%0 Generic %1 berry2013damped %A Berry, Michael %A Somerville, Rachel S. %A Haas, Marcel R. %A Gawiser, Eric %A Maller, Ari %A Popping, Gergo %A Trager, Scott C. %D 2013 %K distribution dla hi sam %T Damped Ly\alpha Absorption Systems in Semi-Analytic Models with Multiphase Gas %U http://arxiv.org/abs/1308.2598 %X We investigate the properties of damped Ly\alpha absorption systems (DLAs) in semi-analytic models of galaxy formation, including partitioning of cold gas in galactic discs into atomic, molecular, and ionized phases with a molecular gas-based star formation recipe. We investigate two approaches for partitioning gas into these constituents: a pressure-based and a metallicity-based recipe. We identify DLAs by passing lines of sight through our simulations to compute HI column densities. We find that models with "standard" gas radial profiles - where the average specific angular momentum of the gas disc is equal to that of the host dark matter halo - fail to reproduce the observed column density distribution of DLAs. These models also fail to reproduce the distribution of velocity widths \Deltav, overproducing low \Deltav relative to high \Deltav systems. Models with "extended" radial gas profiles - corresponding to gas discs with higher specific angular momentum - are able to reproduce quite well the column density distribution of absorbers over the column density range 19 < log NHI < 22.5 in the redshift range 2 < z < 3.5. The model with pressure-based gas partitioning also reproduces the observed line density of DLAs, HI gas density, and \Deltav distribution at z < 3 remarkably well. However all of the models investigated here underproduce DLAs and the HI gas density at z > 3. If this is the case, the flatness in the number of DLAs and HI gas density over the redshift interval 0 < z < 5 may be due to a cosmic coincidence where the majority of DLAs at z > 3 arise from intergalactic gas in filaments while those at z < 3 arise predominantly in galactic discs. We further investigate the dependence of DLA metallicity on redshift and \Deltav, and find reasonably good agreement with the observations, particularly when including the effects of metallicity gradients (abbrv.).

@misc{berry2013damped, abstract = {We investigate the properties of damped Ly{\alpha} absorption systems (DLAs) in semi-analytic models of galaxy formation, including partitioning of cold gas in galactic discs into atomic, molecular, and ionized phases with a molecular gas-based star formation recipe. We investigate two approaches for partitioning gas into these constituents: a pressure-based and a metallicity-based recipe. We identify DLAs by passing lines of sight through our simulations to compute HI column densities. We find that models with "standard" gas radial profiles - where the average specific angular momentum of the gas disc is equal to that of the host dark matter halo - fail to reproduce the observed column density distribution of DLAs. These models also fail to reproduce the distribution of velocity widths {\Delta}v, overproducing low {\Delta}v relative to high {\Delta}v systems. Models with "extended" radial gas profiles - corresponding to gas discs with higher specific angular momentum - are able to reproduce quite well the column density distribution of absorbers over the column density range 19 < log NHI < 22.5 in the redshift range 2 < z < 3.5. The model with pressure-based gas partitioning also reproduces the observed line density of DLAs, HI gas density, and {\Delta}v distribution at z < 3 remarkably well. However all of the models investigated here underproduce DLAs and the HI gas density at z > 3. If this is the case, the flatness in the number of DLAs and HI gas density over the redshift interval 0 < z < 5 may be due to a cosmic coincidence where the majority of DLAs at z > 3 arise from intergalactic gas in filaments while those at z < 3 arise predominantly in galactic discs. We further investigate the dependence of DLA metallicity on redshift and {\Delta}v, and find reasonably good agreement with the observations, particularly when including the effects of metallicity gradients (abbrv.).}, added-at = {2013-08-13T07:14:41.000+0200}, author = {Berry, Michael and Somerville, Rachel S. and Haas, Marcel R. and Gawiser, Eric and Maller, Ari and Popping, Gergo and Trager, Scott C.}, biburl = {https://www.bibsonomy.org/bibtex/201b34b0008fe9fe297134e76635fbb4c/miki}, description = {[1308.2598] Damped Ly{\alpha} Absorption Systems in Semi-Analytic Models with Multiphase Gas}, interhash = {01fee1fcc0a2fb1a96f741b4aa647ccd}, intrahash = {01b34b0008fe9fe297134e76635fbb4c}, keywords = {distribution dla hi sam}, note = {cite arxiv:1308.2598Comment: 27 pages, 15 figures, submitted to MNRAS}, timestamp = {2013-08-13T07:14:41.000+0200}, title = {Damped Ly{\alpha} Absorption Systems in Semi-Analytic Models with Multiphase Gas}, url = {http://arxiv.org/abs/1308.2598}, year = 2013 }