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Stellar kinematics in the nucleus of NGC 6240: A massive galaxy revealedWe have used the 2.3 micron bandhead of CO to measure the kinematics of the red stellar population in the nucleus of the luminous galaxy NGC 6240, the near-infrared spectrum of which is dominated by lines of shocked gas. With this manifest evidence for dissipative effects in the gas, it is such stellar velocity dispersion that is most unambiguously indicative of gravitational potential. We find a nuclear velocity dispersion sigma = 350 km/sec which is considerably larger than that seen in any gaseous component of this galaxy. At least one partner in this merger must therefore have been very massive, with M(sub B) approximately -23. In view of conventional wisdom that the high luminosity of NGC 6240 derives from star formation, it is suprising that we find M/L to be of order unity. While there seems to be little question that star formation is taking place in this interacting system, this high M/L calls into question the importance of star formation in the luminosity budget of the galaxy. In particular, it seems likely that the red starlight in NGC 6240 is produced by giants rather than a population of young red supergiants. This brings into question the (now reflexive) association of relatively deep CO bands in galaxies (which are conspicuously strong in NGC 6240) with recent star formation.
Document ID
19950030768
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lester, Dan F.
(Univ. of Texas at Austin, Austin, TX United States)
Gaffney, Niall I.
(Univ. of Texas at Austin, Austin, TX United States)
Date Acquired
August 16, 2013
Publication Date
August 10, 1994
Publication Information
Publication: The Astrophysical Journal, Part 2 - Letters
Volume: 431
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A62367
Funding Number(s)
CONTRACT_GRANT: NAG2-748
CONTRACT_GRANT: NSF AST-93-15646
CONTRACT_GRANT: NGC-51138
Distribution Limits
Public
Copyright
Other

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