scholarly journals Damped Lyman-α Absorbers in Cosmological SPH Simulations: the “Metallicity Problem”

2005 ◽  
Vol 216 ◽  
pp. 266-273
Author(s):  
Kentaro Nagamine ◽  
Volker Springel ◽  
Lars Hernquist
Keyword(s):  
Star Formation ◽  
Cold Dark Matter ◽  
Mass Density ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Galactic Winds ◽  
Particle Hydrodynamics ◽  
Order Of Magnitude ◽  
Smoothed Particle ◽  
Hydrogen Mass

We study the distribution of star formation rate (SFR) and metallicity of damped Lyman-α absorbers (DLAs) using cosmological smoothed particle hydrodynamics (SPH) simulations of the Λ cold dark matter (CDM) model. Our simulations include a phenomenological model for feedback by galactic winds which allows us to examine the effect of galactic outflows on the distribution of SFR and metallicity of DLAs. For models with strong galactic winds, we obtain good agreement with recent observations with respect to total neutral hydrogen mass density, NHI column-density distribution, abundance of DLAs, and for the distribution of SFR in DLAs. However, we also find that the median metallicity of simulated DLAs is higher than the values typically observed by nearly an order of magnitude. This discrepancy with observations could be due to shortcomings in the treatment of the supernova feedback or the multiphase structure of the gas in our current simulations. Recent observations by Wolfe et al. (2003a,b) seem to point to the same problem; i.e. the observed DLA metallicities are much lower than those expected from the (either observed or simulated) DLA star formation rates, a puzzle that has been known as the “missing metals”-problem for the globally averaged quantities.

scholarly journals The Neutral Hydrogen Cosmological Mass Density at z = 5

2016 ◽  
Vol 11 (S321) ◽  
pp. 309-314
Author(s):  
Neil H. M. Crighton ◽  
Michael T. Murphy ◽  
J. Xavier Prochaska ◽  
Gábor Worseck ◽  
Marc Rafelski ◽  
...  
Keyword(s):  
Star Formation ◽  
Functional Form ◽  
Mass Density ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Ionized Gas ◽  
Galactic Winds ◽  
Lower Column ◽  
Systematic Effects

AbstractWe present the largest homogeneous survey of redshift > 4.4 damped Lyα systems (DLAs) using the spectra of 163 quasars that comprise the Giant Gemini GMOS (GGG) survey. With this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, ΩHI. After correcting for systematic effects using a combination of mock and higher-resolution spectra, we find ΩHI= 0.98+0.20-0.18 × 10−3 at 〈z〉 = 4.9, assuming a 20% contribution from lower column density systems below the DLA threshold. By comparing to literature measurements at lower redshifts, we show that ΩHI can be described by the functional form ΩHI(z) ∝ (1 + z)0.4. This gradual decrease from z = 5 to 0 suggests that in the galaxies which dominate the cosmic star formation rate, Hi is a transitory gas phase fuelling star formation which must be continually replenished by more highly-ionized gas from the intergalactic medium, and from recycled galactic winds.

scholarly journals Testing star formation rate indicators using galaxy merger simulations and radiative transfer

2009 ◽  
Vol 5 (S262) ◽  
pp. 257-260
Author(s):  
Christopher C. Hayward ◽  
Patrik Jonsson ◽  
Kai Noeske ◽  
Stijn Wuyts ◽  
T. J. Cox ◽  
...  
Keyword(s):  
Star Formation ◽  
Radiative Transfer ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Spectral Energy ◽  
Merging Galaxies ◽  
Formation History ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

AbstractWe discuss our ongoing project analyzing N-body/smoothed-particle hydrodynamics simulations of isolated and merging galaxies, performed using GADGET-2 (Springel 2005), with the 3-D adaptive grid, polychromatic Monte Carlo radiative transfer code SUNRISE (Jonsson 2006). We apply commonly used UV, optical, and IR star formation rate (SFR) indicators to the integrated spectral energy distributions (SEDs) of the simulated galaxies in order to determine how well the SFR indicators recover the instantaneous SFR in the simulations. The models underlying each SFR indicator must necessarily make assumptions about physical properties of the galaxies, e.g., the star formation history (SFH), whereas all such properties are known in the simulations. This enables us to test and compare SFR indicators in a way that is complementary to observational studies. We present one preliminary result of interest: even after correcting the Hα luminosity for dust using the Calzetti et al. (2000) attenuation law the SFR is significantly underestimated for simulated galaxies with SFR ≳ 10 M⊙ yr−1.

scholarly journals Implementing and comparing sink particles in AMR and SPH

2010 ◽  
Vol 6 (S270) ◽  
pp. 425-428 ◽  
Author(s):  
Christoph Federrath ◽  
Robi Banerjee ◽  
Daniel Seifried ◽  
Paul C. Clark ◽  
Ralf S. Klessen
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Particle Creation ◽  
Adaptive Mesh ◽  
Particle Properties ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Density Threshold

AbstractWe implemented sink particles in the Adaptive Mesh Refinement (AMR) code FLASH to model the gravitational collapse and accretion in turbulent molecular clouds and cores. Sink particles are frequently used to measure properties of star formation in numerical simulations, such as the star formation rate and efficiency, and the mass distribution of stars. We show that only using a density threshold for sink particle creation is insufficient in case of supersonic flows, because the density can exceed the threshold in strong shocks that do not necessarily lead to local collapse. Additional physical collapse indicators have to be considered. We apply our AMR sink particle module to the formation of a star cluster, and compare it to a Smoothed Particle Hydrodynamics (SPH) code with sink particles. Our comparison shows encouraging agreement of gas and sink particle properties between the AMR and SPH code.

scholarly journals Clues to the nature of dark matter from first galaxies

2019 ◽  
Vol 489 (1) ◽  
pp. 487-496 ◽  
Author(s):  
Boyan K Stoychev ◽  
Keri L Dixon ◽  
Andrea V Macciò ◽  
Marvin Blank ◽  
Aaron A Dutton
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Mass Function ◽  
Stellar Mass ◽  
The Impact

ABSTRACT We use 38 high-resolution simulations of galaxy formation between redshift 10 and 5 to study the impact of a 3 keV warm dark matter (WDM) candidate on the high-redshift Universe. We focus our attention on the stellar mass function and the global star formation rate and consider the consequences for reionization, namely the neutral hydrogen fraction evolution and the electron scattering optical depth. We find that three different effects contribute to differentiate warm and cold dark matter (CDM) predictions: WDM suppresses the number of haloes with mass less than few 109 M⊙; at a fixed halo mass, WDM produces fewer stars than CDM, and finally at halo masses below 109 M⊙, WDM has a larger fraction of dark haloes than CDM post-reionization. These three effects combine to produce a lower stellar mass function in WDM for galaxies with stellar masses at and below 107 M⊙. For z > 7, the global star formation density is lower by a factor of two in the WDM scenario, and for a fixed escape fraction, the fraction of neutral hydrogen is higher by 0.3 at z ∼ 6. This latter quantity can be partially reconciled with CDM and observations only by increasing the escape fraction from 23 per cent to 34 per cent. Overall, our study shows that galaxy formation simulations at high redshift are a key tool to differentiate between dark matter candidates given a model for baryonic physics.

scholarly journals UGC 7639: A Dwarf Galaxy in the Canes Venatici I Cloud

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
L. M. Buson ◽  
D. Bettoni ◽  
P. Mazzei ◽  
G. Galletta
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Global Properties ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Formation And Evolution ◽  
Good Agreement

We want to get insight into the formation mechanism and the evolution of UGC 7639, a dwarf galaxy in the Canes Venatici I Cloud (CVnIC). We used archival multiwavelength data to constrain its global properties. Ultraviolet images show that UGC 7639 inner regions are composed mostly by young stellar populations. In addition, we used smoothed particle hydrodynamics simulations with chemophotometric implementation to account for its formation and evolution. UGC 7639 is an example of blue dwarf galaxy whose global properties are well matched by our multiwavelength approach, that is, a suitable approach to highlight the evolution also of these galaxies as a class. We found that the global properties of UGC 7639, namely, its total absolute B-band magnitude, its whole spectral energy distribution, and morphology, are well matched by an encounter with a system four times more massive than our target. Moreover, the current star formation rate of the simulated dwarf, ≈0.03 M⊙ yr−1, is in good agreement with our UV-based estimate. We derived a galaxy age of 8.6 Gyr. Following our simulation, the ongoing star formation will extinguish within 1.6 Gyr, thus leaving a red dwarf galaxy.

scholarly journals Starbursts and Extra-planar Hα from SINGG

2004 ◽  
Vol 217 ◽  
pp. 287-293 ◽  
Author(s):  
Gerhardt R. Meurer
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Neutral Hydrogen ◽  
Neutral Gas ◽  
Galactic Winds ◽  
First Pass ◽  
Show Evidence ◽  
Galactic Sources ◽  
Hydrogen Mass ◽  
Larger Sample

The NOAO Survey for Ionization in Neutral Gas Galaxies (SINGG) is the largest star formation survey of an H I selected sample. Since the selection is made without regard to optical morphology, it is not biased toward or against “interesting” types of galaxies; thus SINGG is an ideal sample for studying galaxy demographics. Of a sample of 90 extra-galactic sources observed in photometric conditions, all are detected in Hα. This indicates that dormant galaxies, those containing an appreciable ISM but no star formation, are at best rare. We have made first pass morphological surveys for starbursts, as judged by Hα surface brightness, and outflows as judged by extra-planar Hα. We find that about 15% of the sources contain starbursts, with little dependence on the neutral hydrogen mass MHI. Nearly one half of a sample ~ 35 edge-on galaxies show evidence for extra-planar Hα having a scale size of 0.5 Kpc or larger, while nearly one quarter have extra-planar Hα features 1.0 Kpc in size or larger. There is a hint that high MHI systems preferentially have displaced outflows (chimneys, or fountains) while central outflows (galactic winds) preferentially occur in low MHI systems. However, a larger sample (e.g. the full SINGG survey) is needed to confirm this trend.

scholarly journals A statistical measurement of the H i spin temperature in DLAs at cosmological distances

2021 ◽  
Author(s):  
James R Allison
Keyword(s):  
Star Formation ◽  
Atomic Hydrogen ◽  
Milky Way ◽  
Star Formation Rate ◽  
Mass Density ◽  
Formation Rate ◽  
Neutral Medium ◽  
Molecular Gas ◽  
Spin Temperature ◽  
Order Of Magnitude

Abstract Evolution of the cosmic star formation rate (SFR) and molecular mass density is expected to be matched by a similarly strong evolution of the fraction of atomic hydrogen (H i) in the cold neutral medium (CNM). We use results from a recent commissioning survey for intervening 21-cm absorbers with the Australian Square Kilometre Array Pathfinder (ASKAP) to construct a Bayesian statistical model of the NHI-weighted harmonic mean spin temperature (Ts) at redshifts between z = 0.37 and 1.0. We find that Ts ≤ 274 K with 95 per cent probability, suggesting that at these redshifts the typical H i gas in galaxies at equivalent DLA column densities may be colder than the Milky Way interstellar medium (Ts, MW ∼ 300 K). This result is consistent with an evolving CNM fraction that mirrors the molecular gas towards the peak in SFR at z ∼ 2. We expect that future surveys for H i 21-cm absorption with the current SKA pathfinder telescopes will be able to provide constraints on the CNM fraction that are an order of magnitude greater than presented here.

scholarly journals DLAs AND GALAXY FORMATION

2007 ◽  
Vol 22 (32) ◽  
pp. 2413-2427
Author(s):  
KENTARO NAGAMINE
Keyword(s):  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Mass Density ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Infrared Telescope ◽  
Neutral Gas ◽  
Galactic Winds ◽  
Cold Dark Matter Model ◽  
The Future

Damped Lyman-α systems (DLAs) are useful probes of star formation and galaxy formation at high-redshift (hereafter high-z). We study the physical properties of DLAs and their relationship to Lyman break galaxies (LBGs) using cosmological hydrodynamic simulations based on the concordance Λ cold dark matter model. Fundamental statistics such as global neutral hydrogen (H I) mass density, H I column density distribution function, DLA rate-of-incidence and mean halo mass of DLAs are reproduced reasonably well by the simulations, but with some deviations that need to be understood better in the future. We discuss the feedback effects by supernovae and galactic winds on the DLA distribution. We also compute the [C II] emission from neutral gas in high-z galaxies, and make predictions for the future observations by the Atacama Large Millimeter Array (ALMA) and Space Infrared Telescope for Cosmology and Astrophysics (SPICA). Agreement and disagreement between simulations and observations are discussed, as well as the future directions of our DLA research.

scholarly journals New constraints on the co-moving star formation rate in the redshift interval 6

2006 ◽  
Vol 2 (14) ◽  
pp. 251-251
Author(s):  
Richard S. Ellis ◽  
Daniel P. Stark ◽  
Johan Richard ◽  
Andrew J. Bunker ◽  
Eiichi E. Egami ◽  
...  
Keyword(s):  
Star Formation ◽  
Electron Scattering ◽  
Star Formation Rate ◽  
Hubble Space Telescope ◽  
Mass Density ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Stellar Mass ◽  
Microwave Background ◽  
Star Forming

AbstractRecent progress in measuring the optical depth of neutral hydrogen in distant quasars and that of electron scattering of microwave background photons suggests that most of the sources responsible for cosmic re-ionisation probably lie in the redshift interval 6 to 10. We present two new observational results which, together, provide valuable constraints on the contribution from star-forming sources in this redshift interval. First, using a large sample of v-band dropouts with unconfused Spitzer-IRAC detections, we determine the integrated stellar mass density at z = 5. This provides a valuable ‘integral constraint’ on past star formation. It seems difficult to reconcile the observed stellar mass at z = 5 with the low abundance of luminous i-z- and J-band dropouts in deep Hubble Space Telescope data. Accordingly, we explore whether less luminous star-forming sources in the redshift interval 6 to 10 might be the dominant cause of cosmic re-ionization. In the second component of our research, we report on the results of two surveys for weak Lymanα emitters and z- and J-band dropouts highly-magnified by foreground lensing clusters. Although some promising z = 8–9 candidates are found, it seems unlikely that low luminosity sources in this redshift interval can dominate cosmic reionization. If our work is substantiated by more extensive and precise surveys, the bulk of the re-ionizing photons may come from yet earlier sources lying at redshifts z>10.

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