scholarly journals Shockwaves in Extended Near-Relativistic Jets

1988 ◽  
Vol 129 ◽  
pp. 85-86 ◽  
Author(s):  
Peter L. Biermann ◽  
Peter A. Strittmatter
Keyword(s):  
Near Infrared ◽  
Wave Spectrum ◽  
Synchrotron Emission ◽  
Relativistic Jets ◽  
Kolmogorov Type ◽  
Independent Evidence ◽  
Continuous Energy ◽  
Upper Limits ◽  
Thermal Sources ◽  
Turbulent Wave

The origin of the sharp near infrared cutoff in the continuous energy distribution of many compact non-thermal sources (active nuclei or knots in jets) is considered under the assumption that particle acceleration takes place in shockwaves. Energy losses due to synchrotron emission and Compton interactions set upper limits to both electron and proton energies. In this case the upstream disturbance of the flow is dominated by the most energetic protons which are postulated, by analogy with the solar wind, to excite a turbulent wave spectrum of Kolmogorov type in this region. We predict for near relativistic flows a spectral cutoff near 3 1014 Hz independent of magnetic field. The observation of a sharp spectral cutoff near 3 1014 Hz is thus independent evidence for near–relativistic flows in jets.

scholarly journals SDSS J211852.96−073227.5: The first non-local, interacting, late-type intermediate Seyfert galaxy with relativistic jets

2020 ◽  
Vol 636 ◽  
pp. L12 ◽  
Author(s):  
E. Järvelä ◽  
M. Berton ◽  
S. Ciroi ◽  
E. Congiu ◽  
A. Lähteenmäki ◽  
...  
Keyword(s):  
Near Infrared ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Late Type ◽  
Host Galaxies ◽  
Relativistic Jets ◽  
Galaxy Interactions ◽  
Non Local ◽  
First Time

It has been often suggested that a tangible relation exists between relativistic jets in active galactic nuclei (AGN) and the morphology of their host galaxies. In particular, relativistic jets may commonly be related to merging events. Here we present for the first time a detailed spectroscopic and morphological analysis of a Seyfert galaxy, SDSS J211852.96−073227.5, at z = 0.26. This source has previously been classified as a gamma-ray emitting narrow-line Seyfert 1 galaxy. We re-observed it with the 6.5 m Clay Telescope and these new, high-quality spectroscopic data have revealed that it is actually an intermediate-type Seyfert galaxy. Furthermore, the results of modelling the Ks-band near-infrared images obtained with the 6.5 m Baade Telescope indicate that the AGN is hosted by a late-type galaxy in an interacting system, strengthening the suggested connection between galaxy interactions and relativistic jets.

scholarly journals X-Ray and Near-Infrared Spectroscopy of Dim X-Ray Point Sources Constituting the Galactic Ridge X-Ray Emission

2014 ◽  
Vol 1 (1) ◽  
pp. 222-226
Author(s):  
Kumiko Morihana ◽  
Masahiro Tsujimoto ◽  
Ken Ebisawa
Keyword(s):  
Near Infrared ◽  
Cataclysmic Variables ◽  
Point Sources ◽  
X Ray ◽  
Nir Imaging ◽  
Group A ◽  
Field L ◽  
Imaging And Spectroscopy ◽  
Group B ◽  
Thermal Sources

We present the results of X-ray and Near-Infrared observations of the Galactic Ridge X-ray Emission (GRXE). We extracted 2,002 X-ray point sources in the <em>Chandra</em> Bulge Field (l =0°.113, b = 1°.424) down to ~10<sup>-14.8</sup> ergscm<sup>-2</sup>s<sup>-1</sup> in 2-8 keV band with the longest observation (900 ks) of the GRXE. Based on X-ray brightness and hardness, we classied the X-ray point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). In order to know populations of the X-ray point sources, we carried out NIR imaging and spectroscopy observation. We identied 11% of X-ray point sources with NIR and extracted NIR spectra for some of them. Based on X-ray and NIR properties, we concluded that non-thermal sources in the group A are mostly active galactic nuclei and the thermal sources are mostly white dwarf binaries such as cataclysmic variables (CVs) and Pre-CVs. We concluded that the group B and C sources are X-ray active stars in flare and quiescence, respectively.

Recollimation shocks in relativistic jets

2018 ◽  
Vol 27 (10) ◽  
pp. 1844011 ◽  
Author(s):  
José M. Martí ◽  
Manel Perucho ◽  
José L. Gómez ◽  
Antonio Fuentes
Keyword(s):  
Magnetic Fields ◽  
Numerical Simulations ◽  
Theoretical Background ◽  
Synchrotron Emission ◽  
Relativistic Jets ◽  
Dominant Type ◽  
X Ray ◽  
Extragalactic Jets ◽  
X Ray Binaries ◽  
Selection Of

Recollimation shocks (RS) appear associated with relativistic flows propagating through pressure mismatched atmospheres. Astrophysical scenarios invoking the presence of such shocks include jets from AGNs and X-ray binaries and GRBs. We shall start reviewing the theoretical background behind the structure of RS in overpressured jets. Next, basing on numerical simulations, we will focus on the properties of RS in relativistic steady jets threaded by helical magnetic fields depending on the dominant type of energy. Synthetic radio maps from the simulation of the synchrotron emission for a selection of models in the context of parsec-scale extragalactic jets will also be discussed.

scholarly journals Middle-Infrared Observations of DENIS J0255-4700

2003 ◽  
Vol 211 ◽  
pp. 421-422
Author(s):  
Michelle Creech-Eakman ◽  
Eugene Serabyn ◽  
Glenn S. Orton ◽  
Thomas L. Hayward
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Infrared Photometry ◽  
Atmospheric Models ◽  
Brown Dwarf ◽  
Infrared Observations ◽  
Upper Limits ◽  
Model Independent ◽  
Data Yield ◽  
Middle Infrared

The first infrared photometry of an L-type brown dwarf, DENIS J0255-4700, includes N-band and narrow-band 8.8-μm detections, with upper limits in narrow-band 10.3 and 11.7 μm. Model-independent blackbody fits of existing data yield Teff = 1250 – 1750 K, with models favoring the lower end of that range. Dusty atmospheric models by Allard, Burrows and Marley which match the near-infrared photometry are not completely consistent with our mid-infrared photometry.

scholarly journals Upper Limits for the Luminosity of a dM Companion in AM Herculis Objects

1980 ◽  
Vol 88 ◽  
pp. 471-472
Author(s):  
S. Tapia ◽  
G. V. Coyne
Keyword(s):  
Binary Systems ◽  
Near Infrared ◽  
Close Binary ◽  
Optical Identification ◽  
New Class ◽  
Upper Limits ◽  
Infrared Spectral ◽  
Cyclotron Emission ◽  
High Degree ◽  
The Magnetic Field

SummaryThe quest for optical identification of X-ray sources has revealed a new class of variables currently formed by AM Her, AN UMa, VV Pup, and the most recent member, 2A 0311-227 (for which a variable star designation will be available soon). These objects show many of the variations common to close binary systems where mass transfer is under way. However, they are distinguished by the high degree (10 to 35 %) of linear and circular polarization observed in the optical and near infrared spectral regions. Apparently the polarization is due to cyclotron emission of electrons located in a region where the magnetic field strength is about 108 gauss.

scholarly journals Near Infrared and Radio Observations of Distant Galaxies

1983 ◽  
Vol 104 ◽  
pp. 85-86
Author(s):  
R. A. Laing ◽  
F. N. Owen ◽  
J. J. Puschell
Keyword(s):  
Near Infrared ◽  
Angular Size ◽  
Radio Galaxies ◽  
Radio Observations ◽  
Chance Coincidence ◽  
Distant Galaxies ◽  
Upper Limits

This paper is concerned with the distant radio galaxies in a sample of bright sources selected at 178 MHz by Laing, Riley & Longair (1982). This sample is 96% complete for sources with θ < 10′ and the bias of the 3CR catalogue against sources of large angular size has also been reduced. Deep optical searches have located many candidate identifications, but the probability of a chance coincidence with an unrelated object is appreciable, especially in the faintest cases, unless the area to be searched is small. We have therefore mapped the sources with candidate identifications having V > 20, using the VLA at a wavelength of 6 cm (Laing, Owen & Puschell, in preparation), in order to search for radio cores. We have so far located cores in 16/23 sources and set 5σ upper limits of 0.6 mJy for the remainder. None of the cores had been detected previously. In all cases, the cores coincide with optical objects, although one source (3C 340) had been misidentified. Several ambiguities have now been resolved.

scholarly journals On the radio image of relativistic jets – I. Internal structure, Doppler boosting, and polarization maps

2019 ◽  
Vol 488 (1) ◽  
pp. 224-233 ◽  
Author(s):  
A V Chernoglazov ◽  
V S Beskin ◽  
V I Pariev
Keyword(s):  
Active Galactic Nuclei ◽  
Internal Structure ◽  
Linear Polarization ◽  
Ambient Pressure ◽  
Galactic Nuclei ◽  
Synchrotron Emission ◽  
Relativistic Jets ◽  
Radio Image ◽  
Radial Profiles

ABSTRACT In this first paper from forthcoming series of works devoted to radio image of relativistic jets from active galactic nuclei the role of internal structure of a flow is discussed. We determine the radial profiles of all physical values for reasonable Michel magnetization parameter σM and ambient pressure Pext. Maps of Doppler boosting factor δ and observed directions of linear polarization of synchrotron emission are also constructed.

scholarly journals KiDS+VIKING-450: A new combined optical and near-infrared dataset for cosmology and astrophysics

2019 ◽  
Vol 632 ◽  
pp. A34 ◽  
Author(s):  
Angus H. Wright ◽  
Hendrik Hildebrandt ◽  
Konrad Kuijken ◽  
Thomas Erben ◽  
Robert Blake ◽  
...  
Keyword(s):  
Excellent Agreement ◽  
Near Infrared ◽  
Primary Data ◽  
Systematic Uncertainties ◽  
Level Data ◽  
Upper Limits ◽  
Data Products ◽  
Infrared Surveys ◽  
Stellar Masses ◽  
Mass Functions

We present the curation and verification of a new combined optical and near infrared dataset for cosmology and astrophysics, derived by combining ugri-band imaging from the Kilo-Degree Survey (KiDS) and ZYJHKs-band imaging from the VISTA Kilo degree Infrared Galaxy (VIKING) survey. This dataset is unrivaled in cosmological imaging surveys due to the combination of its area (458 deg2 before masking), depth (r ≤ 25), and wavelength coverage (ugriZYJHKs). This combination of survey depth, area, and (most importantly) wavelength coverage allows significant reductions in systematic uncertainties (i.e. reductions of between 10% and 60% in bias, outlier rate, and scatter) in photometric-to-spectroscopic redshift comparisons, compared to the optical-only case at photo-z above 0.7. The complementarity between our optical and near infrared surveys means that over 80% of our sources, across all photo-z, have significant detections (i.e. not upper limits) in our eight reddest bands. We have derived photometry, photo-z, and stellar masses for all sources in the survey, and verified these data products against existing spectroscopic galaxy samples. We demonstrate the fidelity of our higher-level data products by constructing the survey stellar mass functions in eight volume-complete redshift bins. We find that these photometrically derived mass functions provide excellent agreement with previous mass evolution studies derived using spectroscopic surveys. The primary data products presented in this paper are made publicly available through the KiDS survey website.

EFFECT OF RADIATIVE LOSSES ON PARTICLE ACCELERATION AT RELATIVISTIC SHOCKS

2008 ◽  
Vol 17 (10) ◽  
pp. 1819-1826
Author(s):  
PAUL DEMPSEY ◽  
PETER DUFFY
Keyword(s):  
Large Degree ◽  
Lorentz Factor ◽  
High Energy ◽  
Synchrotron Emission ◽  
Relativistic Jets ◽  
Nonrelativistic Approximation ◽  
Relativistic Shocks ◽  
Degree Of Anisotropy ◽  
Radiative Losses ◽  
High Energy Particles

We investigate the acceleration and simultaneous radiative losses of electrons in the vicinity of relativistic shocks. Particles undergo pitch angle diffusion, gaining energy as they cross the shock by the Fermi mechanism and also emitting synchrotron radiation in the ambient magnetic field. Using a semi-analytic approach we find that the cut-off energy differs greatly from the nonrelativistic approximation. Our results also show that, while low energy particles remain nearly isotropic, high energy particles downstream of the shock have a large degree of anisotropy which increases with the Lorentz factor of the shock. The implications for the synchrotron emission of relativistic jets, such as those in microquasars and blazars, are discussed.

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