| MRC 2011−298 | |
|---|---|
 MRC 2011−298 taken byPan-STARRS | |
| Observation data (J2000.0epoch) | |
| Constellation | Sagittarius |
| Right ascension | 20h 14m 18.86s |
| Declination | −29° 42′ 36.02″ |
| Redshift | 0.136620 |
| Heliocentric radial velocity | 40,958km/s |
| Distance | 2.115Gly (648.5Mpc) |
| Group orcluster | Abell 3670 |
| Apparent magnitude (V) | 0.229 |
| Apparent magnitude (B) | 0.303 |
| Characteristics | |
| Type | E |
| Notable features | Radio galaxy |
| Other designations | |
| PMN J2014−2942,PGC 726073,NVSS J201418−294234, TXS 2011−298,2MASX J20141866−2942364 | |
MRC 2011−298 is anelliptical galaxy with anactive galactic nucleus, located in the constellation ofSagittarius. It is located 2.1 billionlight-years away fromEarth. MRC 2011−298 is thebrightest cluster galaxy in thegalaxy cluster, Abell 3670[1][2] and classified as adumbbell galaxy,[3] an optical system with twogalactic nuclei separated by 7″, corresponding to ≃17 kpc according to the adoptedcosmology, with similarmagnitude and a commonstellar halo.[4] The galaxy is known to have anellipticity ofε = 0.28 and aposition angle of PA = 24° that is measured from north to east.[5]
MRC 2011−298 lies in the rich galaxy cluster which is located atredshiftz = 0.142 . The cluster has an angular scale of 1″ = 2.4 kpc, and with a luminosity distance ofDL = 645 Mpc.
MRC 2011−298 has a peculiar shape which itsradio source was observed at 5.5GHz using theVery Large Array (VLA).[6] Instead of being classified as either a FRI and FRIIradio galaxy,[7] the galaxy belongs to a class ofX-shaped radio galaxies; it exhibits a pair of brightlobes in north to south direction with a pair of weak wings in the east going from east to west direction. These wings are oriented with an angle of about 90°, thus giving the structure its cross-like shape.[8] Like other X-shaped radio galaxies, MRC 2011−298 has primary lobes with jets containing hotspots, but the wings does not hosts jets.
Theflux density of the radio lobes in MRC 2011−298 isSlobes = 294 ± 15 mJy, with east and the west wings have a flux density ofSEw = 32 ± 2 mJy andSWw = 23 ± 1 mJy, respectively. The total length of the lobes is found to bellobes ≃ 60″ ≃ 145 kpc, whereas the wings islEw ≃ 75″ ≃ 180 kpc andlWw ≃ 60″ ≃ 145 kpc wide. Itsratio between the projectedlengths of the wings and lobes of MRC 2011−298 is 2.8.[9]
Thanks to researchers, theradio jets in MRC 2011−298 are found to be characterized by a curvature and an S-shaped structure. But no hotspots are present. Further observations suggests the wings are very faint (S < 5 mJy). The eastern one appears as diffuseemission, while the western wing is better defined. As for the north and south jets, the flux density is confirmed toSSj = 17 ± 1 mJy andSNj = 11.1 ± 0.3 mJy, respectively, with similar lengths oflSj ≃ lNj ≃ 18″ ≃ 40 kpc, suggesting MRC 2011−298 to be an FRI-type XRG measured by 1.4 GHz ofP1.4 = (1.7 ± 0.1) × 1025 W Hz−1.[9] The radio power of the galaxy is consistent with the radio power of typical XRGs, intermediate between that of FRIs and FRIIs.[10]
It is suggested the jets in MRC 2011−298 are aligned with themajor axis of a highellipticity galaxy. This causes stronger environmentgas pressure along the major axis with respect to theminor axis. The backflowplasma originating from the hotspots in MRC 2011−298 is found to redirect towards the minor axis, where the minimumresistance of the gas allows the formation of the wings.[9]
In the buoyant backflow model,[8][11] the wings plasma of MRC 2011−298 are led by thebuoyancy force which evolves atsubsonic speeds. In this variant of this model, strongbackflows forms an over-pressured cocoon, with respect to the surroundinggas. This ejects plasma outflows at supersonic speed along the steepestpressure gradient (i.e. the minor axis), to produce more extended wings. From three-dimensionsnumerical simulations, this suggests a supersonic origin and a subsonic evolution of the wings inside the galaxy.[12]
Further observations found MRC 2011−298 contains gas present inside a stellar shell deflecting the radio jets and causing the wings to be formed. Such evidence found, suggests MRC 2011−298 might have gone agalaxy merger with adisk galaxy triggering its active black hole and a system ofstellar shells. These stellar shells are form of rotatingarc-shaped structures roughly found in ~10% of local elliptical galaxies, that are aligned with their optical major axis.[13] Looking through jet interaction inCentaurus A and the stellar shells, finds a similar phenomenon in X-shaped radio galaxies[14] where they contain traces of neutral and molecularhydrogen with an estimated mass ofMH ≃ 4 × 107 M⊙ and averagedensity ofnH ≃ 4 × 10−2 cm−3.[15]
MRC 2011−298 is known to have a highsupermassive black holemass, which is responsible for reorienting the jets making primary lobes evolve along the new direction, with its wings as fossil emissions from previous jets. This phenomenon is caused after thecoalescence with another supermassive black hole[16] or during the interaction between abinary black hole or unstable regions of itsaccretion disk.[17][10]
From traces of stellar shells and high black hole mass, this indicates MRC 2011−298 is the end product caused by several galaxy mergers, hence sharing common characteristics of dominant cluster galaxies.[18][19]
