| PKS 1155+251 | |
|---|---|
 DESI Legacy Surveys image of PKS 1151+251 | |
| Observation data (J2000.0epoch) | |
| 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 | 2.554Gly |
| 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 aSeyfert type 2 galaxy and also aquasar[2][3] located in the constellation ofComa Berenices. Theredshift of the object is (z) 0.202[1] and it was first discovered as anastronomical radio source byastronomers 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]
PKS 1155+251 is described as a radio-loud quasar.[2] The source is mainly compact, with a radio core containing a flatradio spectrum, which is positioned between the lobes of a steep spectrum.[6] Radio imaging made with theVery Long Baseline Array (VLBA) at 15GHz frequencies found an unresolved component which is surrounded byradio 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 aturnover frequency of 2.0 GHz.[8]
Imaging made withVery Long Baseline Interferometry (VLBI) suggested the radio structure is very complicated with evidence suggesting the northeastern feature is further divided into two narrowjet features.[9] Further observations made with the VLBA at both 24 and 43 GHzfrequencies have located the southern complex region. When imaged, it shows the presence of hotspot and blob features that have anorientation from north to west. Further evidence found the component on the central side is unresolved, while the southern component is extremely bright, with an approximatebrightness temperature of 109Kelvin. The measured spectral indexes for both components are around 0.36 ± 0.03 and -0.38 ± 0.03.[2] Twosupermassive black holes are suggested to lie inside the center of the galaxy, with the estimated separation of only 3.5milliarcseconds from each other.[2][10][11]
