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GRBs as cosmological probes

GRBs as cosmological probes. Thomas Krühler (DARK) Thanks to J. Fynbo , D. Malesani , J. Hjorth , J. Greiner, D. A. Kann , D. Perley , N. Tanvir , S. Klose and many others. Very High Energy Phenomena in the Universe 2013 @ La Thuile 1 3/03/2013 . GRB as probes.

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GRBs as cosmological probes

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  1. GRBs as cosmological probes Thomas Krühler (DARK) Thanks to J. Fynbo, D. Malesani, J. Hjorth, J. Greiner, D. A. Kann, D. Perley, N. Tanvir, S. Klose and many others Very High Energy Phenomena in the Universe 2013 @ La Thuile13/03/2013

  2. GRB as probes Image Credit Nature 2008

  3. Afterglows and redshifts

  4. Afterglows Bright, well studied but only ~20 % of Swift afterglows 10 cm With 2m telescopes: Observationally accessible but only ~50% 60 cm 2 m Afterglows, that we typically miss: Intrinsically faint ? dust extinguished ? high-z ? 8 m Kann+ 10

  5. GRB studies in the sample Era P60 (Cenko+ 09, Perley+ 09) UVOT (Roming+ 09, Oates+ 09) GROND (Greiner+ 10, TK+ 11) Liverpool & FTS/N (Melandri+ 08) VLT (Fynbo+ 10, Zafar+ 11) ROTSE (Rykoff+ 09) Dark hosts (Perley+ 09, 13) VLT hosts (Hjorth+ 12, Malesani+ 12, Jakobsson+12, Milvang-Jensen+ 12, TK+ 12) VLT dark hosts (Rossi+ 12) Bright Swift events (Salvaterra+ 12, Melandri+ 12, Campana+ 12, Nava+ 12, D’Avanzo+12, Covino+ 13)

  6. GRB redshifts

  7. Afterglows and redshifts From afterglow spectroscopy Fynbo+ 09

  8. Afterglows and redshifts From afterglow photometry Very good and robust photo-z’s up to z ~ 10 Simple spectrum Unique identification TK+ 11

  9. Afterglows and redshifts From host spectroscopy Requires good position (Swift/XRT or better < 3”) Is not time critical Can easily be performed for ‘old’ GRB

  10. GRBs at the highest redshifts

  11. GRBs as probes of high-redshift SF GRBs at redshift z > 8 GRB 090423: Spectroscopic redshift of z = 8.2 (Tanvir+ 2009, Salvaterra+ 2009) GRB 090429B: Photometric redshift of z ~ 9.4 (Cucchiara+ 2011)

  12. GRBs as probes of high-redshift SF No detection of GRB hosts at z > 5 in ultra-deep HST pointings -> A lot of high-z star-formation is undetected in current surveys Tanvir+ 2012 Probing the galaxy luminosity function below sensitivity limits of even the deepest surveys

  13. GRBs as probes of star-formation

  14. GRBs as probes of high-redshift SF The fraction of high-z GRBs (Greiner+ 10) 5.5 +/- 2.8 % z > 5 (Greiner+ 10) < 14 %, < 7 % z > 5, z > 7 (Perley+ 09) 3-5 %, 0.2-0.7 % z > 5, z > 8 (Salvaterra+ 12) < 14 %, < 5 % z > 6, z > 7 (Jakobsson+ 12) cp. SDSS/CFHT QSO: (~0.05 %) z > 5.7 (Willott+ 10) (Hjorth+ 12, Malesani+ 12, Jakobsson+ 12)

  15. GRBs as probes of high-redshift SF Connect SFR w. GRB rate: None to strong evolution: -> a ~ 0 … 2 (Virgili+11, Wang & Dai 11, Elliott+ 11, Jakobsson+12, Robertson & Ellis 12, Salvaterra+ 12, Coward+ 12) (Robertson & Ellis 12)

  16. GRBs hosts as probes of galaxies

  17. GRBs as probes of high-redshift galaxies Fruchter+ 06

  18. The TOUGH sample Hjorth+12, Jakobsson+ 12, Milvang-Jensen+12, TK+ 12, Michalowski+12: Large (69 -> 200), uniform, X-ray-selected, well-defined (no physical biases), deep (observed with the most sensitive instrumentation)

  19. The TOUGH sample

  20. GRBs as probes of high-redshift galaxies TK+ 2011 Perley+ 2013 Large columns of dust regularly detected. Dominant cause of ‘dark’ bursts -> Physical selection effect in redshift determination -> Biases in redshift distribution, physical properties inferred from optical follow-up (and any quantity that requires a redshift)

  21. GRBs as probes of high-redshift galaxies 3. The hosts of long GRBs The hosts of dark, dust-extinguished GRBs have hosts that are redder, more luminous, higher mass, star-formation higher metallicity hosts than the hosts of optically bright GRBs TK+ 11

  22. Dark burst samples Perley+ 12 GRB hosts missing from previous sample studies are: -> Redder -> More luminous, more massive -> More star-forming

  23. Optically unbiased samples Hjorth+ 12

  24. GRBs as probes of high-redshift galaxies

  25. GRBs as probes of high-redshift galaxies 3. The hosts of long GRBs GRBs appear in all star-forming environments No metallicity cut-off They are clustered at the low-mass end of the galaxy distribution at low redshift If metallicity is indeed the driver of this relation, the trend should soften/disappear at z ~ 2 / 3 (Perley+ 13)

  26. GRBs as probes of cosmic chemical enrichment

  27. GRBs as probes of cosmic chemical enrichment Savaglio+ 12 TK+ 13

  28. GRBs as probes of cosmic chemical enrichment Vreeswijk+ 07 TK+ 13

  29. GRBs as probes of molecular gas GRB 120815A X-shooter spectrum TK+ 13 GRB 080607 LRIS spectrum Direct probe of molecular gas (H2 & CO) at high-redshift. Key quantity for star-formation, directly accessible through GRB and QSO-DLAs Prochaska+ 09

  30. Take-home messages Efficient measurement of GRB redshifts based on host galaxies at z < 4 != time critical != optical afterglows requires only ! good position (X-ray, optical, sub-mm, radio) ! Not a function of feasibility (only resources)

  31. Take-home messages GRBs emerged as the class of objects with the highest spectroscopic redshifts (z = 8.2, stay tuned for updates) Afterglow photo-z’s (up to z ~ 9.4 and beyond) are accurate, robust and unique Studies of metals/dust/gas deep in the ‘dark’ ages Huge potential with ALMA synergies

  32. Take-home messages GRBs are efficient tools for probes of galaxy evolution and star-formation up to z ~ 8 GRBs are hosted by all types of galaxies, including very metal rich ones (> solar) There are evolutionary effects at low-z, likely due to metallicity Accurate quantification is ongoing Likely not dominant at z > 2 - 3

  33. Take-home messages GRBs are routinely used as probes of cosmic chemical enrichment (up to z ~ 5 for now) Provide accurate, direct metallicities (like QSOs) Couple with galaxy studies (unlike QSOs) Probing the metals, gas and molecular content of star-forming regions and galaxies in unprecedented detail

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