Date of Award

Spring 5-16-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Physics & Astronomy

First Advisor

Mark Devlin

Abstract

The Multiplexed SQUID/TES Array at Ninety Gigahertz (MUSTANG) is a bolometric continuum imaging camera designed to operate at the Gregorian focus of the 100m Green Bank Telescope (GBT) in Pocahontas county, West Virginia. The combination of the GBT's large collecting area and the 8x8 array of transition edge sensors at the heart of MUSTANG allows for deep imaging at 10'' resolution at 90GHz. The MUSTANG receiver is now a facility instrument of the National Radio Astronomy Observatory available to the general astronomical community.

The 3.3mm continuum passband is useful to access a large range of Galactic and extra-Galactic astrophysics. Sources with synchrotron, free-free and thermal blackbody emission can be detected at 3.3mm. Of particular interest is the Sunyaev Zel'dovich effect in clusters of galaxies, which arises from the inverse Compton scattering of CMB photons off hot electrons in the intra-cluster medium. In the MUSTANG band, the effect is observationally manifested as an artificial decrement in power on the sky in the direction of the cluster. There have been many experiments in the past two decades dedicated to measurements of the SZE, however, nearly all of them were accomplished with angular resolution larger than ~1'. The massive primary of the GBT enables measurements of the SZE on 10'' scales. This provides a new technique to map pressure substructure in the plasma atmospheres of merging clusters of galaxies. By analyzing MUSTANG data along side X-ray data, spatially resolved measurements of the temperature, density and pressure of the ICM can be performed which can be used to infer the physics governing major mergers.

This thesis details the design, commissioning and operation of the various components which comprise the MUSTANG receiver. This includes the sub-kelvin cryogenic cooling, the time domain multiplexed readout electronics and the array of transition edge sensor bolometers. Laboratory characterization of the detector array is thoroughly described, including the measurements of the transition temperatures, thermal conductance, noise properties and time constants.

Bolometric cameras measure celestial radiation as time ordered data. To reliably produce images from traces in the time domain, care must be taken to modulate the signal in an optimized fashion during observations. Once the data are taken, algorithms must be developed to isolate the signal of interest from the foregrounds produced by atmospheric emission.

This thesis presents the techniques developed to scan, calibrate, filter and produce images from time ordered data taken with MUSTANG and the GBT.

From the Fall of 2006 to the winter of 2010, the MUSTANG receiver was commissioned on the GBT and used for a range of astrophysical measurements. The commissioning process and early science results are given in this thesis. This includes the modifications made to the instrument which have resulted in dramatically enhanced sensitivity as well as the images produced from bright extended millimeter sources such as high mass star forming regions, active galactic nuclei and supernova remnants.

This thesis presents a sample of merging clusters of galaxies imaged through their Sunyaev Zel'dovich signatures at high angular resolution. In the massive cluster RXJ1347, a previously reported pressure enhancement to the south east of the cluster peak was confirmed. This is now interpreted as a parcel of hot shock heated gas (KT~20keV) produced in a recent merger. In the high redshift systems MACS0744 and CL1226, pressure substructure was identified and is believed to be associated with merger activity. Both systems contain peaks in dark matter revealed by gravitational lensing which are not associated with baryonic emission, supportive of a scenario in which an infalling cluster has passed through a main cluster being stripped of its baryons. In MACS0744, the SZE and X-ray morphology is suggestive of a shock wave propagating through the ICM. By fitting the Rankine Hugoniot jump conditions in a simultaneous SZE/X-ray analysis, the likelihood of this interpretation is explored. The system is well described by a mildly supersonic shock wave propagating with a Mach number of ~1.2.

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