The FIRST Survey: Faint Images of the Radio Sky at twenty centimeters
TL;DR: The first year of the First Radio Sky at Twenty centimeters (FIRST) survey as discussed by the authors was performed using the NRAO Very Large Array (VLA) with a total of 144 hr of time in 1993 April and May was used for a variety of tests, as well as to cover an initial strip of the survey extending between 07{sup h}15{sup m} and 16{suph}30{supm} in a 2{sq_bullet}8 wide declination zone passing through the local zenith.
Abstract: The FIRST survey to produce Faint Images of the Radio Sky at Twenty centimeters is now underway using the NRAO Very Large Array. We describe here the scientific motivation for a large-area sky survey at radio frequencies which has a sensitivity and angular resolution comparable to the Palomar Observatory Sky Survey, and we recount the history that led to the current survey project. The technical design of the survey is covered in detail, including a description and justification of the grid pattern chosen, the rationale behind the integration time and angular resolution selected, and a summary of the other considerations which informed our planning for the project. A comprehensive description of the automated data analysis pipeline we have developed is presented. We also report here the results of the first year of FIRST observations. A total of 144 hr of time in 1993 April and May was used for a variety of tests, as well as to cover an initial strip of the survey extending between 07{sup h}15{sup m} and 16{sup h}30{sup m} in a 2{sq_bullet}8 wide declination zone passing through the local zenith (28.2{lt}{delta}{lt}31.0). A total of 2153 individual pointings yielded an image database containing 1039 merged images 46{sq_bullet}5{times}34{sq_bullet}5more » in extent with 1{center_dot}{double_prime}8 pixels and a typical rms of 0.13 mJy. A catalog derived from this 300 deg{sup 2} region contains 28,000 radio sources. We have performed extensive tests on the images and source list in order to establish the photometric and astrometric accuracy of these data products. We find systematic astrometric errors of {lt}0{center_dot}{double_prime}05; individual sources down to the 1 mJy survey flux density threshold have 90{percent} confidence error circles with radii of {lt}1{double_prime}. CLEAN bias introduces a systematic underestimate of point-source flux densities of {approximately}0.25 mJy; the bias is more severe for extended sources. (Abstract Truncated)« less
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TL;DR: The Sloan Digital Sky Survey (SDSS) as mentioned in this paper provides the data to support detailed investigations of the distribution of luminous and non-luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands.
Abstract: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey of the approximately one million brightest galaxies and 10^5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS, and serves as an introduction to extensive technical on-line documentation.
10,039 citations
Donald G. York1, Jennifer Adelman2, John E. Anderson2, Scott F. Anderson3 +148 more•Institutions (29)
TL;DR: The Sloan Digital Sky Survey (SDSS) as discussed by the authors provides the data to support detailed investigations of the distribution of luminous and non-luminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag.
Abstract: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag, and a spectroscopic survey of the approximately 106 brightest galaxies and 105 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS and serves as an introduction to extensive technical on-line documentation.
9,835 citations
Cites methods from "The FIRST Survey: Faint Images of t..."
...Stellar objects brighter than i′ =20 which are FIRST sources (Becker, White and Helfand 1995) are also selected....
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...Comparison with positions from the FIRST (Becker et al. 1995) and 2MASS (Skrutskie 1999) catalogues shows that the rms astrometric accuracy is currently better than 150 milliarcseconds (mas) in each coordinate....
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...The atlas images are sized to enclose the area occupied by each object plus the PSF width, or the object size given in the ROSAT or FIRST catalogues....
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...The photometric data products of the SDSS include: a catalog of all detected objects, with measured positions, magnitudes, shape parameters, model fits and processing flags; atlas images (i.e. cutouts from the imaging data in all five bands) of all detected objects and of objects from the FIRST and ROSAT catalogs; a 4× 4 binned image of the corrected images with the objects removed: and a mask of the areas of sky not processed (because of saturated stars, for example) and of corrected pixels (e.g. those from which cosmic rays were removed)....
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Kevork N. Abazajian1, Jennifer K. Adelman-McCarthy2, Marcel A. Agüeros3, S. Allam4 +220 more•Institutions (77)
TL;DR: A series of improvements to the spectroscopic reductions are described, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
Abstract: This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg^2 of imaging data, with most of the ~2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120° long, 2°.5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg^2. The survey has completed spectroscopy over 9380 deg^2; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
5,665 citations
Cites background from "The FIRST Survey: Faint Images of t..."
...Flux-limited samples of quasar candidates, selected by their nonstellar colors or FIRST (Becker et al. 1995) radio emission to i = 19.1 in regions of color space characteristic of z < 3 quasars, and to i = 20.2 for quasars with 3 < z < 5.5 (Richards et al. 2002)....
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TL;DR: The NRAO VLA Sky Survey (NVSS) covers the sky north of J2000 at 1.4 GHz as discussed by the authors, including a set of 2326 4?? 4? continuum cubes with three planes containing Stokes I, Q, and U images plus a catalog of almost 2? 106 discrete sources stronger than S 2.5 mJy.
Abstract: ?????The NRAO VLA Sky Survey (NVSS) covers the sky north of J2000.0 ? = -40? (82% of the celestial sphere) at 1.4 GHz. The principal data products are (1) a set of 2326 4? ? 4? continuum cubes with three planes containing Stokes I, Q, and U images plus (2) a catalog of almost 2 ? 106 discrete sources stronger than S ? 2.5 mJy. The images all have ? = 45'' FWHM resolution and nearly uniform sensitivity. Their rms brightness fluctuations are ? ? 0.45 mJy beam-1 ? 0.14 K (Stokes I) and ? ? 0.29 mJy beam-1 ? 0.09 K (Stokes Q and U). The rms uncertainties in right ascension and declination vary from 1'' for the N ? 4 ? 105 sources stronger than 15 mJy to 7'' at the survey limit. The NVSS was made as a service to the astronomical community. All data products, user software, and updates are being released via the World Wide Web as soon as they are produced and verified.
5,441 citations