Gravitational Lensing of the CMB

Speaker: Alex van Engelen (CITA, Toronto)

Abstract: Gravitational lensing of the CMB is an emerging field which allows us to make high-precision maps of the matter in the Universe, including dark matter. After a brief review of the concepts, I will discuss current efforts, including ongoing analyses with the ACTPol survey. I will then discuss prospects for new surveys being planned, including the Simons Observatory and CMB-Stage 4.

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Seeing Red: The Search for High-z Galaxy Clusters in the Clusters Occupied by Bent Radio AGN (COBRA) Survey

Speaker: Emmet Golden-Marx (BU)

Abstract:
Galaxy clusters are the largest gravitationally-bound systems in the universe. Although many spectroscopically confirmed low-redshift clusters are known, few high-redshift clusters have been found. To probe the earliest eras of cluster formation, we need high- redshift clusters with a variety of morphological states and masses. One known tracer of high-z clusters is radio loud active galactic nuclei (RLAGN). Particularly, bent, double-lobed radio sources have been shown to be an excellent tracer of galaxy clusters. These bent radio AGN have a distinct “c” shape indicative of ram pressure caused by a gaseous medium; specifically the relative motion of the host galaxy with respect to the intracluster medium bends the lobes. I’ll present results from the Clusters Occupied by Bent Radio AGN (COBRA) Survey, which consists of 646 bent, double-lobed radio sources selected from the VLA FIRST Survey and has observations in the infrared from Spitzer and optical from the 4.3m Discovery Channel Telescope. The COBRA survey spans the redshift range 0.5 < z < 3.0 and includes candidates with a wide range of masses and dynamical states. Using our IR and optical data, we measure galaxy excesses, locate red sequence galaxies, and determine photometric redshifts. As bent radio AGN are not necessarily found in brightest cluster galaxies, we use local galaxy surface density measurements to analyze the spatial offset between our bent radio AGN and newly determined cluster centers, which are estimated using the overdensity of red galaxies. We measure the surface density of all galaxies and red galaxies to better trace large-scale cluster morphologies and dynamical states. Additionally, we compare the projected surface density distributions of our clusters to a projected NFW profile to further estimate the morphological state of our clusters. We find that at least 30% of our high-z bent radio sources are in cluster environments and that these clusters appear to be in a variety of morphological states.