Probing star formation in galaxies at $z \approx 1$ via a Giant
  Metrewave Radio Telescope stacking analysis
  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 $\approx 17\sigma$
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.
