| MRC 0406-244 | |
|---|---|
 MRC 0406-244, as seen byESO | |
| Observation data (J2000.0epoch) | |
| Constellation | Eridanus |
| Right ascension | 04h 08m 51.47s |
| Declination | -24d 18m 16.47s |
| Redshift | 2.440000 |
| Heliocentric radial velocity | 731,494km/s |
| Distance | 10.647Gly (light travel time distance) |
| Apparent magnitude (V) | 0.144 |
| Apparent magnitude (B) | 0.190 |
| Surface brightness | 22.4 |
| Notable features | Radio galaxy,seyfert galaxy,galaxy merger |
| Other designations | |
| TN J0408-2418, PMN J0408-2418,PGC 2823818,NVSS J040851-241815, TXS 0406-244, LQAC 062-024 001, GLEAM J040851-241817 | |
MRC 0406-244 also known asTN J0408-2418, is aradio galaxy producing anastrophysical jet,[1] located in the constellation ofEridanus. At itsredshift of 2.44, it is roughly ten billion light years from Earth.[2]
MRC 0406-244 is one of the most powerful radio galaxies known date-to-date; it was studied extensively by the MRC/1 Jy radio source survey.[3] MRC 0406-244 is also classified aSeyfert type 2 galaxy,[4][5] with a complexmorphology featuring several components, including a point source with an extendednebular and continuumemission.[6] Moreover, it contains an ultra-deep spectrumradio source (USS).[7]
Host galaxy
The host galaxy of MRC 0406-244 is a dusty obscured massiveearly-type galaxy with astar formation of (M⋆ ~ 1011 M⊙). The galaxy also has astellar disc, within the range of 3.5 to 8.2 kpc which is similar to coeval star-forming galaxies, which is found to be smooth.[6]
Galaxy merger
From recentHubble Space Telescope (HST) images, researchers have found several bright clumps with figure-of-eight shapes elongated along the radiojet axis of MRC 0406–244. Further images reveal there is a spatially resolved continuum. It is associated with its southeastern component that is aligned with the radio axis, with a complex morphology, including a double nucleus andtidal tail features.[8] This suggests of a tidal origin, meaning a recentgalaxy merger has taken place.[9] It is believed that galaxy merger plays a dominant role in which itssupermassive black hole is fueled.[10] Signs show the black hole inside the center of MRC 0406–244, is growing at an exponential rate of hundreds to thousands ofsolar masses per year, so as the luminosity, turning it into aquasar.[11][12]
According from HST and ground-basedmultiwavelength observations of MRC 0406–244,[13] researchers found there are two distinct components, aligned with its radio source axis. One of them has the red optical-to-IR and blueultraviolet colors, making it a characteristic of radio galaxies, while the other is red in all colors. From theLyα image, a nebula in MRC 0406-244 is found to be 3'' × 5'' extent, confined to the range ofazimuth angles with respect to the nucleus of 60° to either side. Another component is also found extending northwest with similar morphology seen in the HST images.[14]
Researchers also found the long axis of the Lyman-alpha emission that is 130° east of north in MRC 0406–244, aligns with the radio source. They found out, the total Lyflux is 1.2× 10−14ergs s−1 cm−2, equivalent to aluminosity of 1× 1045 ergs s−1.1 40% of this flux is within the 25× 35 area that is measured in thespectrum. The peaksurface brightness of the Ly emission is found to be 9.0× 10−16 ergs s−1 cm−2 arcsec−2, and emission is detected down to a level of 1.5× 10−16 ergs s−1 cm−2 arcsec−2.[14]
A triple radio source found in MRC 0406–244, is amongst the most power radio sources known according to researchers. They noted that the radio source reaches up to luminosity of 1.2× 1036 ergs s−1 Hz−1 at 1 GHz andradiating at 6.3× 1045 ergs s−1 between 100MHz and 100GHz. This extends over 84 kpc between the hot spots of MRC 0406–244, which found to be steep and strongly curved. Thespectral index of the radio source changes from 1.21 at 1 GHz to 1.49 at 16 GHz in the rest frame toflux densities at severalfrequencies between 408 MHz and 8.44 GHz. This radio core contains a spectral index of 0.80 ± 0.18 (between 4.7 and 8.4 GHz, observed) that contributes the total emission at 15 GHz at 2%.[14]
The tworadio lobes in MRC 0406-244 are notable for theirdegree of asymmetry. Given the asymmetries inarm length and the spectral indices in powerful sources, they are both related both intrinsic asymmetries andlight travel-time differences. From the correlation betweenemission-line and radio asymmetries in other 3CR radio galaxies,[15] this suggests dominance ofenvironmental effects, whichcosmic dust plays a main role in correlation ofoptical and radio asymmetries.[14]
Further observations from researchers found, that nebular and continuum ultraviolet light extends up to 25 kpc from the nucleus of the galaxy. This is six times more than the length of theminor axis in the direction of the radio jets. Both extended components are shown to contribute to the alignment effect given their distribution is biconical along the jet axis.[16][17] The dust at similarly large radii is known to exist, given the diffuse blue continuum is dust-scattered fromactive galactic nucleus light or from dust-reddened youngstars. The dust must had probably originated in the galaxy, hence the outflow of bothmetal-rich gas and dust is important for enriching theintracluster medium.
The nebular gas can be driven out from MRC 0406–244 in two ways. One, either through expandingstarburst bubbles.[18] Two, by overpressurizedcocoons of material that is surrounding the expanding radio jets.[19] Thedust grains are likely destroyed wheninteracting with powerful radio jets, so they instead transported by radiationpressure[20] orsupernovae inducedwinds.[21]
Dust in theintergalactic medium has theorized for a long time, but detected only recently. From the study published by Ménard et al. (2010), it is suggested half of thecosmic dust lies withingalaxies, whilst the other half is expelled to theintergalactic medium.[22] The extended light in MRC 0406−244 allows researchers, a rare opportunity to observe the dust in the midst of leaving the galaxy. As the host galaxy of MRC 0406−244 does not have different characteristics compared to other massive star-forming galaxies, it is possible that many highly star-forming galaxies lying at a similarredshift also expels out similar amounts of dust inbipolar outflows. The dust remains invisible unless it gets illuminated through sufficiently bright active galactic nuclei or throughfeedback driven star formations. If such dusty outflows in MRC 0406-244 is common, then researchers are expected to see ultraviolet-brightemission along the minor axis of stacked images of starbursting active galactic nuclei.[6]
