PKS 1155+251
| PKS 1155+251 | |
|---|---|
DESI Legacy Surveys image of PKS 1151+251 | |
| Observation data (J2000.0 epoch) | |
| Constellation | Coma Berenices |
| Right ascension | 11h 58m 25.78s[1] |
| Declination | +24° 50′ 17.96″[1] |
| Redshift | 0.202556[1] |
| Heliocentric radial velocity | 60,725 km/s ± 8[1] |
| Distance | 2.554 Gly |
| Apparent magnitude (V) | 19.40 |
| Characteristics | |
| Type | FSRQ[1] |
| Size | ~286,300 ly (87.78 kpc) (estimated)[1] |
| Other designations | |
| 7C 1155+2206, VIPS 0500, LEDA 1717805, SDSS J115825.79+245018.0, NVSS J115825+245017, OCARS 1155+251, JVAS J1158+2450[1] | |
PKS 1155+251 is a Seyfert type 2 galaxy and also a quasar[2][3] located in the constellation of Coma Berenices. The redshift of the object is (z) 0.202[1] and it was first discovered as an astronomical radio source by astronomers whom they identified it with a galaxy counterpart in 1974.[4] This object has also been classified as a compact symmetrical object (CSO) in literature.[5][6][7]
Description
PKS 1155+251 is described as a radio-loud quasar.[2] The source is mainly compact, with a radio core containing a flat radio spectrum, which is positioned between the lobes of a steep spectrum.[6] Radio imaging made with the Very Long Baseline Array (VLBA) at 15 GHz frequencies found an unresolved component which is surrounded by radio emission towards both directions. An eastern spur feature was discovered from the northern emission component, which goes in the opposite direction from most of the diffused emission. Evidence also suggests the source is shrinking as its hotspot features retreat towards the core position.[5] The angular size is estimated to be 46.0 milliarcseconds in extent with a turnover frequency of 2.0 GHz.[8]
Imaging made with Very Long Baseline Interferometry (VLBI) suggested the radio structure is very complicated with evidence suggesting the northeastern feature is further divided into two narrow jet features.[9] Further observations made with the VLBA at both 24 and 43 GHz frequencies have located the southern complex region. When imaged, it shows the presence of hotspot and blob features that have an orientation from north to west. Further evidence found the component on the central side is unresolved, while the southern component is extremely bright, with an approximate brightness temperature of 109 Kelvin. The measured spectral indexes for both components are around 0.36 ± 0.03 and -0.38 ± 0.03.[2] Two supermassive black holes are suggested to lie inside the center of the galaxy, with the estimated separation of only 3.5 milliarcseconds from each other.[2][10][11]
References
- ^ a b c d e f g h "NED Search results for PKS 1155+251". NASA/IPAC Extragalactic Database. Retrieved 2025-12-19.
- ^ a b c d Yang, Xiaolong; Liu, Xiang; Yang, Jun; Mi, Ligong; Cui, Lang; An, Tao; Hong, Xiaoyu; Ho, Luis C. (2017-07-13). "VLBA 24 and 43 GHz observations of massive binary black hole candidate PKS 1155 + 251". Monthly Notices of the Royal Astronomical Society. 471 (2): 1873–1878. arXiv:1707.03121. doi:10.1093/mnras/stx1743. ISSN 0035-8711.
- ^ "MOJAVE Sample: 1155+251". www.cv.nrao.edu. Retrieved 2025-12-19.
- ^ Hoskins, D. G.; Murdoch, H. S.; Adgie, R. L.; Crowther, J. H.; Gent, H. (February 1974). "Optical identifications for 45 radio sources based on accurate positions". Monthly Notices of the Royal Astronomical Society. 166 (2): 235–248. Bibcode:1974MNRAS.166..235H. doi:10.1093/mnras/166.2.235. ISSN 0035-8711.
- ^ a b Tremblay, S. E.; Taylor, G. B.; Helmboldt, J. F.; Fassnacht, C. D.; Pearson, T. J. (September 2008). "A Shrinking Compact Symmetric Object: J11584+2450?". The Astrophysical Journal. 684 (1): 153–159. arXiv:0806.3955. Bibcode:2008ApJ...684..153T. doi:10.1086/590377. ISSN 0004-637X.
- ^ a b Tremblay, S. E.; Taylor, G. B.; Helmboldt, J. F.; Fassnacht, C. D.; Romani, R. W. (February 2009). "Identifying Compact Symmetric Objects from the VLBA Imaging and Polarization Survey". Astronomische Nachrichten. 330 (2): 206. arXiv:0905.2982. Bibcode:2009AN....330..206T. doi:10.1002/asna.200811157. ISSN 0004-6337.
- ^ Readhead, A. C. S; Ravi, V.; Blandford, R. D.; Sullivan, A. G.; Somalwar, J.; Begelman, M. C.; Birkinshaw, M.; Liodakis, I.; Lister, M. L.; Pearson, T. J.; Taylor, G. B.; Wilkinson, P. N.; Globus, N.; Kiehlmann, S.; Lawrence, C. R. (2024-01-31). "Compact Symmetric Objects. III. Evolution of the High-luminosity Branch and a Possible Connection with Tidal Disruption Events". The Astrophysical Journal. 961 (2): 242. arXiv:2303.11361. Bibcode:2024ApJ...961..242R. doi:10.3847/1538-4357/ad0c55. ISSN 0004-637X.
- ^ Kiehlmann, S.; Lister, M. L.; Readhead, A. C. S; Liodakis, I.; O’Neill, Sandra; Pearson, T. J.; Sheldahl, Evan; Siemiginowska, Aneta; Tassis, K.; Taylor, G. B.; Wilkinson, P. N. (2024-01-31). "Compact Symmetric Objects. I. Toward a Comprehensive Bona Fide Catalog". The Astrophysical Journal. 961 (2): 240. arXiv:2303.11357. Bibcode:2024ApJ...961..240K. doi:10.3847/1538-4357/ad0c56. ISSN 0004-637X.
- ^ Kellermann, K. I.; Vermeulen, R. C.; Zensus, J. A.; Cohen, M. H. (April 1998). "Sub-Milliarcsecond Imaging of Quasars and Active Galactic Nuclei". The Astronomical Journal. 115 (4): 1295–1318. arXiv:astro-ph/9801010. Bibcode:1998AJ....115.1295K. doi:10.1086/300308. ISSN 0004-6256.
- ^ Yang, Xiaolong; Liu, Xiang (February 2016). "May PKS 1155+251 be the habitat of a binary black hole?". Star Clusters and Black Holes in Galaxies Across Cosmic Time. 312: 71–72. doi:10.1017/S1743921315007528. ISSN 1743-9221.
- ^ "Research Progress in Massive Binary Black Holes Candidate VLBI Observation--Xinjiang Astronomical Observatory". english.xao.cas.cn. Retrieved 2025-12-19.