Browsing by Author "Spergel, David"

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    LUMINOUS RED GALAXY POPULATION IN CLUSTERS AT 0.2 ≤ z ≤ 0.6
    (2009) Ho, Shirley; Lin, Yen-Ting; Spergel, David; Hirata, Christopher M.
    We investigate statistical properties of luminous red galaxies (LRGs) in a sample of X-ray-selected galaxy clusters at intermediate redshift (0.2 <= z <= 0.6) of mass range from similar to 1 x 10(14) M(circle dot) to similar to 8 x 10(14) M(circle dot). The LRGs are selected based on carefully designed color criteria, and the cluster membership is assessed via photometric redshifts. As clusters and LRGs are both viewed as promising tracer of the underlying dark matter distribution, understanding the distribution of LRGs within clusters is an important issue. Our main findings include ( 1) the halo occupation distribution ( HOD) of LRGs inside our cluster sample is < N(M)> = k(M/10(14)h(-1)M(circle dot)) a, where a = 0.495 +/- 0.105 and k = 1.455 +/- 0.285 assuming a Poisson distribution for N(M). If we assume the form of < N( M) > = 1 + k(M/10(14)h(-1)M(circle dot)) a, where a = 0.580 +/- 0.130 and k = 0.975 +/- 0.240 assuming a Poisson distribution for N( M). ( 2) The HOD of LRGs [ N( M)] and the satellite distribution of LRGs [N(M)-1] are both consistent with being Poisson. To be more quantitative, we find Var(N)/< N > = 1.43 +/- 0.35 and Var(N-1)/< N-1 > = 1.82 +/- 0.50. ( 3) The radial profile of LRGs within clusters when fitted with a Navarro-Frenk-White profile gives a concentration of 17.5(-4.3)(+7.1) (6.0(-1.9)(+3.2)) including (excluding) brightest LRGs (BLRGs). In essence, the BLRGs are more concentrated toward the center of the clusters than the other LRGs in clusters. We also discuss the implications of these observations on the evolution of massive galaxies in clusters.
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    The Atacama Cosmology Telescope: arcminute-resolution maps of 18 000 square degrees of the microwave sky from ACT 2008-2018 data combined with Planck
    (2020) Naess, Sigurd; Aiola, Simone; Austermann, Jason E.; Battaglia, Nick; Beall, James A.; Becker, Daniel T.; Bond, Richard J.; Calabrese, Erminia; Choi, Steve K.; Cothard, Nicholas F.; Crowley, Kevin T.; Darwish, Omar; Datta, Rahul; Denison, Edward, V; Devlin, Mark; Duell, Cody J.; Duff, Shannon M.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Duenner, Rolando; Fox, Anna E.; Gallardo, Patricio A.; Halpern, Mark; Han, Dongwon; Hasselfield, Matthew; Hill, J. Colin; Hilton, Gene C.; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Ho, Shuay-Pwu Patty; Hubmayr, Johannes; Huffenberger, Kevin; Hughes, John P.; Kosowsky, Arthur B.; Louis, Thibaut; Madhavacheril, Mathew S.; McMahon, Jeff; Moodley, Kavilan; Nati, Federico; Nibarger, John P.; Niemack, Michael D.; Page, Lyman; Partridge, Bruce; Salatino, Maria; Schaan, Emmanuel; Schillaci, Alessandro; Schmitt, Benjamin; Sherwin, Blake D.; Sehgal, Neelima; Sifon, Cristobal; Spergel, David; Staggs, Suzanne; Stevens, Jason; Storer, Emilie; Ullom, Joel N.; Vale, Leila R.; Van Engelen, Alexander; Van Lanen, Jeff; Vavagiakis, Eve M.; Wollack, Edward J.; Xu, Zhilei
    This paper presents a maximum-likelihood algorithm for combining sky maps with disparate sky coverage, angular resolution and spatially varying anisotropic noise into a single map of the sky. We use this to merge hundreds of individual maps covering the 2008-2018 ACT observing seasons, resulting in by far the deepest ACT maps released so far. We also combine the maps with the full Planck maps, resulting in maps that have the best features of both Planck and ACT: Planck's nearly white noise on intermediate and large angular scales and ACT's high-resolution and sensitivity on small angular scales. The maps cover over 18 000 square degrees, nearly half the full sky, at 100, 150 and 220 GHz. They reveal 4 000 optically-confirmed clusters through the Sunyaev Zel'dovich effect (SZ) and 18 500 point source candidates at > 5 sigma, the largest single collection of SZ clusters and millimeter wave sources to date. The multi-frequency maps provide millimeter images of nearby galaxies and individual Milky Way nebulae, and even clear detections of several nearby stars. Other anticipated uses of these maps include, for example, thermal SZ and kinematic SZ cluster stacking, CMB cluster lensing and galactic dust science. The method itself has negligible bias. However, due to the preliminary nature of some of the component data sets, we caution that these maps should not be used for precision cosmological analysis. The maps are part of ACT DR5, and will be made available on LAMBDA no later than three months after the journal publication of this article, along with an interactive sky atlas.
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    The Atacama Cosmology Telescope: Detection of Millimeter-wave Transient Sources
    (2021) Naess, Sigurd; Battaglia, Nick; Bond, J. Richard; Calabrese, Erminia; Choi, Steve K.; Cothard, Nicholas F.; Devlin, Mark; Duell, Cody J.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Dunner, Rolando; Gallardo, Patricio A.; Gralla, Megan; Guan, Yilun; Halpern, Mark; Hill, J. Colin; Hilton, Matt; Huffenberger, Kevin M.; Koopman, Brian J.; Kosowsky, Arthur B.; Madhavacheril, Mathew S.; McMahon, Jeff; Nati, Federico; Niemack, Michael D.; Page, Lyman; Partridge, Bruce; Salatino, Maria; Sehgal, Neelima; Spergel, David; Staggs, Suzanne; Wollack, Edward J.; Xu, Zhilei
    We report on the serendipitous discovery of three transient millimeter-wave sources using data from the Atacama Cosmology Telescope. The first, detected at R.A. = 273.8138, decl. = -49.4628 at similar to 50 sigma total, brightened from less than 5 mJy to at least 1100 mJy at 150 GHz with an unknown rise time shorter than 13 days, during which the increase from 250 mJy to 1100 mJy took only 8 minutes. Maximum flux was observed on 2019 November 8. The source's spectral index in flux between 90-150 GHz was positive, alpha = 1.5 +/- 0.2. The second, detected at R.A. = 105.1584, decl. = -11.2434 at similar to 20 sigma total, brightened from less than 20 mJy to at least 300 mJy at 150 GHz with an unknown rise time shorter than 8 days. Maximum flux was observed on 2019 December 15. Its spectral index was also positive, alpha = 1.8 +/- 0.2. The third, detected at R.A. = 301.9952, decl. = 16.1652 at similar to 40 sigma total, brightened from less than 8 mJy to at least 300 mJy at 150 GHz over a day or less but decayed over a few days. Maximum flux was observed on 2018 September 11. Its spectrum was approximately flat, with a spectral index of alpha = -0.2 +/- 0.1. None of the sources were polarized to the limits of these measurements. The two rising-spectrum sources are coincident in position with M and K stars, while the third is coincident with a G star.