ANATOMY OF A POST-STARBURST MINOR MERGER: A MULTI-WAVELENGTH WFC3 STUDY OF NGC 4150
- Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
- Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)
- Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States)
- Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
- Department of Physics, ETH-Zurich, Zurich 8093 (Switzerland)
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom)
- Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia)
- Association of Universities for Research in Astronomy, Washington, DC 20005 (United States)
- Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)
- Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
- NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101-1292 (United States)
- Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, Via Gobetti 101, 40129 Bologna (Italy)
- National Optical Astronomy Observatories, Tucson, AZ 85726-6732 (United States)
We present a spatially resolved near-UV/optical study, using the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope, of NGC 4150, a sub-L{sub *}, early-type galaxy (ETG) of around 6 x 10{sup 9} M{sub sun}, which has been observed as part of the WFC3 Early-Release Science Programme. Previous work indicates that this galaxy has a large reservoir of molecular hydrogen gas, exhibits a kinematically decoupled core (a likely indication of recent merging) and strong, central H{beta} absorption (indicative of young stars). While relatively uninspiring in its optical image, the core of NGC 4150 shows ubiquitous near-UV emission and remarkable dusty substructure. Our analysis shows this galaxy to lie in the near-UV green valley, and its pixel-by-pixel photometry exhibits a narrow range of near-UV/optical colors that are similar to those of nearby E+A (post-starburst) galaxies and lie between those of M83 (an actively star-forming spiral) and the local quiescent ETG population. We parameterize the properties of the recent star formation (RSF; age, mass fraction, metallicity, and internal dust content) in the NGC 4150 pixels by comparing the observed near-UV/optical photometry to stellar models. The typical age of the RSF is around 0.9 Gyr, consistent with the similarity of the near-UV colors to post-starburst systems, while the morphological structure of the young component supports the proposed merger scenario. The typical RSF metallicity, representative of the metallicity of the gas fuelling star formation, is {approx}0.3-0.5 Z{sub sun}. Assuming that this galaxy is a merger and that the gas is sourced mainly from the infalling companion, these metallicities plausibly indicate the gas-phase metallicity (GPM) of the accreted satellite. Comparison to the local mass-GPM relation suggests (crudely) that the mass of the accreted system is {approx}3 x 10{sup 8} M{sub sun}, making NGC 4150 a 1:20 minor merger. A summation of the pixel RSF mass fractions indicates that the RSF contributes {approx}2%-3% of the stellar mass. This work reaffirms our hypothesis that minor mergers play a significant role in the evolution of ETGs at late epochs.
- OSTI ID:
- 21567536
- Journal Information:
- Astrophysical Journal, Vol. 727, Issue 2; Other Information: DOI: 10.1088/0004-637X/727/2/115; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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