EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 386/2 Article
Free access article

Issue A&A
Volume 386, Number 2, May I 2002
Page(s) 399 - 414
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20020245



A&A 386, 399-414 (2002)
DOI: 10.1051/0004-6361:20020245

The signature of high-velocity gas in the spectra of NGC 4151

M. Contini1, 2, S. M. Viegas2 and M. A. Prieto3

1  School of Physics & Astronomy, Tel Aviv University, 69978 Tel Aviv, Israel
2  Instituto Astronômico e Geofísico, USP, Av. Miguel Stefano 4200, 04301-904 São Paulo, Brazil
3  European Southern Observatory, 85748 Garching, Germany

(Received 5 July 2001 / Accepted 5 February 2002 )

Abstract
The multiwavelength emission spectrum and associated velocity field of the Seyfert prototype NGC 4151 is modeled. Since the thirties NGC 4151 has been the subject of extensive modeling, nuclear photoionization being the basic approach considered by all authors. HST data has impressively revealed the existence of a large range of velocities (100-1500  $\rm km\, s^{-1}$) dominating the emitting clouds in the extended emission line region of the galaxy. Following this observational result, a revision of the photoionization modeling approach applied to NGC 4151 is presented. It is concluded that a mixture of radiation-dominated clouds and shock-dominated clouds are required to explain the multiwavelength line and continuum spectra of the galaxy. The relative contribution of shock excitation versus photoionization is consistently modeled along the nebulae taking into account the spatial variation of both flux and velocity of main optical and UV lines. The multiwavelength continuum spectrum of NGC 4151 is then nicely accounted for by a combination of nuclear emission at high energy, gas Bremsstrahlung, and dust emission. The last two phenomena are directly linked to the composite shock and photoionization excitation of the gas. The radio SED however is found dominated by synchrotron emission created by the Fermi mechanism at the shock front. In addition, a $3\times10^3$ K black body component accounts for the host galaxy contribution. As a result of the modeling, silicon is found depleted by a high factor and included in dust grains, while the N/C abundance ratio is found compatible with cosmic values.


Key words: galaxies: nuclei -- galaxies: Seyfert -- shock waves -- galaxies: individual: NGC 4151 -- X-ray: galaxies

Offprint request: M. Contini, contini@ccsg.tau.ac.il

SIMBAD Objects



© ESO 2002


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.