Damped Lyman α systems in galaxy formation simulations

By Andrew Pontzen, Fabio Governato, M. Pettini, C. Booth, G. Stinson, James Wadsley, A. Brooks, Thomas Quinn, M. Haehnelt. 2008

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We investigate the population of z = 3 damped Lyman alpha systems (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: the simulation parameters have been fixed by physical and z = 0 observational constraints, and thus our work 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 f ormation 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 ZDLA ≃ Z⊙/20) without invoking observationally unsupported mechanisms such as significant dust biasin g. 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 p ositive 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. DLAs in our simulations are predominantly associated with dark matter haloes with virial masses in the range 10 9 < Mvir/M⊙ < 10 11 . We are able to probe DLAs at high resolution, irrespective of their masses, by using a range of simulation s of differing volumes. The fully constrained feedback prescription in use causes the majority of DLA haloes to form stars at a very low rate, accounting for the low metallicities. It i s also responsible for the massmetallicity relation which appears essential for reproduc ing the velocity-metallicity correlation. 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.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

A new, precise measurement of the primordial abundance of deuterium (2012, background): “…for reliable measures of (D/H)p. DLAs are characterised by high column densities of neutral gas, with N(H i)> 2×1020 atoms cm−2 (Wolfe et al. 2005), and appear to be associated with galaxies at early stages of chemical evolution (Pontzen et al. 2008; Péroux et al. 2012; Krogager et al. 2012).”
The ESO UVES advanced data products quasar sample: II. Cosmological evolution of the neutral gas mass density (2013, background): “It is due to less self-shielding in the absorbers because at these column densities, part of the neutral gas of the absorber is ionized by incidentUV flux (e.g., Katz et al. 1996; Pontzen et al. 2008; McQuinn et al. 2011; Altay et al. 2011).”
ON THE (NON)EVOLUTION OF H i GAS IN GALAXIES OVER COSMIC TIME (2008, unknown): “We await explorations of this topic witin the context of cosmological simulations of galaxy formation (e.g. Nagamine et al. 2004; Razoumov et al. 2006; Pontzen et al. 2008).”
Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies (2012, methodology): “Each region was then resimulated at higher resolution and with baryons using the ‘zoomed-in’ volume renormalization technique (Katz & White 1993; Brooks et al. 2007; Pontzen et al. 2008), while fully preserving the surrounding large scale structure.”
The enrichment of the intergalactic medium with adiabatic feedback – I. Metal cooling and metal diffusion (2009, methodology): “Self-shielding was not modeled during the simulations, however we used a radiative transfer post-processor to recalculate the ionization states of hydrogen as described in Pontzen et al. (2008).”
A DEFINITIVE SURVEY FOR LYMAN LIMIT SYSTEMS AT z ∼ 3.5 WITH THE SLOAN DIGITAL SKY SURVEY (2009, methodology): “The Physical Nature of the LLSs As described in the introduction, observations and numerical simulations associate the DLAs with high z galaxies residing in virialized dark matter halos (e.g. Møller et al. 2002; Pontzen et al. 2008).”
The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime★ (2011, background): “Cosmological simulations of galaxy formation support the possibility that such DLAs still retain the chemical signature of early enrichment (Pontzen et al. 2008; Tescari et al. 2009); the most metal-poor DLAs arise in low mass halos that have undergone little to no in situ star formation.”
Galaxy formation theory (2010, background): “Numerous hydrodynamical simulation codes now contain implementations of chemical enrichment (Scannapiecoet al. 2005; Kobayashi et al. 2007; Pontzen et al. 2008; Gnedin et al. 2009).”
On the evolution of the H i column density distribution in cosmological simulations (2012, background): “…collisional ionization rates and the small-scale structure of the absorbers, has been found to have no significant impact on the simulated HI CDDF (Pontzen et al. 2008; McQuinn & Switzer 2010; Altay et al. 2011). c© 0000 RAS, MNRAS 000, 000–000 on Haardt & Madau (2001) together with Haardt &…”
THE DUAL ORIGIN OF STELLAR HALOS (2009, background): “This regulation of star formation also leads to realistic trends in gas fractions, with our lowest mass galaxies being the most gas-rich (Brooks et al. 2007), and reproducing the observed incidence rate and column densities of damped Lyα systems at z = 3 (Pontzen et al. 2008).”
Implementing molecular hydrogen in hydrodynamic simulations of galaxy formation (2012, background): “…2010), theint rnal structure of disk galaxies (Governato et al. 2007; Roškar et al. 2008; Stinson et al. 2009; Brooks et al. 2009), the column density distributions of damped Lyman-α systems (Pontzen et al. 2008, 2010), and the observed stellar mass-metallicity relationship (Brooks et al. 2007).”
Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs (2010, methodology): “Our fiducial simulation, used to describe most of the physical processes in Sections 3, 4 and 5 is the MW1 run discussed already in Brooks et al. (2007), Pontzen et al. (2008), Read et al. (2009), Brooks et al. (2009).”
Absorption-line systems in simulated galaxies fed by cold streams (2011, background): “Most of the DLAs are estimated by theory to originate in the mass interval 109–1011 M (e.g. Pontzen et al. 2008; Tescari et al. 2009), with a peak around ∼5 × 1010 M .”
THE ROLE OF COLD FLOWS IN THE ASSEMBLY OF GALAXY DISKS (2008, background): “At z = 3, these simulations reproduce the metallicities, incidence rate, and column density distributions of observed damped Lyman alpha absorbers (DLAs Pontzen et al. 2008).”
Deuterium abundance in the most metal-poor damped Lyman alpha system: converging on Ωb,0h2 (2008, background): “1 Damped Lyα systems are a class of QSO absorbers defined by their high column densities of neutral hydrogen, log[N (H I)/cm−2] ≥ 20.3 [see Wolfe, Gawiser & Prochaska (2005), and Pontzen et al. (2008) for recent reviews of DLAs].”
The EAGLE project: Simulating the evolution and assembly of galaxies and their environments (2014, methodology): “More recently, simulations that have been reprocessed using radiative transfer of ionizing radiation have succeeded in matching key properties of the high-column density H i absorbers (e.g. Pontzen et al. 2008; Altay et al. 2011; McQuinn et al. 2011; Rahmati et al. 2013a).”
De re metallica: the cosmic chemical evolution of galaxies (2018, background): “However, more generally, as a consequence of the issues discussed above, most studies investigate the mass-metallicity relation by using the velocity dispersion of the DLAs as a proxy for the mass (Haehnelt et al., 1998; Ledoux et al., 2006; Pontzen et al., 2008).”
Forming a large disc galaxy from a z < 1 major merger (2008, methodology): “The simulation applied a correction to the UV flux for self shielding of dense gas as introduced in Pontzen et al. (2008) and low-temperature metal cooling (Mashchenko, Wadsley & Couchman 2008).”
ON THE INTERPLAY BETWEEN STAR FORMATION AND FEEDBACK IN GALAXY FORMATION SIMULATIONS (2014, background): “Numerical models by Pontzen et al. (2008) have indicated that the metal rich DLAs are likely to be associated with halos of mass Mh & 1010 M .”