SFRs and stellar masses in long duration GRB host galaxies with z ~ 1 José María Castro Cerón Michał Jerzy Michałowski Jens Hjorth Darach Watson Johan Peter Uldall Fynbo Javier Gorosabel Niels Bohr Instituttet l Københavns Universitet

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

3 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007 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). José María Castro Cerón

4 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007 Our sample of GRB hosts GRB GRB GRB GRB GRB GRB 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 José María Castro Cerón

5 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007 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 = José María Castro Cerón

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

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

8 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007 M * calculation M * /L K ~ const. respect to prior SFH. (Glazebrook et al. 2004) M * /L K depends on M *. (Labbé et al. 2005) hosts = blue, faint, young. M * /L K ~ 0,1  robust lower limit. for the first time an accurate M *. GRB ,5  10 9 M  GRB ,5  10 9 M  GRB  10 9 M  GRB ,2  10 9 M  GRB ,9  10 9 M  GRB ,2  10 9 M  José María Castro Cerón Castro Cerón et al. 2006

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

10 Dansk Fysik Selskab | Årsmøde 2007 Nyborg, 19–20 Juni 2007 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. José María Castro Cerón