Feedback in Galaxy Clusters and Brightest Cluster Galaxy Star Formation

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 filamentary structures extending several tens of kpc. I initially focus on these structures, which harbor starbursts forming stars at rates between < 1 M_sun yr^-1 and ~250 M_sun yr^-1. I perform ultraviolet through far-infrared Spectral Energy Distribution (SED) fitting on combined Hubble, Spitzer, and Herschel photometry of 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

System Modeling and Traceability Applications of the Higraph Formalism

One of the most important tools for a systems engineer is their system model. From this model, engineering decisions can be made without costly integration, fabrication, or installations. Existing system modeling languages used to create the system model are detailed and comprehensive, but lack a true ability to unify the system model by showing all relationships among all components in the model. Higraphs, a type of mathematical graph, allow systems engineers to not only represent all required information in a system model, but to formally show all relationships in the model through hierarchies, edges, and orthogonalities. With a higraph system model, all relationships between system requirements, components, and behaviors are formalized allowing for a "smart" model that can be queried for custom sets of information that, when presented to the systems engineer, will aid in engineering decisions

Modulation of hexokinase association with mitochondria analyzed with quantitative three-dimensional confocal microscopy

Hexokinase isozyme I is proposed to be associated with mitochondria in vivo. Moreover, it has been suggested that this association is modulated in coordination with changes in cell metabolic state. To test these hypotheses, we analyzed the subcellular distribution of hexokinase relative to mitochondria in paraformaldehyde-fixed astrocytes using immunocytochemistry and quantitative three-dimensional confocal microscopy. Analysis of the extent of colocalization between hexokinase and mitochondria revealed that approximately 70% of cellular hexokinase is associated with mitochondria under basal metabolic conditions. In contrast to the immunocytochemical studies, between 15 to 40% of cellular hexokinase was found to be associated with mitochondria after fractionation of astrocyte cultures depending on the exact fractionation conditions. The discrepancy between fractionation studies and those based on imaging of distributions in fixed cells indicates the usefulness of using techniques that can evaluate the distributions of cytosolic enzymes in cells whose subcellular ultrastructure is not severely disrupted. To determine if hexokinase distribution is modulated in concert with changes in cell metabolism, the localization of hexokinase with mitochondria was evaluated after inhibition of glucose metabolism with 2-deoxyglucose. After incubation with 2-deoxyglucose there was an approximate 35% decrease in the amount of hexokinase associated with mitochondria. These findings support the hypothesis that hexokinase is bound to mitochondria in rat brain astrocytes in vivo, and that this association is sensitive to cell metabolic state

Developing a Visitor Profile: The Hill of Tara for Hill of Tara Conservation Management Plan

A Conservation Management Plan for the State-owned lands at the Hill of Tara was commissioned by the Minister for Culture, Heritage and the Gaeltacht in January 2018. As an element of this at the request of the Heritage Council and the Discovery Programme, a visitor profile was undertaken by staff and students of the School of Hospitality Management and Tourism, Dublin Institute of Technology (DIT). According to the Office of Public Works (OPW), over 200,000 people visit Tara archaeological site each year, and the site is being actively promoted as part of the Ireland’s Ancient East brand by Fáilte Ireland. As part of the Conservation Management Plan consideration is required as to how the site should be managed in the future, and a visitor profile is the first step in identifying aspects of visitation to the site. The objective of the research work was to develop a visitor profile of the Tara archaeological site in County Meath. The survey was administered to visitors to the Hill of Tara over one day, 18 July 2018. The survey was administered by three volunteer students from the BA in Tourism Management (DT406), DIT, facilitated by Dr. Catherine Gorman. These students were informed of the survey and were offered an opportunity to volunteer to undertake the wor

The Dust and Molecular Gas in the Brightest Cluster Galaxy in MACS 1931.8-2635

We present new ALMA observations of the molecular gas and far-infrared continuum around the brightest cluster galaxy (BCG) in the cool-core cluster MACS 1931.8-2635. Our observations reveal $1.9 \pm 0.3 \times 10^{10}$ M$_{\odot}$ of molecular gas, on par with the largest known reservoirs of cold gas in a cluster core. We detect CO(1-0), CO(3-2), and CO(4-3) emission from both diffuse and compact molecular gas components that extend from the BCG center out to $\sim30$ kpc to the northwest, tracing the UV knots and H$\alpha$ filaments observed by HST. Due to the lack of morphological symmetry, we hypothesize that the $\sim300$ km s$^{-1}$ velocity of the CO in the tail is not due to concurrent uplift by AGN jets, rather we may be observing the aftermath of a recent AGN outburst. The CO spectral line energy distribution suggests that molecular gas excitation is influenced by processes related to both star formation and recent AGN feedback. Continuum emission in Bands 6 and 7 arises from dust and is spatially coincident with young stars and nebular emission observed in the UV and optical. We constrain the temperature of several dust clumps to be $\lesssim 10$ K, which is too cold to be directly interacting with the surrounding $\sim 4.8$ keV intracluster medium (ICM). The cold dust population extends beyond the observed CO emission and must either be protected from interacting with the ICM or be surrounded by local volumes of ICM that are several keV colder than observed by Chandra.Comment: Accepted for Publication in ApJ, 19 pages, 11 figures. Minor revisions to the discussion and accompanying figur