EDP Sciences
Free access
Volume 369, Number 1, April I 2001
Page(s) 57 - 64
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010103

A&A 369, 57-64 (2001)
DOI: 10.1051/0004-6361:20010103

Monitoring of the optical and 2.5-11.7 $\mu$m spectrum and mid-IR imaging of the Seyfert 1 galaxy Mrk 279 with ISO

M. Santos-Lleó1, J. Clavel1, B. Schulz2, B. Altieri1, P. Barr3, D. Alloin4, P. Berlind5, R. Bertram6, 7, D. M. Crenshaw8, R. A. Edelson9, U. Giveon10, K. Horne11, J. P. Huchra5, S. Kaspi10, G. A. Kriss12, J. H. Krolik13, M. A. Malkan14, Yu. F. Malkov15, H. Netzer10, P. T. O'Brien9, B. M. Peterson6, R. W. Pogge6, V. I. Pronik15, 16, B.-C. Qian17, G. A. Reichert18, P. M. Rodríguez-Pascual19, S. G. Sergeev15, 16, J. Tao17, S. Tokarz5, R. M. Wagner6, 7, W. Wamsteker20 and B. J. Wilkes5

1  XMM Science Operations Center, Astrophysics Division, ESA Space Science Department, PO Box 50727, 28080 Madrid, Spain
2  ISO Science Operations Center, Astrophysics Division, ESA Space Science Department, PO Box 50727, 28080 Madrid, Spain
3  Integral Science Operations Center, Astrophysics Division, ESA Space Science Department, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
4  European Southern Observatory, Alonso de Cordova 3107, Vitacura Casilla 19001, Santiago 19, Chile
5  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
6  Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
7  Mailing address: Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
8  Computer Sciences Corporation, Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA
9  Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
10  School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
11  School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, Scotland, UK
12  Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
13  Department of Physics and Astronomy, The John Hopkins University, Baltimore, MD 21218, USA
14  Department of Astronomy, University of California, Math-Science Building, Los Angeles, CA 90024, USA
15  Crimean Astrophysical Observatory, P/O Nauchny, 334413 Crimea, Ukraine
16  Isaac Newton institute of Chile, Crimean Branch
17  Shanghai Astronomical Observatory, 80 Nandan Road, 200030 Shanghai, PR China
18  Raytheon ITSS, Space Science Data Operations Office, NASA Goddard Space Flight Center, Code 631, Greenbelt, MD 20771, USA
19  Universidad Europea de Madrid, Departamento de Física, C/ Tajo sn, Urb. El Bosque, Villaviciosa de Odón, 28670 Madrid, Spain
20  ESA IUE Observatory, PO Box 50727, 28080 Madrid, Spain

(Received 3 January 2000 / Accepted 12 January 2001 )

Mid-infrared images of the Seyfert 1 galaxy Mrk 279 obtained with the ISO satellite are presented together with the results of a one-year monitoring campaign of the 2.5-11.7 $\mu$m spectrum. Contemporaneous optical photometric and spectrophotometric observations are also presented. The galaxy appears as a point-like source at the resolution of the ISOCAM instrument (4-5$\arcsec$). The 2.5-11.7 $\mu$m average spectrum of the nucleus in Mrk 279 shows a strong power law continuum with $\alpha = -0.80\pm0.05$ ( ${
F_{\nu} \propto \nu^{\alpha}}$) and weak PAH emission features. The Mrk 279 spectral energy distribution shows a mid-IR bump, which extends from 2 to 15-20 $\mu$m. The mid-IR bump is consistent with thermal emission from dust grains at a distance of $\ga
100$ lt-d. No significant variations of the mid-IR flux have been detected during our observing campaign, consistent with the relatively low amplitude (~10% rms) of the optical variability during the campaign. The time delay for H$\beta$ line emission in response to the optical continuum variations is $\tau = 16.7^{+5.3}_{-5.6}$ days, consistent with previous measurements.

Key words: galaxies: active -- galaxies: individual: Mrk 279 -- galaxies: nuclei -- galaxies: Seyfert -- infrared: galaxies

Offprint request: M. Santos-Lleó, msantos@xmm.vilspa.esa.es

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