Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs along Gamma-Ray Bursts

Cucchiara, A.; Fumagalli, M.; Rafelski, M.; Kocevski, D.; Prochaska, J.X.; Cooke, R.J.; Becker, G.D.

Abstract

We present the largest, publicly available sample of damped Lyα systems (DLAs) along the lines of sight of Swift-discovered gamma-ray bursts (GRBs) in order to investigate the environmental properties of long GRB hosts in the z = 1.8–6 redshift range. Compared with the most recent quasar DLA sample (QSO-DLA), our analysis shows that GRB-DLAs probe a more metal-enriched environment at $z\gtrsim 3$, up to $[X/H]\sim -0.5$. In the z = 2–3 redshift range, despite the large number of lower limits, there are hints that the two populations may be more similar (only at a 90% significance level) than at higher redshifts. Also, at high-z, the GRB-DLA average metallicity seems to decline at a lower rate than the QSO-DLAs: GRB-DLA hosts may be polluted with metals at least as far as $\sim 2\;$ kpc from the GRB explosion site, probably due to previous star formation episodes and/or supernova explosions. This shallow metallicity trend, now extended up to $z\sim 5$, confirms previous results that GRB hosts are star-forming and have, on average, higher metallicities than the general QSO-DLA population. Finally, our host metallicity measurements are broadly consistent with the predictions derived from the hypothesis of two channels of GRB progenitors, one of which is mildly affected by a metallicity bias, although more data are needed to constrain the models at $z\gtrsim 4$.

Citation

Cucchiara, A., Fumagalli, M., Rafelski, M., Kocevski, D., Prochaska, J., Cooke, R., & Becker, G. (2015). Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs along Gamma-Ray Bursts. Astrophysical Journal, 804(1), https://doi.org/10.1088/0004-637x/804/1/51

• Journal Article Type: Article
• Acceptance Date: Feb 17, 2015
• Publication Date: May 1, 2015
• Deposit Date: May 28, 2015
• Publicly Available Date: May 28, 2015
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 804
• Issue: 1
• DOI: https://doi.org/10.1088/0004-637x/804/1/51
• Keywords: Galaxies: general, Galaxies: ISM, Gamma-ray burst: general, Quasars: absorption lines, Techniques: imaging spectroscopy.
• Public URL: https://durham-repository.worktribe.com/output/1427857