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Todays (extra) Colloquium: Which Galaxies Produce Gamma-Ray Bursts? New Clues from EVLA Observations

Submitter: Daniel Perley (CalTech)
Description: Star-formation at redshifts about z>1 tends to occur primarily in regions of significant dust obscuration, making much of it invisible to ultraviolet and optical light. As the product of dying massive stars, long-duration gamma-ray bursts and their host galaxies should reflect this trend, but observations to date have found very few events within the luminous or ultra-luminous galaxies that dominate the star formation rate density in the distant universe. This has led to suggestions that GRBs cannot occur or are heavily suppressed in such systems, perhaps due to metallicity-related effects.

With the EVLA's sensitivity, we can now search for the radio-continuum signatures of star formation without the biases of optical/UV-selection in a reasonable observation time, even at cosmological distances. Indeed, several systems have been detected in the radio between z=0.8-3.1, indicating that GRBs do occur in these galaxies at an appreciable rate. GRBs therefore probably occur in all classes of star-forming galaxy in the high-redshift universe, although their rate in the most luminous objects still appears to be less than the simplest assumptions would predict.
Copyright: D. Perley
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