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SFRs and stellar masses in long duration GRB host galaxies with z ~ 1

SFRs and stellar masses in long duration GRB host galaxies with z ~ 1

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SFRs and stellar masses in long duration GRB host galaxies with z ~ 1

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  1. SFRs and stellar masses inlong duration GRB host galaxies with z ~ 1 José María Castro Cerón Michał Jerzy Michałowski Jens Hjorth Darach Watson Johan Peter Uldall Fynbo Javier Gorosabel www.dark-cosmology.dk Niels Bohr Instituttet l Københavns Universitet

  2. José María Castro Cerón • Outline • introduction. • sample + motivations. • SED fitting. • SFRs. • M*. • comparison with other galaxy samples: specific SFRs. • summary. Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  3. José María Castro Cerón • GRB host galaxies • they may help our understanding of massive SF, as well as give clues to the nature of the progenitors. They tend to be: • blue (Chary et al. 2002). • subluminous (Le Floc’h et al. 2003). • young (Christensen et al. 2004). • once thought to be ULIRGs, SCUBA proved otherwise (Tanvir et al. 2004). Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  4. José María Castro Cerón • Our sample of GRB hosts • GRB 970508 • GRB 970828 • GRB 980613 • GRB 980703 • GRB 981226 • GRB 990705 Motivation • to examine a sample of hosts at z ~ 1, which has been suggested to be close to the peak of the global SFR (Madau et al. 1998). • at z = 1, the observed 4,5 µm band is approximately equivalent to the rest frame K band, which traces the accumulation of M* (Glazebrook et al. 2004). Photometric data • IRAC 4,5 µm and 8,0 µm; MIPS 24 µm. • SCUBA (our reduction). • other (optical to radio) from the litarature. z = 0,83 – 1,11 R = 22,5 – 24,5 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  5. José María Castro Cerón • Spitzer Space Telescope (Werner et al. 2004) • mirror Ø = 85 cm. • 3 cryogenically cooled instruments. • broadband photometry. • low/moderate resolution spectroscopy. •  = 3 µm – 180 µm. • estimated mission life = 2009. Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  6. José María Castro Cerón Castro Cerón et al. 2006 • SED fits • fitted observational templates: • Arp 220: archetypal ULIRG. • NGC 6946: blue, star forming. • (both Silva et al. 1998) • Dale et al. 2001. • Dale & Helou 2002. • scaled the template to match data. • ------- inconclusive • ......... ruled out • (plotted  highest/lowest SFRs) • _____ fitted Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  7. José María Castro Cerón Castro Cerón et al. 2006 • SFR calculation • integrated from 8 µm to 1.000 µm. • flux density  luminosity density. • (Hogg et al. 2002) • . • then applied Kennicutt 1998. • most accurate/robust host SFRs. • GRB 970508 0,4—26 M yr-1 • GRB 970828 30 ± 8 M yr-1 • GRB 980613 428 ± 51 M yr-1 • GRB 980703 3,8—226 M yr-1 • GRB 981226 1,0—84 M yr-1 • GRB 990705 4,5—173 M yr-1 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  8. José María Castro Cerón Castro Cerón et al. 2006 • M* calculation • M*/LK~ const. respect to prior SFH. • (Glazebrook et al. 2004) • M*/LKdepends on M*. • (Labbé et al. 2005) • hosts = blue, faint, young. • M*/LK~ 0,1  robust lower limit. • for the first time an accurate M*. • GRB 970508 1,5  109M • GRB 970828 2,5  109M • GRB 980613 31  109M • GRB 980703 7,2  109M • GRB 981226 3,9  109M • GRB 990705 9,2  109M Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  9. José María Castro Cerón Castro Cerón et al. 2006 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007

  10. José María Castro Cerón • Summary & Outlook • we have studied IR data from Spitzer observations of GRB host galaxies: • sample of six with z ~ 1. • attempted to fit observational templates to host SEDs: • a significant fraction of our sample could not be fitted. • we require more sophisticated models  synthetic templates. • calculated most accurate/robust SFRs in a sample of GRB hosts to date. • calculated for the first time an accurate value for the M* in those hosts. • compared with other representative types of galaxies: • GRB hosts among those with highest . • a realistic  could not have been derived without Spitzer. • enlarge sample. • full synthesis population. • study redshift dependency. Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007