Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

The Atacama Cosmology Telescope: DR5 maps of 18,000 square degrees of the microwave sky from ACT 2008-2018 data

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 Dünner, Anna 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

TL;DR

The paper introduces a maximum-likelihood framework to coadd heterogeneous microwave sky maps with varying coverage, resolution, and anisotropic noise into a single, deep sky map. It implements a tiled constant-correlation noise model to capture spatially varying correlations, couples ACT data (2008–2018) with Planck to produce DR5 maps at 100/150/220 GHz, and solves the resulting linear system with efficient preconditioned conjugate gradients. The resulting ACT+Planck and ACT-only maps reach large sky coverage (>18,000 deg$^2$) with unprecedented depth and reveal thousands of SZ clusters and hundreds of millimeter sources, enabling diverse astrophysical and cosmological studies while warning about the preliminary data limitations. This work provides a publicly accessible data product and a generalizable coadding methodology for heterogeneous, large-scale sky surveys, with significant implications for multi-instrument CMB and foreground science.

Abstract

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 are available on LAMBDA at https://lambda.gsfc.nasa.gov/product/act/actpol_prod_table.cfm. There is also a web atlas at https://phy-act1.princeton.edu/public/snaess/actpol/dr5/atlas.

The Atacama Cosmology Telescope: DR5 maps of 18,000 square degrees of the microwave sky from ACT 2008-2018 data

TL;DR

The paper introduces a maximum-likelihood framework to coadd heterogeneous microwave sky maps with varying coverage, resolution, and anisotropic noise into a single, deep sky map. It implements a tiled constant-correlation noise model to capture spatially varying correlations, couples ACT data (2008–2018) with Planck to produce DR5 maps at 100/150/220 GHz, and solves the resulting linear system with efficient preconditioned conjugate gradients. The resulting ACT+Planck and ACT-only maps reach large sky coverage (>18,000 deg) with unprecedented depth and reveal thousands of SZ clusters and hundreds of millimeter sources, enabling diverse astrophysical and cosmological studies while warning about the preliminary data limitations. This work provides a publicly accessible data product and a generalizable coadding methodology for heterogeneous, large-scale sky surveys, with significant implications for multi-instrument CMB and foreground science.

Abstract

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 , 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 are available on LAMBDA at https://lambda.gsfc.nasa.gov/product/act/actpol_prod_table.cfm. There is also a web atlas at https://phy-act1.princeton.edu/public/snaess/actpol/dr5/atlas.

Paper Structure

This paper contains 39 sections, 10 equations, 29 figures, 1 table.

Table of Contents

  1. Introduction
  2. The data
  3. Planck
  4. Atacama Cosmology Telescope
  5. ACT-MBAC
  6. ACT DR4
  7. Preliminary Advanced ACTPol
  8. Preliminary ACT daytime data
  9. Co-adding maps
  10. Beam Model
  11. Choosing the Noise Model
  12. Uncorrelated noise model
  13. Constant covariance noise model
  14. Constant correlation noise model
  15. Tiled constant correlation noise model
  16. ...and 24 more sections

Figures (29)

  • Figure 1: Comparison of Planck, ACT+ Planck and ACT-only in a $3^\circ\times3^\circ$ patch centered on RA = 231.5$^\circ$, dec = 16.5$^\circ$. The map of this region includes ACT daytime data. The ACT map depths in this region are 8/8/30 µK-arcmin at f090/f150/f220 (see figure \ref{['fig:bands']} for band definitions). ACT+ Planck is a substantial improvement over Planck alone, both in resolution and depth, and captures the larger scales that ACT alone has trouble measuring. See figure \ref{['fig:matched-filter']} for an image filtered to emphasize the point sources, clusters and other small-scale features.
  • Figure 2: Comparison of the ACT and Planck bandpasses in the range 60 GHz to 270 GHz. (See Section \ref{['sec:act_data']} for description of the three ACT cameras: MBAC, ACTPol and Advanced ACTPol.) They fall into three groups, centered at roughly 90 GHz, 150 GHz and 220 GHz. We label these bandpass-groups f090, f150 and f220. In this paper we approximate all bandpasses in each group as being equivalent. This results in a small scale-dependence of the effective band center for non-CMB parts of the combined maps -- see section \ref{['sec:bandpasses']}.
  • Figure 3: Left: Night-night (red), night-day (green) and day-day (blue) cross pseudo-spectra as a function of multipole for s18 PA5 f090 for the Day-N patch. The daytime loss in power on small scales is clearly visible. Right: The day/night relative beam inferred from the three spectra in each bin (red), and the smooth three-parameter model fit to it (green). See section \ref{['sec:daybeam']} for details.
  • Figure 4: Left: The ACT PA1 and PA2 beams at f150, and their ratio. The ratio is quite constant up to $\ell = 20000$, where the beam model breaks down and the ratio starts swinging wildly. Right: The same beams after regularizing them by replacing the values after they fall to 0.01 of the peak with a smooth function that preserves the beam ratio.
  • Figure 5: The uncorrelated noise model (left) can represent spatially inhomogeneous noise, but ignores all spatial correlations. The constant covariance noise model (middle) is the opposite, capturing complex spatial correlations but having no concept of position-dependence. The constant correlation noise model (right) combines these two models to allow for both correlation and inhomogeneity.
  • ...and 24 more figures