# Composition of the galactic center star cluster: Population analysis from adaptive optics narrow band spectral energy distributions - Astrophysics > Astrophysics of Galaxies

Composition of the galactic center star cluster: Population analysis from adaptive optics narrow band spectral energy distributions - Astrophysics > Astrophysics of Galaxies - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: The goals of this work are to develop a new method to separate early and latetype stellar components of a dense stellar cluster based on narrow bandfilters, to apply it to the central parsec of the GC, and to conduct apopulation analysis of this area. We use AO assisted observations obtained atthe ESO VLT in the NIR H-band and 7 intermediate bands covering the NIR K-band.A comparison of the resulting SEDs with a blackbody of variable extinction thenallows us to determine the presence and strength of a CO absorption feature todistinguish between early and late type stars. The new method is suitable toclassify K giants and later as well as B2 main sequence and earlier starswhich are brighter than 15.5 mag in the K band in the central parsec. Comparedto previous spectroscopic investigations that are limited to 13-14 mag, thisrepresents a major improvement in the depth of the observations as well asreducing the needed observation time. We classify 312 stars as early typecandidates out of a sample of 5914 sources. The distribution of the early typestars can be fitted with a steep power law betaR>1- = -1.49 +- 0.12,alternatively with a broken power law, betaR=1-10- = -1.08 +- 0.12,betaR=10-20- = -3.46 +- 0.58, since we find a drop of the early typedensity at ~10-. We also detect early type candidates outside of 0.5 pc insignificant numbers for the first time. The late type density function shows aninversion in the inner 6-, with a power law slope of betaR<6- = 0.17 +-0.09. The late type KLF has a power law slope of 0.30$\pm$0.01, closelyresembling the KLF obtained for the bulge of the Milky Way. The early type KLFhas a much flatter slope of 0.14 +- 0.02. Our results agree best with anin-situ star formation scenario.

Autor: Rainer M. Buchholz, Rainer Schödel, Andreas Eckart

Fuente: https://arxiv.org/