Daily Image
17-09-2009
An unequal pair
| Submitter: | Nancy Irisarri |
| Description: | Dwarf irregular galaxies are small disk galaxies. Because they do not contain many stars, and hence not much mass in their disks, they are well suited to study the structure of their unseen component, the Dark Matter halo. In the past few weeks, summer student Nancy Irisarri and her supervisor Gyula Józsa had a look at two particular dwarf galaxies. KKH 11 and UGC 5846 had been selected for an observation because they contain more mass in neutral hydrogen than in stars. Such systems promise to have a very extended gas disk compared to the optical one, such that the mass distribution of the galaxy can be traced via line observations out to large radii where their dynamics is completely dominated by Dark Matter. Indeed both systems have very large gas disks. For KKH 11 we could establish a very reliable kinematical model, allowing us to trace the potential out to a radius where the mass enclosed is about 50 times higher than the galaxy’s content in stars. On the image we show the WSRT image of the neutral gas disk overlaid with the velocity field (blue contours), which characterises the kinematics of the system. A tilted-ring model (image on the top) that has been derived to quantify the kinematics matches the observations well. For UGC 5846, with its very irregular distribution of the neutral hydrogen, we could not establish a reliable tilted-ring model. While we will use our results to establish a model of the Dark Matter distribution in KKH 11, our data taken of UGC 5846 will enable us to study in detail the interaction of the stars and the gas in that galaxy. |
| Copyright: | Astron |
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