اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدChandra Reveals Twin X-ray Jets in the Powerful FR-II Radio Galaxy 3C353
215
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report X-ray imaging of the powerful FR-II radio galaxy 3C353 using the Chandra X-ray Observatory. 3C353s two 4-wide and 2-long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C353, including the nucleus, the jet and the counterjet, the terminal jet regions (hotspots), and one radio lobe. We show that the detection of the X-ray emission associated with the radio knots and counterknots puts several crucial constraints on the X-ray emission mechanisms in powerful large-scale jets of quasars and FR-II sources. In particular, we show that this detection is inconsistent with the inverse-Compton model proposed in the literature, and instead implies a synchrotron origin of the X-ray jet photons. We also find that the width of the X-ray counterjet is possibly narrower than that measured in radio bands, that the radio-to-X-ray flux ratio decreases systematically downstream along the jets, and that there are substantial (kpc-scale) offsets between the positions of the X-ray and radio intensity maxima within each knot, whose magnitudes increase away from the nucleus. We discuss all these findings in the wider context of the physics of extragalactic jets, proposing some particular though not definitive solutions or interpretations for each problem.
قيم البحث
اقرأ أيضاً
We present a Spitzer mid-infrared survey of 42 Fanaroff-Riley class II radio galaxies and quasars from the 3CRR catalog at redshift z<1. All of the quasars and 45+/-12% of the narrow-line radio galaxies have a mid-IR luminosity of nuLnu(15 micron) >
8E43 erg/s, indicating strong thermal emission from hot dust in the active galactic nucleus. Our results demonstrate the power of Spitzer to unveil dust-obscured quasars. The ratio of mid-IR luminous narrow-line radio galaxies to quasars indicates a mean dust covering fraction of 0.56+/-0.15, assuming relatively isotropic emission. We analyze Spitzer spectra of the 14 mid-IR luminous narrow-line radio galaxies thought to host hidden quasar nuclei. Dust temperatures of 210-660 K are estimated from single-temperature blackbody fits to the low and high-frequency ends of the mid-IR bump. Most of the mid-IR luminous radio galaxies have a 9.7 micron silicate absorption trough with optical depth <0.2, attributed to dust in a molecular torus. Forbidden emission lines from high-ionization oxygen, neon, and sulfur indicate a source of far-UV photons in the hidden nucleus. However, we find that the other 55+/-13% of narrow-line FR II radio galaxies are weak at 15 micron, contrary to single-population unification schemes. Most of these galaxies are also weak at 30 micron. Mid-IR weak radio galaxies may constitute a separate population of nonthermal, jet-dominated sources with low accretion power
We present a systematic analysis of the extended X-ray emission discovered around 35 FR II radio galaxies from the revised Third Cambridge catalog (3CR) Chandra Snapshot Survey with redshifts between 0.05 to 0.9. We aimed to (i) test for the presen
ce of extended X-ray emission around FR II radio galaxies, (ii) investigate if the extended emission origin is due to Inverse Compton scattering of seed photons arising from the Cosmic Microwave Background (IC/CMB) or to thermal emission from an intracluster medium (ICM) and (iii) test the impact of this extended emission on hotspot detection. We investigated the nature of the extended X-ray emission by studying its morphology and compared our results with low-frequency radio observations (i.e., $sim$150 MHz), in the TGSS and LOFAR archives, as well as with optical images from Pan-STARRS. In addition, we optimized a search for X-ray counterparts of hotspots in 3CR FR II radio galaxies. We found statistically significant extended emission ($>$3$sigma$ confidence level) along the radio axis for $sim$90%, and in the perpendicular direction for $sim$60% of our sample. We confirmed the detection of 7 hotspots in the 0.5 - 3 keV. In the cases where the emission in the direction perpendicular to the radio axis is comparable to that along the radio axis, we suggest that the underlying radiative process is thermal emission from ICM. Otherwise, the dominant radiative process is likely non-thermal IC/CMB emission from lobes. We found that non-thermal IC/CMB is the dominant process in $sim$70% of the sources in our sample, while thermal emission from the ICM dominates in $sim$15% of them.
We report the results from an ASCA X-ray observation of the powerful Broad Line Radio Galaxy, 3C109. The ASCA spectra confirm our earlier ROSAT detection of intrinsic X-ray absorption associated with the source. The absorbing material obscures a cent
ral engine of quasar-like luminosity. The luminosity is variable, having dropped by a factor of two since the ROSAT observations 4 years before. The ASCA data also provide evidence for a broad iron emission line from the source, with an intrinsic FWHM of ~ 120,000 km/s. Interpreting the line as fluorescent emission from the inner parts of an accretion disk, we can constrain the inclination of the disk to be $> 35$ degree, and the inner radius of the disk to be $< 70$ Schwarzschild radii. Our results support unified schemes for active galaxies, and demonstrate a remarkable similarity between the X-ray properties of this powerful radio source, and those of lower luminosity, Seyfert 1 galaxies.
The energetic composition of radio lobes in the FR II galaxies $-$ estimated by comparing their radio luminosities with the powers required to inflate cavities in the external medium $-$ seems to exclude the possibility of their energetic domination
by protons. Furthermore, if the jets were dominated by the kinetic energy of cold protons, it would be difficult to efficiently accelerate leptons in the jets terminal shocks. Assuming that the relative energy contents of leptons, protons and magnetic fields are preserved across the shocks, the above implies that the large-scale jets should also be energetically dominated by leptons: $P_{rm e,j} gtrsim P_{rm p,j}$. On the other hand, previous studies of small-scale jets in blazars and radio cores suggest a pair content (number of electrons and positrons per proton) of the order of $n_{rm e}/n_{rm p} sim 20$. Assuming further that the particle composition of jets does not evolve beyond the blazar scales, we show that this implies an average random Lorentz factor of leptons in large-scale jets of $bargamma_{rm e,j} gtrsim 70(1+chi_{rm p})(20n_{rm p}/n_{rm e})$, and that the protons should be mildly relativistic with $chi_{rm p} equiv (epsilon_{rm p} + p_{rm p})/rho_{rm p} c^2 lesssim 2$, $p_{rm p}$ the pressure of protons, $epsilon_{rm p}$ the internal energy density of protons, and $rho_{rm p} c^2$ the rest-mass energy density of protons. We derive the necessary conditions for loading the inner jets by electron-positron pairs and proton-electron plasma, and provide arguments that heating of leptons in jets is dominated by magnetic reconnection.
We report results from our deep Chandra X-ray observations of a nearby radio galaxy, 4C+29.30 (z=0.0647). The Chandra image resolves structures on sub-arcsec to arcsec scales, revealing complex X-ray morphology and detecting the main radio features:
the nucleus, a jet, hotspots, and lobes. The nucleus is absorbed (N(H)=3.95 (+0.27/-0.33)x10^23 atoms/cm^2) with an unabsorbed luminosity of L(2-10 keV) ~ (5.08 +/-0.52) 10^43 erg/s characteristic of Type 2 AGN. Regions of soft (<2 keV) X-ray emission that trace the hot interstellar medium (ISM) are correlated with radio structures along the main radio axis indicating a strong relation between the two. The X-ray emission beyond the radio source correlates with the morphology of optical line-emitting regions. We measured the ISM temperature in several regions across the galaxy to be kT ~ 0.5 with slightly higher temperatures (of a few keV) in the center and in the vicinity of the radio hotspots. Assuming these regions were heated by weak shocks driven by the expanding radio source, we estimated the corresponding Mach number of 1.6 in the southern regions. The thermal pressure of the X-ray emitting gas in the outermost regions suggest the hot ISM is slightly under-pressured with respect to the cold optical-line emitting gas and radio-emitting plasma, which both seem to be in a rough pressure equilibrium. We conclude that 4C+29.30 displays a complex view of interactions between the jet-driven radio outflow and host galaxy environment, signaling feedback processes closely associated with the central active nucleus.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
