Probability for chance coincidence of a gamma-ray burst with a galaxy on the sky

The nearby long GRB 060614 was not accompanied by a supernova, challenging the collapsar model for long-duration gamma-ray bursts (GRBs) and the traditional classification scheme for GRBs. However, Cobb et al. have argued that the association of GRB 060614 and its host galaxy could be chance coincidence. In this work, we calculate the probability for a GRB to be randomly coincident with a galaxy on the sky, using a galaxy luminosity function obtained from current galaxy surveys. We find that, with a magnitude limit that current telescopes can reach and an evolving galaxy luminosity function obtained from VIMOS VLT Deep Survey, the probability for chance coincidence of a GRB with a galaxy of redshift <1.5 is about several per cent. These results agree with previous estimates based on the observed galaxies. For the case of GRB 060614, the probability for it to be coincident with a z < 0.125 galaxy by angular separation <0.5 arcsec is ≈0.02 per cent, indicating that the association of GRB 060614 and its host galaxy is secure. If the telescope magnitude limit is significantly improved in future, the probability for GRB-galaxy association will be considerably large, making it very problematic to identify a GRB host based only on the superposition of a GRB and a galaxy on the sky.

[1]  A. S. Fruchter,et al.  Gamma-Ray Burst-Selected High-Redshift Galaxies: Comparison to Field Galaxy Populations to z ~ 3 , 2005, astro-ph/0508197.

[2]  A. MacFadyen,et al.  Collapsars: Gamma-Ray Bursts and Explosions in “Failed Supernovae” , 1998, astro-ph/9810274.

[3]  N. Lund,et al.  The optical afterglow and host galaxy of GRB 000926 , 2001 .

[4]  M. Galassi,et al.  GAMMA-RAY BURSTS: 30 YEARS OF DISCOVERY , 2004 .

[5]  IAA-CSIC,et al.  UV star-formation rates of GRB host galaxies , 2004, astro-ph/0407066.

[6]  P. Schechter.  An analytic expression for the luminosity function for galaxies , 1976 .

[7]  Caltech,et al.  Spectroscopy of the Host Galaxy of the Gamma-Ray Burst 980703 , 1998, astro-ph/9808188.

[8]  A. S. Fruchter,et al.  Late-epoch optical and near-infrared observations of the GRB 000911 afterglow and its host galaxy , 2005, astro-ph/0504592.

[9]  E. O. Ofek,et al.  A novel explosive process is required for the γ-ray burst GRB 060614 , 2006, Nature.

[10]  R. S. Priddey,et al.  A case of mistaken identity? GRB 060912A and the nature of the long–short GRB divide , 2007, 0704.2525.

[11]  et al,et al.  The Luminosity Function of Galaxies from SDSS Commissioning Data , 2000 .

[12]  E. Rol,et al.  The host of GRB 030323 at z=3.372: A very high column density DLA system with a low metallicity , 2004, astro-ph/0403080.

[13]  P. Duc,et al.  Very Large Telescope and Hubble Space Telescope Observations of the Host Galaxy of GRB 990705 , 2002 .

[14]  N. Gehrels,et al.  The Spectral Lag of GRB 060505: A Likely Member of the Long-Duration Class , 2008, 0803.1919.

[15]  Charles D. Bailyn,et al.  Connecting Gamma-Ray Bursts and Galaxies: The Probability of Chance Coincidence , 2007, 0708.1510.

[16]  M. SubbaRao,et al.  The Luminosity Function of Morphologically Classified Galaxies in the Sloan Digital Sky Survey , 2002, astro-ph/0212405.

[17]  R. Nichol,et al.  The Galaxy Luminosity Function and Luminosity Density at Redshift z = 0.1 , 2002, astro-ph/0210215.

[18]  Santiago,et al.  The ESO-Sculptor Survey: Luminosity functions of galaxies per spectral type at redshifts 0.1-0.5 , 2003, astro-ph/0301339.

[19]  J. R. Thorstensen,et al.  GRB 060218/SN 2006aj: A Gamma-Ray Burst and Prompt Supernova at z = 0.0335 , 2006, astro-ph/0603686.

[20]  GRB 050826: A Subluminous Event at z=0.296 Finds Its Place in the Luminosity Distribution of Gamma-Ray Burst Afterglows , 2007, 0704.3069.

[21]  S. B. Pandey,et al.  Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow , 2007, 0704.2235.

[22]  S. E. Woosley,et al.  Supernovae, Jets, and Collapsars , 1999, astro-ph/9910034.

[23]  J. Fynbo,et al.  No supernovae detected in two long-duration gamma-ray bursts , 2007, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[24]  A. Gal-Yam,et al.  Multicolor Observations of the GRB 000926 Afterglow , 2000, astro-ph/0012303.

[25]  Bing Zhang.  Gamma-Ray Bursts in the Swift Era , 2007, astro-ph/0701520.

[26]  E. Berger,et al.  A Morphological Study of Gamma-Ray Burst Host Galaxies , 2005 .

[27]  A. Loeb.  Novel Ways to Probe the Universe with Gamma-Ray Bursts and Quasars , 2001, astro-ph/0108432.

[28]  Alexander Heger,et al.  The Progenitor Stars of Gamma-Ray Bursts , 2005, astro-ph/0508175.

[29]  E. Rol,et al.  A multi-colour study of the dark GRB 000210 host galaxy and its environment , 2002, astro-ph/0212334.

[30]  A. Gal-Yam,et al.  Hubble Space Telescope and Ground-based Optical and Ultraviolet Observations of GRB 010222 , 2003, astro-ph/0301059.

[31]  Li-Xin Li,et al.  Correlation between the peak spectral energy of gamma-ray bursts and the peak luminosity of the underlying supernovae: implication for the nature of the gamma-ray burst–supernova connection , 2006, astro-ph/0608315.

[32]  V. Petrosian,et al.  Surface brightness and evolution of galaxies , 1976 .

[33]  S. Djorgovski,et al.  Submitted to The Astrophysical Journal (Letters) The Host Galaxy of the Gamma–Ray Burst 971214 1 , 1998 .

[34]  Bing Zhang,et al.  Astrophysics: A burst of new ideas , 2006, Nature.

[35]  P. Natarajan,et al.  Could GRB 060614 and Its Presumed Host Galaxy Be a Chance Superposition? , 2006, astro-ph/0608678.

[36]  Jesper Sollerman,et al.  No supernovae associated with two long-duration γ-ray bursts , 2006, Nature.

[37]  A. Levan,et al.  The population of GRB hosts , 2007, 0709.0861.

[38]  A. J. Levan,et al.  Long γ-ray bursts and core-collapse supernovae have different environments , 2006, Nature.

[39]  S. R. Kulkarni,et al.  The Redshift Determination of GRB 990506 and GRB 000418 with the Echellete Spectrograph Imager on Keck , 2002, astro-ph/0212123.

[40]  S. Noll,et al.  The evolution of the luminosity functions in the FORS deep field from low to high redshift. II. The red bands , 2004 .

[41]  T. Sakamoto,et al.  A new γ-ray burst classification scheme from GRB 060614 , 2006, Nature.

[42]  The 2dF Galaxy Redshift Survey: galaxy luminosity functions per spectral type , 2001, astro-ph/0107197.

[43]  M. Gilfanov,et al.  Lighthouses of the universe : the most luminous celestial objects and their use for cosmology : proceedings of the MPA/ESO/MPE/USM Joint Astronomy Conference held in Garching, Germany, 6-10 August 2001 , 2002 .

[44]  D. Madgwick,et al.  The 2dF Galaxy Redshift Survey: The bJ-band galaxy luminosity function and survey selection function , 2001, astro-ph/0111011.

[45]  S. R. Kulkarni,et al.  The Observed Offset Distribution of Gamma-Ray Bursts from Their Host Galaxies: A Robust Clue to the Nature of the Progenitors , 2000, astro-ph/0010176.

[46]  D. Frail,et al.  The Radio Afterglow and Host Galaxy of the Dark GRB 020819 , 2005, astro-ph/0505035.

[47]  Jesper Sollerman,et al.  SPATIALLY RESOLVED PROPERTIES OF THE GRB 060505 HOST: IMPLICATIONS FOR THE NATURE OF THE PROGENITOR , 2008 .

[48]  N. R. Tanvir,et al.  Discovery of the Near-IR Afterglow and of the Host of GRB 030528 , 2004 .

[49]  S. J. Lilly,et al.  The Canada-France Redshift Survey. VI. Evolution of the Galaxy Luminosity Function to Z approximately 1 , 1995 .

[50]  M. Feroci,et al.  The Host Galaxy of GRB 990123 , 1999 .

[51]  D. Fugazza,et al.  An enigmatic long-lasting γ-ray burst not accompanied by a bright supernova , 2006, Nature.

[52]  S. R. Kulkarni,et al.  Submitted to The Astrophysical Journal Preprint typeset using L ATEX style emulateapj v. 04/03/99 THE REDSHIFT AND THE ORDINARY HOST GALAXY OF GRB 970228 1 , 1997 .

[53]  E. Ramirez-Ruiz,et al.  Gamma-Ray Bursts in the Swift Era , 2009, 0909.1531.

[54]  S. Noll,et al.  The evolution of the luminosity functions in the FORS Deep Field from low to high redshift: I. The blue bands , 2004, astro-ph/0403535.

[55]  E. al.,et al.  The Sloan Digital Sky Survey: Technical summary , 2000, astro-ph/0006396.

[56]  et al,et al.  Discovery of the optical counterpart and early optical observations of GRB 990712 , 2000 .

[57]  I. M. H. Etherington.  LX. On the definition of distance in general relativity , 1933 .

[58]  Bing Zhang,et al.  Making a Short Gamma-Ray Burst from a Long one: Implications for the Nature of GRB 060614 , 2007 .

[59]  Takashi Ichikawa,et al.  GALAXY COLORS IN VARIOUS PHOTOMETRIC BAND SYSTEMS , 1995 .

[60]  D. Frail,et al.  The radio afterglow from the γ-ray burst of 8 May 1997 , 1997, Nature.

[61]  Li-Xin Li,et al.  Transient Events from Neutron Star Mergers , 1998 .

[62]  Melvyn B. Davies,et al.  A new type of long gamma-ray burst , 2007 .

[63]  A. Mazure,et al.  The VIMOS VLT deep survey , 2008, 0903.0271.

[64]  E. O. Ofek,et al.  GRB 060505: A Possible Short-Duration Gamma-Ray Burst in a Star-forming Region at a Redshift of 0.09 , 2007 .

[65]  NOAO,et al.  Evolution of the Luminosity Function, Star Formation Rate, Morphology, and Size of Star-forming Galaxies Selected at Rest-Frame 1500 and 2800 Å , 2006, astro-ph/0609016.

[66]  Richard G. McMahon,et al.  The Afterglow and Complex Environment of the Optically Dim Burst GRB 980613 , 2002, astro-ph/0205126.

[67]  S. Djorgovski,et al.  The Host Galaxy of GRB 970508 , 1998, astro-ph/9807315.

[68]  W. Freedman,et al.  The First Detections of the Extragalactic Background Light at 3000, 5500, and 8000 Å. I. Results , 2001, astro-ph/0112153.

[69]  J. P. U. Fynbo,et al.  The line-of-sight towards GRB 030429 at z =2.66: Probing the matter at stellar, galactic and intergalactic scales , 2004, astro-ph/0407439.

[70]  George R. Ricker,et al.  GRB 010921: Discovery of the First High Energy Transient Explorer Afterglow , 2002 .

[71]  The Optical Afterglows of Gamma-Ray Bursts , 2002, astro-ph/0211405.

[72]  L. Kewley,et al.  The Host Galaxy of GRB 060505: Host ISM Properties , 2007, 0708.0833.