1,876 research outputs found
The Cosmology Large Angular Scale Surveyor
The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array
designed to characterize relic primordial gravitational waves from inflation
and the optical depth to reionization through a measurement of the polarized
cosmic microwave background (CMB) on the largest angular scales. The
frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one
dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high
atmospheric emission and span the minimum of the polarized Galactic
foregrounds: synchrotron emission at lower frequencies and dust emission at
higher frequencies. Low-noise transition edge sensor detectors and a rapid
front-end polarization modulator provide a unique combination of high
sensitivity, stability, and control of systematics. The CLASS site, at 5200 m
in the Chilean Atacama desert, allows for daily mapping of up to 70\% of the
sky and enables the characterization of CMB polarization at the largest angular
scales. Using this combination of a broad frequency range, large sky coverage,
control over systematics, and high sensitivity, CLASS will observe the
reionization and recombination peaks of the CMB E- and B-mode power spectra.
CLASS will make a cosmic variance limited measurement of the optical depth to
reionization and will measure or place upper limits on the tensor-to-scalar
ratio, , down to a level of 0.01 (95\% C.L.)
Testing CMB Anomalies in E-mode Polarization with Current and Future Data
In this paper, we explore the power of the cosmic microwave background (CMB)
polarization (E-mode) data to corroborate four potential anomalies in CMB
temperature data: the lack of large angular-scale correlations, the alignment
of the quadrupole and octupole (Q-O), the point-parity asymmetry, and the
hemispherical power asymmetry. We use CMB simulations with noise representative
of three experiments -- the Planck satellite, the Cosmology Large Angular Scale
Surveyor (CLASS), and the LiteBIRD satellite -- to test how current and future
data constrain the anomalies. We find the correlation coefficients
between temperature and E-mode estimators to be less than , except for the
point-parity asymmetry ( for cosmic-variance-limited simulations),
confirming that E-modes provide a check on the anomalies that is largely
independent of temperature data. Compared to Planck component-separated CMB
data (SMICA), the putative LiteBIRD survey would reduce errors on E-mode
anomaly estimators by factors of for hemispherical power asymmetry and
point-parity asymmetry, and by for lack of large-scale correlation.
The improvement in Q-O alignment is not obvious due to large cosmic variance,
but we found the ability to pin down the estimator value will be improved by a
factor . Improvements with CLASS are intermediate to these.Comment: 23 pages, 15 figures, 6 table
Control and systems software for the Cosmology Large Angular Scale Surveyor (CLASS)
The Cosmology Large Angular Scale Surveyor (CLASS) is an array of
polarization-sensitive millimeter wave telescopes that observes ~70% of the sky
at frequency bands centered near 40GHz, 90GHz, 150GHz, and 220GHz from the
Atacama desert of northern Chile. Here, we describe the architecture of the
software used to control the telescopes, acquire data from the various
instruments, schedule observations, monitor the status of the instruments and
observations, create archival data packages, and transfer data packages to
North America for analysis. The computer and network architecture of the CLASS
observing site is also briefly discussed. This software and architecture has
been in use since 2016, operating the telescopes day and night throughout the
year, and has proven successful in fulfilling its design goals.Comment: 19 pages, 8 figures, to appear in Proc. SPI
CLASS Observations of Atmospheric Cloud Polarization at Millimeter Wavelengths
The dynamic atmosphere imposes challenges to ground-based cosmic microwave
background observation, especially for measurements on large angular scales.
The hydrometeors in the atmosphere, mostly in the form of clouds, scatter the
ambient thermal radiation and are known to be the main linearly polarized
source in the atmosphere. This scattering-induced polarization is significantly
enhanced for ice clouds due to the alignment of ice crystals under gravity,
which are also the most common clouds seen at the millimeter-astronomy sites at
high altitudes. This work presents a multifrequency study of cloud polarization
observed by the Cosmology Large Angular Scale Surveyor (CLASS) experiment on
Cerro Toco in the Atacama Desert of northern Chile, from 2016 to 2022, at the
frequency bands centered around 40, 90, 150, and 220 GHz. Using a
machine-learning-assisted cloud classifier, we made connections between the
transient polarized emission found in all four frequencies with the clouds
imaged by monitoring cameras at the observing site. The polarization angles of
the cloud events are found to be mostly from the local meridian,
which is consistent with the presence of horizontally aligned ice crystals. The
90 and 150 GHz polarization data are consistent with a power law with a
spectral index of , while an excess/deficit of polarization
amplitude is found at 40/220 GHz compared with a Rayleigh scattering spectrum.
These results are consistent with Rayleigh-scattering-dominated cloud
polarization, with possible effects from supercooled water absorption and/or
Mie scattering from a population of large cloud particles that contribute to
the 220 GHz polarization.Comment: 16 pages, 14 figures, submitted to Ap
Microwave Observations of Venus with CLASS
We report on the disk-averaged absolute brightness temperatures of Venus
measured at four microwave frequency bands with the Cosmology Large Angular
Scale Surveyor (CLASS). We measure temperatures of 432.3 2.8 K, 355.6
1.3 K, 317.9 1.7 K, and 294.7 1.9 K for frequency bands
centered at 38.8, 93.7, 147.9, and 217.5 GHz, respectively. We do not observe
any dependence of the measured brightness temperatures on solar illumination
for all four frequency bands. A joint analysis of our measurements with lower
frequency Very Large Array (VLA) observations suggests relatively warmer
( 7 K higher) mean atmospheric temperatures and lower abundances of
microwave continuum absorbers than those inferred from prior radio occultation
measurements.Comment: 10 pages, 3 figures, published in PS
Notch Signaling Regulates Mitochondrial Metabolism and NF-κB Activity in Triple-Negative Breast Cancer Cells via IKKα-Dependent Non-canonical Pathways
Triple negative breast cancer (TNBC) patients have high risk of recurrence and metastasis, and current treatment options remain limited. Cancer stem-like cells (CSCs) have been linked to cancer initiation, progression and chemotherapy resistance. Notch signaling is a key pathway regulating TNBC CSC survival. Treatment of TNBC with PI3K or mTORC1/2 inhibitors results in drug-resistant, Notch-dependent CSC. However, downstream mechanisms and potentially druggable Notch effectors in TNBC CSCs are largely unknown. We studied the role of the AKT pathway and mitochondrial metabolism downstream of Notch signaling in TNBC CSC from cell lines representative of different TNBC molecular subtypes as well as a novel patient-derived model. We demonstrate that exposure of TNBC cells to recombinant Notch ligand Jagged1 leads to rapid AKT phosphorylation in a Notch1-dependent but RBP-Jκ independent fashion. This requires mTOR and IKKα. Jagged1 also stimulates mitochondrial respiration and fermentation in an AKT- and IKK-dependent fashion. Notch1 co-localizes with mitochondria in TNBC cells. Pharmacological inhibition of Notch cleavage by gamma secretase inhibitor PF-03084014 in combination with AKT inhibitor MK-2206 or IKK-targeted NF-κB inhibitor Bay11-7082 blocks secondary mammosphere formation from sorted CD90hi or CD44+CD24low (CSCs) cells. A TNBC patient-derived model gave comparable results. Besides mitochondrial oxidative metabolism, Jagged1 also triggers nuclear, NF-κB-dependent transcription of anti-apoptotic gene cIAP-2. This requires recruitment of Notch1, IKKα and NF-κB to the cIAP-2 promoter. Our observations support a model where Jagged1 triggers IKKα-dependent, mitochondrial and nuclear Notch1 signals that stimulate AKT phosphorylation, oxidative metabolism and transcription of survival genes in PTEN wild-type TNBC cells. These data suggest that combination treatments targeting the intersection of the Notch, AKT and NF-κB pathways have potential therapeutic applications against CSCs in TNBC cases with Notch1 and wild-type PTEN expression
CLASS Angular Power Spectra and Map-Component Analysis for 40 GHz Observations through 2022
Measurement of the largest angular scale () features of the cosmic
microwave background (CMB) polarization is a powerful way to constrain the
optical depth to reionization, , and search for the signature of
inflation through the detection of primordial -modes. We present an analysis
of maps covering nearly 75% of the sky made from the ground-based
channel of the Cosmology Large Angular Scale Surveyor
(CLASS) from August 2016 to May 2022. Using fast front-end polarization
modulation from the Atacama Desert in Chile, we show this channel achieves
higher sensitivity than the analogous frequencies from satellite measurements
in the range . After a final calibration adjustment, noise
simulations show the CLASS linear (circular) polarization maps have a white
noise level of . We measure the
Galaxy-masked and spectra of diffuse synchrotron radiation and
compare to space-based measurements at similar frequencies. In combination with
external data, we expand measurements of the spatial variations of the
synchrotron spectral energy density (SED) to include new regions of the sky and
measure the faint diffuse SED in the harmonic domain. We place a new upper
limit on a background of circular polarization in the range
with the first bin showing at 95%
confidence. These results establish a new standard for recovery of the
largest-scale CMB polarization from the ground and signal exciting
possibilities when the higher sensitivity and higher frequency CLASS channels
are included in the analysis.Comment: 36 pages, 24 figures, 6 tables. Submitted to The Astrophysical
Journa
Venus Observations at 40 and 90 GHz with CLASS
Using the Cosmology Large Angular Scale Surveyor, we measure the
disk-averaged absolute Venus brightness temperature to be 432.3 2.8 K and
355.6 1.3 K in the Q and W frequency bands centered at 38.8 and 93.7 GHz,
respectively. At both frequency bands, these are the most precise measurements
to date. Furthermore, we observe no phase dependence of the measured
temperature in either band. Our measurements are consistent with a
CO-dominant atmospheric model that includes trace amounts of additional
absorbers like SO and HSO.Comment: 7 pages, 3 figures, published in PS
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