Browsing by Author "Keeton, Charles R."

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    A Multiwavelength Approach to Constraining the Merger Properties of ACT-CL J0034.4+0225
    (2024) Doze, Peter; Hilton, Matt; Hughes, John P.; Keeton, Charles R.; Knowles, Kenda; Moodley, Kavilan; Mroczkowski, Tony; Partridge, Bruce; Raney, Catie A.; Sifon, Cristobal; Sikhosana, Sinenhlanhla; Vargas, Cristian; Wollack, Edward J.
    ACT-CL J0034.4+0225 is a previously unrecognized merging galaxy cluster at z = 0.38588 +/- 0.00068. Our primary evidence is provided by a 21 ks Chandra image that shows two surface brightness peaks separated by similar to 49 '' (259 kpc) surrounded by an extended cluster gas distribution. Each gas peak contains a brightest cluster galaxy, offset from the gas peak. We collect new South African Large Telescope optical spectra that, when augmented by archival data, yield redshifts for the two BGCs and 58 other cluster members. Archival Giant Metrewave Radio Telescope and MeerKAT data reveal a radio halo that encompasses the X-ray peaks. We provide and compare three X-ray-based mass estimates (5.0 x 1014 M circle dot, 6.4 x 1014 M circle dot, and 8.6 x 1014 M circle dot). The Planck and ACT Sunyaev-Zel'dovich masses are approximate to 5.8 x 1014 M circle dot. We constrain the merger state and properties by comparing them to an existing suite of N-body/hydrodynamical models using the measured gas peak separation (259 kpc, projected) and radial velocity difference (0-1000 km s-1). This constrains the epoch of the merger to be within similar to 100 Myr of first pericenter passage. A strong lensing analysis constrains the mass ratio to be in the range 1:1-1:20, while the cluster morphology prefers values near the equal-mass range.
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    The Atacama Cosmology Telescope: CO(J=3-2) Mapping and Lens Modeling of an ACT-selected Dusty Star-forming Galaxy
    (2019) Rivera, Jesus; Baker, Andrew J.; Gallardo, Patricio A.; Gralla, Megan B.; Harris, Andrew, I; Huffenberger, Kevin M.; Hughes, John P.; Keeton, Charles R.; Lopez-Caraballo, Carlos H.; Marriage, Tobias A.; Partridge, Bruce; Sievers, Jonathan L.; Tagore, Amitpal S.; Walter, Fabian; Weiss, Axel; Wollack, Edward J.
    We report Northern Extended Millimeter Array CO(J = 3 - 2) observations of the dusty star-forming galaxy ACT-S J020941+001557 at z = 2.5528, which was detected as an unresolved source in the Atacama Cosmology Telescope (ACT) equatorial survey. Our spatially resolved spectral line data support the derivation of a gravitational lens model from 37 independent velocity channel maps using a pixel-based algorithm, from which we infer a velocity-dependent magnification factor mu approximate to 7-22 with a luminosity-weighted mean approximate to 13. The resulting source-plane reconstruction is consistent with a rotating disk, although other scenarios cannot be ruled out by our data. After correction for lensing, we derive a line luminosity LCO(3-2)' = (5.53 +/- 0.69) x 10(10) K km s(-1) pc(2), a cold gas mass M-gas = (3.86 +/- 0.33) x 10(10) M-circle dot, a dynamical mass M-dyn sin(2) i = 3.9(-1.5)(+1.8) x 10(10) M-circle dot, and a gas mass fraction f(gas) csc(2) i = 1.0(-0.4)(+0.8). The line brightness temperature ratio of r(3,1) approximate to 1.6 relative to a Green Bank Telescope CO(J = 1 - 0) detection may be elevated by a combination of external heating of molecular clouds, differential lensing, and/or pointing errors.