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[1]  arXiv:1511.08207 [pdf, other]
Title: Footprints of Loop I on Cosmic Microwave Background Maps
Comments: 8 pages, 5 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Cosmology has made enormous progress through studies of the cosmic microwave background, however the subtle signals being now sought such as B-mode polarisation due to primordial gravitational waves are increasingly hard to disentangle from residual Galactic foregrounds in the derived CMB maps. We revisit our finding that on large angular scales there are traces of the nearby old supernova remnant Loop I in the WMAP 9-year map of the CMB and confirm this with the new SMICA map from the Planck satellite.

[2]  arXiv:1511.08211 [pdf, other]
Title: MultiDarkLens Simulations: weak lensing light-cones and data base presentation
Comments: 15 pages, 21 figures - submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In this paper we present a large database of weak lensing light cones constructed using different snapshots from the Big MultiDark simulation (BigMDPL). The ray-tracing through different multiple planes has been performed with the GLAMER code accounting both for single source redshifts and for sources distributed along the cosmic time. This first paper presents weak lensing forecasts and results according to the geometry of the VIPERS-W1 and VIPERS-W4 field of view. Additional fields will be available on our database and new ones can be run upon request. Our database also contains some tools for lensing analysis. In this paper we present results for convergence power spectra, one point and high order weak lensing statistics useful for forecasts and for cosmological studies. Covariance matrices have also been computed for the different realisations of the W1 and W4 fields. In addition we compute also galaxy-shear and projected density contrasts for different halo masses at two lens redshifts according to the CFHTLS source redshift distribution both using stacking and cross-correlation techniques, finding very good agreement.

[3]  arXiv:1511.08212 [pdf, other]
Title: The Lifecycle of Clusters in Galaxies
Authors: Angela Adamo (SU), Nate Bastian (LJMU)
Comments: 27 pages, 6 figure, review chapter on young star clusters, to appear in The Origin of Stellar Clusters, 2016, ed. S. Stahler (Springer)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We review many of the basic properties of star cluster systems, and focus in particular on how they relate to their host galaxy properties and ambient environment. The cluster mass and luminosity functions are well approximated by power-laws of the form $Ndm \propto M^{\alpha}dm$, with $\alpha\sim-2$ over most of the observable range. However, there is now clear evidence that both become steeper at high masses/luminosities, with the value of the downward turn dependent on environment. The host galaxy properties also appear to affect the cluster formation efficiency ($\Gamma$ - i.e., the fraction of stars that form in bound clusters), with higher star-formation rate density galaxies having higher $\Gamma$ values. Within individual galaxies, there is evidence for $\Gamma$ to vary by a factor of 3-4, likely following the molecular gas surface density, in agreement with recent predictions. Finally, we discuss cluster disruption and its effect on the observed properties of a population, focussing on the age distribution of clusters. We briefly discuss the expectations of theoretical and numerical studies, and also the observed distributions in a number of galaxies. Most observational studies now find agreement with theoretical expectations, namely nearly a constant cluster age distribution for ages up to ~100 Myr (i.e. little disruption), and a drastic steepening above this value caused by a combination of cluster disruption and incompleteness. Rapid cluster disruption for clusters with ages < 100 Myr is ruled out for most galaxies.

[4]  arXiv:1511.08213 [pdf, other]
Title: A review of action estimation methods for galactic dynamics
Comments: 15 pages, 7 figures, submitted to MNRAS, associated software downloadable at this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We review the available methods for estimating actions, angles and frequencies of orbits in both axisymmetric and triaxial potentials. The methods are separated into two classes. Unless an orbit has been trapped by a resonance, convergent, or iterative, methods are able to recover the actions to arbitrarily high accuracy given sufficient computing time. Faster non-convergent methods rely on the potential being sufficiently close to a separable potential and the accuracy of the action estimate cannot be improved through further computation. We critically compare the accuracy of the methods and the required computation time for a range of orbits in an axisymmetric multi-component Galactic potential. We introduce a new method for estimating actions that builds on the adiabatic approximation of Sch\"onich & Binney (2012) and discuss the accuracy required for the actions, angles and frequencies using suitable distribution functions for the thin and thick discs, the stellar halo and a star stream. We conclude that for studies of the disc and smooth halo component of the Milky Way the most suitable compromise between speed and accuracy is the St\"ackel Fudge, whilst when studying streams the non-convergent methods do not offer sufficient accuracy and the most suitable method is computing the actions from an orbit integration via a generating function. All the software used in this study can be downloaded from

[5]  arXiv:1511.08215 [pdf, other]
Title: Constraining AGN triggering mechanisms through the clustering analysis of active black holes
Authors: M. Gatti (1,2), F. Shankar (3), V. Bouillot (4), N. Menci (1), A. Lamastra (1), M. Hirschmann (5), F. Fiore (1) ((1) INAF - Osservatorio Astronomico di Roma,(2) IFAE - Institut de Fisica d'Altes Energies, (3) University of Southampton, (4) University of Cape Town, (5) Institut d' Astrophysique de Paris)
Comments: Accepted for publication on MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The triggering mechanisms for Active Galactic Nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disk instabilities (DI). Using an advanced semi analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modeling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: i) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the center of halos with $M_h>10^{13.5} h^{-1}M_{\odot}$. On the contrary, the IT scenario predicts abundance of active, central galaxies that generally agrees well with observations at every halo mass. ii) The relative number of satellite AGN in DIs at intermediate-to-low luminosities is always significantly higher than in IT models, especially in groups and clusters. The low AGN satellite fraction predicted for the IT scenario might suggest that different feeding modes could simultaneously contribute to the triggering of satellite AGN. iii) Both scenarios are quite degenerate in matching large-scale clustering measurements, suggesting that the sole average bias might not be an effective observational constraint. iv) Our analysis suggests the presence of both a mild luminosity and a more consistent redshift dependence in the AGN clustering, with AGN inhabiting progressively less massive dark matter halos as the redshift increases. We also discuss the impact of different observational selection cuts in measuring AGN clustering, including possible discrepancies between optical and X-ray surveys.

[6]  arXiv:1511.08217 [pdf, other]
Title: Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths
Comments: 24 pages, 17 figures, Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

In the context of observations of the rest-frame ultraviolet and optical emission from distant galaxies, we explore the emission-line properties of photoionization models of active and inactive galaxies. Our aim is to identify new line-ratio diagnostics to discriminate between gas photoionization by active galactic nuclei (AGN) and star formation. We use a standard photoionization code to compute the emission from AGN narrow-line regions and compare this with calculations of the nebular emission from star-forming galaxies achieved using the same code. We confirm the appropriateness of widely used optical spectral diagnostics of nuclear activity versus star formation and explore new diagnostics at ultraviolet wavelengths. We find that combinations of a collisionally excited metal line or line multiplet, such as CIV 1548,1551, OIII]1661,1666, NIII]1750, [SiIII]1883+[SiIII]1892 and [CIII]1907+CIII]1909, with the HeII 1640 recombination line are individually good discriminants of the nature of the ionizing source. Diagrams involving at least 3 of these lines allow an even more stringent distinction between active and inactive galaxies, as well as valuable constraints on interstellar gas parameters and the shape of the ionizing radiation. Several line ratios involving Ne-based emission lines, such as [NeIV]2424, [NeIII]3343 and [NeV]3426, are also good diagnostics of nuclear activity. Our results provide a comprehensive framework to identify the sources of photoionization and physical conditions of the ionized gas from the ultraviolet and optical nebular emission from galaxies. This will be particularly useful to interpret observations of high-redshift galaxies with future facilities, such as the James Webb Space Telescope and extremely large ground-based telescopes.

[7]  arXiv:1511.08219 [pdf, other]
Title: The young nuclear stellar disc in the SB0 galaxy NGC 1023
Authors: E. M. Corsini (1 and 2), L. Morelli (1 and 2), N. Pastorello (3), E. Dalla Bontà (1 and 2), A. Pizzella (1 and 2), E. Portaluri (2) ((1) Dipartimento di Fisica e Astronomia `G. Galilei', Università di Padova, (2) INAF-Osservatorio Astronomico di Padova, (3) Centre for Astrophysics and Supercomputing, Swinburne University of Technology)
Comments: 11 pages, 5 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Small kinematically-decoupled stellar discs with scalelengths of a few tens of parsec are known to reside in the centre of galaxies. Different mechanisms have been proposed to explain how they form, including gas dissipation and merging of globular clusters. Using archival Hubble Space Telescope imaging and ground-based integral-field spectroscopy, we investigated the structure and stellar populations of the nuclear stellar disc hosted in the interacting SB0 galaxy NGC 1023. The stars of the nuclear disc are remarkably younger and more metal rich with respect to the host bulge. These findings support a scenario in which the nuclear disc is the end result of star formation in metal enriched gas piled up in the galaxy centre. The gas can be of either internal or external origin, i.e. from either the main disc of NGC 1023 or the nearby satellite galaxy NGC 1023A. The dissipationless formation of the nuclear disc from already formed stars, through the migration and accretion of star clusters into the galactic centre is rejected.

[8]  arXiv:1511.08226 [pdf, ps, other]
Title: Evidence for Water in the Atmosphere of HAT-P-26b Using LDSS-3C
Comments: 9 pages, 8 figures, submitted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The characterization of a physically-diverse set of transiting exoplanets is an important and necessary step towards establishing the physical properties linked to the production of obscuring clouds or hazes. Only planets with identifiable spectroscopic features can effectively enhance our understanding of atmospheric chemistry and metallicity. Using data acquired by the newly-commissioned LDSS-3C instrument on Magellan and the Spitzer Space Telescope, we find evidence for water in the transmission spectrum of the Neptune-mass planet HAT-P-26b. Surprisingly, we detect no trace of potassium. Our measured spectrum is best explained by either a high-metallicity, cloud-free atmosphere or a solar-metallicity atmosphere with a cloud deck at ~10 mbar. The presence of strong spectral features in our data suggests that future observations at higher precision could break this degeneracy and reveal the planet's atmospheric composition. We also update HAT-P-26b's transit ephemeris, t_0 = 2455304.65218(25) BJD_TDB, and orbital period, p = 4.2345023(7) days.

[9]  arXiv:1511.08227 [pdf, ps, other]
Title: The gas metallicity gradient and the star formation activity of disc galaxies
Authors: Patricia B. Tissera (UNAB, Chile), Susana E. Pedrosa (IAFE, Argentina), Emanuel Sillero (IATE, Argentina), Jose M. Vilchez (IAA, Spain)
Comments: 12 pages, 8 figures, accepted MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study oxygen abundance profiles of the gaseous disc components in simulated galaxies in a hierarchical universe. We analyse the disc metallicity gradients in relation to the stellar masses and star formation rates of the simulated galaxies. We find a trend for galaxies with low stellar masses to have steeper metallicity gradients than galaxies with high stellar masses at z ~0. We also detect that the gas-phase metallicity slopes and the specific star formation rate (sSFR) of our simulated disc galaxies are consistent with recently reported observations at z ~0. Simulated galaxies with high stellar masses reproduce the observed relationship at all analysed redshifts and have an increasing contribution of discs with positive metallicity slopes with increasing redshift. Simulated galaxies with low stellar masses a have larger fraction of negative metallicity gradients with increasing redshift. Simulated galaxies with positive or very negative metallicity slopes exhibit disturbed morphologies and/or have a close neighbour. We analyse the evolution of the slope of the oxygen profile and sSFR for a gas-rich galaxy-galaxy encounter, finding that this kind of events could generate either positive and negative gas-phase oxygen profiles depending on their state of evolution. Our results support claims that the determination of reliable metallicity gradients as a function of redshift is a key piece of information to understand galaxy formation and set constrains on the subgrid physics.

[10]  arXiv:1511.08243 [pdf, other]
Title: Young, Star-forming Galaxies and their local Counterparts: the Evolving Relationship of Mass-SFR-Metallicity since z ~ 2.1
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We explore the evolution of the Stellar Mass-Star Formation Rate-Metallicity Relation using a set of 256 COSMOS and GOODS galaxies in the redshift range 1.90 < z < 2.35. We present the galaxies' rest-frame optical emission-line fluxes derived from IR-grism spectroscopy with the Hubble Space Telescope and combine these data with star formation rates and stellar masses obtained from deep, multi-wavelength (rest-frame UV to IR) photometry. We then compare these measurements to those for a local sample of galaxies carefully matched in stellar mass (7.5 < log(M*/Msol) < 10.5) and star formation rate (-0.5 < log(SFR) < 2.5 in Msol yr^-1). We find that the distribution of z ~ 2.1 galaxies in stellar mass-SFR-metallicity space is clearly different from that derived for our sample of similarly bright (L_H\b{eta} > 3 . 10^40 ergs s^-1) local galaxies, and this offset cannot be explained by simple systematic offsets in the derived quantities. At stellar masses above ~10^9 Msol and star formation rates above ~10 Msol yr^-1, the z ~ 2.1 galaxies have higher oxygen abundances than their local counterparts, while the opposite is true for lower-mass, lower-SFR systems.

[11]  arXiv:1511.08252 [pdf, ps, other]
Title: Suppression of Star Formation in the Hosts of Low-Excitation Radio Galaxies
Comments: 15 pages, 9 figures, resubmitted to ApJ after referee's comments
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The feedback from radio-loud active galactic nuclei (R-AGN) may help maintain low star formation (SF) rates in their early-type hosts, but the observational evidence for this mechanism has been inconclusive. We study systematic differences of aggregate spectral energy distributions (SEDs) of various subsets of $\sim$4000 low-redshift R-AGN from Best & Heckman (2012) with respect to (currently) inactive control samples selected to have matching redshift, stellar mass, population age, axis ratio, and environment. Aggregate SEDs, ranging from the ultraviolet (UV) through mid-infrared (mid-IR, 22 $\mu$m), were constructed using a Bayesian method that eliminates biases from non-detections in GALEX and WISE. We study rare high-excitation sources separately from low-excitation ones, which we split by environment and host properties. We find that both the UV and mid-IR emission of non-cluster R-AGNs (80% of sample) are suppressed by $\sim$0.2 dex relative to that of the control group, especially for moderately massive galaxies (log $M_* \lesssim$ 11). The difference disappears for high-mass R-AGN and for R-AGN in clusters, where other, non-AGN quenching/maintenance mechanisms may dominate, or where the suppression of SF due to AGN may persist between active phases of the central engine, perhaps because of the presence of a hot gaseous halo storing AGN energy. High-excitation (high accretion rate) sources, which make up 2% of the R-AGN sample, also show no evidence of SF suppression (their UV is the same as in controls), but they exhibit a strong mid-IR excess due to AGN dust heating.

[12]  arXiv:1511.08255 [pdf, other]
Title: nIFTY galaxy cluster simulations III: The Similarity & Diversity of Galaxies & Subhaloes
Comments: 17 pages (+4 page appendix), 16 figures, 2 tables; submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We examine subhaloes and galaxies residing in a simulated LCDM galaxy cluster ($M^{\rm crit}_{200}=1.1\times10^{15}M_\odot/h$) produced by hydrodynamical codes ranging from classic Smooth Particle Hydrodynamics (SPH), newer SPH codes, an adaptive mesh code and a moving mesh scheme. These codes use subgrid models to capture galaxy formation physics. We compare how well these codes reproduce the same subhaloes/galaxies in gravity only, non-radiative hydrodynamics and full radiative physics runs by looking at the overall subhalo/galaxy distribution and on an individual objects basis. We find the subhalo population is reproduced to within $\lesssim10\%$ for both dark matter only and non-radiative runs, with individual objects showing code-to-code scatter of $\lesssim0.1$ dex, although the gas in non-radiative simulations shows significant scatter. Including radiative physics significantly increases the diversity seen. The subhalo mass and $V_{max}$ distributions vary by $\approx20\%$, a result of feedback moving significant baryonic mass around. Galaxies also show striking code-to-code variations. Although the Tully-Fisher relation is similar in almost all codes, the number of galaxies with $10^{9}M_\odot/h\lesssim M_*\lesssim 10^{12}M_\odot/h$ can differ by a factor of 4. Individual galaxies show code-to-code scatter of $\sim0.5$ dex in stellar mass. Moreover, strong systematic differences exist, with some codes producing galaxies $70\%$ smaller than others. The diversity partially arises from the inclusion/absence of AGN feedback. Our results combined with our companion papers, Sembolini et al. (2015a,b), demonstrate that subgrid physics is not just subject to fine-tuning, but the complexity of building galaxies in all environments remains a challenge. We argue that even basic galaxy properties, such as the stellar mass to halo mass, should be treated with errors bars of $\sim0.2-0.5$ dex.

[13]  arXiv:1511.08278 [pdf, ps, other]
Title: Discovery of two broad absorption line quasars at redshift about 4.75 using the Lijiang 2.4m telescope
Comments: 6 pages, 3 figures
Journal-ref: Science China Physics, Mechanics & Astronomy, September 2015 Vol.58 No.9:599501
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The ultraviolet broad absorption lines have been seen in the spectra of quasars at high redshift, and are generally considered to be caused by outflows with velocities from thousands kilometers per second to one tenth of the speed of light. They provide crucial implications for the cosmological structures and physical evolutions related to the feedback of active galactic nuclei (AGNs). Recently, through a dedicated program of optically spectroscopic identifications of selected quasar candidates at redshift 5 by using the Lijiang 2.4 m telescope, we discovered two luminous broad absorption line quasars (BALQSOs) at redshift about 4.75. One of them may even have the potentially highest absorption Balnicity Index (BI) ever found to date, which is remarkably characterized by its deep, broad absorption lines and sub-relativistic outflows. Further physical properties, including the metal abundances, variabilities, evolutions of the supermassive black holes (SMBH) and accretion disks associated with the feedback process, can be investigated with multi-wavelength follow-up observations in the future.

[14]  arXiv:1511.08279 [pdf, ps, other]
Title: Probing the gravitational Faraday rotation using quasar X-ray microlensing
Authors: Bin Chen
Comments: 15 pages, 3 figures
Journal-ref: Scientific Reports, 5, 16860, 2015
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission.

[15]  arXiv:1511.08289 [pdf, other]
Title: NGC 147, NGC 185 and CassII: a genetic approach to orbital properties, star formation and tidal debris
Comments: Accepted for publication on MNRAS. 12 pages, 9 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

NGC147, NGC185 and CassiopeiaII (CassII) have similar positions in the sky, distances and measured line of sight velocities. This proximity in phase space suggests that these three satellites of M31 form a subgroup within the Local Group. Nevertheless, the differences in their star formation history and interstellar medium, and the recent discovery of a stellar stream in NGC~147, combined with the lack of tidal features in the other two satellites, are all indications of complex and diverse interactions between M31 and these three satellites. We use a genetic algorithm to explore the different orbits that these satellites can have and select six sets of orbits that could best explain the observational features of the NGC147, NGC185 and CassII satellites. The parameters of these orbits are then used as a starting point for N-body simulations. We present models for which NGC147, NGC185 and CassII are a bound group for a total time of at least one Gyr but still undergo different interactions with M31 and as a result NGC147 has a clear stellar stream whereas the other two satellites have no significant tidal features. This result shows that it is possible to find solutions that reproduce the contrasting properties of the satellites and for which NGC147-NGC185-CassII have been gravitationally bound.

[16]  arXiv:1511.08293 [pdf, other]
Title: Asteroid Evolution: Role of Geotechnical Properties
Authors: Paul Sánchez
Comments: Invited review paper presented at the XXIX IAU General Assembly, August, 2015
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

This paper presents a brief review and latest results of the work that has been carried out by the Planetary Science community in order to understand that role of the geotechnical properties of granular asteroids (commonly known as "rubble-pile" asteroids) in their formation, evolution and possible disruption. As such, we will touch in aspects of the theoretical and numerical tools that have been used with this objective and how the obtained results compare to the observed asteroids.

[17]  arXiv:1511.08296 [pdf, ps, other]
Title: Flickering of accreting white dwarfs: the remarkable amplitude - flux relation and disc viscocity
Comments: 5 pages, ver...16.October.2015
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We analyze optical photometric data of short term variability (flickering) of accreting white dwarfs in cataclysmic variables (KR Aur, MV Lyr, V794 Aql, TT Ari, V425 Cas), recurrent novae (RS Oph and T CrB) and jet-ejecting symbiotic stars (CH Cyg and MWC 560). We find that the amplitude-flux relationship is visible over four orders of magnitude, in the range of fluxes from $10^{29}$ to $10^{33}$ erg s$^{-1}$ \AA$^{-1}$, as a "statistically perfect" correlation with correlation coefficient 0.96 and p-value $ \sim 10^{-28}$. In the above range, the amplitude of variability for any of our 9 objects is proportional to the flux level with (almost) one and the same factor of proportionality for all 9 accreting white dwarfs with $\Delta F = 0.36 (\pm 0.05) F_{av}$, $\sigma_{rms} = 0.086(\pm 0.011) F_{av}$, and $\sigma_{rms} / \Delta F = 0.24 \pm 0.02$. Over all, our results indicate that the viscosity in the accretion discs is practically the same for all 9 objects in our sample, in the mass accretion rate range $2 \times 10^{-11} - 2\times10^{-7}$ $M_\odot$ yr$^{-1}$.

[18]  arXiv:1511.08298 [pdf, ps, other]
Title: Multi-frequency Radio Profiles of PSR B1133+16: radiation location and particle energy
Comments: 13 pages, 18 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The pulse profile of PSR B1133+16 is usually regarded as a conal-double structure. However, its multifrequency profiles cannot simply be fitted with two Gaussian functions, and a third component is always needed to fit the bridge region (between two peaks). This would introduce additional, redundant parameters. In this paper, through a comparison of five fitting functions (Gaussian, von Mises, hyperbolic secant, square hyperbolic secant, and Lorentz), it is found that the square hyperbolic secant function can best reproduce the profile, yielding an improved fit. Moreover, a symmetric 2D radiation beam function, instead of a simple 1D Gaussian function, is used to fit the profile. Each profile with either well-resolved or not-so-well-resolved peaks could be fitted adequately using this beam function, and the bridge emission between the two peaks does not need to be a new component. Adopting inclination and impact angles based on polarization measurements, the opening angle ({\theta}_{\mu}0) of the radiation beam in a certain frequency band is derived from beam-function fitting. The corresponding radiation altitudes are then calculated. Based on multi-frequency profiles, we also computed the Lorentz factors of the particles and their dispersion at those locations in both the curvature-radiation (CR) and inverse-Compton-scattering (ICS) models. We found that the Lorentz factors of the particles decrease rapidly as the radiation altitude increases. Besides, the radiation prefers to be generated in annular region rather than core region, and this needs further validation.

[19]  arXiv:1511.08311 [pdf, ps, other]
Title: The Megamaser Cosmology Project VIII. A Geometric Distance to NGC 5765b
Comments: 49 pages, 11 figures, 9 tables; Accepted by ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

As part of the Megamaser Cosmology Project (MCP), here we present a new geometric distance measurement to the megamaser galaxy NGC 5765b. Through a series of VLBI observations, we have confirmed the water masers trace a thin, sub-parsec Keplerian disk around the nucleus, implying an enclosed mass of 4.55 $\pm$ 0.40 $\times~10^{7}M_\odot$. Meanwhile, from single dish monitoring of the maser spectra over two years, we measured the secular drifts of maser features near the systemic velocity of the galaxy with rates between 0.5 and 1.2 km s$^{-1}$ yr$^{-1}$. Fitting a warped, thin disk model to these measurements, we determine a Hubble Constant $H_{0}$ of 66.0 $\pm$ 6.0 km s$^{-1}$ Mpc$^{-1}$ with the angular-diameter distance to NGC 5765b of 126.3 $\pm$ 11.6 Mpc.
Apart from the distance measurement, we also investigate some physical properties related to the maser disk in NGC 5765b. The high-velocity features are spatially distributed into several clumps, which may indicate the existence of a spiral density wave associated with the accretion disk. For the red-shifted features, the envelope defined by the peak maser intensities increases with radius. The profile of the systemic masers in NGC 5765b is smooth and shows almost no structural changes over the two years of monitoring time, which differs from the more variable case of NGC 4258.

[20]  arXiv:1511.08325 [pdf, ps, other]
Title: SMA observations of the W3(OH) complex: Dynamical differentiation between W3(H$_2$O) and W3(OH)
Comments: accepted by MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We present Submillimeter Array (SMA) observations of the HCN\,(3--2) and HCO$^+$\,(3--2) molecular lines toward the W3(H$_2$O) and W3(OH) star-forming complexes. Infall and outflow motions in the W3(H$_2$O) have been characterized by observing HCN and HCO$^+$ transitions. High-velocity blue/red-shifted emission, tracing the outflow, show multiple knots, which might originate in episodic and precessing outflows. `Blue-peaked' line profiles indicate that gas is infalling onto the W3(H$_2$O) dust core. The measured large mass accretion rate, 2.3$\times$10$^{-3}$~M$_{\odot}$~yr$^{-1}$, together with the small free-fall time scale, 5$\times$10$^{3}$~yr, suggest W3(H$_2$O) is in an early evolutionary stage of the process of formation of high-mass stars. For the W3(OH), a two-layer model fit to the HCN and HCO$^+$ spectral lines and Spizter/IRAC images support that the W3(OH) H{\sc ii} region is expanding and interacting with the ambient gas, with the shocked neutral gas being expanding with an expansion timescale of 6.4$\times$10$^{3}$~yr. The observations suggest different kinematical timescales and dynamical states for the W3(H$_2$O) and W3(OH).

[21]  arXiv:1511.08330 [pdf, other]
Title: Discovery of a suspected giant radio galaxy with the KAT-7 array
Comments: 7 pages, 6 figures, 2 tables, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We detect a new suspected giant radio galaxy (GRG) discovered by KAT-7. The GRG core is identified with the WISE source J013313.50-130330.5, an extragalactic source based on its infrared colors and consistent with a misaligned AGN-type spectrum at $z\approx 0.3$. The multi-$\nu$ spectral energy distribution (SED) of the object associated to the GRG core shows a synchrotron peak at $\nu \approx 10^{14}$ Hz consistent with the SED of a radio galaxy blazar-like core. The angular size of the lobes are $\sim 4 ^{\prime}$ for the NW lobe and $\sim 1.2 ^{\prime}$ for the SE lobe, corresponding to projected linear distances of $\sim 1078$ kpc and $\sim 324$ kpc, respectively. The best-fit parameters for the SED of the GRG core and the value of jet boosting parameter $\delta =2$, indicate that the GRG jet has maximum inclination $\theta \approx 30$ deg with respect to the line of sight, a value obtained for $\delta=\Gamma$, while the minimum value of $\theta$ is not constrained due to the degeneracy existing with the value of Lorentz factor $\Gamma$. Given the photometric redshift $z \approx 0.3$, this GRG shows a core luminosity of $P_{1.4 GHz} \approx 5.52 \times 10^{24}$ W Hz$^{-1}$, and a luminosity $P_{1.4 GHz} \approx 1.29 \times 10^{25}$ W Hz$^{-1}$ for the NW lobe and $P_{1.4 GHz} \approx 0.46 \times 10^{25}$ W Hz$^{-1}$ for the SE lobe, consistent with the typical GRG luminosities. The radio lobes show a fractional linear polarization $\approx 9 \%$ consistent with typical values found in other GRG lobes.

[22]  arXiv:1511.08339 [pdf, other]
Title: Dreaming of atmospheres
Authors: I. P. Waldmann
Comments: ApJ submitted
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Here we introduce the RobERt (Robotic Exoplanet Recognition) algorithm for the classification of exoplanetary emission spectra. Spectral retrievals of exoplanetary atmospheres frequently requires the preselection of molecular/atomic opacities to be defined by the user. In the era of open-source, automated and self-sufficient retrieval algorithms, manual input should be avoided. User dependent input could, in worst case scenarios, lead to incomplete models and biases in the retrieval. The RobERt algorithm is based on deep belief neural (DBN) networks trained to accurately recognise molecular signatures for a wide range of planets, atmospheric thermal profiles and compositions. Reconstructions of the learned features, also referred to as `dreams' of the network, indicate good convergence and an accurate representation of molecular features in the DBN. Using these deep neural networks, we work towards retrieval algorithms that themselves understand the nature of the observed spectra, are able to learn from current and past data and make sensible qualitative preselections of atmospheric opacities to be used for the quantitative stage of the retrieval process.

[23]  arXiv:1511.08356 [pdf, other]
Title: The far-infrared behaviour of Herbig Ae/Be discs: Herschel PACS photometry
Comments: 18 pages, 12 figures main text, 32 figure in Appendix
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Herbig Ae/Be objects are pre-main sequence stars surrounded by gas- and dust-rich circumstellar discs. These objects are in the throes of star and planet formation, and their characterisation informs us of the processes and outcomes of planet formation processes around intermediate mass stars. Here we analyse the spectral energy distributions of disc host stars observed by the Herschel Open Time Key Programme `Gas in Protoplanetary Systems'. We present Herschel/PACS far-infrared imaging observations of 22 Herbig Ae/Bes and 5 debris discs, combined with ancillary photometry spanning ultraviolet to sub-millimetre wavelengths. From these measurements we determine the diagnostics of disc evolution, along with the total excess, in three regimes spanning near-, mid-, and far-infrared wavelengths. Using appropriate statistical tests, these diagnostics are examined for correlations. We find that the far-infrared flux, where the disc becomes optically thin, is correlated with the millimetre flux, which provides a measure of the total dust mass. The ratio of far-infrared to sub-millimetre flux is found to be greater for targets with discs that are brighter at millimetre wavelengths and that have steeper sub-millimetre slopes. Furthermore, discs with flared geometry have, on average, larger excesses than flat geometry discs. Finally, we estimate the extents of these discs (or provide upper limits) from the observations.

[24]  arXiv:1511.08360 [pdf, ps, other]
Title: From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2
Comments: 11 pages, 6 figures, 1 table, accepted for publication in Astrophysics and Space Science
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Earth co-orbitals of the horseshoe type are interesting objects to study for practical reasons. They are relatively easy to access from our planet and that makes them attractive targets for sample return missions. Here, we show that near-Earth asteroid (NEA) 2015 SO2 is a transient co-orbital to the Earth that experiences a rather peculiar orbital evolution characterised by recurrent, alternating horseshoe and quasi-satellite episodes. It is currently following a horseshoe trajectory, the ninth asteroid known to do so. Besides moving inside the 1:1 mean motion resonance with the Earth, it is subjected to a Kozai resonance with the value of the argument of perihelion librating around 270 degrees. Contrary to other NEAs, asteroid 2015 SO2 may have remained in the vicinity of Earth's co-orbital region for a few hundreds of thousands of years.

[25]  arXiv:1511.08365 [pdf, ps, other]
Title: Asteroseismic inversions for radial differential rotation of Sun-like stars: Sensitivity to uncertainties
Comments: accepted in A&A, 9 pages, 10 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We quantify the effect of observational spectroscopic and asteroseismic uncertainties on regularised least squares (RLS) inversions for the radial differential rotation of Sun-like and subgiant stars. We first solved the forward problem to model rotational splittings plus the observed uncertainties for models of a Sun-like star, HD 52265, and a subgiant star, KIC 7341231. We randomly perturbed the parameters of the stellar models within the uncertainties of the spectroscopic and asteroseismic constraints and used these perturbed stellar models to compute rotational splittings. We experimented with three rotation profiles: solid body rotation, a step function, and a smooth rotation profile decreasing with radius. We then solved the inverse problem to infer the radial differential rotation profile using a RLS inversion and kernels from the best-fit stellar model.We found that the inversions for Sun-like stars with solar-like radial differential rotation profiles are insensitive to the uncertainties in the stellar models. We found that when the rotation rate below the convection zone is increased to six times that of the surface rotation rate the inferred rotation profile excluded solid body rotation. With the current observational uncertainties, we found that inversions of subgiant stars are sensitive to the uncertainties in the stellar model. Our findings suggest that inversions for the radial differential rotation of subgiant stars would benefit from more tightly constrained stellar models. In Sun-like stars, the insensitivity of the inversions to stellar model uncertainties suggests that it may be possible to perform ensemble inversions for the average radial differential rotation of many stars with a range of stellar types to better constrain the inversions.

[26]  arXiv:1511.08397 [pdf, other]
Title: The SOPHIE search for northern extrasolar planets VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions
Comments: 17 pages, 9 figures, accepted in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-year radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 Jupiter mass orbiting solar-type stars with periods longer than ten years. An upper mass limit of these companions is provided using astrometric Hipparcos data, high-angular resolution imaging made with PUEO, and a deep analysis of the cross-correlation function of the main stellar spectra to search for blend effects or faint secondary components. These objects double the number of known brown dwarf companions with orbital periods longer than ten years and reinforce the conclusion that the occurrence of such objects increases with orbital separation. With a projected separation larger than 100 mas, all these brown dwarf candidates are appropriate targets for high-contrast and high angular resolution imaging.

[27]  arXiv:1511.08402 [pdf, other]
Title: UBVRIz Light Curves of 51 Type II Supernovae
Comments: 110 pages, 9 Figures, 6 Tables, accepted in AJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present a compilation of UBV RIz light curves of 51 type II supernovae discovered during the course of four different surveys during 1986 to 2003: the Cerro Tololo Supernova Survey, the Calan/Tololo Supernova Program (C&T), the Supernova Optical and Infrared Survey (SOIRS), and the Carnegie Type II Supernova Survey (CATS). The photometry is based on template-subtracted images to eliminate any potential host galaxy light contamination, and calibrated from foreground stars. This work presents these photometric data, studies the color evolution using different bands, and explores the relation between the magnitude at maximum brightness and the brightness decline parameter (s) from maximum light through the end of the recombination phase. This parameter is found to be shallower for redder bands and appears to have the best correlation in the B band. In addition, it also correlates with the plateau duration, being thus shorter (longer) for larger (smaller) s values.

[28]  arXiv:1511.08422 [pdf, other]
Title: The daily processing of asteroid observations by Gaia
Comments: 25 pages, 5 figures, accepted in Planetary and Space Science, 2015
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Gaia mission started its regular observing program in the summer of 2014, and since then it is regularly obtaining observations of asteroids. This paper draws the outline of the data processing for Solar System objects, and in particular on the daily "short-term" processing, from the on-board data acquisition to the ground-based processing. We illustrate the tools developed to compute predictions of asteroid observations, we discuss the procedures implemented by the daily processing, and we illustrate some tests and validations of the processing of the asteroid observations. Our findings are overall consistent with the expectations concerning the performances of Gaia and the effectiveness of the developed software for data reduction.

[29]  arXiv:1511.08424 [pdf, other]
Title: Temperature dependence of alpha-induced scintillation in the 1,1,4,4-tetraphenyl-1,3-butadiene wavelength shifter
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)

Liquid noble gas based particle detectors often use the organic wavelength shifter 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) which shifts UV scintillation light to the visible regime, facilitating its detection, but which also can scintillate on its own. Dark matter searches based on this type of detector commonly rely on pulse-shape discrimination (PSD) for background mitigation. Alpha-induced scintillation therefore represents a possible background source in dark matter searches. The timing characteristics of this scintillation determine whether this background can be mitigated through PSD. We have therefore characterized the pulse shape and light yield of alpha induced TPB scintillation at temperatures ranging from 300 K down to 4 K, with special attention given to liquid noble temperatures. We find that the pulse shapes and light yield depend strongly on temperature. In addition, the significant contribution of long time constants above ~50 K provides an avenue for discrimination between alpha decay events in TPB and nuclear-recoil events in noble liquid detectors.

[30]  arXiv:1511.08425 [pdf, ps, other]
Title: The MiMeS Survey of Magnetism in Massive Stars: Introduction and overview
Comments: Accepted by MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The MiMeS project is a large-scale, high resolution, sensitive spectropolarimetric investigation of the magnetic properties of O and early B type stars. Initiated in 2008 and completed in 2013, the project was supported by 3 Large Program allocations, as well as various programs initiated by independent PIs and archival resources. Ultimately, over 4800 circularly polarized spectra of 560 O and B stars were collected with the instruments ESPaDOnS at the Canada-France-Hawaii Telescope, Narval at the T\'elescope Bernard Lyot, and HARPSpol at the European Southern Observatory La Silla 3.6m telescope, making MiMeS by far the largest systematic investigation of massive star magnetism ever undertaken. In this paper, the first in a series reporting the general results of the survey, we introduce the scientific motivation and goals, describe the sample of targets, review the instrumentation and observational techniques used, explain the exposure time calculation designed to provide sensitivity to surface dipole fields above approximately 100 G, discuss the polarimetric performance, stability and uncertainty of the instrumentation, and summarize the previous and forthcoming publications.

[31]  arXiv:1511.08438 [pdf, ps, other]
Title: Analysis of the Z Distribution of Young Objects in the Galactic Thin Disk
Comments: 13 pages, 2 figures, 2 tables
Journal-ref: Astronomy Letters, 2016, Vol. 42, No. 1, pp. 1-9
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We have obtained new estimates of the Sun's distance from the symmetry plane Zo and the vertical disk scale height h using currently available data on stellar OB associations, Wolf-Rayet stars, HII regions, and Cepheids. Based on individual determinations, we have calculated the mean Zo=-16+/-2 pc. Based on the model of a self-gravitating isothermal disk for the density distribution, we have found the following vertical disk scale heights: h = 40.2+/-2.1 pc from OB associations, h = 47.8+/-3.9 pc from Wolf-Rayet stars, h=48.4+/-2.5 pc from HII regions, and h = 66.2+/-1.6 pc from Cepheids. We have estimated the surface, \sum=6 kpc^{-2}, and volume, D(Zo) = 50.6 kpc^{-3}, densities from a sample of OB associations. We have found that there could be approximately 5000 OB associations in the Galaxy.

[32]  arXiv:1511.08457 [pdf, ps, other]
Title: New CCD Photometry Study of RV UMa
Authors: D.Tasselli
Comments: Total Page: 18 Total Table: 10 Total Figure: 20. arXiv admin note: substantial text overlap with arXiv:1510.02837; text overlap with arXiv:astro-ph/0410119 by other authors
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

All available CCD observation of RV UMa have been analyzed to obtain an accurate mathematical description of the ligh variation. We discuss in this paper a new study of variable star RV UMa, a short period RRab star, in orther to determine through the light curve and the physical parameters, the presence of "Blazhko effect". The Star were observed for a total of 839 sessions shooting, and exhibits light curve modulation with the shortest modulation Period=0.468002 ever observed. The result detect small but definite modification in temperature and mean radius of the star itself. All results are compared with previously published literature values and discussed.

[33]  arXiv:1511.08470 [pdf, other]
Title: Primordial Black Holes Formation from Particle Production during Inflation
Authors: Encieh Erfani
Comments: 17 pages, 4 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We study the possibility that particle production during inflation can source the required power spectrum for dark matter (DM) primordial black holes (PBH) formation. We consider the scalar and the gauge quanta production in inflation models, where in the latter case, we focus in two sectors: inflaton coupled i) directly and ii) gravitationally to a $U(1)$ gauge field. We do not assume any specific potential for the inflaton field. Hence, in the gauge production case, in a model independent way we show that the non-production of DM PBHs puts stronger upper bound on the particle production parameter. Our analysis show that this bound is more stringent than the bounds from the bispectrum and the tensor-to-scalar ratio derived by gauge production in these models. In the scenario where the inflaton field coupled to a scalar field, we put an upper bound on the amplitude of the generated scalar power spectrum by non-production of PBHs. As a by-product we also show that the required scalar power spectrum for PBHs formation is lower when the density perturbations are non-Gaussian in comparison to the Gaussian density perturbations.

[34]  arXiv:1511.08480 [pdf, other]
Title: Chemodynamical modelling of the Milky Way
Comments: 6 pages to appear in "Reconstructing the Milky Way history: spectroscopic surveys, asteroseismology and chemodynamical models", eds C Chiappini, J Montalban & M Steffen
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Chemodynamical models of our Galaxy that have analytic Extended Distribution Functions (EDFs) are likely to play a key role in extracting science from surveys in the era of Gaia.

[35]  arXiv:1511.08481 [pdf, other]
Title: Merger Signatures in the Dynamics of Star-forming Gas
Authors: Chao-Ling Hung (1,2,3), Christopher C. Hayward (4,2), Howard A. Smith (2), Matthew L. N. Ashby (2), Lauranne Lanz (5), Juan R. Martínez-Galarza (2), D. B. Sanders (1), Andreas Zezas (6,2) ((1) IfA Hawaii, (2) CfA, (3) UT Austin, (4) Caltech, (5) IPAC, (6) Crete)
Comments: 13 pages, 8 figures, ApJ accepted
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Spatially resolved kinematics have been used to determine the dynamical status of star-forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-forming gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-forming gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, gas fractions, and mass ratios, we find that the merger signatures are visible for ~0.2-0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive gas-rich disk galaxies designed to be analogs of z~2-3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20-60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-forming gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-forming galaxies, and including them in samples of star-forming disks may bias the measurements of disk properties such as intrinsic velocity dispersion.

[36]  arXiv:1511.08493 [pdf, ps, other]
Title: Globular Cluster Systems in Brightest Cluster Galaxies. II: NGC 6166
Comments: 19 pages, 22 figures. In press for Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present new deep photometry of the globular cluster system (GCS) around NGC 6166, the central supergiant galaxy in Abell 2199. HST data from the ACS and WFC3 cameras in F475W, F814W are used to determine the spatial distribution of the GCS, its metallicity distribution function (MDF), and the dependence of the MDF on galactocentric radius and on GC luminosity. The MDF is extremely broad, with the classic red and blue subpopulations heavily overlapped, but a double-Gaussian model can still formally match the MDF closely. The spatial distribution follows a Sersic-like profile detectably to a projected radius of at least $R_{gc} = 250$ kpc. To that radius, the total number of clusters in the system is N_{GC} = 39000 +- 2000, the global specific frequency is S_N = 11.2 +- 0.6, and 57\% of the total are blue, metal-poor clusters. The GCS may fade smoothly into the Intra-Cluster Medium of A2199; we see no clear transition from the core of the galaxy to the cD halo or the ICM. The radial distribution, projected ellipticity, and mean metallicity of the red (metal-richer) clusters match the halo light extremely well for R > 15 kpc, both of them varying as \sigma_{MRGC} ~ \sigma_{light} ~ R^-1.8. By comparison, the blue (metal-poor) GC component has a much shallower falloff \sigma_{MPGC} ~ R^-1.0 and a more nearly spherical distribution. This strong difference in their density distributions produces a net metallicity gradient in the GCS as a whole that is primarily generated by the population gradient. With NGC 6166 we appear to be penetrating into a regime of high enough galaxy mass and rich enough environment that the bimodal two-phase description of GC formation is no longer as clear or effective as it has been in smaller galaxies.

[37]  arXiv:1511.08502 [pdf, ps, other]
Title: How Big Can a Black Hole Grow?
Authors: Andrew King
Comments: to appear in MNRAS Letters; 4 pages, 1 figure
Subjects: Astrophysics of Galaxies (astro-ph.GA)

I show that there is a physical limit to the mass of a black hole, above which it cannot grow through luminous accretion of gas, and so cannot appear as a quasar or active galactic nucleus. The limit is Mmax \simeq 5x10^{10}M_sun for typical parameters, but can reach Mmax \simeq 2.7x10^{11}M_sun in extreme cases (e.g. maximal prograde spin). The largest black hole masses so far found are close to but below the limit. The Eddington luminosity \simeq 6.5x10^{48} erg/s corresponding to Mmax is remarkably close to the largest AGN bolometric luminosity so far observed. The mass and luminosity limits both rely on a reasonable but currently untestable hypothesis about AGN disc formation, so future observations of extreme SMBH masses can therefore probe fundamental disc physics. Black holes can in principle grow their masses above Mmax by non-luminous means such as mergers with other holes, but cannot become luminous accretors again. They might nevertheless be detectable in other ways, for example through gravitational lensing. I show further that black holes with masses ~ Mmax can probably grow above the values specified by the black-hole -- host-galaxy scaling relations, in agreement with observation.

[38]  arXiv:1511.08503 [pdf, other]
Title: Herschel-Planck dust optical depth and column density maps - II. Perseus
Comments: 15 pages, 19 figures. Accepted for publication in Astronomy & Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present optical depth and temperature maps of the Perseus molecular cloud, obtained combining dust emission data from the Herschel and Planck satellites and 2MASS/NIR dust extinction maps. The maps have a resolution of 36 arcsec in the Herschel regions, and of 5 arcmin elsewhere. The dynamic range of the optical depth map ranges from $1\times10^{-2}\, \mathrm{mag}$ up to $20 \,\mathrm{mag}$ in the equivalent K band extinction. We also evaluate the ratio between the $2.2 \,\mathrm{\mu m}$ extinction coefficient and the $850 \,\mathrm{\mu m}$ opacity. The value we obtain is close to the one found in the Orion B molecular cloud. We show that the cumulative and the differential area function of the data (which is proportional to the probability distribution function of the cloud column density) follow power laws with index respectively $\simeq -2$, and $\simeq -3$. We use WISE data to improve current YSO catalogues based mostly on \emph{Spitzer} data and we build an up-to-date selection of Class~I/0 objects. Using this selection, we evaluate the local Schmidt law, $\Sigma_{\mathrm{YSO}} \propto \Sigma_{\mathrm{gas}}^{\beta}$, showing that $\beta=2.4 \pm 0.6$. Finally, we show that the area-extinction relation is important for determining the star formation rate in the cloud, which is in agreement with other recent works.

[39]  arXiv:1511.08504 [pdf, ps, other]
Title: Using the Inferred Halpha Emission from z~4-5 Galaxies to Measure the Lyman-Continuum Photon Production Efficiency xi_{ion}: Implications for the Escape Fraction
Comments: 12 pages, 6 figures, 3 tables, submitted to the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Galaxies represent one of the preferred candidate sources to drive the reionization of the universe. Even as gains are made in mapping the galaxy UV luminosity density to z>6, significant uncertainties remain regarding the Lyman-continuum (LyC) photon production efficiency xi_{ion} and the escape fraction f_{esc}. However, dramatic progress can be made in assessing the impact of z>~6 galaxies on the reionization of the universe, using the Halpha fluxes inferred from z=4-5 galaxies based on their IRAC broad-band fluxes. Here, we provide the first-ever direct estimates of the LyC photon production efficiency xi_{ion} for z>~4 galaxies, by comparing the LyC photons implied by the inferred H$\alpha$ luminosities for a $z=4$-5 sample with the dust-corrected UV-continuum luminosities. We find log_{10} xi_{ion}/[Hz / ergs] to have a mean value of 25.28_{-0.09}^{+0.10} and 25.34_{-0.08}^{+0.09} for sub-L* z=4-5 galaxies adopting Calzetti and SMC dust laws, respectively. Reassuringly, both derived values are consistent with standardly assumed xi_{ion}'s in reionization models, with a slight preference for higher xi_{ion}'s (by ~0.1 dex) adopting the SMC dust law. A modest ~0.03-dex increase in these estimates would result if the escape fraction for ionizing photons is non-zero and galaxies dominate the ionizing emissivity at z~4.4. High values of xi_{ion} (~25.5-25.9 dex) are derived for the bluest galaxies (beta<-2.3) in our samples, independent of dust law and consistent with results for a z=7.045 galaxy. Such elevated values of xi_{ion} would have important consequences, indicating that f_{esc} cannot be in excess of 13% unless the galaxy UV luminosity function does not extend down to -13 mag or the clumping factor is greater than 3. A low escape fraction would fit well with the low rate of Lyman-continuum leakage observed at z~3.

[40]  arXiv:1511.08508 [pdf, ps, other]
Title: The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
Comments: 10 pages, 9 figures, Submitted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We validate a candidate super-Earth ($R_p=2.38\pm 0.25R_\oplus$) on a close-in orbit ($P=2.26$ days) around EPIC 206318379, a metal-rich M4-type dwarf in the Campaign 3 field of the K2 mission. Our follow-up observations included multi-band transit observations from the optical to the near infrared, low-resolution spectroscopy, and high-resolution adaptive-optics (AO) imaging. The phase-folded K2 transit light curve has a V-shape because the transit duration around this small star is comparable to the 30-minute K2 cadence. However, the light curves from our follow-up observations exhibit a sharp ingress and/or egress and flat bottom, ruling out a grazing eclipse of a binary system. We perform a global fit to all ground-based observations using a Gaussian process-based method and show that the transit depths in all passbands ($r'_2, z_\mathrm{s,2}, J, H, K_\mathrm{s}$) are within $2.2\sigma$ of the K2 value. Based on a model of the background stellar population and the absence of nearby sources in our AO imaging, we estimate the probability that a background eclipsing binary could cause a false positive to be $< 2\times 10^{-5}$. We also show that given the almost constant transit depths in the five passbands, EPIC 206318379 cannot have a physically associated companion later than M4, and the probability that it has another M4 dwarf is low as well ($\approx 0.0721_{-0.036}^{+0.023}$), even in which case the size of EPIC 206318379b falls on the planetary regime. EPIC 206318379b has the same radius (within $1\sigma$) and experiences a similar irradiation from its host star as the well-studied GJ 1214b. A comparison between the atmospheric properties of these two objects with future observations would be especially interesting.

[41]  arXiv:1511.08516 [pdf, ps, other]
Title: Modulation and diurnal variation in axionic dark matter searches
Authors: Y. Semertzidis (Center for Axion and Precision Physics Research, IBS, Daejeon, Republic of Korea), J.D. Vergados (Centre for the Subatomic Structure of Matter (CSSM), University of Adelaide)
Comments: 16 pages,9 figures, To appear in the proceedings of the 18th International Conference From the Planck Scale to the Electroweak Scale 25-29 May 2015 Ioannina, Greece
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)

In the present work we study possible time dependent effects in Axion Dark Matter searches employing resonant cavities. We find that the width of the resonance, which depends on the axion mean square velocity in the local frame, will show an annual variation due to the motion of the Earth around the sun (modulation). Furthermore, if the experiments become directional, employing suitable resonant cavities, one expects large asymmetries in the observed widths relative to the sun's direction of motion. Due to the rotation of the Earth around its axis, these asymmetries will manifest themselves as a diurnal variation in the observed width.

[42]  arXiv:1511.08518 [pdf, other]
Title: IceCube Constraints on Fast-Spinning Pulsars as High-Energy Neutrino Sources
Comments: 21 pages, 8 figures, to be submitted to JCAP
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Relativistic winds of fast-spinning pulsars have been proposed as a potential site for cosmic-ray acceleration from very high energies (VHE) to ultrahigh energies (UHE). We re-examine conditions for high-energy neutrino production, considering the interaction of accelerated particles with baryons of the expanding supernova ejecta and the radiation fields in the wind nebula. We make use of the current IceCube sensitivity in diffusive high-energy neutrino background, in order to constrain the parameter space of the most extreme neutron stars as sources of VHE and UHE cosmic rays. We demonstrate that the current non-observation of $10^{18}$ eV neutrinos put stringent constraints on the pulsar scenario. For a given model, birthrates, ejecta mass and acceleration efficiency of the magnetar sources can be constrained. When we assume a proton cosmic ray composition and spherical supernovae ejecta, we find that the IceCube limits almost exclude their significant contribution to the observed UHE cosmic-ray flux. Furthermore, we consider scenarios where a fraction of cosmic rays can escape from jet-like structures piercing the ejecta, without significant interactions. Such scenarios would enable the production of UHE cosmic rays and help remove the tension between their EeV neutrino production and the observational data.

[43]  arXiv:1511.08519 [pdf, other]
Title: An advanced leakage scheme for neutrino treatment in astrophysical simulations
Comments: 22 Pages, 12 Figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

We present an Advanced Spectral Leakage (ASL) scheme to model neutrinos in the context of core-collapse supernovae and compact binary mergers. Based on previous gray leakage schemes, the ASL scheme computes the neutrino cooling rates by interpolating local production and diffusion rates (relevant in optically thin and thick regimes, respectively), separately for discretized values of the neutrino energy. Neutrino trapped components are also modeled, based on equilibrium and timescale arguments. The better accuracy achieved by the spectral treatment allows a more reliable computation of neutrino heating rates in optically thin conditions. The scheme has been calibrated and tested against Boltzmann transport in the context of Newtonian spherically symmetric models of core-collapse supernovae. ASL shows a very good qualitative and a partial quantitative agreement, for key quantities from collapse to a few hundreds of milliseconds after core bounce. We have proved the adaptability and flexibility of our ASL scheme coupling it to an axisymmetric Eulerian and to a three-dimensional SPH code to simulate core-collapse. Therefore, the neutrino treatment presented here is ideal for large parameter-space explorations, parametric studies, high-resolution tests, code developments, and long-term modeling of asymmetric configurations, where more detailed neutrino treatments are not available or currently computationally too expensive.

[44]  arXiv:1511.08534 [pdf, ps, other]
Title: 3D Modeling of Spectra and Light Curves of Hot Jupiters; A First Approach
Comments: The paper has been formally accepted for publication in Revista Mexicana de Astronomia y Astrofisica (RevMxAA). It will appear in Vol. 52, Num 1, April, 2016. 21 pages, 9 Figures, 3 Tables. arXiv admin note: text overlap with arXiv:astro-ph/0104262, arXiv:0809.2089 by other authors
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

In this paper, a detailed Global Circulation Model was employed to feed the PHOENIX code to calculate 3D spectra and light curves of hot Jupiters. Cloud free and dusty radiative luxes for the planet HD179949b were modeled to show differences between them. The PHOENIX simulations can explain the broad features of the observed 8 {\mu}m light curves, including the fact that the planet-star flux ratio peaks before the secondary eclipse. The PHOENIX reflection spectrum matches the Spitzer secondary-eclipse depth at 3.6 {\mu}m and underpredicts the eclipse depths at 4.5, 5.8 and 8.0 {\mu}m. These discrepancies result from the chemical composition and provide motivation for incorporating different metallicities in future studies.

[45]  arXiv:1511.08548 [pdf, other]
Title: A coupled 2$\times$2D Babcock-Leighton solar dynamo model. I. Surface magnetic flux evolution
Journal-ref: The Astrophysical Journal, Volume 810, Issue 1, article id. 78, 18 pp. (2015)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The need for reliable predictions of the solar activity cycle motivates the development of dynamo models incorporating a representation of surface processes sufficiently detailed to allow assimilation of magnetographic data. In this series of papers we present one such dynamo model, and document its behavior and properties. This first paper focuses on one of the model's key components, namely surface magnetic flux evolution. Using a genetic algorithm, we obtain best-fit parameters of the transport model by least-squares minimization of the differences between the associated synthetic synoptic magnetogram and real magnetographic data for activity cycle 21. Our fitting procedure also returns Monte Carlo-like error estimates. We show that the range of acceptable surface meridional flow profiles is in good agreement with Doppler measurements, even though the latter are not used in the fitting process. Using a synthetic database of bipolar magnetic region (BMR) emergences reproducing the statistical properties of observed emergences, we also ascertain the sensitivity of global cycle properties, such as the strength of the dipole moment and timing of polarity reversal, to distinct realizations of BMR emergence, and on this basis argue that this stochasticity represents a primary source of uncertainty for predicting solar cycle characteristics.

[46]  arXiv:1511.08553 [pdf, other]
Title: Beltrami state in black-hole accretion disk: A magnetofluid approach
Comments: 8 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

Using the magnetofluid unification framework, we show that the accretion disk plasma (embedded in the background geometry of a blackhole) can relax to a class of states known as the Beltrami-Bernoulli (BB) equilibria. Modeling the disk plasma as a Hall MHD system, we find that the space-time curvature can significantly alter the magnetic/velocity decay rate as we move away from the compact object; the velocity profiles in BB states, for example, deviate substantially from the predicted corresponding geodesic velocity profiles. These departures imply a rich interplay of plasma dynamics and general relativity revealed by examining the corresponding Bernoulli condition representing "homogeneity" of total energy. The relaxed states have their origin in the constraints provided by the two helicity invariants of Hall MHD. These helicities conspire to introduce a new oscillatory length scale into the system that is strongly influenced by relativistic and thermal effects.

[47]  arXiv:1511.08567 [pdf, ps, other]
Title: Observations of Protostellar Outflow Feedback in Clustered Star Formation
Authors: Fumitaka Nakamura (NAOJ)
Comments: 6 pages, 2 figures, The 6th Zermatt ISM Symposium, Conditions and Impact of Star Formation, From Lab to Space; Zermatt, Switzerland, 2015, September 7-11; In memory of Charles H. Townes
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We discuss the role of protostellar outflow feedback in clustered star formation using the observational data of recent molecular outflow surveys toward nearby cluster-forming clumps. We found that for almost all clumps, the outflow momentum injection rate is significantly larger than the turbulence dissipation rate. Therefore, the outflow feedback is likely to maintain supersonic turbulence in the clumps. For less massive clumps such as B59, L1551, and L1641N, the outflow kinetic energy is comparable to the clump gravitational energy. In such clumps, the outflow feedback probably affects significantly the clump dynamics. On the other hand, for clumps with masses larger than about 200 M$_\odot$, the outflow kinetic energy is significantly smaller than the clump gravitational energy. Since the majority of stars form in such clumps, we conclude that outflow feedback cannot destroy the whole parent clump. These characteristics of the outflow feedback support the scenario of slow star formation.

[48]  arXiv:1511.08596 [pdf, ps, other]
Title: The Innermost Extremes of Black Hole Accretion
Authors: A.C. Fabian
Comments: 6 pages. 12 figures, in press Astronomical Notes (Proc. XMM-Newton 2015 Science Workshop)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The inner 20 gravitational radii around the black hole at the centre of luminous Active Galactic Nuclei and stellar mass Black Hole Binaries are now being routinely mapped by X-ray spectral-timing techniques. Spectral blurring and reverberation of the reflection spectrum are key tools in this work. In the most extreme AGN cases with high black hole spin, when the source appears in a low state, observations probe the region within 1 gravitational radius of the event horizon. The location, size and operation of the corona, which generates the power-law X-ray continuum, are also being revealed.

[49]  arXiv:1511.08608 [pdf, ps, other]
Title: The physical fundamental plane of black hole activity: revisited
Authors: Xiang Liu, Zhenhua Han, Zhen Zhang (Xinjiang Astronomical Observatory, CAS)
Comments: 7 pages, 5 figures, accepted for publication in Astrophysics & Space Sciences
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The correlation between the jet power and accretion disk luminosity is investigated for active galactic nuclei (AGNs) and black hole X-ray binaries (BHXBs) from the literature. The power-law correlation index is steep ($\mu \sim$ 1.0--1.4) for radio loud quasars and the `outliers' track of BHXBs, and it is flatter ($\mu \sim$ 0.3--0.6) for radio loud galaxies and the standard track of BHXBs. The steep-index groups are mostly at higher accretion rates (peaked at Eddington ratio $>$ 0.01) and the flatter-index groups are at relatively low accretion rates (peaked at Eddington ratio $<$ 0.01), implying that the former groups could be dominated by the inner disk accretion of black hole, while the jet in latter groups would be a hybrid production of the accretion and black hole spin. We could still have a fundamental plane of black hole activity for the BHXBs and AGNs with diverse (maybe two kinds of) correlation indices. It is noted that the fundamental plane of black hole activity should be referred to the correlation between the jet power and disk luminosity or equivalently to the correlation between jet power, Eddington ratio and black hole mass, rather than the jet power, disk luminosity and black hole mass.

[50]  arXiv:1511.08618 [pdf, ps, other]
Title: Wave propagation in a solar quiet region and the influence of the magnetic canopy
Comments: 10 pages, 6 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Aims. We seek indications or evidence of transmission/conversion of magnetoacoustic waves at the magnetic canopy, as a result of its impact on the properties of the wave field of the photosphere and chromosphere. Methods. We use cross-wavelet analysis to measure phase differences between intensity and Doppler signal oscillations in the Halpha, CaII H, and G-band.We use the height of the magnetic canopy to create appropriate masks to separate internetwork (IN) and magnetic canopy regions. We study wave propagation and differences between these two regions. Results. The magnetic canopy affects wave propagation by lowering the phase differences of progressive waves and allowing the propagation of waves with frequencies lower than the acoustic cut-off. We also find indications in the Doppler signals of Halpha of a response to the acoustic waves at the IN, observed in the CaII H line. This response is affected by the presence of the magnetic canopy. Conclusions. Phase difference analysis indicates the existence of a complicated wave field in the quiet Sun, which is composed of a mixture of progressive and standing waves. There are clear imprints of mode conversion and transmission due to the interaction between the p-modes and small-scale magnetic fields of the network and internetwork.

[51]  arXiv:1511.08619 [pdf, ps, other]
Title: Advanced Environment for Knowledge Discovery in the VIALACTEA Project
Comments: Astronomical Data Analysis Software and Systems XXV. Proceedings of a Conference held from October 25th to 30th, 2015 at Rydges World Square in Sydney, Australia
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The VIALACTEA project aims at building a predictive model of star formation in our galaxy. We present the innovative integrated framework and the main technologies and methodologies to reach this ambitious goal.

[52]  arXiv:1511.08640 [pdf, ps, other]
Title: Asteroids@home - A BOINC distributed computing project for asteroid shape reconstruction
Journal-ref: Astronomy and Computing 13 (2015) 80-84
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present the project Asteroids@home that uses distributed computing to solve the time-consuming inverse problem of shape reconstruction of asteroids. The project uses the Berkeley Open Infrastructure for Network Computing (BOINC) framework to distribute, collect, and validate small computational units that are solved independently at individual computers of volunteers connected to the project. Shapes, rotational periods, and orientations of the spin axes of asteroids are reconstructed from their disk-integrated photometry by the lightcurve inversion method.

[53]  arXiv:1511.08641 [pdf, ps, other]
Title: A Large Deviation Principle at play in Large-Scale Structure cosmology
Comments: 5 pages, 2 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present an application of Large Deviation Theory to the problem of structure growth on large-scale structure cosmology. Starting from gaussian distributed overdensities on concentric spherical shells, we show that a Large Deviation Principle holds for the densities on the corresponding shells after gravitational evolution if no shell-crossing happens. As consequences of the Large Deviation Principle we obtain the cumulant generating function for the non-linear densities, and present formulae to compute the cumulant generating function for general window functions.

[54]  arXiv:1511.08650 [pdf, other]
Title: Non-parametric determination of H and He IS fluxes from cosmic-ray data
Comments: 10 pages, 6 figures, 3 tables
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

Top-of-atmosphere (TOA) cosmic-ray (CR) fluxes from satellites and balloon-borne experiments are snapshots of the solar activity imprinted on the interstellar (IS) fluxes. Given a series of snapshots, the unknown IS flux shape and the level of modulation (for each snapshot) can be recovered. We wish (i) to provide the most accurate determination of the IS H and He fluxes from TOA data only, (ii) to obtain the associated modulation levels (and uncertainties) fully accounting for the correlations with the IS flux uncertainties, and (iii) to inspect whether the minimal Force-Field approximation is sufficient to explain all the data at hand. Using H and He TOA measurements, including the recent high precision AMS, BESS-Polar and PAMELA data, we perform a non-parametric fit of the IS fluxes $J^{\rm IS}_{\rm H,~He}$ and modulation level $\phi_i$ for each data taking period. We rely on a Markov Chain Monte Carlo (MCMC) engine to extract the PDF and correlations (hence the credible intervals) of the sought parameters. Despite H and He being the most abundant and best measured CR species, several datasets must be excluded from the analysis due to inconsistencies with other measurements. From the subset of data passing our consistency cut, we provide ready-to-use best-fit and credible intervals for the H and He IS fluxes from MeV/n to PeV/n energy (with a relative precision in the range $[2-10\%]$ at 1$\sigma$). Given the strong correlation between $J^{\rm IS}$ and $\phi_i$ parameters, the uncertainties on $J^{\rm IS}$ translate into $\Delta\phi\approx \pm 30$ MV (at 1$\sigma$) for all experiments. We also find that the presence of $^3$He in He data biases $\phi$ towards higher $\phi$ values by $\sim 30$ MV. The force-field approximation, despite its limitation, gives an excellent ($\chi^2/$dof$=1.02$) description of the recent high-precision TOA H and He fluxes.

[55]  arXiv:1511.08679 [pdf, ps, other]
Title: Evidence for Reflected Light from the Most Eccentric Exoplanet Known
Comments: 12 pages, 9 figures, 4 tables, submitted to the Astrophysical Journal. Comments welcome!
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve the our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.25 degrees, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations are likely caused by reflected light from the planet's atmosphere and the dramatic change in star--planet separation surrounding the periastron passage.

[56]  arXiv:1511.08686 [pdf, other]
Title: Spectroradiometry with Space Telescopes
Comments: 87 pages, 16 figures, AARev 2015, Springer svjour3.cls
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Radiometry has been of fundamental importance in astronomy from the early beginnings. Initially, astronomers had their own radiometric system, based on extraterrestrial standards, namely the irradiance of stars expressed in visual magnitudes. Observing and comparing magnitudes in specific spectral bands then led to the astronomical spectrophotometry. The advent of astronomical high-resolution spectroscopy offered the possibility to interpret observations through physical models of stellar atmospheres. Such models had to be constructed based on physics-related units, and such units, rather than magnitudes, were then used for observational tests of the models. In this review, we provide an overview of how to achieve a valid laboratory calibration, and discuss ways to reliably extend this calibration to the spectroscopic telescope's performance in space. Recently, the quest for independent calibrations traceable to laboratory standards has become a well-supported aim, and has led to plans for now also launching calibration rockets for the visible and infrared spectral range. A survey of the calibration of instruments observing from the X-ray to the infrared spectral domains rounds off this review.

[57]  arXiv:1511.08690 [pdf, other]
Title: CMB reconstruction from the WMAP and Planck PR2 data
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In this article, we describe a new estimate of the Cosmic Microwave Background (CMB) intensity map reconstructed by a joint analysis of the full Planck 2015 data (PR2) and WMAP nine-years. It provides more than a mere update of the CMB map introduced in (Bobin et al. 2014b) since it benefits from an improvement of the component separation method L-GMCA (Local-Generalized Morphological Component Analysis) that allows the efficient separation of correlated components (Bobin et al. 2015). Based on the most recent CMB data, we further confirm previous results (Bobin et al. 2014b) showing that the proposed CMB map estimate exhibits appealing characteristics for astrophysical and cosmological applications: i) it is a full sky map that did not require any inpainting or interpolation post-processing, ii) foreground contamination is showed to be very low even on the galactic center, iii) it does not exhibit any detectable trace of thermal SZ contamination. We show that its power spectrum is in good agreement with the Planck PR2 official theoretical best-fit power spectrum. Finally, following the principle of reproducible research, we provide the codes to reproduce the L-GMCA, which makes it the only reproducible CMB map.

[58]  arXiv:1511.08695 [pdf, other]
Title: Turning noise into signal: learning from the scatter in the Hubble diagram
Authors: Tiago Castro, Miguel Quartin, Sandra Benitez-Herrera (Rio de Janeiro Federal U.)
Comments: 13 pages, 7 figures. Comments are welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The supernova Hubble diagram residual contains valuable information on both the present matter power spectrum and its growth history. In this paper we show that this information can be retrieved with precision by combining both peculiar velocity and weak-lensing analysis on the data. To wit, peculiar velocity induces correlations on the nearby supernovae while lensing induces a non-Gaussian dispersion in faraway objects. We show that both effects have almost orthogonal degeneracies and discuss how they can be extracted simultaneously from the data. We analyze the JLA supernova catalog in a 14-dimensional parameter space, assuming a flexible growth-rate index gamma. We arrive at the following marginalized constraints: sigma8 = $1.16^{+0.23}_{-0.47}$ and gamma = $0.80^{+0.29}_{-0.34}$. We note that these constraints complement well the ones obtained from other data sets. Assuming instead GR as the correct gravitation theory (and thus gamma = 0.55), the constraints in sigma8 tighten further: sigma8 = $0.89^{+0.18}_{-0.21}$.

[59]  arXiv:1511.08699 [pdf, ps, other]
Title: Intermittent Self-Sustaining Star Formation in Low-Redshift Galaxies Exhibiting a Peak Metallicity Plateau
Authors: Martin Harwit
Comments: 10 pages, 1 figure: Accepted for publication in the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The decline of star formation in massive low-redshift galaxies, often referred to as quenching, has been attributed to a variety of factors. Some proposals suggest that erupting active galactic nuclei may strip galaxies of their interstellar medium, and thus the ability to form stars. Here, we note that, whereas star formation is universal in small, low-redshift galaxies, fractional duty cycles of star formation steadily decline in galaxies of increasing mass, although star formation may not cease entirely. We show that, when infall of gas from extragalactic space ceases, galaxies of high stellar mass appear to sustain star formation on gas liberated in mass loss from evolved low- and intermediate-mass stars admixed with occasional Type II supernova ejecta. This model quantitatively accounts for the universal limiting metallicity plateau at a ratio of oxygen to hydrogen atoms, Z(O) = n(O)/n(H) = 0.0013, characterizing high-mass intermittently star-forming galaxies. We show that, when fractional duty cycles are specifically taken into account, the star formation rates of galaxies on this plateau correspond to mass loss rates from evolving stars in rough agreement with observed estimates. Far-infrared continuum and fine-structure line observations, as well as molecular data, may soon be able to resolve whether or not low levels of sporadic star formation can be sustained indefinitely in massive galaxies.

[60]  arXiv:1511.08725 [pdf, other]
Title: Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC6720
Comments: Accepted by MNRAS. 5 pages
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Evolved stars are primary sources for the formation of polycyclic aromatic hydrocarbons (PAHs) and dust grains. Their circumstellar chemistry is usually designated as either oxygen-rich or carbon-rich, although dual-dust chemistry objects, whose infrared spectra reveal both silicate- and carbon-dust features, are also known. The exact origin and nature of this dual-dust chemistry is not yet understood. Spitzer-IRS mid-infrared spectroscopic imaging of the nearby, oxygen-rich planetary nebula NGC6720 reveals the presence of the 11.3 micron aromatic (PAH) emission band. It is attributed to emission from neutral PAHs, since no band is observed in the 7 to 8 micron range. The spatial distribution of PAHs is found to closely follow that of the warm clumpy molecular hydrogen emission. Emission from both neutral PAHs and warm H2 is likely to arise from photo-dissociation regions associated with dense knots that are located within the main ring. The presence of PAHs together with the previously derived high abundance of free carbon (relative to CO) suggest that the local conditions in an oxygen-rich environment can also become conducive to in-situ formation of large carbonaceous molecules, such as PAHs, via a bottom-up chemical pathway. In this scenario, the same stellar source can enrich the interstellar medium with both oxygen-rich dust and large carbonaceous molecules.

[61]  arXiv:1511.08727 [pdf, other]
Title: Dynamics of the 3/1 planetary mean-motion resonance. An application to the HD60532 b-c planetary system
Comments: Accepted for publication at Celestial Mechanics and Dynamical Astronomy. 25 pages, 15 figures. Comments are welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

In this paper, we use a semi-analytical approach to analyze the global structure of the phase space of the planar planetary 3/1 mean-motion resonance, in cases where the outer planet is more massive than its inner companion. We show that the resonant dynamics can be described using only two fundamental parameters, the total angular momentum and the scaling parameter. The topology of the Hamiltonian function describing the resonant behaviour is studied on the representative planes that allows us to investigate a large domain of the phase space of the three-body problem without time-expensive numerical integrations of the equations of motion, and without any restriction on the magnitude of the planetary eccentricities. The families of the well known Apsidal Corotation Resonances (ACR) parameterized by the planetary mass ratio are obtained and their stability is analyzed. The main dynamical features in the domains around ACR are also investigated in detail by means of spectral analysis techniques, which allow us to detect the regions of different regimes of motion of resonant systems. The construction of dynamical maps for various values of the total angular momentum shows the evolution of domains of stable motion with the eccentricities, identifying possible configurations suitable for exoplanetary systems.

[62]  arXiv:1511.08730 [pdf, ps, other]
Title: Evidence for a Toroidal Magnetic-Field Component in 5C4.114 on Kiloparsec Scales
Comments: 5 pages, 2 figures
Journal-ref: A&A, vol. 583, p. 96 (2015)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

A monotonic, statistically significant gradient in the observed Faraday Rotation Measure (RM) across the jet of an Active Galactic Nucleus (AGN) reflects a corresponding gradient in the electron density and/or line-of-sight magnetic (B) field. Such gradients may indicate the presence of a toroidal B field component, possibly associated with a helical jet B field. Although transverse RM gradients have been reported across a number of parsec-scale AGN jets, the same is not true on kiloparsec scales, suggesting that other (e.g. random) B-field components usually dominate on these larger scales. We have identified an extended, monotonic transverse RM gradient across the Northern lobe of a previously published Very Large Array (kiloparsec-scale) RM image of 5C4.114. We reanalyzed these VLA data in order to determine the significance of this RM gradient. The RM gradient across the Northern kiloparsec-scale lobe structure of 5C4.114 has a statistical significance of about 4sigma. There is also a somewhat less prominent monotonic transverse RM gradient across the Southern jet/lobe (significance ~ 3sigma). Other parts of the RM distribution observed across the source are patchy and show no obvious order.This suggests that we are observing a random RM component associated with the foreground material in the cluster in which the radio source is located and through which it is viewed, superposed on a more ordered RM component that arises in the immediate vicinity of the AGN jets. We interpret the transverse RM gradient as reflecting the systematic variations of the line-of-sight component of a helical or toroidal B field associated with the jets of 5C4.114. These results suggest that the helical field that arises due to the joint action of the rotation of the central black hole and its accretion disc and the jet outflow can survive to distances of thousands of parsec from the central engine.

[63]  arXiv:1511.08736 [pdf, ps, other]
Title: What $ξ$ ? Cosmological constraints on the non-minimal coupling constant
Authors: Orest Hrycyna
Comments: 22 pages, 2 figs. arXiv admin note: text overlap with arXiv:1506.03429
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

In dynamical system describing evolution of universe with the flat Friedmann-Robertson-Walker symmetry filled with barotropic dust matter and non-minimally coupled scalar field with a constant potential function an invariant manifold of the de Sitter state is used to obtain exact solutions of the reduced dynamics. Using observational data coming from distant supernovae type Ia, the Hubble function $H(z)$ measurements and information coming from the Alcock-Paczy$\'n$ski test we find cosmological constraints on the non-minimal coupling constant $\xi$ between the scalar curvature and the scalar field. For all investigated models we can exclude negative values of this parameter at the $68\%$ confidence level. We obtain coherence with values needed for conformal coupling of the scalar field in higher dimensional theories of gravity.

[64]  arXiv:1511.08741 [pdf, other]
Title: An assessment of the "too big to fail" problem for field dwarf galaxies in view of baryonic feedback effects
Authors: Emmanouil Papastergis (1), Francesco Shankar (2) ((1) Kapteyn Astronomical Institute, (2) University of Southampton)
Comments: Submitted to A&A.9 pages, 5 figures (+ appendix)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Recent studies have established that extreme dwarf galaxies --whether satellites or field objects-- suffer from the so called "too big to fail" (TBTF) problem. Put simply, the TBTF problem consists of the fact that it is difficult to explain both the measured kinematics of dwarfs and their observed number density within the LCDM framework. The most popular proposed solutions to the problem involve baryonic feedback processes. For example, reionization and baryon depletion can decrease the abundance of halos that are expected to host dwarf galaxies. Moreover, feedback related to star formation can alter the dark matter density profile in the central regions of low-mass halos. In this article we assess the TBTF problem for field dwarfs, taking explicitly into account the baryonic effects mentioned above. We find that 1) reionization feedback cannot resolve the TBTF problem on its own, because the halos in question are too massive to be affected by it, and that 2) the degree to which profile modification can be invoked as a solution to the TBTF problem depends on the radius at which galactic kinematics are measured. Based on a literature sample of about 90 dwarfs with interferometric observations in the 21cm line of atomic hydrogen (HI), we conclude that the TBTF problem persists despite baryonic effects. However, the preceding statement assumes that the sample under consideration is representative of the general population of field dwarfs. In addition, the unexplained excess of dwarf galaxies in LCDM could be as small as a factor of ~ 1.8, given the current uncertainties in the measurement of the galactic velocity function. Both of these caveats highlight the importance of upcoming uniform surveys with HI interferometers for advancing our understanding of the issue.

[65]  arXiv:1511.08790 [pdf, other]
Title: Solar Modulation of the Proton Local Interstellar Spectrum with AMS-02, Voyager 1 and PAMELA
Comments: 8 pages, 13 figures, 3 tables
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

In recent years, the increasing precision of direct cosmic rays measurements opened the door to indirect searches of dark matter with high-sensitivity and to more accurate predictions for radiation doses received by astronauts and electronics in space. The key ingredients in the study of these phenomena are the knowledge of the local interstellar spectrum (LIS) of galactic cosmic rays (GCRs) and the understanding of how the solar modulation affects the LIS inside the heliosphere. Voyager 1, AMS-02 and PAMELA measurements of proton fluxes provide invaluable information, allowing us to shed light on the shape of the LIS and the details of the solar modulation during solar cycles 23 and 24. A new parametrization of the proton LIS is presented, based on the latest data from Voyager 1 and AMS-02. Using the framework of the force-field approximation, the solar modulation parameter is extracted from the time-dependent proton fluxes measured by PAMELA. A modified version of the force-field approximation with an energy-dependent modulation parameter is introduced, yielding better results on proton data than the force-field approximation. The results are compared with the modulation parameter inferred by neutron monitors.

[66]  arXiv:1511.08793 [pdf, other]
Title: Constraints on Primordial Magnetic Fields from Inflation
Comments: 26 pages
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

We present generic bounds on magnetic fields produced from cosmic inflation. By investigating field bounds on the vector potential, we constrain both the quantum mechanical production of magnetic fields and their classical growth in a model independent way. For classical growth, we show that only if the reheating temperature is as low as T_{reh} <~ 10^2 MeV can magnetic fields of 10^{-15} G be produced on Mpc scales in the present universe. For purely quantum mechanical scenarios, even stronger constraints are derived. Our bounds on classical and quantum mechanical scenarios apply to generic theories of inflationary magnetogenesis with a two-derivative time kinetic term for the vector potential. In both cases, the magnetic field strength is limited by the gravitational back-reaction of the electric fields that are produced simultaneously. As an example of quantum mechanical scenarios, we construct vector field theories whose time diffeomorphisms are spontaneously broken, and explore magnetic field generation in theories with a variable speed of light. Transitions of quantum vector field fluctuations into classical fluctuations are also analyzed in the examples.

[67]  arXiv:1511.08796 [pdf, other]
Title: On the feasibility of RADAR detection of high-energy cosmic neutrinos
Comments: Proceedings of the 34th International Cosmic Ray Conference, The Hague 2015, to be published
Journal-ref: PoS(ICRC2015)1168
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

We discuss the radar detection technique as a probe for high-energy cosmic neutrino induced particle cascades in a dense medium like ice. With the recent detection of high-energy cosmic neutrinos by the IceCube neutrino observatory the window to neutrino astronomy has been opened. We discuss a new technique to detect cosmic neutrinos at even higher energies than those covered by IceCube, but with an energy threshold below the currently operating Askaryan radio detectors. A calculation for the radar return power, as well as first experimental results will be presented.