We present and analyse HST/WFPC2 broad- and narrow-band observations of the central regions of 19 nearby radio-loud early-type galaxies. Together with two more galaxies they form a complete sample of Fanaroff & Riley Type I galaxies. We obtained V - and I-band images and narrow-band images centered on the H-alpha+[NII] emission lines. We use archival data for six galaxies. We describe the data reduction, give isophotal fits and analyse the central emission-line gas and dust distributions. Our main conclusions are the following. Although obscuration by dust inhibits a direct determination of central cusp slopes, the data suggest most but not all galaxies have shallow cores. Dust is detected in all but two galaxies. There is a wide variety of central dust morphologies, ranging from central disks to lanes and irregular distributions. The analysis suggests the difference between disks and lanes is intrinsic and not due to different viewing angles. Central emission-line gas is detected in all galaxies. Extended low-surface-brightness emission is always associated with the dust features. In a subsequent paper we will present a detailed analysis of the relation between these central properties and the nuclear activity (Refer to PDF file for exact formulas).

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Also archived in: arXiv: astro-ph/9909256 v1 15 Sep 1999 Support for this work was provided by NASA through grant number #GO-06673.01-95A from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. TdZ gratefully acknowledges the warm hospitality of STScI. The authors would like to thank Roeland van der Marel and Marcella Carollo for helpful discussions and a critical reading of the manuscript, and the referee for helpful suggestions to improve the manuscript.ISSN:1538-3881 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus