ORCID Profile
0000-0003-2606-9340
Current Organisations
University of Colorado at Boulder
,
University of Colorado
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Publisher: American Astronomical Society
Date: 31-08-2020
Publisher: American Physical Society (APS)
Date: 13-07-2021
Publisher: American Physical Society (APS)
Date: 26-01-2021
Publisher: EDP Sciences
Date: 09-2010
Publisher: American Astronomical Society
Date: 08-2022
Abstract: We provide the first combined cosmological analysis of the South Pole Telescope (SPT) and Planck cluster catalogs. The aim is to provide an independent calibration for Planck scaling relations, exploiting the cosmological constraining power of the SPT-SZ cluster catalog and its dedicated weak lensing (WL) and X-ray follow-up observations. We build a new version of the Planck cluster likelihood. In the ν Λ CDM scenario, focusing on the mass slope and mass bias of Planck scaling relations, we find α SZ = 1.49 − 0.10 + 0.07 and 1 − b SZ = 0.69 − 0.14 + 0.07 , respectively. The results for the mass slope show a ∼4 σ departure from the self-similar evolution, α SZ ∼ 1.8. This shift is mainly driven by the matter density value preferred by SPT data, Ω m = 0.30 ± 0.03, lower than the one obtained by Planck data alone, Ω m = 0.37 − 0.06 + 0.02 . The mass bias constraints are consistent both with outcomes of hydrodynamical simulations and external WL calibrations, (1 − b ) ∼ 0.8, and with results required by the Planck cosmic microwave background cosmology, (1 − b ) ∼ 0.6. From this analysis, we obtain a new catalog of Planck cluster masses M 500 . We estimate the ratio between the published Planck M SZ masses and our derived masses M 500 , as a “measured mass bias,” 1 − b M . We analyze the mass, redshift, and detection noise dependence of 1 − b M , finding an increasing trend toward high redshift and low mass. These results mimic the effect of departure from self-similarity in cluster evolution, showing different dependencies for the low-mass, high-mass, low- z , and high- z regimes.
Publisher: Oxford University Press (OUP)
Date: 19-07-2018
Abstract: The use of galaxy clusters as precision cosmological probes relies on an accurate determination of their masses. However, inferring the relationship between cluster mass and observables from direct observations is difficult and prone to s le selection biases. In this work, we use weak lensing as the best possible proxy for cluster mass to calibrate the Sunyaev–Zel’dovich (SZ) effect measurements from the APEX-SZ experiment. For a well-defined (ROSAT) X-ray complete cluster s le, we calibrate the integrated Comptonization parameter, YSZ, to the weak-lensing derived total cluster mass, M500. We employ a novel Bayesian approach to account for the selection effects by jointly fitting both the SZ Comptonization, YSZ–M500, and the X-ray luminosity, Lx–M500, scaling relations. We also account for a possible correlation between the intrinsic (lognormal) scatter of Lx and YSZ at fixed mass. We find the corresponding correlation coefficient to be $r= 0.47_{-0.35}^{+0.24}$, and at the current precision level our constraints on the scaling relations are consistent with previous works. For our APEX-SZ s le, we find that ignoring the covariance between the SZ and X-ray observables biases the normalization of the YSZ–M500 scaling high by 1–2σ and the slope low by ∼1σ, even when the SZ effect plays no role in the s le selection. We conclude that for higher precision data and larger cluster s les, as anticipated from on-going and near-future cluster cosmology experiments, similar biases (due to intrinsic covariances of cluster observables) in the scaling relations will dominate the cosmological error budget if not accounted for correctly.
Publisher: American Astronomical Society
Date: 07-2020
Publisher: American Physical Society (APS)
Date: 02-04-2014
Publisher: American Physical Society (APS)
Date: 08-12-2015
Publisher: American Astronomical Society
Date: 02-2022
Abstract: We present component-separated maps of the primary cosmic microwave background/kinematic Sunyaev–Zel’dovich (SZ) litude and the thermal SZ Compton- y parameter, created using data from the South Pole Telescope (SPT) and the Planck satellite. These maps, which cover the ∼2500 deg 2 of the southern sky imaged by the SPT-SZ survey, represent a significant improvement over previous such products available in this region by virtue of their higher angular resolution ( 1 .′ 25 for our highest-resolution Compton- y maps) and lower noise at small angular scales. In this work we detail the construction of these maps using linear combination techniques, including our method for limiting the correlation of our lowest-noise Compton- y map products with the cosmic infrared background. We perform a range of validation tests on these data products to test our sky modeling and combination algorithms, and we find good performance in all of these tests. Recognizing the potential utility of these data products for a wide range of astrophysical and cosmological analyses, including studies of the gas properties of galaxies, groups, and clusters, we make these products publicly available at ublic/data/sptsz_ymap and on the NASA/LAMBDA website.
Publisher: American Astronomical Society
Date: 04-04-2013
Publisher: Elsevier BV
Date: 03-2015
Publisher: Springer Science and Business Media LLC
Date: 06-01-2016
Publisher: Springer Science and Business Media LLC
Date: 03-2013
DOI: 10.1038/NATURE12001
Abstract: In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the s le indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.
Publisher: Elsevier BV
Date: 03-2015
Publisher: American Astronomical Society
Date: 02-2021
Abstract: We report new measurements of millimeter-wave power spectra in the angular multipole range 2000 ≤ ℓ ≤ 11,000 (angular scales ). By adding 95 and 150 GHz data from the low-noise 500 deg 2 SPTpol survey to the SPT-SZ three-frequency 2540 deg 2 survey, we substantially reduce the uncertainties in these bands. These power spectra include contributions from the primary cosmic microwave background, cosmic infrared background, radio galaxies, and thermal and kinematic Sunyaev–Zel’dovich (SZ) effects. The data favor a thermal SZ (tSZ) power at 143 GHz of and a kinematic SZ (kSZ) power of . This is the first measurement of kSZ power at ≥3 σ . However, different assumptions about the CIB or SZ models can reduce the significance down to 2.4 σ in the worst case. We study the implications of the measured kSZ power for the epoch of reionization under the Calabrese et al. model for the kSZ power spectrum and find the duration of reionization to be ( at 95% confidence), when combined with our previously published tSZ bispectrum measurement. The upper limit tightens to if the assumed homogeneous kSZ power is increased by 25% (∼0.5 μ K 2 ) and relaxes to if the homogeneous kSZ power is decreased by the same amount.
Publisher: American Astronomical Society
Date: 22-06-2015
Publisher: Oxford University Press (OUP)
Date: 19-05-2022
Abstract: We search for the signature of cosmological shocks in stacked gas pressure profiles of galaxy clusters using data from the South Pole Telescope (SPT). Specifically, we stack the latest Compton-y maps from the 2500 deg2 SPT-SZ survey on the locations of clusters identified in that same data set. The s le contains 516 clusters with mean mass $\\langle M_{\\rm 200m}\\rangle = 10^{14.9} \\, {\\rm M}_\\odot$ and redshift 〈z〉 = 0.55. We analyse in parallel a set of zoom-in hydrodynamical simulations from the three hundred project. The SPT-SZ data show two features: (i) a pressure deficit at R/R200m = 1.08 ± 0.09, measured at 3.1σ significance and not observed in the simulations, and (ii) a sharp decrease in pressure at R/R200m = 4.58 ± 1.24 at 2.0σ significance. The pressure deficit is qualitatively consistent with a shock-induced thermal non-equilibrium between electrons and ions, and the second feature is consistent with accretion shocks seen in previous studies. We split the cluster s le by redshift and mass, and find both features exist in all cases. There are also no significant differences in features along and across the cluster major axis, whose orientation roughly points towards filamentary structure. As a consistency test, we also analyse clusters from the Planck and Atacama Cosmology Telescope Polarimeter surveys and find quantitatively similar features in the pressure profiles. Finally, we compare the accretion shock radius ($R_{\\rm sh,\\, acc}$) with existing measurements of the splashback radius (Rsp) for SPT-SZ and constrain the lower limit of the ratio, $R_{\\rm sh,\\, acc}/R_{\\rm sp}\\gt 2.16 \\pm 0.59$.
Publisher: American Astronomical Society
Date: 20-08-2012
Publisher: American Astronomical Society
Date: 18-02-2020
Publisher: American Astronomical Society
Date: 07-08-2009
Publisher: Springer Science and Business Media LLC
Date: 24-01-2012
Publisher: American Physical Society (APS)
Date: 04-10-2021
Publisher: American Astronomical Society
Date: 11-08-2015
Publisher: American Astronomical Society
Date: 27-05-2022
Abstract: We report an improved measurement of the degree-scale cosmic microwave background B -mode angular-power spectrum over 670 deg 2 sky area at 150 GHz with P olarbear . In the original analysis of the data, errors in the angle measurement of the continuously rotating half-wave plate, a polarization modulator, caused significant data loss. By introducing an angle-correction algorithm, the data volume is increased by a factor of 1.8. We report a new analysis using the larger data set. We find the measured B -mode spectrum is consistent with the ΛCDM model with Galactic dust foregrounds. We estimate the contamination of the foreground by cross-correlating our data and Planck 143, 217, and 353 GHz measurements, where its spectrum is modeled as a power law in angular scale and a modified blackbody in frequency. We place an upper limit on the tensor-to-scalar ratio r 0.33 at 95% confidence level after marginalizing over the foreground parameters.
Publisher: Springer Science and Business Media LLC
Date: 07-09-2018
Publisher: Springer Science and Business Media LLC
Date: 27-01-2020
DOI: 10.1007/S10909-019-02329-W
Abstract: Recent developments of transition-edge sensors (TESs), based on extensive experience in ground-based experiments, have been making the sensor techniques mature enough for their application on future satellite cosmic microwave background (CMB) polarization experiments. LiteBIRD is in the most advanced phase among such future satellites, targeting its launch in Japanese Fiscal Year 2027 (2027FY) with JAXA’s H3 rocket. It will accommodate more than 4000 TESs in focal planes of reflective low-frequency and refractive medium-and-high-frequency telescopes in order to detect a signature imprinted on the CMB by the primordial gravitational waves predicted in cosmic inflation. The total wide frequency coverage between 34 and 448 GHz enables us to extract such weak spiral polarization patterns through the precise subtraction of our Galaxy’s foreground emission by using spectral differences among CMB and foreground signals. Telescopes are cooled down to 5 K for suppressing thermal noise and contain polarization modulators with transmissive half-wave plates at in idual apertures for separating sky polarization signals from artificial polarization and for mitigating from instrumental 1/ f noise. Passive cooling by using V-grooves supports active cooling with mechanical coolers as well as adiabatic demagnetization refrigerators. Sky observations from the second Sun–Earth Lagrangian point, L2, are planned for 3 years. An international collaboration between Japan, the USA, Canada, and Europe is sharing various roles. In May 2019, the Institute of Space and Astronautical Science, JAXA, selected LiteBIRD as the strategic large mission No. 2.
Publisher: American Physical Society (APS)
Date: 02-10-2020
Publisher: American Astronomical Society
Date: 28-03-2013
Publisher: American Physical Society (APS)
Date: 09-07-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2013
Publisher: Springer Science and Business Media LLC
Date: 24-01-2012
Publisher: American Astronomical Society
Date: 30-08-2017
Publisher: American Astronomical Society
Date: 23-10-2017
Publisher: American Physical Society (APS)
Date: 22-06-2020
Publisher: American Astronomical Society
Date: 08-2021
Publisher: American Astronomical Society
Date: 16-08-2019
Publisher: American Astronomical Society
Date: 05-03-2020
Location: United States of America
No related grants have been discovered for NILS WILLIAM HALVERSON.