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Title: The Two–sided Parsec–Scale Structure of the Low–Luminosity Active Galactic Nucleus in NGC 4278

Abstract

Here, we present new very long baseline interferometry observations of the LINER galaxy NGC 4278. The observations were taken with the Very Long Baseline Array (VLBA) and a single antenna of the Very Large Array (VLA) at 5 and 8.4 GHz and have a linear resolution of lesssim0.1 pc. Our radio data reveal a two-sided structure, with symmetric img1.gif-shaped jets emerging from a flat-spectrum core. We fit the jet brightness with Gaussian components, which we identify from a previous observation taken 5 years before. By comparing the positions of the components in the two epochs, we measure motions between 0.45 ± 0.14 and 3.76 ± 0.65 mas, corresponding to apparent velocities lesssim0.2c and to ages in the range 8.3-65.8 yr. Assuming that the radio morphology is intrinsically symmetric and its appearance is governed by Doppler beaming effects, we find that NGC 4278 has mildly relativistic jets (β ~ 0.75), closely aligned to the line of sight (2° ≤ θ ≤ 4°). Alternatively, the source could be oriented at a larger angle and asymmetries could be related to the jet interaction with the surrounding medium. We also present new simultaneous VLA observations between 1.4 and 43 GHz, and a 5 GHzmore » light curve between 1972 and 2003. The radio spectrum can be fitted by a relatively steep power law (α = 0.54). We find significant variability at 5 GHz. All these arguments indicate that the radiation from NGC 4278 is emitted via the synchrotron process by relativistic particles accelerated by a supermassive black hole. Despite a much lower power, this is the same process that takes place in ordinary radio-loud active galactic nuclei (AGNs).« less

Authors:
 [1];  [2];  [1]
  1. Istituto di Radioastronomia, Bologna (Italy); Univ. di Bologna, Bologna (Italy)
  2. Kavli Institute of Particle Astrophysics and Cosmology, Menlo Park, CA (United States); National Radio Astronomy Observatory, Socorro, NM (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1442476
Report Number(s):
SLAC-PUB-10929
Journal ID: ISSN 0004-637X; TRN: US1900925
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 622; Journal Issue: 1; Journal ID: ISSN 0004-637X
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Giroletti, M., Taylor, G. B., and Giovannini, G. The Two–sided Parsec–Scale Structure of the Low–Luminosity Active Galactic Nucleus in NGC 4278. United States: N. p., 2005. Web. doi:10.1086/427898.
Giroletti, M., Taylor, G. B., & Giovannini, G. The Two–sided Parsec–Scale Structure of the Low–Luminosity Active Galactic Nucleus in NGC 4278. United States. doi:10.1086/427898.
Giroletti, M., Taylor, G. B., and Giovannini, G. Sun . "The Two–sided Parsec–Scale Structure of the Low–Luminosity Active Galactic Nucleus in NGC 4278". United States. doi:10.1086/427898. https://www.osti.gov/servlets/purl/1442476.
@article{osti_1442476,
title = {The Two–sided Parsec–Scale Structure of the Low–Luminosity Active Galactic Nucleus in NGC 4278},
author = {Giroletti, M. and Taylor, G. B. and Giovannini, G.},
abstractNote = {Here, we present new very long baseline interferometry observations of the LINER galaxy NGC 4278. The observations were taken with the Very Long Baseline Array (VLBA) and a single antenna of the Very Large Array (VLA) at 5 and 8.4 GHz and have a linear resolution of lesssim0.1 pc. Our radio data reveal a two-sided structure, with symmetric img1.gif-shaped jets emerging from a flat-spectrum core. We fit the jet brightness with Gaussian components, which we identify from a previous observation taken 5 years before. By comparing the positions of the components in the two epochs, we measure motions between 0.45 ± 0.14 and 3.76 ± 0.65 mas, corresponding to apparent velocities lesssim0.2c and to ages in the range 8.3-65.8 yr. Assuming that the radio morphology is intrinsically symmetric and its appearance is governed by Doppler beaming effects, we find that NGC 4278 has mildly relativistic jets (β ~ 0.75), closely aligned to the line of sight (2° ≤ θ ≤ 4°). Alternatively, the source could be oriented at a larger angle and asymmetries could be related to the jet interaction with the surrounding medium. We also present new simultaneous VLA observations between 1.4 and 43 GHz, and a 5 GHz light curve between 1972 and 2003. The radio spectrum can be fitted by a relatively steep power law (α = 0.54). We find significant variability at 5 GHz. All these arguments indicate that the radiation from NGC 4278 is emitted via the synchrotron process by relativistic particles accelerated by a supermassive black hole. Despite a much lower power, this is the same process that takes place in ordinary radio-loud active galactic nuclei (AGNs).},
doi = {10.1086/427898},
journal = {Astrophysical Journal},
number = 1,
volume = 622,
place = {United States},
year = {2005},
month = {3}
}

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