Cold gas in the early Universe

Heintz, K. E.; Ledoux, C.; Fynbo, J. P. U.; Jakobsson, P.; Noterdaeme, P.; Krogager, J.-K.; Bolmer, J.; Møller, P.; Vergani, S. D.; Watson, D.; Zafar, T.; De, A.; Tanvir, N. R.; Malesani, D.; Japelj, J.; Covino, S.; Kaper, L.

doi:10.1051/0004-6361/201834246

Cited by 19 publications

(24 citation statements)

References 106 publications

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“…. We find no evidence for C i in this absorption system (see also Heintz et al 2019a), and derive a 2σ upper limit of log N(C i) tot < 14.0 assuming b = 2 km s −1 .…”

Section: Appendix B: Individual Notes On Sample Xs-grbsmentioning

confidence: 59%

“…D'Elia et al(2014) derived an upper limit on the visual extinction along the line of sight to this GRB of A V < 0.03 mag. We find no evidence for C i in this absorption system (see alsoHeintz et al 2019a), and derive a 2σ upper limit of log N(C i) tot < 14.3 assuming b = 2 km s −1 .Article number, page 17 of 21 A&A proofs: manuscript no. h2physprop_acc .1.…”

mentioning

confidence: 71%

“…The amount of C i has been observed to be correlated with the visual extinction, A V , in the line of sight to quasar and GRB absorbers (Ledoux et al 2015;Ma et al 2018;Heintz et al 2019a), suggesting a common origin for the main extinction-derived dust component and C i (see also Heintz et al 2019b). In Fig.…”

Section: The Connection Between Dust and Molecular Gasmentioning

confidence: 98%

“…Srianand et al 2005;Noterdaeme et al 2018). This collection is therefore not an unbiased representation of the GRB population as a whole, but rather a compilation of GRB afterglows where a determination of the relative gas content and the physical conditions in the molecular Article number, page 3 of 21 0 1 1 2 2 3 3 0 1 1 2 2 3 3 0 1 1 2 2 3 3 0 1 1 2 2 3 3 0 1 1 2 2 3 gas-phase is possible (see instead Heintz et al 2019a for statistical analyses of the presence of H 2 and C i in GRB afterglows). In total, we compiled ten XS-GRBs with H 2 and/or C i detected in absorption, listed in Table 1.…”

Section: Observations and Sample Descriptionmentioning

confidence: 99%

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New constraints on the physical conditions in H₂-bearing GRB-host damped Lyman-α absorbers

Heintz

Bolmer

Ledoux

et al. 2019

A&A

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We report the detections of molecular hydrogen (H 2 ), vibrationally-excited H 2 (H * 2 ), and neutral atomic carbon (C i), an efficient tracer of molecular gas, in two new afterglow spectra of GRBs 181020A (z = 2.938) and 190114A (z = 3.376), observed with X-shooter at the Very Large Telescope (VLT). Both host-galaxy absorption systems are characterized by strong damped Lyman-α absorbers (DLAs) and substantial amounts of molecular hydrogen with log N(H i, H 2 ) = 22.20 ± 0.05, 20.40 ± 0.04 (GRB 181020A) and log N(H i, H 2 ) = 22.15 ± 0.05, 19.44 ± 0.04 (GRB 190114A). The DLA metallicites, depletion levels and dust extinctions are within the typical regimes probed by GRBs with [Zn/H] = −1.57 ± 0.06, [Zn/Fe] = 0.67 ± 0.03, and A V = 0.27 ± 0.02 mag (GRB 181020A) and [Zn/H] = −1.23 ± 0.07, [Zn/Fe] = 1.06 ± 0.08, and A V = 0.36 ± 0.02 mag (GRB 190114A). In addition, we examine the molecular gas content of all known H 2 -bearing GRB-DLAs and explore the physical conditions and characteristics required to simultaneously probe C i and H * 2 . We confirm that H 2 is detected in all C i-and H * 2 -bearing GRB absorption systems, but that these rarer features are not necessarily detected in all GRB H 2 absorbers. We find that a large molecular fraction of f H 2 10 −3 is required for C i to be detected. The defining characteristic for H * 2 to be present is less clear, though a large H 2 column density is an essential factor. We find that the observed line profiles of the molecular-gas tracers are kinematically 'cold', with small velocity offsets of δv < 20 km s −1 from the bulk of the neutral absorbing gas. We then derive the H 2 excitation temperatures of the molecular gas and find that they are relatively low with T ex ≈ 100 − 300 K, however, there could be evidence of warmer components populating the high-J H 2 levels in GRBs 181020A and 190114A. Finally, we demonstrate that even though the X-shooter GRB afterglow campaign has been successful in recovering several H 2 -bearing GRB-host absorbers, this sample is still hampered by a significant dust bias excluding the most dust-obscured H 2 absorbers from identification. C i and H * 2 could open a potential route to identify molecular gas even in low-metallicity or highly dust-obscured bursts, though they are only efficient tracers for the most H 2 -rich GRB-host absorption systems.

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“…. We find no evidence for C i in this absorption system (see also Heintz et al 2019a), and derive a 2σ upper limit of log N(C i) tot < 14.0 assuming b = 2 km s −1 .…”

Section: Appendix B: Individual Notes On Sample Xs-grbsmentioning

confidence: 59%

mentioning

confidence: 71%

Section: The Connection Between Dust and Molecular Gasmentioning

confidence: 98%

Section: Observations and Sample Descriptionmentioning

confidence: 99%

See 2 more Smart Citations

New constraints on the physical conditions in H₂-bearing GRB-host damped Lyman-α absorbers

Heintz

Bolmer

Ledoux

et al. 2019

A&A

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“…The cause of this putative discrepancy between the dust content inferred from the extinguished afterglow SED and the gasphase depletion levels, might also be related to a too simplistic view of the location of the dust. Recent studies of GRB and quasar absorbers have for instance found that the visual extinction, A V , and the strength of the 2175 Å extinction bump feature is correlated with the amount of neutral atomic-carbon (C i; Zafar et al 2012;Ledoux et al 2015;Ma et al 2018;Heintz et al 2019). Absorption features from C i are often found to be coincident with H 2 (Srianand et al 2005;Jorgenson et al 2010;Noterdaeme et al 2018) and is therefore believed to be a good tracer of the cold and molecular gas-phase of the ISM.…”

Section: Introductionmentioning

confidence: 99%

On the dust properties of high-redshift molecular clouds and the connection to the 2175 Å extinction bump

Heintz

Zafar

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present a study of the extinction and depletion-derived dust properties of gamma-ray burst (GRB) absorbers at 1 < z < 3 showing the presence of neutral carbon (C i). By modelling their parametric extinction laws, we discover a broad range of dust models characterizing the GRB C i absorption systems. In addition to the already well-established correlation between the amount of C i and visual extinction, A V , we also observe a correlation with the total-toselective reddening, R V . All three quantities are also found to be connected to the presence and strength of the 2175 Å dust extinction feature. While the amount of C i is found to be correlated with the SED-derived dust properties, we do not find any evidence for a connection with the depletion-derived dust content as measured from [Zn/Fe] and N(Fe) dust . To reconcile this, we discuss a scenario where the observed extinction is dominated by the composition of dust particles confined in the molecular gas-phase of the ISM. We argue that since the depletion level trace non-carbonaceous dust in the ISM, the observed extinction in GRB C i absorbers is primarily produced by carbon-rich dust in the molecular cloud and is therefore only observable in the extinction curves and not in the depletion patterns. This also indicates that the 2175 Å dust extinction feature is caused by dust and molecules in the cold and molecular gas-phase. This scenario provides a possible resolution to the discrepancy between the depletion-and SED-derived amounts of dust in high-z absorbers.

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Evidence for diffuse molecular gas and dust in the hearts of gamma-ray burst host galaxies

Bolmer

Ledoux

Wiseman

et al. 2019

A&A

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Context. Damped Lyman-α absorption-line systems at the redshifts of gamma-ray burst afterglows offer a unique way to probe the physical conditions within star-forming galaxies in the early Universe. Aims. Here we built up a large sample of 22 GRBs at redshifts z > 2 observed with VLT/X-shooter in order to determine the abundances of hydrogen, metals, dust, and molecular species. This allows us to study the metallicity and dust depletion effects in the neutral interstellar medium at high redshift and to answer the question whether (and why) there might be a lack of H 2 in GRB-DLAs. Methods. We developed new, state-of-the-art methods based on the Bayesian inference package, PyMC, to fit absorption lines and measure the column densities of different metal species as well as atomic and molecular hydrogen. The derived relative abundances are used to fit dust depletion sequences and determine the dust-to-metals ratio and the host-galaxy intrinsic visual extinction. Additionally, we searched for the absorption signatures of vibrationally-excited H 2 and carbon monoxide.Results. There is no lack of H 2 -bearing GRB-DLAs. We detect absorption lines from molecular hydrogen in 6 out of 22 GRB afterglow spectra, with molecular fractions ranging between f 5 · 10 −5 and f 0.04, and claim tentative detections in three other cases. For the remaining sample, we measure, depending on S/N, spectral coverage and instrumental resolution, more or less stringent upper limits. The GRB-DLAs in the present sample have on average low metallicities ([X/H] ≈ −1.3), comparable to the rare population of extremely strong QSO-DLAs (log N(H i) > 21.5). Furthermore, H 2 -bearing GRB-DLAs are found to be associated with significant dust extinction, A V > 0.1 mag, and have dust-to-metals ratios DTM > 0.4. All of these systems exhibit neutral hydrogen column densities of log N(H i) > 21.7. The overall fraction of H 2 detections is ≥ 27% (41% including tentative detections), which is three to four times larger than in the general population of QSO-DLAs. For 2 < z < 4, and considering column densities log N(H i) > 21.7, the H 2 detection fraction is 60-80% in GRB-DLAs as well as in extremely strong QSO-DLAs. This is likely a consequence of the fact that both GRB-and QSO-DLAs with high neutral hydrogen column densities probe sight-lines with small impact parameters that indicate that the absorbing gas is associated with the inner regions of the absorbing galaxy, where the gas pressure is higher and the conversion of H i to H 2 takes place. In the case of GRB hosts, this diffuse molecular gas is located at distances 500 pc and hence is unrelated to the star-forming region where the GRB explosion occurred.

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Cold gas in the early Universe

Cited by 19 publications

References 106 publications

New constraints on the physical conditions in H₂-bearing GRB-host damped Lyman-α absorbers

New constraints on the physical conditions in H₂-bearing GRB-host damped Lyman-α absorbers

On the dust properties of high-redshift molecular clouds and the connection to the 2175 Å extinction bump

Evidence for diffuse molecular gas and dust in the hearts of gamma-ray burst host galaxies

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Cold gas in the early Universe

Cited by 19 publications

References 106 publications

New constraints on the physical conditions in H2-bearing GRB-host damped Lyman-α absorbers

New constraints on the physical conditions in H2-bearing GRB-host damped Lyman-α absorbers

On the dust properties of high-redshift molecular clouds and the connection to the 2175 Å extinction bump

Evidence for diffuse molecular gas and dust in the hearts of gamma-ray burst host galaxies

Contact Info

Product

Resources

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New constraints on the physical conditions in H₂-bearing GRB-host damped Lyman-α absorbers

New constraints on the physical conditions in H₂-bearing GRB-host damped Lyman-α absorbers