The nature of H I absorbers in gamma-ray burst afterglows: clues from hydrodynamic simulations

In recent work, we have shown that it is possible to link quantitatively many aspects of damped Lyman α (DLA) absorbers in the spectra of quasars to high-resolution simulations of galaxy formation. Using runs from the same series of hydrodynamic numerical studies, we consider the expected properties of intrinsic Lyman α absorbers seen in the spectra of high-redshift (z > 2) gamma-ray burst afterglows (GRB–DLAs). If GRBs are associated with the death of massive stars, their afterglows provide insights into otherwise unprobed regions of protogalactic objects, but detailed physical interpretations are currently embryonic. We find that median impact parameters (measured from the potential minimum) are approximately 1 kpc for GRBs compared with 4 kpc for quasi-stellar object–DLA (QSO–DLA). However, an equally important difference is that GRB–DLAs are predominantly associated with haloes of mass 10^(10) < M_(vir)/M_⊙ < 10^(12) , an order of magnitude larger than the hosts of QSO–DLAs. Accordingly, there are differences in the stellar properties of hosts. For instance, mean star formation rates are higher: <M(overdot)_★ ≃ 10 M_⊙ yr^(-1) for GRB–DLAs compared with <M(overdot)_★ ≃ 1 M_⊙ yr^(-1) for QSO–DLAs. Our simulations accurately predict the form of the GRB–DLA H I column density distribution, producing quantitative agreement for N_(H I) > 10^(19) cm^(−2) , but they somewhat underpredict the incidence of low column densities N_(H I_ < 10^(19) cm^(−2) . This is reflected in our estimate of the ionizing photon escape fraction, f_(esc) ≃ 1 per cent, which is lower than the observational GRB-derived escape fraction (2 per cent). Line-of-sight neutral gas metallicities predicted by our simulations (10^(−2) < Z/Z_⊙ < 1) are consistent with the modest observational constraints. Because of large internal dispersions in gas metallicities, this agreement is not significantly compromised by imposing a cut-off on the metallicity of stars able to launch GRBs (Z_★ < Z_⊙/3) , confounding claims that the observed metallicity of GRB–DLAs poses a severe challenge to current GRB models.

[1]  P. Moller,et al.  Ly+ and ultraviolet emission from high-redshift gamma-ray burst hosts: to what extent do gamma-ray bursts trace star formation? , 2005 .

[2]  S. White,et al.  Galaxies–intergalactic medium interaction calculation – I. Galaxy formation as a function of large-scale environment , 2009, 0906.4350.

[3]  J. Xavier Prochaska,et al.  Reconciling the Metallicity Distributions of Gamma-Ray Burst, Damped Lyα, and Lyman Break Galaxies at z ≈ 3 , 2008, Proceedings of the International Astronomical Union.

[4]  Jr.,et al.  The Global Schmidt law in star forming galaxies , 1997, astro-ph/9712213.

[5]  S. E. Nuza,et al.  The host galaxies of long-duration gamma-ray bursts in a cosmological hierarchical scenario , 2006, astro-ph/0611122.

[6]  J. P. U. Fynbo,et al.  Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches , 2009, 0907.1057.

[7]  Patrick Petitjean,et al.  Molecular Hydrogen in high redshift Damped Lyman-α systems , 2002 .

[8]  G. Stinson,et al.  Damped Lyman α systems in galaxy formation simulations , 2008, 0804.4474.

[9]  T. Quinn,et al.  Gasoline: a flexible, parallel implementation of TreeSPH , 2003, astro-ph/0303521.

[10]  S. Woosley,et al.  Nucleosynthesis in massive stars and the 12C(α, γ)16O reaction rate , 1993 .

[11]  D. Osterbrock,et al.  Astrophysics of Gaseous Nebulae , 1976 .

[12]  E. Rol,et al.  The host of GRB 030323 at z=3.372: A very high column density DLA system with a low metallicity , 2004, astro-ph/0403080.

[13]  A Physical Upper Limit on the H I Column Density of Gas Clouds , 2001, astro-ph/0109280.

[14]  Simon D. M. White,et al.  Hierarchical galaxy formation : overmerging and the formation of an X-ray cluster , 1993 .

[15]  R. S. Priddey,et al.  Probing cosmic chemical evolution with gamma-ray bursts: GRB 060206 at z = 4.048 , 2006, astro-ph/0602444.

[16]  M. Halpern,et al.  FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: LIKELIHOODS AND PARAMETERS FROM THE WMAP DATA , 2008, 0803.0586.

[17]  J. Prochaska,et al.  A New Constraint on the Escape Fraction in Distant Galaxies Using γ-Ray Burst Afterglow Spectroscopy , 2007, 0707.2594.

[18]  Hsiao-Wen Chen,et al.  Escape of Ionizing Radiation from High-Redshift Galaxies , 2007, 0707.0879.

[19]  K. Lodders Solar System Abundances and Condensation Temperatures of the Elements , 2003 .

[20]  Claus Leitherer,et al.  Optimization of Starburst99 for Intermediate-Age and Old Stellar Populations , 2004, astro-ph/0412491.

[21]  Princeton,et al.  MEASURED METALLICITIES AT THE SITES OF NEARBY BROAD-LINED TYPE IC SUPERNOVAE AND IMPLICATIONS FOR THE SN-GRB CONNECTION , 2007 .

[22]  M. Modjaz,et al.  MODELING THE GRB HOST GALAXY MASS DISTRIBUTION: ARE GRBs UNBIASED TRACERS OF STAR FORMATION? , 2009, 0905.1953.

[23]  India,et al.  The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman-alpha systems , 2003 .

[24]  G. Stinson,et al.  The Origin and Evolution of the Mass-Metallicity Relationship for Galaxies: Results from Cosmological N-Body Simulations , 2006, astro-ph/0609620.

[25]  P. Noterdaeme,et al.  Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7 , 2009, 0908.1574.

[26]  E. O. Ofek,et al.  THE HOST GALAXIES OF SWIFT DARK GAMMA-RAY BURSTS: OBSERVATIONAL CONSTRAINTS ON HIGHLY OBSCURED AND VERY HIGH REDSHIFT GRBs , 2009, 0905.0001.

[27]  Jason X. Prochaska,et al.  Dissecting the Circumstellar Environment of γ-Ray Burst Progenitors , 2006, astro-ph/0601057.

[28]  C. Guidorzi,et al.  THE PROMPT, HIGH-RESOLUTION SPECTROSCOPIC VIEW OF THE “NAKED-EYE” GRB080319B , 2008, 0804.2141.

[29]  C. Brook,et al.  Forming a large disc galaxy from a z < 1 major merger , 2008, 0812.0379.

[30]  Andre Maeder,et al.  Stellar Evolution with Rotation , 2000 .

[31]  Jason X. Prochaska,et al.  A Survey for N V Absorption at z ≈ zGRB in GRB Afterglow Spectra: Clues to Gas Near the Progenitor Star , 2008, 0806.0399.

[32]  IAA-CSIC,et al.  UV star-formation rates of GRB host galaxies , 2004, astro-ph/0407066.

[33]  J. Prochaska,et al.  The SDSS Damped Lyα Survey: Data Release 3 , 2005, astro-ph/0508361.

[34]  D. Osterbrock,et al.  Book-Review - Astrophysics of Gaseous Nebulae and Active Galactic Nuclei , 1989 .

[35]  Fabio Governato,et al.  Forming disc galaxies in ΛCDM simulations , 2006 .

[36]  A. MacFadyen,et al.  Collapsars: Gamma-Ray Bursts and Explosions in “Failed Supernovae” , 1998, astro-ph/9810274.

[37]  Usa,et al.  CONSTRAINING THE STAR FORMATION HISTORIES OF GAMMA-RAY BURST HOST GALAXIES FROM THEIR OBSERVED ABUNDANCE PATTERNS , 2008, 0811.1591.

[38]  Christian Wolf,et al.  The metallicity dependence of the long-duration gamma-ray burst rate from host galaxy luminosities , 2007 .

[39]  S. R. Kulkarni,et al.  Time-dependent Optical Spectroscopy of GRB 010222: Clues to the Gamma-Ray Burst Environment , 2002, astro-ph/0207009.

[40]  S. Borgani,et al.  Damped Lyman α systems in high‐resolution hydrodynamical simulations , 2009, 0904.3545.

[41]  D. Osterbrock,et al.  Astrophysics of Gaseous Nebulae and Active Galactic Nuclei , 1989 .

[42]  S. Arnouts,et al.  The fabulous destiny of galaxies : bridging past and present , 2006 .

[43]  G. Stinson,et al.  Star formation and feedback in smoothed particle hydrodynamic simulations – I. Isolated galaxies , 2006, astro-ph/0602350.

[44]  STAR FORMATION IN GALAXIES ALONG THE HUBBLE SEQUENCE , 1998, astro-ph/9807187.

[45]  Max Pettini,et al.  The Direct Detection of Lyman Continuum Emission from Star-forming Galaxies at z~3 , 2006, astro-ph/0606635.

[46]  S. M. Fall,et al.  Heavy-Element Abundances and Dust Depletions in the Host Galaxies of Three Gamma-Ray Bursts , 2002, astro-ph/0203154.

[47]  A. J. Levan,et al.  Long γ-ray bursts and core-collapse supernovae have different environments , 2006, Nature.

[48]  Alan A. Wells,et al.  The Swift Gamma-Ray Burst Mission , 2004, astro-ph/0405233.

[49]  Jason X. Prochaska,et al.  Probing the Interstellar Medium near Star-forming Regions with Gamma-Ray Burst Afterglow Spectroscopy: Gas, Metals, and Dust , 2007 .

[50]  U. Copenhagen,et al.  Escape of Ionizing Radiation from Star-forming Regions in Young Galaxies , 2006, astro-ph/0609545.

[51]  R. S. Priddey,et al.  HI column densities of z > 2 Swift gamma-ray bursts , 2006 .

[52]  Abraham Loeb,et al.  Identifying the Environment and Redshift of Gamma-Ray Burst Afterglows from the Time Dependence of Their Absorption Spectra , 1998 .

[53]  G. Gilmore,et al.  The distribution of low-mass stars in the Galactic disc , 1993 .

[54]  Alexander Heger,et al.  The Progenitor Stars of Gamma-Ray Bursts , 2005, astro-ph/0508175.

[55]  Switzerland,et al.  Stellar evolution with rotation - XIII. Predicted GRB rates at various Z , 2005, astro-ph/0507343.

[56]  P. Madau,et al.  Radiative Transfer in a Clumpy Universe. II. The Ultraviolet Extragalactic Background , 1995, astro-ph/9509093.

[57]  Observatoire de Geneve,et al.  THE FIRST POSITIVE DETECTION OF MOLECULAR GAS IN A GRB HOST GALAXY , 2009, 0901.0556.

[58]  S. Savaglio,et al.  GRBs as cosmological probes—cosmic chemical evolution , 2006, astro-ph/0609489.

[59]  D. A. Kann,et al.  LOW-RESOLUTION SPECTROSCOPY OF GAMMA-RAY BURST OPTICAL AFTERGLOWS: BIASES IN THE SWIFT SAMPLE AND CHARACTERIZATION OF THE ABSORBERS , 2009, 0907.3449.

[60]  S. Savaglio,et al.  THE GALAXY POPULATION HOSTING GAMMA-RAY BURSTS , 2008, 0803.2718.

[61]  S. M. Fall,et al.  Cosmic chemical evolution , 1995 .

[62]  M. Viel,et al.  On the formation of dwarf galaxies and stellar haloes , 2006, astro-ph/0606391.

[63]  Sandra Savaglio,et al.  Rapid-response mode VLT/UVES spectroscopy of GRB 060418. Conclusive evidence for UV pumping from the time evolution of Fe II and Ni II excited- and metastable-level populations , 2006 .

[64]  L. Hernquist,et al.  Incidence Rate of GRB-Host DLAs at High Redshift , 2008, 0806.2899.

[65]  A. Pontzen,et al.  Dust biasing of damped Lyman alpha systems: a Bayesian analysis , 2008, 0810.3236.

[66]  Stephanie Courty,et al.  Host galaxies of gamma-ray bursts and their cosmological evolution , 2004 .

[67]  E. Le Floc'h,et al.  Detection of Wolf-Rayet stars in host galaxies of gamma-ray bursts (GRBs) : are GRBs produced by runaway massive stars ejected from high stellar density regions? , 2006 .

[68]  Hsiao-Wen Chen,et al.  Searching for Low Surface Brightness Galaxies in the Hubble Ultra Deep Field: Implications for the Star Formation Efficiency in Neutral Gas at z ∼ 3 , 2006, astro-ph/0608040.