Browsing by Author "Sifon, Cristobal"

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    Atacama Cosmology Telescope: Constraints on cosmic birefringence
    (AMER PHYSICAL SOC, 2020) Namikawa, Toshiya; Guan, Yilun; Darwish, Omar; Sherwin, Blake D.; Aiola, Simone; Battaglia, Nicholas; Beall, James A.; Becker, Daniel T.; Bond, J. Richard; Calabrese, Erminia; Chesmore, Grace E.; Choi, Steve K.; Devlin, Mark J.; Dunkley, Joanna; Dunner, Rolando; Fox, Anna E.; Gallardo, Patricio A.; Gluscevic, Vera; Han, Dongwon; Hasselfield, Matthew; Hilton, Gene C.; Hincks, Adam D.; Hlozek, Renee; Hubmayr, Johannes; Huffenberger, Kevin; Hughes, John P.; Koopman, Brian J.; Kosowsky, Arthur; Louis, Thibaut; Lungu, Marius; MacInnis, Amanda; Madhavacheril, Mathew S.; Mallaby Kay, Maya; Maurin, Loic; McMahon, Jeffrey; Moodley, Kavilan; Naess, Sigurd; Nati, Federico; Newburgh, Laura B.; Nibarger, John P.; Niemack, Michael D.; Page, Lyman A.; Qu, Frank J.; Robertson, Naomi; Schillaci, Alessandro; Sehgal, Neelima; Sifon, Cristobal; Simon, Sara M.; Spergel, David N.; Staggs, Suzanne T.; Storer, Emilie R.; van Engelen, Alexander; van Lanen, Jeff; Wollack, Edward J.
    We present new constraints on anisotropic birefringence of the cosmic microwave background polarization using two seasons of data from the Atacama Cosmology Telescope covering 456 square degrees of sky. The birefringence power spectrum, measured using a curved-sky quadratic estimator, is consistent with zero. Our results provide the tightest current constraint on birefringence over a range of angular scales between 5 arc minutes and 9 degrees. We improve previous upper limits on the amplitude of a scale-invariant birefringence power spectrum by a factor of between 2 and 3. Assuming a nearly massless axion field during inflation, our result is equivalent to a 2 sigma upper limit on the Chern-Simons coupling constant between axions and photons of g(alpha gamma) < 4.0 x 10(-2)/H-I, where H-I is the inflationary Hubble scale.
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    Intrinsic Morphology of Ultra-diffuse Galaxies
    (IOP PUBLISHING LTD, 2020) Rong, Yu; Dong, Xiao Yu; Puzia, Thomas H.; Galaz, Gaspar; Sanchez Janssen, Ruben; Cao, Tianwen; van der Burg, Remco F. J.; Sifon, Cristobal; Pina, Pavel E. Mancera; Marcelo, Mora; D'Ago, Giuseppe; Zhang, Hong Xin; Johnston, Evelyn J.; Eigenthaler, Paul
    With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z similar to 0.020-0.063) galaxy clusters and 84 UDGs in two intermediate-redshift (z similar to 0.308-0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert, i.e., the underlying shapes of UDGs are purely prolate (C = B < A), we find that the data favor the oblate-triaxial models (i.e., thick disks with C < B less than or similar to A) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are related to their stellar masses/luminosities, environments, and redshifts. First, the more luminous UDGs have puffier morphologies compared with the less luminous counterparts; the UDG morphologic dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs); in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories; they may differ not only in size. Second, the UDGs with smaller clustercentric distances are more puffed up, compared with the counterparts with larger clustercentric distances; in combination with the UDG thickness dependence on luminosity, the puffier morphologies of UDGs with high luminosities or located in the denser environments are very likely to be attributed to tidal interactions with massive galaxies. Third, we find that the intermediate-redshift UDGs are more flattened, compared with the low-redshift counterparts, which plausibly suggests a "disky" origin for the high-redshift, newly born UDGs.
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    The atacama cosmology telescope : The stellar content of galaxy clusters selected using the sunyaev-zel'dovich effect
    (2013) Hilton, Matt; Hasselfield, Matthew; Sifon, Cristobal; Baker, Andrew J.; Barrientos, Luis Felipe; Battaglia, Nicholas; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Infante Lira, Leopoldo