{{Short description|Quasar located in the constellation Draco}} {{Infobox galaxy|name=[[Third Cambridge Catalogue of Radio Sources|3C]] 343|epoch=[[J2000.0]]|ra={{RA|16|34|33.80}}<ref name="ned" />|constellation name=[[Draco (constellation)|Draco]]|dec={{DEC|+62|45|35.89}}<ref name="ned" />|z=0.988000<ref name="ned" />|h_radial_v=296,195 [[kilometer per second|km/s]]<ref name="ned" />|dist_ly=7.880 [[light year|Gly]]|appmag_b=21.06|type=HEG, CSS<ref name="ned" />|names=[[Fourth Cambridge Survey|4C]] +62.26, [[Lyon-Meudon Extragalactic Database|LEDA]] 2817689, [[NRAO VLA Sky Survey|NVSS]] J163433+624535, [[Sixth Cambridge Survey of Radio Sources|6C]] B163400.8+625137, DA 416, NRAO 0509, CoNFIG 255<ref name="ned" />|image=File:Image of 3C 343.png|caption=[[Sloan Digital Sky Survey|SDSS]] image of 3C 343.}}

'''3C 343''' is a [[quasar]]<ref>{{Cite journal |last1=Spencer |first1=R.E. |last2=McDowell |first2=J.C. |last3=Charlesworth |first3=M. |last4=Fanti |first4=C. |last5=Parma |first5=P. |last6=Peacock |first6=J.A. |date=October 1989 |title=MERLIN and VLA observations of compact steep-spectrum radio sources. |url=https://articles.adsabs.harvard.edu/pdf/1989MNRAS.240..657S |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=240 |issue=3 |pages=657–687 |doi= 10.1093/mnras/240.3.657 |doi-access=free |issn=0035-8711 |archive-url=https://web.archive.org/web/20240626141627/https://ui.adsabs.harvard.edu/abs/1989MNRAS.240..657S/abstract |archive-date=2024-06-26}}</ref> located in the constellation of [[Draco (constellation)|Draco]]. The [[redshift]] of the object is (z) 0.988<ref name="ned">{{Cite web |title=NED Search results for 3C 343 |url=https://ned.ipac.caltech.edu/byname?objname=3C+343&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 |access-date=2025-09-28 |website=NASA/IPAC Extragalactic Database}}</ref> and it was first recorded in the [[Third Cambridge Catalogue of Radio Sources]] survey in 1962.<ref>{{Cite journal |last=S. |first=Bennett, A. |date=1962 |title=The revised 3C catalogue of radio sources. |url=https://ui.adsabs.harvard.edu/abs/1962MmRAS..68..163B/abstract |journal=Memoirs of the Royal Astronomical Society |language=en |volume=68 |page=163 |bibcode=1962MmRAS..68..163B |archive-url=https://web.archive.org/web/20240413093523/https://ui.adsabs.harvard.edu/abs/1962MmRAS..68..163B/abstract |archive-date=2024-04-13}}</ref> It is a [[Seyfert galaxy|Seyfert type 2 galaxy]]<ref>{{Cite journal |last1=Aldcroft |first1=Thomas L. |last2=Bechtold |first2=Jill |last3=Elvis |first3=Martin |date=July 1994 |title=MG II absorption in a sample of 56 steep-spectrum quasars |url=https://ui.adsabs.harvard.edu/abs/1994ApJS...93....1A/abstract |journal=The Astrophysical Journal Supplement Series |language=en |volume=93 |pages=1 |doi=10.1086/192044 |bibcode=1994ApJS...93....1A |issn=0067-0049 |archive-url=https://web.archive.org/web/20240706052001/https://ui.adsabs.harvard.edu/abs/1994ApJS...93....1A/abstract |archive-date=2024-07-06}}</ref> and such contains a compact steep [[spectrum]] source that is classified as double.<ref name=":0">{{Cite journal |last1=Pearson |first1=T. J. |last2=Readhead |first2=A. C. S. |date=May 1988 |title=The milliarcsecond structure of a complete sample of radio sources. II - First-epoch maps at 5 GHz |url=https://ui.adsabs.harvard.edu/abs/1988ApJ...328..114P/abstract |journal=The Astrophysical Journal |language=en |volume=328 |pages=114 |doi=10.1086/166274 |bibcode=1988ApJ...328..114P |issn=0004-637X |archive-url=https://web.archive.org/web/20221107063549/https://ui.adsabs.harvard.edu/abs/1988ApJ...328..114P/abstract |archive-date=2022-11-07}}</ref><ref name=":1">{{Cite journal |last1=N. |first1=Ren-Dong |last2=T. |first2=Schilizzi, R. |last3=C. |first3=Fanti |last4=R. |first4=Fanti |last5=van Breugel, W. J. M. |last6=W. |first6=Muxlow, T. |date=1988 |title=The radio structure of the compact steep spectrum sources 3C 119, 3C 287 and 3C 343. |url=https://ui.adsabs.harvard.edu/scan/manifest/1988IAUS..129..119R |journal=The Impact of VLBI on Astrophysics and Geophysics |language=en |volume=129 |issn=1743-9221 |archive-url=https://web.archive.org/web/20241110211100/https://ui.adsabs.harvard.edu/abs/1988IAUS..129..119R/abstract |archive-date=2024-11-10}}</ref><ref>{{Cite journal |last=Moffet |first=AT |date=1965 |title=3C 343, a Double Radio Source with Very Wide Component Separation |url=https://ui.adsabs.harvard.edu/scan/manifest/1965ApJ...141.1580M |journal=American Astronomical Society}}</ref>

== Description == 3C 343 is classified as a young radio-loud [[Active galactic nucleus|active galaxy]] with a radio power of 27.7 [[Hertz|GHz]].<ref name=":2">{{Cite journal |last1=Kawakatu |first1=Nozomu |last2=Nagao |first2=Tohru |last3=Woo |first3=Jong-Hak |date=2009-03-10 |title=Exploring the Disk-Jet Connection From the Properties of Narrow-Line Regions in Powerful Young Radio-Loud Active Galactic Nuceli |journal=The Astrophysical Journal |language=en |volume=693 |issue=2 |pages=1686–1695 |doi=10.1088/0004-637X/693/2/1686 |arxiv=0812.1329 |bibcode=2009ApJ...693.1686K |issn=0004-637X }}</ref> It contains a compact source described as a single component that is around 200 [[Millisecond|milliseconds]] in [[diameter]].<ref name=":0" /> [[Polarimetry|Polarimetric]] observations made with the [[Very Long Baseline Array]] (VLBA) reveal two components that are surrounded by weak [[Radio wave|radio emission]]. Both of these components are shown to have a steep [[radio spectrum]] between the frequencies of 4.8 and 8.4 GHz.<ref name=":3">{{Cite journal |last1=Mantovani |first1=F. |last2=Rossetti |first2=A. |last3=Junor |first3=W. |last4=Saikia |first4=D. J. |last5=Salter |first5=C. J. |date=2010-07-01 |title=Radio polarimetry of 3C 119, 3C 318, and 3C 343 at milliarcsecond resolution |url=https://www.aanda.org/articles/aa/abs/2010/10/aa14400-10/aa14400-10.html |journal=Astronomy & Astrophysics |language=en |volume=518 |pages=A33 |doi=10.1051/0004-6361/201014400 |arxiv=1005.2950 |bibcode=2010A&A...518A..33M |issn=0004-6361}}</ref>

Observations with European [[Very-long-baseline interferometry|Very Long Baseline Interferometry]] (VLBI) at 18 [[Centimetre|centimeters]] showed the source has several emission ridges distributed across multiple [[Position angle|position angles]], while newer VLBI observations described the source as elongated from north to west.<ref>{{Cite journal |last1=C. |first1=Fanti |last2=R. |first2=Fanti |last3=P. |first3=Parma |last4=T. |first4=Schilizzi, R. |last5=van Breugel, W. J. M. |date=February 1985 |title=Compact steep spectrum 3 CR radio sources. VLBI observations at 18 cm. |url=https://articles.adsabs.harvard.edu/pdf/1985A%26A...143..292F |journal=Astronomy and Astrophysics |language=en |volume=143 |page=292 |bibcode=1985A&A...143..292F |issn=0004-6361 |archive-url=https://web.archive.org/web/20240327105002/https://ui.adsabs.harvard.edu/abs/1985A&A...143..292F/abstract |archive-date=2024-03-27}}</ref><ref>{{Cite journal |last1=Dallacasa |first1=D |last2=Orienti |first2=M |last3=Fanti |first3=C |last4=Fanti |first4=R |date=2021-04-13 |title=VLBI images at 327 MHz of compact steep spectrum and GHz-peaked spectrum sources from the 3C and PW samples |journal=Monthly Notices of the Royal Astronomical Society |volume=504 |issue=2 |pages=2312–2324 |doi=10.1093/mnras/stab1014 |doi-access=free |issn=0035-8711|arxiv=2104.12804 }}</ref> A complex structure is found inside a core component by VLBI.<ref>{{Cite journal |last1=Pearson |first1=T. J. |last2=Readhead |first2=A. C. S. |last3=Perley |first3=R. A. |date=May 1985 |title=Compact radio sources in the 3C catalog |url=https://articles.adsabs.harvard.edu/pdf/1985AJ.....90..738P |journal=The Astronomical Journal |language=en |volume=90 |pages=738 |doi=10.1086/113782 |bibcode=1985AJ.....90..738P |issn=0004-6256 |archive-url=https://web.archive.org/web/20240609160637/https://ui.adsabs.harvard.edu/abs/1985AJ.....90..738P/abstract |archive-date=2024-06-09}}</ref> There is a [[Astrophysical jet|radio jet]] present in 3C 343, having a knotty appearance and deflated through collisions with [[interstellar medium]].<ref name=":1" /> This jet is estimated to have a linear size of 1.45 [[Parsec|kiloparsecs]].<ref name=":2" />

A new component was discovered in 3C 343 via an 8.4 GHz radio image. This component is found in an eastern direction from the first component and has an estimated [[flux]] [[density]] of 7.7 [[Jansky|mJy]]. It is noted to have a radio spectrum that is inverted, making it possible this is the radio core. Further evidence also revealed the component is situated on the jet's curved [[trajectory]] path. Polarization is found in 3C 343, with the [[percentage]] of it being around 0.96%.<ref name=":3" /> It is noted to be variable, increasing rapidly though [[wavelength]] observations.<ref>{{Cite journal |last1=van Breugel |first1=W. |last2=Miley |first2=G. |last3=Heckman |first3=T. |date=January 1984 |title=Studies of kiloparsec-scale, steep-spectrum radio cores. I VLA maps |url=https://articles.adsabs.harvard.edu/pdf/1984AJ.....89....5V |journal=The Astronomical Journal |language=en |volume=89 |pages=5 |doi=10.1086/113480 |bibcode=1984AJ.....89....5V |issn=0004-6256 |archive-url=https://web.archive.org/web/20240609175842/https://ui.adsabs.harvard.edu/abs/1984AJ.....89....5V/abstract |archive-date=2024-06-09}}</ref> A [[supermassive black hole]] mass of 7.5 M<sub>☉</sub> has been found for the quasar.<ref>{{Citation |last=Wu |first=Qingwen |title=The black hole mass, Eddington ratio and ''M'' <sub>BH</sub>-σ<sub>&#91;O III&#93;</sub>relation in young radio galaxies |journal=Monthly Notices of the Royal Astronomical Society |date=2009-05-22 |volume=398 |issue=4 |pages=1905–1914 |doi=10.1111/j.1365-2966.2009.15127.x |doi-access=free |arxiv=0905.3663 |bibcode=2009MNRAS.398.1905W }}</ref>

== References == <references />

== External links == {{WikiSky}} *[http://simbad.u-strasbg.fr/simbad/sim-id?bibyear1=1850&bibyear2=%24currentYear&submit=Display&Ident=%40375002&Name=ICRF+J163433.8%2B624535&bibdisplay=refsum&bibyear1=1850&bibyear2=%24currentYear#lab_bib 3C 343 on SIMBAD]

{{Draco (constellation)}} [[Category:3C objects|343]] [[Category:Quasars]] [[Category:Draco (constellation)]] [[Category:LEDA objects|2817689]] [[Category:Active galaxies]] [[Category:4C objects|+62.26]] [[Category:Astronomical objects discovered in 1962]]