Abstract:
We report observations of H alpha nebulosities in the X-ray bright
elliptical galaxies which are members of nearby groups of galaxies or
clusters. Our sample includes NGC 1399, NGC 1600, NGC 2563, NGC
3607, NGC 4203, NGC 4636, NGC 4753 and NGC 5044. Some of these
galaxies have X-ray cooling flows. The results are based on CCD surface
photometry carried out using the broad band filters V and R. and a narrow
band filter appropriate for the red-shifted Ha + [N II] emission. We
present the integrated Ha luminosities in these galaxies and examine
various emission mechanisms. Photoionization by young stars is a
viable mechanism. New features like dust and shells with blue colours have
been discovered in some galaxies. The presence of the 10*K gas is asso-
ciated with the presence of such features indicative of galaxy-galaxy interac-
tions. In NGC 3607, rings or a disk of dust surrounds the ionized gas. In
NGC 4753, a very complex system of dust lanes is observed. We suggest
that the dust and associated gas in NGC 3607 is acquired from an
interacting neighbour NGC 3608. Accretion events or mergers may be
common in these galaxies.