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J.P. Magué & B. Ménard

[1]
Title: Afterglow rebrightenings as a signature of a long-lasting central engine activity? The emblematic case of GRB 100814A
Comments: 11 pages, 7 figures, 2 tables; Astronomy & Astrophysics, in press
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

In the past few years the number of well-sampled optical to NIR light curves of long Gamma-Ray Bursts (GRBs) has greatly increased particularly due to simultaneous multi-band imagers such as GROND. Combining these densely sampled ground-based data sets with the Swift UVOT and XRT space observations unveils a much more complex afterglow evolution than what was predicted by the most commonly invoked theoretical models. GRB 100814A represents a remarkable example of these interesting well-sampled events, showing a prominent late-time rebrightening in the optical to NIR bands and a complex spectral evolution. This represents a unique laboratory to test the different afterglow emission models. Here we study the nature of the complex afterglow emission of GRB 100814A in the framework of different theoretical models. Moreover, we compare the late-time chromatic rebrightening with those observed in other well-sampled long GRBs. We analysed the optical and NIR observations obtained with the seven-channel Gamma-Ray burst Optical and Near-infrared Detector at the 2.2 m MPG/ESO telescope together with the X-ray and UV data detected by the instruments onboard the Swift observatory. The broad-band afterglow evolution, achieved by constructing multi-instrument light curves and spectral energy distributions, will be discussed in the framework of different theoretical models. We find that the standard models that describe the broad-band afterglow emission within the external shock scenario fail to describe the complex evolution of GRB 100814A, and therefore more complex scenarios must be invoked. [abridged]

[2]
Title: The Mystery of the $σ$-Bump -- A new Signature for Major Mergers in Early-type Galaxies?
Comments: 7 pages, 4 figures, submitted to APJ Letters
Subjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The stellar velocity dispersion as a function of the galactocentric radius of an early-type galaxy can generally be well approximated by a power law $\sigma \propto r^{\beta}$. However, some observed dispersion profiles show a deviation from this fit at intermediate radii, usually between one and three $R_{\mathrm{eff}}$, where the velocity dispersion remains constant with radius, showing a bump-like behavior, which we term the "$\sigma$-"bump. To understand the origin of this $\sigma$-bump, we study a set of simulated early-type galaxies formed in major mergers. We find the $\sigma$-bump in all of our simulated early-type galaxies, with the size and position of the bump slightly varying from galaxy to galaxy, leading to the assumption that the bump is a characteristic of the major merger formation scenario. The feature can be seen both in the intrinsic and projected stellar velocity dispersions. In contrast to shells that form during the merger event but evolve with time and finally disappear, the $\sigma$-bump stays nearly constant with radius and is a permanent feature that is preserved until the end of the simulation. The $\sigma$-bump is not seen in the dark matter and gas components and we therefore conclude that it is a purely stellar feature of merger remnants.

[3]
Title: Magnetized HI Fibers and the Rolling Hough Transform
Comments: 13 pages, 12 figures. Submitted to the Astrophysical Journal. Comments welcome
Subjects: Galaxy Astrophysics (astro-ph.GA)

We present observations of a new group of structures in the diffuse Galactic ISM: slender, linear HI features we dub "fibers" that extend for many degrees at high Galactic latitude. To characterize and measure the extent and strength of these fibers, we present the Rolling Hough Transform (RHT), a new machine vision method for parameterizing the coherent linearity of structures in the image plane. With this powerful new tool we show the fibers are oriented along the interstellar magnetic field as probed by starlight polarization. We find that these low column (N(HI) ~ 5 x 10^18 cm^-2) fiber features are most likely a component of the local cavity wall, about 100 pc away. The HI data we use to demonstrate this alignment at high latitude are from the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) Survey and the Parkes Galactic All Sky Survey (GASS). We find better alignment in the higher resolution GALFA-HI data, where the fibers are more visually evident. This trend continues in our investigation of magnetically aligned linear features in the Riegel-Crutcher HI cold cloud, detected in the Southern Galactic Plane Survey (SGPS). We propose an application of the RHT for estimating the field strength in such a cloud, based on the Chandrasekhar-Fermi method. We conclude that data-driven, quantitative studies of ISM morphology can be very powerful predictors of underlying physical quantities.

[4]
Title: Discovery of a new black hole transient within 100" (400 pc) of M31*
Comments: Accepted for publication in ApJ. 4 pages, 4 figures. arXiv admin note: substantial text overlap with arXiv:1305.1302
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We identified a new X-ray transient CXOM31 004252.457+411631.17 (T13) in M31 during a 2013 June Chandra observation. This system is particularly exciting because it is located within 100" of M31*; it is thought that this region of the bulge is sufficiently dense to form X-ray binaries dynamicaly, but only systems with black hole accretors and/or short periods are expected to survive. A follow-up XMM-Newton observation yielded a soft spectrum, well described by a 0.39+/-0.02 keV disk blackbody; applying this model to the Chandra observation yielded an observed 0.3--10 keV luminosity peak of 6.2+/-0.6 E+37 erg/s (4.7 E+36 erg/s in the 2.0--10 keV band). Observing with HST/ACS did not reveal an optical counterpart, but allowed us to place an upper limit of B >26.9, corresponding to an absolute V band magnitude >2.0. From the 2--10 keV luminosity and absolute V magnitude, we estimate an orbital period $<$5 h from an empirical relation. Fitting a disk blackbody + blackbody model allows us to reject a neutron star accretor at a 14 sigma level.

[5]
Title: More than just halo mass: Modelling how the red galaxy fraction depends on multiscale density in a HOD framework
Comments: 24 pages, 21 figures, accepted for publication by MNRAS
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The fraction of galaxies with red colours depends sensitively on environment, and on the way in which environment is measured. To distinguish competing theories for the quenching of star formation, a robust and complete description of environment is required, to be applied to a large sample of galaxies. The environment of galaxies can be described using the density field of neighbours on multiple scales - the multiscale density field. We are using the Millennium simulation and a simple HOD prescription which describes the multiscale density field of Sloan Digital Sky Survey DR7 galaxies to investigate the dependence of the fraction of red galaxies on the environment. Using a volume limited sample where we have sufficient galaxies in narrow density bins, we have more dynamic range in halo mass and density for satellite galaxies than for central galaxies. Therefore we model the red fraction of central galaxies as a constant while we use a functional form to describe the red fraction of satellites as a function of halo mass which allows us to distinguish a sharp from a gradual transition. While it is clear that the data can only be explained by a gradual transition, an analysis of the multiscale density field on different scales suggests that colour segregation within the haloes is needed to explain the results. We also rule out a sharp transition for central galaxies, within the halo mass range sampled.

[6]
Title: Distinguishing models of reionization using future radio observations of 21-cm 1-point statistics
Comments: 18 pages, 15 figures, Submitted to MNRAS
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We explore the impact of reionization topology on 21-cm statistics. Four reionization models are presented which emulate large ionized bubbles around over-dense regions (21CMFAST/ global-inside- out), small ionized bubbles in over-dense regions (local-inside-out), large ionized bubbles around under-dense regions (global-outside-in) and small ionized bubbles around under-dense regions (local-outside-in). We show that first-generation instruments might struggle to distinguish global models using the shape of the power spectrum alone. All instruments considered are capable of breaking this degeneracy with the variance, which is higher in outside-in models. Global models can also be distinguished at small scales from a boost in the power spectrum from a positive correlation between the density and neutral-fraction fields in outside-in models. Negative skewness is found to be unique to inside-out models and we find that pre-SKA instruments could detect this feature in maps smoothed to reduce noise errors. The early, mid and late phases of reionization imprint signatures in the brightness-temperature moments, we examine their model dependence and find pre-SKA instruments capable of exploiting these timing constraints in smoothed maps. The dimensional skewness is introduced and is shown to have stronger signatures of the early and mid-phase timing if the inside-out scenario is correct.

[7]
Title: Do the spectral energy distributions of type 1 AGN show diversity?
Comments: 14 pages, 8 figures, 2 tables. Accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We create broadband SEDs of 761 type 1 AGN. The Scott et al. sample, created by a cross-correlation of the optical SDSS DR5 quasar catalogue and the 2XMMi catalogue of serendipitous X-ray sources, is further matched with the FIRST catalogue of radio sources, the WISE MIR all-sky data release, the 2MASS NIR point source catalogue, the UKIDSS DR9 Large Area Survey and the GALEX all-sky and medium UV imaging surveys. This allows broadband SEDs covering log(nu)~9.2-18.1 to be created. We investigate variations in the SED shape by binning a subsample of 237 AGN with the best quality SEDs according to their X-ray spectral parameters, their AGN sub-type and their luminosity, black hole mass and Eddington ratio. The AGN sub-populations show some significant differences in their SEDs; X-ray absorbed AGN show a deficit of emission at X-ray/UV frequencies and an excess in the MIR consistent with absorption and re-emission, radio-loud AGN show increased radio and X-ray emission, consistent with the presence of a jet component in addition to the emission seen from radio-quiet AGN and the SEDs of NLS1s only differ from other type 1s in the X-ray regime, suggesting any physical differences are limited to their X-ray emitting region. Binning the AGN according to underlying physical parameters reveals more subtle differences in the SEDs. The X-ray spectral slope does not appear to have any influence or dependence on the multiwavelength emission in the rest of the SED. The contribution of X-rays to Lbol is lower in higher luminosity sources, and relatively more emission in the optical/UV is seen in AGN with higher Lx. Variations in the relative flux and peak frequency of the BBB are observed and may suggest higher inner disc temperatures with increasing accretion rates. Overall, we find that the diversity in the SED shapes is relatively small, and we find no apparent single driver for the variations.

[8]
Title: Star formation activity and gas stripping in the Cluster Projected Phase-Space (CPPS)
Comments: 24 pages, 9 figures, 5 tables; accepted for publication in MNRAS
Subjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

This work is focused on the study of the distribution in the CPPS of passive and star-forming galaxy populations and also, the intense and quiescent star-forming populations for a set of 9 nearby z<0.05 galaxy clusters. Furthermore, we compare the CPPS distribution of the passive galaxy population with the accreted halo population of a set of 28 simulated clusters and the star-forming population with the non-accreted population. We consider various cluster accretion epochs and accretion radii where it is assumed that star formation in galaxies becomes quenched, in order to segregate the accreted population from the non-accreted population. Just applying this segregation in simulations, we get a qualitative agreement between the CPPS distributions of the passive and the accreted populations and also between the star-forming and the non-accreted populations. The uncertainty in cluster centering strongly affects the pronounced cuspy profiles of the projected density and also, it can explain the main difference (i.e. inner slope) between the CPPS distribution of passive and accreted populations. The CPPS density of star-forming galaxies and the intensity of ram-pressure stripping present an opposite trend throughout the CPPS. This implies that ram-pressure stripping significantly contributes to modulate the observed CPPS distribution of star-forming galaxies inside and around cluster virial regions. The significant fraction of star-forming galaxies at the projected center of clusters are mainly those galaxies with low l-o-s velocities and they can be mainly identified as those galaxies with a remaining star formation activity (quiescent star-forming galaxies) inside the physical virial region or, in a lower degree, as galaxy interlopers i.e. outside the physical virial region.(abridged)

[9]
Title: On the art and theory of self-calilbration
Comments: 15 pages, 3 figures, submitted
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Information Theory (cs.IT); Data Analysis, Statistics and Probability (physics.data-an); Machine Learning (stat.ML)

Calibration is the process of inferring how much measured data depend on the signal one is interested in. It is essential for any quantitative signal estimation on the basis of the data. Here, we investigate the "art" of self-calibration that augments an external calibration solution using a known reference signal with an internal calibration on the unknown measurement signal itself. Contemporary self-calibration schemes try to find a self-consistent solution for signal and calibration. This can be understood in terms of maximizing their joint probability. Thus, the full uncertainty structure of this probability around its maximum is not taken into account by these schemes. Therefore better schemes -- in sense of minimal square error -- can be designed that also reflect the uncertainties of signal and calibration reconstructions. We argue that at least the signal uncertainty should not be neglected in typical measurement situations, since the calibration solutions suffer from a systematic bias otherwise, which consequently distorts the signal reconstruction. Furthermore, we argue that non-parametric, signal-to-noise filtered calibration should provide more accurate reconstructions than the common bin averages and provide a new, improved self-calibration scheme. We illustrate our findings with a simplistic numerical example.

[10]
Title: Absolute properties of the eclipsing binary system AQ Serpentis: A stringent test of convective core overshooting in stellar evolution models
Authors: Guillermo Torres (1), Luiz Paulo R. Vaz (2), Claud H. Sandberg Lacy (3), Antonio Claret (4) ((1) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, (2) ICEx-UFMG, Belo Horizonte, Brazil, (3) Department of Physics, University of Arkansas, Fayetteville, AR, (4) Instituto de Astrofisica de Andalucia, CSIC, Granada, Spain)
Comments: 12 pages in emulateapj format, including all tables and figures. To appear in The Astronomical Journal (accepted)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report differential photometric observations and radial-velocity measurements of the detached, 1.69-day period, double-lined eclipsing binary AQ Ser. Accurate masses and radii for the components are determined to better than 1.8% and 1.1%, respectively, and are M1 = 1.417 +/- 0.021 MSun, M2 = 1.346 +/- 0.024 MSun, R1 = 2.451 +/- 0.027 RSun, and R2 = 2.281 +/- 0.014 RSun. The temperatures are 6340 +/- 100 K (spectral type F6) and 6430 +/- 100 K (F5), respectively. Both stars are considerably evolved, such that predictions from stellar evolution theory are particularly sensitive to the degree of extra mixing above the convective core (overshoot). The component masses are different enough to exclude a location in the H-R diagram past the point of central hydrogen exhaustion, which implies the need for extra mixing. Moreover, we find that current main-sequence models are unable to match the observed properties at a single age even when allowing the unknown metallicity, mixing length parameter, and convective overshooting parameter to vary freely and independently for the two components. The age of the more massive star appears systematically younger. AQ Ser and other similarly evolved eclipsing binaries showing the same discrepancy highlight an outstanding and largely overlooked problem with the description of overshooting in current stellar theory.

[11]
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

Inflationary models based on a single scalar field $\phi$ with a quadratic potential $V = \frac{1}{2} m^2 \phi^2$ are disfavoured by the recent Planck constraints on the scalar index, $n_s$, and the tensor-to-scalar ratio for cosmological density perturbations, $r_T$. In this paper we study how such a quadratic inflationary model can be rescued by postulating additional fields with quadratic potentials, such as might occur in sneutrino models, which might serve as either curvatons or supplementary inflatons. Introducing a second scalar field reduces but does not remove the pressure on quadratic inflation, but we find a sample of three-field models that are highly compatible with the Planck data on $n_s$ and $r_T$. We exhibit a specific three-sneutrino example that is also compatible with the data on neutrino mass difference and mixing angles.

[12]
Title: Conversion between the power spectra of a field and its logarithm
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We derive a formula to convert the power spectrum of a log-normal field to the power spectrum of the logarithmic Gaussian field and vice versa. The formula is useful to generate log-normal random fields with a given spectrum as well as comparing power spectra of observed or simulated densities with the power spectrum of the log-density that might be available from theoretical considerations. We apply the formalism to the spectrum of the large-scale matter density to compare the linearly evolved spectrum of the logarithmic density with the non-linear density spectrum according to third order perturbation theory. We find a qualitative albeit not quantitative agreement for redshifts between 1 and 7, if the linear growth factor is applied to the logarithmic density. A quantitative agreement can be found if a factor proportional to the square root of the linear growth factor is applied to the logarithmic density and the remaining factor to the density contrast.

[13]
Title: The Earth's velocity for direct detection experiments
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The Earth's velocity relative to the Sun in galactic coordinates is required in the rate calculation for direct detection experiments. We provide a rigorous derivation of this quantity to first order in the eccentricity of the Earth's orbit. We also discuss the effect of the precession of the equinoxes, which has previously been ignored. Comparing with other expressions in the literature, we confirm that the expression of Lee, Lisanti and Safdi is correct, while the expression of Lewin and Smith, the de facto standard expression, contains an error. For calculations of the absolute event rate, the leading order expression is sufficient while for modulation searches, an expression with the eccentricity is required for accurate predictions of the modulation phase.

[14]
Title: On the contribution of active galactic nuclei to reionization (Research Note)
Comments: 6 pages, 4 figures, accepted by Astronomy & Astrophysics
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The electron scattering optical depth constraints on reionization suggest that there may be other sources that contribute to the ionization of hydrogen aside from observable star forming galaxies. Often the calculated value of the electron scattering optical depth, \tau_{es}, falls below the measurements derived from observations of the CMB or an assumption about non-observable sources must be made in order to reach agreement. Here, we calculate the hydrogen ionization fraction as a function of redshift and the electron scattering optical depth from both galaxies and active galactic nuclei (AGN) factoring in the secondary collisional ionizations from the AGN X-ray emission. In this paper we use the most current determination of the evolving hard X-ray luminosity function and extrapolate its evolution beyond z = 6. The AGN spectral energy distributions (SEDs) include both UV and X-ray ionizing photons. To search for the largest possible effect, all AGN are assumed to have \lambda_{Edd} = 1.0 and be completely unobscured. The results show that AGNs produce a perturbative effect on the reionization of hydrogen and remains in agreement with current constraints. Our calculations find the epoch of reionization still ends at z \approx 6 and only increases the electron scattering optical depth by ~2.3% under the most optimal conditions. This can only be moderately increased by assuming a constant black hole mass of M_{BH} = 10^(5) solar masses. As a result, we conclude that there is a need for other sources beyond observable galaxies and AGNs that contribute to the reionization of hydrogen at z > 6.

[15]
Title: A Search for Methane in the Atmosphere of GJ 1214b via GTC Narrow-Band Transmission Spectrophotometry
Comments: 12 pages, including 14 figures and 1 table; accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present narrow-band photometric measurements of the exoplanet GJ 1214b using the 10.4 m Gran Telescopio Canarias (GTC) and the OSIRIS instrument. Using tuneable filters we observed a total of five transits, three of which were observed at two wavelengths nearly simultaneously, producing a total of eight individual light curves, six of these probed the possible existence of a methane absorption feature in the 8770 - 8850 {\AA} region at high resolution. We detect no increase in the planet-to-star radius ratio across the methane feature with a change in radius ratio of $\Delta$R = -0.0007 $\pm$ 0.0017 corresponding to a scale height (H) change of -0.5 $\pm$ 1.2 H across the methane feature, assuming a hydrogen dominated atmosphere. We find a variety of water and cloudy atmospheric models fit the data well, but find that cloud-free models provide poor fits. These observations support a flat transmission spectrum resulting from the presence of a high-altitude haze or a water-rich atmosphere, in agreement with previous studies. In this study the observations are predominantly limited by the photometric quality and the limited number of data points (resulting from a long observing cadence), which make the determination of the systematic noise challenging. With tuneable filters capable of high resolution measurements (R ~ 600 - 750) of narrow absorption features, the interpretation of our results are also limited by the absence of high resolution methane models below 1 $\mu$m.

[16]
Title: Computation of the Halo Mass Function Using Physical Collapse Parameters: Application to Non-Standard Cosmologies
Authors: I. Achitouv (LMU), C. Wagner (MPA), J. Weller (LMU), Y. Rasera (LUTh)
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

In this article we compare the halo mass function predicted by the excursion set theory with a drifting diffusive barrier against the results of N-body simulations for several cosmological models. This includes the standard LCDM case for a large range of halo masses, models with different types of primordial non-Gaussianity, and a dark energy model. We show that in all those cosmological scenarios, the abundance of dark matter halos can be described by a drifting diffusive barrier, where the two parameters describing the barrier have physical content. In the case of the Gaussian LCDM, the statistics is precise enough to actually predict those parameters from the initial conditions. Furthermore, we found that the stochasticity in the barrier is non-negligible making the simple deterministic spherical collapse model a bad approximation even at very high halo masses. We also show that using the standard excursion set approach with a barrier inspired by peak patches leads to inconsistent predictions of the halo mass function.

[17]
Title: Observational Constraints From Binary Stars on Stellar Evolution Models
Authors: Guillermo Torres (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Comments: 8 pages including figures and tables. To appear in the Proceedings of Setting a New Standard in the Analysis of Binary Stars, eds. K. Pavlovski, A. Tkachenko and G. Torres, EAS Publication Series
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Accurate determinations of masses and radii in binary stars, along with estimates of the effective temperatures, metallicities, and other properties, have long been used to test models of stellar evolution. As might be expected, observational constraints are plentiful for main-sequence stars, although some problems with theory remain even in this regime. Models in other areas of the H-R diagram are considerably less well constrained, or not constrained at all. I summarize the status of the field, and provide examples of how accurate measurements can supply stringent tests of stellar theory, including aspects such as the treatment of convection. I call attention to the apparent failure of current models to match the properties of stars with masses of 1.1-1.7 MSun that are near the point of central hydrogen exhaustion, possibly connected with the simplified treatment of convective core overshooting.

[18]
Title: Anisotropies of ultra-high energy cosmic rays diffusing from extragalactic sources
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We obtain the dipolar anisotropies in the arrival directions of ultra-high energy cosmic rays diffusing from nearby extragalactic sources. We discuss both the energy regime of spatial diffusion and the quasi-rectilinear one leading to just angular diffusion at higher energies. We obtain analytic results for the anisotropies from a single source which are validated using two different numerical simulations. For a scenario with a few sources in the local supercluster (with the closest source at a typical distance of few to tens of Mpc), we discuss the possible transition between the case in which the anisotropies are dominated by a few sources at energies below few EeV towards the regime in which many sources contribute at higher energies. The effect of a non-isotropic source distribution is also discussed, showing that it can significantly affect the observed dipole.

[19]
Title: Tidal Flows in asynchronous binaries: The beta-factor
Comments: in Setting New Standards in Binary Star Research, A. Tkachenko & K. Pavlovski (eds), EAS Publication Series, in Press
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We discuss the potential role that tidal flows in asynchronous binary stars may play in transporting chemically enriched material from deep layers towards the surface and the corresponding observational consequences of these processes. We suggest that the time-dependent velocity field induced by asynchronous rotation may contribute significantly to the mixing, thus providing a channel for the formation of chemically enriched slowly rotating massive stars.

[20]
Title: A swirling flare-related EUV jet
Authors: Q. M. Zhang, H. S. Ji
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

{We report our observations of a swirling flare-related EUV jet on 2011 October 15.} {We utilised the EUV observations from SDO/AIA. We extracted a wide slit along the jet axis and 12 thin slits across its axis to investigate the longitudinal motion and transverse rotation. We also used data from STEREO/EUVI to investigate the 3D structure of the jet. Gound-based H$\alpha$ images provide a good opportunity to explore the relationship between the cool surge and hot jet. LOS magnetograms from SDO/HMI enable us to study the magnetic evolution of the flare/jet event.} {The onset of jet eruption coincided with the start time of C1.6 flare impulsive phase. The initial velocity and acceleration of the longitudinal motion were 254$\pm10$ km s$^{-1}$ and $-97\pm5$ m s$^{-2}$, respectively. The jet presented helical structure and transverse swirling motion at the beginning of its eruption. The counter-clockwise rotation slowed down from an average velocity of $\sim$122 km s$^{-1}$ to $\sim$80 km s$^{-1}$. The interwinding thick threads of the jet untwisted into multiple thin threads during the rotation that lasted for 1 cycle with a period of $\sim$7 min and an amplitude that increases from $\sim$3.2 Mm at the bottom to $\sim$11 Mm at the upper part. Afterwards, the curtain-like leading edge of the jet continued rising without rotation, leaving a dimming region behind before falling back to the solar surface. The appearance/disappearance of dimming corresponded to the longitudinal ascending/descending motions of jet. Cospatial H$\alpha$ surge and EUV dimming imply that the dimming resulted from the absorption of hot EUV emission by cool surge. The flare/jet event was caused by continuous magnetic cancellation before the start of flare. The jet was associated with the open magnetic fields at the edge of AR 11314.}

[21]
Title: High redshift supermassive blackholes: accretion through cold flows
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We use zoom-in techniques to re-simulate three high-redshift (z > 5.5) halos which host 10^9 solar mass blackholes from the ~ Gpc volume, MassiveBlack cosmological hydrodynamic simulation. We examine a number of factors potentially affecting supermassive blackhole growth at high redshift in cosmological simulations. These include numerical resolution, feedback prescriptions and formulation of smoothed particle hydrodynamics. We find that varying the size of the region over which feedback energy is deposited directly, either for fixed number of neighbours or fixed volume makes very little difference to the accretion history of blackholes. Changing mass resolution by factors of up to 64 also does not change the blackhole growth history significantly. We find that switching from the density-entropy formulation to the pressure-entropy formulation of smoothed particle hydrodynamics slightly increases the accretion rate onto blackholes. In general numerical details appear to have small effects on the main fueling mechanism for blackholes at these high redshifts. We examine the fashion by which this occurs, finding that the insensitivity to simulation technique seems to be a hallmark of the cold flow feeding picture of these high-z supermassive blackholes. We show that the gas that participates in critical accretion phases, in these massive objects at z > 6~7 is in all cases colder, denser, and forms more coherent streams than the average gas in the halo. This is also mostly the case when the blackhole accretion is feedback regulated (z < 6), however the distinction is less prominent. For our resimulated halos, cold flows appear to be a viable mechanism for forming the most massive blackholes in the early universe, occurring naturally in LambdaCDM models of structure formation. Not requiring fine tuning of numerical parameters, they seem to be physically inevitable in these objects.

[22]
Title: The Size-distribution of Scattered Disk TNOs from that of JFCs between 0.2 and 15km effective radius
Comments: 47 pages, 12 Figures, 2 Tables. Accepted by Icarus, December 2013
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We investigate the size-frequency distribution of Jupiter Family comets to determine whether they are primordial accreted objects or collisional fragments. We develop a list of effective radii and their uncertainties for 161 active JFCs and compute the observed size-frequency distribution using a Probability Index technique. The radii range from 0.2 to 15.4 km. This is then corrected for the effects of observational selection using a model published earlier by Meech et al.(2004). We estimate that the total number of active JFCs between 0.2 and 15.4 km is approximately 2300.The active JFC size-frequency distribution, over the range from 0.6 to 10 km where it is best defined, is found to be closer to an exponential distribution in character than a power-law. We then develop a statistical model, based on the assumption of a steady state, for converting the distribution of active JFCs to the SFD of the source population among the TNOs. The model includes the effects of devolatization (that produces a large sub-class of defunct nuclei) and surficial mass-loss. Comparison with available TNO observations shows that to simultaneously attain continuity with the data on objects in the hot TNO population (Fuentes et al,2010), satisfy constraints on the number of TNOs set by the occultation detections of Schlichting et al.(2012), and to remain within upper limits set by the Taiwanese-American Occultation Survey (TAOS; Zhang et al,2013) the total JFC population must contain a large fraction of small defunct nuclei. The effective power-law index of the inferred TNO differential SFD between 1 and 10 km is -4.5 +/- 0.5 indicating a population in this range that is not in fully relaxed collisional equilibrium. We conclude that the cometary nuclei visited by spacecraft and many JFCs are primordial accreted objects relatively unaffected by collisional evolution.

[23]
Title: Observational tests of the picture of disk accretion
Authors: Thomas J. Maccarone (Texas Tech University)
Comments: 21 pages, 3 figures, accepted for publication in ISSI book on black holes in Space Science Reviews
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

In this chapter, I present a summary of observational tests of the basic picture of disk accretion. An emphasis is placed on tests relevant to black holes, but many of the fundamental results are drawn from studies of other classes of systems. Evidence is discussed for the basic structures of accretion flows. The cases of systems with and without accretion disks are discussed, as is the evidence that disks actually form. Also discussed are the hot spots where accretion streams impact the disks, and the boundary layers in the inner parts of systems where the accretors are not black holes. The nature of slow, large amplitude variability is discussed. It is shown that some of the key predictions of the classical thermal-viscous ionization instability model for producing outbursts are in excellent agreement with observational results. It is also show that there are systems whose outbursts are extremely difficult to explain without invoking variations in the rate of mass transfer from the donor star into the outer accretion disk, or tidally induced variations in the mass transfer rates. Finally, I briefly discuss recent quasar microlensing measurements which give truly independent constraints on the inner accretion geometry around black holes.

[24]
Title: Pressure of Degenerate and Relativistic electrons in a superhigh magnetic field
Comments: 26 Papers, 5 Figures, Published in Modern Physics Letters A ., Vol. 28, No. 36 (2013)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Based on our previous work, we deduce a general formula for pressure of degenerate and relativistic electrons,Pe, which is suitable for superhigh magnetic fields, discuss the quantization of Landau levels of electrons, and consider the quantum electrodynam-ic(QED) effects on the equations of states (EOSs) for different matter systems. The main conclusions are as follows:Pe is related to the magnetic field B, matter density ?, and electron fraction Ye ; the stronger the magnetic field, the higher the electron pressure becomes; the high electron pressure could be caused by high Fermi energy of electrons in a superhigh magnetic field; compared with a common radio pulsar, a magnetar could be a more compact oblate spheroid-like deformed neutron star due to the anisotropic total pressure; and an increase in the maximum mass of a magnetar is expected because of the positive contribution of the magnetic field energy to the EOS of the star.

[25]
Title: Constraints on the inverse power-law scalar field dark energy model from strong gravitational lensing data and updated Hubble parameter measurements
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

We constrain the scalar field dark energy model with an inverse power-law potential, i.e., $V(\phi)\propto {\phi}^{-\alpha}$ ($\alpha>0$), from the recent cosmological observations. We compile an updated sample of Hubble parameter measurements including 31 independent data points to constrain the parameters of the inverse power-law scalar field dark energy model. Our results show that the constraining power of the updated sample of $H(z)$ data is almost comparable to that of the SCP Union2 compilation, and a bit stronger than that of SCP Union2.1. The recent sample of the strong gravitational lensing is also adopted to confine the model, the results of which are compatible with those from other data fittings. A joint analysis of the strong gravitational lensing data with the more restrictive updated Hubble parameter measurements and the Type Ia supernovae data from SCP Union2 indicates that the recent observations still can not distinguish whether dark energy is a time-independent cosmological constant or a time-varying dynamical component. We also display the evolutions of the deceleration parameter $q(z)$ and the equation of state $\omega_{\phi}(z)$ of the field $\phi$. Taking the best-fit parameters as prior values, we obtain the transition redshift (deceleration/acceleration) $z_T$ to be 0.73, which is in good agreement with that in the literature. In addition, from the evolution of $\omega_{\phi}(z)$, one can easily find out that the model possesses the feature of the freezing quintessence.

[26]
Title: Opacity of fluffy dust aggregates
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Context. Dust grains coagulate in protoplanetary disks to form fluffy aggregates. Theoretical and experimental studies have shown that the internal density of dust aggregates is expected to be as small as $10^{-4} {\rm ~g~cm^{-3}}$. Disk observations, on the other hand, are interpreted as the emission from compact grains. The emission may come from fluffy aggregates. However, optical properties of such fluffy aggregates have been poorly understood. Aims. We aim to reveal the mass opacity of fluffy aggregates at from infrared to millimeter wavelengths with the filling factor ranging from 1 down to $10^{-4}$. Methods. We use Mie calculations with an effective medium theory. The monomers are assumed to be 0.1 micron-sized grains, which is much shorter than the wavelengths which we focus on. Results. We find that the absorption mass opacity of fluffy aggregates are well characterized by the product $a\times f$, where $a$ is the dust radius and $f$ is the filling factor, except for the interference structure. The scattering mass opacity is also well characterized by a f at short wavelengths while it is higher in more fluffy aggregates at long wavelengths. We also derive the analytic formula of the mass opacity and find that it well reproduces the Mie calculations. We also calculate the expected difference of the emission between compact and fluffy aggregates in protoplanetary disks with a simple dust growth and drift model. We find that the compact and fluffy aggregates can be distinguished by the radial distribution of the opacity index beta. The previous observation of the radial distribution of beta is consistent with the fluffy case, but more observations are required to distinguish fluffy or compact. In addition, we find that the scattered light would be another clue to distinguish the compact and fluffy aggregates.

[27]
Title: Constraints on diffuse gamma-ray emission from structure formation processes in the Coma cluster
Authors: Fabio Zandanel, Shin'ichiro Ando (GRAPPA Institute, University of Amsterdam, Netherlands)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We analyze the 5-year (63 months) data of Large Area Telescope on board Fermi satellite from the Coma galaxy cluster in the energy range between 100 MeV and 100 GeV. The likelihood analyses are performed with several model templates. We consider (1) a point source; (2) models motivated by cosmological hydrodynamical simulations that predict a dominant pion-decay-induced gamma-ray emission from cosmic ray proton-proton interaction with the cluster ambient gas; (3) a phenomenological template based on the cluster radio relic to test the possible associated inverse-Compton scattering of the relic electrons off the cosmic microwave background; and (4) both a disk and ring-like emission profiles to test the inverse-Compton emission from primary electrons accelerated at accreting shocks. We find no excess emission for any of these models, and derive the most stringent constraints to date on the Coma cluster above 100 MeV, and on the tested scenarios in general. The upper limits on the integral flux range from 10^-10 to 10^-9 cm^-2 s^-1, and are stringent enough to challenge different scenarios. We find that the acceleration efficiency of cosmic ray protons and electrons at shocks must be below approximately 15% and 1%, respectively. Additionally, we argue that the proton acceleration efficiency should be lower than 5% in order to be consistent with radio data. This, however, relays on magnetic field estimates in the cluster. In particular, this implies that the contribution to the diffuse extragalactic gamma-ray background due to the high-energy photons from structure formation processes in clusters of galaxies is negligible, below 1%. Finally, we discuss detectability prospects for Astro-H, Fermi after 10 yr of operation, and the Cherenkov Telescope Array.

[28]
Title: Optical observations of the nearby galaxy IC342 with narrow band [SII] and H$α$ filters. I
Comments: 9 pages, 3 tables, 4 figures, accepted for publication in Serbian Astronomical Journal
Subjects: Galaxy Astrophysics (astro-ph.GA)

We present observations of the portion of the nearby spiral galaxy IC342 using narrow band [SII] and H$\alpha$ filters. These observations were carried out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper we report coordinates, diameters, H$\alpha$ and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 galaxy. The number of detected HII regions is 2.5 times higher than previously known in these two parts of the galaxy.

[29]
Title: Constraints on Helium Enhancement in the Globular Cluster M4 (NGC 6121): The Horizontal Branch Test
Subjects: Galaxy Astrophysics (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance ($Y$) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different $Y$ values. Comparing the photometric data with the theoretically-derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have $\Delta Y \lesssim 0.01$ with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)-- a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

[30]
Title: GLAMER Part II: Multiple Plane Gravitational Lensing
Comments: 14 pages, 10 figures, submitted to MNRAS
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present an extension to multiple planes of the gravitational lensing code {\small GLAMER}. The method entails projecting the mass in the observed light-cone onto a discrete number of lens planes and inverse ray-shooting from the image to the source plane. The mass on each plane can be represented as halos, simulation particles, a projected mass map extracted form a numerical simulation or any combination of these. The image finding is done in a source oriented fashion, where only regions of interest are iteratively refined on an initially coarse image plane grid. The calculations are performed in parallel on shared memory machines. The code is able to handle different types of analytic halos (NFW, NSIE, power-law, etc.), haloes extracted from numerical simulations and clusters constructed from semi-analytic models ({\small MOKA}). Likewise, there are several different options for modeling the source(s) which can be distributed throughout the light-cone. The distribution of matter in the light-cone can be either taken from a pre-existing N-body numerical simulations, from halo catalogs, or are generated from an analytic mass function. We present several tests of the code and demonstrate some of its applications such as generating mock images of galaxy and galaxy cluster lenses.

[31]
Title: On the nature of the WO3 star DR1 in IC 1613
Comments: Massive Stars: From {\alpha} to {\Omega}, held 10-14 June 2013 in Rhodes, Greece; Online at this http URL, id.187
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present the results of a quantitative spectroscopic analysis of the oxygen-sequence Wolf- Rayet star DR1 in the low-metallicity galaxy IC 1613. Our models suggest that the strong oxygen emission lines are the result of the high temperature of this WO3 star and do not necessarily reflect a more advanced evolutionary stage than WC stars.

[32]
Title: A Magnified View of the Kinematics and Morphology of RCSGA 032727-132609: Zooming in on a Merger at z=1.7
Authors: Eva Wuyts (1), Jane R. Rigby (2), Michael D. Gladders (3,4), Keren Sharon (5) ((1) Max Planck Institute for Extraterrestrial Physics, (2) NASA Goddard Space Flight Center, (3) University of Chicago, (4) Kavli Institute for Cosmological Physics, (5) University of Michigan)
Comments: 22 pages, 16 figures, accepted to ApJ
Subjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present a detailed analysis of multi-wavelength HST/WFC3 imaging and Keck/OSIRIS near-IR AO-assisted integral field spectroscopy for a highly magnified lensed galaxy at z=1.70. This young starburst is representative of UV-selected star-forming galaxies (SFG) at z~2 and contains multiple individual star-forming regions. Due to the lensing magnification, we can resolve spatial scales down to 100pc in the source plane of the galaxy. The velocity field shows disturbed kinematics suggestive of an ongoing interaction, and there is a clear signature of a tidal tail. We constrain the age, reddening, SFR and stellar mass of the star-forming clumps from SED modelling of the WFC3 photometry and measure their H-alpha luminosity, metallicity and outflow properties from the OSIRIS data. With strong star formation driven outflows in four clumps, RCSGA0327 is the first high redshift SFG at stellar mass <10^10 M_sun with spatially resolved stellar winds. We compare the H-alpha luminosities, sizes and dispersions of the star-forming regions to other high-z clumps as well as local giant HII regions and find no evidence for increased clump star formation surface densities in interacting systems, unlike in the local Universe. Spatially resolved SED modelling unveils an established stellar population at the location of the largest clump and a second mass concentration near the edge of the system which is not detected in H-alpha emission. This suggests a picture of an equal-mass mixed major merger, which has not triggered a new burst of star formation or caused a tidal tail in the gas-poor component.

[33]
Title: Off-center observers versus supernovae in inhomogeneous pressure universes
Comments: 20 pages, 4 figures, AAS LATEX 5.2
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Exact luminosity distance and apparent magnitude formulas are applied to Union2 557 supernovae sample in order to constrain possible position of an observer outside of the center of symmetry in spherically symmetric inhomogeneous pressure Stephani universes which are complementary to inhomogeneous density Lema\^itre-Tolman-Bondi (LTB) void models. Two specific models are investigated. The first which allows a barotropic equation of state at the center of symmetry with no scale factor function being specified (model IIA), and the second which has no barotropic equation of state at the center, but has an explicit dust-like scale factor evolution (model IIB).
It is shown that even at $3\sigma$ CL, an off-center observer cannot be further than about 3-4 Gpc away from the center of symmetry which is comparable to the reported size of a void in LTB models with the most likely value of the distance from the center about 270 Mpc for Model IIA. The off-center observer cannot be farther away from the center than about 400 Mpc for model IIB. It is evaluated that the parameters which characterize inhomogeneity are: most likely value of $\Omega_{inh} = 0.74$ (model IIA) and $-4.3 \cdot 10^{-8} < \alpha < 3.2 \cdot 10^{-8}$ (model IIB).
It is worth emphasizing that the test is based on supernovae data only, and the restrictions for a position of the observer may become stronger if other cosmological tests such as the CMB shift parameter, baryon acoustic oscillations, and the redshift drift are taken into account.

[34]
Title: Feasibility Studies for the Detection of $O_2$ in an Earth-like Exoplanet
Authors: Florian Rodler (CfA), Mercedes Lopez-Morales (CfA)
Comments: Accepted for publication in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present the results of simulations on the detectability of $O_2$ in the atmosphere of Earth twins around nearby low mass stars using high resolution transmission spectroscopy. We explore such detectability with each of the three upcoming Extremely Large Telescopes (ELTs), i.e. GMT, TMT and E-ELT, and high resolution spectrographs, assuming such instruments will be available in all ELTs. With these simulations we extend previous studies by taking into account atmospheric refraction in the transmission spectrum of the exo-Earth and observational white and red noise contributions. Our studies reveal that the number of transits necessary to detect the $O_2$ in the atmosphere of an Earth twin around M-dwarfs is by far higher than the number of transits estimated by Snellen et al. (2013). In addition, our simulations show that, when accounting for typical noise levels associated to observations in the optical and near-infrared, the $O_2$ A-band at 760 nm is more favorable to detect the exoplanetary signal than the $O_2$ band at 1268 nm for all the spectral types, except M9V. We conclude that, unless unpredicted instrumental limitations arise, the implementation of pre-slit optics such as image slicers appear to be key to significantly improve the yield of this particular science case. However, even in the most optimistic cases, we conclude that the detection of $O_2$ in the atmosphere of an Earth twin will be only feasible with the ELTs if the planet is orbiting a bright close-by (d $\le$ 8 pc) M-dwarf with a spectral type later than M3.

[35]
Title: Recent results in cosmic ray physics and their interpretation
Authors: Pasquale Blasi (INAF/Arcetri and GSSI)
Comments: Invited Plenary Review Talk at the 33rd International Cosmic Ray Conference (ICRC), 2013, Rio de Janeiro, Brazil
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The last decade has been dense with new developments in the search for the sources of Galactic cosmic rays. Some of these developments have confirmed the tight connection between cosmic rays and supernovae in our Galaxy, through the detection of gamma rays and the observation of thin non-thermal X-ray rims in supernova remnants. Some other, such as the detection of features in the spectra of some chemicals opened new questions on the propagation of cosmic rays in the Galaxy and on details of the acceleration process. Here I will summarize some of these developments and their implications for our understanding of the origin of cosmic rays. I will also discuss some new avenues that are being pursued in testing the supernova origin of Galactic cosmic rays.

[36]
Title: The Green Bank Telescope Maps the Dense, Star-Forming Gas in the Nearby Starburst Galaxy M82
Authors: Amanda A. Kepley (NRAO-GB), Adam K. Leroy (NRAO-CV), David Frayer (NRAO-GB), Antonio Usero (Observatorio Astronomico Nacional), Josh Marvil (New Mexico Tech and NRAO-Socorro), Fabian Walter (MPIA)
Comments: 7 pages, 4 figures, 1 table, accepted to ApJL
Subjects: Galaxy Astrophysics (astro-ph.GA)

Observations of the Milky Way and nearby galaxies show that dense molecular gas correlates with recent star formation, suggesting that the formation of this gas phase may help regulate star formation. A key test of this idea requires wide-area, high-resolution maps of dense molecular gas in galaxies to explore how local physical conditions drive dense gas formation, but these observations have been limited because of the faintness of dense gas tracers like HCN and HCO+. Here we demonstrate the power of the Robert C. Byrd Green Bank Telescope -- the largest single-dish millimeter radio telescope -- for mapping dense gas in galaxies by presenting the most sensitive maps yet of HCN and HCO+ in the starburst galaxy M82. The HCN and HCO+ in the disk of this galaxy correlates with both recent star formation and more diffuse molecular gas and shows kinematics consistent with a rotating torus. The HCO+ emission extending to the north and south of the disk is coincident with the outflow previously identified in CO and traces the eastern edge of the hot outflowing gas. The central starburst region has a higher ratio of star formation to dense gas than the outer regions, pointing to the starburst as a key driver of this relationship. These results establish that the GBT can efficiently map the dense molecular gas at 90 GHz in nearby galaxies, a capability that will increase further with the 16 element feed array under construction.

[37]
Title: La Silla QUEST RR Lyrae Star Survey: Region I
Subjects: Galaxy Astrophysics (astro-ph.GA)

A search for RR Lyrae stars (RRLS) in 840 sq.deg. of the sky in right ascension 150 - 210 deg and declination -10 - +10 deg yielded 1013 type ab and 359 type c RRLS. This sample is used to study the density profile of the Galactic halo, halo substructures, and the Oosterhoff type of the halo over distances from 5 to 80 kpc. The halo is flattened towards the Galactic plane, and its density profile steepens in slope at galactocentric distances greater than 25 kpc. The RRLS in the stellar stream from the Sagittarius dwarf spheroidal (dSph) galaxy match well the model of Law and Majewski for the stars that were stripped 1.3 to 3.2 Gyr ago, but not for the ones stripped 3.2 to 5.0 Gyr ago. Over densities are found at the locations of the Virgo Overdensity and the Virgo Stellar Stream. Within 1 deg of 1220-1, which Jerjen et al. identify as a halo substructure at a distance of 24 kpc, there are 4 RRLS that are possibly members. Away from substructures, the RRLS are a mixture of Oosterhoff types I and II, but mostly OoI (73%). The accretion of galaxies resembling in RRLS content the most massive Milky Way satellites (LMC, SMC, For,Sgr) may explain this preponderance of OoI. Six new RRLS and 3 new anomalous Cepheids were found in the Sextans dSph galaxy.

[38]
Title: US and European Technology Roadmap for a Mid-infrared Space Interferometer
Comments: 2 pages; proceedings of workshop "Pathways Towards Habitable Planets" held 14 to 18 September 2009 in Barcelona, Spain
Journal-ref: ASP Conference Series, vol. 430 (2010), p.536
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Studies of mid-infrared space interferometer concepts in the USA and in Europe have converged on a single architecture. We address the question of how the US and European communities could collaborate to advance technology efforts leading to a future space mission. We present the current state of the art in nulling interferometry, as demonstrated at ambient temperature and pressure in the lab, and outline required steps to demonstrate its performance under space conditions. Design studies of a cryogenic optical test bench under vacuum have already been carried out. We highlight pre-conditions and constraints of a collaborative effort, foreseeable practical and administrative challenges, and possible strategies to meet those challenges.

[39]
Title: The ACS survey of globular clusters. XIII. Photometric calibration in comparison with Stetson standards
Comments: 28 pages, 14 figures, accepted for publication in ApJS
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Galaxy Astrophysics (astro-ph.GA)

In this study we compare the photometric data of 34 Milky Way globular clusters, observed within the ACS Treasury Program (PI: Ata Sarajedini) with the corresponding ground-based data, provided by the Photometric Standard Field Catalogs of Stetson (2000, 2005). We focus on the transformation between the HST/ACS F606W to V-band and F814W to I-band only. The goal is to assess the validity of the filter transformation equations by Sirianni et al.(2005) with respect to their dependence on metallicity, Horizontal Branch morphology, mass and integrated (V-I) colour of the various globular clusters. Such a dependence is expected due to the fact that the transformation equations are based on the observations of only one globular cluster, i.e., NGC 2419. Surprisingly, the correlation between offset and metallicity is found to be weak, with a low level significance. The correlation between offset and Horizontal Branch structure, as well as total cluster mass is still weaker. Based on the available data we do not find the photometric offset to be linked to multiple stellar populations, e.g., as found in NGC 0288, NGC 1851, and NGC 5139. The results of this study show that there are small systematic offsets between the transformed ACS- and observed ground based photometry, and that these are only weakly correlated, if at all, with various cluster parameters and their underlying stellar populations. As a result, investigators wishing to transform globular cluster photometry from the Sirianni et al.(2005) ground-based V, I system onto the Stetson (2000) system simply need to add 0.040 (+/-0.012) to the V-band magnitudes and 0.047 (+/-0.011) to the I-band magnitudes. This in turn means that the transformed ACS (V-I) colours match the ground-based values from Stetson (2000) to within ~0.01 mag.

[40]
Title: Shell galaxies: kinematical signature of shells, satellite galaxy disruption and dynamical friction
Authors: Ivana Ebrova
Comments: PhD thesis, the thesis puls videos at: this http URL
Subjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Stellar shells observed in many giant elliptical and lenticular as well as a few spiral and dwarf galaxies presumably result from radial minor mergers of galaxies. We show that the line-of-sight velocity distribution of the shells has a quadruple-peaked shape. We found simple analytical expressions that connect the positions of the four peaks of the line profile with the mass distribution of the galaxy, namely, the circular velocity at the given shell radius and the propagation velocity of the shell. The analytical expressions were applied to a test-particle simulation of a radial minor merger, and the potential of the simulated host galaxy was successfully recovered. Shell kinematics can thus become an independent tool to determine the content and distribution of dark matter in shell galaxies up to ~100 kpc from the center of the host galaxy. Moreover we investigate the dynamical friction and gradual disruption of the cannibalized galaxy during the shell formation in the framework of a simulation with test particles. The coupling of both effects can considerably redistribute positions and luminosities of shells. Neglecting them can lead to significant errors in attempts to date the merger in observed shell galaxies.

[41]
Title: Collision Avoidance in Next-generation Fiber Positioner Robotic System for Large Survey Spectrograph
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Some of the next generation massive spectroscopic survey projects, such as DESI and PFS, plan to use thousands of fiber positioner robots packed at a focal plane to quickly move in parallel the fiber-ends from the previous to the next target points. The most direct trajectories are prone to collision that could damage the robots and impact the survey operation. We thus present here a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber positioners. The navigation function takes into account the configuration of positioners as well as the actuator constraints. We provide details for the proof of convergence and collision avoidance. Decentralization results in linear complexity for the motion planning as well as dependency of motion duration with respect to the number of positioners. Therefore the coordination method is scalable for large-scale spectrograph robots. The short in-motion duration of positioner robots (~2.5 seconds using typical actuator constraints), will thus allow the time dedicated for observation to be maximized.

[42]
Title: The optical rebrightening of GRB100814A: an interplay of forward and reverse shocks?
Comments: 27 pages, 8 figures, 5 tables. Submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a wide dataset of gamma-ray, X-ray, UVOIR, and radio observations of the Swift GRB100814A. At the end of the slow decline phase of the X-ray and optical afterglow, this burst shows a sudden and prominent rebrightening in the optical band only, followed by a fast decay in both bands. The optical rebrightening also shows chromatic evolution. Such a puzzling behaviour cannot be explained by a single component model. We discuss other possible interpretations, and we find that a model that incorporates a long-lived Reverse Shock and Forward Shock fits the temporal and spectral properties of GRB100814 the best. We also touch upon other GRBs presenting a behaviour similar to that of GRB100814A, such as GRB081029 and GRB100621A.

[43]
Title: Direct Measurement of Interstellar Extinction Toward Young Stars Using Atomic Hydrogen Lyman-$α$ Absorption
Interstellar reddening corrections are necessary to reconstruct the intrinsic spectral energy distributions (SEDs) of accreting protostellar systems. The stellar SED determines the heating and chemical processes that can occur in circumstellar disks. Measurement of neutral hydrogen absorption against broad Lyman-$\alpha$ emission profiles in young stars can be used to obtain the total H I column density (N(H I)) along the line of sight. We measure N(H I) with new and archival ultraviolet observations from the Hubble Space Telescope ($HST$) of 31 classical T Tauri and Herbig Ae/Be stars. The H I column densities range from log$_{10}$(N(H I)) $\approx 19.6 - 21.1$, with corresponding visual extinctions of A$_{V}$ $= 0.02 - 0.72$ mag, assuming an R$_{V}$ of 3.1. We find that the majority of the H I absorption along the line of sight likely comes from interstellar rather than circumstellar material. Extinctions derived from new $HST$ blue-optical spectral analyses, previous IR and optical measurements, and new X-ray column densities on average overestimate the interstellar extinction toward young stars compared to the N(H I) values by $\sim 0.6$ mag. We discuss possible explanations for this discrepancy in the context of a protoplanetary disk geometry.