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Session 110 - Imaging of Cluster Galaxies.
Display session, Thursday, January 18
North Banquet Hall, Convention Center
We have obtained U, R and H\alpha images of the centrally dominant galaxy in the Zwicky 3146 cluster using the 4 meter telescope of the Kitt Peak National Observatory. Zwicky 3146 is a distant (z=0.29), X-ray luminous cluster (L_x\simeq 2\times 10^45 erg s^-1) that harbors the largest known cooling flow (\dot m\sim 1200 M_ødot yr^-1) [Allen et al. 1992, MNRAS 259, 67; Edge, et al. 1994, MNRAS, 270, L1]. The central galaxy has an unusually blue optical spectrum and is the most luminous known in optical line emission (L_H\alpha\simeq 10^43 erg s^-1) [Allen et al. 1992].
We find the inner 75 kpc of the central galaxy (H_0=50 km s^-1 Mpc^-1; q_0=0) to be roughly 1.2 magnitudes bluer at U-R than the halo. The H\alpha emission is extended over a similar region of the galaxy. The bluest regions are located in two features oriented north-south straddling the nucleus. It is not clear whether the galaxy is intrinsically bluest in these regions or whether this morphology results from reddening by a 40 kpc dust lane bisecting the galaxy. The blue structure, which probably originates from a significant episode of star formation, is morphologically similar to the lobes of optical continuum found along the radio lobes of the central galaxies in the Abell 1795 and Abell 2597 clusters (McNamara amp; O'Connell, 1993, AJ, 105, 417). These clusters also harbor massive cooling flows with cooling rates \sim 300 M_ødot yr^-1. The Zwicky 3146 central galaxy has not been imaged at radio frequencies, so the relationship between its blue optical structure and radio source is unknown.
Program listing for Thursday