H I Imaging Observations of Superthin Galaxies. II. IC 2233 and the Blue Compact Dwarf NGC 2537

• Published in: The Astronomical journal Vol. 135; no. 1; pp. 291 - 318
• Main Authors: Matthews, Lynn D, Uson, Juan M
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 01.01.2008
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; COLOR; DWARF STARS; GALAXIES; GIANT STARS; OPTICAL PROPERTIES; ORGANOLEPTIC PROPERTIES; PHYSICAL PROPERTIES; STARS; SUPERGIANT STARS
• ISSN: 1538-3881; 0004-6256; 1538-3881
• DOI: 10.1088/0004-6256/135/1/291

We have used the Very Large Array to image the H I 21 cm line emission in the edge-on Sd galaxy IC 2233 and the blue compact dwarf NGC 2537. We also present new optical B, R, and H{alpha} imaging of IC 2233 obtained with the WIYN telescope. Despite evidence of localized massive star formation in the form of prominent H II regions and shells, supergiant stars, and a blue integrated color, IC 2233 is a low surface brightness system with a very low global star formation rate ({approx}<0.05 M{sub sun} yr{sup -1}), and we detect no significant 21 cm radio continuum emission from the galaxy. The H I and ionized gas disks of IC 2233 are clumpy and vertically distended, with scale heights comparable to that of the young stellar disk. Both the stellar and H I disks of IC 2233 appear flared, and we also find a vertically extended, rotationally anomalous component of H I extending to {approx} 2.4d{sub 10} kpc from the midplane. The H I disk exhibits a mild lopsidedness as well as a global corrugation pattern with a period of {approx}7d{sub 10} kpc and an amplitude of {approx}150d{sub 10} pc. To our knowledge, this is the first time corrugations of the gas disk have been reported in an external galaxy; these undulations may be linked to bending instabilities or to underlying spiral structure and suggest that the disk is largely self-gravitating. Lying at a projected distance of 16'.7 from IC 2233, NGC 2537 has an H I disk with a bright, tilted inner ring and a flocculent, dynamically cold outer region that extends to {approx}3.5 times the extent of the stellar light (D{sub 25}). Although NGC 2537 is rotationally-dominated, we measure H I velocity dispersions as high as {sigma}{sub V.HI}{approx}25 km s{sup -1} near its center, indicative of significant turbulent motions. The inner rotation curve rises steeply, implying a strong central mass concentration. Our data indicate that IC 2233 and NGC 2537 do not constitute a bound pair and most likely lie at different distances. We also find no compelling evidence of a recent minor merger in either IC 2233 or NGC 2537, suggesting that both are examples of small disk galaxies evolving in relative isolation.