اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدChandra & HST Imaging of the Quasars PKS B0106+013 & 3C345: Inverse Compton X-rays and Magnetized Jets
69
0
0.0
(
0
)
تأليف
Preeti Kharb
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present results from deep (70 ks) Chandra ACIS observations and Hubble Space Telescope ACS F475W observations of two highly optically polarized quasars belonging to the MOJAVE blazar sample, viz., PKS B0106+013 and 1641+399 (3C345). These observations reveal X-ray and optical emission from the jets in both sources. X-ray emission is detected from the entire length of the 0106+013 radio jet, which shows clear bends or wiggles - the X-ray emission is brightest at the first prominent kpc jet bend. A picture of a helical kpc jet with the first kpc-scale bend representing a jet segment moving close(r) to our line of sight, and getting Doppler boosted at both radio and X-ray frequencies, is consistent with these observations. The X-ray emission from the jet end however peaks at about 0.4 (~3.4 kpc) upstream of the radio hot spot. Optical emission is detected both at the X-ray jet termination peak and at the radio hot spot. The X-ray jet termination peak is found upstream of the radio hot spot by around 0.2 (~1.3 kpc) in the short projected jet of 3C345. HST optical emission is seen in an arc-like structure coincident with the bright radio hot spot, which we propose is a sharp (apparent) jet bend instead of a terminal point, that crosses our line of sight and consequently has a higher Doppler beaming factor. A weak radio hot spot is indeed observed less than 1 downstream of the bright radio hot spot, but has no optical or X-ray counterpart. By making use of the pc-scale radio and the kpc-scale radio/X-ray data, we derive constraints on the jet Lorentz factors (Gamma_jet) and inclination angles (theta): for a constant jet speed from pc- to kpc-scales, we obtain a Gamma_jet of ~70 for 0106+013, and ~40 for 3C345. On relaxing this assumption, we derive a Gamma_jet of ~2.5 for both the sources. Upper limits on theta of ~13 degrees are obtained for the two quasars. (ABRIDGED)
قيم البحث
اقرأ أيضاً
We present results from continued Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like extended structure. X-rays are detected from 24 of the 39 jets observed so far. We compute the dis
tribution of alpha_rx, the spectral index between the X-ray and radio bands, showing that it is broad, extending at least from 0.8 to 1.2. While there is a general trend that the radio brightest jets are detected most often, it is clear that predicting the X-ray flux from the radio knot flux densities is risky so a shallow X-ray survey is the most effective means for finding jets that are X-ray bright. We test the model in which the X-rays result from inverse Compton (IC) scattering of cosmic microwave background (CMB) photons by relativistic electrons in the jet moving with high bulk Lorentz factor nearly along the line of sight. Depending on how the jet magnetic fields vary with z, the observed X-ray to radio flux ratios do not follow the redshift dependence expected from the IC-CMB model. For a subset of our sample with known superluminal motion based on VLBI observations, we estimate the angle of the kpc-scale jet to the line of sight by considering the additional information in the bends observed between pc- and kpc-scale jets. These angles are sometimes much smaller than estimates based on the IC-CMB model with a Lorentz factor of 15, indicating that these jets may decelerate significantly from pc scales to kpc scales.
We investigate the polarization of Compton scattered X-rays from relativistic jets in active galactic nuclei using Monte Carlo simulations. We consider three scenarios: scattering of photons from an accretion disk, scattering of cosmic microwave back
ground (CMB) photons, and synchrotron self-Comptonization (SSC) within the jet. For Comptonization of thermal disk photons or CMB photons the maximum linear polarization attained is slightly over 20% at viewing angles close to 90 degrees. The value decreases with the viewing inclination. For SSC, the maximum value may exceed 80%. The angle dependence is complicated, and it varies with the photon injection sites. Our study demonstrates that X-ray polarization, in addition to multi-wavelength spectra, can distinguish certain models for emission and particle acceleration in relativistic jets.
This work presents the results of a Chandra study of 21 broad absorption line (BAL) radio-loud quasars (RLQs). We conducted a Chandra snapshot survey of 12 bright BAL RLQs selected from SDSS/FIRST data and possessing a wide range of radio and CIV abs
orption properties. Optical spectra were obtained nearly contemporaneously with the Hobby-Eberly Telescope; no strong flux or BAL variability was seen between epochs. We also include in our sample 9 additional BAL RLQs possessing archival Chandra coverage. We compare the properties of (predominantly high-ionization) BAL RLQs to those of non-BAL RLQs as well as to BAL radio-quiet quasars (RQQs) and non-BAL RQQs for context. All 12 snapshot and 8/9 archival BAL RLQs are detected, with observed X-ray luminosities less than those of non-BAL RLQs having comparable optical/UV luminosities by typical factors of 4.1-8.5. (BAL RLQs are also X-ray weak by typical factors of 2.0-4.5 relative to non-BAL RLQs having both comparable optical/UV and radio luminosities.) However, BAL RLQs are not as X-ray weak relative to non-BAL RLQs as are BAL RQQs relative to non-BAL RQQs. While some BAL RLQs have harder X-ray spectra than typical non-BAL RLQs, some have hardness ratios consistent with those of non-BAL RLQs, and there does not appear to be a correlation between X-ray weakness and spectral hardness, in contrast to the situation for BAL RQQs. RLQs are expected to have X-ray continuum contributions from both disk-corona and small-scale jet emission. While the entire X-ray continuum in BAL RLQs cannot be obscured to the same degree as in BAL RQQs, we calculate that the jet is likely partially covered in many BAL RLQs. We comment briefly on implications for geometries and source ages in BAL RLQs.
This paper presents multiwavelength imaging and broad-band spectroscopy of the relativistic jets in the two nearby radio galaxies 3C 371 and PKS 2201+044, acquired with Chandra, HST, VLA, and Merlin. Radio polarization images are also available. The
two sources stand out as intermediate between FRIs and FRIIs; their cores are classified as BL Lacs, although broad and narrow optical emission lines were detected at times. The multiwavelength images show jet morphologies with the X-ray emission peaking closer to the nucleus than the longer wavelengths. The jets are resolved at all wavelengths in a direction perpendicular to the jet axis. The jets SEDs are consistent with a single spectral component from radio to X-rays, interpreted as synchrotron emission. The SEDs show a progressive softening from the inner to the outer regions of the jet, indicating that the electron break energy moves to lower energies with distance from the core. Overall, the X-ray and multiwavelength properties of the jets of 3C 371 and PKS 2201+044 appear intermediate between those of FRIs and FRIIs.
For more than 15 years, since the days of the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma-Ray Observatory (CGRO; 1991-2000), it has remained an open question why the prominent blazar 3C 345 was not reliably detected at
gamma-ray energies <=20 MeV. Recently a bright gamma-ray source (0FGL J1641.4+3939/1FGL J1642.5+3947), potentially associated with 3C 345, was detected by the Large Area Telescope (LAT) on Fermi. Multiwavelength observations from radio bands to X-rays (mainly GASP-WEBT and Swift) of possible counterparts (3C 345, NRAO 512, B3 1640+396) were combined with 20 months of Fermi-LAT monitoring data (August 2008 - April 2010) to associate and identify the dominating gamma-ray emitting counterpart of 1FGL J1642.5+3947. The source 3C 345 is identified as the main contributor for this gamma-ray emitting region. However, after November 2009 (15 months), a significant excess of photons from the nearby quasar NRAO 512 started to contribute and thereafter was detected with increasing gamma-ray activity, possibly adding flux to 1FGL J1642.5+3947. For the same time period and during the summer of 2010, an increase of radio, optical and X-ray activity of NRAO 512 was observed. No gamma-ray emission from B3 1640+396 was detected.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
