We report the discovery of an ultraviolet lament detected in a new Space Telescope Imaging Spectrograph (STIS) NUV-MAMA image of the cD galaxy UGC 9799, located in the cooling-flow cluster Abell 2052 and host to the radio source 3C 317. The lament is similar to2 kpc in length and is located at a distance of similar to4 kpc from the nucleus along a north-south axis. It consists of three knots embedded along the edges of a diffuse filamentary halo. The northern half of the lament is narrow (similar to100 pc) and straight while the southern half is bent and more diffuse. The blue color (NUV-V approximate to -2.4) and morphology of the lament are most consistent with a recent episode of star formation (T approximate to 5 Myr). Only a few x 10(4) M-circle dot of young stars or a star formation rate of approximate to10(-3) M-circle dot yr(-1) is required to produce the feature. A steep ultraviolet halo is detected around the unresolved nucleus, and it may be associated with an old stellar component. No ultraviolet features are identified at the location of the extended emission-line nebulae observed from the ground, indicating that OB stars are not the primary source of ionization in these regions. We consider cooling flows and a merger with a satellite galaxy the trigger for the starburst regions and conclude that the latter is the more consistent with the chaotic dust lanes spread throughout the host galaxy. The star formation observed is orders of magnitude less than the inferred cooling rate in the cooling flow scenario. References: 39
展开▼
