Cool Core Disruption Spiral: A spiral of excess intracluster X-ray emission is seen to wind out from the core of galaxy cluster Abell 1763 (Douglass et al. 2018). The system likely responsible for this violent transfer of angular momentum is seen to the southwest. The color image was produced by running the X-ray image through a Gaussian Gradient Magnitude filter which highlights regions where the change in brightness is the steepest. The bright region on the outside of the western edge of the inner spiral indicates its formation originated from a sloshing cool core, however the cool core has been disrupted to the point of non-detection.
Recent Presentations:
Off-Axis Mergers and Cool Core Disruption
Talk presented at 20 Years of Chandra Science Symposium | Boston, MA | Dec 2019
Clusters of Galaxies
The largest gravitationally bound systems the Universe can create are identified in optical observations as clusters of galaxies. When observed with X-ray telescopes, these tightly concentrated collections of galaxies (with member galaxies numbering up to the thousands) are each found to be embedded within a high mass cloud of diffuse, ten million degree gas. This intracluster medium (ICM) generally outweighs the stellar component of the galaxies by a factor of five. The baryonic matter (protons, neutrons) which comprises the stars in the galaxies and gas of the ICM makes up only a fraction of the total gravitating matter of the system. Multiple lines of evidence provided through independent methods of analysis (e.g. dynamical studies of orbiting member galaxies, gravitational lensing surveys, cosmological simulations) show that 90% of the cluster mass is in the form of an electrically neutral halo of particles which neither absorb nor emit light. Their presence is only revealed through the gravitational influence they exert upon their environment. The substance has been termed "dark matter", reflecting both its non-photo-interactive nature and the fact that the its taxonomy has yet to be revealed by way of experiment or observation.
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Clusters of galaxies form through hierarchical assembly of smaller groups of galaxies. Through billions of years of subsystem accretion, clusters grow to attain masses on the order of 10^15 Msun. The ICM, growing in mass at the center of the larger dark matter halo, preserves clues to the clusters’ evolutionary histories as large-scale mergers, lesser accretion events, AGN outbursts, and relaxation all leave observable imprints on the spatial distribution and thermal characteristics of the gas.
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As a diffuse plasma, the ICM emits radiation via Thermal Bremsstrahlung with the amount of energy emitted highly dependent upon the density of the ICM. This results in the dense cores of clusters shining much more brightly than the less dense outskirts. As the gas shines, the emitted radiation carries away with it thermal energy, resulting in a decrease in temperature of the cores of clusters. The overlying gas further compresses the cooling core resulting in additional cooling. These come to be known as cool cores (CCs). This energy loss is ultimately regulated, preventing runaway cooling and starbursting, by reinjection of energy via recurrent outbursts by the supermassive black hole found within the cluster's central dominant galaxy.
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The galaxy cluster population can be divided into those clusters that host CCs at their centers and those that do not (non-cool cores, NCCs). Since a CC should form in a collapsed gas rich halo in the absence of significant energy injection, one can conclude that something must have happened in cores of NCC clusters to have prevented the formation or to have destroyed the already present CC. My research focuses on understanding what it was that transpired in these NCC clusters.
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