Superthin Galaxies Research Articles

HiImaging Observations of Superthin Galaxies. I. UGC 7321

We have used the Very Large Array to image the isolated superthin galaxy UGC 7321 in the H I line with a spatial resolution of 16'' and a spectral resolution of 24 kHz (5.2 km s-1). We have reached a sensitivity of (0.36–0.40) mJy beam-1 channel-1, which correspond to a column density of (8–9) × 1018 atoms cm-2 (1 σ). UGC 7321 has a gas-rich disk, with MH I = (1.06 ± 0.01) × 109 d M⊙ and MH I/LB = 1.0 (d10 is the distance to UGC 7321 in units of 10 Mpc, the value adopted in this paper), and no detectable radio continuum emission (FCONT = 0.41 ± 0.25 mJy). The global H I distribution of UGC 7321 is rather symmetric and extends to ~1.5 times the optical radius (DH I = 865 ± 015 at nH I = 3 × 1019 atoms cm-2). An integral sign warp is observed in the H I disk, commencing near the edge of the stellar distribution and twisting back toward the equatorial plane in the outermost regions. In addition, the position-velocity diagram suggests the presence of a bar or inner arm within ~40'' from the center. The rotation curve of UGC 7321 is slowly rising; it reaches its asymptotic velocity of ~110 km s-1 at ~25 from the center (about 0.9 optical radii) and declines near the edge of the H I disk. The ratio of the inferred dynamical mass to the mass in gas and stars is ~12d, implying that UGC 7321 is a highly dark-matter–dominated galaxy.

The Extraordinary “Superthin” Spiral Galaxy UGC 7321. II. The Vertical Disk Structure

We explore the vertical light distribution as a function of galactocentric radius in the edge-on (i = 88°) Sd superthin galaxy UGC 7321. UGC 7321 is a low-luminosity spiral (MB,i = -17.0) with a diffuse, low surface brightness stellar disk and no discernible bulge component. Within ~ 025 (~725 pc) of the disk center the global luminosity profile of UGC 7321 can be reasonably characterized by an exponential function with a scale height hz ~ 29 (~140 pc) in H and hz ~ 31 (~150 pc) in R, making this among the thinnest galaxy disks known. Near the disk center we derive a ratio of disk scale length to global disk scale height hr/hz ~ 14 in both H and R; near the edge of the disk, hr/hz ~ 10. At intermediate galactocentric radii (025 ≤ |r| ≤ 15), the disk of UGC 7321 becomes less peaked than an exponential near the galactic plane. At these radii the vertical luminosity profiles can be well reproduced by a linear combination of two isothermal disk components of differing scale heights. These fits, together with the strong disk color gradients by Matthews, Gallagher, & van Driel, suggest that UGC 7321 has multiple disk subcomponents comprised of stellar populations with different ages and velocity dispersions. Thus even examples of the thinnest pure disk galaxies exhibit complex structure and signatures of dynamical heating.

Spectroscopic observations of superthin galaxies

view Abstract Citations (91) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic observations of superthin galaxies. Goad, J. W. ; Roberts, M. S. Abstract Spectroscopic observations of the superthin galaxies UGC 4278, 7170, 7321, and 9242 with 4 and 2.1 m telescopes, are reported to demonstrate how the morphology, kinematics and line ratios of a superthin galaxy may be interrelated. Comparisons are also made with two related edge-on systems. The superthin galaxies are characterized by modest central velocity gradients, an underabundance of nitrogen, and very thin disks with little evidence of a central luminosity concentration. The mean H I content is roughly 10% of the estimated match, which is a value close to the mean for late-type Sd spirals, and large-scale galactic shocks may be nonexistent in the disks due to the modest central concentration of mass. Publication: The Astrophysical Journal Pub Date: November 1981 DOI: 10.1086/159349 Bibcode: 1981ApJ...250...79G Keywords: Abundance; Astronomical Spectroscopy; Disk Galaxies; Galactic Structure; Spiral Galaxies; Galactic Rotation; Hydrogen Atoms; Luminous Intensity; Nitrogen; Shock Waves; Astrophysics full text sources ADS | data products SIMBAD (18) NED (14)