Faint Images of the Radio Sky at Twenty-Centimeters

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Faint Images of the Radio Sky at Twenty-Centimeters
VLA 4893505508.jpg
Part of the Karl G. Jansky Very Large Array
Alternative namesFIRST
Started1993  OOjs UI icon edit-ltr-progressive.svg
Ended2011  OOjs UI icon edit-ltr-progressive.svg
Wavelength 20 centimetre  OOjs UI icon edit-ltr-progressive.svg
Website sundog.stsci.edu
[ edit on Wikidata]

Faint Images of the Radio Sky at Twenty-Centimeters, or FIRST, was an astronomical survey of the Northern Hemisphere carried out by the Very Large Array. It was led by Robert H. Becker, Richard L. White, and David J. Helfand, who came up with the idea for the survey after they had completed the VLA Galactic Plane survey in 1990, [1] as well as Michael D. Gregg and Sally A. Laurent-Muehleisen. [2] The survey was started 50 years after the first systematic survey of the radio sky was completed by Grote Reber in April 1943. [3]

Contents

Survey

The survey covers 10,575 square degrees, [4] around 25% of the sky, [1] with regions centred on the North and South Galactic poles. The regions were chosen so that they would also be covered by the Sloan Digital Sky Survey (SDSS) in 5 optical bands, [5] and the survey was comparable to the Palomar Observatory Sky Survey in terms of resolution and sensitivity. [3]

The observations were made in 'B' configuration at a wavelength of 20 centimetres (1,500 MHz) (in the L Band), with an angular resolution of 5 arcsecond. [6] It was proposed at the same time as the NRAO VLA Sky Survey, and trial observations for both surveys were taken in 1992. Survey observations of the North Galactic pole started in 1993, [1] with 144 hours of observing time in April and May 1993 for test observations and the initial survey strip of 300 square degrees, producing an initial catalogue of 28,000 sources. [3] Survey observations continued until 2004. Observations of the South Galactic pole were made in 2009 and 2011; [5] the 2011 observations used the EVLA. [7] The target flux density limit was 1 milliJansky, with an <0.15mJy r.m.s. noise limit. [3]

The survey data was analysed using an automated pipeline through the Astronomical Image Processing System. [1] Images and catalogues from the survey were made available after quality checks, without a proprietary period. [8] Several versions of the survey catalogue have been generated, with the first published in 1997, [9] and the latest (as of 2017) published in December 2014. [4] The catalogue includes over 70,000 cross-identifications with SDSS and the Two Micron All Sky Survey (2MASS). [7] The expectation was that radio sources would be observed and 65,000 images produced by the survey; [1] the 2014 catalogue included 946,432 sources. [4] Sources in the catalogue follow a naming convention comprising the survey name and source coordinate with the format "FIRST Jhhmmss.s+ddmmss"; the convention is registered with the International Astronomical Union. [10]

Science

The resolution of the survey was chosen so that optical counterparts to the radio sources could be identified; complex radio sources with multiple components could be resolved (to avoid optical misidentifications); and radio morphology (e.g., Fanaroff-Riley classification) could be identified. [1] The survey aimed to contribute to science on quasars and active galaxies; galaxy evolution; galactic astronomy; the large-scale structure of the Universe; and dark matter. [1] The survey produced a series of papers. [11] The survey paper has been referenced by over 1,600 other scientific publications. [3]

The survey sources were cross-matched with the Palomar Sky Survey to create the FIRST Bright Quasar Survey (FBQS), which comprised quasar candidates that were then followed up with optical spectroscopy. The initial survey found 69 quasars, with 51 being newly identified. [12] A number of broad absorption line quasars were discovered by FIRST. [13] [14] Other, high-redshift quasars were identified in the survey by cross-matching with SDSS. [15]

Variability was detected in over 1600 sources during the course of the survey, including stars, pulsars, galaxies, quasars, and unidentified radio sources. [16] On large scales, the two-point correlation function between radio galaxies was observed. [17]

Related Research Articles

<span class="mw-page-title-main">Quasar</span> Active galactic nucleus containing a supermassive black hole

A quasar is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up because of friction and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.

An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess, non-stellar emissions have been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an active galaxy. The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy.

<span class="mw-page-title-main">Hubble Deep Field</span> Multiple exposure image of deep space in the constellation Ursa Major

The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995.

<span class="mw-page-title-main">Reionization</span> Process that caused matter to reionize early in the history of the Universe

In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages".

<span class="mw-page-title-main">Messier 77</span> Barred spiral galaxy in the constellation Cetus

Messier 77 (M77), also known as NGC 1068 or the Squid Galaxy, is a barred spiral galaxy in the constellation Cetus. It is about 47 million light-years (14 Mpc) away from Earth. Messier 77 was discovered by Pierre Méchain in 1780, who originally described it as a nebula. Méchain then communicated his discovery to Charles Messier, who subsequently listed the object in his catalog. Both Messier and William Herschel described this galaxy as a star cluster. Today, however, the object is known to be a galaxy.

In astronomical spectroscopy, the Gunn–Peterson trough is a feature of the spectra of quasars due to the presence of neutral hydrogen in the Intergalactic medium (IGM). The trough is characterized by suppression of electromagnetic emission from the quasar at wavelengths less than that of the Lyman-alpha line at the redshift of the emitted light. This effect was originally predicted in 1965 by James E. Gunn and Bruce Peterson.

A dark galaxy is a hypothesized galaxy with no stars. They received their name because they have no visible stars but may be detectable if they contain significant amounts of gas. Astronomers have long theorized the existence of dark galaxies, but there are no confirmed examples to date. Dark galaxies are distinct from intergalactic gas clouds caused by galactic tidal interactions, since these gas clouds do not contain dark matter, so they do not technically qualify as galaxies. Distinguishing between intergalactic gas clouds and galaxies is difficult; most candidate dark galaxies turn out to be tidal gas clouds. The best candidate dark galaxies to date include HI1225+01, AGC229385, and numerous gas clouds detected in studies of quasars.

<span class="mw-page-title-main">NGC 3226</span> Dwarf elliptical galaxy in the constellation Leo

NGC 3226 is a dwarf elliptical galaxy that is interacting with the spiral galaxy NGC 3227. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies. Both galaxies may be found in the constellation Leo. It is a member of the NGC 3227 Group of galaxies, which is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.

Kenneth Irwin Kellermann is an American astronomer at the National Radio Astronomy Observatory. He is best known for his work on quasars. He won the Helen B. Warner Prize for Astronomy of the American Astronomical Society in 1971, and the Bruce Medal of the Astronomical Society of the Pacific in 2014.

<span class="mw-page-title-main">APM 08279+5255</span> Quasar

APM 08279+5255 is a very distant, broad absorption line quasar located in the constellation Lynx. It is magnified and split into multiple images by the gravitational lensing effect of a foreground galaxy through which its light passes. It appears to be a giant elliptical galaxy with a supermassive black hole and associated accretion disk. It possesses large regions of hot dust and molecular gas, as well as regions with starburst activity.

<span class="mw-page-title-main">GRS 1915+105</span> Binary system in the constellation Aquila

GRS 1915+105 or V1487 Aquilae is an X-ray binary star system which features a regular star and a black hole. It was discovered on August 15, 1992 by the WATCH all-sky monitor aboard Granat. "GRS" stands for "GRANAT source", "1915" is the right ascension and "105" reflects the approximate declination. The near-infrared counterpart was confirmed by spectroscopic observations. The binary system lies 11,000 parsecs away in Aquila. GRS 1915+105 is the heaviest of the stellar black holes so far known in the Milky Way Galaxy, with 10 to 18 times the mass of the Sun. It is also a microquasar, and it appears that the black hole rotates at least 950 times per second, close to the maximum of 1,150 times per second, with a spin parameter value between 0.82 and 1.00.

<span class="mw-page-title-main">NGC 4698</span> Galaxy in the constellation Virgo

NGC 4698 is a barred spiral galaxy located around 55 million light years away from Earth in the constellation of Virgo. It belongs to the Virgo Cluster of galaxies and is positioned near the northeastern edge of this assemblage. The morphological classification of NGC 4698 in the De Vaucouleurs system is SA(s)ab, which indicates a purely spiral structure with moderate to tightly wound arms. It is inclined to the line of sight from the Earth by an angle of 53° along a position angle of 170°.

<span class="mw-page-title-main">NGC 708</span> Galaxy in the constellation Andromeda

NGC 708 is an elliptical galaxy located 240 million light-years away in the constellation Andromeda and was discovered by astronomer William Herschel on September 21, 1786. It is classified as a cD galaxy and is the brightest member of Abell 262. NGC 708 is a weak FR I radio galaxy and is also classified as a type 2 Seyfert galaxy.

<span class="mw-page-title-main">NGC 4055</span> Galaxy in the constellation Coma Berenices

NGC 4055 is an elliptical galaxy located 310 light-years away in the constellation Coma Berenices. It was discovered by astronomer William Herschel on April 27, 1785. It was rediscovered by John Herschel on April 29, 1832. It is listed both as NGC 4061 and NGC 4055. NGC 4055 is a member of the NGC 4065 Group and forms an interacting pair with its companion, NGC 4065 as evidenced by distortions in their optical isophotes.

<span class="mw-page-title-main">NGC 4065</span> Galaxy in the constellation Coma Berenices

NGC 4065 is an elliptical galaxy located 300 million light-years away in the constellation Coma Berenices. The galaxy was discovered by astronomer William Herschel on April 27, 1785. It was then rediscovered by John Herschel on April 29, 1832 and was listed as NGC 4057. NGC 4065 is the brightest member of the NGC 4065 Group.

<span class="mw-page-title-main">NGC 4066</span> Galaxy in the constellation Coma Berenices

NGC 4066 is an elliptical galaxy located 340 million light-years away in the constellation Coma Berenices. The galaxy was discovered by astronomer William Herschel on April 27, 1785. NGC 4066 is a member of the NGC 4065 Group.

<span class="mw-page-title-main">NGC 4074</span> Galaxy in the constellation Coma Berenices

NGC 4074 is a peculiar lenticular galaxy located 310 million light-years away in the constellation Coma Berenices. It was discovered by astronomer William Herschel on April 27, 1785 and is a member of the NGC 4065 Group.

References

  1. 1 2 3 4 5 6 7 Becker, Robert H.; White, Richard L.; Helfand, David J. (1 January 1994). "The VLA's FIRST Survey". ASP Conference Series. 61: 165. Bibcode:1994ASPC...61..165B.
  2. ↑ "The VLA FIRST Survey" . Retrieved 1 January 2017.
  3. 1 2 3 4 5 Becker, Robert H.; White, Richard L.; Helfand, David J. (1995). "The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters". Astrophysical Journal. 450: 559. Bibcode:1995ApJ...450..559B. doi: 10.1086/176166 .
  4. 1 2 3 "The FIRST Survey Catalog: 14Dec17 Version" . Retrieved 1 January 2017.
  5. 1 2 "Status of FIRST Survey Observations" . Retrieved 1 January 2017.
  6. ↑ "SkyView surveys".
  7. 1 2 "What's New in FIRST?" . Retrieved 1 January 2017.
  8. ↑ "Description of the FIRST Survey" . Retrieved 1 January 2017.
  9. ↑ White, Richard L.; Becker, Robert H.; Helfand, David J.; Gregg, Michael D. (1 February 1997). "A Catalog of 1.4 GHz Radio Sources from the FIRST Survey". The Astrophysical Journal. 475 (2): 479–493. Bibcode:1997ApJ...475..479W. doi:10.1086/303564.
  10. ↑ "Designation of FIRST Sources" . Retrieved 1 January 2017.
  11. ↑ "The VLA FIRST Survey: Publications". sundog.stsci.edu. Retrieved 30 December 2016.
  12. ↑ Gregg, Michael D.; Becker, Robert H.; White, Richard L.; Helfand, David J.; McMahon, Richard G.; Hook, Isobel M. (1 August 1996). "The First Bright QSO Survey". The Astronomical Journal. 112: 407. arXiv: astro-ph/9604148 . Bibcode:1996AJ....112..407G. doi:10.1086/118024. S2CID   119330027.
  13. ↑ Becker, Robert H.; Gregg, Michael D.; Hook, Isobel M.; McMahon, Richard G.; White, Richard L.; Helfand, David J. (1 April 1997). "The FIRST Radio-loud Broad Absorption Line QSO and Evidence for a Hidden Population of Quasars". The Astrophysical Journal Letters. 479 (2): L93–L96. arXiv: astro-ph/9702012 . Bibcode:1997ApJ...479L..93B. doi:10.1086/310594. S2CID   14603492.
  14. ↑ Brotherton, Michael S.; van Breugel, Wil; Smith, R. J.; Boyle, B. J.; Shanks, T.; Croom, S. M.; Miller, Lance; Becker, Robert H. (1 September 1998). "Discovery of Radio-Loud Broad Absorption Line Quasars Using Ultraviolet Excess and Deep Radio Selection". The Astrophysical Journal Letters. 505 (1): L7–L10. arXiv: astro-ph/9807230 . Bibcode:1998ApJ...505L...7B. doi:10.1086/311599. S2CID   15625175.
  15. ↑ McGreer, Ian D.; Helfand, David J.; White, Richard L. (1 December 2009). "Radio-Selected Quasars in the Sloan Digital Sky Survey". The Astronomical Journal. 138 (6): 1925–1937. arXiv: 0909.4091 . Bibcode:2009AJ....138.1925M. doi:10.1088/0004-6256/138/6/1925. S2CID   8989100.
  16. ↑ Thyagarajan, Nithyanandan; Helfand, David J.; White, Richard L.; Becker, Robert H. (1 November 2011). "Variable and Transient Radio Sources in the FIRST Survey". The Astrophysical Journal. 742 (1): 49. arXiv: 1107.5901 . Bibcode:2011ApJ...742...49T. doi:10.1088/0004-637X/742/1/49. S2CID   118394490.
  17. ↑ Cress, Catherine M.; Helfand, David J.; Becker, Robert H.; Gregg, Michael D.; White, Richard L. (1 December 1996). "The Angular Two-Point Correlation Function for the FIRST Radio Survey". The Astrophysical Journal. 473: 7–14. arXiv: astro-ph/9606176 . Bibcode:1996ApJ...473....7C. doi:10.1086/178122. S2CID   62068.
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