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Title: ANATOMY OF A POST-STARBURST MINOR MERGER: A MULTI-WAVELENGTH WFC3 STUDY OF NGC 4150

Abstract

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 themore » 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.« less

Authors:
; ;  [1]; ; ;  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [10];  [11];  [12];  [13];  [14];  [15]
  1. Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom)
  2. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
  3. Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)
  4. Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States)
  5. Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
  6. Department of Physics, ETH-Zurich, Zurich 8093 (Switzerland)
  7. School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom)
  8. Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia)
  9. Association of Universities for Research in Astronomy, Washington, DC 20005 (United States)
  10. Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)
  11. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
  12. NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  13. Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101-1292 (United States)
  14. Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, Via Gobetti 101, 40129 Bologna (Italy)
  15. National Optical Astronomy Observatories, Tucson, AZ 85726-6732 (United States)
Publication Date:
OSTI Identifier:
21567536
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 727; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/727/2/115; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; GALACTIC EVOLUTION; GALAXIES; NEAR ULTRAVIOLET RADIATION; ELECTROMAGNETIC RADIATION; EVOLUTION; RADIATIONS; ULTRAVIOLET RADIATION

Citation Formats

Crockett, R Mark, Kaviraj, Sugata, Silk, Joseph I, Whitmore, Bradley C, Mutchler, Max, Bond, Howard E, O'Connell, Robert W, Balick, Bruce, Calzetti, Daniela, Carollo, C Marcella, Disney, Michael J, Dopita, Michael A, Frogel, Jay A, Hall, Donald N. B., Holtzman, Jon A, Kimble, Randy A, McCarthy, Patrick J, Paresce, Francesco, Saha, Abhijit, and Trauger, John T., E-mail: mark.crockett@astro.ox.ac.uk. ANATOMY OF A POST-STARBURST MINOR MERGER: A MULTI-WAVELENGTH WFC3 STUDY OF NGC 4150. United States: N. p., 2011. Web. doi:10.1088/0004-637X/727/2/115.
Crockett, R Mark, Kaviraj, Sugata, Silk, Joseph I, Whitmore, Bradley C, Mutchler, Max, Bond, Howard E, O'Connell, Robert W, Balick, Bruce, Calzetti, Daniela, Carollo, C Marcella, Disney, Michael J, Dopita, Michael A, Frogel, Jay A, Hall, Donald N. B., Holtzman, Jon A, Kimble, Randy A, McCarthy, Patrick J, Paresce, Francesco, Saha, Abhijit, & Trauger, John T., E-mail: mark.crockett@astro.ox.ac.uk. ANATOMY OF A POST-STARBURST MINOR MERGER: A MULTI-WAVELENGTH WFC3 STUDY OF NGC 4150. United States. doi:10.1088/0004-637X/727/2/115.
Crockett, R Mark, Kaviraj, Sugata, Silk, Joseph I, Whitmore, Bradley C, Mutchler, Max, Bond, Howard E, O'Connell, Robert W, Balick, Bruce, Calzetti, Daniela, Carollo, C Marcella, Disney, Michael J, Dopita, Michael A, Frogel, Jay A, Hall, Donald N. B., Holtzman, Jon A, Kimble, Randy A, McCarthy, Patrick J, Paresce, Francesco, Saha, Abhijit, and Trauger, John T., E-mail: mark.crockett@astro.ox.ac.uk. Tue . "ANATOMY OF A POST-STARBURST MINOR MERGER: A MULTI-WAVELENGTH WFC3 STUDY OF NGC 4150". United States. doi:10.1088/0004-637X/727/2/115.
@article{osti_21567536,
title = {ANATOMY OF A POST-STARBURST MINOR MERGER: A MULTI-WAVELENGTH WFC3 STUDY OF NGC 4150},
author = {Crockett, R Mark and Kaviraj, Sugata and Silk, Joseph I and Whitmore, Bradley C and Mutchler, Max and Bond, Howard E and O'Connell, Robert W and Balick, Bruce and Calzetti, Daniela and Carollo, C Marcella and Disney, Michael J and Dopita, Michael A and Frogel, Jay A and Hall, Donald N. B. and Holtzman, Jon A and Kimble, Randy A and McCarthy, Patrick J and Paresce, Francesco and Saha, Abhijit and Trauger, John T., E-mail: mark.crockett@astro.ox.ac.uk},
abstractNote = {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.},
doi = {10.1088/0004-637X/727/2/115},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 727,
place = {United States},
year = {2011},
month = {2}
}