Malin 1 - A quiescent disk galaxy

Abstract

view Abstract Citations (155) References (65) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Malin 1: A Quiescent Disk Galaxy Impey, Chris ; Bothun, Greg Abstract We present new optical and radio spectroscopic observations of the remarkable galaxy Malin 1. This galaxy has unique features that include an extremely low surface brightness disk with an enormous mass of neutral hydrogen, and a low-luminosity Seyfert nucleus. Malin 1 is exceptional in its values of M_HI_, L_B_, and M_HI_/L_B_, and modest in its surface mass density of gas and stars. Spirals with large M_HI_/L_B_ tend to have low mean column densities of H I and are close to the threshold for star formation caused by instabilities in a rotating gas disk. In these terms, Malin 1 has a disk with extremely inefficient star formation. The bulge spectrum is dominated by the absorption features of an old, metal-rich stellar population, although there is some evidence for hot (young) stars. The emission line excitations and widths in the nucleus are typical of a Seyfert galaxy; but Malin 1 is in the lowest 5% of the luminosity function of Seyferts, despite a copious fuel supply. Malin 1 is in a low-density region of the universe. We propose it as an unevolving disk galaxy, where the surface mass density is so low that the chemical composition and mass fraction in gas change very slowly over a Hubble time. Its properties are similar to those of the damped Lyα absorption systems seen in the spectra of high-redshift quasars. We emphasize that there are strong observational selection effects against finding gas-rich galaxies that are both massive and diffuse. Finally, we suggest that large and massive H I disks may have formed as early as z ~ 2, and remained quiescent to the present day. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/167474 Bibcode: 1989ApJ...341...89I Keywords: Disk Galaxies; Galactic Evolution; Galactic Nuclei; Radio Astronomy; Seyfert Galaxies; Star Formation; Flux Density; Hubble Constant; Lyman Alpha Radiation; Quasars; Astrophysics; GALAXIES: INDIVIDUAL NAME: MALIN 1; GALAXIES: PHOTOMETRY; GALAXIES: SEYFERT; GALAXIES: STELLAR CONTENT; RADIO SOURCES: 21 CM RADIATION; STARS: FORMATION full text sources ADS | data products SIMBAD (18) NED (15)