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[1]  arXiv:1607.06810 [pdf, ps, other]
Title: Another one grinds the dust: Variability of the planetary debris disc at the white dwarf SDSS J104341.53+085558.2
Comments: 11 pages, 5 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We report nine years of optical spectroscopy of the metal-polluted white dwarf SDSS J104341.53+085558.2, which presents morphological variations of the line profiles of the 8600 \AA\ Ca II triplet emission from the gaseous component of its debris disc. Similar changes in the shape of the Ca II triplet have also been observed in two other systems that host a gaseous disc, and are likely related to the same mechanism. We report the Mg, Si, and Ca abundances of the debris detected in the photosphere of SDSS J1043+0855, place upper limits on O and Fe, and derive an accretion rate of (2.5 - 12)x$10^8$ g/s, consistent with those found in other systems with detected debris discs. The Mg/Si ratio and the upper limit on the Fe/Si ratio of the accreted material broadly agree with those found for the crust of the Earth. We also review the range of variability observed among white dwarfs with planetary debris discs.

[2]  arXiv:1607.06811 [pdf, ps, other]
Title: Infrared High-Resolution Integrated Light Spectral Analyses of M31 Globular Clusters from APOGEE
Comments: Accepted for publication in the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Chemical abundances are presented for 25 M31 globular clusters (GCs), based on moderately high resolution (R = 22, 500) H-band integrated light spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Infrared spectra offer lines from new elements, of different strengths, and at higher excitation potentials compared to the optical. Integrated abundances of C, N, and O are derived from CO, CN, and OH molecular features, while Fe, Na, Mg, Al, Si, K, Ca, and Ti abundances are derived from atomic features. These abundances are compared to previous results from the optical, demonstrating the validity and value of infrared integrated light analyses. The CNO abundances are consistent with typical tip of the red giant branch stellar abundances, but are systematically offset from optical, Lick index abundances. With a few exceptions, the other abundances agree between the optical and the infrared within the 1{\sigma} uncertainties. The first integrated K abundances are also presented, and demonstrate that K tracks the alpha-elements. The combination of infrared and optical abundances allows better determinations of GC properties, and enables probes of the multiple populations in extragalactic GCs. In particular, the integrated effects of the Na/O anticorrelation can be directly examined for the first time.

[3]  arXiv:1607.06815 [pdf, ps, other]
Title: Light dark matter scattering in outer neutron star crusts
Comments: 14 pages, 3 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

We calculate for the first time the phonon excitation rate in the outer crust of a neutron star due to scattering from light dark matter (LDM) particles gravitationally boosted into the star. We consider dark matter particles in the sub-GeV mass range scattering off a periodic array of nuclei through an effective scalar-vector interaction with nucleons. We find that LDM effects cause a modification of the net number of phonons in the lattice as compared to the standard thermal result. In addition, we estimate the contribution of LDM to the ion-ion thermal conductivity in the outer crust and find that it can be significantly enhanced at large densities. Our results imply that for magnetized neutron stars the LDM-enhanced global conductivity in the outer crust will tend to reduce the anisotropic heat conduction between perpendicular and parallel directions to the magnetic field.

[4]  arXiv:1607.06816 [pdf, ps, other]
Title: Chemical Enrichment of the Pre-Solar Cloud by Supernova Dust Grains
Comments: 16 pages, 10 figures, Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The presence of short-lived radioisotopes (SLRs) in solar system meteorites has been interpreted as evidence that the solar system was exposed to a supernova shortly before or during its formation. Yet results from hydrodynamical models of SLR injection into the proto-solar cloud or disc suggest that gas-phase mixing may not be efficient enough to reproduce the observed abundances. As an alternative, we explore the injection of SLRs via dust grains as a way to overcome the mixing barrier. We numerically model the interaction of a supernova remnant containing SLR-rich dust grains with a nearby molecular cloud. The dust grains are subject to drag forces and both thermal and non-thermal sputtering. We confirm that the expanding gas shell stalls upon impact with the dense cloud and that gas-phase SLR injection occurs slowly due to hydrodynamical instabilities at the cloud surface. In contrast, dust grains of sufficient size (> 1 micron) decouple from the gas and penetrate into the cloud within 0.1 Myr. Once inside the cloud, the dust grains are destroyed by sputtering, releasing SLRs and rapidly enriching the dense (potentially star-forming) regions. Our results suggest that SLR transport on dust grains is a viable mechanism to explain SLR enrichment.

[5]  arXiv:1607.06818 [pdf, ps, other]
Title: A synthetic model of the gravitational wave background from evolving binary compact objects
Comments: 13 pages, 6 figures. Comments welcome
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Modeling the stochastic gravitational wave background from various astrophysical sources is a key objective in view of upcoming observations with ground- and space-based gravitational wave observatories such as Advanced LIGO, VIRGO, eLISA and PTA. We develop a synthetic model framework that follows the evolution of single and binary compact objects in an astrophysical context. We describe the formation and merger rates of binaries, the evolution of their orbital parameters with time and the spectrum of emitted gravitational waves at different stages of binary evolution. Our approach is modular and allows us to test and constrain different ingredients of the model, including stellar evolution, black hole formation scenarios and the properties of binary systems. We use this framework in the context of a particularly well-motivated astrophysical setup to calculate the gravitational wave background from several types of sources, including inspiraling stellar-mass binary black holes that have not merged during a Hubble time. We find that this signal, albeit weak, has a characteristic shape that can help constrain the properties of binary black holes in a way complementary to observations of the background from merger events. We discuss possible applications of our framework in the context of other gravitational wave sources, such as supermassive black holes.

[6]  arXiv:1607.06820 [pdf, ps, other]
Title: A Direct Measurement of the High-Mass End of the Velocity Dispersion Function at z~0.55 from SDSS-III/BOSS
Comments: 11 pages, 4 figures. Submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We report the first direct spectroscopic measurement of the velocity dispersion function (VDF) for the high-mass red sequence (RS) galaxy population at redshift $z \sim 0.55$. We achieve high precision by using a sample of 600,000 massive galaxies with spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) of the third Sloan Digital Sky Survey (SDSS-III), covering stellar masses $M_* \gtrsim 10^{11} M_{\odot}$. We determine the VDF by projecting the joint probability-density function (PDF) of luminosity $L$ and velocity dispersion $\sigma$, i.e. $p(L, \sigma)$, defined by our previous measurements of the RS luminosity function (LF) and $L-\sigma$ relation for this sample. These measurements were corrected from red--blue galaxy population confusion, photometric blurring, incompleteness and selection effects within a forward-modeling framework that furthermore correctly accommodates the low spectroscopic signal-to-noise ratio of the individual BOSS spectra. The $z\sim0.55$ RS VDF is in agreement with the $z\sim0$ early-type galaxy (ETG) VDF at $\log_{10} \sigma \gtrsim 2.47$, but the number density of $z=0.55$ RS galaxies is larger than that of $z=0$ ETG galaxies at $2.35 \gtrsim \log_{10} \sigma \gtrsim 2.47$. The extrapolation of an intermediate-mass L-$\sigma$ relation towards the high-mass end in previous low-z works may be responsible for this trend, although this interpretation is still subject to small differences in the way both populations are defined. We also provide the sample PDF for the RS population (i.e. uncorrected for incompleteness), which is a key ingredient for gravitational lensing analyses using the BOSS sample.

[7]  arXiv:1607.06829 [pdf, other]
Title: A perturbation study of axisymmetric strongly magnetic degenerate stars : the case of super-Chandrasekhar white dwarfs
Comments: 10 pages, 10 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

In the presence of a strong magnetic field a stellar equilibrium configuration, aided by the Lorentz force, can support a larger mass than a non-magnetic one. This has been considered a possible explanation of the super-Chandrasekhar mass white dwarfs giving rise to over-luminous Type-Ia supernovae. We present here linear and non-linear perturbation studies of such strongly magetised configurations and show that axisymmetric configurations with poloidal or toroidal fields are unstable. The numerical evolution of the perturbations shows instability after about an Alfv\'en crossing time. This time scale is very short for the magnetically supported super-Chandrasekhar mass white dwarfs. Uniform rotation about the symmetry axis can reduce the growth rate but can not stabilize the super-massive configurations. It is concluded that long-lived super-Chandrasekhar mass white dwarfs supported by magnetic field are unlikely to occur in Nature.

[8]  arXiv:1607.06840 [pdf, other]
Title: Young stars and ionized nebulae in M83: comparing chemical abundances at high metallicity
Authors: Fabio Bresolin (U. of Hawaii), Rolf-Peter Kudritzki (U. of Hawaii), Miguel A. Urbaneja (Innsbruck), Wolfgang Gieren (Concepcion), I-Ting Ho (U. of Hawaii), Grzegorz Pietrzynski (Concepcion)
Comments: Accepted for publication in the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present spectra of 14 A-type supergiants in the metal-rich spiral galaxy M83. We derive stellar parameters and metallicities, and measure a spectroscopic distance modulus m-M = 28.47 +\- 0.10 (4.9 +\- 0.2 Mpc), in agreement with other methods. We use the stellar characteristic metallicity of M83 and other systems to discuss a version of the galaxy mass-metallicity relation that is independent of the analysis of nebular emission lines and the associated systematic uncertainties. We reproduce the radial metallicity gradient of M83, which flattens at large radii, with a chemical evolution model, constraining gas inflow and outflow processes. We carry out a comparative analysis of the metallicities we derive from the stellar spectra and published HII region line fluxes, utilizing both the direct, Te-based method and different strong-line abundance diagnostics. The direct abundances are in relatively good agreement with the stellar metallicities, once we apply a modest correction to the nebular oxygen abundance due to depletion onto dust. Popular empirically calibrated strong-line diagnostics tend to provide nebular abundances that underestimate the stellar metallicities above the solar value by ~0.2 dex. This result could be related to difficulties in selecting calibration samples at high metallicity. The O3N2 method calibrated by Pettini and Pagel gives the best agreement with our stellar metallicities. We confirm that metal recombination lines yield nebular abundances that agree with the stellar abundances for high metallicity systems, but find evidence that in more metal-poor environments they tend to underestimate the stellar metallicities by a significant amount, opposite to the behavior of the direct method.

[9]  arXiv:1607.06841 [pdf, other]
Title: Time-series Doppler imaging of the red giant HD 208472. Active longitudes and differential rotation
Comments: 12 pages, 11 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

HD 208472 is among the most active RS~CVn binaries with cool starspots. Decade-long photometry has shown that the spots seem to change their longitudinal appearance with a period of about six years, coherent with brightness variations. Our aim is to spatially resolve the stellar surface of HD 208472 and relate the photometric results to the true longitudinal and latitudinal spot appearance. Furthermore, we investigate the surface differential rotation pattern of the star. We employed three years of high-resolution spectroscopic data with a high signal-to-noise ratio (S/N) from the STELLA robotic observatory and determined new and more precise stellar physical parameters. Precalculated synthetic spectra were fit to each of these spectra, and we provide new spot-corrected orbital elements. A sample of 34 absorption lines per spectrum was used to calculate mean line profiles with a S/N of several hundred. A total of 13 temperature Doppler images were reconstructed from these line profiles with the inversion code iMap. Differential rotation was investigated by cross-correlating successive Doppler images in each observing season. Spots on HD 208472 are distributed preferably at high latitudes and less frequently around mid-to-low latitudes. No polar-cap like structure is seen at any epoch. We observed a flip-flop event between 2009 and 2010, manifested as a flip of the spot activity from phase 0.0 to phase 0.5, while the overall brightness of the star continued to increase and reached an all-time maximum in 2014. Cross-correlation of successive Doppler images suggests a solar-like differential rotation that is ~15 times weaker than that of the Sun.

[10]  arXiv:1607.06858 [pdf, other]
Title: New observational limits on dark radiation in brane-world cosmology
Comments: 4 Pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

A dark radiation term arises as a correction to the energy momentum tensor in the simplest five-dimensional RS-II brane-world cosmology. In this paper we revisit the constraints on dark radiation based upon the newest results for light-element nuclear reaction rates, observed light-element abundances and the power spectrum of the Cosmic Microwave Background (CMB). Adding the effect of dark radiation during big bang nucleosynthesis alters the Friedmann expansion rate causing the nuclear reactions to freeze out at a different temperature. This changes the final light element abundances at the end of BBN. Its influence on the CMB is to change the effective expansion rate at the surface of last scattering. We find that the BBN constraint reduces the the allowed range for dark radiation to between -12.1% and +6.2% of the photon background. Combining this result with fits to the CMB power spectrum constraint, the range decreases to -6.0% to +6.2%. Thus, we find, that the ratio of dark radiation to the background total relativistic mass energy density $\rho_{DR}/\rho$ is consistent with zero though there remains a very slight preference for a positive (rather than negative) contribution.

[11]  arXiv:1607.06861 [pdf, other]
Title: BICEP3 focal plane design and detector performance
Comments: 11 pages, 10 figures. To be published in Proc. SPIE. Presented at SPIE Astronomical Telescopes and Instrumentation Conference 9914: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, June 2016
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

BICEP3, the latest telescope in the BICEP/Keck program, started science observations in March 2016. It is a 550mm aperture refractive telescope observing the polarization of the cosmic microwave background at 95 GHz. We show the focal plane design and detector performance, including spectral response, optical efficiency and preliminary sensitivity of the upgraded BICEP3. We demonstrate 9.72$\mu$K$\sqrt{\textrm{s}}$ noise performance of the BICEP3 receiver.

[12]  arXiv:1607.06868 [pdf, ps, other]
Title: Formation and evolution of blue compact dwarfs: The origin of their steep rotation curves
Authors: A. Watts, K. Bekki
Comments: 13 pages, 11 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The origin of the observed steep rotation curves of blue compact dwarf galaxies (BCDs) remains largely unexplained by theoretical models of BCD formation. We therefore investigate the rotation curves in BCDs formed from mergers between gas- rich dwarf irregular galaxies based on the results of numerical simulations for BCD formation. The principal results are as follows. The dark matter of merging dwarf irregulars undergoes a central concentration so that the central density can become up to 6 times higher than those of the initial dwarf irregulars. However, the more compact dark matter halo alone can not reproduce the gradient differences observed between dwarf irregulars and BCDs. We provide further support that the central concentration of gas due to rapid gas-transfer to the central regions of dwarf-dwarf mergers is responsible for the observed difference in rotation curve gradients. The BCDs with central gas concentration formed from merging can thus show steeply rising rotation curves in their central regions. Such gas concentration is also responsible for central starbursts of BCDs and the high central surface brightness and is consistent with previous BCD studies. We discuss the relationship between rotational velocity gradient and surface brightness, the dependence of BCD rotation curves on star formation threshold density, progenitor initial profile, interaction type and merger mass ratio, as well as potential evolutionary links between dwarf irregulars, BCDs and compact dwarf irregulars.

[13]  arXiv:1607.06869 [pdf, other]
Title: Fragmentation of protoplanetary disks around M-dwarfs
Comments: 18 pages, 15 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We investigate the conditions required for planet formation via gravitational instability (GI) and protoplanetary disk (PPD) fragmentation around M-dwarfs. Using a suite of 64 SPH simulations with $10^6$ particles, the parameter space of disk mass, temperature, and radius is explored, bracketing reasonable values based on theory and observation. Our model consists of an equilibrium, gaseous, and locally isothermal disk orbiting a central star of mass $M_*=M_{sol}/3$. Disks with a minimum Toomre $Q$ of $Q_{min} \lesssim 0.9$ will fragment and form gravitationally bound clumps. Some previous literature has found $Q_{min} < 1.3-1.5$ to be sufficient for fragmentation. Increasing disk height tends to stabilize disks, and when incorporated into $Q$ as $Q_{eff}\propto Q(H/R)^\alpha$ for $\alpha=0.18$ is sufficient to predict fragmentation. Some discrepancies in the literature regarding $Q_{crit}$ may be due to different methods of generating initial conditions (ICs). A series of 15 simulations demonstrates that perturbing ICs slightly out of equilibrium can cause disks to fragment for higher $Q$. Our method for generating ICs is presented in detail. We argue that GI likely plays a role in PPDs around M-dwarfs and that disk fragmentation at large radii is a plausible outcome for these disks.

[14]  arXiv:1607.06874 [pdf, other]
Title: Polarized Scattering and Biosignatures in Exoplanetary Atmospheres
Authors: S.V. Berdyugina
Comments: JQSRT, accepted, 12 pages
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (

Polarized scattering in planetary atmospheres is computed in the context of exoplanets. The problem of polarized radiative transfer is solved for a general case of absorption and scattering, while Rayleigh and Mie polarized scattering are considered as most relevant examples. We show that (1) relative contributions of single and multiple scattering depend on the stellar irradiation and opacities in the planetary atmosphere; (2) cloud (particle) physical parameters can be deduced from the wavelength-dependent measurements of the continuum polarization and from a differential analysis of molecular band absorption; (3) polarized scattering in molecular bands increases the reliability of their detections in exoplanets; (4) photosynthetic life can be detected on other planets in visible polarized spectra with high sensitivity. These examples demonstrate the power of spectropolarimetry for exoplanetary research and for searching for life in the universe.

[15]  arXiv:1607.06892 [pdf, other]
Title: MASSIVE: A Bayesian analysis of giant planet populations around low-mass stars
Comments: Accepted for publication on A&A, 23 pages, 10 figures, 13 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Direct imaging has led to the discovery of several giant planet and brown dwarf companions. These imaged companions populate a mass, separation and age domain (mass>1MJup, orbits>5AU, age<1Gyr) quite distinct from the one occupied by exoplanets discovered by the radial velocity or transit methods. This distinction could pinpoint that different formation mechanisms are at play. We aim at investigating correlations between the host star's mass and the presence of wide-orbit giant planets, and at providing new observational constraints on planetary formation models. We observed 58 young and nearby M-type dwarfs in L'-band with the VLT/NaCo instrument and used ADI algorithms to optimize the sensitivity to planetary-mass companions and to derive the best detection limits. We estimate the probability of detecting a planet as a function of its mass and physical separation around each target. We conduct a Bayesian analysis to determine the frequency of substellar companions orbiting low-mass stars, using a homogenous sub-sample of 54 stars. We derive a frequency of $4.4^{+3.2}_{-1.3}\%$ for companions with masses in the range of 2-80MJup}, and $2.3^{+2.9}_{-0.7}$\% for planetary mass companions (2-14MJup), at physical separations of 8 to 400AU for both cases. Comparing our results with a previous survey targeting more massive stars, we find evidence that substellar companions more massive than 1MJup with a low mass ratio Q with respect to their host star (Q<1%), are less frequent around low-mass stars. This may represent an observational evidence that the frequency of imaged wide-orbit substellar companions is correlated with stellar mass, corroborating theoretical expectations. On the opposite, we show statistical evidence that intermediate-mass ratio (1%<Q<5%) companion with masses >2MJup might be independent from the mass of the host star.

[16]  arXiv:1607.06916 [pdf, other]
Title: General features of single-scalar field dark energy models
Authors: Louis Perenon
Comments: Proceedings of 51st Rencontres de Moriond
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a systematic study of modified gravity (MG) models containing a single scalar field non-minimally coupled to the metric. Despite a large parameter space, exploiting the effective field theory of dark energy (EFT of DE) formulation and imposing simple physical constraints such as stability conditions and (sub-)luminal propagation of perturbations, we arrive at a number of generic predictions about the large scale structures.

[17]  arXiv:1607.06930 [pdf, other]
Title: Photometric, Spectroscopic and Orbital Period Study of Three Early Type Semi-detached Systems: XZ Aql, UX Her and AT Peg
Comments: 40 pages, 16 figures
Journal-ref: 2016, AJ, 152, 33
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In this paper we present a combined photometric, spectroscopic and orbital period study of three early-type eclipsing binary systems: XZ Aql, UX Her, and AT Peg. As a result, we have derived the absolute parameters of their components and, on that basis, we discuss their evolutionary states. Furthermore, we compare their parameters with those of other binary systems and with the theoretical models. An analysis of all available up-to-date times of minima indicated that all three systems studied here show cyclic orbital changes, their origin is discussed in detail. Finally, we performed a frequency analysis for possible pulsational behavior and as a result we suggest that XZ Aql hosts a {\delta} Scuti component.

[18]  arXiv:1607.06937 [pdf, ps, other]
Title: Optical Spectroscopy of Four Young Radio Sources
Comments: 11 pages, 5 Figures, 2 Tables, accepted by New Astronomy
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report the optical spectroscopy of four young radio sources which are observed with the Lijiang 2.4m telescope. The Eddington ratios of these sources are similar with those of narrow-line Seyfert 1 galaxies (NLS1s). Their Fe {\sc ii} emission is strong while [O {\sc iii}] strength is weak. These results confirm the NLS1 features of young radio sources, except that the width of broad H$\beta$ of young radio sources is larger than that of NLS1s. We thus suggest that the young radio sources are the high black hole mass counterparts of steep-spectrum radio-loud NLS1s. In addition, the broad H$\beta$ component of \astrobj{4C 12.50} is the blue wing of the narrow component, but not from the broad line region.

[19]  arXiv:1607.06949 [pdf]
Title: The ERIS Adaptive Optics System
Comments: 11 pages, 11 figures, 1 table. SPIE conference Astronomical Telescopes and Instrumentation, 26 June - 01 July 2016, Edinburgh, Scotland, United Kingdom
Journal-ref: Proc. SPIE Vol. 9909 (2016)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

ERIS is the new AO instrument for VLT-UT4 led by a Consortium of Max-Planck Institut fuer Extraterrestrische Physik, UK-ATC, ETH-Zurich, ESO and INAF. The ERIS AO system provides NGS mode to deliver high contrast correction and LGS mode to extend high Strehl performance to large sky coverage. The AO module includes NGS and LGS wavefront sensors and, with VLT-AOF Deformable Secondary Mirror and Laser Facility, will provide AO correction to the high resolution imager NIX (1-5um) and the IFU spectrograph SPIFFIER (1-2.5um). In this paper we present the preliminary design of the ERIS AO system and the estimated correction performance.

[20]  arXiv:1607.06957 [pdf, other]
Title: Quasi-Periodic Pulsations during the Impulsive and Decay phases of an X-class Flare
Comments: 7 pages, 4 figures, 1 table
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Quasi-periodic pulsations (QPP) are often observed in X-ray emission from solar flares. To date, it is unclear what their physical origins are. Here, we present a multi-instrument investigation of the nature of QPP during the impulsive and decay phases of the X1.0 flare of 28 October 2013. We focus on the character of the fine structure pulsations evident in the soft X-ray time derivatives and compare this variability with structure across multiple wavelengths including hard X-ray and microwave emission. We find that during the impulsive phase of the flare, high correlations between pulsations in the thermal and non-thermal emissions are seen. A characteristic timescale of ~20s is observed in all channels and a second timescale of ~55s is observed in the non-thermal emissions. Soft X-ray pulsations are seen to persist into the decay phase of this flare, up to 20 minutes after the non-thermal emission has ceased. We find that these decay phase thermal pulsations have very small amplitude and show an increase in characteristic timescale from ~40s up to ~70s. We interpret the bursty nature of the co-existing multi-wavelength QPP during the impulsive phase in terms of episodic particle acceleration and plasma heating. The persistent thermal decay phase QPP are most likely connected with compressive MHD processes in the post-flare loops such as the fast sausage mode or the vertical kink mode.

[21]  arXiv:1607.06970 [pdf, other]
Title: OSSOS: IV. Discovery of a dwarf planet candidate in the 9:2 resonance
Comments: 10 pp, 4 figures; submitted to AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We report the discovery and orbit of a new dwarf planet candidate, 2015 RR$_{245}$, by the Outer Solar System Origins Survey (OSSOS). 2015 RR$_{245}$'s orbit is eccentric ($e=0.586$), with a semi-major axis near 82 au, yielding a perihelion distance of 34 au. 2015 RR$_{245}$ has $g-r = 0.59 \pm 0.11$ and absolute magnitude $H_{r} = 3.6 \pm 0.1$; for an assumed albedo of $p_V = 12$% the object has a diameter of $\sim670$ km. Based on astrometric measurements from OSSOS and Pan-STARRS1, we find that 2015 RR$_{245}$ is securely trapped in the 9:2 mean-motion resonance with Neptune. It is the first TNO identified in this resonance. On hundred-Myr timescales, particles in 2015 RR$_{245}$-like orbits depart and sometimes return to the resonance, indicating that 2015 RR$_{245}$ likely forms part of the long-lived metastable population of distant TNOs that drift between resonance sticking and actively scattering via gravitational encounters with Neptune. The discovery of a 9:2 TNO stresses the role of resonances in the long-term evolution of objects in the scattering disk, and reinforces the view that distant resonances are heavily populated in the current Solar System. This object further motivates detailed modelling of the transient sticking population.

[22]  arXiv:1607.06981 [pdf]
Title: The masses of neutron stars
Comments: 12 pp., 3 figures, Chapter of forthcoming Handbook of Supernovae, edited by Athem W. Alsabti and Paul Murdin
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We present in this article an overview of the problem of neutron star masses. After a brief appraisal of the methods employed to determine the masses of neutron stars in binary systems, the existing sample of measured masses is presented, with a highlight on some very well-determined cases. We discuss the analysis made to uncover the underlying distribution and a few robust results that stand out from them. The issues related to some particular groups of neutron stars originated from different channels of stellar evolution are shown. Our conclusions are that last century's paradigm that there a single, $1.4 M_{\odot}$ scale is too simple. A bimodal or even more complex distribution is actually present. It is confirmed that some neutron stars have masses of $\sim 2 M_{\odot}$, and, while there is still no firm conclusion on the maximum and minimum values produced in nature, the field has entered a mature stage in which all these and related questions can soon be given an answer.

[23]  arXiv:1607.07001 [pdf, other]
Title: First Simultaneous Views of the Axial and Lateral Perspectives of a Coronal Mass Ejection
Comments: 21 pages, 11 figures, Solar Physics, Online First (07/2016)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The different appearances exhibited by coronal mass ejections (CMEs) are believed to be in part the result of different orientations of their main axis of symmetry, consistent with a flux-rope configuration. There are observational reports of CMEs seen along their main axis (axial perspective) and perpendicular to it (lateral perspective), but no simultaneous observations of both perspectives from the same CME have been reported to date. The stereoscopic views of the telescopes onboard the $Solar$-$Terrestrial$ $Relations$ $Observatory$ (STEREO) twin spacecraft, in combination with the views from the $Solar$ $and$ $Heliospheric$ $Observatory$ (SOHO) and the $Solar$ $Dynamics$ $Observatory$ (SDO), allow us to study the axial and lateral perspectives of a CME simultaneously for the first time. In addition, this study shows that the lateral angular extent ($L$) increases linearly with time, while the angular extent of the axial perspective ($D$) presents this behavior only from the low corona to $\approx\,$5 $R_{\odot}$, where it slows down. The ratio $L/D \approx\,$1.6 obtained here as the average over several points in time is consistent with measurements of $L$ and $D$ previously performed on events exhibiting only one of the perspectives from the single vantage point provided by SOHO.

[24]  arXiv:1607.07004 [pdf, ps, other]
Title: Near infrared spectroscopy of M dwarfs. IV. A preliminary survey on the carbon isotopic ratios in M dwarfs
Authors: Takashi Tsuji
Comments: 19 pages, 6 figures, 5 tables, accepted by PASJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Based on the medium resolution near infrared spectra of 13CO (3,1) band, carbon isotopic ratios are estimated in 48 M dwarfs, for which we had determined the carbon and oxygen abundances from CO and H2O lines, respectively. We find clear evidence for the presence of a 13CO feature for the first time in the spectra of M dwarfs. The spectral resolution of our observed data, however, is not high enough to analyze the 13CO feature directly. Instead, we compare observed spectrum with synthetic spectra assuming 12C/13C = 10, 25, 50, 100, and 200 for each of 48 M dwarfs and estimate the best possible 12C/13C ratio by the chi-square analysis. The resulting 12C/13C ratios in M dwarfs distribute from 39 to a lower limit of 200. The mean value of 31 M dwarfs for which 12C/13C ratios are determined is 12C/13C = 87 +- 21 (p.e.), and that of 48 M dwarfs including those with the lower limit of 200 is 12C/13C > 127 +- 41 (p.e.). These results are somewhat larger than the 12C/13C ratio of the present interstellar matter (ISM) determined from the molecular lines observed in the millimeter and optical wavelength regions. Since the amount of 13C in the ISM has increased with time due to mass-loss from evolved stars, the 12C/13C ratios in M dwarfs, reflecting those of the past ISM, should be larger than those of the present ISM. In M dwarfs, log 13C/12C plotted against log Ac shows a large scatter without clear dependence on the metallicity. This result shows a marked contrast to log 16O/12C (= log Ao/Ac) plotted against log Ac, which shows a rather tight correlation with the larger value at the lower metallicity. Such a contrast can be a natural consequence that 16O and 12C are the primary products in the stellar nuclear synthesis while 13C is the secondary product, at least partly.

[25]  arXiv:1607.07037 [pdf]
Title: The Earth-Moon system as a typical binary in the Solar System
Authors: S. I. Ipatov
Comments: The paper in SPACEKAZAN-IAPS-2015, ed. by. M.Ya. Marov, Kazan, Publishing house of Kazan University, pp. 97-105 (2015). The international astronomical conference SPACEKAZAN-IAPS-2015 has been held on June 1-7, 2015 in Kazan, Russia. In the attached file, a font size, a page size, and a line spacing are different from those in the proceedings, and so the number of pages is different
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Solid embryos of the Earth and the Moon, as well as trans-Neptunian binaries, could form as a result of contraction of the rarefied condensation which was parental for a binary. The angular momentum of the condensation needed for formation of a satellite system could be mainly acquired at the collision of two rarefied condensations at which the parental condensation formed. The minimum value of the mass of the parental condensation for the Earth-Moon system could be about 0.02 of the Earth mass. Besides the main collision, which was followed by formation of the condensation that was a parent for the embryos of the Earth and the Moon, there could be another main collision of the parental condensation with another condensation. The second main collision (or a series of similar collisions) could change the tilt of the Earth. Depending on eccentricities of the planetesimals that collided with the embryos, the Moon could acquire 0.04-0.3 of its mass at the stage of accumulation of solid bodies while the mass of the growing Earth increased by a factor of ten.

[26]  arXiv:1607.07046 [pdf, ps, other]
Title: Effect of spectral index distribution on estimating the AGN radio luminosity function
Comments: 8 pages, 4 figures, Accepted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

In this paper, we scrutinize the effect of spectral index distribution on estimating the AGN (active galactic nucleus) radio luminosity function (RLF) by a Monte Carlo method. We find that the traditional bivariate RLF estimators can cause bias in varying degree. The bias is especially pronounced for the flat-spectrum radio sources whose spectral index distribution is more scattered. We believe that the bias is caused because the $K$-corrections complicate the truncation boundary on the $L-z$ plane of the sample, but the traditional bivariate RLF estimators have difficulty in dealing with this boundary condition properly. We suggest that the spectral index distribution should be incorporated into the RLF analysis process to obtain a robust estimation. This drives the need for a trivariate function of the form $\Phi(\alpha,z,L)$ which we show provides an accurate basis for measuring the RLF.

[27]  arXiv:1607.07049 [pdf, ps, other]
Title: Local Stellar Kinematics from RAVE data - VII. Metallicity Gradients from Red Clump Stars
Comments: 18 pages, including 16 figures and 6 tables, accepted for publication in PASA
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We investigate the Milky Way Galaxy's radial and vertical metallicity gradients using a sample of 47,406 red clump stars from the RAVE DR4. This sample is more than twice the size of the largest sample in the literature investigating radial and vertical metallicity gradients. The absolute magnitude of Groenewegen (2008) is used to determine distances to our sample stars. The resulting distances agree with the RAVE DR4 distances Binney et al. (2014) of the same stars. Our photometric method also provides distances to 6185 stars that are not assigned a distance in RAVE DR4. The metallicity gradients are calculated with their current orbital positions ($R_{gc}$ and $Z$) and with their orbital properties (mean Galactocentric distance, $R_{m}$ and $z_{max}$), as a function of the distance to the Galactic plane: d[Fe/H]/d$R_{gc}=$-$0.047\pm0.003$ dex/kpc for $0\leq |Z|\leq0.5$ kpc and d[Fe/H]/d$R_m=$-$0.025\pm0.002$ dex/kpc for $0\leq z_{max}\leq0.5$ kpc. This reaffirms the radial metallicity gradient in the thin disc but highlights that gradients are sensitive to the selection effects caused by the difference between $R_{gc}$ and $R_{m}$. The radial gradient is flat in the distance interval 0.5-1 kpc from the plane and then becomes positive greater than 1 kpc from the plane. The radial metallicity gradients are also eccentricity dependent. We showed that d[Fe/H]/d$R_m=$-$0.089\pm0.010$, -$0.073\pm0.007$, -$0.053\pm0.004$ and -$0.044\pm0.002$ dex/kpc for $e_p\leq0.05$, $e_p\leq0.07$, $e_p\leq0.10$ and $e_p\leq0.20$ sub-samples, respectively, in the distance interval $0\leq z_{max}\leq0.5$ kpc. Similar trend is found for vertical metallicity gradients. Both the radial and vertical metallicity gradients are found to become shallower as the eccentricity of the sample increases. These findings can be used to constrain different formation scenarios of the thick and thin discs.

[28]  arXiv:1607.07058 [pdf, other]
Title: Hubble induced mass after inflation in spectator field models
Comments: 19 pages, 5 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

Spectator field models such as the curvaton scenario and the modulated reheating are attractive scenarios for the generation of the cosmic curvature perturbation, as the constraints on inflation models are relaxed. In this paper, we discuss the effect of Hubble induced masses on the dynamics of spectator fields after inflation. We pay particular attention to the Hubble induced mass by the kinetic energy of an oscillating inflaton, which is generically unsuppressed but often overlooked. In the curvaton scenario, the Hubble induced mass relaxes the constraint on the property of the inflaton and the curvaton, such as the reheating temperature and the inflation scale. We comment on the implication of our discussion for baryogenesis in the curvaton scenario. In the modulated reheating, the predictions of models e.g. the non-gaussianity can be considerably altered. Furthermore, we propose a new model of the modulated reheating utilizing the Hubble induced mass which realizes a wide range of the local non-gaussianity parameter.

[29]  arXiv:1607.07094 [pdf, other]
Title: Active region fine structure observed at 0.08 arcsec resolution
Comments: 11 pages, accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The various mechanisms of magneto-convective energy transport determines the structure of sunspots and active regions. We characterise the appearance of light bridges and other fine structure details and elaborate on their magneto-convective nature. We present speckle-reconstructed images taken with the broad band imager at the 1.5 m GREGOR telescope in the 486nm and 589nm bands. We estimate the spatial resolution from the noise characteristics of the image bursts and obtain 0.08'' at 589nm. We describe structure details in individual best images as well as the temporal evolution of selected features. We find branched dark lanes extending along thin (~1'') light bridges in sunspots at various heliocentric angles. In thick (~2'') light bridges the branches are disconnected from the central lane and have a `Y' shape with a bright grain toward the umbra. The images reveal that light bridges exist on varying intensity levels and that their small-scale features evolve on time scales of minutes. Faint light bridges show dark lanes outlined by the surrounding bright features. Dark lanes are very common and also found in the boundary of pores. They have a characteristic width of 0.1'' or less. Intergranular dark lanes of that width are seen in active region granulation. While central dark lanes in thin light bridges are elevated and associated with an density increase above upflows, the dark lane branches correspond to locations of downflows and are depressed relative to the adjacent bright plasma. Thick light bridges with central dark lanes show no projection effect. They have a flat elevated plateau that falls off steeply at the umbral boundary. There, `Y' shaped filaments form like in the inner penumbra. This indicates the presence of inclined magnetic fields, i.e., that the umbral magnetic field wraps around the convective light bridge.

[30]  arXiv:1607.07125 [pdf, ps, other]
Title: No Signatures of Black-Hole Spin in the X-ray Spectrum of the Seyfert 1 Galaxy Fairall 9
Comments: 21 pages, 2 tables, 6 figures, accepted by MNRAS. arXiv admin note: text overlap with arXiv:1508.07685
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Fairall 9 is one of several type 1 active galactic nuclei for which it has been claimed that the angular momentum (or spin) of the supermassive black hole can be robustly measured, using the Fe K$\alpha$ emission line and Compton-reflection continuum in the X-ray spectrum. The method rests upon the interpretation of the Fe K$\alpha$ line profile and associated Compton-reflection continuum in terms of relativistic broadening in the strong gravity regime in the innermost regions of an accretion disc, within a few gravitational radii of the black hole. Here, we re-examine a Suzaku X-ray spectrum of Fairall 9 and show that a face-on toroidal X-ray reprocessor model involving only nonrelativistic and mundane physics provides an excellent fit to the data. The Fe K$\alpha$ line emission and Compton reflection continuum are calculated self-consistently, the iron abundance is solar, and an equatorial column density of $\sim 10^{24} \ \rm cm^{-2}$ is inferred. In this scenario, neither the Fe K$\alpha$ line, nor the Compton-reflection continuum provide any information on the black-hole spin. Whereas previous analyses have assumed an infinite column density for the distant-matter reprocessor, the shape of the reflection spectrum from matter with a finite column density eliminates the need for a relativistically broadened Fe K$\alpha$ line. We find a 90 per cent confidence range in the Fe K$\alpha$ line FWHM of $1895$-$6205 \ \rm km \ s^{-1}$, corresponding to a distance of $\sim 3100$ to $33,380$ gravitational radii from the black hole, or $0.015$-$0.49$ pc for a black-hole mass of $\sim 1-3 \times 10^{8} \ M_{\odot}$.

[31]  arXiv:1607.07140 [pdf, other]
Title: Impact of Baryonic Physics on Intrinsic Alignments
Comments: 7 pages, 6 figures, submitted to ApJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We explore the effects of specific assumptions in the subgrid models of star formation and stellar and AGN feedback on intrinsic alignments of galaxies in cosmological simulations of "MassiveBlack-II" family. Using smaller volume simulations, we explored the parameter space of the subgrid star formation and feedback model and found remarkable robustness of the observable statistical measures to the details of subgrid physics. The one observational probe most sensitive to modeling details is the distribution of misalignment angles. We hypothesize that the amount of angular momentum carried away by the galactic wind is the primary physical quantity that controls the orientation of the stellar distribution. Our results are also consistent with a similar study by the EAGLE simulation team.

[32]  arXiv:1607.07166 [pdf, other]
Title: Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization
Comments: 14 pages, 11 figures, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The dynamical impact of Lyman-alpha (Ly{\alpha}) radiation pressure on galaxy formation depends on the rate and duration of momentum transfer between Ly{\alpha} photons and neutral hydrogen gas. Although photon trapping has the potential to multiply the effective force, ionizing radiation from stellar sources may relieve the Ly{\alpha} pressure before appreciably affecting the kinematics of the host galaxy or efficiently coupling Ly{\alpha} photons to the outflow. We present self-consistent Ly{\alpha} radiation-hydrodynamics simulations of high-$z$ galaxy environments by coupling the Cosmic Ly{\alpha} Transfer code (COLT) with spherically symmetric Lagrangian frame hydrodynamics. The accurate but computationally expensive Monte-Carlo radiative transfer calculations are feasible under the one-dimensional approximation. In certain cases Ly{\alpha} feedback significantly enhances the velocity of the shell of gas expanding around a central source. Radiative feedback alone is capable of ejecting baryons into the intergalactic medium (IGM) for protogalaxies with a virial mass of $M_{\rm vir} \lesssim 10^8~{\rm M}_\odot$. We compare the Ly{\alpha} signatures of Population III stars with $10^5$ K blackbody emission to that of direct collapse black holes with a nonthermal Compton-thick spectrum and find substantial differences. For both sources, the flux emerging from the galaxy is reprocessed by the IGM such that the observed Ly{\alpha} luminosity is reduced significantly and the time-averaged velocity offset of the Ly{\alpha} peak is shifted redward.

[33]  arXiv:1607.07190 [pdf, ps, other]
Title: Oxygen abundance maps of CALIFA galaxies
Comments: 20 pages, 12 figures; Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We construct maps of the oxygen abundance distribution across the disks of 88 galaxies using CALIFA data release 2 (DR2) spectra. The position of the center of a galaxy (coordinates on the plate) were also taken from the CALIFA DR2. The galaxy inclination, the position angle of the major axis, and the optical radius were determined from the analysis of the surface brightnesses in the SDSS $g$ and $r$ bands of the photometric maps of SDSS data release 9. We explore the global azimuthal abundance asymmetry in the disks of the CALIFA galaxies and the presence of a break in the radial oxygen abundance distribution. We found that there is no significant global azimuthal asymmetry for our sample of galaxies, i.e., the asymmetry is small, usually lower than 0.05 dex. The scatter in oxygen abundances around the abundance gradient has a comparable value, $\lesssim 0.05$ dex. A significant (possibly dominant) fraction of the asymmetry can be attributed to the uncertainties in the geometrical parameters of these galaxies. There is evidence for a flattening of the radial abundance gradient in the central part of 18 galaxies. We also estimated the geometric parameters (coordinates of the center, the galaxy inclination and the position angle of the major axis) of our galaxies from the analysis of the abundance map. The photometry-map-based and the abundance-map-based geometrical parameters are relatively close to each other for the majority of the galaxies but the discrepancy is large for a few galaxies with a flat radial abundance gradient.

[34]  arXiv:1607.07198 [pdf]
Title: Collimating Slicer for Optical Integral Field Spectroscopy
Comments: 13 pages
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Optics (physics.optics)

Integral Field Spectroscopy (IFS) is a technique that gives simultaneously the spectrum of each spatial sampling element in a given object field. It is a powerful tool which rearranges the data cube (x, y, lambda) represented by two spatial dimensions defining the field and the spectral decomposition in a detector plane. In IFS, the spatial unit reorganizes the field and the spectral unit is being composed of a classical spectrograph.The development of a Collimating Slicer aims at proposing a new type of integral field spectrograph which should be more compact. The main idea is to combine the image slicer with the collimator of the spectrograph, thus mixing the spatial and spectral units. The traditional combination of slicer, pupil and slit elements and the spectrograph collimator is replaced by a new one composed of a slicer and collimator only. In this paper, the state of the art of integral field spectroscopy using image slicers is described. The new system based onto the development of a Collimating Slicer for optical integral field spectroscopy is depicted. First system analysis results and future improvements are discussed. It finally turns out that this new system looks very promising for low resolution spectroscopy.

[35]  arXiv:1607.07206 [pdf, ps, other]
Title: Time-dependent shock acceleration of particles. Effect of the time-dependent injection, with application to supernova remnants
Comments: MNRAS, accepted
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Three approaches are considered to solve the equation which describes the time-dependent diffusive shock acceleration of test particles at the non-relativistic shocks. At first, the solution of Drury (1983) for the particle distribution function at the shock is generalized to any relation between the acceleration time-scales upstream and downstream and for the time-dependent injection efficiency. Three alternative solutions for the spatial dependence of the distribution function are derived. Then, the two other approaches to solve the time-dependent equation are presented, one of which does not require the Laplace transform. At the end, our more general solution is discussed, with a particular attention to the time-dependent injection in supernova remnants. It is shown that, comparing to the case with the dominant upstream acceleration time-scale, the maximum momentum of accelerated particles shifts toward the smaller momenta with increase of the downstream acceleration time-scale. The time-dependent injection affects the shape of the particle spectrum. In particular, i) the power-law index is not solely determined by the shock compression, in contrast to the stationary solution; ii) the larger the injection efficiency during the first decades after the supernova explosion, the harder the particle spectrum around the high-energy cutoff at the later times. This is important, in particular, for interpretation of the radio and gamma-ray observations of supernova remnants, as demonstrated on a number of examples.

[36]  arXiv:1607.07226 [pdf, ps, other]
Title: Uncertainty Limits on Solutions of Inverse Problems over Multiple Orders of Magnitude using Bootstrap Methods: An Astroparticle Physics Example
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (

Astroparticle experiments such as IceCube or MAGIC require a deconvolution of their measured data with respect to the response function of the detector to provide the distributions of interest, e.g. energy spectra. In this paper, appropriate uncertainty limits that also allow to draw conclusions on the geometric shape of the underlying distribution are determined using bootstrap methods, which are frequently applied in statistical applications. Bootstrap is a collective term for resampling methods that can be employed to approximate unknown probability distributions or features thereof. A clear advantage of bootstrap methods is their wide range of applicability. For instance, they yield reliable results, even if the usual normality assumption is violated.
The use, meaning and construction of uncertainty limits to any user-specific confidence level in the form of confidence intervals and levels are discussed. The precise algorithms for the implementation of these methods, applicable for any deconvolution algorithm, are given. The proposed methods are applied to Monte Carlo simulations to show their feasibility and their precision in comparison to the statistical uncertainties calculated with the deconvolution software TRUEE.

[37]  arXiv:1607.07227 [pdf, other]
Title: Training telescope operators and support astronomers at Paranal
Comments: Paper 9910-123 presented at SPIE 2016
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Physics Education (physics.ed-ph)

The operations model of the Paranal Observatory relies on the work of efficient staff to carry out all the daytime and nighttime tasks. This is highly dependent on adequate training. The Paranal Science Operations department (PSO) has a training group that devises a well-defined and continuously evolving training plan for new staff, in addition to broadening and reinforcing courses for the whole department. This paper presents the training activities for and by PSO, including recent astronomical and quality control training for operators, as well as adaptive optics and interferometry training of all staff. We also present some future plans.

[38]  arXiv:1607.07231 [pdf, other]
Title: An interferometric view of binary stars
Comments: Paper 9907-135 presented at SPIE 2016
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The study of binary stars is critical to apprehend many of the most interesting classes of stars. Moreover, quite often, the study of stars in binary systems is our only mean to constrain stellar properties, such as masses and radii. Unfortunately, a great fraction of the most interesting binaries are so compact that they can only be apprehended by high-resolution techniques, mostly by interferometry. I present some results highlighting the use of interferometry in the study of binary stars, from finding companions and deriving orbits, determining the mass and radius of stars, to studying mass transfer in symbiotic stars, and tackling luminous blue variables. In particular, I show how interferometric studies using the PIONIER instrument have allowed us to confirm a dichotomy within symbiotic stars, obtain masses of stars with a precision better than 1%, and help us find a new Eta Carinae-like system. I will also illustrate the benefits for the study of binary stars one would get from upgrading the VLT Interferometer so as to be able to observe in the visible range.

[39]  arXiv:1607.07237 [pdf, other]
Title: Regaining the FORS: making optical ground-based transmission spectroscopy of exoplanets with VLT+FORS2 possible again
Comments: Paper 9908-85 presented at SPIE 2016
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Detectors (physics.ins-det)

Transmission spectroscopy facilitates the detection of molecules and/or clouds in the atmospheres of exoplanets. Such studies rely heavily on space-based or large ground-based observatories, as one needs to perform time- resolved, high signal-to-noise spectroscopy. The FORS2 instrument at ESO's Very Large Telescope is the obvious choice for performing such studies, and was indeed pioneering the field in 2010. After that, however, it was shown to suffer from systematic errors caused by the Longitudinal Atmospheric Dispersion Corrector (LADC). This was successfully addressed, leading to a renewed interest for this instrument as shown by the number of proposals submitted to perform transmission spectroscopy of exoplanets. We present here the context, the problem and how we solved it, as well as the recent results obtained. We finish by providing tips for an optimum strategy to do transmission spectroscopy with FORS2, in the hope that FORS2 may become the instrument of choice for ground-based transmission spectroscopy of exoplanets.

[40]  arXiv:1607.07245 [pdf, other]
Title: A GMRT survey of regions towards the Taurus Molecular Cloud at 323 and 608 MHz
Comments: Accepted for publication in MNRAS; data products, full catalogue and the manuscript with high-res versions of the figures can be found on the project website: this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

We present observations of three active sites of star formation in the Taurus Molecular Cloud complex taken at 323 and 608 MHz (90 and 50 cm, respectively) with the Giant Metrewave Radio Telescope (GMRT). Three pointings were observed as part of a pathfinder project, targeted at the young stellar objects (YSOs) L1551 IRS 5, T Tau and DG Tau (the results for these target sources were presented in a previous paper). In this paper, we search for other YSOs and present a survey comprising of all three fields; a by-product of the large instantaneous field of view of the GMRT. The resolution of the survey is of order 10 arcsec and the best rms noise at the centre of each pointing is of order $100\,\mu$Jy beam$^{-1}$ at 323 MHz and $50\,\mu$Jy beam$^{-1}$ at 608 MHz. We present a catalogue of 1815 and 687 field sources detected above $5\,\sigma_{\rm rms}$ at 323 and 608 MHz, respectively. A total of 440 sources were detected at both frequencies, corresponding to a total unique source count of 2062 sources. We compare the results with previous surveys and showcase a sample of extended extragalactic objects. Although no further YSOs were detected in addition to the target YSOs based on our source finding criteria, these data can be useful for targeted manual searches, studies of radio galaxies or to assist in the calibration of future observations with the Low Frequency Array (LOFAR) towards these regions.

[41]  arXiv:1607.07246 [pdf, ps, other]
Title: Dynamics of Saturn's great storm of 2010-2011 from Cassini ISS and RPWS
Comments: 17 figures
Journal-ref: Icarus 223 (2013) 460-478
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Saturn's quasi-periodic planet-encircling storms are the largest convecting outbursts in the Solar System. The last eruption was in 1990. A new eruption started in December 2010 and presented the first-ever opportunity to observe such episodic storms from a spacecraft in orbit around Saturn. Here, we analyze images acquired with the Cassini Imaging Science Subsystem (ISS), which captured the storm's birth, evolution and demise. In studying the end of the convective activity, we also analyze the Saturn Electrostatic Discharge (SED) signals detected by the Radio and Plasma Wave Science (RPWS) instrument. [...]

[42]  arXiv:1607.07248 [pdf, other]
Title: Long-term observations of the pulsars in 47 Tucanae. I. A study of four elusive binary systems
Comments: Accepted for publication by MNRAS, 18 pages, 11 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

For the past couple of decades, the Parkes radio telescope has been regularly observing the millisecond pulsars in 47 Tucanae (47 Tuc). This long-term timing program was designed to address a wide range of scientific issues related to these pulsars and the globular cluster where they are located. In this paper, the first of a series, we address one of these objectives: the characterization of four previously known binary pulsars for which no precise orbital parameters were known, namely 47 Tuc P, V, W and X (pulsars 47 Tuc R and Y are discussed elsewhere). We determined the previously unknown orbital parameters of 47 Tuc V and X and greatly improved those of 47 Tuc P and W. For pulsars W and X we obtained, for the first time, full coherent timing solutions across the whole data span, which allowed a much more detailed characterization of these systems. 47 Tuc W, a well-known tight eclipsing binary pulsar, exhibits a large orbital period variability, as expected for a system of its class. 47 Tuc X turns out to be in a wide, extremely circular, 10.9-day long binary orbit and its position is ~3.8 arcmin away from the cluster center, more than three times the distance of any other pulsar in 47 Tuc. These characteristics make 47 Tuc X a very different object with respect to the other pulsars of the cluster.

[43]  arXiv:1607.07257 [pdf]
Title: Olivine on Vesta as exogenous contaminants brought by impacts: Constraints from modeling Vesta's collisional history and from impact simulations
Comments: 24 pages, 6 figures, accepted for publication on the journal Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The survival of asteroid Vesta during the violent early history of the Solar System is a pivotal constraint on theories of planetary formation. Particularly important from this perspective is the amount of olivine excavated from the vestan mantle by impacts, as this constrains both the interior structure of Vesta and the number of major impacts the asteroid suffered during its life. The NASA Dawn mission revealed that olivine is present on Vesta's surface in limited quantities, concentrated in small patches at a handful of sites and interpreted as the result of the excavation of endogenous olivine. Later works raised the possibility that the olivine had an exogenous origin, based on the geologic and spectral features of the deposits. In this work we quantitatively explore the proposed scenario of a exogenous origin for the detected olivine to investigate whether its presence on Vesta can be explained as a natural outcome of the collisional history of the asteroid. We took advantage of the impact contamination model previously developed to study the origin and amount of dark and hydrated materials observed by Dawn on Vesta, which we updated by performing dedicated hydrocode impact simulations. We show that the exogenous delivery of olivine by impacts can offer a viable explanation for the currently identified olivine-rich sites without violating the constraint posed by the lack of global olivine signatures on Vesta. Our results indicate that no mantle excavation is in principle required to explain the observations of the Dawn mission and support the idea that the vestan crust could be thicker than indicated by simple geochemical models based on the Howardite-Eucrite-Diogenite family of meteorites.

[44]  arXiv:1607.07258 [pdf, ps, other]
Title: The small observed scale of AGN--driven outflows, and inside--out disc quenching
Comments: 13 pages, 14 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Observations of massive outflows with detectable central AGN typically find them within radii $\lesssim 10$ kpc. We show that this apparent size restriction is a natural result of AGN driving if this process injects total energy only of order the gas binding energy to the outflow, and the AGN varies over time (`flickers') as suggested in recent work. After the end of all AGN activity the outflow continues to expand to larger radii, powered by the thermal expansion of the remnant shocked AGN wind. We suggest that on average, outflows should be detected further from the nucleus in more massive galaxies. In massive gas--rich galaxies these could be several tens of kpc in radius. We also consider the effect that pressure of such outflows has on a galaxy disc. In moderately gas--rich discs, with gas-to-baryon fraction $< 0.2$, the outflow may induce star formation significant enough to be distinguished from quiescent by an apparently different normalisation of the Kennicutt-Schmidt law. The star formation enhancement is probably stronger in the outskirts of galaxy discs, so coasting outflows might be detected by their effects upon the disc even after the driving AGN has shut off. We compare our results to the recent inference of inside--out quenching of star formation in galaxy discs.

[45]  arXiv:1607.07296 [pdf, ps, other]
Title: Matter density perturbation and power spectrum in running vacuum model
Comments: 7 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

We investigate the matter density perturbation $\delta_m$ and power spectrum $P(k)$ in the running vacuum model (RVM) with the cosmological constant being a function of the Hubble parameter, given by $\Lambda = \Lambda_0 + 6 \sigma H H_0+ 3\nu H^2$. Taking the dark energy perturbation into consideration, we derive the evolution equation for $\delta_m$ and find a specific scale $d_{cr}=2 \pi/k_{cr}$, which divides the evolution of the universe into the sub and super-interaction regimes, corresponding to $k \ll k_{cr}$ and $k \gg k_{cr}$, respectively. For the former, the evolution of $\delta_m$ has the same behavior as that in the $\Lambda$CDM model, while for the latter, the growth of $\delta_m$ is frozen (greatly enhanced) when $\nu + \sigma >(<)0$ due to the couplings between radiation, matter and dark energy. It is clear that the observational data rule out the cases with $\nu<0$ and $\nu + \sigma <0$, while the allowed window for the model parameters is extremely narrow with $\nu, |\sigma| \lesssim \mathcal{O}(10^{-7})$.

[46]  arXiv:1607.07299 [pdf, other]
Title: BaTMAn: Bayesian Technique for Multi-image Analysis
Comments: 17 pages, 5 Figure, 2 Tables
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

This paper describes the Bayesian Technique for Multi-image Analysis (BaTMAn), a novel image segmentation technique based on Bayesian statistics, whose main purpose is to characterize an astronomical dataset containing spatial information and perform a tessellation based on the measurements and errors provided as input. The algorithm will iteratively merge spatial elements as long as they are statistically consistent with carrying the same information (i.e. signal compatible with being identical within the errors). We illustrate its operation and performance with a set of test cases that comprises both synthetic and real Integral-Field Spectroscopic (IFS) data. Our results show that the segmentations obtained by BaTMAn adapt to the underlying structure of the data, regardless of the precise details of their morphology and the statistical properties of the noise. The quality of the recovered signal represents an improvement with respect to the input, especially in those regions where the signal is actually constant and/or the signal-to-noise ratio of the measurements is low. However, the algorithm may be sensitive to small-scale random fluctuations (depending on the dimensionality of the data and the adopted priors), and its ability to recover the signal in the presence of spatial gradients is limited. Due to these effects, the output errors may be underestimated by as much as a factor of the order of two. Two of the most interesting aspects of the algorithm are that (i) it will prioritise the conservation of all the statistically-significant information over the reduction of the noise, and (ii) the precise choice of the input data does have a crucial impact on the results. Hence, the philosophy of BaTMAn is not to use it as a "black box" that improves the signal-to-noise ratio, but as a new approach for the characterization of spatially-resolved data prior to its scientific analysis.

[47]  arXiv:1607.07308 [pdf, ps, other]
Title: Constraints on the Broad Line Region Properties and Extinction in Local Seyferts
Comments: 19 pages, 14 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use high spectral resolution (R > 8000) data covering 3800-13000\r{A} to study the physical conditions of the broad line region (BLR) of nine nearby Seyfert 1 galaxies. Up to six broad HI lines are present in each spectrum. A comparison - for the first time using simultaneous optical to near-infrared observations - to photoionisation calculations with our devised simple scheme yields the extinction to the BLR at the same time as determining the density and photon flux, and hence distance from the nucleus, of the emitting gas. This points to a typical density for the HI emitting gas of 10$^{11}$cm$^{-3}$ and shows that a significant amount of this gas lies at regions near the dust sublimation radius, consistent with theoretical predictions. We also confirm that in many objects the line ratios are far from case B, the best-fit intrinsic broad-line H$\alpha$/H$\beta$ ratios being in the range 2.5-6.6 as derived with our photoionization modeling scheme. The extinction to the BLR, based on independent estimates from HI and HeII lines, is A$_V$ $\le$ 3 for Seyfert 1-1.5s, while Seyfert 1.8-1.9s have A$_V$ in the range 4-8. A comparison of the extinction towards the BLR and narrow line region (NLR) indicates that the structure obscuring the BLR exists on scales smaller than the NLR. This could be the dusty torus, but dusty nuclear spirals or filaments could also be responsible. The ratios between the X-ray absorbing column N$_H$ and the extinction to the BLR are consistent with the Galactic gas-to-dust ratio if N$_H$ variations are considered.

[48]  arXiv:1607.07317 [pdf, other]
Title: The stellar mass distribution of S$^4$G disk galaxies and the signatures of bar-induced secular evolution
Comments: 22 pages, 18 figures, accepted for publication in A&A (July 24, 2016)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use 3.6 $\mu$m photometry from the Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G) to trace the stellar distribution in nearby disk galaxies ($z\approx0$) with total stellar masses $10^{8.5}\lesssim M_{\ast}/M_{\odot}\lesssim10^{11}$ and mid-IR Hubble types $-3 \le T \le 10$, and to provide observational constraints for galaxy formation models to be checked against. For 1154 galaxies with disk inclinations lower than $65^{\circ}$, we Fourier decompose and rescale their images to a common frame determined (i) by the size in physical units, (ii) by their disk scalelength, and for 748 barred galaxies (iii) by both the length and orientation of their bars. We stack the resized density profiles and images to obtain statistically representative average stellar disks and bars in bins of $M_{\ast}$ and $T$. We also calculate the mean stellar contribution to the circular velocity. We infer the gravitational potentials from the synthetic bars to obtain the tangential-to-radial force ratio ($Q_{\rm T}$) and $A_2$ profiles in the different bins. We provide observational evidence for bar-induced secular evolution of disk galaxies. For $M_{\ast} \ge 10^{9}M_{\odot}$, we find a significant difference in the stellar density profiles of barred and non-barred systems: (i) disks in barred galaxies show larger scalelengths ($h_{\rm R}$) and fainter extrapolated central surface brightnesses ($\Sigma_{0}$), (ii) the mean surface brightness profiles ($\Sigma_{\ast}$) of barred and non-barred galaxies intersect each other slightly beyond the mean bar length, most likely at the bar corotation, and (iii) the central mass concentration of barred galaxies is larger (by almost a factor 2 when $T\le5$) than in their non-barred counterparts. We also show that bars hosted by early-type galaxies are more centrally concentrated and have larger density amplitudes than their late-type counterparts (Abridged).

[49]  arXiv:1607.07323 [pdf, ps, other]
Title: MHD simulations of three-dimensional Resistive Reconnection in a cylindrical plasma column
Comments: 11 pages, 11 figures, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Magnetic reconnection is a plasma phenomenon where a topological rearrangement of magnetic field lines with opposite polarity results in dissipation of magnetic energy into heat, kinetic energy and particle acceleration. Such a phenomenon is considered as an efficient mechanism for energy release in laboratory and astrophysical plasmas. An important question is how to make the process fast enough to account for observed explosive energy releases. The classical model for steady state magnetic reconnection predicts reconnection times scaling as $S^{1/2}$ (where $S$ is the Lundquist number) and yields times scales several order of magnitude larger than the observed ones. Earlier two-dimensional MHD simulations showed that for large Lundquist number the reconnection time becomes independent of $S$ ("fast reconnection" regime) due to the presence of the secondary tearing instability that takes place for $S \gtrsim 1 \times 10^4$. We report on our 3D MHD simulations of magnetic reconnection in a magnetically confined cylindrical plasma column under either a pressure balanced or a force-free equilibrium and compare the results with 2D simulations of a circular current sheet. We find that the 3D instabilities acting on these configurations result in a fragmentation of the initial current sheet in small filaments, leading to enhanced dissipation rate that becomes independent of the Lundquist number already at $S \simeq 1\times 10^3$.

[50]  arXiv:1607.07325 [pdf, ps, other]
Title: The local black hole mass function derived from the M_{BH}-P and the M_{BH}-n relations
Authors: Burcin Mutlu Pakdil (Univ. Minnesota), Marc S. Seigar (Univ. Minnesota Duluth), Benjamin L. Davis (Univ. Arkansas, Arkansas Tech Univ.)
Comments: Accepted for publication in ApJ. For full version of paper with high-resolution figures go to this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a determination of the supermassive black hole (SMBH) mass function for early- and late-type galaxies in the nearby universe (z<0.0057), established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern hemisphere. The sample is defined by limiting luminosity (redshift-independent) distance, D_L=25.4 Mpc, and a limiting absolute B-band magnitude, M_B=-19.12. These limits define a sample of 140 spiral, 30 elliptical (E), and 38 lenticular (S0) galaxies. We established the Sersic index distribution for early-type (E/S0) galaxies in our sample. Davis et al. (2014) established the pitch angle distribution for their sample, which is identical to our late-type (spiral) galaxy sample. We then used the pitch angle and the Sersic index distributions in order to estimate the SMBH mass function for our volume-limited sample. The observational simplicity of our approach relies on the empirical relation between the mass of the central (SMBH) and the Sersic index (Graham et al. 2007) for an early-type galaxy or the logarithmic spiral arm pitch angle (Berrier et al. 2013) for a spiral galaxy. Our SMBH mass function agrees well at the high-mass end with previous values in the literature. At the low-mass end, while inconsistencies exist in previous works that still need to be resolved, our work is more in line with expectations based on modeling of black hole evolution.

[51]  arXiv:1607.07328 [pdf, other]
Title: Decaying dark matter search with NuSTAR deep sky observations
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present the results of the search for decaying dark matter with particle mass in the 6-40 keV range with NuSTAR deep observations of COSMOS and ECDFS empty sky fields. We show that main contribution to the decaying dark matter signal from the Milky Way galaxy comes through the aperture of the NuSTAR detector, rather than through the focusing optics. High sensitivity of the NuSTAR detector, combined with the large aperture and large exposure times of the two observation fields allow us to improve previously existing constraints on the dark matter decay time by up to an order of magnitude in the mass range 10-30 keV. In the particular case of the nuMSM sterile neutrino dark matter, our constraints impose an upper bound m<20 keV on the dark matter particle mass. We report detection of four unidentified spectral lines in our data set. These line detections are either due to the systematic effects (uncertainties of calibrations of the NuSTAR detectors) or have an astrophysical origin. We discuss different possibilities for testing the nature of the detected lines.

[52]  arXiv:1607.07333 [pdf, other]
Title: Influence of a second satellite on the rotational dynamics of an oblate moon
Comments: 19 pages, 9 figures; accepted for publication in Celestial Mechanics and Dynamical Astronomy
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Chaotic Dynamics (nlin.CD); Space Physics (

The gravitational influence of a second satellite on the rotation of an oblate moon is numerically examined. A simplified model, assuming the axis of rotation perpendicular to the (Keplerian) orbit plane, is derived. The differences between the two models, i.e. in the absence and presence of the second satellite, are investigated via bifurcation diagrams and by evolving compact sets of initial conditions in the phase space. It turns out that the presence of another satellite causes some trajectories, that were regular in its absence, to become chaotic. Moreover, the highly structured picture revealed by the bifurcation diagrams in dependence on the eccentricity of the oblate body's orbit is destroyed when the gravitational influence is included, and the periodicities and critical curves are destroyed as well. For demonstrative purposes, focus is laid on parameters of the Saturn-Titan-Hyperion system, and on oblate satellites on low-eccentric orbits, i.e. $e\approx 0.005$.

[53]  arXiv:1607.07367 [pdf, other]
Title: Discontinuous Galerkin finite element methods for radiative transfer in spherical symmetry
Comments: accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The discontinuous Galerkin finite element method (DG-FEM) is successfully applied to treat a broad variety of transport problems numerically. In this work, we use the full capacity of the DG-FEM to solve the radiative transfer equation in spherical symmetry. We present a discontinuous Galerkin method to directly solve the spherically-symmetric radiative transfer equation as a two-dimensional problem. The transport equation in spherical atmospheres is more complicated than in the plane-parallel case due to the appearance of an additional derivative with respect to the polar angle. The DG-FEM formalism allows for the exact integration of arbitrarily complex scattering phase functions, independent of the angular mesh resolution. We show that the discontinuous Galerkin method is able to describe accurately the radiative transfer in extended atmospheres and to capture discontinuities or complex scattering behaviour which might be present in the solution of certain radiative transfer tasks and can, therefore, cause severe numerical problems for other radiative transfer solution methods.

[54]  arXiv:1607.07369 [pdf, ps, other]
Title: Dormant Comets Among the Near-Earth Object Population: A Meteor-Based Survey
Comments: MNRAS in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Dormant comets in the near-Earth object (NEO) population are thought to be involved in the terrestrial accretion of water and organic materials. Identification of dormant comets is difficult as they are observationally indistinguishable from their asteroidal counterparts, however they may have produced dust during their final active stages which potentially are detectable today as weak meteor showers at the Earth. Here we present the result of a reconnaissance survey looking for dormant comets using 13~567~542 meteor orbits measured by the Canadian Meteor Orbit Radar (CMOR). We simulate the dynamical evolution of the hypothetical meteoroid streams originated from 407 near-Earth asteroids in cometary orbits (NEACOs) that resemble orbital characteristics of Jupiter-family comets (JFCs). Out of the 44 hypothetical showers that are predicted to be detectable by CMOR, we identify 5 positive detections that are statistically unlikely to be chance associations, including 3 previously known associations. This translates to a lower limit to the dormant comet fraction of $2.0\pm1.7\%$ in the NEO population and a dormancy rate of $\sim 10^{-5}~\mathrm{yr^{-1}}$ per comet. The low dormancy rate confirms disruption and dynamical removal as the dominant end state for near-Earth JFCs. We also predict the existence of a significant number of meteoroid streams whose parents have already been disrupted or dynamically removed.

[55]  arXiv:1607.07377 [pdf, other]
Title: Frames of most uniform Hubble flow
Authors: David Kraljic (Oxford), Subir Sarkar (Oxford & Copenhagen)
Comments: 18 pages, 8 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

It has been observed that the locally measured Hubble parameter converges quickest to the background value and the dipole structure of the velocity field is smallest in the reference frame of the Local Group of galaxies. We study the statistical properties of Lorentz boosts with respect to the Cosmic Microwave Background frame which make the Hubble flow look most uniform around a particular observer. We use a very large N-Body simulation to extract the dependence of the boost velocities on the local environment such as underdensities, overdensities, and bulk flows. We find that the observation is not unexpected if we are located in an underdensity, which is indeed the case for our position in the universe. The amplitude of the measured boost velocity for our location is consistent with the expectation in the standard cosmology.

[56]  arXiv:1607.07399 [pdf, other]
Title: Design and development of an ambient-temperature continuously-rotating achromatic half-wave plate for CMB polarization modulation on the POLARBEAR-2 experiment
Comments: To be published in Proc. of SPIE, Volume 9914, Number 99142U-1, 2016
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We describe the development of an ambient-temperature continuously-rotating half-wave plate (HWP) for study of the Cosmic Microwave Background (CMB) polarization by the POLARBEAR-2 (PB2) experiment. Rapid polarization modulation suppresses 1/f noise due to unpolarized atmospheric turbulence and improves sensitivity to degree-angular-scale CMB fluctuations where the inflationary gravitational wave signal is thought to exist. A HWP modulator rotates the input polarization signal and therefore allows a single polarimeter to measure both linear polarization states, eliminating systematic errors associated with differencing of orthogonal detectors. PB2 projects a 365-mm-diameter focal plane of 7,588 dichroic, 95/150 GHz transition-edge-sensor bolometers onto a 4-degree field of view that scans the sky at $\sim$ 1 degree per second. We find that a 500-mm-diameter ambient-temperature sapphire achromatic HWP rotating at 2 Hz is a suitable polarization modulator for PB2. We present the design considerations for the PB2 HWP, the construction of the HWP optical stack and rotation mechanism, and the performance of the fully-assembled HWP instrument. We conclude with a discussion of HWP polarization modulation for future Simons Array receivers.

[57]  arXiv:1607.07404 [pdf, ps, other]
Title: Evolution of density and velocity profiles of matter in large voids
Comments: 9 figures; accepted by Advances in Astronomy and Space Physics
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We analyse the evolution of cosmological perturbations which leads to the formation of large voids in the distribution of galaxies. We assume that perturbations are spherical and all components of the Universe - radiation, matter and dark energy - are continuous media with ideal fluid energy-momentum tensors, which interact only gravitationally. Equations of the evolution of perturbations in the comoving to cosmological background reference frame for every component are obtained from equations of conservation and Einstein's ones and are integrated by modified Euler method. Initial conditions are set at the early stage of evolution in the radiation-dominated epoch, when the scale of perturbation is mush larger than the particle horizon. Results show how the profiles of density and velocity of matter in spherical voids with different overdensity shells are formed.

[58]  arXiv:1607.07408 [pdf, ps, other]
Title: On the dark matter haloes inner structure and galaxy morphology
Authors: A. Del Popolo (Department of Physics and Astronomy, UniVersity of Catania, Italy)
Comments: 27 pages, 5 figures, published in Astronomy & Space Science
Journal-ref: Astronomy & Space Science, 2016, 361 (7), 222
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In the present paper, we extend the study of Del Popolo (2010) to determine the slope of the inner density profile of galaxy haloes with different morphologies. We study how galaxy morphology changes the relation between the inner slope of the galaxy halo density profile, $\alpha$, and the stellar mass, $M_{*}$, or rotation velocity $V_{\rm rot}$. For this, we use the model of Del Popolo (2009) in combination with observed data from the Romanowsky \& Fall (2012) sample of elliptical and spiral galaxies, the Local Group sample compiled by McConnachie (2012), and the simulation results by Cloet-Osselaer et al. (2014). We find that the slope $\alpha$ flattens monotonically, from $\alpha \simeq -1 $ at $V_{\rm rot} \simeq 250$ km/s, to $\alpha \simeq 0 $. After $V_{\rm rot}\simeq 25$ km/s the slope starts to steepen. The steepening happens in the mass range dominated by non-rotationally supported galaxies (e.g., dSphs) and depends on the level of offset in the angular momentum of rotationally and non-rotationally dominated galaxies. The steepening is a consequence of the decrease in baryons content, and angular momentum in spheroidal dwarf galaxies. We finally compare our result to the SPH simulations of Di Cintio. Our result is in qualitatively agreement with their simulations, with the main difference that the inner slope $\alpha$ at small stellar masses ($M_* \lesssim10^{8} M_{\odot}$) is flatter than that in their simulations. As a result, the claim that finding a core in dwarf galaxies with masses slightly smaller than $\simeq 10^6 M_{\odot}$, (as in the Di Cintio, or Governato, supernovae feedback mechanism) would be a problem for the $\Lambda$CDM model must be probably revised.

[59]  arXiv:1607.07410 [pdf, other]
Title: Search for low-mass WIMPs in a 0.6 kg day exposure of the DAMIC experiment at SNOLAB
Comments: 13 pages, 10 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)

We present results of a dark matter search performed with a 0.6 kg day exposure of the DAMIC experiment at the SNOLAB underground laboratory. We measured the energy spectrum of ionization events in the bulk silicon of charge-coupled devices (CCDs) down to a signal of 60 eV electron-equivalent. The data is consistent with radiogenic backgrounds, and constraints on the spin-independent WIMP-nucleon elastic-scattering cross-section are accordingly placed. Cross-sections relevant to the potential signal from the CDMS-II Si experiment are excluded using the same target for the first time. This result, obtained with a limited exposure, demonstrates the potential to explore the low-mass WIMP region (<10 GeV/$c^{2}$) of the upcoming DAMIC100, a 100 g detector currently being installed in SNOLAB.

[60]  arXiv:1607.07420 [pdf, ps, other]
Title: Hitomi constraints on the 3.5 keV line in the Perseus galaxy cluster
Comments: 8 pages, 4 figures. Submitted to ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E=3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported flux level. The high flux derived with XMM MOS for the Perseus region covered by Hitomi is excluded at >3-sigma within the energy confidence interval of the most constraining previous study. If XMM measurement uncertainties for this region are included, the inconsistency with Hitomi is at a 99% significance for a broad dark-matter line and at 99.7% for a narrow line from the gas. We do find a hint of a broad excess near the energies of high-n transitions of Sxvi (E=3.44 keV rest-frame) -- a possible signature of charge exchange in the molecular nebula and one of the proposed explanations for the 3.5 keV line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.