The Atacama Cosmology Telescope: Arcminute-resolution maps of 18 000 square degrees of the microwave sky from ACT 2008–2018 data combined with Planck

Sigurd Naess, Simone Aiola, Jason E. Austermann, Nick Battaglia, James A. Beall, Daniel T. Becker, Richard J. Bond, Erminia Calabrese, Steve K. Choi, Nicholas F. Cothard, Kevin T. Crowley, Omar Darwish, Rahul Datta, Edward V. Denison, Mark Devlin, Cody J. Duell, Shannon M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Rolando DünnerAnna E. Fox, Patricio A. Gallardo, Mark Halpern, Dongwon Han, Matthew Hasselfield, J. Colin Hill, Gene C. Hilton, Matt Hilton, Adam D. Hincks, Renée Hložek, Shuay Pwu Patty Ho, Johannes Hubmayr, Kevin Huffenberger, John P. Hughes, Arthur B. Kosowsky, Thibaut Louis, Mathew S. Madhavacheril, Jeff McMahon, Kavilan Moodley, Federico Nati, John P. Nibarger, Michael D. Niemack, Lyman Page, Bruce Partridge, Maria Salatino, Emmanuel Schaan, Alessandro Schillaci, Benjamin Schmitt, Blake D. Sherwin, Neelima Sehgal, Cristóbal Sifón, David Spergel, Suzanne Staggs, Jason Stevens, Emilie Storer, Joel N. Ullom, Leila R. Vale, Alexander van Engelen, Jeff van Lanen, Eve M. Vavagiakis, Edward J. Wollack, Zhilei Xu

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


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 > 5σ, 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.

Original languageEnglish (US)
JournalJournal of Cosmology and Astroparticle Physics
Issue number12
StatePublished - Dec 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics


  • CMBR experiments
  • CMBR polarisation


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