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Keywords:

  • galaxies: dwarf;
  • galaxies: evolution;
  • galaxies: general

ABSTRACT

We present a deep [O ii] emission-line survey of faint galaxies (22.5< KAB <24) in the Chandra Deep Field South (CDFS) and the Faint Infra-Red Extragalactic Survey (FIRES) field. With these data we measure the star formation rate (SFR) in galaxies in the stellar mass range 8.85 ≲ log (M*/M) ≲ 9.5 at 0.62 < z < 0.885, to a limit of SFR ∼ 0.1 M yr−1. The presence of a massive cluster (MS1054−03) in the FIRES field, and of significant large-scale structure in the CDFS field, allows us to study the environmental dependence of SFRs amongst this population of low-mass galaxies. Comparing our results with more massive galaxies at this epoch, with our previous survey [Redshift One LDSS-3 Emission Line Survey (ROLES)] at the higher redshift z ∼ 1, and with Sloan Digital Sky Survey (SDSS) Stripe 82 data, we find no significant evolution of the stellar mass function of star-forming galaxies between z = 0 and z ∼ 1, and no evidence that its shape depends on environment. The correlation between specific star formation rate (sSFR) and stellar mass at z ∼ 0.75 has a power-law slope of β ∼ −0.2, with evidence for a steeper relation at the lowest masses. The normalization of this correlation lies as expected between that corresponding to z ∼ 1 and the present day. The global SFR density is consistent with an evolution of the form (1 + z)2 over 0 < z < 1, with no evidence for a dependence on stellar mass. The sSFR of these star-forming galaxies at z ∼ 0.75 does not depend upon the density of their local environment. Considering just high-density environments, the low-mass end of the sSFR–M* relation in our data is steeper than that in Stripe 82 at z = 0, and shallower than that measured by ROLES at z = 1. Evolution of low-mass galaxies in dense environments appears to be more rapid than in the general field.