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Host Galaxies of Long GRBs: A Study on Optically Unbiased Hosts with Swift-Detected Afterglows

This study examines the host properties of long-duration gamma-ray bursts (GRBs) detected by Swift, focusing on optically unbiased hosts. The research includes host galaxy identification, selection criteria, redshift distribution, and host properties analysis.

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Host Galaxies of Long GRBs: A Study on Optically Unbiased Hosts with Swift-Detected Afterglows

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  1. Host Galaxies of Long GRBs PalliJakobsson Centre for Astrophysics & Cosmology University of Iceland

  2. LP (Large Programme) sample TOUGH sample The Optically Unbiased GRB Host Jens Hjorth Johan Fynbo Daniele Malesani Bo Milvang-Jensen Nial Tanvir Bob Chapman

  3. GRB Host Galaxies GRB 980425 / SN 1998bw z = 0.0085 Fruchter et al. (2006)

  4. TOUGH sample selection criteria 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: 68 GRBs 80% have an optical/NIR afterglow 57% have a reported redshift (39/68)

  5. Sample selection: sky map Empty circles: without an X-ray afterglow Filled circles: with an X-ray afterglow Crosses: untriggered bursts Green: short bursts

  6. Locating the hosts Optical afterglow images provide accurate astrometry.

  7. Locating the hosts X-ray position is usually good enough.

  8. How many detected? R-band detections: 56/68 = 82% K-band detections: 23/65 = 35%

  9. Host properties -15 > MB > -22 GRB hosts are mostly subluminous In line with previous findings based on smaller and less complete samples

  10. Host properties Blue colours: <R – K> ~ 3 Only 1/56 ERO Red: no OA Tanvir et al. (2008) Jaunsen et al. (2008) Perley et al. (2009) Levesque et al. (2010) Blue: with OA

  11. Redshift determination (R < 25 mag)

  12. Redshift determination (z = 0.84) (z = 0.84)

  13. Redshift distribution Before TOUGH: <z> = 2.39 After TOUGH: <z> = 2.13 10 new redshifts All 68 hosts have a redshift constraint

  14. Redshift distribution

  15. Legacy value

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