Blasts and shocks in the disc of NGC 4258



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Jiménez Vicente, J. and Mediavilla, E. and Castillo Morales, África and Battaner, E. (2010) Blasts and shocks in the disc of NGC 4258. Monthly notices of the Royal Astronomical Society, 406 (1). pp. 181-186. ISSN 0035-8711

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We present integral field spectroscopic observations of the central region of the active galaxy NGC 4258 obtained with the fibre IFU system INTEGRAL. We have been able to detect cold neutral gas by means of the interstellar NaD doublet absorption and to trace its distribution and kinematics with respect to the underlying disc. The neutral gas is blueshifted with projected velocities in the 120-370 km s(-1) range. We have also detected peculiar kinematics in part of the ionized gas in this region by means of a careful kinematic decomposition. The bipolar spatial distribution of the broader component is roughly coincident with the morphology of the X-ray diffuse emission. The kinematics of this gas can be explained in terms of expansion at very high (projected) velocities of up to 300 km s(-1). The observations also reveal the existence of a strip of neutral gas, parallel to the major kinematic axis, that is nearly coincident with a region of very high [S II]/H alpha ratio tracing the shocked gas. Our observations are consistent with the jet model presented by Wilson, Yang & Cecil in which a cocoon originating from the nuclear jet is shocking the gas in the galaxy disc. Alternatively, our observations are also consistent with the bipolar hypershell model of Sofue and Sofue & Vogler. On balance, we prefer the latter model as the most likely explanation for the puzzling features of this peculiar object.

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This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2010 The Authors. Journal compilation © 2010 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. We are grateful to the anonymous referee for his valuable comments which have led to an improvement in this paper. This paper has been supported by the 'Secretaría de Estado de Política Científica y Tecnológica' (AYA2007-67625-C02-02) and by the 'Consejería de Ciencia y Tecnología de la Junta de Andalucía' (FQM-108, P05-FQM-792). AC-M acknowledges support from the Juan de la Cierva Programme financed by the Spanish MICINN and from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2006-02358. This research has made use of NASA/IPAC Extragalactic Database (NED) which is operated by the JPL, Caltech, under contract with NASA. We have used observations made with the NASA/ESA HST, obtained from the data archive at the STScI. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

Uncontrolled Keywords:Optical-fiber system; Anomalous arms; Bidimensional spectroscopy; Central region; Braided jets; NGC-4258; Galaxies; Discovery; Emission; Bubbles
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:30346
Deposited On:26 May 2015 07:45
Last Modified:10 Dec 2018 15:05

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