Browsing by Author "Datta, Rahul"

Now showing 1 - 9 of 9
  • Thumbnail Image
    Item
    CLASS Angular Power Spectra and Map-component Analysis for 40 GHz Observations through 2022
    (2024) Eimer, Joseph R.; Li, Yuyang; Brewer, Michael K.; Shi, Rui; Ali, Aamir; Appel, John W.; Bennett, Charles L.; Bruno, Sarah Marie; Bustos, Ricardo; Chuss, David T.; Cleary, Joseph; Dahal, Sumit; Datta, Rahul; Denes Couto, Jullianna; Denis, Kevin L.; Dunner, Rolando; Essinger-Hileman, Thomas; Fluxa, Pedro; Hubmayer, Johannes; Harrington, Kathleen; Iuliano, Jeffrey; Karakla, John; Marriage, Tobias A.; Nunez, Carolina; Parker, Lucas; Petroff, Matthew A.; Reeves, Rodrigo A.; Rostem, Karwan; Valle, Deniz A. N.; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Xu, Zhilei; Zeng, Lingzhen
    Measurement of the largest angular scale (l < 30) 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 B-modes. We present an analysis of maps covering 73.6% of the sky made from the 40 GHz channel of the Cosmology Large Angular Scale Surveyor (CLASS) from 2016 August to 2022 May. Taking advantage of the measurement stability enabled by front-end polarization modulation and excellent conditions from the Atacama Desert, we show this channel achieves higher sensitivity than the analogous frequencies from satellite measurements in the range 10 < l < 100. Simulations show the CLASS linear (circular) polarization maps have a white noise level of 125(130)mu Karcmin . We measure the Galaxy-masked EE and BB 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 sky regions and measure the diffuse SED in the harmonic domain. We place a new upper limit on a background of circular polarization in the range 5 < l < 125 with the first bin showing D- l < 0.023 mu K-CMB(2) 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.
  • No Thumbnail Available
    Item
    CLASS Data Pipeline and Maps for 40 GHz Observations through 2022
    (2023) Li, Yunyang; Eimer, Joseph R.; Osumi, Keisuke; Appel, John W.; Brewer, Michael K.; Ali, Aamir; Bennett, Charles L.; Bruno, Sarah Marie; Bustos, Ricardo; Chuss, David T.; Cleary, Joseph; Couto, Jullianna Denes; Dahal, Sumit; Datta, Rahul; Denis, Kevin L.; Dunner, Rolando; Espinoza, Francisco; Essinger-Hileman, Thomas; Rojas, Pedro Fluxa; Harrington, Kathleen; Iuliano, Jeffrey; Karakla, John; Marriage, Tobias A.; Miller, Nathan J.; Novack, Sasha; Nunez, Carolina; Petroff, Matthew A.; Reeves, Rodrigo A.; Rostem, Karwan; Shi, Rui; Valle, Deniz A. N.; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Xu, Zhilei; Zeng, Lingzhen; CLASS Collaboration
    The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background over 75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. This paper describes the CLASS data pipeline and maps for 40 GHz observations conducted from 2016 August to 2022 May. We demonstrate how well the CLASS survey strategy, with rapid (similar to 10 Hz) front-end modulation, recovers the large-scale Galactic polarization signal from the ground: the mapping transfer function recovers similar to 67% (85%) of EE and BB (VV) power at l = 20 and similar to 35% (47%) at l = 10. We present linear and circular polarization maps over 75% of the sky. Simulations based on the data imply the maps have a white noise level of 110 mu Karcmin and correlated noise component rising at low-l as l -2.4. The transfer-function-corrected low-l component is comparable to the white noise at the angular knee frequencies of l approximate to 18 (linear polarization) and l approximate to 12 (circular polarization). Finally, we present simulations of the level at which expected sources of systematic error bias the measurements, finding subpercent bias for the Lambda cold dark matter EE power spectra. Bias from E-to-B leakage due to the data reduction pipeline and polarization angle uncertainty approaches the expected level for an r = 0.01 BB power spectrum. Improvements to the instrument calibration and the data pipeline will decrease this bias.
  • No Thumbnail Available
    Item
    CLASS Observations of Atmospheric Cloud Polarization at millimeter Wavelengths
    (2023) Li, Yunyang; Appel, John W.; Bennett, Charles L.; Bustos, Ricardo; Chuss, David T.; Cleary, Joseph; Couto, Jullianna Denes; Dahal, Sumit; Datta, Rahul; Duenner, Rolando; Eimer, Joseph R.; Essinger-Hileman, Thomas; Harrington, Kathleen; Iuliano, Jeffrey; Marriage, Tobias A.; Petroff, Matthew A.; Reeves, Rodrigo A.; Rostem, Karwan; Shi, Rui; Valle, Deniz A. N.; Watts, Duncan J.; Wolff, Oliver F.; Wollack, Edward J.; Xu, Zhilei
    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 experiment on Cerro Toco in the Atacama Desert of northern Chile, from 2016-2022, 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 90 degrees 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 3.90 +/- 0.06, 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.
  • No Thumbnail Available
    Item
    Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
    (2024) Datta, Rahul; Brewer, Michael K.; Couto, Jullianna Denes; Eimer, Joseph; Li, Yunyang; Xu, Zhilei; Ali, Aamir; Appel, John W.; Bennett, Charles L.; Bustos, Ricardo; Chuss, David T.; Cleary, Joseph; Dahal, Sumit; Inostroza, Francisco Raul Javier Espinoza; Essinger-Hileman, Thomas; Fluxa, Pedro; Harrington, Kathleen; Helson, Kyle; Iuliano, Jeffrey; Karakla, John; Marriage, Tobias A.; Novack, Sasha; Nunez, Carolina; Padilla, Ivan L.; Parker, Lucas; Petroff, Matthew A.; Reeves, Rodrigo; Rostem, Karwan; Shi, Rui; Valle, Deniz A. N.; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Zeng, Lingzhen
    The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over similar to 75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale CMB polarization to constrain the tensor-to-scalar ratio and the optical depth to last scattering. This paper presents the optical characterization of the 90 GHz telescope. Observations of the Moon establish the pointing while dedicated observations of Jupiter are used for beam calibration. The standard deviations of the pointing error in azimuth, elevation, and boresight angle are 1.' 3, 2.' 1, and 2.' 0, respectively, over the first 3 yr of observations. This corresponds to a pointing uncertainty similar to 7% of the beam's full width at half-maximum (FWHM). The effective azimuthally symmetrized instrument 1D beam estimated at 90 GHz has an FWHM of 0.degrees 620 +/- 0.degrees 003 and a solid angle of 138.7 +/- 0.6(stats.) +/- 1.1(sys.) mu sr integrated to a radius of 4 degrees. The corresponding beam window function drops to b & ell;2=0.93,0.71,0.14 at & ell; = 30, 100, 300, respectively. Far-sidelobes are studied using detector-centered intensity maps of the Moon and measured to be at a level of 10-3 or below relative to the peak. The polarization angle of Tau A estimated from preliminary survey maps is 149 degrees.6 +/- 0 degrees.2(stats.) in equatorial coordinates. The instrumental temperature-to-polarization (T -> P) leakage fraction, inferred from per-detector demodulated Jupiter scan data, has a monopole component at the level of 1.7 x 10-3, a dipole component with an amplitude of 4.3 x 10-3, with no evidence of quadrupolar leakage.
  • No Thumbnail Available
    Item
    Four-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: On-sky Receiver Performance at 40, 90, 150, and 220 GHz Frequency Bands
    (2022) Dahal, Sumit; Appel, John W.; Datta, Rahul; Brewer, Michael K.; Ali, Aamir; Bennett, Charles L.; Bustos, Ricardo; Chan, Manwei; Chuss, David T.; Cleary, Joseph; Couto, Jullianna D.; Denis, Kevin L.; Dunner, Rolando; Eimer, Joseph; Espinoza, Francisco; Essinger-Hileman, Thomas; Golec, Joseph E.; Harrington, Kathleen; Helson, Kyle; Iuliano, Jeffrey; Karakla, John; Li, Yunyang; Marriage, Tobias A.; McMahon, Jeffrey J.; Miller, Nathan J.; Novack, Sasha; Nunez, Carolina; Osumi, Keisuke; Padilla, Ivan L.; Palma, Gonzalo A.; Parker, Lucas; Petroff, Matthew A.; Reeves, Rodrigo; Rhoades, Gary; Rostem, Karwan; Valle, Deniz A. N.; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Xu, Zhilei
    The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized cosmic microwave background (CMB) over the angular scales of 1 degrees less than or similar to theta <= 90 degrees with the aim of characterizing primordial gravitational waves and cosmic reionization. We report on the on-sky performance of the CLASS Q-band (40 GHz), W-band (90 GHz), and dichroic G-band (150/220 GHz) receivers that have been operational at the CLASS site in the Atacama desert since 2016 June, 2018 May, and 2019 September, respectively. We show that the noise-equivalent power measured by the detectors matches the expected noise model based on on-sky optical loading and lab-measured detector parameters. Using Moon, Venus, and Jupiter observations, we obtain power to antenna temperature calibrations and optical efficiencies for the telescopes. From the CMB survey data, we compute instantaneous array noise-equivalent-temperature sensitivities of 22, 19, 23, and 71 mu K-cmp root s for the 40, 90, 150, and 220 GHz frequency bands, respectively. These noise temperatures refer to white noise amplitudes, which contribute to sky maps at all angular scales. Future papers will assess additional noise sources impacting larger angular scales.
  • No Thumbnail Available
    Item
    The Atacama Cosmology Telescope: a measurement of the Cosmic Microwave Background power spectra at 98 and 150 GHz
    (2020) Choi, Steve K.; Hasselfield, Matthew; Ho, Shuay-Pwu Patty; Koopman, Brian; Lungu, Marius; Abitbol, Maximilian H.; Addison, Graeme E.; Ade, Peter A. R.; Aiola, Simone; Alonso, David; Amiri, Mandana; Amodeo, Stefania; Angile, Elio; Austermann, Jason E.; Baildon, Taylor; Battaglia, Nick; Beall, James A.; Bean, Rachel; Becker, Daniel T.; Bond, J. Richard; Bruno, Sarah Marie; Calabrese, Erminia; Calafut, Victoria; Campusano, Luis E.; Carrero, Felipe; Chesmore, Grace E.; Cho, Hsiao-mei; Clark, Susan E.; Cothard, Nicholas F.; Crichton, Devin; Crowley, Kevin T.; Darwish, Omar; Datta, Rahul; Denison, Edward, V; Devlin, Mark J.; Duell, Cody J.; Duff, Shannon M.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Dunner, Rolando; Essinger-Hileman, Thomas; Fankhanel, Max; Ferraro, Simone; Fox, Anna E.; Fuzia, Brittany; Gallardo, Patricio A.; Gluscevic, Vera; Golec, Joseph E.; Grace, Emily; Gralla, Megan; Guan, Yilun; Hall, Kirsten; Halpern, Mark; Han, Dongwon; Hargrave, Peter; Henderson, Shawn; Hensley, Brandon; Hill, J. Colin; Hilton, Gene C.; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Hubmayr, Johannes; Huffenberger, Kevin M.; Hughes, John P.; Infante, Leopoldo; Irwin, Kent; Jackson, Rebecca; Klein, Jeff; Knowles, Kenda; Kosowsky, Arthur; Lakey, Vincent; Li, Dale; Li, Yaqiong; Li, Zack; Lokken, Martine; Louis, Thibaut; MacInnis, Amanda; Madhavacheril, Mathew; Maldonado, Felipe; Mallaby-Kay, Maya; Marsden, Danica; Maurin, Loic; McMahon, Jeff; Menanteau, Felipe; Moodley, Kavilan; Morton, Tim; Naess, Sigurd; Namikawa, Toshiya; Nati, Federico; Newburgh, Laura; Nibarger, John P.; Nicola, Andrina; Niemack, Michael D.; Nolta, Michael R.; Orlowski-Sherer, John; Page, Lyman A.; Pappas, Christine G.; Partridge, Bruce; Phakathi, Phumlani; Prince, Heather; Puddu, Roberto; Qu, Frank J.; Rivera, Jesus; Robertson, Naomi; Rojas, Felipe; Salatino, Maria; Schaan, Emmanuel; Schillaci, Alessandro; Schmitt, Benjamin L.; Sehgal, Neelima; Sherwin, Blake D.; Sierra, Carlos; Sievers, Jon; Sifon, Cristobal; Sikhosana, Precious; Simon, Sara; Spergel, David N.; Staggs, Suzanne T.; Stevens, Jason; Storer, Emilie; Sunder, Dhaneshwar D.; Switzer, Eric R.; Thorne, Ben; Thornton, Robert; Trac, Hy; Treu, Jesse; Tucker, Carole; Vale, Leila R.; Van Engelen, Alexander; Van Lanen, Jeff; Vavagiakis, Eve M.; Wagoner, Kasey; Wang, Yuhan; Ward, Jonathan T.; Wollack, Edward J.; Xu, Zhilei; Zago, Fernando; Zhu, Ningfeng
    We present the temperature and polarization angular power spectra of the CMB measured by the Atacama Cosmology Telescope (ACT) from 5400 deg(2) of the 2013-2016 survey, which covers >15000 deg(2) at 98 and 150 GHz. For this analysis we adopt a blinding strategy to help avoid confirmation bias and, related to this, show numerous checks for systematic error done before unblinding. Using the likelihood for the cosmological analysis we constrain secondary sources of anisotropy and foreground emission, and derive a "CMB-only" spectrum that extends to l = 4000. At large angular scales, foreground emission at 150 GHz is similar to 1% of TT and EE within our selected regions and consistent with that found by Planck. Using the same likelihood, we obtain the cosmological parameters for Lambda CDM for the ACT data alone with a prior on the optical depth of tau = 0.065 +/- 0.015. Lambda CDM is a good fit. The best-fit model has a reduced chi(2) of 1.07 (PTE = 0.07) with H-0 = 67.9 +/- 1.5 km/s/Mpc. We show that the lensing BB signal is consistent with Lambda CDM and limit the celestial EB polarization angle to psi(P) = 0.07 degrees +/- 0.09 degrees. We directly cross correlate ACT with Planck and observe generally good agreement but with some discrepancies in TE. All data on which this analysis is based will be publicly released.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    The Atacama Cosmology Telescope: DR4 maps and cosmological parameters
    (2020) Aiola, Simone; Calabrese, Erminia; Maurin, Loic; Naess, Sigurd; Schmitt, Benjamin L.; Abitbol, Maximilian H.; Addison, Graeme E.; Ade, Peter A. R.; Alonso, David; Amiri, Mandana; Amodeo, Stefania; Angile, Elio; Austermann, Jason E.; Baildon, Taylor; Battaglia, Nick; Beall, James A.; Bean, Rachel; Becker, Daniel T.; Bond, J. Richard; Bruno, Sarah Marie; Calafut, Victoria; Campusano, Luis E.; Carrero, Felipe; Chesmore, Grace E.; Cho, Hsiao-mei; Choi, Steve K.; Clark, Susan E.; Cothard, Nicholas F.; Crichton, Devin; Crowley, Kevin T.; Darwish, Omar; Datta, Rahul; Denison, Edward, V; Devlin, Mark J.; Duell, Cody J.; Duff, Shannon M.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Dunner, Rolando; Essinger-Hileman, Thomas; Fankhanel, Max; Ferraro, Simone; Fox, Anna E.; Fuzia, Brittany; Gallardo, Patricio A.; Gluscevic, Vera; Golec, Joseph E.; Grace, Emily; Gralla, Megan; Guan, Yilun; Hall, Kirsten; Halpern, Mark; Han, Dongwon; Hargrave, Peter; Hasselfield, Matthew; Helton, Jakob M.; Henderson, Shawn; Hensley, Brandon; Hill, J. Colin; Hilton, Gene C.; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Ho, Shuay-Pwu Patty; Hubmayr, Johannes; Huffenberger, Kevin M.; Hughes, John P.; Infante, Leopoldo; Irwin, Kent; Jackson, Rebecca; Klein, Jeff; Knowles, Kenda; Koopman, Brian; Kosowsky, Arthur; Lakey, Vincent; Li, Dale; Li, Yaqiong; Li, Zack; Lokken, Martine; Louis, Thibaut; Lungu, Marius; MacInnis, Amanda; Madhavacheril, Mathew; Maldonado, Felipe; Mallaby-Kay, Maya; Marsden, Danica; McMahon, Jeff; Menanteau, Felipe; Moodley, Kavilan; Morton, Tim; Namikawa, Toshiya; Nati, Federico; Newburgh, Laura; Nibarger, John P.; Nicola, Andrina; Niemack, Michael D.; Nolta, Michael R.; Orlowski-Sherer, John; Page, Lyman A.; Pappas, Christine G.; Partridge, Bruce; Phakathi, Phumlani; Pisano, Giampaolo; Prince, Heather; Puddu, Roberto; Qu, Frank J.; Rivera, Jesus; Robertson, Naomi; Rojas, Felipe; Salatino, Maria; Schaan, Emmanuel; Schillaci, Alessandro; Sehgal, Neelima; Sherwin, Blake D.; Sierra, Carlos; Sievers, Jon; Sifon, Cristobal; Sikhosana, Precious; Simon, Sara; Spergel, David N.; Staggs, Suzanne T.; Stevens, Jason; Storer, Emilie; Sunder, Dhaneshwar D.; Switzer, Eric R.; Thorne, Ben; Thornton, Robert; Hy Trac; Treu, Jesse; Tucker, Carole; Vale, Leila R.; Van Engelen, Alexander; Van Lanen, Jeff; Vavagiakis, Eve M.; Wagoner, Kasey; Wang, Yuhan; Ward, Jonathan T.; Wollack, Edward J.; Xu, Zhilei; Zago, Fernando; Zhu, Ningfeng
    We present new arcminute-resolution maps of the Cosmic Microwave Background temperature and polarization anisotropy from the Atacama Cosmology Telescope, using data taken from 2013-2016 at 98 and 150 GHz. The maps cover more than 17,000 deg(2), the deepest 600 deg(2) with noise levels below 10 mu K-arcmin. We use the power spectrum derived from almost 6,000 deg(2) of these maps to constrain cosmology. The ACT data enable a measurement of the angular scale of features in both the divergence-like polarization and the temperature anisotropy, tracing both the velocity and density at last-scattering. From these one can derive the distance to the last-scattering surface and thus infer the local expansion rate, H-0. By combining ACT data with large-scale information from WMAP we measure H-0 = 67.6 +/- 1.1 km/s/Mpc, at 68% confidence, in excellent agreement with the independently-measured Planck satellite estimate (from ACT alone we find H-0 = 67.9 +/- 1.5 km/s/Mpc). The Lambda CDM model provides a good fit to the ACT data, and we find no evidence for deviations: both the spatial curvature, and the departure from the standard lensing signal in the spectrum, are zero to within 1 sigma; the number of relativistic species, the primordial Helium fraction, and the running of the spectral index are consistent with Lambda CDM predictions to within 1.5-2.2 sigma. We compare ACT, WMAP, and Planck at the parameter level and find good consistency; we investigate how the constraints on the correlated spectral index and baryon density parameters readjust when adding CMB large-scale information that ACT does not measure. The DR4 products presented here will be publicly released on the NASA Legacy Archive for Microwave Background Data Analysis.
  • No Thumbnail Available
    Item
    Two Year Cosmology Large Angular Scale Surveyor (CLASS) Observations: Long Timescale Stability Achieved with a Front-end Variable-delay Polarization Modulator at 40 GHz
    (2021) Harrington, Kathleen; Datta, Rahul; Osumi, Keisuke; Ali, Aamir; Appel, John W.; Bennett, Charles L.; Brewer, Michael K.; Bustos, Ricardo; Chan, Manwei; Chuss, David T.; Cleary, Joseph; Couto, Jullianna Denes; Dahal, Sumit; Dunner, Rolando; Eimer, Joseph R.; Essinger-Hileman, Thomas; Hubmayr, Johannes; Espinoza Inostroza, Francisco Raul; Iuliano, Jeffrey; Karakla, John; Li, Yunyang; Marriage, Tobias A.; Miller, Nathan J.; Nunez, Carolina; Padilla, Ivan L.; Parker, Lucas; Petroff, Matthew A.; Pradenas Marquez, Bastian; Reeves, Rodrigo; Fluxa Rojas, Pedro; Rostem, Karwan; Valle, Deniz Augusto Nunes; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Xu, Zhilei
    The Cosmology Large Angular Scale Surveyor (CLASS) is a four-telescope array observing the largest angular scales (2 less than or similar to l less than or similar to 200) of the cosmic microwave background (CMB) polarization. These scales encode information about reionization and inflation during the early universe. The instrument stability necessary to observe these angular scales from the ground is achieved through the use of a variable-delay polarization modulator as the first optical element in each of the CLASS telescopes. Here, we develop a demodulation scheme used to extract the polarization timestreams from the CLASS data and apply this method to selected data from the first 2 yr of observations by the 40GHz CLASS telescope. These timestreams are used to measure the 1/f noise and temperature-to-polarization (T -> P) leakage present in the CLASS data. We find a median knee frequency for the pair-differenced demodulated linear polarization of 15.12 mHz and a T -> P leakage of <3.8 x 10(-4) (95% confidence) across the focal plane. We examine the sources of 1/f noise present in the data and find the component of 1/f due to atmospheric precipitable water vapor (PWV) has an amplitude of 203 +/- 12 mu K-RJ root s for 1 mm of PWV when evaluated at 10 mHz; accounting for similar to 17% of the 1/f noise in the central pixels of the focal plane. The low levels of T -> P leakage and 1/f noise achieved through the use of a front-end polarization modulator are requirements for observing of the largest angular scales of the CMB polarization by the CLASS telescopes.