Anatomy of a post-starburst minor merger

A multi-wavelength WFC3 study of NGC 4150

R. Mark Crockett, Sugata Kaviraj, Joseph I. Silk, Bradley C. Whitmore, Robert W. O'Connell, Max Mutchler, Bruce Balick, Howard E. Bond, Daniela Calzetti, C. Marcella Carollo, Michael J. Disney, Michael A. Dopita, Jay A. Frogel, Donald N B Hall, Jon A. Holtzman, Randy A. Kimble, Patrick J. McCarthy, Francesco Paresce, Abhijit Saha, John T. Trauger & 5 others Alistair R. Walker, Rogier Windhorst, Erick T. Young, Hyunjin Jeong, Sukyoung K. Yi

Research output: Contribution to journalArticle

6 Citations (Scopus)

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 *, early-type galaxy (ETG) of around 6 × 109 M, 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 Hβ 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 ∼0.3-0.5 Ż. 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 ∼3 × 108 M, making NGC 4150 a 1:20 minor merger. A summation of the pixel RSF mass fractions indicates that the RSF contributes ∼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.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume727
Issue number2
DOIs
StatePublished - Feb 1 2011

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anatomy
merger
metallicity
cameras
wavelength
pixel
galaxies
pixels
gas
wavelengths
photometry
star formation
population type
gases
vapor phases
color
stars
stellar models
refueling
starburst galaxies

Keywords

  • Galaxies: elliptical and lenticular, cD
  • Galaxies: evolution
  • Ultraviolet: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Crockett, R. M., Kaviraj, S., Silk, J. I., Whitmore, B. C., O'Connell, R. W., Mutchler, M., ... Yi, S. K. (2011). Anatomy of a post-starburst minor merger: A multi-wavelength WFC3 study of NGC 4150. Astrophysical Journal, 727(2). https://doi.org/10.1088/0004-637X/727/2/115

Anatomy of a post-starburst minor merger : A multi-wavelength WFC3 study of NGC 4150. / Crockett, R. Mark; Kaviraj, Sugata; Silk, Joseph I.; Whitmore, Bradley C.; O'Connell, Robert W.; Mutchler, Max; Balick, Bruce; Bond, Howard E.; 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.; Walker, Alistair R.; Windhorst, Rogier; Young, Erick T.; Jeong, Hyunjin; Yi, Sukyoung K.

In: Astrophysical Journal, Vol. 727, No. 2, 01.02.2011.

Research output: Contribution to journalArticle

Crockett, RM, Kaviraj, S, Silk, JI, Whitmore, BC, O'Connell, RW, Mutchler, M, Balick, B, Bond, HE, Calzetti, D, Carollo, CM, Disney, MJ, Dopita, MA, Frogel, JA, Hall, DNB, Holtzman, JA, Kimble, RA, McCarthy, PJ, Paresce, F, Saha, A, Trauger, JT, Walker, AR, Windhorst, R, Young, ET, Jeong, H & Yi, SK 2011, 'Anatomy of a post-starburst minor merger: A multi-wavelength WFC3 study of NGC 4150', Astrophysical Journal, vol. 727, no. 2. https://doi.org/10.1088/0004-637X/727/2/115
Crockett RM, Kaviraj S, Silk JI, Whitmore BC, O'Connell RW, Mutchler M et al. Anatomy of a post-starburst minor merger: A multi-wavelength WFC3 study of NGC 4150. Astrophysical Journal. 2011 Feb 1;727(2). https://doi.org/10.1088/0004-637X/727/2/115
Crockett, R. Mark ; Kaviraj, Sugata ; Silk, Joseph I. ; Whitmore, Bradley C. ; O'Connell, Robert W. ; Mutchler, Max ; Balick, Bruce ; Bond, Howard E. ; 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. ; Walker, Alistair R. ; Windhorst, Rogier ; Young, Erick T. ; Jeong, Hyunjin ; Yi, Sukyoung K. / Anatomy of a post-starburst minor merger : A multi-wavelength WFC3 study of NGC 4150. In: Astrophysical Journal. 2011 ; Vol. 727, No. 2.
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T2 - A multi-wavelength WFC3 study of NGC 4150

AU - Crockett, R. Mark

AU - Kaviraj, Sugata

AU - Silk, Joseph I.

AU - Whitmore, Bradley C.

AU - O'Connell, Robert W.

AU - Mutchler, Max

AU - Balick, Bruce

AU - Bond, Howard E.

AU - Calzetti, Daniela

AU - Carollo, C. Marcella

AU - Disney, Michael J.

AU - Dopita, Michael A.

AU - Frogel, Jay A.

AU - Hall, Donald N B

AU - Holtzman, Jon A.

AU - Kimble, Randy A.

AU - McCarthy, Patrick J.

AU - Paresce, Francesco

AU - Saha, Abhijit

AU - Trauger, John T.

AU - Walker, Alistair R.

AU - Windhorst, Rogier

AU - Young, Erick T.

AU - Jeong, Hyunjin

AU - Yi, Sukyoung K.

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N2 - 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 *, early-type galaxy (ETG) of around 6 × 109 M⊙, 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 Hβ 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 ∼0.3-0.5 Ż. 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 ∼3 × 108 M⊙, making NGC 4150 a 1:20 minor merger. A summation of the pixel RSF mass fractions indicates that the RSF contributes ∼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.

AB - 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 *, early-type galaxy (ETG) of around 6 × 109 M⊙, 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 Hβ 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 ∼0.3-0.5 Ż. 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 ∼3 × 108 M⊙, making NGC 4150 a 1:20 minor merger. A summation of the pixel RSF mass fractions indicates that the RSF contributes ∼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.

KW - Galaxies: elliptical and lenticular, cD

KW - Galaxies: evolution

KW - Ultraviolet: galaxies

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