High Column Densities and Low Extinctions of Gamma-Ray Bursts: Evidence for Hypernovae and Dust Destruction

By T. Galama, R. Wijers. 2000

180 citations recorded by the source corpus.

We analyze a complete sample of γ-ray burst afterglows and find X-ray evidence for high column densities of gas around them. The column densities are in the range 1022-1023 cm-2, which is right around the average column density of Galactic giant molecular clouds. We also estimate the cloud sizes to be 10-30 pc, implying masses ≳105 M☉. This strongly suggests that γ-ray bursts lie within star-forming regions and therefore argues against neutron star mergers and for collapses of massive stars as their sources. The optical extinctions, however, are 10-100 times smaller than expected from the high column densities. This confirms theoretical findings that the early hard radiation from γ-ray bursts and their afterglows can destroy the dust in their environment, thus carving a path for the afterglow light out of the molecular cloud. Because of the self-created low extinction and location in star-forming regions, we expect γ-ray bursts to provide a relatively unbiased sample of high-redshift star formation. Thus, they may help resolve what is the typical environment of high-redshift star formation.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5d9bf3faf1bfa2afe4e2efbcc370f9f0fafa5543

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In Astronomy and Astrophysics

1. Bing Zhang
2. C. Matzner
3. Mark R. Krumholz
4. P. Hopkins
5. C. McKee
6. E. Berger
7. Jonathan C. Tan
8. E. Quataert

Citations in the corpus

• Signatures of Extragalactic Dust in Pre-Swift GRB Afterglows (2005, background): “This is an update of the plot first presented in Galama & Wijers (2001) and expanded in Stratta et al. (2004).4 The results reinforce our findings presented in x 3.1.”
• The SEDs and host galaxies of the dustiest GRB afterglows (2011, methodology): “For the afterglow SED analysis, X-ray (0.3−10 keV) and optical/NIR data were fit together under the assumption that the underlying continuum emission is well-represented by synchrotron emission (e.g., Sari et al. 1998; Galama & Wijers 2001; Schady et al. 2007; Rossi et al. 2011a).”
• Probing the Interstellar Medium near Star-forming Regions with Gamma-Ray Burst Afterglow Spectroscopy: Gas, Metals, and Dust (2007, result): “In this respect, studies of the ISM along sightlines to GRBs complement those toward quasars.”
• The nature of "dark" gamma-ray bursts (2010, result): “As has been noted frequently in the past (e.g. Galama & Wijers, 2001; Stratta et al., 2004; Schady et al., 2010), theNH-to-AV ratio is far from being similar among different bursts, and substantially larger than in our Galaxy.”
• Properties of Relativistic Jets in Gamma-Ray Burst Afterglows (2001, background): “These values are 2–5 orders of magnitude smaller than those implied by the NH column densities inferred by Galama & Wijers (2001) for 970508, 980519, 980703, 990123, and 990510 from the absorption seen in their soft X-ray spectra.”
• Trans-Relativistic Blast Waves in Supernovae as Gamma-Ray Burst Progenitors (2000, background): “…host galaxies (Bloom, Kulkarni, & Djorgovski 2000b), but there is only tentative evidence for a direct association with star-forming regions (Kulkarni et al. 2000 ; Djorgovski, Bloom, & Kulkarni 2000 ; Galama & Wijers 2001), which would be expected if they arose from the deaths of massive stars.”
• Supernova hosts for gamma-ray burst jets: dynamical constraints (2002, background): “Several GRB afterglows show evidence for high column densities (980703 and 980329; Galama & Wijers 2001) or high local gas densities (000926 and 980519; Harrison et al. 2001; Wang, Dai & Lu 2000), both of which connote star-forming regions.”
• Are the hosts of gamma-ray bursts sub-luminous and blue galaxies? (2003, background): “These include the presence of dust extinction in the X-ray and optical transients (e.g., Galama & Wijers 2001), the spectral energy distribution and morphology of GRB hosts consistent with compact, irregular or merger-driven starbursts (e.g., Hjorth et al. 2002; Sokolov et al. 2001; Djorgovski et…”
• Swift Identification of Dark Gamma-Ray Bursts (2004, background): “In some cases, though, it is either positioned below the optical or above the X-rays.”
• Theories of Gamma-Ray Bursts (2001, background): “Also, standard afterglow model fits indicate an ambient gas density generally lower than that expected in star-forming clouds (Galama & Wijers 2001, Panaitescu & Kumar 2001b).”
• THE FIRST POSITIVE DETECTION OF MOLECULAR GAS IN A GRB HOST GALAXY (2009, background): “We conclude that the gas has a much lower dustto-metals ratio than Galactic (Galama & Wijers 2001; Watson et al. 2006).”