Day 533

Tuesday, in Rome.

1310.4832
The Andromeda optical and infrared disk survey
Sick, Courteau, Cuillandre

The survey has mapped M31 in u*g'r'i' J Ks out to R=40 kpc on CFHT.  Survey designed to simultaneously resolve stars while also reproducing the surface brightness of M31, allowing study of M31's global structure in the context of both resolved stellar populations and SEDs.  Calibrate photometry via mapping u*g'r'i' sky background with sky-target nodding.  Maps are stable, and reveal warps in the outer M31 disk in surface brightness.  The equivalent mapping in NIR uses a combination of sky-target nodding and image-to-image sky offset optimization to produce stable surface brightnesses.  This study enables a detailed analysis of the systematics of SED fitting with NIR bands where asymptotic giant branch stars impose a significant, but ill-constrained, contribution to the NIR light of a galaxy.  Present panchromatic surface brightness maps and initial results from the NIR resolved stellar catalog.

1310.4835
Ly{\alpha} equivalent width distribution at redsfhit z $\sim$ 4.5
Zheng, et al

Lya EWs provide clues to the physical nature of nigh-z LAEs; but measuring EW distribution of high-z narrowband selected LAEs are difficult because many sources do not have broadband photometry.  Investigate possible biases in measuring the intrinsic Lya EW distribution for LAE sample at z~4.5 in the Extended Chandra Deep Field South (ECDFS).  Only weak Malmquist-type bias in both the intrinsic Lya LF and the EW distribution were found.  However, the observed EW distribution is severely biased if one only considers LAEs with detections in the continuum.  Taking the broadband non-detections into account requires fitting the distribution of the broadband-to-narrowband ratio, which then gives a larger EW distribution scale length.  Assuming an exponential-form distribution of the EW, obtain constant of W_0 = 167pm44A (uncorrected for IGM absorption of Lya).  Discuss the likely range of IGM absorption effects in light of recent measurements of Lya line profiles and velocity offsets.  Data consistent with Lya EW being independent of UV luminosity.  Simulations also imply that broad-band images should be 0.5-1 magnitude deeper than narrowband images for an effective and reasonably complete LAE survey.  Comparing with consistent measurements at other redshifts, see a strong evolution in Lya EW distribuiton with redshift which goes as a power-law form of (1+z)^xi, with xi=1.7pm0.1 if no IGM corrections are applied to the Lya line, or xi=2.2pm0.1 after applying maximal IGM-absorption correction to Lya, from z=0.3 to 6.5.

1310.4841
Swansong biospheres II: the final signs of life on terrestrial planets near the end of their habitable lifetimes
O'Malley-James et al

As the title says---it will likely consist of predominantly unicellular microorganisms due to thei ncreased hostility of environmental conditions caused by the Sun as it enters the late state of its MS evolution.

1310.4842
Dust may be more rare than expected in metal poor galaxies
Fisher et al

[Nature paper]  Low-dust examples: Himiko at z=6.6, and a local galaxy I Zw 18.  Report observations of dust emission from I Zw 18, estimate dust mass to be 450-1800 Msun, yielding a dust-to-stellar mass ratio of 1e-6 to 1e-5 and a dust-to-gas mass ratio 3.2-13e-6.  If I Zw 18 is a reasonable analog of Himiko, then Himiko's dust mass is ~50k Msun, a factor of 100 below the current upper limit.  These numbers are considerably uncertain, but if most high-z galaxies are more like Himiko than like the quasar host SDSS J114816.64+525150.3, then the prospects for detecting the gas and dust in them are much poorer than hitherto anticipated.

1310.4925
Halo/galaxy bispectrum with primordial non-Gaussianity from integrated perturbation theory (iPT)
Yokoyama, Matsubara, Taruya

Derive a formula for the halo/galaxy bispectrum on the basis of the iPT.  In addition to the gravity-induced non-Gaussianity, consider the non-Gaussianity of the primordial curvature perturbations, and investigate in detail the effect of such primordial non-Gaussianity on the large-scale halo/galaxy bispectrum.  In iPT, the effects of primordial non-Gaussianity are wholly encapsulated in the linear (primordial) polyspectra; systematically calculate the contributions to the large-scale behaviors arising from the three types of primordial bispectrum (local-, equilateral-, and orthogonal-types), and primordial trispectrum of the local-type non-Gaussianity.  Find that the equilateral- and orthogonal-type non-Gaussianities show distinct scale-dependent behaviors which can dominate the gravity-induced non-Gaussianity at very large scales.  For the local-type non-Gaussianity, higher-order loop corrections are found to give a significantly large contribution to the halo/galaxy bispectrum of the squeezed shape, and eventually dominate over the other contributions on large scales.  A diagrammatic approach based on the iPT helps to systematically investigate an impact of such higher-order contributions to the large-scale halo/galaxy bispectrum.

1310.4932
Chemo-dynamical simulations of dwarf galaxy evolution
Recchi

A summary review of the state-of-the-art of chemo-dynamical numerical modelling of galaxies in general, and of dwarf galaxies in particular.  Pay attention to: (i) initial conditions; (ii) the equations to solve; (iii) the SF process in galaxies; (iv) the initial mass function; (v) the chemical feedback; (vi) the mechanical feedback; (vii) the environmental effects.  Additionally: key results on galactic winds in galaxies, and the fate of heavy elements, freshly synthesized after an episode of SF.  Summarize the topics and physical processes, relevant for evolution of galaxies, which are not properly treated in modern simulations (in the author's opinion), and deserve more attention in the future.

1310.4944
Are ultra-long gamma-ray bursts different?
Boer, Gendre, Stratta

Discovery of numbers of gamma-ray bursts with >1000 seconds, with one case with 25k seconds, open the question on whether these bursts form a new class of sources: "ultra-long GRBs", or if they form the tail of the long GRB duration distribution.  Investigate statistical properties of these GRBs and compare with the overall long burst population.  Discuss differences observed in their spectral properties.  Find that ultra-long GRBs are statistically different form standard long GRBs with typical burst duration <100-500 seconds, for which a Wolf Rayet star progenitor is usually invoked.  Interpret this result as an indication that an alternative scenario has to be found in order to explain the ultra-long GRB extreme energetics, as well as the mass reservoir and its size that can feed the central engine for such a long time.
1310.4950
The FMOS-Cosmos survey of star-forming galaxies at z~1.6 II. the mass-metallicity relation and the dependence on star formation rate and dust extinction
Zahid et al

Investigate the relationship between stellar mass, gas-phase oxygen abundance (metallicity), SFR, and dust content of SF galaxies at z~1.6 using Subaru/FMOS spectroscopy in COSMOS.  The mass-metallicity relation at z~1.6 is significantly steeper than the relation observed in the local Universe.  The most massive galaxies at z~1.6 (1e11 Msun) are enriched to the level observed in massive galaxies in the local Universe.  The mass-metallicity relation measured at z~1.6 supports the suggestion of an empirical upper metallicity limit that does not significantly evolve with redshift.  Find an anti-correlation between metallicity and SFR of galaxies at a fixed stellar mass at z~1.6 which is similar to trends observed in the local Universe.  Do not find a relation between stellar mass, metallicity and SFR that is independent of redshift; data suggest that there is redshift evolution in this relation.  Examine the relation between stellar mass, metallicity and dust extinction  Find that at a fixed stellar mass dustier galaxies tend to be more metal rich.  From examination of the stellar masses, metallicities, SFRs and dust extinctions, conclude that stellar mass is most closely related to dust extinction.

1310.5102
A new framework for numerical simulations of structure formation
Shaller et al

Numerical cosmological simulations use "coarse-graining" methods to deal with the large number of particles whose interaction must be simulated; there is no closed system of equations for the evolution of the matter density field alone and instead it should still be discretized at each timestep.  This work describes a method of solving the full 6-dimensional Vlasov-Poisson equation via a system of auxiliary Schroedinger-like equations.  The complexity of problem gets shifted into the choice of the number and shape of the initial wavefunctions that should only be specified at the beginning of the computation (these wavefunctions have nothing todo with the quantum nature of the actual DM particles).  Discuss different prescriptions to generate the initial wave functions from the initial conditions, and demonstrate the validity of the technique on two simple test cases.  This new simulation algorithm can in principle be used on an arbitrary distribution function, enabling the simulation of warm and hot dark matter structure formation scenarios.