GRB 050814 at z = 5.3 and a Mean Redshift of 2.8 for Swift

GRBsA&A, in press (astro-ph/0509888)

Páll JakobssonRobert PriddeyDarach WatsonPriya Natarajan

Andrew LevanJens HjorthBrian L. JensenJavier Gorosabel

Johan P. U. FynboNial TanvirJesper SollermanKristian Pedersen

X2.7

GRB 050814

t90 = 65+40-20 s (poorly constrained).

XRT source @ 138 s.UVOT @ 167 s: V > 20.5 mag.

NOT observations of OA @ 14 hours:V > 25.2 mag; R = 23.4 mag; I = 20.6 mag.

R – I 2.8 mag β 11.7

UKIRT detection in the NIR (J and K).

Spectral Energy Distribution

Spectral Energy Distribution

GRB 050814 (z = 5.3) GRB 050904 (z = 6.3)

Tagliaferri et al. (2005)

Spectral Energy Distribution

2(z) for GRB 050814

z = 5.3 ± 0.3

β = 1.0 (fixed)

AV 0.9 mag

The Redshift Distribution of Swift LGRBs

Is it consistent with models were GRBs trace the global star formation?

Important to construct a “clean” sample as unbiased as possible.

Metallicity dependence?

Selection Criteria

Small error circles: XRT localization (68).

Sufficiently small Galactic extinction:AV < 0.5 mag (46).

Quick distribution of XRT error circles for a relatively rapid follow-up: after 1 March 2005 (39).

Reject bursts with an unsuitable declination:above +70º or below –70º (36).

A total of 83 long-duration Swift GRBs

The Sample (36 bursts)

050315 050318050319050401050406050412050416A050502B050505050525050603050714B

050716050726050730050801050802050803050814050819050820A050822050824050904

050908050915A050922B050922C051001051006051008051012051016A051016B051117A051117B

1.95 1.44 3.24 2.90< 3.5

0.65< 8.5 4.27 0.61 2.82

< 8.0 < 5.0 3.97< 2.0 1.71

5.3

2.61 0.83 6.29

3.34 < 13.0 2.20

0.94

GRB GRB GRBz z z

Cumulative Fraction

Natarajan et al. (2005)Gorosabel et al. (2004)

At least 6% @ z > 5

050315 050318050319050401050406050412050416A050502B050505050525050603050714B

050716050726050730050801050802050803050814050819050820A050822050824050904

050908050915A050922B050922C051001051006051008051012051016A051016B051117A051117B

1.95 1.44 3.24 2.90< 3.5

0.65< 8.5 4.27 0.61 2.82

< 8.0 < 5.0 3.97< 2.0 1.71

5.3

2.61 0.83 6.29

3.34 < 13.0 2.20

0.94

GRB GRB GRBz z z