View
217
Download
2
Embed Size (px)
Citation preview
(Long) Gamma-Ray Bursts as
cosmological probes
(Long) Gamma-Ray Bursts as
cosmological probes
Davide Lazzati (JILA, U of Colorado)
Gabriele Ghisellini (OAB); Giancarlo Ghirlanda (OAB); Claudio Firmani (OAB); Lara Nava (OAB); Vladimir Avila-Reese
(UNAM)
•Standard Candles•Lighthouses•Tracers of star formation
GRBs are NOT standard candlesGRBs are NOT
standard candlesGhirlanda et al. 2004
GRB energies
span three orders of magnitude
““StretchingStretching”: the ”: the
slower the slower the brighterbrighter
Sne Ia are not standard either,
but…
Sne Ia are not standard either,
but…
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Correlations…Correlations…As seen by Lamb et al. 2005
Original correlation in Frail et al. 2001 and Panaitescu & Kumar 2001
Reichart et al. 2001 Norris et al. 2000
EE peak
peak=k E
=k E
0.69
0.69
Ghirlanda, Ghisellini & Lazzati 2004
Ghirlanda, Ghisellini & Lazzati 2004Ghirlanda
correlationGhirlanda
correlation
Ghirlanda cosmologyGhirlanda cosmology
Ghirlanda et al. 2004
Ghirlanda cosmologyGhirlanda cosmology
Ghirlanda et al. 2004
Very controversial result (e.g. Friedman & Bloom 2005)
Ambient mediumAmbient mediumThe ISM
density plays a small role
in the Ghirlanda
correlation. But the density profile….
Ep’ ~ E
Opening angle
systematically smaller for wind profile
Nava et al. 2005
LighthousesLighthousesGRB 021004: Flasher et al. in prep.
CIV
LighthousesLighthousesGRB 021004: Flasher et al. in prep.
CIV
2.5 evidence of decrease of the EW of high velocity CIV features
LighthousesLighthousesGRB 021004: Flasher et al. in prep.
Wind extends to tens of parsecs implies very massive star. Why afterglow fits require homogeneous ISM?
Tracers for star formation
Tracers for star formation
• Long GRBs associated to final evolutionary stages of massive star
• Very easy to detect so in principle rate of explosion can be constrained
• But IMF may change• And additional ingredients required (metallicity, rotation, binarity)
SummarySummary• GRBs are useful cosmological tools from many points of view
• Analogously to SN Ia can be standardized by using correlations among observables
• The field is in its infancy: different correlations can be used and we do not really know what to chose yet. All give comparable results.
• Nevertheless GRBs have comparable constraining capabilities to SN Ia and are much easier to detect, especially at high redshift
• Absorption spectra can be used for studying local GRB environment; ISM; IGM (see talks later today)
• Rate of GRBs constrains SFR but more details need to be figured out before we can really constrain