Feedback in Galaxy Clusters and Brightest Cluster Galaxy Star Formation

[摘要] My main thesis work is to understand the relationship between star formation in the brightest cluster galaxy (BCG) and the thermodynamical state of the intracluster medium (ICM) of cool core galaxy clusters. Detailed photometry of BCGs in galaxy clusters observed in the Cluster Lensing and Supernova survey with Hubble (CLASH) reveal ultraviolet and H-alpha emitting knot and filamentarystructures extending several tens of kpc. I initially focus on these structures, which harbor starbursts forming stars at rates between < 1 M_sunyr^-1 and ~250 M_sunyr^-1. I perform ultraviolet through far-infrared Spectral Energy Distribution (SED) fitting on combined Hubble, Spitzer, and Herschel photometryof CLASH BCGs, and measure star formation rates (SFRs), dust contents, and constrain the duration of starburst activity. Using X-ray data from Chandra, I find a tight relationship between CLASH BCG SFRs and the cooling-to-freefall time ratio in the ICM. I propose treating the cooling-to-freefall time ratio as a proxy for the mass condensation efficiency of the ICM in the core of cool-core clusters, an interpretation which is motivated by recent theoretical work describing feedback regulated condensation and precipitation of the ICM in cool core clusters. I follow up this work by performing similar SED fitting on a larger sample of clusters observed in the Cosmic Evolution Survey (COSMOS). I examine the evolution of star formation in BCGs and discuss the impact of cluster environment on BCG specific SFRs.Besides this work, I have developed the polynomial apodized vortex coronagraph (PAVC). I describe the performance of this theoretical coronagraph design, which restores ideal starlight suppression to the vortex coronagraph in the presence of centrally obstructed telescope pupils. The PAVC offers substantial gains in throughput relative to other designs that optimize vortex coronagraphs for obstructed pupils, and can be combined with active correction techniques to account for pupils with both central obstructions and obstructions due to support structures, segment gaps, or defects.

[发布机构] Johns Hopkins University

[效力级别] Star Formation

[关键词] Galaxy Clusters;Star Formation;Physics