We have used the Giant Metrewave Radio Telescope (GMRT) to carry out deep 610 MHz continuum imaging of four sub-fields of the DEEP2 Galaxy Redshift Survey. We stacked the radio emission in the GMRT images from a near-complete (absolute blue magnitude ${rm M_B} leq -21$) sample of 3698 blue star-forming galaxies with redshifts $0.7 lesssim z lesssim 1.45$ to detect (at $approx 17sigma$ 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 $rm L_{1.4 ; GHz} = (4.13 pm 0.24) times 10^{22}$ 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 $rm (24.4 pm 1.4); M_odot$ yr$^{-1}$ for blue star-forming galaxies with $rm M_B leq -21$ at $0.7 lesssim z lesssim 1.45$. We detect the main-sequence relation between SFR and stellar mass, $rm M_star$, obtaining $rm SFR = (13.4 pm 1.8) times [(M_{star}/(10^{10} ;M_odot)]^{0.73 pm 0.09} ; M_odot ; yr^{-1}$; the power-law index shows no change over $z approx 0.7 - 1.45$. 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 sub-sample of the DEEP2 galaxies at $z approx 1.3$; neutral atomic gas thus appears to be a transient phase in high-$z$ star-forming galaxies.
تحميل البحث