Day 712

Wednesday.

1112.1956
Galaxy and mass assembly (GAMA): structural investigation of galaxies via model analysis (SIGMA)
Kelvin, ... et al

Present single Sérsic 2d model fits to 167k galaxies modeled independently in the ugrizYJHK bandpasses using SDSS DR7 and UKIDSS-LAS imaging data available from GAMA database.  Developed SIGMA, an R wrapper around several astronomy SW packages including SExtractor, PSF Extractor and GALFIT 3.  SIGMA produces realistic 2d model fits to galaxies, employing automatic adaptive BG subtraction and empirical PSF measurements on the fly for each galaxy in GAMA.  Using these results, define a common coverage area across the 3 GAMA regions containing 138k galaxies.  Provide Sersic magnitudes truncated at 10 re which show good agreement with SDSS Petrosian and GAMA photometry for low Sersic index systems (n<4), and much improved photometry for high Sersic index systems (n>4), recovering as much as Delta m=0.5 magnitudes in the r band.  Employ a K band Sersic index / u-r color relation to delineate the massive (n>~2) ETGs from the LTGs.  The mean Sersic index of these ETGs shows a smooth variation with wavelength, increasing by 30% from g through K.  LTGs exhibit a more extreme change in Sersic index, increasing by 52% across the same range.  In addition, ETGs and LTGs exhibit a 38% and 25% decrease respectively in HLR from g through K.  These trends are shown to arise due to the effects of dust attenuation and stellar population/metallicity gradients within galaxy populations.

1407.7545
Impact of population~III binaries on early cosmic evolution
Chen, Bromm, Heger, Jeon, Woosley

Present the results of the stellar feedback from Pop III binaries.  Consider a fixed mass of 60 Msun, either contained in a single star, or split up in binary stars of 30 Msun each, or asymmetric case of 45 Msun and 15 Msun.  Where as the sizes of the resulting HII regions are comparable across all cases, the HeIII regions around binary stars are significantly smaller than that of the single star.  Consequently, the He+ 1640 A recombination line is expected to become much weaker.  SN feedback exhibits great variety due to the uncertainty in possible explosion pathways.  If at least one of the component stars dies as a hyper nova about 10 times more energetic that conventional core-collapse SNe, the gas inside the host mini halo is effectively blown out, chemically enriching the IGM to an average metallicity of 1e-4 to 1e-3 Zsun, out to ~2 kpc.  The single star, however, is more likely to collapse into a BH, accompanied by at most very weak explosions.  The effectiveness of early chemical enrichment would thus be significantly reduced, in difference from the lower mass binary stars, where at least one component is likely to contribute to heavy element production and dispersal.  Important new feedback physics is also introduced if close binaries can form high-mass x-ray binaries, leading to the pre-heating and ionization of the IGM beyond the extent of the stellar HII regions.

1407.7555
Galaxy and mass assembly (GAMA): stellar mass functions by Hubble type
Kelvin, et al

Present an estimate of the galaxy stellar MF and its division by morphological type in the local (0.025<z<0.06) universe.  From a sample of 3727 galaxies from GAMA, define a local volume and stellar mass limited sub-sample of 2711 galaxies to a lower stellar mass limit of M=1e9Msun.  Confirm that the galaxy stellar MF is well described by a double Schechter function, with alpha1=-0.43 and alpha2=-1.50 (M*=1e10.6Msun, phi*1=4.1/dex/Mpc3, phi*2=0.74 /dex/Mpc3).  The constituent morphological-type stellar MFs are well sampled above the lower stellar mass limit, excepting the faint little blue spheroid population of galaxies.  Find approximately 71% of the stellar mass in the local Universe within spheroid dominated galaxies (ellipticals and S0-Sas).  The remaining 29% falls predominantly within late type disk dominated systems, Sab-Scds and Sd-Irrs.  Adopting reasonable bulge-to-total ratios implies that approximately half the stellar mass today resides in spheroidal structures, and half in disk structures.  Within this local sample, find approximate stellar mass proportions for E : S0-Sa : Sab-Scd : Sd-Irr of 34 : 37 : 24 : 5.

1407.7676
GalSim: the modular galaxy image simulation toolkit
Rowe, et al

GALSIM: SW library of generating images of astronomical objects such as stars and galaxies, efficiently handling image transformations and operations such as convolution and rendering at high precision.  Demonstrate that the performance of GALSIM meets the stringent requirements of high precision image analysis applications such as WL for current datasets and for the Stage IV DE surveys of LSST, Euclid, WFIRST-AFTA.  The GALSIM project repository is public and includes the full code history, all open and closed issues, installation instructions, documentation, and wiki pages.