The Host Galaxies of
High-Redshift GRBs
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
metallicity
Long GRBs Hosts: Metallicity?
redshift
Levesque, Berger, & Kewley
2009,2010
mass
Low-Z “preference” at z<1; essentially disappears by z~2
GRB Absorption Spectroscopy
QSOs act as
background sources of
illumination; GRBs are
embedded within their
host galaxies
40 kpc
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
40 kpc
- High(er) redshift
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
GRB-DLAs
〈ZGRB〉~ 3 x〈ZQSO〉
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
QSO-DLA Counterparts
DLA?
HST/NICMOS: H=22 mag; 1/22
detected
HST/NICMOS: H=23 mag;
QSO
confused
Colbert & Malkan 2002
Warren et al. 2001
GRB-DLA Counterparts
1. GRBs have <1″ offset:
2. GRBs fade away:
No ambiguity about the
identity of the DLA
counterpart
Counterpart can be
imaged to L≪ L*
regardless of PSF
GRB-DLA Counterparts
HST/ACS
1″=1.75 kpc
z = 3.372
Vreeswijk et al. 2004
• F606W(AB) = 28.1
mag
• L ≈ 0.02 L*
• SFR ≈ 1 M /yr
Wainwright, Berger, & Penprase 20
GRB-DLA Counterparts
GRB 050904:
z = 6.295
L < L*
SFR < 6
M⊙/yr
M < 109 M⊙
Berger et al. 2007
GRB-DLA Counterparts
Spitzer/IRAC: z ~ 2 - 3
Chary, Berger, & Cowie
2007 Berger, & Chary
Laskar,
2010
Spitzer/IRAC:
z~3-5
GRB-DLA Counterparts
GOOD
S
z~1
GRBs
Chary, Berger, & Cowie 2007
The M-Z & L-Z Relations at z > 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
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 …
No Detection: L < 0.1 L*
Chary, Berger, et al. 2009
Obscured Star Formation?
z~1-2:
SFR ~ 100−300 M⊙/yr
LFIR ~ 1012 L⊙
ALMA/EVLA: detections to z~4-6; e.g. correlation of CO & Z
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 MZ and L-Z relations at z > 2, as well as a mass function
of DLAs