1. The Host Galaxies of
High-Redshift GRBs
Edo Berger
Harvard University

2. Outline 1. GRBs at z<1: Is there a low-metallicity bias?
2. The ISM of high-redshift galaxies
3. DLA counterparts & the M-Z relation at z>2
Spitzer stack

3. Long GRBs Hosts: Metallicity?
redshift
mass
Levesque, Berger, & Kewley 2009,2010
Low-Z “preference” at z<1; essentially disappears by z~2
Wainwright, EB & Penprase 2007, ApJ

4. GRB Absorption Spectroscopy
QSOs act as background sources of illumination; GRBs are embedded within their host galaxies
40 kpc

5. 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

6. GRB Absorption Spectroscopy
Intrinsic
Ly series absorption
Lyα forest
Metals
log NH =22.1±0.1
[S/H] = 0.06 Z⦿
Berger et al. 2006

7. GRB-DLAs 〈ZGRB〉~ 3 x〈ZQSO〉 〈N(HI)GRB〉~ 10 x〈N(HI)QSO〉 MW GMCs
Berger et al. 2006; Prochaska et al. 2007; Savaglio et al. 2007
Berger et al. 2006; Fynbo et al. 2009
〈N(HI)GRB〉~ 10 x〈N(HI)QSO〉
Complication for reionization? Avi’s question

8. QSO-DLA Counterparts HST/NICMOS: H=22 mag; 1/22 detected
Warren et al. 2001
HST/NICMOS: H=23 mag; confused
Colbert & Malkan 2002

9. GRB-DLA Counterparts 1. GRBs have <1″ offset:
No ambiguity about the identity of the DLA counterpart
2. GRBs fade away:
Counterpart can be imaged to L≪ L* regardless of PSF

10. GRB-DLA Counterparts HST/ACS z = 3.372 F606W(AB) = 28.1 mag
1″=1.75 kpc
z = 3.372
Vreeswijk et al. 2004
Wainwright, Berger, & Penprase 2007
F606W(AB) = mag
L ≈ 0.02 L*
SFR ≈ 1 M⊙/yr

11. GRB-DLA Counterparts GRB 050904: z = 6.295 L < L* SFR < 6 M⊙/yr
M < 109 M⊙
Berger et al. 2007

12. GRB-DLA Counterparts Spitzer/IRAC: z ~ 2 - 3 Spitzer/IRAC: z ~ 3 - 5
Chary, Berger, & Cowie 2007
Laskar, Berger, & Chary 2010

13. GRB-DLA Counterparts
GOODS
z~1 GRBs
Chary, Berger, & Cowie 2007

14. The M-Z & L-Z Relations at z > 2
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

15. The Host of z=8.2
Detection at 3.6 m 46 days after the burst (5 days in the rest-frame):
72 hr exposure: AB mag = 48 nJy
2nd epoch in 2/2010 to detect the underlying host galaxy, and …
No Detection: L < 0.1 L*
Chary, Berger, et al. 2009

16. Obscured Star Formation?
ALMA/EVLA: detections to z~4-6; e.g. correlation of CO & Z
z~1-2:
SFR ~ 100−300 M⊙/yr
LFIR ~ 1012 L⊙

17. 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 > 2, as well as a mass function of DLAs