45 research outputs found
CCAT-prime: Science with an Ultra-widefield Submillimeter Observatory at Cerro Chajnantor
We present the detailed science case, and brief descriptions of the telescope
design, site, and first light instrument plans for a new ultra-wide field
submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m
elevation site on Cerro Chajnantor in northern Chile. Our science goals are to
study star and galaxy formation from the epoch of reionization to the present,
investigate the growth of structure in the Universe, improve the precision of
B-mode CMB measurements, and investigate the interstellar medium and star
formation in the Galaxy and nearby galaxies through spectroscopic,
polarimetric, and broadband surveys at wavelengths from 200 um to 2 mm. These
goals are realized with our two first light instruments, a large field-of-view
(FoV) bolometer-based imager called Prime-Cam (that has both camera and an
imaging spectrometer modules), and a multi-beam submillimeter heterodyne
spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very
low system emissivity, so that combined with its wide FoV at the unsurpassed
CCAT site our telescope/instrumentation combination is ideally suited to pursue
this science. The CCAT-prime telescope is being designed and built by Vertex
Antennentechnik GmbH. We expect to achieve first light in the spring of 2021.Comment: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared
Detectors and Instrumentation for Astronomy IX, June 14th, 201
Recommended from our members
The Simons Observatory: Science goals and forecasts
The Simons Observatory (SO) is a new cosmic microwave background experiment
being built on Cerro Toco in Chile, due to begin observations in the early
2020s. We describe the scientific goals of the experiment, motivate the design,
and forecast its performance. SO will measure the temperature and polarization
anisotropy of the cosmic microwave background in six frequency bands: 27, 39,
93, 145, 225 and 280 GHz. The initial configuration of SO will have three
small-aperture 0.5-m telescopes (SATs) and one large-aperture 6-m telescope
(LAT), with a total of 60,000 cryogenic bolometers. Our key science goals are
to characterize the primordial perturbations, measure the number of
relativistic species and the mass of neutrinos, test for deviations from a
cosmological constant, improve our understanding of galaxy evolution, and
constrain the duration of reionization. The SATs will target the largest
angular scales observable from Chile, mapping ~10% of the sky to a white noise
level of 2 K-arcmin in combined 93 and 145 GHz bands, to measure the
primordial tensor-to-scalar ratio, , at a target level of .
The LAT will map ~40% of the sky at arcminute angular resolution to an expected
white noise level of 6 K-arcmin in combined 93 and 145 GHz bands,
overlapping with the majority of the LSST sky region and partially with DESI.
With up to an order of magnitude lower polarization noise than maps from the
Planck satellite, the high-resolution sky maps will constrain cosmological
parameters derived from the damping tail, gravitational lensing of the
microwave background, the primordial bispectrum, and the thermal and kinematic
Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle
polarization signal to measure the tensor-to-scalar ratio. The survey will also
provide a legacy catalog of 16,000 galaxy clusters and more than 20,000
extragalactic sources
The Simons Observatory microwave SQUID multiplexing detector module design
Advances in cosmic microwave background (CMB) science depend on increasing
the number of sensitive detectors observing the sky. New instruments deploy
large arrays of superconducting transition-edge sensor (TES) bolometers tiled
densely into ever larger focal planes. High multiplexing factors reduce the
thermal loading on the cryogenic receivers and simplify their design. We
present the design of focal-plane modules with an order of magnitude higher
multiplexing factor than has previously been achieved with TES bolometers. We
focus on the novel cold readout component, which employs microwave SQUID
multiplexing (mux). Simons Observatory will use 49 modules containing
60,000 bolometers to make exquisitely sensitive measurements of the CMB. We
validate the focal-plane module design, presenting measurements of the readout
component with and without a prototype detector array of 1728
polarization-sensitive bolometers coupled to feedhorns. The readout component
achieves a yield and a 910 multiplexing factor. The median white noise
of each readout channel is 65 . This impacts the
projected SO mapping speed by , which is less than is assumed in the
sensitivity projections. The results validate the full functionality of the
module. We discuss the measured performance in the context of SO science
requirements, which are exceeded.Comment: Accepted to The Astrophysical Journa
The Atacama Cosmology Telescope: DR6 Gravitational Lensing Map and Cosmological Parameters
We present cosmological constraints from a gravitational lensing mass map
covering 9400 sq. deg. reconstructed from CMB measurements made by the Atacama
Cosmology Telescope (ACT) from 2017 to 2021. In combination with BAO
measurements (from SDSS and 6dF), we obtain the amplitude of matter
fluctuations at 1.8% precision,
and the Hubble
constant at
1.6% precision. A joint constraint with CMB lensing measured by the Planck
satellite yields even more precise values: ,
and . These measurements agree
well with CDM-model extrapolations from the CMB anisotropies measured
by Planck. To compare these constraints to those from the KiDS, DES, and HSC
galaxy surveys, we revisit those data sets with a uniform set of assumptions,
and find from all three surveys are lower than that from ACT+Planck
lensing by varying levels ranging from 1.7-2.1. These results motivate
further measurements and comparison, not just between the CMB anisotropies and
galaxy lensing, but also between CMB lensing probing on
mostly-linear scales and galaxy lensing at on smaller scales. We
combine our CMB lensing measurements with CMB anisotropies to constrain
extensions of CDM, limiting the sum of the neutrino masses to eV (95% c.l.), for example. Our results provide independent
confirmation that the universe is spatially flat, conforms with general
relativity, and is described remarkably well by the CDM model, while
paving a promising path for neutrino physics with gravitational lensing from
upcoming ground-based CMB surveys.Comment: 30 pages, 16 figures, prepared for submission to ApJ. Cosmological
likelihood data is here:
https://lambda.gsfc.nasa.gov/product/act/actadv_prod_table.html ; likelihood
software is here: https://github.com/ACTCollaboration/act_dr6_lenslike . Also
see companion papers Qu et al and MacCrann et al. Mass maps will be released
when papers are publishe
The Atacama Cosmology Telescope: High-resolution component-separated maps across one-third of the sky
Observations of the millimeter sky contain valuable information on a number
of signals, including the blackbody cosmic microwave background (CMB), Galactic
emissions, and the Compton- distortion due to the thermal Sunyaev-Zel'dovich
(tSZ) effect. Extracting new insight into cosmological and astrophysical
questions often requires combining multi-wavelength observations to spectrally
isolate one component. In this work, we present a new arcminute-resolution
Compton- map, which traces out the line-of-sight-integrated electron
pressure, as well as maps of the CMB in intensity and E-mode polarization,
across a third of the sky (around 13,000 sq.~deg.). We produce these through a
joint analysis of data from the Atacama Cosmology Telescope (ACT) Data Release
4 and 6 at frequencies of roughly 93, 148, and 225 GHz, together with data from
the \textit{Planck} satellite at frequencies between 30 GHz and 545 GHz. We
present detailed verification of an internal linear combination pipeline
implemented in a needlet frame that allows us to efficiently suppress Galactic
contamination and account for spatial variations in the ACT instrument noise.
These maps provide a significant advance, in noise levels and resolution, over
the existing \textit{Planck} component-separated maps and will enable a host of
science goals including studies of cluster and galaxy astrophysics, inferences
of the cosmic velocity field, primordial non-Gaussianity searches, and
gravitational lensing reconstruction of the CMB.Comment: The Compton-y map and associated products will be made publicly
available upon publication of the paper. The CMB T and E mode maps will be
made available when the DR6 maps are made publi
The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and its Implications for Structure Growth
We present new measurements of cosmic microwave background (CMB) lensing over
sq. deg. of the sky. These lensing measurements are derived from the
Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) CMB dataset, which
consists of five seasons of ACT CMB temperature and polarization observations.
We determine the amplitude of the CMB lensing power spectrum at
precision ( significance) using a novel pipeline that minimizes
sensitivity to foregrounds and to noise properties. To ensure our results are
robust, we analyze an extensive set of null tests, consistency tests, and
systematic error estimates and employ a blinded analysis framework. The
baseline spectrum is well fit by a lensing amplitude of
relative to the Planck 2018 CMB power spectra
best-fit CDM model and relative to
the best-fit model. From our lensing power
spectrum measurement, we derive constraints on the parameter combination
of
from ACT DR6 CMB lensing alone and
when combining ACT DR6 and Planck NPIPE
CMB lensing power spectra. These results are in excellent agreement with
CDM model constraints from Planck or
CMB power spectrum measurements. Our lensing measurements from redshifts
-- are thus fully consistent with CDM structure growth
predictions based on CMB anisotropies probing primarily . We find no
evidence for a suppression of the amplitude of cosmic structure at low
redshiftsComment: 45+21 pages, 50 figures. Prepared for submission to ApJ. Also see
companion papers Madhavacheril et al and MacCrann et a
The Atacama Cosmology Telescope: Detection of the pairwise kinematic Sunyaev-Zel'dovich effect with SDSS DR15 galaxies
We present a
5.4
σ
detection of the pairwise kinematic Sunyaev-Zeldovich (kSZ) effect using Atacama Cosmology Telescope (ACT) and Planck CMB observations in combination with Luminous Red Galaxy samples from the Sloan Digital Sky Survey (SDSS) DR15 catalog. Results are obtained using three ACT CMB maps: co-added 150 and 98 GHz maps, combining observations from 2008–2018 (ACT DR5), which overlap with SDSS DR15 over 3,700 sq. deg., and a component-separated map using night-time only observations from 2014–2015 (ACT DR4), overlapping with SDSS DR15 over 2,089 sq. deg. Comparisons of the results from these three maps provide consistency checks in relation to potential frequency-dependent foreground contamination. A total of 343,647 galaxies are used as tracers to identify and locate galaxy groups and clusters from which the kSZ signal is extracted using aperture photometry. We consider the impact of various aperture photometry assumptions and covariance estimation methods on the signal extraction. Theoretical predictions of the pairwise velocities are used to obtain best-fit, mass-averaged, optical depth estimates for each of five luminosity-selected tracer samples. A comparison of the kSZ-derived optical depth measurements obtained here to those derived from the thermal SZ effect for the same sample is presented in a companion paper