Probing star formation in galaxies at z ≃ 1 via a Giant Metrewave Radio Telescope stacking analysis.
BERA A., KANEKAR N., WEINER B.J., SETHI S. and DWARAKANATH K.S.
Abstract (from CDS):
We report deep Giant Metrewave Radio Telescope (GMRT) 610 MHz continuum imaging of four subfields of the DEEP2 Galaxy Redshift Survey. We stacked the radio emission in the GMRT images from a near-complete (absolute blue magnitude MB <= -21) sample of 3698 blue star-forming galaxies with redshifts 0.7 <= z <= 1.45 to detect (at ≃17σ significance) the median rest-frame 1.4 GHz radio continuum emission of the sample galaxies. The stacked emission is unresolved, with a rest-frame 1.4 GHz luminosity of L1.4GHz = (4.13 ± 0.24) x 1022 W Hz–1. We used the local relation between total star formation rate (SFR) and 1.4 GHz luminosity to infer a median total SFR of (24.4 ± 1.4) M☉ yr–1 for blue star-forming galaxies with MB <= -21 at 0.7 <= z <= 1.45. We detect the main-sequence relation between SFR and stellar mass, M*, obtaining SFR = (13.4 ± 1.8) x [(M*/1010 M☉)]0.73±0.09 M☉ yr–1; the power-law index shows no change over z ≃ 0.7-1.45. We find that the nebular line emission suffers less extinction than the stellar continuum, contrary to the situation in the local universe; the ratio of nebular extinction to stellar extinction increases with decreasing redshift. We obtain an upper limit of 0.87 Gyr to the atomic gas depletion time of a subsample of DEEP2 galaxies at z ≃ 1.3; neutral atomic gas thus appears to be a transient phase in high-z star-forming galaxies.