Stellar populations of early-type galaxies with mid-infrared excess emission

Journal Article · Fri Apr 01 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/820/2/132· OSTI ID:22890094

Ko, Jongwan; Lee, Jong Chul ^[1]; Chung, Haeun

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1. Korea Astronomy and Space Science Institute, Daejeon 34055 (Korea, Republic of)

We present a stellar population analysis of quiescent (without Hα emission) and bright (M{sub r} < −21.5) early-type galaxies (ETGs) with recent star formation. The ETGs are selected from a spectroscopic sample of SDSS galaxies at 0.04 < z < 0.11 with WISE mid-infrared (IR) and GALEX near-ultraviolet (UV) emissions. We stack the optical spectra of ETGs with different amounts of mid-IR and near-UV excess emissions to measure the strength of 4000 Å break D{sub n}4000 and the width of Balmer absorption line Hδ{sub A} that are indicative of recent (∼1 Gyr) star formation activity. The WISE [3.4]–[12] colors show stronger correlations with the spectral features than NUV–r colors. We fit to the stacked spectra with a spectral fitting code, STARLIGHT, and find that the mass fraction of young (⩽1 Gyr) and intermediate-age (∼1–5 Gyr) stars in the ETGs with mid-IR excess emission is ∼4%–11%, depending on the template spectrum used for the fit. These results show that the ETGs with mid-IR excess emission have experienced star formation within the last 1–5 Gyr and that the mid-IR emission is a useful diagnostic tool for probing recent star formation activity in ETGs.

• OSTI ID: 22890094
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 820; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
EMISSION
GALACTIC EVOLUTION
GALAXIES
INTERMEDIATE INFRARED RADIATION
MASS
POPULATIONS
SPECTRA
STACKS
STARS
ULTRAVIOLET RADIATION