THE NEUTRAL INTERSTELLAR-MEDIUM IN NEARBY DWARF GALAXIES .2. NGC-185,NGC-205, AND NGC-147

We present new, high-resolution observations of the interstellar mediu m (ISM) in the two dwarf elliptical galaxies NGC 185 and NGC 205, as w ell as a new upper limit on the H I content of the dwarf elliptical ga laxy NGC 147. The data consist of VLA observations of H I emission at similar to 80 pc resolution (a factor of 3.5 improvement over older da ta), CO spectra at similar to 80 pc resolution in NGC 185 and NGC 205, an image of CO emission in NGC 205 at 40 x 20 pc resolution from the BIMA array, and Ha images of NGC 185 and NGC 205. These observations r epresent the intersection of two separate fields of inquiry: (1) the d istribution, kinematics, and origin of neutral gas in giant elliptical s, which are structurally similar to the dwarf ellipticals but cannot currently be studied at such high linear resolution; and (2) the physi cal properties of the ISM in the Galaxy and its neighbors, which can b e studied at very high linear resolution but which. might have very di fferent interstellar media than elliptical galaxies. The new H I image s show that the neutral gas and stars of NGC 205 are two distinct dyna mical systems, whereas in NGC 185 the gas and stars may be parts of th e same dynamical system. The H I distributions in these galaxies are l ess extended than the optical emission and do not appear to be stable rotating disks, a result that is very different from the pattern estab lished for giant ellipticals. An internal gas origin (mass loss from e volved stars) may be plausible for NGC 185. No H I emission is detecte d in NGC 147 with an upper limit of 3 x 10(3) M. for an unresolved sou rce with a line width of 8 km s(-1). Furthermore, the H I distribution s in NGC 185 and 205 are extremely clumpy on size and mass scales less than 200 pc and similar to 10(4) M., with H I velocity dispersions ra nging from 3 to 15 km s(-1). We present evidence that the molecular ga s in these galaxies is associated with individual clumps or clouds of atomic gas, similar to many Galactic giant molecular clouds. However, the H I column densities in the dwarf ellipticals are factors of 5-10 less than the 10(21) cm(-2) thought to be necessary to shield Galactic giant molecular clouds against photodissociation. Images of NGC 185 i n H alpha + [N II] show an extended region of emission 50 pc in diamet er near the center of the galaxy and the H I column density peak.