The Observed Offset Distribution of Gamma-Ray Bursts from Their Host Galaxies: A Robust Clue to the Nature of the Progenitors

By Joshua S. Bloom, Shrinivas R. Kulkarni, S. George Djorgovski. 2000

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We present a comprehensive study to measure the locations of gamma-ray bursts (GRBs) relative to their host galaxies. In total, we find the offsets of 20 long-duration GRBs from their apparent host galaxy centers by utilizing ground-based images from Palomar and Keck and space-based images from the Hubble Space Telescope (HST). We discuss in detail how a host galaxy is assigned to an individual GRB and the robustness of the assignment process. The median projected angular (physical) offset is 0.″17 (1.3 kpc). The median offset normalized by the individual host half-light radii is 0.98, suggesting a strong connection of GRB locations with the UV light of their hosts. This provides strong observational evidence for the connection of GRBs to star formation. We further compare the observed offset distribution with the predicted burst locations of leading stellar-mass progenitor models. In particular, we compare the observed offset distribution with an exponential disk, a model for the location of collapsars and promptly bursting binaries (e.g., helium star–black hole binaries). The statistical comparison shows good agreement, given the simplicity of the model, with the Kolmogorov-Smirnov probability that the observed offsets derive from the model distribution of PKS = 0.45. We also compare the observed GRB offsets with the expected offset distribution of delayed merging remnant progenitors (black hole–neutron star and neutron star–neutron star binaries). We find that delayed merging remnant progenitors, insofar as the predicted offset distributions from population synthesis studies are representative, can be ruled out at the 2 × 10-3 level. This is arguably the strongest observational constraint yet against delayed merging remnants as the progenitors of long-duration GRBs. In the course of this study, we have also discovered the putative host galaxies of GRB 990510 and GRB 990308 in archival HST data.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c8967ac1c5dccc249aed9cb52fc1fef6d309fa89

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In Astronomy and Astrophysics

1. Bing Zhang
2. E. Berger
3. B. Metzger
4. Pawan Kumar
5. E. Quataert
6. A. Filippenko
7. S. Smartt
8. E. Nakar

Citations in the corpus

• A NEW POPULATION OF ULTRA-LONG DURATION GAMMA-RAY BURSTS (2013, background): “Astrometric constraints A crucial diagnostic as to the nature of any transient event is its location within its host galaxy (e.g., Bloom et al. 2002; Fruchter et al. 2006; Svensson et al. 2010b; Fong et al. 2010; Anderson & James 2009).”
• THE OPTICALLY UNBIASED GAMMA-RAY BURST HOST (TOUGH) SURVEY. I. SURVEY DESIGN AND CATALOGS (2012, background): “Following the discovery of long-duration gamma-ray burst (GRB) optical afterglows (e.g., van Paradijs et al. 2000), evidence rapidly accumulated pointing to their origin in the deaths of massive stars (Galama et al. 1998; Bloom et al. 2002; Stanek et al. 2003; Hjorth et al. 2003).”
• On the Lyalpha emission from gamma-ray burst host galaxies: Evidence for low metallicities (2003, background): “The impact parameters of afterglows relative to their hosts are small enough, typically a fraction of an arcsec on the sky, that chance alignment is not a serious limitation (Bloom et al. 2002).”
• Photometry and Spectroscopy of GRB 030329 and Its Associated Supernova 2003dh: The First Two Months (2003, methodology): “A bum p in thelightcurvewasobserved both from the ground and with HST (Garnavich et al.2003a;Bloom et al.2002).”
• The physics of gamma-ray bursts (2004, background): “…colors of GRB hosts are not distinguishable from those of normal field galaxies at comparable magnitudes and redshifts sSokolov et al., 2001; Bloom, Kulkarni, and Djorgovski, 2002d, others sFruchter et al., 1999d assert that the host galaxies are unusually blue and that they are strongly…”
• High-resolution calculations of merging neutron stars - III. Gamma-ray bursts (2003, background): “Searches for host galaxies of gamma-ray bursts may thus help limit the possible progenitors (see e.g. Bloom et al. 2002) providing we have a reasonable understanding of the distribution of merger times and accurate galactic models.”
• Early-Time Photometry and Spectroscopy of the Fast Evolving SN 2006aj Associated with GRB 060218 (2006, background): “Circumstantial evidence includes the location of GRBs near sites of massive star formation (Bloom et al. 2002) and the detection of unusual " bumps " in the GRB afterglow light curves that mimic a SN light curve and its colors (e.g., Bloom et al. 1999; Garnavich et al. 2003).”
• The First Stars (2003, background): “Although the nature of the central engine that powers the relativistic jets is still debated, recent evidence indicates that GRBs trace the formation of massive stars (e.g., Bloom et al. 2002, and references therein).”
• The Propagation and Eruption of Relativistic Jets from the Stellar Progenitors of Gamma-Ray Bursts (2003, background): “In addition to the observed association with star-forming regions in galaxies (Vreeswijk et al. 2001; Bloom et al. 2002a; Gorosabel et al. 2003), ‘‘bumps’’ observed in the afterglows of many GRBs (Reichart 1999; Galama et al. 2000; Bloom et al. 2002b; Garnavich et al. 2003; Bloom 2004), spectral…”
• The Supernova Gamma-Ray Burst Connection (2006, background): “…with Garnavich et al. (2003b) showing evidence that the brightness and color evolution resembled 1998S (a Type IIn; see also Meurs and Rebelo 2004) and Bloom et al. (2002b) showing consistency with a Ic-like curve interpolated between the faint and fast 1994I and the bright and slow 1998bw.”
• THE HOST GALAXIES OF GAMMA-RAY BURSTS. II. A MASS–METALLICITY RELATION FOR LONG-DURATION GAMMA-RAY BURST HOST GALAXIES (2010, background): “As a result, a number of studies cite these explosive events as potential unbiased tracers of the star formation and metallicity history of the universe at high redshifts (e.g., Bloom et al. 2002, Fynbo et al. 2006a, Chary et al. 2007, Savaglio et al. 2009).”
• Short-Duration Gamma-Ray Bursts (2013, background): “…significance (e.g.,Hjorth et al. 2003, Stanek et al. 2003, Pian et al. 2006, Berger et al. 2011), and on photometric re-brightenings on a timescale of∼ 15− 20 d post-burst that match Type Ic SN light curves in both brightness and color (toz∼ 1; e.g.,Bloom et al. 1999, 2002, Woosley & Bloom 2006).”
• HUBBLE SPACE TELESCOPE OBSERVATIONS OF SHORT GAMMA-RAY BURST HOST GALAXIES: MORPHOLOGIES, OFFSETS, AND LOCAL ENVIRONMENTS (2009, methodology): “Comparison to Long GRB Host Galaxies We compare our observed short GRB offsets with those of long GRBs from the sample of Bloom et al. (2002) in Figures 13-15.”
• The physics of gamma-ray bursts & relativistic jets (2014, background): “This is consistent with the compact star merger scenarios, since compact stars born in asymmetric supernovae most likely received a ‘‘kick’’, so that the binary system drifted away from the star forming regions when mergers occur [804].”