Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Grace E. Chesmore
Kathleen Harrington
Carlos E. Sierra
Patricio A. Gallardo
Shreya Sutariya
Tommy Alford
Alexandre E. Adler
Tanay Bhandarkar
Gabriele Coppi
Nadia Dachlythra
Joseph Golec
Jon Gudmundsson
Saianeesh K. Haridas
Bradley R. Johnson
Anna M. Kofman
Jeffrey Iuliano
Jeff McMahon
Michael D. Niemack
John Orlowski-Scherer
Karen Perez Sarmiento
Abstract： We present near-field radio holography measurements of the Simons Observatory Large Aperture Telescope Receiver optics. These measurements demonstrate that radio holography of complex millimeter-wave optical systems comprising cryogenic lenses, filters, and feed horns can provide detailed characterization of wave propagation before deployment. We used the measured amplitude and phase, at 4K, of the receiver near-field beam pattern to predict two key performance parameters: 1) the amount of scattered light that will spill past the telescope to 300K and 2) the beam pattern expected from the receiver when fielded on the telescope. These cryogenic measurements informed the removal of a filter, which led to improved optical efficiency and reduced side-lobes at the exit of the receiver. Holography measurements of this system suggest that the spilled power past the telescope mirrors will be less than 1\% and the main beam with its near side-lobes are consistent with the nominal telescope design. This is the first time such parameters have been confirmed in the lab prior to deployment of a new receiver. This approach is broadly applicable to millimeter and sub-millimeter instruments.
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
John Orlowski-Scherer
Saianeesh K. Haridas
Luca Di Mascolo
Karen Perez Sarmiento
Charles E. Romero
Simon Dicker
Tony Mroczkowski
Tanay Bhandarkar
Eugene Churazov
Tracy E Clarke
Mark Devlin
Massimo Gaspari
Ian Lowe
Brian Mason
Craig L Sarazin
Jonathon Sievers
Rashid Sunyaev
Abstract： Mechanical feedback from active galactic nuclei (AGN) is thought to be the dominant feedback mechanism quenching cooling flows and star formation in galaxy cluster cores. However, the mechanisms by which AGN couple to the intracluster medium (ICM) are not well understood. The nature of pressure supporting the cavities is not known. Using the MUSTANG-2 instrument on the Green Bank Telescope (GBT), we aimed to measure thermal Sunyaev-Zeldovich (SZ) effect signals associated with the X-ray cavities in MS0735.6+7421, a moderate mass cluster hosting one of the most energetic AGN outbursts known. We use these measurements to infer the level of non-thermal sources of pressure, such as magnetic fields and turbulence, as well as relativistic and cosmic ray components, supporting the cavities. We used preconditioned gradient descent to fit a model for the cluster, cavities, and central point source directly to the time ordered data of the MUSTANG-2 signal. We use this model to probe the thermodynamic state of the cavities. We have shown that the SZ signal associated with the cavities is suppressed compared to the expectations for a thermal plasma with the temperature $\sim$few tens keV. The smallest value of the suppression factor $f$ that is consistent with the data is $\sim$0.4, lower than inferred in earlier work. Larger values of $f$ are possible once the contribution of the cocoon shock surrounding the bubbles is taken into account. The baseline model with this particular geometrical setup yields best-fitting value f~0.5, which at face value implies a mix of thermal and non-thermal pressure support. Larger values of $f$ (up to 1, i.e. no tSZ signal from the bubbles) are still possible when allowing for variations in the line-of-sight geometry.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Zhilei Xu
Shunsuke Adachi
Peter Ade
J. A. Beall
Tanay Bhandarkar
J. Richard Bond
Grace E. Chesmore
Yuji Chinone
Steve K. Choi
Jake A. Connors
Gabriele Coppi
Nicholas F. Cothard
Kevin D. Crowley
Mark Devlin
Simon Dicker
Bradley Dober
Shannon M. Duff
Nicholas Galitzki
Patricio A. Gallardo
Joseph E. Golec
Abstract： The Simons Observatory (SO) is a Cosmic Microwave Background (CMB) experiment to observe the microwave sky in six frequency bands from 30GHz to 290GHz. The Observatory -- at $\sim$5200m altitude -- comprises three Small Aperture Telescopes (SATs) and one Large Aperture Telescope (LAT) at the Atacama Desert, Chile. This research note describes the design and current status of the LAT along with its future timeline.
Peer Review Status:Awaiting Review
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