Day 960

Friday.


1509.00853
The impact of stellar feedback on the structure, size and morphology of galaxies in Milky Way size dark matter haloes
Agertz, Kravsov

Use cosmo zoom-in sims of galaxy formation in MW-sized halo started from identical initial conditions to investigate the evolution of galaxy sizes, baryon fractions, morphologies and angular momenta in runs with different parameters of the star formation--feedback cycle.  The fiducial model with a high local SF efficiency, which results in efficient feedback, produces a realistic late-type galaxy that matches the evolution of basic properties of late-type galaxies: stellar mass, disk size, morphology dominated by kinematically cold disk, stellar and gas surface density profiles, and specific angular momentum.  Argue that feedback's role in this success is twofold: (1) removal of low-angular momentum gas and (2) maintaining a low disk-to-halo mass fraction which suppresses disk instabilities that lead to angular momentum redistribution and a central concentration of baryons.  However, the model with a low local star formation efficiency, but large energy input per supernova, chosen to produce a galaxy with a similar SFH as the fiducial model, leads to a highly irregular galaxy with no kinematically cold component, overly extended stellar distribution and low angular momentum.  This indicates that only when feedback is slowed to become vigorous via locally efficient SF in dense cold gas, resulting galaxy sizes, gas/stellar surface density profiles and stellar disk angular momenta agree with observed z=0 galaxies.


1509.00870
Assessing galaxy limiting magnitudes in large optical surveys
Rykoff, Rozo, Keisler

Large scale structure measurements require accurate and precise knowledge of the survey depth --- typically expressed in the form of a limiting magnitude --- as a function of position on the sky.  To date, most surveys only compute the point-source limiting magnitude measured within a fixed metric aperture.  However, this quantity is ill suited to describe the limiting depth of galaxies, which depends on the detailed interplay of survey systematics with galaxy shapes and sizes.  Describe an empirical method for directly estimating the limiting magnitude for large photometric surveys, and apply it to ~10,000 deg2 of SDSS DR8 data.  Combined with deeper imaging from SDSS Stripe 82 and CFHTLenS, able to use these depth maps to estimate the location-dependent galaxy detection completeness at any point within the full BOSS DR8 survey region.  Show that these maps can be used to construct random points suitable for unbiased estimation of correlation functions for galaxies near the survey limiting magnitude.  Finally, provide limiting magnitude maps for galaxies in SDSS DR8 in HEALPix format with NSIDE=2048.