GRBs as a Probe of the Elemental Abundance History of the Universe D. Q. Lamb (U. Chicago) Workshop on Chemical Enrichment of the Early Universe Santa Fe, NM, 13 August 2004

Outline of This Talk  HETE-2 is “going great guns:”  It is currently localizing ~ GRBs yr^-1  It has localized 68 GRBs so far  25 of these localizations have led to the detection of X-ray, optical, or radio afterglows  15 of these afterglows have led to redshift determinations  In this talk, I will discuss: q GRB-SN Connection q Detectability of GRBs and their optical/NIR afterglows out to very high redshifts (z > 5) q GRBs as (possible) powerful probes of cosmology and the early universe

GRB030329: HETE “Hits a Home Run” z =  probability of detecting a bright GRB this close by is ~1/3000 => unlikely that HETE-2 or Swift will see another such event Vanderspek et al. (2004)

GRB030329:Spectrum of SN 2003dh Stanek et al. (2003)

GRB030329: Implications qHETE-2—localized burst GRB030329/SN 2003dh confirms the GRB – SN connection qImplications: q We must understand Type Ib/Ic core collapse SNe in order to understand GRBs q Conversely, we need to understand GRBs in order to fully understand Type Ib/Ic core collapse SNe q Result strengthens the expectation that GRBs occur out to z ~ 20, and are therefore a powerful probe of cosmology and the early universe

Detectability of GRBs Lamb and Reichart (2000)

Detectability of GRB Optical Afterglows Lamb and Reichart (2000)

Evidence for Evolution of GRBs with Redshift Graziani, Lamb, and Donaghy (2004)

Possible Star-Formation Rate Pop III Pop II (Salpeter IMF) Increasing Metallicity Lamb and Reichart (2000)

Possible Differential and Cumulative Distributions of GRBs Lamb and Reichart (2000)  15-25% of GRBs May Lie at z > 5

GRBs in Cosmological Context Lamb (2000)

Predicted Elemental Abundances as Function of Redshift Predictions from Valageas and Silk (1999) GRBs Probe All 3 Sites

GRBs as Probe of Elemental Abundance History of Universe qHigh-resolution IR and near-IR spectra can measure column density and thermal velocity of clouds within GRB host galaxy – perhaps even within the star-forming region in which GRB occurs qEWs of absorption lines provide an estimate of the total star formation that has occurred in damped Ly-alpha and Ly-alpha forest clouds as a function of column density N H of the cloud and redshift z qEWs of absorption lines trace history of heavy element production in universe as function of redshift

GRB

GRB021004: T + 43 sec

GRB021004: T + 73 min

GRB021004: T min

GRB021004: T min (Optical Transient Detected at T + 9 min)

Discovery of GRB Optical Afterglow  Spectroscopic observations 1.6)  Optical afterglow very bright (R = 15.4) at discovery

GRB Optical Afterglow Mirabal et al. (2003)

ALS in Optical Afterglow Spectrum of GRB Mirabal et al. (2003)  LRIS spectrum taken 2002 Oct  Three ALS seen:  z 1 =  z 2 =  z 3 = 2.328

Fragmented Circumburst Nebula Model Mirabal et al. (2003)

Redshift Sub-Components in Optical Afterglow Spectrum of GRB Mirabal et al. (2003)

Column Densities of Elements Savaglio, Fall and Fiore (2003)

Observed Mass of C IV as Function of Redshift Pettini et al. (2003)

Possible Ionization Histories of the Universe Holder et al. (2003)

Advantages of GRBs as Probes of Reionization qGRBs are by far the most luminous events in the universe and are therefore easy to find qGRBs are expected to lie at very high redshifts (z > 5) qOptical and NIR/IR afterglows of GRBs are detectable out to very high redshifts qGRBs produce no “proximity effects” (i.e., no dynamical disturbance or ionization of the IGM) qGRBs have simple power-law spectra and dramatically outshine their host galaxies, making it relatively easy to determine the shape of the red edge of the Gunn- Peterson trough

Reionization Signature in GRB NIR Afterglows

NIR Spectra of GRBs as Probe of Reionization Lamb and Haiman (2004)

NIR Spectra of GRBs as Probe of Reionization Lamb and Haiman (2004)

Conclusions qHETE-2 and follow-up observations have confirmed the connection between GRBs and core-collapse supernovae qThis strengthens likelihood that GRBs exist out to very high redshifts (z > 5) qGRBs and their optical/NIR afterglows are easily visible out to redshifts z ~ 20 qGRBs may therefore provide a powerful probe of q Moment of first light q Star-formation history of the universe q Elemental abundance history of the universe q Reionization history of the universe