The metallicity evolution of blue compact dwarf galaxies from the
  intermediate redshift to the local Universe
  We present oxygen abundance measurements for 74 blue compact dwarf (BCD)
galaxies in the redshift range in [0.2, 0.5] using the strong-line method. The
spectra of these objects are taken using Hectospec on the Multiple Mirror
Telescope (MMT). More than half of these BCDs had dust attenuation corrected
using the Balmer decrement method. For comparison, we also selected a sample of
2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the
local and intermediate-z BCD samples, we investigated the cosmic evo- lution of
the metallicity, star-formation rate (SFR), and Dn (4000) index. Com- pared
with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio
but similar O32 ratio. Interestingly, no significant deviation in the
mass-metallicity (MZ) relation was found between the intermediate-z and lo- cal
BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR
distribution that was consistent with local BCDs, suggesting a weak de-
pendence on redshift. The intermediate-z BCDs seemed to be younger than the
local BCDs with lower D4000 index values. The insignificant deviation in the
mass-metallicity and mass-SFR relations between intermediate-z and local BCDs
indicates that the relations between the global parameters of low-mass compact
galaxies may be universal. These results from low mass compact galaxies could
be used to place important observational constraints on galaxy formation and
evolution models.
