Extreme [O III] Emitters at z ∼ 0.5
Abstract
We have found a sample of extreme emission-line galaxies (EELGs) with strong [O III]λ5007 emission at z ∼ 0.5. Using broadband photometric selection and requiring small uncertainties in photometry, we searched the 14th Data Release of the Sloan Digital Sky Survey (SDSS) and found 2658 candidates with strong i-band excess (i - z ≤ r - i - 0.7). We further obtained 649 SDSS spectra of these objects, and visually identified 22 [O III] emitters lying at 0.40 < z < 0.63. Having constructed their ultraviolet-infrared spectral energy distributions, we found that they have fairly blue r - W2 and red W1 - W4 colors, indicative of strong, warm dust emission. Their rest-frame [O III]λ5007 equivalent widths are mostly 200-600 Å, and their high [O III]λ5007/Hβ ratios put them at the boundary of star-forming galaxies and active galactic nuclei on line ratio classification diagrams. The typical E(B-V) and electron temperature of [O III] emitters are ∼0.1-0.3 mag and ∼104 K, respectively. The lowest metallicity of our [O III] emitters with S/N[O III]λ4363 > 3 is 12 + log(O/H) = {7.98}-0.02+0.12, with a median value of {8.24}-0.04+0.05. Our [O III] emitters exhibit remarkably high line luminosity—18/22 have L [O III]λ5007 > 5 × 1042 erg s-1 and 5/22 have L [O III]λ5007 > 1043 erg s-1. Their estimated volume number density at z ∼ 0.5 is ∼2 × 10-8 Mpc-3, with L [O III]λ5007 down to ∼3 × 1042 erg s-1. The cumulative number distribution of EELGs across different redshifts is indicative of a strong redshift evolution at the bright end of the [O III] luminosity function.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2018
- DOI:
- 10.3847/1538-4357/aabfd9
- arXiv:
- arXiv:1804.11309
- Bibcode:
- 2018ApJ...860...83L
- Keywords:
-
- galaxies: dwarf;
- galaxies: luminosity function;
- galaxies: ISM;
- galaxies: starburst;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 23 pages, 15 figures, accepted for publication in ApJ