Astrophys. J., 715, 172-185 (2010/May-3)
Episodic star formation coupled to reignition of radio activity in 3C 236.
TREMBLAY G.R., O'DEA C.P., BAUM S.A., KOEKEMOER A.M., SPARKS W.B., DE BRUYN G. and SCHOENMAKERS A.P.
Abstract (from CDS):
We present Hubble Space Telescope Advanced Camera for Surveys and STIS FUV/NUV/optical imaging of the radio galaxy 3C 236, whose relic ∼4 Mpc radio jet lobes and inner 2 kpc compact steep spectrum (CSS) radio source are evidence of multiple epochs of active galactic nucleus (AGN) activity. Consistent with previous results, our data confirm the presence of four bright knots of FUV emission in an arc along the edge of the inner circumnuclear dust disk in the galaxy's nucleus, as well as FUV emission cospatial with the nucleus itself. We interpret these to be sites of recent or ongoing star formation. We present photometry of these knots, as well as an estimate for the internal extinction in the source using line ratios from archival ground-based spectroscopy. We estimate the ages of the knots by comparing our extinction-corrected photometry with stellar population synthesis models. We find the four knots cospatial with the dusty disk to be young, of order ∼107 yr old. The FUV emission in the nucleus, to which we do not expect scattered light from the AGN to contribute significantly, is likely due to an episode of star formation triggered ∼109 yr ago. We argue that the young ∼107 yr old knots stem from an episode of star formation that was roughly coeval with the event resulting in reignition of radio activity, creating the CSS source. The ∼109 yr old stars in the nucleus may be associated with the previous epoch of radio activity that generated the 4 Mpc relic source, before being cut off by exhaustion or interruption. The ages of the knots, considered in the context of both the disturbed morphology of the nuclear dust and the double-double morphology of the "old" and "young" radio sources, present evidence for an AGN/starburst connection that is possibly episodic in nature. We suggest that the AGN fuel supply was interrupted for ∼107 yr due to a minor merger event and has now been restored. The resultant nonsteady flow of gas in the disk is likely responsible for both the new episode of infall-induced star formation and also the multiple epochs of radio activity.
galaxies: active - galaxies: individual: 3C 236 - galaxies: jets - galaxies: starburst
View the reference in ADS
To bookmark this query, right click on this link: simbad:2010ApJ...715..172T and select 'bookmark this link' or equivalent in the popup menu