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تسجيل مستخدم جديدThe two sided parsec scale structure of the Low Luminosity Active Galactic Nucleus in NGC 4278
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G. Giovannini
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We present new Very Long Baseline Interferometry observations of the LINER galaxy NGC 4278 with a linear resolution of < 0.1 pc. Our radio data reveal a two sided structure, with symmetric S-shaped jets emerging from a flat spectrum core. By comparing the positions of the components in two epochs, we measure motions corresponding to apparent velocities < 0.2 c, and to ages in the range 8.3 - 65.8 years. From our measurements, we derive that NGC 4278 has mildly relativistic jets (beta aprox 0.75), closely aligned to the line-of-sight (2 deg < theta < 4 deg). We also present a flux density history for the source with data between 1972 and 2003. All these arguments indicates that the low power radio emission from NGC 4278 is emitted via the synchrotron process by relativistic particles accelerated by a supermassive black hole.
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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 GHz and 8.4 GHz and have a linear
resolution of <0.1 pc. Our radio data reveal a two sided structure, with symmetric S-shaped jets emerging from a flat spectrum core. We fit the jet brightness with gaussian components, which we identify from a previous observation taken five 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 < 0.2c, and to ages in the range 8.3 - 65.8 years. Assuming that the radio morphology is intrinsically symmetric and its appearance is governed by Doppler beaming effects, we find that NGC4278 has mildly relativistic jets (beta ~ 0.75), closely aligned to the line-of-sight (2 degrees < theta < 4 degrees). 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 fit by a relatively steep power-law (alpha = 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 AGNs.
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The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 1
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