The Source of Variable Optical Emission is Localized in the Jet of the Radio Galaxy 3C 390.3 (original) (raw)
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Eprint Arxiv Astro Ph 0512393, 2005
Context. The "central engine" of AGN is thought to be powered by accretion on a central nucleus believed to be a super-massive black hole. The localization and exact mechanism of the energy release in AGN are still not well understood. Aims. We present observational evidence for the link between variability of the radio emission of the compact jet, optical and X-ray continua emission and ejections of new jet components in the radio galaxy 3C 390.3. Methods. The time delays between the light curves of the individual jet components and the light curve of the optical continuum are estimated by using minimization methods and the discret correlation function. Results. We find that the variations of the optical continuum are correlated with radio emission from a stationary feature in the jet. This correlation indicates that the source of variable non-thermal continuum radiation is located in the innermost part of the relativistic jet. Conclusions. We suggest that the continuum emission from the jet and counterjet ionizes material in a subrelativistic outflow surrounding the jet, which results in a formation of two conical regions with broad emission lines (in addition to the conventional broad line region around the central nucleus) at a distance > ∼ 0.4 parsecs from the central engine. Implications for modeling of the broad-line regions are discussed.
Monthly Notices of the Royal Astronomical Society, 2010
Context. The "central engine" of AGN is thought to be powered by accretion on a central nucleus believed to be a super-massive black hole. The localization and exact mechanism of the energy release in AGN are still not well understood. Aims. We present observational evidence for the link between variability of the radio emission of the compact jet, optical and X-ray continua emission and ejections of new jet components in the radio galaxy 3C 390.3. Methods. The time delays between the light curves of the individual jet components and the light curve of the optical continuum are estimated by using minimization methods and the discret correlation function. Results. We find that the variations of the optical continuum are correlated with radio emission from a stationary feature in the jet. This correlation indicates that the source of variable non-thermal continuum radiation is located in the innermost part of the relativistic jet. Conclusions. We suggest that the continuum emission from the jet and counterjet ionizes material in a subrelativistic outflow surrounding the jet, which results in a formation of two conical regions with broad emission lines (in addition to the conventional broad line region around the central nucleus) at a distance > ∼ 0.4 parsecs from the central engine. Implications for modeling of the broad-line regions are discussed.
Following the discovery of a new radio component right before the GeV \gamma-ray detection since 2008 August by Fermi Gamma-ray Space Telescope, we present a detailed study of the kinematics and lightcurve on the central sub-pc scale of 3C 84 using the archival VLBA 43-GHz data covering the period between 2002 January to 2008 November. We find that the new component "C3", previously reported by the observations with the VLBI Exploration of Radio Astrometry (VERA), was already formed in 2003. The flux density of C3 increases moderately until 2008, and then it becomes brighter rapidly after 2008. The radio core, C1, also shows a similar trend. The apparent speed of C3 with reference to the core C1 shows moderate acceleration from 0.10c to 0.47c between 2003 November to 2008 November, but is still sub-relativistic. We further try to fit the observed broadband spectrum by the one-zone synchrotron self-Compton (SSC) model using the measured apparent speed of C3. The fit can rep...
The Astrophysical Journal, 2012
Following the discovery of a new radio component right before the GeV γ -ray detection since 2008 August by the Fermi Gamma-ray Space Telescope, we present a detailed study of the kinematics and light curve on the central sub-parsec scale of 3C 84 using the archival Very Long Baseline Array 43 GHz data covering the period between 2002 January and 2008 November. We find that the new component "C3," previously reported by the observations with the Very Long Baseline Interferometer Exploration of Radio Astrometry, was already formed in 2003. The flux density of C3 increases moderately until 2008, and then it becomes brighter rapidly after 2008. The radio core, C1, also shows a similar trend. The apparent speed of C3 with reference to the core C1 shows moderate acceleration from 0.10c to 0.47c between 2003 November and 2008 November, but is still sub-relativistic. We further try to fit the observed broadband spectrum by the one-zone synchrotron self-Compton model using the measured apparent speed of C3. The fit can reproduce the observed γ -ray emission, but does not agree with the observed radio spectral index between 22 and 43 GHz.
VLBI Observations of a Complete Sample of Radio Galaxies: 10 Years Later
The Astrophysical Journal, 2001
A complete sample of 27 radio galaxies was selected from the B2 and 3CR catalogs, in order to study their properties on the milliarcsecond scale. In the Appendix of this paper we present new radio images for 12 of them. Thanks to the present data, all the sources in this sample have been imaged at mas resolution. We discuss the general results. In particular we stress the evidence for high velocity jets in low power radio galaxies, we compare high and low power sources, and discuss the source properties in the light of the unified scheme models. We derive that the properties of parsec scale jets are similar in sources with different total radio power and kpc scale morphology. From the core-total radio power correlation, we estimate that relativistic jets with Lorentz factor γ in the range 3-10 are present in high and low power radio sources. We discuss also the possible existence of a two velocity structure in parsec scale jets (fast spine and lower velocity external shear layer).
The Astrophysical Journal, 1994
A complete sample of 27 radio galaxies was selected from the B2 and 3CR catalogs, in order to study their properties on the milliarcsecond scale. In the Appendix of this paper we present new radio images for 12 of them. Thanks to the present data, all the sources in this sample have been imaged at mas resolution. We discuss the general results. In particular we stress the evidence for high velocity jets in low power radio galaxies, we compare high and low power sources, and discuss the source properties in the light of the unified scheme models. We derive that the properties of parsec scale jets are similar in sources with different total radio power and kpc scale morphology. From the core-total radio power correlation, we estimate that relativistic jets with Lorentz factor γ in the range 3-10 are present in high and low power radio sources. We discuss also the possible existence of a two velocity structure in parsec scale jets (fast spine and lower velocity external shear layer).
The faint radio sky: VLBA observations of the COSMOS field
Astronomy & Astrophysics
Context. Quantifying the fraction of active galactic nuclei (AGN) in the faint radio population and understanding their relation with star-forming activity are fundamental to studies of galaxy evolution. Very long baseline interferometry (VLBI) observations are able to identify AGN above relatively low redshifts (z > 0.1) since they provide milli-arcsecond resolution. Aims. We have created an AGN catalogue from 2865 known radio sources observed in the Cosmic Evolution Survey (COSMOS) field, which has exceptional multi-wavelength coverage. With this catalogue we intend to study the faint radio sky with statistically relevant numbers and to analyse the AGN-host galaxy co-evolution, making use of the large amount of ancillary data available in the field. Methods. Wide-field VLBI observations were made of all known radio sources in the COSMOS field at 1.4 GHz to measure the AGN fraction, in particular in the faint radio population. We describe in detail the observations, data calibration, source detection and flux density measurements, parts of which we have developed for this survey. The combination of number of sources, sensitivity, and area covered with this project are unprecedented. Results. We have detected 468 radio sources, expected to be AGN, with the Very Long Baseline Array (VLBA). This is, to date, the largest sample assembled of VLBI detected sources in the sub-mJy regime. The input sample was taken from previous observations with the Very Large Array (VLA). We present the catalogue with additional optical, infrared and X-ray information. Conclusions. We find a detection fraction of 20 ± 1%, considering only those sources from the input catalogue which were in principle detectable with the VLBA (2361). As a function of the VLA flux density, the detection fraction is higher for higher flux densities, since at high flux densities a source could be detected even if the VLBI core accounts for a small percentage of the total flux density. As a function of redshift, we see no evolution of the detection fraction over the redshift range 0.5 < z < 3. In addition, we find that faint radio sources typically have a greater fraction of their radio luminosity in a compact core-∼70% of the sub-mJy sources detected with the VLBA have more than half of their total radio luminosity in a VLBI-scale component, whereas this is true for only ∼30% of the sources that are brighter than 10 mJy. This suggests that fainter radio sources differ intrinsically from brighter ones. Across our entire sample, we find the predominant morphological classification of the host galaxies of the VLBA detected sources to be early type (57%), although this varies with redshift and at z > 1.5 we find that spiral galaxies become the most prevalent (48%). The number of detections is high enough to study the faint radio population with statistically significant numbers. We demonstrate that wide-field VLBI observations, together with new calibration methods such as multi-source self-calibration and mosaicing, result in information which is difficult or impossible to obtain otherwise.
The Astrophysical Journal, 1998
We present Hubble Space T elescope Wide Field Planetary Camera 2 broadband red and linear ramp Ðlter (isolating redshifted [O II] j3727) observations and subarcsecond-resolution 15, 22, and 43 GHz VLA observations of the radio-loud quasar 3C 380. We conÐrm the report of de Vries et al. that there is good correspondence between the locations of two optical and radio knots/hot spots in the jet. We show that the optical knots are continuum rather than line emission. The radio-optical spectrum can be Ðtted either by a normal radio spectrum (a D [0.8) with a break somewhere in the infrared or by a steeper single power law (a D [1) (where We suggest that the two knots are radiating optical synchro-S l P la). tron emission. This would make the knots in 3C 380 the most luminous optical knots/hot spots currently known.
2006
We study the correlations between the jet ejection event and changes in the continuum emission of the radio-loud galaxy 3C 390.3, using the archived monitoring data in radio, optical and X-ray. We present evidence for the link between the variable optical continuum and a stationary radio feature in the jet. The ejection of radio components happens during, or after, the dip in the X-ray light curve. Moreover, during the X-ray dip the flux variability is significantly reduced while the hardness ratio and its variance becomes harder. These findings strengthen the idea of similarity between active galactic nuclei (AGN) and microquasars, pointing towards a common physical mechanism acting in the disk-jet system. Other similarities are also discussed on the basis of comparision between 3C 390.3 and the microquasars GRS 1915+105 and Cyg X-1. If the analogy (based on linear mass scaling) between the ejection rates of the microquasar GRS 1915+105 and 3C 390.3 is correct, then the rate of eje...
Opacity in parsec-scale jets of active galactic nuclei: VLBA study from 1.4 to 15 GHz
2008
In extragalactic jets, the apparent position of the bright/narrow end (the core) depends on the observing frequency, owing to synchrotron self-absorption and external absorption. The effect must be taken into account in order to achieve unbiased results from multi-frequency VLBI data on AGN jets. Multi-frequency core shift measurements supplemented by other data enable estimating the absolute geometry and a number of fundamental physical properties of the jets and their environment. We have previously measured the shift between 13 and 3.6 cm in a sample of 29 AGNs to range between 0 and 1.4 mas. In these proceedings, we present and discuss first results of our follow-up study using VLBA between 1.4 and 15.4 GHz.