Day 1052

Monday.


1602.05957
Reconciling dwarf galaxies with LCDM cosmology: simulating a realistic population of satellites around a Milky Way-mass galaxy
Wentzel, Hopkins, Kim, Faucher-Giguere, Keres, Quahaert

Low-mass "dwarf" galaxies represent the most significant challenges to the CDM model of cosmo structure formation.  Because these faint galaxies are (best) observed within the LG of the MW and M31, understanding their formation in such an environment is critical.  Present the first results from the Latte Project: the MW on FIRE (Feedback in Realistic Environments).  This simulation models the formation of a MW-mass galaxy to z=0 within LCDM cosmology, including DM, gas, and stars at unprecedented resolution: baryon mass of 7070 Msun at spatial resolution down to 1pc.  Latte was simulated using the GIZMO code with a mesh-free method for accurate hydrodynamics and the FIRE model for SF and explicit feedback within a multi-phase ISM.  For the first time, Latte self-consistently resolve the internal structure of dwarf galaxies that form around a MW-mass shot down to M*>1e5 Msun.  Latte's population of dwarf galaxies agrees well with hose observed in the LG across a broad range of properties:  (1) distributions of stellar masses and stellar velocity dispersions (dynamical masses), including their joint relation, (2) the mass-metallicity relation, and (3) a diverse range of SFHs, including their mass dependence.  Thus, Latte produces a realistic population of dwarf galaxies at M*>1e5 Msun that does not suffer from the "missing satellites" or "too big to fail" problems of small-scale structure formation.  Conclude that baryonic physics can reconcile observed dwarf galaxies with standard LCDM cosmology.


1502.05960
Hierarchical Bayesian inference of galaxy redshift distributions from photometric surveys
Listed, Mortlock, Peiris

Accurately characterizing the redshift distributions of galaxies is essential for analyzing deep photometric surveys and testing cosmo models.  Present a technique to simultaneously infer redshift distributions and individual redshifts from photometric galaxy catalogues.  The model constructs a piecewise constant representation (effectively a histogram) of the distribution of galaxy types and redshifts, the parameters of which are efficiently inferred from noisy photometric flux measurements.  This approach can be seen as a generalization of template-fitting photometric redshift methods and relies on a library of spectral templates to relate the photometric fluxes of individual galaxies to their redshifts.  Illustrate this technique on simulated galaxy survey data, and demonstrate that it delivers correct poster distributions on the underlying type and redshift distributions, as well as on the individual types and redshifts of galaxies.  Show that even with uninformative priors, large photometric errors and parameter degeneracies, the redshift and type distributions can be recovered robustly thanks to the hierarchical nature of the model, which is not possible with common photometric redshift estimation techniques.  As a result, redshift uncertainties can be fully propagated in cosmological analyses for the first time, fulfilling a essential requirement for the current and future generation of surveys.