skip to main content

SciTech ConnectSciTech Connect

Title: 'Direct' gas-phase metallicities, stellar properties, and local environments of emission-line galaxies at redshifts below 0.90

Using deep narrow-band (NB) imaging and optical spectroscopy from the Keck telescope and MMT, we identify a sample of 20 emission-line galaxies at z = 0.065-0.90 where the weak auroral emission line, [O III] λ4363, is detected at ≥3σ. These detections allow us to determine the gas-phase metallicity using the 'direct' method. With electron temperature measurements, and dust attenuation corrections from Balmer decrements, we find that four of these low-mass galaxies are extremely metal-poor with 12 + log (O/H) ≤ 7.65 or one-tenth solar. Our most metal-deficient galaxy has 12 + log (O/H) = 7.24{sub −0.30}{sup +0.45} (95% confidence), similar to some of the lowest metallicity galaxies identified in the local universe. We find that our galaxies are all undergoing significant star formation with average specific star formation rate (SFR) of (100 Myr){sup –1}, and that they have high central SFR surface densities (average of 0.5 M {sub ☉} yr{sup –1} kpc{sup –2}). In addition, more than two-thirds of our galaxies have between one and four nearby companions within a projected radius of 100 kpc, which we find is an excess among star-forming galaxies at z = 0.4-0.85. We also find that the gas-phase metallicities for a given stellar massmore » and SFR lie systematically lower than the local M {sub *}-Z-(SFR) relation by ≈0.2 dex (2σ significance). These results are partly due to selection effects, since galaxies with strong star formation and low metallicity are more likely to yield [O III] λ4363 detections. Finally, the observed higher ionization parameter and high electron density suggest that they are lower redshift analogs to typical z ≳ 1 galaxies.« less
Authors:
 [1] ;  [2] ;  [3] ; ;  [4] ;  [5]
  1. Space Telescope Science Institute, Baltimore, MD (United States)
  2. Department of Physics and Astronomy, UCLA, Los Angeles, CA (United States)
  3. Research Center for Space and Cosmic Evolution, Ehime University, Matsuyama (Japan)
  4. Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo (Japan)
  5. Department of Astronomy, School of Science, University of Tokyo, Bunkyo, Tokyo (Japan)
Publication Date:
OSTI Identifier:
22348259
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CORRECTIONS; DENSITY; DETECTION; DUSTS; ELECTRON DENSITY; ELECTRON TEMPERATURE; EMISSION; GALAXIES; MASS; METALLICITY; PHOTOMETRY; RED SHIFT; SPECTROSCOPY; STAR EVOLUTION; STARS; TELESCOPES; UNIVERSE