ترغب بنشر مسار تعليمي؟ اضغط هنا

The Growth of Red Sequence Galaxies in a Cosmological Hydrodynamic Simulation

234   0   0.0 ( 0 )
 نشر من قبل Jared Gabor
 تاريخ النشر 2012
  مجال البحث فيزياء
والبحث باللغة English
 تأليف J. M. Gabor




اسأل ChatGPT حول البحث

We examine the cosmic growth of the red sequence in a cosmological hydrodynamic simulation that includes a heuristic prescription for quenching star formation that yields a realistic passive galaxy population today. In this prescription, halos dominated by hot gas are continually heated to prevent their coronae from fueling new star formation. Hot coronae primarily form in halos above sim10^12 Modot, so that galaxies with stellar masses sim10^10.5 Modot are the first to be quenched and move onto the red sequence at z > 2. The red sequence is concurrently populated at low masses by satellite galaxies in large halos that are starved of new fuel, resulting in a dip in passive galaxy number densities around sim10^10 Modot. Stellar mass growth continues for galaxies even after joining the red sequence, primarily through minor mergers with a typical mass ratio sim1:5. For the most massive systems, the size growth implied by the distribution of merger mass ratios is typically sim2times the corresponding mass growth, consistent with observations. This model reproduces mass-density and colour-density trends in the local universe, with essentially no evolution to z = 1, with the hint that such relations may be washed out by z sim 2. Simulated galaxies are increasingly likely to be red at high masses or high local overdensities. In our model, the presence of surrounding hot gas drives the trends with both mass and environment.



قيم البحث

اقرأ أيضاً

258 - Mark Vogelsberger 2014
Previous simulations of the growth of cosmic structures have broadly reproduced the cosmic web of galaxies that we see in the Universe, but failed to create a mixed population of elliptical and spiral galaxies due to numerical inaccuracies and incomp lete physical models. Moreover, because of computational constraints, they were unable to track the small scale evolution of gas and stars to the present epoch within a representative portion of the Universe. Here we report a simulation that starts 12 million years after the Big Bang, and traces 13 billion years of cosmic evolution with 12 billion resolution elements in a volume of $(106.5,{rm Mpc})^3$. It yields a reasonable population of ellipticals and spirals, reproduces the distribution of galaxies in clusters and statistics of hydrogen on large scales, and at the same time the metal and hydrogen content of galaxies on small scales.
We study the nature of rapidly star-forming galaxies at z=2 in cosmological hydrodynamic simulations, and compare their properties to observations of sub-millimetre galaxies (SMGs). We identify simulated SMGs as the most rapidly star-forming systems that match the observed number density of SMGs. In our models, SMGs are massive galaxies sitting at the centres of large potential wells, being fed by smooth infall and gas-rich satellites at rates comparable to their star formation rates (SFR). They are not typically undergoing major mergers that significantly boost their quiescent SFR, but they still often show complex gas morphologies and kinematics. Our simulated SMGs have stellar masses of log M*/Mo~11-11.7, SFRs of ~180-500 Mo/yr, a clustering length of 10 Mpc/h, and solar metallicities. The SFRs are lower than those inferred from far-IR data by a factor of 3, which we suggest may owe to one or more systematic effects in the SFR calibrations. SMGs at z=2 live in ~10^13 Mo halos, and by z=0 they mostly end up as brightest group galaxies in ~10^14 Mo halos. We predict that higher-M* SMGs should have on average lower specific SFRs, less disturbed morphologies, and higher clustering. We also predict that deeper far-IR surveys will smoothly join SMGs onto the massive end of the SFR-M* relationship defined by lower-mass z=2 galaxies. Overall, our simulated rapid star-formers provide as good a match to available SMG data as merger-based scenarios, offering an alternative scenario that emerges naturally from cosmological simulations.
We examine the global HI properties of galaxies in quarter-billion particle cosmological simulations using Gadget-2, focusing on how galactic outflows impact HI content. We consider four outflow models, including a new one (ezw) motivated by recent i nterstellar medium simulations in which the wind speed and mass loading factor scale as expected for momentum-driven outflows for larger galaxies and energy-driven outflows for dwarfs (sigma<75 km/s). To obtain predicted HI masses, we employ a simple but effective local correction for particle self-shielding, and an observationally-constrained transition from neutral to molecular hydrogen. Our ezw simulation produces an HI mass function whose faint-end slope of -1.3 agrees well with observations from the ALFALFA survey; other models agree less well. Satellite galaxies have a bimodal distribution in HI fraction versus halo mass, with smaller satellites and/or those in larger halos more often being HI-deficient. At a given stellar mass, HI content correlates with star formation rate and inversely correlates with metallicity, as expected if driven by stochasticity in the accretion rate. To higher redshifts, massive HI galaxies disappear and the mass function steepens. The global cosmic HI density conspires to remain fairly constant from z~5-0, but the relative contribution from smaller galaxies increases with redshift.
217 - Kentaro Nagamine 2009
We examine the past and current work on the star formation (SF) histories of dwarf galaxies in cosmological hydrodynamic simulations. The results obtained from different numerical methods are still somewhat mixed, but the differences are understandab le if we consider the numerical and resolution effects. It remains a challenge to simulate the episodic nature of SF history in dwarf galaxies at late times within the cosmological context of a cold dark matter model. More work is needed to solve the mysteries of SF history of dwarf galaxies employing large-scale hydrodynamic simulations on the next generation of supercomputers.
Using data from the Sloan Digital Sky Survey (SDSS; data release 7), we have conducted a search for local analogs to the extremely compact, massive, quiescent galaxies that have been identified at z > 2. We show that incompleteness is a concern for s uch compact galaxies, particularly for low redshifts (z < ~0.05) as a result of the SDSS spectroscopic target selection algorithm. We have identified 63 massive red sequence galaxies at 0.066 < z < 0.12 that are smaller than the median size-mass relation by a factor of 2 or more. Consistent with expectations from the virial theorem, the median offset from the mass-velocity dispersion relation for these galaxies is 0.12 dex. We do not find any galaxies with sizes and masses comparable to those observed at z ~ 2, implying a decrease in the comoving number density (at fixed size and mass) by a factor of > 5000. This result cannot be explained by incompleteness: at 0.066 < z <0.12, the SDSS spectroscopic sample should typically be ~75% complete for galaxies with the sizes and masses seen at high redshift, although for the very smallest galaxies it may be as low as ~20%. To confirm that the absence of such compact massive galaxies in SDSS is not a spectroscopic selection effect, we have also looked for such galaxies in the SDSS photometric catalog, using photometric redshifts. While we do find signs of a bias against massive, compact galaxies, this analysis suggests that the SDSS spectroscopic sample is missing at most a few objects in the regime we consider. Accepting the high redshift results, it is clear that massive galaxies must undergo significant structural evolution over z<2 in order to match the population seen in the local universe. Our results suggest that a highly stochastic mechanism like major mergers cannot be the primary driver of this strong size evolution.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا