{{Short description|Quasar in the constellation Boötes}} {{Infobox galaxy|name=OQ 172|epoch=[[J2000.0]]|constellation name=[[Boötes]]|ra={{RA|14|45|16.465}}|dec={{DEC|+09|58|36.073}}|z=3.540681|dist_ly=11.543 [[light years|Gly]]|appmag_v=17.78|appmag_b=18.58|type=GPS, FSRQ|names=[[Lyon-Meudon Extragalactic Database|LEDA]] 2828124, [[Parkes Catalogue of Radio Sources|PKS]] 1442+101, [[NRAO VLA Sky Survey|NVSS]] J144516+095836, [[Quasar|QSO]] B1442+101, TXS 1442+101, CoNFIG 200, IERS B1442+101|image=File:Image of OQ 172.jpg|caption=The quasar OQ 172.}}
'''OQ 172''' ('''OHIO Q 172''') is a [[quasar]]<ref>{{Cite journal |last1=Fomenko |first1=A. F. |last2=Levshakov |first2=S. A. |last3=Varshalovich |first3=D. A. |last4=Nebelitskii |first4=V. B. |date=1984-02-01 |title=Spectra of the quasar OQ 172 |url=https://ui.adsabs.harvard.edu/abs/1984PAZh...10...83F/abstract |journal=Pis'ma v Astronomicheskii Zhurnal |volume=10 |pages=83–89 |bibcode=1984PAZh...10...83F |issn=0320-0108}}</ref> located in the [[constellation]] of [[Boötes]]. It has a [[redshift]] of (z) 3.544,<ref>{{Cite journal |last1=Morton |first1=D. C. |last2=Peterson |first2=B. A. |last3=Chen |first3=J.-S. |last4=Wright |first4=A. E. |last5=Jauncey |first5=D. L. |date=1989-12-01 |title=The spectrum of the QSO 1442 + 101 (OQ172) at intermediate dispersion |journal=Monthly Notices of the Royal Astronomical Society |volume=241 |issue=3 |pages=595–612 |doi=10.1093/mnras/241.3.595 |doi-access=free |issn=0035-8711}}</ref> making it one of the [[List of quasars|most distant quasars]] at the time of its discovery by [[astronomer]]s in 1973.<ref>{{Cite journal |last1=Gurvits |first1=L.I. |last2=Schilizzi |first2=R.T. |last3=Barthel |first3=P.D. |last4=Kardashev |first4=N.S. |last5=Kellermann |first5=K.L. |last6=Lobanov |first6=A.P. |title=Milliarcsecond structures of extremely distant quasars: 0336-017, 0636+680, 1442+101, and 2048+312 |url=https://articles.adsabs.harvard.edu/full/1994A%26A...291..737G/0000738.000.html |journal=Astronomy & Astrophysics |date=1994 |volume=291 |issue=3 |pages=737–742 |bibcode=1994A&A...291..737G |issn=0004-6361}}</ref> This object was the record holder for almost a decade, before being surpassed by [[PKS 2000-330]] in 1982 located at the redshift of (z) 3.78.<ref>{{Cite journal |last=Shaver |first=Peter |date=December 1987 |title=Ever more distant quasars? |url=https://www.nature.com/articles/330426a0.pdf |journal=Nature |volume=330 |issue=6147 |pages=426 |doi=10.1038/330426a0 |bibcode=1987Natur.330..426S |issn=0028-0836}}</ref>
== Description == The source of OQ 172 has a [[radio spectrum]] characterized by its [[Spectral density|spectral]] peak in the [[Hertz|gigahertz]] domain, making it a [[Hertz|gigahertz]]-peaked spectrum quasar (GPS)<ref>{{Cite journal |last1=Liu |first1=Y. |last2=Jiang |first2=D. R. |last3=Gu |first3=M. |last4=Gurvits |first4=L. I. |date=2016-02-01 |title=The compact radio structure of the high-redshift quasar OQ172 |url=https://ui.adsabs.harvard.edu/abs/2016AN....337..101L/abstract |journal=Astronomische Nachrichten |volume=337 |issue=1–2 |pages=101 |doi=10.1002/asna.201512273 |bibcode=2016AN....337..101L |issn=0004-6337}}</ref><ref>{{Cite journal |last1=Barthel |first1=Peter D. |last2=Vestergaard |first2=Marianne |last3=Lonsdale |first3=Colin J. |date=2000-02-01 |title=Radio imaging of core-dominated high redshift quasars |url=https://articles.adsabs.harvard.edu/pdf/2000A%26A...354....7B |journal=Astronomy and Astrophysics |volume=354 |pages=7–16 |arxiv=astro-ph/9911474 |bibcode=2000A&A...354....7B |issn=0004-6361}}</ref> or a compact steep spectrum source (CSS).<ref>{{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=2013-06-18 |title=Radio polarimetry of compact steep spectrum sources at sub-arcsecond resolution |url=https://www.aanda.org/articles/aa/pdf/2013/07/aa20769-12.pdf |journal=Astronomy & Astrophysics |volume=555 |pages=A4 |doi=10.1051/0004-6361/201220769 |arxiv=1305.1644 |bibcode=2013A&A...555A...4M |issn=0004-6361}}</ref>
OQ 172 contains a core-jet structure with the radio core itself located in the northern region of the radio emission.<ref name=":0">{{Cite journal |last1=Mantovani |first1=F. |last2=Junor |first2=W. |last3=Bondi |first3=M. |last4=Cotton |first4=W. |last5=Fanti |first5=R. |last6=Padrielli |first6=L. |date=1998 |title=Large bent jets in the inner region of CSSs |url=https://articles.adsabs.harvard.edu/pdf/1998A%26A...332...10M |journal=Astronomy & Astrophysics |volume=332 |pages=10–18 |arxiv=astro-ph/9712084 |bibcode=1998A&A...332...10M }}</ref> This core is found to show a flat [[spectrum]] up to > 30 GHz in the rest frame with a steep spectrum above 30 GHz which continues steepening until 1000 GHz, thus confirming there is no buried flat spectrum core within the emission source.<ref>{{Cite journal |last1=Punsly |first1=Brian |last2=Marziani |first2=Paola |last3=Kharb |first3=Preeti |last4=O’Dea |first4=Christopher P. |last5=Vestergaard |first5=Marianne |date=2015-10-09 |title=The Extreme Ultraviolet Deficit: Jet Connection In the Quasar 1442+101 |url=http://dx.doi.org/10.1088/0004-637x/812/1/79 |journal=The Astrophysical Journal |volume=812 |issue=1 |pages=79 |doi=10.1088/0004-637x/812/1/79 |arxiv=1509.02619 |bibcode=2015ApJ...812...79P |issn=1538-4357}}</ref>
The [[Astrophysical jet|jet]] of OQ 172 is found to turn almost at an 180° [[angle]] with jet emission in the west-southwest direction extending right from the core, eventually bending almost southwards. When reaching 20 mas south of the core, the jet immediately bends once again, this time at 90° and extends towards the east.<ref name=":1">{{Cite journal |last1=Udomprasert |first1=P. S. |last2=Taylor |first2=G. B. |last3=Pearson |first3=T. J. |last4=Roberts |first4=D. H. |date=1997-07-01 |title=Evidence for Ordered Magnetic Fields in the Quasar Environment |url=https://iopscience.iop.org/article/10.1086/310725/fulltext/ |journal=The Astrophysical Journal |volume=483 |issue=1 |pages=L9–L12 |doi=10.1086/310725 |issn=0004-637X|arxiv=astro-ph/9704112 |bibcode=1997ApJ...483L...9U }}</ref> A further study also shows the jet has three components, one of which is the fastest at a [[proper motion]] of 0.13 ± 0.01 mas yr<sup>−1</sup>. With a mean T<sub>B</sub> of 15.5 ± 6.4 × 10<sup>10</sup> K, this suggests OQ 172 has a highly [[Relativistic beaming|beamed jet]].<ref>{{Cite journal |last1=Zhang |first1=Yingkang |last2=An |first2=Tao |last3=Frey |first3=Sándor |last4=Gabányi |first4=Krisztina Éva |last5=Sotnikova |first5=Yulia |date=September 2022 |title=Radio Jet Proper-motion Analysis of Nine Distant Quasars above Redshift 3.5 |journal=The Astrophysical Journal |language=en |volume=937 |issue=1 |pages=19 |doi=10.3847/1538-4357/ac87f8 |doi-access=free |issn=0004-637X|arxiv=2209.10760 |bibcode=2022ApJ...937...19Z }}</ref>
[[Very-long-baseline interferometry|Very long baseline interferometry]] radio observations revealed OQ 172 has [[magnetic field]]s on parsec scales which rotate the polarization plane of the radio emission originating from both its core and inner jet.<ref name=":1" /> Based on the derived rest-frame rotational measurement of RM 40,000 rad m<sup>−2</sup>, it is found OQ 172 has the highest value amongst other known RM sources.<ref name=":2">{{Cite journal |last1=Liu |first1=Yi |last2=Jiang |first2=D. R. |last3=Gu |first3=Minfeng |last4=Gurvits |first4=L. I. |date=2017-03-15 |title=Multifrequency VLBA polarimetry of the high-redshift GPS quasar OQ172 |journal=Monthly Notices of the Royal Astronomical Society |volume=468 |issue=3 |pages=2699–2712 |doi=10.1093/mnras/stx617 |doi-access=free |issn=0035-8711|arxiv=1703.04066 }}</ref> When at 10 mas from the core, the jet's absolute value of RM decreases to <100 rad m<sup>−2</sup>.<ref name=":1" /> Additionally, linear [[Polarization (waves)|polarized]] emission has been detected in both components in all five [[Frequency|frequencies]]. The core has low fractional polarization, while the jet components have a higher polarization. A rotational measurement was obtained at 4.8 and 8.3 GHz respectively, showing a high value of 2000 rad m<sup>−2</sup> in the innermost region of OQ 172. Towards the outer jet regions, this value drops to 700 rad m<sup>−2</sup>, quickly decreasing to lower values.<ref name=":2" /><ref name=":0" />
== References == <references />
== External links == *[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=QSO%20B1445%2B101 OQ 172 on SIMBAD] *[http://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=63686&objname=2&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1 OQ 172 on NASA/IPAC Database]
{{Boötes}}
[[Category:Quasars]] [[Category:Boötes]] [[Category:LEDA objects|2828124]] [[Category:Active galaxies]] [[Category:Astronomical objects discovered in 1973]]