Very large array H92α and H53α radio recombination line observations of M82

Rodriguez-Rico, C.A.; Viallefond, F.; Zhao, J.H.; Goss, W.M.; Anantharamaiah, K.R.

Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/3007

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DC Field	Value	Language
dc.contributor.author	Rodriguez-Rico, C.A.	-
dc.contributor.author	Viallefond, F.	-
dc.contributor.author	Zhao, J.H.	-
dc.contributor.author	Goss, W.M.	-
dc.contributor.author	Anantharamaiah, K.R.	-
dc.date.accessioned	2007-06-19T11:12:47Z	-
dc.date.available	2007-06-19T11:12:47Z	-
dc.date.issued	2004-12	-
dc.identifier.citation	Astrophysical Journal, 2004, Vol.616, p783-803	en
dc.identifier.issn	0004-637X	-
dc.identifier.issn	1538-4357(Online)	-
dc.identifier.uri	http://hdl.handle.net/2289/3007	-
dc.description	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)	en
dc.description.abstract	We present high angular resolution (0.6") observations made with the Very Large Array of the radio continuum at 8.3 and 43 GHz, as well as H92α and H53α radio recombination lines from the nearby (~3 Mpc) starburst galaxy M82. In the continuum we identify 58 sources at 8.3 GHz, of which 19 have no counterparts in catalogs published at other frequencies. At 43 GHz we identify 18 sources, unresolved at 0.6" resolution, of which five were unknown previously. The spatial distribution of the H92α line is inhomogeneous; we identify 27 features; about half of them are associated with continuum emission sources. Their sizes are typically in the range 2-10 pc. Although observed with poorer signal-to-noise ratio, the H53α line is detected. The line and continuum emission are modeled using a collection of H II regions at different distances from the nucleus. The observations can be interpreted assuming a single-density component, but equally well with two components if constraints originating from previous high-resolution continuum observations are used. The high-density component has a density of ~4×104 cm-3. However, the bulk of the ionization is in regions with densities that are typically a factor of 10 lower. The gas kinematics, using the H92α line, confirms the presence of steep velocity gradient (26 km s-1 arcsec-1) in the nuclear region, as previously reported, in particular from observations of the [Ne II] line at 12 μm. This gradient has about the same amplitude on both sides of the nucleus. Since this steep gradient is observed not only on the major axis but also at large distances along a band at P.A.~150deg, the interpretation in terms of x2 orbits elongated along the minor axis of the bar, which would be observed at an angle close to the inclination of the main disk, seems inadequate. The observed kinematics cannot be modeled using a simple model that consists of a set of circular orbits observed at different tilt angles. Ad hoc radial motions must be introduced to reproduce the pattern of the velocity field. Different families of orbits are indicated since we detect a signature in the kinematics at the transition between the two plateaus observed in the NIR light distribution. These H92α data also reveal the base of the outflow where the injection toward the halo on the northern side occurs. The outflow has a major effect on the observed kinematics, present even in the disk at distances close to the nucleus. The kinematic pattern suggests a connection between the gas flowing in the plane of M82 toward the center; this behavior most likely is due to the presence of a bar and the outflow out of the plane.	en
dc.format.extent	1369960 bytes	-
dc.format.mimetype	application/pdf	-
dc.language.iso	en	en
dc.publisher	The University of Chicago Press for the American Astronomical Society	en
dc.relation.uri	http://adsabs.harvard.edu/cgi-bin/bib_query?2004ApJ...616..783R	en
dc.relation.uri	http://arxiv.org/abs/astro-ph/0408368	en
dc.relation.uri	http://dx.doi.org/10.1086/425109	en
dc.rights	2004 American Astronomical Society	en
dc.subject	Galaxies: Individual: Messier Number: M82	en
dc.subject	Galaxies: ISM	en
dc.subject	Galaxies: Starburst	en
dc.subject	ISM: H II Regions	en
dc.subject	Radio Lines: Galaxies	en
dc.title	Very large array H92α and H53α radio recombination line observations of M82	en
dc.type	Article	en
Appears in Collections:	Research Papers (A&A)

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