Daily Image
14-10-2014
Summer student project: HI in the star forming ring around UGC 9519
| Submitter: | Maolin Zhang |
| Description: | UGC 9519 is a large nearby S0 galaxy with a very faint optical disk, which is also faint in the UV, showing signs of low levels of star formation. Along with galaxies like Hoag's Object (HO) and ESO 381-47, UGC 9519 falls into a special class of early type galaxies surrounded by a star forming ring. The rings in HO and ESO 381-47 host large amounts of HI, so, for my summer student project, I analysed deep observations done for the ATLAS3D project. We had nine (96 hours in total) observation of this galaxy in the 21-cm line of atomic hydrogen with the WSRT. The data were calibrated with MIRIAD. The first image is an optical image with the HI contours overlaid. The lowest contour is about 2x10^19 cm^-2 . From the data cube we obtained we can see a bright ring-like structure that appears to have a fainter, more inclined outer extension. The intensity distribution also shows that there is a central HI component and there is a gap between the central component and the bright ring. We modelled the HI emission using the GIPSY task GALMOD. The HI data cube can be well modelled by using very simple parameters in the model. According to the model, the central component is nearly perpendicular to the bright ring. The second image we show here is the velocity field from the model (black contours) overlaid on the observed velocity field (white contours). From the velocity field we can see that the central HI component is rotating in a very different plane than the bright ring. When we put HI contours on the optical image, we find that star formation occurs exactly in those places where the HI column density is above 3 x 10^20 cm^-2. This means that, despite the very different galaxy setting, the star formation in UGC 9515 behaves exactly as it does in spiral galaxies. Maolin, Zhang, worked on this project as a summer student supervised by Brad Frank and Tom Oosterloo at ASTRON. He is currently doing his Master degree in department of Engineering physics at Tsinghua University in Beijing, China. |
| Copyright: | Zhang, Astron |
| Tweet |  |