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

Journal Article · Sun Mar 20 04:00:00 EST 2005 · The Astrophysical Journal

DOI:https://doi.org/10.1086/427898· OSTI ID:1442476

Giroletti, M. ^[1]; Taylor, G. B. ^[2]; Giovannini, G. ^[1]

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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)

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).

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1442476
• Report Number(s): SLAC-PUB--10929
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 622; ISSN 0004-637X
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS