The Afterglows and Redshifts of Swift GRBs

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The Host Galaxies of High-Redshift GRBs
Edo Berger Harvard University
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Outline
1. GRBs at zlt1 Is there a low-metallicity bias?
2. The ISM of high-redshift galaxies
3. DLA counterparts the M-Z relation at zgt2
Spitzer stack
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Long GRBs Hosts Metallicity?
metallicity
redshift
mass
Levesque, Berger, Kewley 2009,2010
Low-Z preference at zlt1 essentially disappears
by z2
Wainwright, EB Penprase 2007, ApJ
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GRB Absorption Spectroscopy
QSOs act as background sources of illumination
GRBs are embedded within their host galaxies
40 kpc
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GRB Absorption Spectroscopy
QSOs act as background sources of illumination
GRBs are embedded within their host galaxies

• GRBs vs. quasars
• Small impact parameter
• No Mpc proximity effect
• In star forming regions
• High(er) redshift
• Power law spectrum
• Fade away

40 kpc
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GRB Absorption Spectroscopy
Intrinsic
Ly series absorption
Lya forest
Metals
log NH 22.10.1 S/H 0.06 Z?
Berger et al. 2006
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GRB-DLAs
ltZGRBgt 3 xltZQSOgt
MW GMCs
Berger et al. 2006 Prochaska et al. 2007
Savaglio et al. 2007
Berger et al. 2006 Fynbo et al. 2009
ltN(HI)GRBgt 10 xltN(HI)QSOgt Complication for
reionization? Avis question
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QSO-DLA Counterparts
DLA?
HST/NICMOS H22 mag 1/22 detected
QSO
Colbert Malkan 2002
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GRB-DLA Counterparts
1. GRBs have lt1? offset No ambiguity about the
identity of the DLA counterpart
2. GRBs fade away Counterpart can be imaged to
L L regardless of PSF
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GRB-DLA Counterparts
HST/ACS
1?1.75 kpc
Vreeswijk et al. 2004
Wainwright, Berger, Penprase 2007
z 3.372

• F606W(AB) 28.1 mag
• L 0.02 L
• SFR 1 M?/yr

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GRB-DLA Counterparts
GRB 050904 z 6.295 L lt L SFR lt 6 M?/yr M lt
109 M?
Berger et al. 2007
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GRB-DLA Counterparts
Spitzer/IRAC z 2 - 3
Spitzer/IRAC z 3 - 5
Chary, Berger, Cowie 2007
Laskar, Berger, Chary 2010
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GRB-DLA Counterparts
GOODS
z1 GRBs
Chary, Berger, Cowie 2007
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The M-Z L-Z Relations at z gt 2
z 4
z 4
Chary, Berger, Cowie 2007
z 0 Tremonti et al. 2004 z 1 Kobulnicky
Kewley 2004 Savaglio et al. 2005 z 2 Erb
et al. 2006
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The Host of GRB090423 _at_ z8.2
Detection at 3.6 ?m 46 days after the burst (5
days in the rest-frame) 72 hr exposure 27.2
AB mag 48 nJy 2nd epoch in 2/2010 to detect
the underlying host galaxy, and
No Detection L lt 0.1 L
Chary, Berger, et al. 2009
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Obscured Star Formation?
z1-2 SFR 100-300 M?/yr LFIR 1012 L?
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Conclusions

• GRBs are a powerful probe of the ISM of high-z
  galaxies, at redshifts that cannot be currently
  probed by direct spectroscopic observations
• The environments probed by GRBs have higher
  neutral hydrogen and metal columns than those
  probed by quasars probes of star forming regions
• Host galaxy observations will soon provide the
  first M-Z and L-Z relations at z gt 2, as well as
  a mass function of DLAs