A COMPLETE SAMPLE OF BRIGHT SWIFT LONG GAMMA-RAY BURSTS. I. SAMPLE PRESENTATION, LUMINOSITY FUNCTION AND EVOLUTION

Journal Article · Tue Apr 10 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/749/1/68· OSTI ID:22020470

Salvaterra, R ^[1]; Campana, S; Vergani, S D; Covino, S; D'Avanzo, P; Fugazza, D; Ghirlanda, G; Ghisellini, G; Melandri, A; Sbarufatti, B; Tagliaferri, G ^[2]; Nava, L ^[3]; Flores, H ^[4]; Piranomonte, S ^[5]

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1. INAF, IASF Milano, via E. Bassini 15, I-20133 Milano (Italy)
2. INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Saint Lucia) (Italy)
3. SISSA, via Bonomea 265, I-34136 Trieste (Italy)
4. Laboratoire GEPI, Observatoire de Paris, CNRS-UMR8111, Univ. Paris-Diderot 5 place Jules Janssen, 92195 Meudon (France)
5. INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Rome (Italy)

We present a carefully selected sub-sample of Swift long gamma-ray bursts (GRBs) that is complete in redshift. The sample is constructed by considering only bursts with favorable observing conditions for ground-based follow-up searches, which are bright in the 15-150 keV Swift/BAT band, i.e., with 1-s peak photon fluxes in excess to 2.6 photons s{sup -1} cm{sup -2}. The sample is composed of 58 bursts, 52 of them with redshift for a completeness level of 90%, while another two have a redshift constraint, reaching a completeness level of 95%. For only three bursts we have no constraint on the redshift. The high level of redshift completeness allows us for the first time to constrain the GRB luminosity function and its evolution with cosmic times in an unbiased way. We find that strong evolution in luminosity ({delta}{sub l} = 2.3 {+-} 0.6) or in density ({delta}{sub d} = 1.7 {+-} 0.5) is required in order to account for the observations. The derived redshift distributions in the two scenarios are consistent with each other, in spite of their different intrinsic redshift distributions. This calls for other indicators to distinguish among different evolution models. Complete samples are at the base of any population studies. In future works we will use this unique sample of Swift bright GRBs to study the properties of the population of long GRBs.

• OSTI ID: 22020470
• Journal Information: Astrophysical Journal, Vol. 749, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COSMIC GAMMA BURSTS
COSMOLOGY
LUMINOSITY
PHOTONS
RED SHIFT
STAR EVOLUTION
STARS