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Studying GRB Environments and Progenitors with Absorption Spectroscopy

Studying GRB Environments and Progenitors with Absorption Spectroscopy. Derek B. Fox Astronomy & Astrophysics Penn State University. Image: Aurore Simonnet, Sonoma State. Group Papers.

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Studying GRB Environments and Progenitors with Absorption Spectroscopy

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  1. Studying GRB Environments and Progenitors with Absorption Spectroscopy Derek B. Fox Astronomy & Astrophysics Penn State University Image: Aurore Simonnet, Sonoma State

  2. Group Papers • Spectroscopy of GRB 050505 at z=4.275: A log N(HI)=22.1 DLA Host Galaxy and the Nature of the Progenitor. Berger et al. 2006a, ApJ submitted, astro-ph/0511498. • Fine-Structure FeII and SiII Absorption in the Spectrum of GRB 051111: Implications for the Burst Environment.Berger et al. 2006b, ApJL submitted, astro-ph/0512280. • Spectroscopy of GRB 051111 at z=1.54948: Kinematics and Elemental Abundances of the GRB Environment and Host Galaxy.Penprase et al. 2006, ApJ in press, astro-ph/0512340. • HST and Spitzer Observations of the Host Galaxy of GRB 050904: A Metal-Enriched Dusty Starburst at z=6.295.Berger et al. 2006c, ApJ submitted, astro-ph/0603689. • An Energetic Afterglow from a Distant Stellar Explosion.Frail et al. 2006, ApJ submitted, astro-ph/0604580.

  3. Group Members • Edo Berger, Mike Gladders & Pat McCarthy (Carnegie) • Bryan Penprase (Pomona) • Dale Frail (NRAO) • Shri Kulkarni, S. Brad Cenko, Alicia Soderberg, Ehud Nakar,Eran Ofek, Avishay Gal-Yam, Mansi Kasliwal, P. Brian Cameron, Chuck Steidel, Naveen Reddy & S. George Djorgovski (Caltech) • Paul Price & Len Cowie (IfA Hawaii) • Brian Schmidt &Bruce Peterson (MSO/ANU) • Derek Fox (Penn State) • Ranga-Ram Chary (Spitzer) • Amy Barger (Wisconsin) • Grant Hill, Barbara Schaefer & Marilyn Reed (Keck)

  4. Long GRBs as Massive Stars • GRB-Supernova = “Gamma-Ray Bright Supernova” • SN Ic – No Hydrogen – Wolf-Rayet progenitor • What makes a star go GRB? (What makes a star go SN?) • Massive Stellar Autopsy: • Redshift • Energetics • Circumburst material • Nickel mass (low-z) • Multimessenger astronomy (very low-z) • Rare population = Biases likely (low-Z? binaries?) Stanek et al. 2003

  5. GRB Afterglow Spectroscopy • Uniquely bright sources at cosmological distances • Illuminate immediate burst surroundings • W-R Winds • Mass ejection events • Occur in the midst of a host galaxy • Host observed as DLA • Rich array of metal lines • What are the conditions of massive star formation at z>1? • At z>4? • At z>6?

  6. GRB Afterglow Spectroscopy • Uniquely bright sources at cosmological distances • Illuminate immediate burst surroundings • W-R Winds • Mass ejection events • Occur in the midst of a host galaxy • Host observed as DLA • Rich array of metal lines • What are the conditions of massive star formation at z>1? • At z>4? • At z>6? 56% complete Jakobsson/Swift sample

  7. A High-Velocity Wind Around a Massive Star at z=4.27 • Spectroscopy of GRB 050505 at z=4.275: A log N(HI)=22.1 DLA Host Galaxy and the Nature of the Progenitor. Berger et al. 2006a, ApJ submitted, astro-ph/0511498.

  8. GRB 050505 Berger et al. 2006a

  9. Berger et al. 2006a

  10. Berger et al. 2006a

  11. Nature of the Absorbers • Highest-column DLA known • Composite curve of growth indicates small velocity spread, ~100 km s–1 • Dust depletion analysis disfavors cold disk • Si II* detection implies high density material, nH > 102 cm–3 • 1000 km s–1 velocity spread for C IV but not Si IV • Either a local or galaxy-scale wind Berger et al. 2006a

  12. Nature of the Absorbers • Highest-column DLA known • Composite curve of growth indicates small velocity spread, ~100 km s–1 • Dust depletion analysis disfavors cold disk • Si II* detection implies high density material, nH > 102 cm–3 • 1000 km s–1 velocity spread for C IV but not Si IV • Either a local or galaxy-scale wind Berger et al. 2006a

  13. Nature of the Wind • Reminiscent of multiple C IV systems to –3000 km s–1 in GRB 021004 (resolved) • GRB 021004 structure identified in H I, other less-ionized species • Led to clumpy wind models • Implies an enrichment of [C/Si] in the progenitor stellar wind for GRB 050505 • Winds from LBGs can reach 1000 km s–1, however… Berger et al. 2006a

  14. GRB Hosts v. QSO DLAs • GRB hosts extend to higher HI column densities • Metallicities higher for a given redshift • Si II* never seen in line-of-sight DLAs • Implies small cross-section for Si II* systems • Consistent with high inferred densities, nH >~ 102 cm–3 Berger et al. 2006a

  15. Berger et al. 2006a

  16. Dense Excited Gas Near a Massive Star at z=1.55 • Fine-Structure Fe II and Si II Absorption in the Spectrum of GRB 051111: Implications for the Burst Environment.Berger et al. 2006b, ApJL submitted, astro-ph/0512280. • Spectroscopy of GRB 051111 at z=1.54948: Kinematics and Elemental Abundances of the GRB Environment and Host Galaxy.Penprase et al. 2006, ApJ in press, astro-ph/0512340. And see also: • Dissecting the Circumstellar Environment of GRB Progenitors. Prochaska, Chen & Bloom 2006, ApJ submitted, astro-ph/0601057

  17. Penprase et al. 2006

  18. Penprase et al. 2006

  19. Penprase et al. 2006

  20. Penprase et al. 2006

  21. Penprase et al. 2006

  22. Nature of the Absorbers • Log N(HI) ~ 21.9 via Zn II • Velocity spread ~10 km s–1 from curve of growth • Dust depletion analysis favors warm disk • Excited states to Fe II****, Si II* from high-density material on line of sight • What is the source of this excitation? Penprase et al. 2006

  23. Nature of the Absorbers • Log N(HI) ~ 21.9 via Zn II • Velocity spread ~10 km s–1 from curve of growth • Dust depletion analysis favors warm disk • Excited states to Fe II****, Si II* from high-density material on line of sight • What is the source of this excitation? Penprase et al. 2006

  24. Nature of the Excitation • Collisional excitation could explain FeII* states alone, but inconsistent with Si II* • Radiative excitation is thus preferred • If it is the GRB/afterglow, time-dependent absorption features are expected • Otherwise the IR radiation field with F ~ 2.2might be supplied by a nearby supercluster Berger et al. 2006b

  25. The Environment and Host Galaxy of a Massive Star at z=6.3 • HST and Spitzer Observations of the Host Galaxy of GRB 050904: A Metal-Enriched Dusty Starburst at z=6.295.Berger et al. 2006c, ApJ submitted, astro-ph/0603689. • An Energetic Afterglow from a Distant Stellar Explosion.Frail et al. 2006, ApJ submitted, astro-ph/0604580. Along with: • Implications for the Cosmic Reionization from the Optical Afterglow Spectrum of the Gamma-Ray Burst 050904 at z=6.3. Totani et al. 2006, PASJ submitted, astro-ph/0512154

  26. GRB 050904 • Swift XRT position (6 arcsec) • Deep optical limits from P60 • Bright NIR afterglow with SOAR: z > 6 (Haislip et al. 2006) • Detection with a 0.5-m optical telescope… (TAROT; Gendre et al. 2006) • Subaru redshift, z=6.3 (Kawai et al. 2006; Totani et al. 2006) • DLA prevents strong constraints on HI in the IGM • Host metallicity ~ 5% solar Haislip et al. 2006

  27. Haislip et al. 2006

  28. log NHI=21.6 Totani et al. 2006

  29. Berger et al. 2006c

  30. Berger et al. 2006c

  31. Berger et al. 2006c

  32. Nature of the Host Galaxy • Metallicity of ~5% solar (Kawai et al. 2006) • MUV ~ –21.7 mag • L ~ L* for this redshift • SFR ~ 15 M yr–1 • Extension of the mass-metallicity relationship to z=6.3 • Galaxy metallicities continue to decrease with redshift… Berger et al. 2006c

  33. Frail et al. 2006

  34. Nature of the Environment • Extremely energetic burst: E ~ 1052 ergs, including jet correction • Roughly x30 greater energy than z~1 GRBs • Density n ~ 700 cm–3 • Roughly x100 greater density than z~1 GRBs • Consistent with density of the Si II* absorber (Kawai et al. 2006) Frail et al. 2006

  35. Conclusions Image: Aurore Simonnet, Sonoma State

  36. GRB Afterglow Spectroscopy • GRBs are a merciless probe of their surroundings • Host is usually a DLA • Velocity broadening mild in most species • Metal abundances >~typical for GRB redshift • Host DLA + metals complicate z>6 IGM studies (Totani et al. 2006) • Unusual features: • High-velocity absorption systems • Excited states of Si, Fe

  37. GRB Afterglow Spectroscopy High-Velocity Absorption: • Stellar wind is the readiest source of v ~ 1000 km s–1 metals on line of sight • But: LBGs also exhibit v > 300 km s–1 outflows • No temporal changes in absorption features have been detected Berger et al. 2006a

  38. GRB Afterglow Spectroscopy Excited states of Si, Fe: • Si II* allows a direct estimate of the density of the absorber • n > 100 cm–3 @ z=4.3 • n ~ 300 cm –3 @ z=6.3 • High local density for GRB 050904 confirmed by radio detection + afterglow model • Fe II* states probably not due to collisional excitation • Radiative pumping may be due to strong ambient IR light or the effect of the GRB/afterglow • Afterglow effects will produce varying absorption features Berger et al. 2006b

  39. The End Image: Aurore Simonnet, Sonoma State

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