PKS 1127−145

PKS 1127−145 is a radio-loud quasar^[1] located in the constellation of Crater. This is a Gigahertz Peaked Spectrum object^[2][3] with a redshift of (z) 1.187,^[4] first discovered by astronomers in 1966.^[5] Its radio spectrum appears to be flat making it a flat-spectrum radio quasar, or an FRSQ in short.^[6][7]

PKS 1127−145
The quasar, PKS 1127−145.
Observation data (J2000.0 epoch)
Constellation	Crater
Right ascension	11h 30m 07.0526s
Declination	−14° 49′ 27.388″
Redshift	1.180000
Heliocentric radial velocity	353,755 km/s
Distance	8.170 Gly
Apparent magnitude (V)	17.17
Apparent magnitude (B)	16.90
Characteristics
Type	Blazar, LPQ, FSRQ
Notable features	Longest X-ray jet detected in a high redshift quasar
Other designations
INTREF 453, 2E 2471, LEDA 2826758, 4FGL J1129.8−1447, WMAP 157, QSO B1127−1432, PKS 1127−14, OHIO M -146, PMN J1130−1449

Description

PKS 1127−145 displays blazar-like behavior. It is known to undergo a period of gamma ray activity,^[8] especially in December 2020 where its daily gamma ray flux reached a peak of (E > 100 MeV) of (1.6 ± 0.3) x 10⁻⁶ photons cm⁻² s⁻¹.^[9] Two flares were detected by Fermi-LAT in May and October 2022.^[10][11]

The radio structure of PKS 1127−145 is found to be complex. A radio image made by the Very Long Baseline Interferometry (VLBI) shows the object has two components, mainly a bright component and a much weaker component with same brightness temperatures of 1.3 x 10¹¹ Kelvin. No extension is found in northwest direction.^[12] There is a presence of a compact core displaying strong increase of flux density^[13] with the outermost component being separated into several smaller regions enveloped completely by emission.^[9] A stationary feature is also seen located 4 mas from the core via a 22 GHz image taken by VLBI.^[14] Circular polarization has also been found in the quasar as well.^[15]

X-ray jet

Chandra image of the X-ray jet in PKS 1127−145

An X-ray jet has been discovered in PKS 1127−145 by Chandra X-ray Observatory.^[16] With an estimated length of 300 kiloparsecs, this makes the longest one detected so far in any of the high redshift quasars.^[17] Advanced CCD Imaging Spectrometer also revealed a complex structure in the X-ray jet from the core with bright knots of different morphologies. Two of the knots showed changes in their profiles while the other knot is found fainter with presence of X-ray emission scattered over a large area.^[18]

A more in-depth analysis of the X-ray jet in PKS 1127−145 showed the inner jet of PKS 1127−145 located from the core is found to be extremely polarized and a parallel magnetic field towards the jet's axis. Upon reaching 18 arcseconds from the core, the jet suddenly bends slightly causing the re-brightening of radio emission. In additional, there is a 90° rotation of the magnetic field suggesting it might be compressed to the plane that is found perpendicular to the axis.^[9]