Day 515

Wednesday.

1309.5950
On the connection between the intergalactic medium and galaxies: The HI-galaxy cross-correlation at z<1
Tejos et al

Optical spectroscopic survey of 1777 SF and 366 non-SF galaxies at z<1, 22 AGN and 423 stars, observed by DEIMOS< VIMOS and GMOS and 3 fields containing 5 QSOs with HST UV spectroscopy.  Also present new spectroscopic survey of 165 'strong' and 489 'weak) intervening HI absorption line systems at z<1, observed in the spectra of 8 QUSs by COS and FOS on the HST.  Combining these new data with previously published galaxy catalogs (VVDS and GDDS), gathered a sample of 654 HI absorption systems and 17509 galaxies at transverse scales <50 Mpc.  Present observational results on the HI-galaxy and galaxy-galaxy correlations at transverse scales r<10 Mpc, and the HI-HI- auto-correlation at transverse scales r<2 Mpc.  THe 2-pt correlation functions are measured both along and transverse to the LoS.  Constrain the HI-galaxy statistical connection, as a function of both HI column density and galaxy SF activity.  Results are consistent with the following conclusions: (1) the bulk of HI systems on Mpc scales have little velocity dispersion (<120 km/s) wrt the bulk of galaxies; (2) the vast majority of strong HI systems and SF galaxies are distributed in the same locations, together with 75pm15% of non-SF galaxies, all of which typically reside in DM halos of similar masses; (3) 25pm15% of non-SF galaxies reside in galaxy clusters and are not correlated with strong HI systems at scales <2Mpc; and (4) 50% of weak HI systems reside within galaxy voids (hence not correlated with galaxies), and are confined in DM haloes of masses smaller than those hosting...

1309.5951
Tracing inflows and outflows with absorption lines in circumgalactic gas
Ford, Dave, Oppenheimer, Katz, Kollmeier, Thompson, Weinberg

Examine how HI and metal absorption lines within low-z galaxy haloes trace the dynamical state of circumgalactic gas, using cosmological hydrodynamic simulations that include a well-vetted heuristic model for galactic outflows.  Categorize inflowing, outflowing and ambient gas based on its history and fate as tracked in the simulation.  Following earlier work showing that the ionisation level of absorbers was a primary factor in determining the physical conditions of absorbing gas, show here that it is also a governing factor for its dynamical state.  Low-ionisation metal absorbers (MgII) tend to arise in gas that will fall onto galaxies within several Gyr, while high-ionisation metal absorbers (OVI) generally trace material that was deposited by outflows many Gyrs ago.  Inflowing gas is dominated by enriched material that was previously ejected in an outflow, hence accretion at low redshifts is typically substantially enriched.  Recycling wind material is preferentially found closer to galaxies, and is more dominant in lower-mass haloes since high-mass haloes have more hot gas that is able to support itself against infall.  Low-mass haloes also tend to re-eject more of their accreted material, owing to their outflow prescription that employs higher mass loading factors for lower-mass galaxies.  Typical HI absorbers trace unenriched ambient material that is not participating in the baryon cycle, but stronger HI absorbers arise in cool, enriched inflowing gas.  Instantaneous radial velocity measures of absorbers are generally poor at distinguishing between inflowing and outflowing gas, except in the case of very recent outflows.  These results suggest that probing halo gas using a range of absorbers can provide detailed information about the amount and physical conditions of material that is participating in the baryon cycle.

1309.5955
Model breaking measure for cosmological surveys
Amara, Refregier

Another FoM that quantifies the capacity of future surveys to rule out the LCDM model: based on a measure of difference in volume of observable space that the future surveys will constrain with and without imposing the model.  This model breaking FoM is easy to compute and can lead to different survey optimizations than other metrics.  Illustrate its impact using a simple combination of supernovae and BAO mock observations and compare the respective merit of these probes to challenge LCDM.  Discuss how this approach would impact the design of future cosmological experiments.  

1309.5972
Galaxy stellar mass functions from ZFOURGE/CANDELS: an excess of low-mass galaxies since z=2 and the rapid buildup of quiescent galaxies
Tomszak, ... van Dokkum, et al

Deepest measurements to date of the galaxy stellar mass function at 0.5<z<2.5.  ZFOURGE provides well-constrained photo-z made possible through deep medium-bandwidth imaging at 1-2 um.  Combine this with HST imaging from CANDELS, allowing for the efficient selection of both blue and red galaxies down to stellar masses 1e9.5 Msun at z~2.5.  The total surveyed area is 316 arcmin^2 distributed over 3 independent fields.  Supplement these data with the wider and shallower NMBS to provide stronger constraints at high masses.  Several studies at z<=1 have revealed a steepening of the slope at the low-mass end of the stellar mass function, leading to an upturn at masses <1e10 Msun that is not well-described by a standard single-Schechter function.  Find evidence that this feature extends to at least z~2, and that it can be found in both the SF and quiescent populations individually.  The characteristic mass M* and slope at the lowest masses (alpha) of a double-Schechter function fit to the SMF stay roughly constant at log(M/Msun)~10.65 and ~-1.5, respectively.  The SMF of SF galaxies has evolved primarily in normalization, while the change in shape is relatively minor.  This is not the case for quiescent galaxies: the depth of imaging allows to show for the first time significantly more evolution at log(M/Msun)<10.5 than at higher masses.  Find that the total mass density (down to 1e9 Msun) in SF galaxies has increased by a factor of ~2.2 since z~2.5, whereas in quiescent galaxies it has increased by a factor of ~12.