NEW OBSERVATIONS OF NGC-1275 - PECULIAR VELOCITIES IN THE HIGH-VELOCITY SYSTEM

Spectroscopic observations of several off-nuclear regions in the peculiar galaxy NGC 1275 have been obtained. These show the following new features. (1) The high-velocity gas does not show a smooth gradient of ∼ 300 km s-1 as has been claimed previously but appears disrupted, having a velocity range of 600 km s-1. (2) Stellar absorption is seen from the high-velocity system in the Ca II λ8498 line. Although other stellar absorption lines are not seen, this is consistent with a presumed early-type stellar population and with the difficulty of subtracting bright night sky emission lines in the Ca II triplet region. (3) Absorption is seen from the high-velocity system in the Na I D lines. This is seen clearly where the low-velocity continuum is strong, and so is likely to arise in gas. The implications of these findings for the various proposed explanations of the high-velocity emission are examined. Although the presence of star light adds further weight to the arguments against the ejection hypothesis, the new velocity information makes interpretation of the high-velocity system as an unperturbed galaxy very unlikely. Either the emission-line velocities do not represent motion governed by the internal dynamics of the galaxy, or the galaxy is extremely peculiar in size, H I content, and structure. In the former case, an argument can be made that the emission-line gas is in the process of being decelerated by interaction with the low-velocity gas.