MUSTANG: The MUltiplexed SQUID/TES Array at Ninety GHz

The MUltiplexed SQUID/TES Array at Ninety GHz (MUSTANG-1)

In 2002, the University of Pennsylvania initiated a collaboration with NRAO, NIST and NASA-GSFC to develop a 90 GHz receiver for the Green Bank Telescope (GBT). MUSTANG [1, 2], employs a 64-element array of transition-edge sensor (TES) bolometers utilizing the 9" resolution of the GBT. The receiver was completed in 2006 with commissioning and first observations in 2007/2008. The project was extremely successful in developing solutions to the technical challenges faced by TES bolometer array receivers, such as magnetic fields, optical design, SQUID/TES tuning, and operations on a large, multi-purpose facility telescope. We were also able to perfect scan strategies, develop a complete data pipeline, understand the impact of the weather on our data, and characterize the high-frequency performance of the GBT.

Science Objectives and Results

With MUSTANG we have made observations of jets from AGN [3] as well as star formation in our own galaxy [4]. However, the goal has always been high-resolution studies of the SZE in galaxy clusters. While other instruments have imaged many dozens of clusters through the SZE, our SZE window on cluster astrophysics has been limited to a comparatively low-resolution view of the intra-cluster medium (ICM). With MUSTANG, SZE imaging entered a new era as a powerful tool for studying astrophysics in detail in systems at redshifts z > 0.4. This was demonstrated with our observations of RXJ1347.5-1145 (3.3 hour integration), a massive cluster at z = 0.45. In the highest resolution SZE image to date (e.g. see Figure 1, from [5]), MUSTANG observations of this system strongly confirmed (> 5-sigma) the presence of merger activity only hinted at in SZE observations with the Nobeyama 45 m telescope. Recently, MUSTANG has imaged seven more clusters, discovering a shock in MACS0744 (see Figure 2, [6]) and finding strong evidence for substructure that contributes SZE flux on small scales equal to roughly 10% of the total SZE flux as measured by OVRO/BIMA.

More recently, MUSTANG imaged the disturbed, intermediate-redshift (z = 0.55) galaxy cluster MACS0717, a triple-merger system comprising four distinct, optically detected subclusters. MUSTANG SZE data confirm previous indications from Chandra of a pressure enhancement due to shock-heated, >20 keV gas immediately adjacent to extended radio emission seen in low-frequency radio maps of this cluster. MUSTANG also detects pressure substructure that is not well constrained by the Chandra X-ray data in the remnant core of a merging subcluster. Combined analysis with Bolocam observations at 140 and 268 GHz provides tantalizing evidence for a kinetic SZE component in this subcluster [7].

References

[1] S. R. Dicker, et al. A 90-GHz bolometer array for the Green Bank Telescope. In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, volume 6275 of Presented at the Society of Photo-Optical Instrumentation Engineers (SPIE) Conference, July 2006. doi: 10.1117/12.672166.

[2] S. R. Dicker, et al. MUSTANG: 90 GHz science with the Green Bank Telescope. In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, volume 7020 of Presented at the Society of Photo-Optical Instrumentation Engineers (SPIE) Conference, August 2008. doi: 10.1117/12.788361.

[3] W. D. Cotton, et al. 90 GHz Observations of M87 and Hydra A. ApJ, 701:1872-1879, August 2009. doi: 10.1088/0004-637X/701/2/1872.

[4] S. R. Dicker, et al. 90 GHz and 150 GHz Observations of the Orion M42 Region. A Submillimeter to Radio Analysis. ApJ, 705:226-236, November 2009. doi: 10.1088/0004-637X/705/1/226.

[5] B. S. Mason, et al. Implications of a High Angular Resolution Image of the Sunyaev-Zel'Dovich Effect in RXJ1347-1145. ApJ, 716:739-745, June 2010. doi: 10.1088/0004-637X/716/1/739.

[6] P. M. Korngut, S. R. Dicker, E. D. Reese, B. S. Mason, M. J. Devlin, T. Mroczkowski, C. L. Sarazin, M. Sun, and J. Sievers. MUSTANG High Angular Resolution Sunyaev-Zel'dovich Effect Imaging of Substructure in Four Galaxy Clusters. ApJ, 734:10, June 2011. doi: 10.1088/0004-637X/734/1/10.

[7] T. Mroczkowski, et al. A Multi-wavelength Study of the Sunyaev-Zel'dovich Effect in the Triple-merger Cluster MACS J0717.5+3745 with MUSTANG and Bolocam. ApJ, 761:47, December 2012. doi: 10.1088/0004-637X/761/1/47.