Day 1015

Wednesday.


1512.00007
The number of tidal dwarf satellite galaxies in dependence of bulge index
Lopez-Corredora, Krupa

Show that a significant correlation (up to 5 sigma) emerges between the bulge index, defined to be larger for larger bulge/disk ratio, in spiral galaxies with similar luminosities in the Galaxy Zoo 2 of SDSS and the number of tidal-dwarf galaxies in the catalogue by Kaviraj+2012.  In the standard cold or warm DM cosmological models the number of satellite galaxies correlates with the circular velocity of the DM host halo.  In generalized-gravity models without cold or warm DM such a correlation does not exist, because those galaxies cannot capture in-falling dwarf galaxies due to the absence of DM-induced dynamical friction.  However, in such models a correlation is expected to exist between the bulge mass and the number of satellite galaxies, because bulges and tidal-dwarf satellite galaxies form in encounters between host galaxies.  This is not predicted by DM models in which bulge mass and the number of satellites are a priori uncorrelated because higher bulge/disk ratios do not imply higher dark/luminous ratios.  Hence, the correlation reproduces the prediction of scenarios without DM, whereas an explanation is not found readily from the a priori predictions of the standard scenario with DM.  Further research is needed to explore whether some application of the standard theory may explain this correlation.


1512.00008
The galaxy correlation function as a constraint on galaxy formation physics
van Daalen, Henriques, Angulo, White

Introduce methods which allow observed galaxy clustering to be used together with observed luminosity or stellar mass functions to constrain the physics of galaxy formation.  Show how the projected 2-pt correlation function of galaxies in a large semi-analytic simulation can be estimated to better than ~10% using only a very small subsample of the sub halo merger trees.  This allows measured correlation to be used as constraints in a MCMC exploration of the astrophysical and cosmological parameter space.  An important part of the scheme is an analytic profile which captures the simulated satellite distribution extremely well out to several halo viral radii.  This is essential to reproduce the correlation properties of the full simulation at intermediate separations.  As a first application, use low-redshift clustering and abundance measurements to constrain a recent version of the Munich SAM.  The preferred values of most parameters are consistent with those found previously, with significantly improved constraints and somewhat shifted "best" values for parameters that primary affect spatial distributions.  The methods allow multi-epoch data on galaxy clustering and abundance to be used as joint constraints on galaxy formation.  This may lead to significant constraints on cosmo parameters even after marginalizing over galaxy formation physics.  


1512.00086
The evolution of the intergalactic medium
McQuinn

[Review.] The bulk of cosmic matter resides in a dilute reservoir that fills the space between galaxies, the intergalactic medium (IGM).  The history of the reservoir is intimately tied to the cosmic histories of structure formation, SF, and SMBH accretion.  The models for the IGM at intermediate redshifts (2<z<5) are a tremendous success, quantitatively explaining the statistics of Lyman-alpha absorption of intergalactic hydrogen.  However, at both lower and higher redshifts (and around galaxies) much is still unknown about the IGM.  Review the theoretical models and measurements that form the basis for the modern understanding of the IGM and discuss unsolved puzzles (ranging from the largely unconstrained process of reionization at high-z to the missing baryons problem at low-z), highlighting the efforts that have the potential to solve them.