Computer Science
Scientific paper
Aug 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007phdt........18r&link_type=abstract
Proquest Dissertations And Theses 2007. Section 0167, Part 0606 172 pages; [Ph.D. dissertation].United States -- Ohio: Ohio Uni
Computer Science
Cluster Cores, Intracluster Medium, Active Galactic Nuclei, Cooling Flows, Black Holes
Scientific paper
We present an analysis of star formation, cooling, and feedback in 61 galaxies at the cores of galaxy clusters. A subsample of 33 of these systems possesses cavities in the intracluster medium (ICM) inflated by radio jets emanating from their active galactic nuclei (AGN). We present an extensive analysis of the X- ray cavities in these systems. We find that AGN, through their cavities alone, are energetically able to balance radiative losses (cooling) from the ICM in more than half of these systems. Using the cavity (jet) powers, we place strong lower limits on the rate of growth of supermassive black holes in central galaxies, and we find that they are growing at an average rate of ~0.1 [Special characters omitted.] yr -1 , with some systems growing as quickly as ~1 [Special characters omitted.] yr -1 . We find a trend between bulge growth (star formation) and black hole growth that is approximately in accordance with the slope of the local (Magorrian) relation between black hole and bulge mass. However, the large scatter in the trend suggests that bulges and black holes do not always grow in lock step. With the exception of the rapidly accreting supercavity systems (e.g., MS 0735.6+7421), the black holes are accreting well below their Eddington rates. Most systems could be powered by Bondi accretion from the hot ICM, provided the central gas density increases into the Bondi radius as r 0( r -1 . However, if the gas density profile flattens into a core, as observed in M87, Bondi accretion is unlikely to be driving the most powerful outbursts.
Using a subsample of 17 systems with published star formation rates, we examine the relationship between cooling and star formation. We find that the star formation rates are approaching or are comparable to X-ray and far-UV limits on the rates of gas condensation onto the central galaxy. The remaining radiative losses could be offset by AGN feedback. The vast gulf between radiative losses and the sink of cooling material, which has been the primary objection to cooling flows, has narrowed and, in some cases, is no longer a serious issue. Lastly, for a subsample of 40 systems, we use broadband optical imaging to measure the U - I and U - R colors in the galaxies at the cores of the clusters. By comparing the optical properties to the X-ray-derived properties on similar spatial scales, we find that blue colors, indicative of recent star formation, occur only in clusters for which the central X-ray-emitting gas has cooling times less than ~7 × 10 8 yr (or entropies of less than ~30 keV cm 2 ), whereas red central colors occur over a wide range of cooling times.
Taken together, these findings represent compelling evidence for AGN feedback in massive halos.
No associations
LandOfFree
Feedback in cluster cores does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Feedback in cluster cores, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Feedback in cluster cores will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1799304