Astronomy and Astrophysics – Astrophysics
Scientific paper
May 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...444l..77s&link_type=abstract
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 444, no. 2, p. L77-L80
Astronomy and Astrophysics
Astrophysics
66
Elliptical Galaxies, Galactic Structure, H I Regions, Interacting Galaxies, Interstellar Matter, Radio Observation, Mass Distribution, Mass To Light Ratios, Star Distribution, Velocity Distribution
Scientific paper
We report the discovery of neutral hydrogen in a second elliptical galaxy with shells, NGC 2865. Very Large Array (VLA) images reveal an association between the neutral hydrogen (H I) and the fine structure (shells, tails, and loops) in the galaxy. Similar to what we previously observed in NGC 5128 (Centaurus A), most of the 6 x 108/h2 solar mass of cold gas is found in a broken ring in the outer regions of NGC 2865 (beyond 0.5D25) and is displaced to the outside of the shells and loops. The measured velocities cover a range of 500 km/s around the systematic velocity. The velocity field of the outer H I has the same sense and magnitude (and line of nodes) as that of the stars in the elliptical body. Although NGC 2865 appears to be a relaxed elliptical galaxy, deep images, photometry, and spectroscopy suggest that the galaxy might be the recent (less than 7 Gyr) product of a major disk-disk merger -- a 'dynamically young elliptical.' Our H I data support this hypothesis. Nevertheless, the association between gas and stellar fine structure, with gas displaced outward from the stars in projected position, implies gas motions not predicted by any of the current merger scenarios. Using the H I ring and assuming nearly circular motion, we measure M/LB at large radii (4 x 0.5D25). We find M/LB = 33 +/- 4 h, a factor of 5 greater than the value of M/LB found for the central regions, indicating the presence of a dark halo.
Malin David F.
Schiminovich David
van der Hulst J. M.
van Gorkom Jacqueline H.
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