THE FIRST POSITIVE DETECTION OF MOLECULAR GAS IN A GRB HOST GALAXY

By J. Xavier Prochaska, Y. Sheffer, D. Perley, Joshua S. Bloom, L. Lopez, M. Dessauges-Zavadsky, H. Chen, A. Filippenko, M. Ganeshalingam, W. Li and 8 more. 2009

150 citations recorded by the source corpus.

We report on strong H2 and CO absorption from gas within the host galaxy of gamma-ray burst (GRB) 080607. Analysis of our Keck/LRIS afterglow spectrum reveals a very large H i column density () and strong metal-line absorption at zGRB = 3.0363 with a roughly solar metallicity. We detect a series of A − X bandheads from CO and estimate N(CO) = 1016.5±0.3 cm−2 and TCOex > 100 K. We argue that the high excitation temperature results from UV pumping of the CO gas by the GRB afterglow. Similarly, we observe H2 absorption via the Lyman–Werner bands and estimate with –300 K. The afterglow photometry suggests an extinction law with RV ≈ 4 and AV ≈ 3.2 mag and requires the presence of a modest 2175 Å bump. Additionally, modeling of the Swift XRT X-ray spectrum confirms a large column density with NH = 1022.58±0.04 cm-2. Remarkably, this molecular gas has extinction properties, metallicity, and a CO/H2 ratio comparable to those of translucent molecular clouds of the Milky Way, suggesting that star formation at high z proceeds in similar environments as today. However, the integrated dust-to-metals ratio is sub-Galactic, suggesting the dust is primarily associated with the molecular phase while the atomic gas has a much lower dust-to-gas ratio. Sightlines like GRB 080607 serve as powerful probes of nucleosynthesis and star-forming regions in the young universe and contribute to the population of “dark” GRB afterglows.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c7a36fab8a4bef254e2b8f1125cd61a088caddbf

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In Astronomy and Astrophysics

1. Bing Zhang
2. E. Berger
3. D. Schneider
4. B. Metzger
5. L. Hernquist
6. P. Hopkins
7. P. Petitjean
8. J. Silverman

In Instrumentation

1. D. Schneider
2. N. Ross
3. Adam D. Myers
4. Karl Glazebrook
5. Lisa J. Kewley
6. E. Berger
7. J. Silverman
8. Iap Paris

Citations in the corpus

• GRB hosts through cosmic time - VLT/X-Shooter emission-line spectroscopy of 96 γ-ray-burst-selected galaxies at 0.1 (2015, background): “In particular the information that is obtained through afterglow spectroscopy provides insights of unprecedented detail into the chemical composition of high-redshift galaxies (e.g., Fynbo et al. 2006; Prochaska et al. 2009; Thöne et al. 2013; Cucchiara et al. 2015).”
• A POPULATION OF MASSIVE, LUMINOUS GALAXIES HOSTING HEAVILY DUST-OBSCURED GAMMA-RAY BURSTS: IMPLICATIONS FOR THE USE OF GRBs AS TRACERS OF COSMIC STAR FORMATION (2013, background): “…absorption bump; Perley et al. 2011), an afterglow spectrum rich in ionic and molecular absorption features from a molecular cloud within the host along the line of sight (Prochaska et al. 2009; Sheffer et al. 2009), and the relatively high redshift of the system (z = 3.038 from the same spectra).”
• Gamma-Ray Bursts in the Swift Era (2009, background): “…2008); discovery of high-ionization N V features, providing evidence for absorption by gas within d ∼< 10 pc of the burst (Fox et al. 2008, Prochaska et al. 2008); and most recently, the first detection of molecular gas along the line of sight to a GRB afterglow (Figure 13; Prochaska et al. 2009).”
• THE HOST GALAXIES OF SWIFT DARK GAMMA-RAY BURSTS: OBSERVATIONAL CONSTRAINTS ON HIGHLY OBSCURED AND VERY HIGH REDSHIFT GRBs (2009, background): “…and infrared photometry of the extremely bright GRB 080607 at z = 3.036 revealed a strongly extinguished (AV = 3.2 ± 0.5) event, showing a clear 2175Å bump and an abundance of molecular and ionic lines associated with a nearby molecular cloud with Solar-like metallicity (Prochaska et al. 2009).”
• The nature of "dark" gamma-ray bursts (2010, background): “From individual bursts not in this sample there is evidence that bursts with evenAV ∼ 3− 5 exist (e.g. GRB 080607, Prochaska et al. (2009); GRB 070306, Jaunsen et al. (2008)) – though these are admittedly rare occasions which require larger samples to include them.”
• THE HOST GALAXIES OF GAMMA-RAY BURSTS. II. A MASS–METALLICITY RELATION FOR LONG-DURATION GAMMA-RAY BURST HOST GALAXIES (2010, background): “…studies have measured high metallicities in other LGRB host galaxies based on afterglow spectra (e.g. Watson et al. 2006, Eĺıasdóttir et al. 2009, Prochaska et al. 2009), the relationship between afterglow absorption metallicities and emission-line metallicities has not yet been examined, and…”
• Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9 (2012, background): “…via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/547/L1 The most recent contributions to the census of DLAs have used data mining of thousands of quasar spectra from the SDSS (SDSS, York et al. 2000) by Prochaska et al. (2005), Prochaska et al. (2009), and Noterdaeme et al. (2009, hereafter N09).”
• The SEDs and host galaxies of the dustiest GRB afterglows (2011, background): “The afterglow of GRB 080607 is heavily reddened (AV ∼ 3 mag), has a modest 2175 Å dust feature, and is characterized by a strong neutral hydrogen absorber of roughly solar metallicity and molecular gas (Prochaska et al. 2009; Perley et al. 2011b).”