The Host Galaxies of High-Redshift GRBs

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

Berger et al. 2007

GRB 050904:

z = 6.295

L < L*

SFR < 6 M⊙/yr

M < 109 M⊙

GRB-DLA Counterparts

Spitzer/IRAC: z ~ 2 - 3

Chary, Berger, & Cowie 2007

Spitzer/IRAC:z ~ 3 - 5 Laskar, Berger, &

Chary 2010

GRB-DLA Counterparts

Chary, Berger, & Cowie 2007

GOODS

z~1 GRBs

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