High Resolution SZE Measurements of Galaxy Clusters with MUSTANG
My thesis is focused on high resolution Sunyaev-Zel'dovich Effect (SZE) measurements of galaxy clusters. To do my research, I use the Green Bank Telescope (GBT), which has on board a bolomoter array, MUSTANG, whose resolution is 9\" FWHM. The core of the thesis will be analyzing (galaxy) cluster (electron) pressure profiles. Although pressure profiles have been measured before, X-ray data was used, which not directly sensitive to (integrated) electron pressure, as the SZE is. Pressure profiles are of interest since equations of hydrostatic equilibrium (HSE) lets one calculate enclosed mass from the slope of the pressure profile.
In addition to determining cluster pressure profiles, I will examine the impact that cluster substructure (as seen in the SZE) has on cluster scaling relations. The principle relation is the M-Y relation, which relates cluster mass and integrated compton y parameters. Characterization of this scatter could lead to better constraints on cosmology, and is poised to help significantly with the ongoing SZE surveys. A significant advantage that SZE observations have over any other observations of galaxy clusters is that the SZE is redshift independent, and we have already seen new cluster detections from SZE observations.
In order to do both of the above analyses, I am working on code that can quantitatively fit models (of galaxy clusters) to the data. To do this, I will be using a linear least-squares approach. To do this correctly requires a solid understanding of the noise characteristics of our data, especially in the face of subtracting out systematic noises. (Our signal is buried in the noise, and to recover the signal, we effectively end up stacking the data.)
Once the model fitting code is working, it will be applicable to any cluster where a viable model is available. This includes those relaxed clusters where a pressure profile is meaningful (i.e. does not looked distrubed, and we can reasonably assume HSE. Additional features that may be modelled include helium sedimentation and shocks with clean geometry (propogation is in the plane of the sky). For any cluster observation, there is the potential for point sources (potentially AGN) close to the cluster, especially considering brightest cluster galaxies (BCGs) are more likely that other cluster galaxies to emit at 90 GHz. Since point sources can be modelled without too much difficulty, the fitting code will allow simultaneous fits for point source and cluster models.
Another portion of my thesis will be to do some hardware work on the next generation receiver: MUSTANG-2. As it stands, our collaboration has garnered enough funds for what we have deemed MUSTANG-1.5 which has all the housing components of MUSTANG-2, but will not have the full population of detectors. MUSTANG-2 will provided over a factor of 10 gain in sensitivity, especially when considering the greater field of view, thus mapping speeds (times) will be dramatically improved (reduced).