NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2018-12-11 T02:54:07 PST
Help | Comment | NED Home

For refcode 1994ApJS...91...79H:
Retrieve 43 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
1994ApJS...91...79H NEUTRAL HYDROGEN AND OPTICAL PROPERTIES OF THREE AMORPHOUS GALAXIES DEIDRE A. HUNTER Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 HUGO VAN WOERDEN Kapteyn Astronomical Institute, Postbus 800, NL-9700 Groningen, The Netherlands AND JOHNS. GALLAGHER III Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 Received 1993 April 12; accepted 1993 July 15 ABSTRACT We present new interferometric H I and optical observations of three amorphous galaxies, systems with a smooth, high surface brightness but an asymmetrical distribution of light. All three galaxies are forming stars and have LMC-like emission-line ratios, low dust content, and high H I velocity dispersions. NGC 1140 has a boxy inner morphology with a hook off one corner. At low light levels unusual extensions of starlight are seen curving to the northwest and southeast. The galaxy contains a very luminous central star-forming region and a small chain of H II regions that coincide with the hook. The central H II region has broad H{alpha} velocity profiles (FWHM <= 140 km s^-1^), and it is a radio continuum source. There is a rotating H I gas disk, 40 kpc in radius, at a position angle 51^deg^ from the optical major axis. The central gas ridge follows the chain of H II regions, and the H I peak is on the hook. The outer gas on the southeast side curves away from the H I major axis. The central gas density is high, and the surface density declines very slowly with radius. The rotation velocity yields a mass of 1 x 10^11^ M_sun_ at 3.3 Holmberg radii (R_H_). NGC 1800 has a hook that coincides with a large H II region, and an r^1/4^ luminosity distribution. There are numerous H II regions along the major axis and extraordinary filaments of ionized gas. Emanating from the major axis on either side of the galaxy are H{alpha} fingers ~750 pc long. About 2.3 kpc to the north is a web of filaments ~3 kpc in extent. H{alpha} profiles of H II regions and filaments are narrow. The H I gas disk has a position angle that is ~13^deg^ different from that of the optical axis. There are two peaks near the center, one of which is near the largest H II region. Beyond the Holmberg radius to the west is a 6 x 10^6^ M_sun_ H I cloud. Its velocity indicates a mass of ~6 X 10^9^ M_sun_ for NGC 1800 at 1.5R_H_. At ~R_25_ to the east there is a large HI shell. Also, at ~R_25_ on both sides the velocity gradient switches by 90^deg^, and in the interior the rotation is about the major axis. The central gas density is low and falls off slowly. In the inner regions NGC 4670 resembles an SO/a galaxy seen rather edge-on. It contains a central supergiant H II region with very high velocity widths (FWHM <= 180 km s^-1^) and complex velocity structures. It is a radio continuum source as well. The H I gas is a single spherical cloud or a disk at low inclination centered on the galaxy with a slight elongation along the optical major axis and rotation about the minor axis. The central gas density is high, and there is a high degree of concentration. The rotation speed indicates a total mass of 5 X 10^10^ M_sun_ at 1.1 R_H_. We compare these characteristics with properties of gas in the presence of stellar bar potentials, gas warps, and interacting and merging galaxy models. Although there are inconsistencies and uncertainties, we conclude that NGC 1140 is a spiral of low surface brightness that has undergone a merger, while NGC 1800 and NGC 4670 are, respectively, probably an Im system and a spiral that had an encounter of the Noguchi (1988a) kind. Subject headings: galaxies: structure - radio lines: galaxies
Retrieve 43 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home