Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0804.4474

Damped Lyman Alpha Systems in Galaxy Formation Simulations

Andrew Pontzen·Fabio Governato·Max Pettini·C. M. Booth·Greg Stinson·James Wadsley·Alyson Brooks·Thomas Quinn·Martin Haehnelt
View original source ↗Read source document ↗Export metadata ↓

Abstract

We investigate the population of z=3 damped Lyman alpha absorbers (DLAs) in a recent series of high resolution galaxy formation simulations. The simulations are of interest because they form at z=0 some of the most realistic disk galaxies to date. No free parameters are available in our study: these have been fixed by physical and z=0 observational constraints, and thus our study provides a genuine consistency test. The precise role of DLAs in galaxy formation remains in debate, but they provide a number of strong constraints on the nature of our simulated bound systems at z=3 because of their coupled information on neutral H I densities, kinematics, metallicity and estimates of star formation activity. Our results, without any parameter-tuning, closely match the observed incidence rate and column density distributions of DLAs. Our simulations are the first to reproduce the distribution of metallicities (with a median of Z_{DLA} = Z_{solar}/20) without invoking observationally unsupported mechanisms such as dust biasing. This is especially encouraging given that these simulations have previously been shown to have a realistic 0<z<2 stellar mass-metallicity relation. Additionally, we see a strong positive correlation between sightline metallicity and low-ion velocity width, the normalization and slope of which comes close to matching recent observational results. However, we somewhat underestimate the number of observed high velocity width systems; the severity of this disagreement is comparable to other recent DLA focused studies. By z=0 the majority of the z=3 neutral gas forming the DLAs has been converted into stars, in agreement with rough physical expectations. [Abridged]

Explore related subjects

astro-ph

Keep this discovery

BibTeXRIS

Andrew Pontzen, Fabio Governato, Max Pettini, C. M. Booth, Greg Stinson, James Wadsley, Alyson Brooks, Thomas Quinn, Martin Haehnelt. 2008-10-17. Damped Lyman Alpha Systems in Galaxy Formation Simulations. https://doi.org/10.1111/j.1365-2966.2008.13782.x

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2015

Subarcsecond Submillimeter Imaging of the Ultracompact HII Region G5.89-0.39

We present the first subarcsecond submillimeter images of the enigmatic ultracompact HII region (UCHII) G5.89-0.39. Observed with the SMA, the 875 micron continuum emission exhibits a shell-like morphology similar to longer wavelengths. By using images with comparable angular resolution at five frequencies obtained from the VLA archive and CARMA, we have removed the free-free component from the 875 micron image. We find five sources of dust emission: two compact warm objects (SMA1 and SMA2) along the periphery of the shell, and three additional regions further out. There is no dust emission inside the shell, supporting the picture of a dust-free cavity surrounded by high density gas. At subarcsecond resolution, most of the molecular gas tracers encircle the UCHII region and appear to constrain its expansion. We also find G5.89-0.39 to be almost completely lacking in organic molecular line emission. The dust cores SMA1 and SMA2 exhibit compact spatial peaks in optically-thin gas tracers (e.g. 34SO2), while SMA1 also coincides with 11.9 micron emission. In CO(3-2), we find a high-velocity north/south bipolar outflow centered on SMA1, aligned with infrared H2 knots, and responsible for much of the maser activity. We conclude that SMA1 is an embedded intermediate mass protostar with an estimated luminosity of 3000 Lsun and a circumstellar mass of ~1 Msun. Finally, we have discovered an NH3 (3,3) maser 12 arcsec northwest of the UCHII region, coincident with a 44 GHz CH3OH maser, and possibly associated with the Br gamma outflow source identified by Puga et al. (2006).

astro-ph↗
arXiv2015

Solutions to the "General Grand Unification Problem," and the Questions "How Did Our Universe Come Into Being?" and "Of What is Empty Space Composed?"

Using mathematical techniques to model one of the most simplistic of human linguistic processes, it is rationally predicted that within the nonstandard physical world (NSP-world) there exists a force-like (logical) operator *S and an entity w' such that *S{w'} sequentially generates each of the Natural systems that comprise a Universe. This model shows specifically that within the NSP-world the behavior of each Natural world Natural system is related logically. Further, the model predicts the rational existence of a single type of entity within the NSP-world's substratum that can be used to construct, by means of an exceptionally simple process, all of the fundamental Natural world particles used within particle physics. In section 11.2, it is shown how (Natural law) allowable perturbations in Natural system behavior are also included within this mathematical model. These results solve the pre-geometry problem of Wheeler. In general, the model predicts that when the behavior of these Universe creating processes is viewed globally, it can be described as apparently mirroring the behavior of an infinitely powerful computer or mind.

astro-ph↗
arXiv2014

Dark matter in elliptical galaxies: I. Is the total mass density profile of the NFW form or even steeper?

Elliptical galaxies are modelled as Sersic luminosity distributions with density profiles (DPs) for the total mass adopted from the DPs of haloes within dissipationless LambdaCDM N-body simulations. Ellipticals turn out to be inconsistent with cuspy low-concentration NFW models representing the total mass, nor are they consistent with a steeper -1.5 inner slope, nor with the shallower models proposed by Navarro et al. 04, nor with NFW models 10 times more concentrated than predicted, as deduced from several X-ray observations: the mass models, extrapolated inwards, lead to local mass-to-light ratios that are smaller than the stellar value inside an effective radius (R_e), and to central aperture velocity dispersions that are much smaller than observed. This conclusion remains true as long as there is no sharp steepening (slope < -2) of the dark matter (DM) DPs just inside 0.01 virial radii. The too low total mass and velocity dispersion produced within R_e by an NFW-like total mass profile suggests that the stellar component should dominate the DM one out to at least R_e. It should then be difficult to kinematically constrain the inner slope of the dark matter DP of ellipticals. The high concentration parameters deduced from X-ray observations appear to be a consequence of fitting an NFW model to the total mass DP made up of a stellar component that dominates inside and a DM component that dominates outwards. An appendix gives the virial mass dependence of the concentration parameter, central density, and total mass of the Navarro et al. model. In a 2nd appendix are given single integral expressions for the velocity dispersions averaged along the line-of-sight, in circular apertures and in thin slits, for general luminosity density and mass distributions, with isotropic orbits.

astro-ph↗