Hi gas and stellar content of early-type galaxies

✍ Scribed by P. Serra; S.C. Trager; J.M. van der Hulst; T.A. Oosterloo; R. Morganti; J.H. van Gorkom; E.M. Sadler

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 551 KB
• Volume: 51
• Category: Article
• ISSN: 1387-6473
• DOI: 10.1016/j.newar.2006.11.009

✦ Synopsis

We present Australian telescope compact array observations of the neutral-hydrogen gas in 42 early-type galaxies detected by the HIPASS survey. We confirm the detection of 18 galaxies with HI mass between a few times 10 9 and $10 10 M x and column density below a few times 10 20 cm À2 . Most of the confirmed detections show disk-or ring-like HI distribution with regular morphology and rotation. These HI-rich galaxies could have formed via either a HI-rich merger event or smooth accretion of gas from the intergalactic medium. As a part of a larger project, we present the results of optical spectroscopy and imaging and deeper 21 cm wavelength observations of one of the HI-rich galaxies, IC 4200, performed in order to distinguish between the two formation processes. We find that the galaxy hosts 8.5 • 10 9 M x of HI rotating on a $90°warped disk extended out to 60 kpc from the centre of the galaxy. Optical spectroscopy reveals a simple-stellar-population-equivalent age of 1.5 Gyr in the centre of the galaxy, and V-and R-band images show stellar shells. We interpret these observational results as evidence for a major merger origin of IC 4200, and date the merger back to 1-3 Gyr ago.