Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDeep spectroscopy of 9C J1503+4528: a very young CSS radio source at z=0.521
75
0
0.0
(
0
)
Added by
Katherine J. Inskip
Publication date
2006
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
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.
rate research
Read More
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.
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.
The magnetar Swift ,J1818.0-1607 was discovered in March 2020 when Swift detected a 9 ms hard X-ray burst and a long-lived outburst. Prompt X-ray observations revealed a spin period of 1.36 s, soon confirmed by the discovery of radio pulsations. We report here on the analysis of the Swift burst and follow-up X-ray and radio observations. The burst average luminosity was $L_{rm burst} sim2times 10^{39}$ erg/s (at 4.8 kpc). Simultaneous observations with XMM-Newton and NuSTAR three days after the burst provided a source spectrum well fit by an absorbed blackbody ($N_{rm H} = (1.13pm0.03) times 10^{23}$ cm$^{-2}$ and $kT = 1.16pm0.03$ keV) plus a power-law ($Gamma=0.0pm1.3$) in the 1-20 keV band, with a luminosity of $sim$$8times10^{34}$ erg/s, dominated by the blackbody emission. From our timing analysis, we derive a dipolar magnetic field $B sim 7times10^{14}$ G, spin-down luminosity $dot{E}_{rm rot} sim 1.4times10^{36}$ erg/s and characteristic age of 240 yr, the shortest currently known. Archival observations led to an upper limit on the quiescent luminosity $<$$5.5times10^{33}$ erg/s, lower than the value expected from magnetar cooling models at the source characteristic age. A 1 hr radio observation with the Sardinia Radio Telescope taken about 1 week after the X-ray burst detected a number of strong and short radio pulses at 1.5 GHz, in addition to regular pulsed emission; they were emitted at an average rate 0.9 min$^{-1}$ and accounted for $sim$50% of the total pulsed radio fluence. We conclude that Swift ,J1818.0-1607 is a peculiar magnetar belonging to the small, diverse group of young neutron stars with properties straddling those of rotationally and magnetically powered pulsars. Future observations will make a better estimation of the age possible by measuring the spin-down rate in quiescence.
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.
(1270) Datura is the largest member of a very young asteroid cluster that was thought to be broken-up 0.45 Myr ago. The light-curve and the rotation-resolved reflectance spectra (0.6 um - 1.0 um) were observed in order to find fresh surface. Our data show no significant spectral variation along the rotation phase. The depth of the 0.95 um absorption band, which indicates the degree of space weathering, was similar to that of an old S-type asteroid. This suggests that the reflectance spectrum in this wavelength range changes rapidly and saturates the depth of the 0.95 um absorption in less than 0.45 Myr in the main belt environment.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
