1995A&A...295..655N -
Astronomy and Astrophysics, volume 295, 655-677 (1995/3-3)
The Galactic structure towards the Galactic Centre. I. A study of the Palomar-Groningen Field 3.
NG Y.K., BERTELLI G., BRESSAN A., CHIOSI C. and LUB J.
Abstract (from CDS):
In this paper we address the analysis of the structure of the Galaxy towards the Centre. For this purpose we developed the so-called HRD-GST, the Hertzsprung-Russell Diagram Galactic Software Telescope, which simulates the stellar distribution in the line of sight. With the aid of the HRD-GST we analyze the stellar content in field #3 of the Palomar-Groningen Survey (PG3), located at the periphery of the Galactic Bulge. The observations are well described by a two component model with a disc and spheroid. There is no need to include a population from the so-called thick disc in the direction of field #3. The majority of the stars (BJ<18mag) in this field are located in the disc. The main stellar population is well described with the following structural parameters for the scale height and scale length: (z0=250pc; h0=4.5kpc) or (z0=230pc; h0=3.5kpc). For the metallicity and age we obtained: Z=0.008-0.015 and t=7.0-4.5Gyr for an exponentially decreasing star formation rate with a characteristic time scale equal to 2.5Gyr. At brighter magnitudes there is a significant contribution from a younger disc population. This population is described with the following structural and evolutionary parameters: (z0=100pc; h0=4.5kpc), Z=0.015-0.020, and t=5.0-2.0Gyr for a constant star formation rate. A peak at BJ=16.4mag and BJ-RF≃1.5mag in the Colour-Magnitude Diagram is identified with stars on the Horizontal Branch from a stellar population within the spheroid. Two stellar populations are the main contributors to the spheroidal component. The analysis is restricted to a maximum metallicity Z=0.020. For the older and metal poorer halo population we use a R1/4-law with flattening q=0.60, Z=0.0004-0.0050, and t=16-10Gyr for an exponentially increasing star formation rate with a characteristic time scale equal to 3.0Gyr. For the younger and metal richer bulge population we used a power-law with index n=4.0 and flattening q=0.8, Z=0.005-0.020, and t=10-5.0Gyr for an exponentially decreasing star formation rate with a characteristic time scale equal to 2.5Gyr.
Abstract Copyright:
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Journal keyword(s):
methods: data analysis, numerical - stars: general, HR Diagram, statistics - Galaxy: general, stellar content, structure
Errata:
erratum vol. 301, p. 318-319
Simbad objects:
2
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