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2. The ISM of high-redshift galaxies
3. DLA counterparts & the M-Z relation at z>2
1. GRBs at z<1: Is there a low-metallicity bias?
Outline
Spitzer stack
Levesque, Berger, & Kewley 2009,2010
Long GRBs Hosts: Metallicity?
me
talli
city
redshift mass
Low-Z “preference” at z<1; essentially disappears by z~2
QSOs act as background sources of illumination; GRBs are embedded within
their host galaxies
GRB Absorption Spectroscopy
40 kpc
QSOs act as background sources of illumination; GRBs are embedded within
their host galaxies
GRB Absorption Spectroscopy
40 kpc
GRBs vs. quasars:
- Small impact parameter
- No Mpc proximity effect
- In star forming regions
- High(er) redshift
- Power law spectrum
- Fade away
Berger et al. 2006
log NH =22.1±0.1
[S/H] = 0.06 Z⦿
Intrinsic
Ly series absorpti
onLyα
forestMetal
s
GRB Absorption Spectroscopy
Berger et al. 2006; Prochaska et al. 2007; Savaglio et al.
2007
〈 N(HI)GRB 〉 ~ 10 x 〈 N(HI)QSO 〉
Complication for reionization? Avi’s question
Berger et al. 2006; Fynbo et al. 2009
GRB-DLAs
〈 ZGRB 〉 ~ 3 x 〈 ZQSO 〉MW GMCs
QSO-DLA CounterpartsDLA?
QSO
Colbert & Malkan 2002
HST/NICMOS: H=22 mag; 1/22 detected
Warren et al. 2001
HST/NICMOS: H=23 mag; confused
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
GRB-DLA Counterparts
• F606W(AB) = 28.1 mag• L ≈ 0.02 L*
• SFR ≈ 1 M⊙/yr
z = 3.372Vreeswijk et al. 2004
1″=1.75 kpc
HST/ACS
Wainwright, Berger, & Penprase 2007
GRB-DLA Counterparts
Spitzer/IRAC: z ~ 2 - 3
Chary, Berger, & Cowie 2007
Spitzer/IRAC:z ~ 3 - 5 Laskar, Berger, &
Chary 2010
The M-Z & L-Z Relations at z > 2
Chary, Berger, & Cowie 2007z ~ 0: Tremonti et al. 2004 z ~ 1: Kobulnicky & Kewley 2004; Savaglio et al. 2005 z ~ 2: Erb et al. 2006
z ~ 4 z ~ 4
The Host of GRB090423 @ z=8.2
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 …
Chary, Berger, et al. 2009
No Detection: L < 0.1 L*
Obscured Star Formation?
z~1-2:
SFR ~ 100−300 M⊙/yrLFIR ~ 1012 L⊙
ALMA/EVLA: detections to z~4-6; e.g. correlation of CO & Z
•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
Conclusions