NGC 315: High-velocity H I in an active elliptical galaxy
We report the detection of H I in absorption against the nuclear continuum source in the giant elliptical galaxy NGC 315. This is the first reported observation of individually resolved high-velocity H I clouds in or near an elliptical galaxy. The absorption line is highly blueshifted in the reference frame of the galaxy, with a projected velocity toward the galaxy of 490 km s/sup -1/. It is very strong (244 +- 4 mJy) and consists of two components with very narrow velocity widths of 2.5 km s/sup -1/ (FWHM) each. The peak optical depths are 0.9 and 0.2. If the line widths are due solely to thermal broadening, then the kinetic temperature must be 150 K. The neutral gas column densities implied are 2-5 x 10/sup 20/ hydrogen atoms cm/sup -2/. These absorbing clouds are thus very similar to the diffuse H I clouds observed in absorption in the galaxy. We did not detect OH in absorption in these clouds to a limiting peak optical depth of 0.04, but this result is consistent with either a galactic or extragalactic origin of the clouds. They may have condensed out of a large unobserved galactic halo of gas, or they may reside in or have been captured from the intracluster medium.
- OSTI ID:
- 5910253
- Journal Information:
- Astrophys. J., Lett. Ed.; (United States), Vol. 266:2
- Country of Publication:
- United States
- Language:
- English
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