The Atacama Cosmology Telescope: CO(J = 3 - 2) Mapping and Lens Modeling of an ACT-selected Dusty Star-forming Galaxy
Gallardo, Patricio A.; Huffenberger, Kevin M.; Hughes, John P.; Marriage, Tobias A.; Partridge, Bruce; Wollack, Edward J.; Keeton, Charles R.; Walter, Fabian; Baker, Andrew J.; Sievers, Jonathan L.; Tagore, Amitpal S.; Rivera, Jesus; Gralla, Megan B.; Harris, Andrew I.; López-Caraballo, Carlos H.; Weiß, Axel
United States, Chile, South Africa, Canada, United Kingdom, Germany
Abstract
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 μ ≈ 7-22 with a luminosity-weighted mean ≤ft< μ \right> ≈ 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 {L}CO(3-2)}{\prime }=(5.53+/- 0.69)× {10}10 {{K}} {km} {{{s}}}-1 {pc}}2, a cold gas mass {M}gas}=(3.86+/- 0.33)× {10}10 {M}⊙ , a dynamical mass {M}dyn} {\sin }2 i={3.9}-1.5+1.8× {10}10 {M}⊙ , 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 ≈ 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.