The Optically Unbiased GRB Host (TOUGH) sample

The Optically Unbiased GRB Host (TOUGH) sample

Palli JakobssonCentre for Astrophysics & Cosmology

University of Iceland

TOUGH 1: Survey Design and Catalogues (Hjorth et al.)

TOUGH 2: Fundamental Properties (Malesani et al.)

TOUGH 3: Redshift Distribution (Jakobsson et al.)

TOUGH 4: Lyα Emitters (Milvang-Jensen et al.)

TOUGH 5: Radio Survey at z < 1 (Michałowski et al.)

TOUGH 6: Host Luminosity Function (Schulze et al.)

Jens Hjorth (PI)Jóhán Fýnbó(Icelandic expert)

Bo Milvang-Jensen(Eurovision expert)

Daniele Malesani(GCN expert)

Bob Chapman(Dr. Who expert)

Nial Tanvir(world record expert)

The TOUGH Guys

Thomas Krühler(X-shooter expert)

69 Host Galaxies (R-band)

Redshift DistributionBefore TOUGH:

<z> = 2.39

Redshift DistributionBefore TOUGH:

<z> = 2.39

TOUGH (FORS):

<z> = 2.23

Redshift Distribution

TOUGH (FORS):

<z> = 2.23

Before TOUGH:<z> = 2.3915 new

redshifts

68/69 hosts have a redshift

constraint

TOUGH (X-shooter):<z> = 2.23

77% (53/69) redshift

completion

1. A Swift-detected GRB with t90 > 2 s.

2. XRT afterglow position distributed within 12 hours.

3. Small foreground Galactic extinction: AV < 0.5 mag.

4. Favorable declination: -70° < δ < 27°.

5. Afterglow error radius < 2”.

March 2005 – August 2007: 69 GRBs

75% had an optical/NIR afterglow

TOUGH Sample Selection Criteria

55% had a reported redshift (38/69)

Blue: short bursts

Empty circles: withoutan X-ray afterglow

Filled circles: withan X-ray afterglow

Crosses: untriggered bursts

Sample Selection: Sky Map

R-band detections:53/69 = 77%

K-band detections:24/60 = 40%

How Many Hosts Detected (R-band)?

-15 > MB > -22

GRB hosts aremostly subluminous

In line with previousfindings based onsmaller and less

complete samples

Host Properties

Blue colours:<R – K> ~ 3

Blue: with OA

Red: no OA

Only 1/56 ERO

Host Properties

Tanvir et al. (2008)Jaunsen et al. (2008)Perley et al. (2009)

Levesque et al. (2010)Krühler et al. (2011)

Redshift Determination (R < 25 mag)

Redshift Determination(z = 0.84) (z =

1.92)

(z = 0.84)

Cumulative Redshift Distribution

KS: < 1%KS: 52%

SFR1(Li 2008 modified by

Langer & Norman 2006low-metallicity

correction)

SFR2(Model A from Schmidt 2009)

SFR Density Histories

Lyα and the Role of Dust