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Title: SIX YEARS OF FERMI-LAT AND MULTI-WAVELENGTH MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 120: JET DISSIPATION AT SUB-PARSEC SCALES FROM THE CENTRAL ENGINE

Abstract

In this paper, we present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240–56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the γ-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a γ-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ~0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Basedmore » on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the γ rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. Finally, we also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.« less

Authors:
 [1];  [2];  [2];  [3]; ORCiD logo [4];  [5];  [6];  [7];  [7];  [5]
  1. Hiroshima University (Japan). Hiroshima Astrophysical Science Center
  2. Institute of Space and Astronautical Science (Japan)
  3. Naval Research Laboratory, Washington, DC (United States). Space Science Division
  4. Institute of Space and Astronautical Science (Japan) ; Jagiellonian University (Poland). Astronomical Observatory
  5. Hiroshima University (Japan). Department of Physical Sciences
  6. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  7. Waseda University, Tokyo (Japan). Research Institute for Science and Engineering
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1355174
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal. Letters
Additional Journal Information:
Journal Volume: 799; Journal Issue: 2; Journal ID: ISSN 2041-8213
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; radiation mechanisms; non-thermal — galaxies; active — galaxies; jets — gamma rays; galaxies — radio continuum; galaxies — galaxies; individual (3C 120)

Citation Formats

Tanaka, Y. T., Doi, A., Inoue, Y., Cheung, C. C., Stawarz, L., Fukazawa, Y., Gurwell, M. A., Tahara, M., Kataoka, J., and Itoh, R.. SIX YEARS OF FERMI-LAT AND MULTI-WAVELENGTH MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 120: JET DISSIPATION AT SUB-PARSEC SCALES FROM THE CENTRAL ENGINE. United States: N. p., 2015. Web. doi:10.1088/2041-8205/799/2/L18.
Tanaka, Y. T., Doi, A., Inoue, Y., Cheung, C. C., Stawarz, L., Fukazawa, Y., Gurwell, M. A., Tahara, M., Kataoka, J., & Itoh, R.. SIX YEARS OF FERMI-LAT AND MULTI-WAVELENGTH MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 120: JET DISSIPATION AT SUB-PARSEC SCALES FROM THE CENTRAL ENGINE. United States. doi:10.1088/2041-8205/799/2/L18.
Tanaka, Y. T., Doi, A., Inoue, Y., Cheung, C. C., Stawarz, L., Fukazawa, Y., Gurwell, M. A., Tahara, M., Kataoka, J., and Itoh, R.. Fri . "SIX YEARS OF FERMI-LAT AND MULTI-WAVELENGTH MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 120: JET DISSIPATION AT SUB-PARSEC SCALES FROM THE CENTRAL ENGINE". United States. doi:10.1088/2041-8205/799/2/L18. https://www.osti.gov/servlets/purl/1355174.
@article{osti_1355174,
title = {SIX YEARS OF FERMI-LAT AND MULTI-WAVELENGTH MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 120: JET DISSIPATION AT SUB-PARSEC SCALES FROM THE CENTRAL ENGINE},
author = {Tanaka, Y. T. and Doi, A. and Inoue, Y. and Cheung, C. C. and Stawarz, L. and Fukazawa, Y. and Gurwell, M. A. and Tahara, M. and Kataoka, J. and Itoh, R.},
abstractNote = {In this paper, we present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240–56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the γ-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a γ-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ~0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the γ rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. Finally, we also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.},
doi = {10.1088/2041-8205/799/2/L18},
journal = {The Astrophysical Journal. Letters},
number = 2,
volume = 799,
place = {United States},
year = {Fri Jan 23 00:00:00 EST 2015},
month = {Fri Jan 23 00:00:00 EST 2015}
}

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Cited by: 12works
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  • We present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240–56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the γ-ray and VLBA phenomena in temporal proximity to each other, itmore » is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a γ-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ∼0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the γ rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. We also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.« less
  • We present unambiguous evidence for a parsec scale wind in the broad-line radio galaxy 3C 382, the first radio-loud active galactic nucleus, with R{sub L} = log{sub 10}(f{sub 5GHz}/f{sub 4400})>1, whereby an outflow has been measured with X-ray grating spectroscopy. A 118 ks Chandra grating (HETG) observation of 3C 382 has revealed the presence of several high ionization absorption lines in the soft X-ray band, from Fe, Ne, Mg, and Si. The absorption lines are blueshifted with respect to the systemic velocity of 3C 382 by -840 {+-} 60 km s{sup -1} and are resolved by Chandra with a velocitymore » width of {sigma} = 340 {+-} 70 km s{sup -1}. The outflow appears to originate from a single zone of gas of column density N{sub H} = 1.3 x 10{sup 21} cm{sup -2} and ionization parameter log({xi}/erg cm s{sup -1}) = 2.45. From the above measurements we calculate that the outflow is observed on parsec scales, within the likely range from 10to1000 pc, i.e., consistent with an origin in the narrow-line region.« less
  • We present results from a multiyear monitoring campaign of the broad-line radio galaxy 3C 120, using the Rossi X-ray Timing Explorer for nearly five years of observations. Additionally, we present coincident optical monitoring using data from several ground-based observatories. Both the X-ray and optical emission are highly variable and appear to be strongly correlated, with the X-ray emission leading the optical by 28 days. The X-ray power density spectrum is best fit by a broken power law, with a low-frequency slope of -1.2, breaking to a high-frequency slope of -2.1, and a break frequency of log {nu}{sub b} = -5.75more » Hz, or 6.5 days. This value agrees well with the value expected based on 3C 120's mass and accretion rate. We find no evidence for a second break in the power spectrum. Combined with a moderately soft X-ray spectrum ({gamma} = 1.8) and a moderately high accretion rate, this indicates that 3C 120 fits in well with the high/soft variability state found in most other active galactic nuclei. Previous studies have shown that the spectrum has a strong Fe K{alpha} line, which may be relativistically broadened. The presence of this line, combined with a power spectrum similar to that seen in Seyfert galaxies, suggests that the majority of the X-ray emission in this object arises in or near the disk, and not in the jet.« less
  • We report a relation between radio emission in the inner jet of the Seyfert galaxy 3C 120 and optical continuum emission in this galaxy. Combining the optical variability data with multi-epoch high-resolution very long baseline interferometry observations reveals that an optical flare rises when a superluminal component emerges into the jet, and its maxima is related to the passage of such component through the location of a stationary feature at a distance of {approx}1.3 pc from the jet origin. This indicates that a significant fraction of the optical continuum produced in 3C 120 is non-thermal, and it can ionize materialmore » in a sub-relativistic wind or outflow. We discuss implications of this finding for the ionization and structure of the broad emission line region, as well as for the use of broad emission lines for determining black hole masses in radio-loud active galactic nucleus.« less
  • We present the proper motion of the sub-parsec-scale jet in a nearby elliptical galaxy 3C 66B. Observations were made at 2.3 GHz and 8.4 GHz at 10 epochs over four years, using the Very Long Baseline Array for all epochs and the Effelsberg 100 m telescope for the last epoch. The 8.4 GHz images showed that the proper motion increases from 0.21 to 0.70 mas yr{sup -1}, corresponding to an apparent speed of 0.30-0.96c, with a distance from the core on a sub-parsec scale. Our investigation suggests that the apparent increase in the proper motion can be explained by changesmore » in the viewing angle, according to a relativistic beaming model. However, we still cannot eliminate the possibility that acceleration of the jet outflow speed or changes in the emissivity profile in the two-zone jet might be found in 3C 66B.« less