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Astron. Astrophys. 348, 768-782 (1999)

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7. Conclusions

For an area [FORMULA] centered approximately on Sgr A* and referred to as "mosaic" we have determined its KLF containing [FORMULA] sources with reddened K band flux densities [FORMULA]Jy. The completeness limit of this KLF lies in the range [FORMULA]Jy. Half of the K band surface brightness integrated over the mosaic comes from an unresolved continuum formed by an estimated number of [FORMULA] low and medium mass ([FORMULA]) MS stars. For [FORMULA]Jy (O9 stars and later) the characteristics of the observed KLF and the unresolved continuum are well represented by a model KLF combined with the observed and extrapolated KLF. The model KLF is based on a Salpeter IMF and a total stellar mass contained within [FORMULA] pc of [FORMULA]. The combined KLF increases [FORMULA] for [FORMULA]Jy and [FORMULA] for [FORMULA]Jy. The flattening and turnover of the KLF observed in the central parts of the Nuclear Bulge appears to be an artifact caused by incompleteness of the source counts.

From the observation we constructed difference KLFs which make it possible to obtain KLFs for different spatial sections along the line of sight. This allowed us to isolate the mosaic KLF related to the stellar population of the Nuclear Bulge (see Fig. 4b and Table 3) and to confirm quantitatively the results by Glass et al. (1987), Catchpole et al. (1990), Blum et al. (1996a) and Narayanan et al. (1996) that this stellar population has an excess of bright stars compared to the stellar population of the Galactic Bulge ([FORMULA]kpc[FORMULA]) and the interarm region of the Galactic Disk ([FORMULA] kpc).

Blum et al. (1996b), based on stellar NIR spectroscopy, conclude that most of the bright, cool stars in the Nuclear Bulge are intermediate mass/age AGB stars. Our results support these findings. O9 - O3 stars contribute only [FORMULA], Giants [FORMULA] to the integrated K band flux density. Some of the most luminous K band stars could be Wolf-Rayet stars and Supergiants.

In agreement with Genzel et al. (1996) we find a deficiency of low-mass low-luminosity stars in the central [FORMULA]. Fitting King profiles to the observed surface brightnesses we obtain core radii of [FORMULA] and [FORMULA], respectively, for resolved and unresolved stars.

We use the integrated radio/IR spectrum to determine dust- and Lyc-photon luminosities for the central [FORMULA] ([FORMULA] 1.25 pc). A warm component ([FORMULA] 150 K) dominates the dust emission. The luminosity of the cool stellar component ([FORMULA] K) is not sufficient to provide the heating which appears to be due to [FORMULA] 24 hot ([FORMULA] K) and luminous ([FORMULA]) stars, which also are responsible for the ionization of the gas in the Central Cavity.

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© European Southern Observatory (ESO) 1999

Online publication: August 13, 199
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