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Date and Time of the Query: 2019-05-25 T22:18:52 PDT
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For refcode 1994A&AS..105..341G:
Retrieve 56 NED objects in this reference.
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1994A&AS..105..341G Interstellar matter in Shapley-Ames elliptical galaxies. II. The distribution of dust and ionized gas* P. Goudfrooij, L. Hansen, H.E. Jorgensen and H.U. Norgaard-Nielsen Astronomical Institute "Anton Pannekoek", University of Amsterdam, Kruislaan 403, NL-1098 SJ Amsterdam, The Netherlands Copenhagen University Observatory, Oster Voldgade 3, DK-1350 Kobenhavn K, Denmark Danish Space Research Institute, Gl. Lundtoftevej 7, DK-2800 Lyngby, Denmark Received November 22, accepted December 21, 1993 Abstract. - We present results of deep optical CCD imaging for a complete, optical magnitude-limited sample of 56 elliptical galaxies from the RSA catalog. For each galaxy we have obtained broad-band images (in B, V, and I) and narrow-band images using interference filters isolating the H{alpha}+[N II] emission lines to derive the amount and morphology of dust and ionized gas. Detailed consideration of systematic errors due to effects of sky background subtraction and removal of stellar continuum light from the narrow-band images is described. The flux calibration of the narrow-band images is performed by deconvolving actually measured spectral energy distributions with the filter transmission curves. We also present optical long-slit spectroscopy to determine the [NII]/H{alpha} intensity ratio of the ionized gas. Dust lanes and/or patches have been detected in 23 galaxies (41%) from this sample using both colour-index images and division by purely elliptical model images. We achieved a detection limit for dust absorption of A_B_ ~ 0.02. Accounting for selection effects, the true fraction of elliptical galaxies containing dust is estimated to be of order 80%. This detection rate is comparable to that of the IRAS satellite, and significantly larger than results of previous optical studies. Ionized gas has been detected in 32 galaxies (57%). The spectroscopic data confirm the presence and distribution of ionized gas as seen in the direct imaging. All elliptical galaxies in our sample in which a number of emission lines is detected show very similar emission-line intensity ratios, which are typical of LINER nuclei. The amounts of detectable dust and ionized gas are generally small-of order 10^4^ - 10^5^ M_sun_ of dust and 10^3^ - 10^4^ M_sun_ of ionized gas. The dust and ionized gas show a wide variety of distributions-extended along either the apparent major axis, or the minor axis, or a skewed axis, indicating that triaxiality is in general required as a galaxy figure. In some cases (NGC 1275, NGC 2325, NGC 3136, NGC 3962, NGC 4696, NGC 5018, NGC 5044, NGC 5813, IC 1459) the interstellar matter has a patchy or filamentary distribution, suggestive of a recent interaction event. The distributions of dust and ionized gas are consistent with being physically associated with each other. Key words: galaxies: elliptical - elliptical galaxies: interstellar matter, photometry, structure
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