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Issue A&A
Volume 400, Number 3, March IV 2003
Page(s) 903 - 915
Section Stellar clusters and associations
DOI 10.1051/0004-6361:20030004



A&A 400, 903-915 (2003)
DOI: 10.1051/0004-6361:20030004

The ISOGAL field FC-01863+00035: Mid-IR interstellar extinction and stellar populations

B. W. Jiang1, 2, 3, A. Omont2, S. Ganesh2, 4, G. Simon5 and F. Schuller2

1  Department of Astronomy, Beijing Normal University, Beijing 100875, PR China
2  Institut d'Astrophysique de Paris, CNRS, 98 bis Bd Arago, 75014 Paris, France
3  National Astronomical Observatories, Chinese Academy of Sciences, Datun Rd. No.20(A), Beijing 100012, PR China (on leave)
4  Physical Research Laboratory, Navarangpura, Ahmedabad 380009, India
5  GEPI, Observatoire de Paris, 21 avenue de l'Observatoire, 75014 Paris, France

(Received 18 July 2002 / Accepted 23 December 2002 )

Abstract
A 0.35° $\times$ 0.29°field centered at l=-18.63°, b=0.35° was observed during the ISOGAL survey by ISOCAM imaging at 7  $\mu$m and 15  $\mu$m. 648 objects were detected and their brightness are measured.

By combining with the DENIS data in the near-infrared J and $K_{\rm S}$ bands, one derives the extinction at 7  $\mu$m through ${A_{K_{\rm S}}-A_7 = 0.35 (A_J-A_{K_{\rm S}})}$ which yields $A_\sim 0.03$ from the near-IR extinction values of van de Hulst-Glass (Glass 1999). The extinction structure along the line of sight is then determined from the values of $J{-}K_{\rm S}$ or $K_{\rm S}$-[7] of the ISOGAL sources identified as RGB or early AGB stars with mild mass-loss. The distribution of AV ranges from 0 to ~45 and it reflects the concentration of the extinction in the spiral arms. Based on their locations in color-magnitude diagrams and a few cross-identifications with IRAS and MSX sources, the nature of objects is discussed in comparison with the case of a low extinction field in Baade's Window. Most of the objects are either AGB stars with moderate mass loss rate or luminous RGB stars. Some of them may be AGB stars with high mass loss rate. In addition, a few young stellar objects (YSOs) are present.


Key words: stars: AGB and post-AGB -- stars: late-type -- stars: mass loss -- stars: pre-main sequence -- ISM: dust, extinction  -- Galaxy: stellar content -- Infrared: stars

Offprint request: B. W. Jiang, bjiang@bnu.edu.cn

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