The Atacama Cosmology Telescope: A Catalog of >4000 Sunyaev–Zel’dovich Galaxy Clusters

We present a catalog of 4195 optically confirmed Sunyaev–Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg2 of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M500c > 3.8 × 1014 M⊙, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 2farcm4. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg2), the Hyper Suprime-Cam Subaru Strategic Program (469 deg2), and the Kilo Degree Survey (825 deg2). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr

Table-top ultrafast X-ray microcalorimeter spectrometry for molecular structure

This work presents an x-ray absorption measurement by use of ionizing radiation generated by a femtosecond pulsed laser source. The spectrometer was a microcalorimetric array whose pixels are capable of accurately measuring energies of individual radiation quanta. An isotropic continuum x-ray spectrum in the few-keV range was generated from a laser plasma source with a water-jet target. X rays were transmitted through a ferrocene powder sample to the detector, whose pixels have average photon energy resolution E ¼ 3:14 eV full-width-at-half-maximum at 5.9 keV. The bond distance of ferrocene was retrieved from this first hard-x-ray absorption fine-structure spectrum collected with an energydispersive detector. This technique will be broadly enabling for time-resolved observations of structural dynamics in photoactive systems.peerReviewe

Effect of magnetic fields on TiAu TES bolometers for the SAFARI instrument on the SPICA FIR telescope

At the Netherlands Institute for Space Research (SRON) we are developing Transition Edge Sensors (TES) bolometers for the SAFARI Imaging Spectrometer on the SPICA telescope. With the current design of the SPICA telescope a background magnetic field of about a Gauss with fluctuations of a couple percent is expected. The effect of this external magnetic field on the bolometer needs to be well understood in order to design effective shielding. We present the results of an investigation of magnetic field on the performance of TES bolometers. For this experiment we used a Ti/Au TES bolometer which has a measured NEP of 5.0 × 10?19 W/Hz1/2. The TES is exposed to a parallel and perpendicular magnetic field of varying strength and the baseline and responsivity are determined. We see that the bolometers are sensitive to the perpendicular field but are relative insensitive to the parallel magnetic field. Fluctuations with a period of 30 mG are present as function of perpendicular magnetic fieldKavli Institute of NanoScienceApplied Science