Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apjs...91...79h&link_type=abstract
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 91, no. 1, p. 79-110
Astronomy and Astrophysics
Astronomy
44
Astronomical Models, Brightness, Brightness Distribution, Galactic Structure, H I Regions, H Ii Regions, Ionized Gases, Luminosity, Plasmas (Physics), Radio Sources (Astronomy), Charge Coupled Devices, H Alpha Line, Images, Interferometry, Iue, Radio Astronomy, Spectrographs, Very Large Array (Vla)
Scientific paper
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 full width at half maximum (FWHM) less than or equal to 140 km/s, 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 1011 solar mass at 3.3 Holmberg radii (RH). NGC 1800 has a hook that coincides with a large H II region, and an r1/4 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 approximately 750 pc long. About 2.3 kpc to the north is a web of filaments approximately 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 approximately 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.
Gallagher John S. III
Hunter Deidre Ann
van Woerden Hugo
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