Topic
Celestial pole
About: Celestial pole is a research topic. Over the lifetime, 212 publications have been published within this topic receiving 3638 citations.
Papers published on a yearly basis
Papers
ASTRON1, Open University of Israel2, Rhodes University3, University of the Western Cape4, California Institute of Technology5, University College London6, Imperial College London7, Max Planck Society8, University of Colorado Boulder9, University of Sussex10, Stockholm University11, Kapteyn Astronomical Institute12, Leiden University13
TL;DR: In this paper, the authors present the first limits on the Epoch of Reionization 21 cm H I power spectra, in the redshift range z = 7.9 −10.6, using the Low-Frequency Array (LOFAR) High-Band Antenna (HBA).
Abstract: We present the first limits on the Epoch of Reionization 21 cm H I power spectra, in the redshift range z = 7.9–10.6, using the Low-Frequency Array (LOFAR) High-Band Antenna (HBA). In total, 13.0 hr of data were used from observations centered on the North Celestial Pole. After subtraction of the sky model and the noise bias, we detect a non-zero Δ^2_I = (56 ± 13 mK)^2 (1-σ) excess variance and a best 2-σ upper limit of Δ^2_(21) < (79.6 mK)^2 at k = 0.053 h cMpc^(−1) in the range z = 9.6–10.6. The excess variance decreases when optimizing the smoothness of the direction- and frequency-dependent gain calibration, and with increasing the completeness of the sky model. It is likely caused by (i) residual side-lobe noise on calibration baselines, (ii) leverage due to nonlinear effects, (iii) noise and ionosphere-induced gain errors, or a combination thereof. Further analyses of the excess variance will be discussed in forthcoming publications.
300 citations
TL;DR: In this article, microwave background observations at the Owens Valley Radio Observatory were used to detect intrinsic anisotropy on scales of 7'-22' after point-source removal, and significant emission with temperature spectral index? -2 toward the north celestial pole (NCP).
Abstract: We present results from microwave background observations at the Owens Valley Radio Observatory. These observations, at 14.5 and 32 GHz, are designed to detect intrinsic anisotropy on scales of 7'-22'. After point-source removal, we detect significant emission with temperature spectral index ? -2 toward the north celestial pole (NCP). Comparison of our data with the IRAS 100 ?m map of the same fields reveals a strong correlation between this emission and the infrared dust emission. From the lack of detectable H? emission, we conclude that the signals are consistent either with flat-spectrum synchrotron radiation or with free-free emission from Te 106 K gas, probably associated with a large H I feature known as the NCP Loop. Assuming ? = -2.2, our data indicate a conversion Tf/I100?m = 7.5 ? 10-2?$−2.2{r GHz}$ --> K (MJy sr-1)-1. The detection of such a component suggests that we should be cautious in any assumptions made regarding foregrounds when designing experiments to map the microwave background radiation.
279 citations
TL;DR: The Yale/San Juan Southern Proper Motion Catalog (SPM4) as mentioned in this paper contains absolute proper motions, celestial coordinates, and (B,V) photometry for over 103 million stars and galaxies between the south celestial pole and -20 deg declination.
Abstract: We present the fourth installment of the Yale/San Juan Southern Proper Motion Catalog, SPM4. The SPM4 contains absolute proper motions, celestial coordinates, and (B,V) photometry for over 103 million stars and galaxies between the south celestial pole and -20 deg declination. The catalog is roughly complete to V=17.5 and is based on photographic and CCD observations taken with the Yale Southern Observatory's double-astrograph at Cesco Observatory in El Leoncito, Argentina. The proper-motion precision, for well-measured stars, is estimated to be 2 to 3 mas/yr, depending on the type of second-epoch material. At the bright end, proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, while the faint end is anchored to the inertial system using external galaxies. Systematic uncertainties in the absolute proper motions are on the order of 1 mas/yr.
187 citations
TL;DR: The Yale/San Juan Southern Proper Motion Catalog (SPM4) as mentioned in this paper contains absolute proper motions, celestial coordinates, and B, V photometry for over 103 million stars and galaxies between the south celestial pole and -20{sup 0} declination.
Abstract: We present the fourth installment of the Yale/San Juan Southern Proper Motion Catalog, SPM4. The SPM4 contains absolute proper motions, celestial coordinates, and B, V photometry for over 103 million stars and galaxies between the south celestial pole and -20{sup 0} declination. The catalog is roughly complete to V = 17.5 and is based on photographic and CCD observations taken with the Yale Southern Observatory's double astrograph at Cesco Observatory in El Leoncito, Argentina. The proper-motion precision, for well-measured stars, is estimated to be 2-3 mas yr{sup -1}, depending on the type of second-epoch material. At the bright end, proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, while the faint end is anchored to the inertial system using external galaxies. Systematic uncertainties in the absolute proper motions are on the order of 1 mas yr{sup -1}.
180 citations
ASTRON1, Kapteyn Astronomical Institute2, Mount Stromlo Observatory3, Harvard University4, Max Planck Society5, University of Colorado Boulder6, Stockholm University7, Leiden University8, University College London9, Space Telescope Science Institute10, Netherlands Institute for Space Research11, Chalmers University of Technology12, University of Southampton13, University of Sydney14, Jacobs University Bremen15, University of Hamburg16, Radboud University Nijmegen17, University of Nice Sophia Antipolis18, Centre national de la recherche scientifique19, University of Manchester20, University of Amsterdam21, Ruhr University Bochum22, University of Oxford23, Lebedev Physical Institute24, Center for Information Technology25, Rhodes University26
TL;DR: In this article, the authors present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz.
Abstract: The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP.
164 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 3 |
| 2020 | 2 |
| 2019 | 11 |
| 2018 | 5 |
| 2017 | 4 |
| 2016 | 6 |