ISOGAL: A deep survey of the obscured inner Milky Way with ISO at 7 μm and 15 μm and with DENIS in the near-infrared ^*,**,***

¹ Institut d'Astrophysique de Paris, CNRS, 98 bis Bd. Arago, 75014 Paris
² Institute of Astronomy, Cambridge, UK
³ GEPI, Observatoire de Paris, France
⁴ Physical Research Laboratory, Ahmedabad, India
⁵ University of Victoria, Canada
⁶ ISO Data Centre, ESA, Villafranca, Spain
⁷ Instituut voor Sterrenkunde, K. U. Leuven, Belgium
⁸ UMS-CNRS 2201, Observatoire de Paris, France
⁹ SIRTF Science Center, California Institute of Technology, Pasadena, CA, USA
¹⁰ ESO, Garching, Germany
¹¹ Indian Institute of Science, Bangalore, India
¹² LESIA, Observatoire de Paris, France
¹³ Air Force Research Laboratory, Hanscom AFB, MA, USA
¹⁴ Observatoire de Strasbourg, France
¹⁵ OCA, Nice, France
¹⁶ Osservatorio Astrofisico di Arcetri, Firenze, Italy
¹⁷ ESO, Santiago, Chile
¹⁸ MPIE, Garching, Germany
¹⁹ South African Astronomical Observatory, South Africa
²⁰ Max-Planck Institut für Astronomie, Heidelberg, Germany
²¹ Leiden Observatory, Leiden, The Netherlands
²² Laboratoire de radioastronomie millimétrique, École Normale Supérieure and Observatoire de Paris, Paris, France
²³ Department of Astronomy, Beijing Normal University, Beijing, China
²⁴ Institut für Astrophysik der Leopold-Franzens, Universität Innsbruck, Austria
²⁵ UCLA, Los Angeles, CA, USA
²⁶ TIFR, Mumbai, India
²⁷ UFES, Vitoria, Brasil
²⁸ ESTEC, ESA, Noordwijk, The Netherlands
²⁹ Indian Institute of Astrophysics, Bangalore, India
³⁰ Observatoire de Besançon, France
³¹ Astrophysics Group, School of Chemistry & Physics, Keele University, UK
³² The Johns Hopkins University, Baltimore MD, USA 


Corresponding author: A. Omont, omont@iap.fr

Received: 19 August 2002
Accepted: 17 March 2003

Abstract

The ISOGAL project is an infrared survey of specific regions sampling the Galactic Plane selected to provide information on Galactic structure, stellar populations, stellar mass-loss and the recent star formation history of the inner disk and Bulge of the Galaxy. ISOGAL combines 7 and 15 μm ISOCAM observations – with a resolution of 6″ at worst – with DENIS IJK_s data to determine the nature of the sources and the interstellar extinction. We have observed about 16 square degrees with a sensitivity approaching 10–20 mJy, detecting ~10⁵ sources, mostly AGB stars, red giants and young stars. The main features of the ISOGAL survey and the observations are summarized in this paper, together with a brief discussion of data processing and quality. The primary ISOGAL products are described briefly (a full desciption is given in Schuller et al. 2003): viz. the images and the ISOGAL–DENIS five-wavelength point source catalogue. The main scientific results already derived or in progress are summarized. These include astrometrically calibrated 7 and 15 μm images, determining structures of resolved sources; identification and properties of interstellar dark clouds; quantification of the infrared extinction law and source dereddening; analysis of red giant and (especially) AGB stellar populations in the central Bulge, determining luminosity, presence of circumstellar dust and mass-loss rate, and source classification, supplemented in some cases by ISO/CVF spectroscopy; detection of young stellar objects of diverse types, especially in the inner Bulge with information about the present and recent star formation rate; identification of foreground sources with mid-IR excess. These results are the subject of about 25 refereed papers published or in preparation.