Day 546

Friday.  Saturday.  Sunday.

1311.1816
The dependence of the galaxy mass-metallicity relation on environment and the implied metallicity of the IGM
Peng, Maiolino

Dependence of galaxy mass-metallicity relation on environment (over density and central/satellite dichotomy): find that at a given M*, there is a strong dependence of metallicity on over density for SF satellites.  Instead, for SF central, no correlation is found.  SF satellites at different stellar masses form a tight sequence in the average over density - metallicity plane, which covers the entire observed range of metallicities and stellar masses.  This results appears to imply that there exists a universal evolutionary path for all SF satellites, regardless of their stellar masses.  The strong correlation between over density and metallicity of SF satellites indicates that the gas inflow of satellite galaxies is progressively metal-enriched in denser regions.  Interpret results by employing the gas regulator model and find that the metallicity of the enriched inflow of SF satellite galaxies strongly increase with increasing over density, largely independently of stellar mass.  If the metallicity of the inflow of SF satellites can represent the metallicity of the IGM, then the implied metallicity of the IGM rises from ~0.01 solar metallicity in void-like environments to ~0.3 solar metallicity in cluster-like environments, in broad agreement with observations.  Show that the observed metallicity difference between SF centrals and SF satellites becoming smaller towards high stellar masses can be simply explained by the mass-independent enriched inflow, without the need to involve any mass-dependent environmental effect on metallicity.  Since satellite galaxies account for at least half of the galaxy population [really?  I guess if you include SF-ing satellites it's true?], this prompt for a revision of many galaxy evolutionary models, which generally assume pristine gas inflows.

1311.1818
The phantom menace of galaxy clustering: assembly bias and the galaxy-halo relationship
Zentner, Hearing, van den Bosch

HOD, CLF, etc assume halo mass alon suffices to determine a halo's resident galaxy population; but clustering strength of CDM halos also depends upon other halo properties, such as formation time (assembly bias).  If galaxy characteristics are correlated with any of these auxiliary halo properties, the basic assumption of HOD/CLF methods is violated.  Estimate the potential for assembly bias to induce systematic errors in inferred HO statistics.  Use halo abundance matching and age matching to construct fiducial mock galaxy catalogs that exhibit assembly bias as well as additional mock catalogs with identical HODs, but with assembly bias removed.  Fit a parameterized HOD to the projected 2pt clustering of mock galaxies in each catalog to assess the systematic errors induced by reasonable levels of assembly bias.  In the absence of assembly bias, the inferred HODs generally describe the there underlying HODs well, validating the basic methodology.  However, in all of the cases with assembly bias, the inferred HODs have systematic errors that are statistically significant.  In most cases, these systematic errors cannot be identified using void statistics as auxiliary observables.  Conclude that the galaxy-halo relationship inferred from galaxy clustering should be subject to a non-negligible systematic error induced by assembly bias.  Work suggests that efforts to model and/or constraint assembly bias should be high priorities as it is a threatening source of systematic error in galaxy evolution studies as well as the precision cosmology program.  

1311.1828
Infrared properties of z=7 galaxies from cosmological simulations
Cen, Kimm

3d panchromatic dust radiative transfer calculations on 198 galaxies of M* = 5e8 to 3e10 Msun from hydro-sim (resolved at 29 pc/h) at z=7.  Stellar mass, UV LF and UV-optical and FUV-NUV colors in good agreement with observations, if SMC-type dust extinction curve is adopted.  Predictions for z=7 galaxy properties observable with ALMA: (1) effective radius in the rest-fram MIPS 70 um band is in the range of 80-400 pc proper for z=7 galaxies with L_FIR=1e11.3-12 Lsun. (2) The median of the peak wavelength of the FIR SED is in the range of 45-60 um, depending on the dust-to-metal ratio.  (3) For SFR in the range 3-100 Msun/yr the median FIR to bolometric luminosity ratio is 60-90%.  (4) The FIR luminosity function displays a power law in the high end with a slope of -3.1 pm 0.4, instead of the usual exponential decline.

1311.2338
Can CMB lensing help cosmic shear surveys?
Das, Errard, Spergel

Answer is yes.  X-corr between the WL shear, galaxy number counts from galaxy redshift survey, and the CMB lensing convergence can be used to calibrate the shear multiplicative bias, not of the most challenging systematics in lensing surreys.  These X-correlations can significantly reduce the effects of the uncertainties in multiplicative bias.