Gas and dust properties in the afterglow spectra of GRB 050730

Starling, R. L. C.; Vreeswijk, P. M.; Ellison, Sara L.; Rol, E.; Wiersema, K.; Levan, A. J.; Tanvir, N. R.; Wijers, R. A. M. J.; Tadhunter, C. N.; Zaurín, J. Rodríguez; Delgado, R. M. González; Kouveliotou, C.

doi:10.1051/0004-6361:200500181

Cited by 70 publications

(78 citation statements)

References 25 publications

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“…The total neutral hydrogen column density of the GRB 050730-DLA has been measured in previous analyses (Starling et al 2005;Chen et al 2005;D'Elia et al 2007) and the standard deviation of the three available measurements, based on different datasets, is very small (0.04 dex). We thus adopt their average value and combined uncertainty, i.e., log N(H 0 ) = 22.10 ± 0.10.…”

Section: Discussionmentioning

confidence: 95%

“…This line of sight exhibits one of the highest H 0 column density DLAs ever observed in GRB afterglow spectra (Starling et al 2005;Chen et al 2005;D'Elia et al 2007) with a metallicity at the low end of the distribution for GRB hosts (see Chen et al 2005;Prochaska et al 2007a;D'Elia et al 2007; see also this paper, Sect. 2.2.1).…”

Section: Introductionmentioning

confidence: 84%

“…Including the process of destruction of UV photons by dust grains would decrease the influence of the GRB even more. However, this will be important only for high N(H 0 ) values coupled to high metallicities and large dust contents, while for GRB 050730 a low dust content was inferred (see Starling et al 2005). Therefore, the current lack of H 2 detections in GRB-DLAs located at least 0.5 kpc away Fig.…”

Section: Grb-dla Gas Distance and H 2 Photo-dissociationmentioning

confidence: 92%

“…In the conversion to the rest frame, we adopted the Galactic extinction of E(B − V) = 0.046 from Schlegel et al (1998) and assumed that any other extinction along the line of sight is negligible (see also Starling et al 2005). The latter assumption is consistent with the low metallicity and low depletion factor of [S/Fe] measured at the hostgalaxy absorber redshift, which indicates a low dust content if any (see Sect.…”

Section: Modelmentioning

confidence: 94%

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Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

Ledoux¹,

Vreeswijk

Smette³

et al. 2009

A&A

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160

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Aims. We aim to understand the nature of the absorbing neutral gas in the galaxies hosting high-redshift long-duration gamma-ray bursts (GRBs) and to determine their physical conditions. Methods. A detailed analysis of high-quality VLT/UVES spectra of the optical afterglow of GRB 050730 and other Swift-era bursts is presented. Results. We report the detection of a significant number of previously unidentified allowed transition lines of Fe + , involving the fine structure of the ground term ( 6 D 7/2 , 6 D 5/2 , 6 D 3/2 , 6 D 1/2 ) and that of other excited levels ( 4 F 9/2 , 4 F 7/2 , 4 F 5/2 , 4 F 3/2 , 4 D 7/2 , 4 D 5/2 ), from the z abs = 3.969, log N(H 0 ) = 22.10, damped Lyman-α (DLA) system located in the host galaxy of GRB 050730. No molecular hydrogen (H 2 ) is detected down to a molecular fraction of log f < −8.0. We derive accurate metal abundances for Fe + , S + , N 0 , Ni + , and, for the first time in this system, Si + and Ar 0 . The absorption lines are best-fit as a single narrow velocity component at z abs = 3.96857. The time-dependent evolution of the observed Fe + energy-level populations is modelled by assuming the excitation mechanism is fluorescence following excitation by ultraviolet photons emitted by the afterglow of GRB 050730. This UV pumping model successfully reproduces the observations, yielding a total Fe + column density of log N = 15.49 ± 0.03, a burst/cloud distance (defined to the near-side of the cloud) of d = 440 ± 30 pc, and a linear cloud size of l = 520 +240 −190 pc. This application of our photoexcitation code demonstrates that burst/DLA distances can be determined without strong constraints on absorption-line variability provided enough energy levels are detected. From the cloud size, we infer a particle density of n H ≈ 5−15 cm −3 . Conclusions.We discuss these results in the context of no detections of H 2 and C i lines (with log N(C 0 )/N(S + ) < −3) in a sample of seven z > 1.8 GRB host galaxies observed with VLT/UVES. We show that the lack of H 2 can be explained by the low metallicities, [X/H] < −1, low depletion factors, and, at most, moderate particle densities of the systems. This points to a picture where GRB-DLAs typically exhibiting very high H 0 column densities are diffuse metal-poor atomic clouds with high kinetic temperatures, T kin > ∼ 1000 K, and large physical extents, l > ∼ 100 pc. The properties of GRB-DLAs observed at high spectral resolution towards bright GRB afterglows differ markedly from the high metal and dust contents of GRB-DLAs observed at lower resolution. This difference likely results from the effect of a bias, against systems of high metallicity and/or close to the GRB, due to dust obscuration in the magnitudelimited GRB afterglow samples observed with high-resolution spectrographs.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 84%

Section: Grb-dla Gas Distance and H 2 Photo-dissociationmentioning

confidence: 92%

Section: Modelmentioning

confidence: 94%

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Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

Ledoux¹,

Vreeswijk

Smette³

et al. 2009

A&A

Self Cite

160

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“…It is well known that the absorption in the X-ray afterglows of some GRBs appears to decrease as a function of time (e.g. Starling et al 2005;Gendre et al 2007;Campana et al 2007). For this reason, it is often preferable to choose the later PC data, as it is likely to be closer to the Galactic value.…”

Section: Sample Selection Data Reduction and Analysismentioning

confidence: 99%

The Galactic dust-to-metals ratio and metallicity using gamma-ray bursts

Watson

2011

A&A

112

108

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The metallicity and dust-to-metals ratio of the Galaxy are fundamental parameters in understanding the interstellar medium (ISM). Currently, there is still some uncertainty surrounding these parameters. In this paper, the dust-to-metals ratio in the Galaxy is determined using the photoelectric absorption of the soft X-ray afterglows of a large sample of several hundred gamma-ray bursts (GRBs) to determine the metal column density in combination with Galactic dust maps to determine the line-of-sight dust extinction through the Galaxy in the direction of the GRB. GRB afterglows often have large extragalactic soft X-ray absorptions and therefore the GRB sample's upper-bound will define the Galactic dust-to-metals relation. Using a two-dimensional two-sample Kolmogorov-Smirnoff test, we determine this upper-bound and so derive the dust-to-metals ratio of the Galaxy. We find N H = 2.2 +0.3 −0.4 × 10 21 cm −2 A V asassuming solar, Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197), metallicity. This result is consistent with previous findings using bright X-ray sources in the Galaxy. Using the same technique but substituting the H i maps from the Leiden-ArgentineBonn survey for the dust maps, allows us to place a limit on the metallicity in the Galaxy. We find a metallicity consistent with the Anders & Grevesse (1989) solar values often used in X-ray fitting. Based on this and previous studies, we suggest that the metallicity of a typical ISM sightline through the Galaxy is ∼0.25 dex higher than the current best estimate of the solar metallicity. We further show that the dust-to-gas ratio seems to be correlated with the total gas column density, and that this may be due to the metallicity gradient observed toward the Galactic centre. Based on the non-constant nature of the dust-to-gas ratio, we propose that the dust column density, at N H = 2.2 × 10 21 cm −2 A V , represents a better proxy for the soft X-ray absorption column density than H i maps.

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GRB‐selected galaxies

et al. 2011

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We describe the current status and recent results from our Swift/VLT legacy survey, a VLT Large Programme aimed at characterizing the host galaxies of a homogeneously selected sub-sample of Swift gamma-ray bursts (GRBs). The immediate goals are to determine the host luminosity function, study the effects of reddening, determine the fraction of Lyα emitters in the hosts, and obtain redshifts for targets without a reported one. We have defined a very carefully selected sample, obeying strict and well-defined criteria: 68 targets in total. Among the preliminary results is a large optical detection rate, the lack of extremely red objects (only one possible case in the sample), and 10 new GRB redshifts with the mean redshift of the host sample assessed to be z 2.

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Gas and dust properties in the afterglow spectra of GRB 050730

Cited by 70 publications

References 25 publications

Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

The Galactic dust-to-metals ratio and metallicity using gamma-ray bursts

GRB‐selected galaxies

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