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Register a new userJ2102+6015: a young radio source at z = 4.575
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Jets of high-redshift active galactic nuclei (AGNs) can be used to directly probe the activity of the black holes in the early Universe. Radio sources with jets misaligned with respect to the line of sight are expected to dominate the high-redshift AGN population. In this paper, we present the high-resolution imaging results of a z=4.57 AGN J2102+6015 by analyzing its multi-epoch dual-frequency very long baseline interferometry (VLBI) data. The 8.4-GHz VLBI images reveal two major features along the east-west direction separated by $sim$ 10 milli-arcsec (mas). From the spectral index map, both features show flat/inverted spectra. The separation between the two features remains almost unchanged over an observation period of $sim$ 13 years, placing an upper limit of the separation speed as about 0.04 mas year$^{-1}$. Previous studies have classified the source as a GHz-peaked spectrum quasar. Our results indicate that J2102+6015 is most likely a young, compact symmetric object rather than a blazar-type core-jet source.
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9C J1503+4528 is a very young CSS radio galaxy, with an age of order 10^4 years. This source is an ideal laboratory for the study of the intrinsic host galaxy/IGM properties, radio source interactions, evidence for young stellar populations and the radio source triggering mechanism. Here we present the results of a spectroscopic analysis of this source, considering each of these aspects of radio source physics.
We present a comprehensive analysis of Chandra X-ray observations of 15 young radio quasars at redshifts $4.5 < z < 5.0$. All sources are detected in the $0.5-7.0$ keV energy band. Emission spectra are extracted, and the average photon index for the sample is measured to be $1.5pm0.1$. Unabsorbed rest-frame $2-10$ keV luminosities are found to range between $(0.5-23.2) times 10^{45}$ erg s$^{-1}$. The optical-X-ray power-law spectral index $alpha_{ox}$ is calculated for each source using optical/UV data available in the literature. The $alpha_{ox}$-UV relationship is compared with other quasar surveys, and an anticorrelation is observed that agrees with independent estimates. Rest-frame radio and X-ray luminosities are established for the sample, and a correlation between the luminosities is detected. These multiwavelength results reinforce a lack of spectral evolution for quasars over a broad redshift range. We additionally identify three quasars from our multiwavelength analysis that are statistically significant outliers, with one source being a Compton-thick candidate in the early universe, and discuss each in detail.
Extinct radio pulsars, in which stationary, self-sustaining generation of a relativistic electron-positron plasma becomes impossible when rotation brakes down, can be sources of a subrelativistic flux of positrons and electrons. We assume that the observed excess of positrons in the bulge and the disc of the Galaxy is associated with these old neutron stars. The production of pairs in their magnetospheres occurs due to one-photon absorption of gamma quanta of the Galactic and extragalactic backgrounds. The cascade process of plasma production leads to the flux of positrons escaping from the open magnetosphere $simeq 3 times 10^{34} text{ s}^{-1}$. The total flux of positrons from all old Galactic neutron stars with rotational periods $1.5 < P < 35$ s is $simeq 3 times 10^{43} text{ s}^{-1}$. The energy of positrons is less than $simeq 10$ MeV. The estimated characteristics satisfy the requirements for the positron source responsible for the 511-keV Galactic annihilation line.
We present preliminary results from a multi-wavelength study of a merger candidate, NGC3801, hosting a young FR I radio galaxy, with a Z-shaped structure. Analysing archival data from the VLA, we find two HI emission blobs on either side of the host galaxy, suggesting a 30 kpc sized rotating gas disk aligned with stellar rotation, but rotating significantly faster than the stars. Broad, faint, blue-shifted absorption wing and an HI absorption clump associated with the shocked shell around the eastern lobe are also seen, possibly due to an jet-driven outflow. While 8.0 um dust and PAH emission, from Spitzer and near and far UV emission from GALEX is seen on a large scale in an S-shape, partially coinciding with the HI emission blobs, it reveals a ~2 kpc radius ring-like, dusty, starforming structure in the nuclear region, orthogonal to the radio jet axis. Its similarities with Kinematically Decoupled Core galaxies and other evidences have been argued for a merger origin of this young, bent jet radio galaxy.
9C J1503+4528 is a very young CSS radio galaxy, with an age of order 10^4 years. This source is therefore an ideal laboratory for the study ofthe intrinsic host galaxy/IGM properties, interactions between the radio source and surrounding ISM, links between star formation and AGN activity and the radio source triggering mechanism. Here we present the results of a spectroscopic analysis of this source, considering each of these aspects of radio source physics. We find that shock ionization by the young radio source is important in the central regions of the galaxy on scales similar to that of the radio source itself, whilst evidence for an AGN ionization cone is observed at greater distances. Line and continuum features require the presence of a young stellar population, the best-fit model for which implies an age of 5x10^6 years, significantly older than the radio source. Most interestingly, the relative sizes of radio source and extended emission line region suggest that both AGN and radio source are triggered at approximately the same time. If both the triggering of the radio source activity and the formation of the young stellar population had the same underlying cause, this source provides a sequence for the events surrounding the triggering process. We propose that the AGN activity in 9C J1503+4528 was causedby a relatively minor interaction, and that a super-massive black hole powering the radio jets must have been in place before the AGN was triggered.
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