Tidal tails of minor mergers. II. Comparing star formation in the tidal tails of NGC 2782

Karen A. Knierman, Paul Scowen, Todd Veach, Christopher Groppi, Brendan Mullan, Iraklis Konstantopoulos, Patricia M. Knezek, Jane Charlton

Research output: Contribution to journalArticle

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Abstract

The peculiar spiral NGC 2782 is the result of a minor merger with a mass ratio ∼4: 1 occurring ∼200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun. However, deep UBVR and Hα narrowband images show evidence of recent star formation in the western tail, though it lacks massive star clusters and cluster complexes. Using Herschel PACS spectroscopy, we discover 158 μm [C II] emission at the location of the three most luminous Hα sources in the eastern tail, but not at the location of the even brighter Hα source in the western tail. The western tail is found to have a normal star formation efficiency (SFE), but the eastern tail has a low SFE. The lack of CO and [C II] emission suggests that the western tail H II region may have a low carbon abundance and be undergoing its first star formation. The western tail is more efficient at forming stars, but lacks massive clusters. We propose that the low SFE in the eastern tail may be due to its formation as a splash region where gas heating is important even though it has sufficient molecular and neutral gas to make massive star clusters. The western tail, which has lower gas surface density and does not form high-mass star clusters, is a tidally formed region where gravitational compression likely enhances star formation.

Original languageEnglish (US)
Article number125
JournalAstrophysical Journal
Volume774
Issue number2
DOIs
StatePublished - Sep 10 2013

Fingerprint

merger
star formation
gas
star clusters
massive stars
spectroscopy
compression
heating
carbon
neutral gases
H II regions
molecular gases
mass ratios
narrowband
stars
gases

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Knierman, Karen A. ; Scowen, Paul ; Veach, Todd ; Groppi, Christopher ; Mullan, Brendan ; Konstantopoulos, Iraklis ; Knezek, Patricia M. ; Charlton, Jane. / Tidal tails of minor mergers. II. Comparing star formation in the tidal tails of NGC 2782. In: Astrophysical Journal. 2013 ; Vol. 774, No. 2.
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abstract = "The peculiar spiral NGC 2782 is the result of a minor merger with a mass ratio ∼4: 1 occurring ∼200 Myr ago. This merger produced a molecular and H I-rich, optically bright eastern tail and an H I-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun. However, deep UBVR and Hα narrowband images show evidence of recent star formation in the western tail, though it lacks massive star clusters and cluster complexes. Using Herschel PACS spectroscopy, we discover 158 μm [C II] emission at the location of the three most luminous Hα sources in the eastern tail, but not at the location of the even brighter Hα source in the western tail. The western tail is found to have a normal star formation efficiency (SFE), but the eastern tail has a low SFE. The lack of CO and [C II] emission suggests that the western tail H II region may have a low carbon abundance and be undergoing its first star formation. The western tail is more efficient at forming stars, but lacks massive clusters. We propose that the low SFE in the eastern tail may be due to its formation as a splash region where gas heating is important even though it has sufficient molecular and neutral gas to make massive star clusters. The western tail, which has lower gas surface density and does not form high-mass star clusters, is a tidally formed region where gravitational compression likely enhances star formation.",
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Knierman, KA, Scowen, P, Veach, T, Groppi, C, Mullan, B, Konstantopoulos, I, Knezek, PM & Charlton, J 2013, 'Tidal tails of minor mergers. II. Comparing star formation in the tidal tails of NGC 2782', Astrophysical Journal, vol. 774, no. 2, 125. https://doi.org/10.1088/0004-637X/774/2/125

Tidal tails of minor mergers. II. Comparing star formation in the tidal tails of NGC 2782. / Knierman, Karen A.; Scowen, Paul; Veach, Todd; Groppi, Christopher; Mullan, Brendan; Konstantopoulos, Iraklis; Knezek, Patricia M.; Charlton, Jane.

In: Astrophysical Journal, Vol. 774, No. 2, 125, 10.09.2013.

Research output: Contribution to journalArticle

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Knierman KA, Scowen P, Veach T, Groppi C, Mullan B, Konstantopoulos I et al. Tidal tails of minor mergers. II. Comparing star formation in the tidal tails of NGC 2782. Astrophysical Journal. 2013 Sep 10;774(2). 125. https://doi.org/10.1088/0004-637X/774/2/125