Engineering topics

Loh, Michael

Publications and source records attributed to Loh, Michael.

3 records

NASA NTRS2009

Application of a Self-Similar Pressure Profile to Sunyaev-Zeldovich Effect Data from Galaxy Clusters

We investigate the utility of a new, self-similar pressure profile for fitting Sunyaev-Zel'dovich (SZ) effect observations of galaxy clusters. Current SZ imaging instruments-such as the Sunyaev-Zel'dovich Array (SZA)- are capable of probing clusters over a large range in a physical scale. A model is therefore required that can accurately describe a cluster's pressure profile over a broad range of radii from the core of the cluster out to a significant fraction of the virial radius. In the analysis presented here, we fit a radial pressure profile derived from simulations and detailed X-ray analysis of relaxed clusters to SZA observations of three clusters with exceptionally high-quality X-ray data: A1835, A1914, and CL J1226.9+3332. From the joint analysis of the SZ and X-ray data, we derive physical properties such as gas mass, total mass, gas fraction and the intrinsic, integrated Compton y-parameter. We find that parameters derived from the joint fit to the SZ and X-ray data agree well with a detailed, independent X-ray-only analysis of the same clusters. In particular, we find that, when combined with X-ray imaging data, this new pressure profile yields an independent electron radial temperature profile that is in good agreement with spectroscopic X-ray measurements.

Mroczkowski, Tony↗

NASA NTRS2006

Observations of High-Redshift X-Ray Selected Clusters with the Sunyaev-Zel'dovich Array

We report measurements of the Sunyaev-Zel'dovich (SZ) effect in three high redshift (0.89 less than or equal to z less than or equal to 1.03), X-ray selected galaxy clusters. The observations were obtained at 30 GHz during the commissioning period of a new, eight-element interferometer - the Sunyaev-Zel'dovich Array (SZA) - built for dedicated SZ effect observations. The SZA observations are sensitive to angular scales larger than those subtended by the virial radii of the clusters. Assuming isothermality and hydrostatic equilibrium for the intracluster medium, and gas-mass fractions consistent with those for clusters at moderate redshift, we calculate electron temperatures, gas masses, and total cluster masses from the SZ data. The SZ-derived masses, integrated approximately to the virial radii, are 1.9 (sup +0.5)(sub -0.4) x 10(exp 14) solar mass for Cl J1415.1+3612, 3.4 (sup +0.6)(sub -0.5) x 10(exp 14) solar mass for Cl J1429.0+4241 and 7.2 (sup +1.3)(sub -0.9) x 10(exp 14) solar mass for Cl J1226.9+3332. The SZ-derived quantities are in good agreement with the cluster properties derived from X-ray measurements.

Muchovej, Stephen↗

NASA NTRS2006

Observations of High-Redshift X-Ray Selected Clusters with the Sunyaev-Zel'dovich Array

We report measurements of the Sunyaev-Zel'dovich (SZ) effect in three highredshift (0.89 less than or equal to z less than or equal to 1.03), X-ray selected galaxy clusters. The observations were obtained at 30 GHz during the commissioning period of a new, eight-element interferometer - the Sunyaev-Zel dovich Array (SZA) - built for dedicated SZ effect observations. The SZA observations are sensitive to angular scales larger than those subtended by the virial radii of the clusters. Assuming isothermality and hydrostatic equilibrium for the intracluster medium, and gas-mass fractions consistent with those for clusters at moderate redshift, we calculate electron temperatures, gas masses, and total cluster masses from the SZ data. The SZ-derived masses, integrated approximately to the virial radii, are 1.9(sup +0.5)(sub -0.4) x 10(sup 14) solar mass for ClJ1415.1+3612, 3.4 (sup +0.6)(sup -0.5) x 10(sup 14) solar mass for ClJ1429.0+4241 and 7.2(sup +1.3)(sub -0.9) x 10(sup 14) solar mass for ClJ1226.9+3332. The SZ-derived quantities are in good agreement with the cluster properties derived from X-ray measurements.

Muchovej, Stephen↗