Ju n 20 08 The Most Luminous Starbursts in the Universe

A summary of starburst luminosities based on PAH features is given for 243 starburst galaxies with 0 < z < 2.5, observed with the Spitzer Infrared Spectrograph. Luminosity νLν(7.7μm) for the peak luminosity of the 7.7μm PAH emission feature is found to scale as log[νLν (7.7μm)] = 44.63(±0.09) + 2.48(±0.28) log(1+z) for the most luminous starbursts observed. Empirical calibrations of νLν(7.7μm) are used to determine bolometric luminosity Lir and the star formation rate (SFR) for these starbursts. The most luminous starbursts found in this sample have log Lir = 45.4(±0.3) + 2.5(±0.3) log(1+z), in ergs s , and the maximum star formation rates for starbursts in units of M⊙ yr are log(SFR) = 2.1(±0.3) + 2.5(±0.3) log(1+z), up to z = 2.5. The exponent for pure luminosity evolution agrees with optical and radio studies of starbursts but is flatter than previous results based in infrared source counts. The maximum star formation rates are similar to the maxima determined for submillimeter galaxies; the most luminous individual starburst included within the sample has log Lir = 46.9, which gives a SFR = 3.4 x 10 M⊙ yr . Subject headings: infrared: galaxies — galaxies: starburst— galaxies: high redshift– galaxies: evolution– galaxies: distances and redshifts