VLT/X-Shooter spectroscopy of the afterglow of the<i>Swift</i>GRB 130606A

We study metal depletion due to dust in the interstellar medium (ISM) to infer the properties of dust grains and characterize the metal and dust content of galaxies down to low metallicity and intermediate redshift z. We provide metal column densities and abundances of a sample of 70 damped Lyman-α absorbers (DLAs) towards quasars, observed at high spectral resolution with the Very Large Telescope (VLT) Ultraviolet and Visual Echelle Spectrograph (UVES). This is the largest sample of phosphorus abundances measured in DLAs so far. We use literature measurements for Galactic clouds to cover the high-metallicity end. We discover tight (scatter 0.2 dex) correlations between [Zn/Fe] and the observed relative abundances from dust depletion. This implies that grain growth in the ISM is an important process of dust production. These sequences are continuous in [Zn/Fe] from dust-free to dusty DLAs, and to Galactic clouds, suggesting that the availability of refractory metals in the ISM is crucial for dust production, regardless of the star formation history. We observe [S/Zn] up to ∼ 0.25 dex in DLAs, which is broadly consistent with Galactic stellar abundances. Furthermore, we find a good agreement between the nucleosynthetic pattern of Galactic halo stars and our observations of the least dusty DLAs. This supports recent star formation in low-metallicity DLAs. The derived depletions of Zn, O, P, S, Si, Mg, Mn, Cr, and Fe correlate with [Zn/Fe], with steeper slopes for more refractory elements. P is mostly not affected by dust depletion. We present canonical depletion patterns to be used as reference in future studies of relative abundances and depletion. We derive the total (dust-corrected) metallicity, typically −2 [M/H] tot 0 for DLAs, and scattered around solar metallicity for the Galactic ISM. The dust-to-metal ratio (DTM) increases with metallicity, again supporting the importance of grain growth for dust production. The dust extinction A V derived from the depletion is typically < 0.2 mag in DLAs. Finally, we derive elemental abundances in dust, which is key to understanding the dust composition and its evolution. We observe similar abundances of Mg, Si, and Fe in dust; this suggests that grain species such as pyroxenes and iron oxides are more important than olivine, but this needs to be confirmed by more detailed analysis. Overall, we characterize dust depletion, nucleosynthesis, and dust-corrected metallicity in DLAs, providing a unified picture from low-metallicity systems to the Galactic ISM.

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“…for GRB/,130606A at z ∼ 6, Hartoog et al 2015). The largest reservoirs of neutral gas in the Universe (e.g.…”

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confidence: 99%

Dust-depletion sequences in damped Lyman-αabsorbers

Ledoux

Mattsson

et al. 2016

A&A

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169

186

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“…Pink and purple diamonds with error bar are the result of the same QSO fromTang et al (2017). The rest of the data points are from previous studies(Hartoog et al 2015;Bosman et al 2018;Eilers et al 2018) as indicated in the legend. Data points fromTang et al (2017) are measured through the same LOS as this work, whileHartoog et al (2015) is measured from a gamma-ray burst spectrum.…”

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confidence: 99%

Subaru Medium-resolution Spectra of a QSO at z = 6.62: Three Reionization Tests

Goto

Tang

et al. 2020

ApJ

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Investigating the Gunn-Peterson trough of high redshift quasars (QSOs) is a powerful way to reveal the cosmic reionization. As one of such attempts, we perform a series of analyses to examine the absorption lines observed with one of the highest redshift QSOs, PSO J006.1240+39.2219, which we previously discovered at z = 6.62. Using the Subaru telescope, we obtained medium-resolution spectrum with a total exposure time of 7.5 hours. We calculate the Lyα transmission in different redshift bins to determine the near zone radius and the optical depth at 5.6< z <6.5. We find a sudden change in the Lyα transmission at 5.75< z <5.86, which is consistent with the result from the literature. The near zone radius of the QSO is 5.79±0.09 pMpc, within the scatter of the near zone radii of other QSOs measured in previous studies. We also analyze the dark gap distribution to probe the neutral hydrogen fractions beyond the saturation limit of the Gunn-Peterson trough. We extend the measurement of the dark gaps to 5.7< z <6.3. We find that the gap widths increase with increasing redshifts, suggesting more neutral Universe at higher redshifts. However, these measurements strongly depend on the continuum modeling. As a continuum model-free attempt, we also perform the dark-pixel counting analysis, to find the upper limit of x HI ∼0.6 (0.8) at z <5.8 (z >5.8). All three analyses based on this QSO show increasingly neutral hydrogen towards higher redshifts, adding precious measurements up to z ∼6.5.

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“…However, recent studies of extremely saturated DLAs (ESDLA) (Noterdaeme et al 2014(Noterdaeme et al , 2015aBalashev et al 2017;Ranjan et al 2018;Bolmer et al 2019;Ranjan et al 2020) indicate that ESDLAs and GRB-DLAs likely represent the same population of the galaxies, probed by small impact parameters, and hence can probe star-forming regions. Furthermore, recently, a huge data is also available on GRB-DLA host galaxies up to a very high redshift (z≈ 6) (Hartoog et al 2015;Bolmer et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Physical conditions in two high-redshift H2-bearing GRB-DLAs, 120815A and 121024A

Shaw

Ferland

2020

Monthly Notices of the Royal Astronomical Society

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The gamma-ray burst (GRB) afterglows provide an unique opportunity to study the interstellar medium (ISM) of star-forming galaxies at high-redshift. The GRB-DLAs (damped Lyman-α absorbers) contain a large neutral hydrogen column density, N(H I), and are observed against the GRB afterglow. A large fraction of GRB-DLAs show presence of molecular hydrogen (H 2 ) which is an indicator of star-formation. Hence it is important to study those GRB-DLAs which have H 2 lines to decipher and understand their physical conditions. The GRB-DLAs 121024A and 120815A, situated at redshift 2.30 and 2.36 respectively, are two such important H 2 -bearing GRB-DLAs. Besides H 2 , these two GRB-DLAs also show many metal lines. In this work we have carried out a detail numerical study on the H 2 lines, as well as on those metal lines, in GRB-DLAs 121024A and 120815A self-consistently. We use the spectral synthesis code CLOUDY for this study. This modeling helps us to determine the underlying physical conditions which give rise such lines and hence to understand these two GRB-DLAs in much more detail than any other previous investigation. We find that the hydrogen densities for these two H 2 -bearing DLAs are ≥ 60 cm −3 . Moreover our study infers that the linear sizes are ≤ 17.7 pc for these two GRB-DLAs, and the mean gas temperatures averaged over the cloud thickness, are ≤ 140 K. Overall, we find that these two H 2 -bearing GRB-DLAs are denser, cooler and smaller compared to those without H 2 .

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VLT/X-Shooter spectroscopy of the afterglow of theSwiftGRB 130606A

Cited by 95 publications

References 95 publications

Dust-depletion sequences in damped Lyman-αabsorbers

Dust-depletion sequences in damped Lyman-αabsorbers

Subaru Medium-resolution Spectra of a QSO at z = 6.62: Three Reionization Tests

Physical conditions in two high-redshift H2-bearing GRB-DLAs, 120815A and 121024A

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