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  • 1
    Online-Ressource
    Online-Ressource
    Making maps of cosmic microwave background polarization for B -mode studies: the POLARBEAR example
    EDP Sciences ; 2017
    In:  Astronomy & Astrophysics Vol. 600 ( 2017-4), p. A60-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 600 ( 2017-4), p. A60-
    Kurzfassung: Analysis of cosmic microwave background (CMB) datasets typically requires some filtering of the raw time-ordered data. For instance, in the context of ground-based observations, filtering is frequently used to minimize the impact of low frequency noise, atmospheric contributions and/or scan synchronous signals on the resulting maps. In this work we have explicitly constructed a general filtering operator, which can unambiguously remove any set of unwanted modes in the data, and then amend the map-making procedure in order to incorporate and correct for it. We show that such an approach is mathematically equivalent to the solution of a problem in which the sky signal and unwanted modes are estimated simultaneously and the latter are marginalized over. We investigated the conditions under which this amended map-making procedure can render an unbiased estimate of the sky signal in realistic circumstances. We then discuss the potential implications of these observations on the choice of map-making and power spectrum estimation approaches in the context of B -mode polarization studies. Specifically, we have studied the effects of time-domain filtering on the noise correlation structure in the map domain, as well as impact it may haveon the performance of the popular pseudo-spectrum estimators. We conclude that although maps produced by the proposed estimators arguably provide the most faithful representation of the sky possible given the data, they may not straightforwardly lead to the best constraints on the power spectra of the underlying sky signal and special care may need to be taken to ensure this is the case. By contrast, simplified map-makers which do not explicitly correct for time-domain filtering, but leave it to subsequent steps in the data analysis, may perform equally well and be easier and faster to implement. We focused on polarization-sensitive measurements targeting the B -mode component of the CMB signal and apply the proposed methods to realistic simulations based on characteristics of an actual CMB polarization experiment, POLARBEAR. Our analysis and conclusions are however more generally applicable.
    Materialart: Online-Ressource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201629467
    RVK:
    UA 1000
    RVK:
    US 1090
    Sprache: Englisch
    Verlag: EDP Sciences
    Publikationsdatum: 2017
    ZDB Id: 1458466-9
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
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    Target Selection and Validation of DESI Quasars
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Vol. 944, No. 1 ( 2023-02-01), p. 107-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 944, No. 1 ( 2023-02-01), p. 107-
    Kurzfassung: The Dark Energy Spectroscopic Instrument (DESI) survey will measure large-scale structures using quasars as direct tracers of dark matter in the redshift range 0.9 〈 z 〈 2.1 and using Ly α forests in quasar spectra at z 〉 2.1. We present several methods to select candidate quasars for DESI, using input photometric imaging in three optical bands ( g , r , z ) from the DESI Legacy Imaging Surveys and two infrared bands (W1, W2) from the Wide-field Infrared Survey Explorer. These methods were extensively tested during the Survey Validation of DESI. In this paper, we report on the results obtained with the different methods and present the selection we optimized for the DESI main survey. The final quasar target selection is based on a random forest algorithm and selects quasars in the magnitude range of 16.5 〈 r 〈 23. Visual selection of ultra-deep observations indicates that the main selection consists of 71% quasars, 16% galaxies, 6% stars, and 7% inconclusive spectra. Using the spectra based on this selection, we build an automated quasar catalog that achieves a fraction of true QSOs higher than 99% for a nominal effective exposure time of ∼1000 s. With a 310 deg −2 target density, the main selection allows DESI to select more than 200 deg −2 quasars (including 60 deg −2 quasars with z 〉 2.1), exceeding the project requirements by 20%. The redshift distribution of the selected quasars is in excellent agreement with quasar luminosity function predictions.
    Materialart: Online-Ressource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/acb3c2
    RVK:
    UA 1000
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2023
    ZDB Id: 2207648-7
    ZDB Id: 1473835-1
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    Online-Ressource
    The Robotic Multiobject Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)
    American Astronomical Society ; 2023
    In:  The Astronomical Journal Vol. 165, No. 1 ( 2023-01-01), p. 9-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 165, No. 1 ( 2023-01-01), p. 9-
    Kurzfassung: A system of 5020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically retarget their optical fibers every 10–20 minutes, each to a precision of several microns, with a reconfiguration time of fewer than 2 minutes. Over the next 5 yr, they will enable the newly constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5020 robotic positioners and optical fibers, DESI’s Focal Plane System includes six guide cameras, four wave front cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multiobject, fiber-fed spectrographs.
    Materialart: Online-Ressource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac9ab1
    RVK:
    US 1090
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2023
    ZDB Id: 2207625-6
    ZDB Id: 2003104-X
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    The Target-selection Pipeline for the Dark Energy Spectroscopic Instrument
    American Astronomical Society ; 2023
    In:  The Astronomical Journal Vol. 165, No. 2 ( 2023-02-01), p. 50-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 165, No. 2 ( 2023-02-01), p. 50-
    Kurzfassung: In 2021 May, the Dark Energy Spectroscopic Instrument (DESI) began a 5 yr survey of approximately 50 million total extragalactic and Galactic targets. The primary DESI dark-time targets are emission line galaxies, luminous red galaxies, and quasars. In bright time, DESI will focus on two surveys known as the Bright Galaxy Survey and the Milky Way Survey. DESI also observes a selection of “secondary” targets for bespoke science goals. This paper gives an overview of the publicly available pipeline ( desitarget ) used to process targets for DESI observations. Highlights include details of the different DESI survey targeting phases, the targeting ID ( TARGETID ) used to define unique targets, the bitmasks used to indicate a particular type of target, the data model and structure of DESI targeting files, and examples of how to access and use the desitarget code base. This paper will also describe “supporting” DESI target classes, such as standard stars, sky locations, and random catalogs that mimic the angular selection function of DESI targets. The DESI target-selection pipeline is complex and sizable; this paper attempts to summarize the most salient information required to understand and work with DESI targeting data.
    Materialart: Online-Ressource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/aca5f9
    RVK:
    US 1090
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2023
    ZDB Id: 2207625-6
    ZDB Id: 2003104-X
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 5
    Online-Ressource
    Online-Ressource
    The DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation
    American Astronomical Society ; 2023
    In:  The Astronomical Journal Vol. 165, No. 6 ( 2023-06-01), p. 253-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 165, No. 6 ( 2023-06-01), p. 253-
    Kurzfassung: Over the next 5 yr, the Dark Energy Spectroscopic Instrument (DESI) will use 10 spectrographs with 5000 fibers on the 4 m Mayall Telescope at Kitt Peak National Observatory to conduct the first Stage IV dark energy galaxy survey. At z 〈 0.6, the DESI Bright Galaxy Survey (BGS) will produce the most detailed map of the universe during the dark-energy-dominated epoch with redshifts of 〉 10 million galaxies spanning 14,000 deg 2 . In this work, we present and validate the final BGS target selection and survey design. From the Legacy Surveys, BGS will target an r 〈 19.5 mag limited sample (BGS Bright), a fainter 19.5 〈 r 〈 20.175 color-selected sample (BGS Faint), and a smaller low- z quasar sample. BGS will observe these targets using exposure times scaled to achieve homogeneous completeness and cover the footprint three times. We use observations from the Survey Validation programs conducted prior to the main survey along with simulations to show that BGS can complete its strategy and make optimal use of “bright” time. BGS targets have stellar contamination 〈 1%, and their densities do not depend strongly on imaging properties. BGS Bright will achieve 〉 80% fiber assignment efficiency. Finally, BGS Bright and BGS Faint will achieve 〉 95% redshift success over any observing condition. BGS meets the requirements for an extensive range of scientific applications. BGS will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z 〈 0.4. It presents opportunities for new methods that require highly complete and dense samples (e.g., N -point statistics, multitracers). BGS further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter.
    Materialart: Online-Ressource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/accff8
    RVK:
    US 1090
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2023
    ZDB Id: 2207625-6
    ZDB Id: 2003104-X
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 6
    Online-Ressource
    Online-Ressource
    CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
    American Astronomical Society ; 2022
    In:  The Astrophysical Journal Vol. 926, No. 1 ( 2022-02-01), p. 54-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 926, No. 1 ( 2022-02-01), p. 54-
    Kurzfassung: CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r , in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2–3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r 〉 0.003 at greater than 5 σ , or in the absence of a detection, of reaching an upper limit of r 〈 0.001 at 95% CL.
    Materialart: Online-Ressource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/ac1596
    RVK:
    UA 1000
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2022
    ZDB Id: 2207648-7
    ZDB Id: 1473835-1
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    Overview of the DESI Milky Way Survey
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Vol. 947, No. 1 ( 2023-04-01), p. 37-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 947, No. 1 ( 2023-04-01), p. 37-
    Kurzfassung: We describe the Milky Way Survey (MWS) that will be undertaken with the Dark Energy Spectroscopic Instrument (DESI) on the Mayall 4 m telescope at the Kitt Peak National Observatory. Over the next 5 yr DESI MWS will observe approximately seven million stars at Galactic latitudes ∣ b ∣ 〉 20°, with an inclusive target selection scheme focused on the thick disk and stellar halo. MWS will also include several high-completeness samples of rare stellar types, including white dwarfs, low-mass stars within 100 pc of the Sun, and horizontal branch stars. We summarize the potential of DESI to advance understanding of the Galactic structure and stellar evolution. We introduce the final definitions of the main MWS target classes and estimate the number of stars in each class that will be observed. We describe our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances. We use ≃500,000 spectra of unique stellar targets from the DESI Survey Validation program (SV) to demonstrate that our pipelines can measure radial velocities to ≃1 km s −1 and [Fe/H] accurate to ≃0.2 dex for typical stars in our main sample. We find the stellar parameter distributions from ≈100 deg 2 of SV observations with ≳90% completeness on our main sample are in good agreement with expectations from mock catalogs and previous surveys.
    Materialart: Online-Ressource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/acb3c0
    RVK:
    UA 1000
    Sprache: Unbekannt
    Verlag: American Astronomical Society
    Publikationsdatum: 2023
    ZDB Id: 2207648-7
    ZDB Id: 1473835-1
    SSG: 16,12
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Online-Ressource
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