The distribution of warm ionized gas in NGC 891

Abstract

view Abstract Citations (238) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Distribution of Warm Ionized Gas in NGC 891 Rand, Richard J. ; Kulkarni, Shrinivas R. ; Hester, J. Jeff Abstract We present narrow-band imaging of the edge-on spiral NGC 891 in the Hα and [S II] λλ6717, 6731 lines. Emission from H II regions confined to the plane of the galaxy and from diffuse gas up to about 4 kpc off the plane is readily detected. The full radial extent of the diffuse emission in the plane is about 30 kpc. The [S II]/Hα ratio is quite uniform in the halo and is significantly higher in the halo than in the disk-consistent with observations of the diffuse ionized gas in our Galaxy. NGC 891 is found to have a surface density of diffuse ionized gas twice the Galactic value, a thicker ionized gas layer, and a larger surface density of ionized gas relative to neutral gas. We interpret these to be consequences of a relatively high level of star formation in this galaxy. Other star formation tracers indicate the same conclusion. We see many vertical Hα filaments, or "worms," extending to > 2 kpc off the plane of the galaxy. These worms are interpreted in terms of chimney models for the interstellar media of spirals. We also see several "supershells" which are centered up to 1400 pc above the plane. The highest z emission could be due to gas accelerated into the halo by chimneys, but reionization of this gas by another galactic source is probably required. The intergalactic EUV ionizing flux is insufficient to maintain the high-z ionization. Publication: The Astrophysical Journal Pub Date: March 1990 DOI: 10.1086/185679 Bibcode: 1990ApJ...352L...1R Keywords: Interstellar Gas; Ion Distribution; Ionized Gases; Line Spectra; Spiral Galaxies; Star Formation; Galactic Radiation; H Alpha Line; H Ii Regions; Halos; Milky Way Galaxy; Astrophysics; GALAXIES: INTERSTELLAR MATTER; STARS: FORMATION full text sources ADS | data products SIMBAD (1) NED (1) Related Materials (1) Erratum: 1990ApJ...362L..35R