# COMMUNICATIONS / MITTEILUNGEN

## A. Frontó ,
L.G. Balázs, M. Paparó

## Distribution of Late-type Stars around IC 4665

No. 95 (Vol. 11, Part 2)
Budapest, 1990

## Abstract

We have investigated 424 stars of F8 spectral types and later in a 19.5
sq. degree field around IC 4665. The main purpose of our study in this low
latitude field (b = +16.5 in our case) was the testing of the plane-parallel
hypothesis of the density distribution, i.e. the hypothesis that the spatial
density of the Population I stars observed at great angular distance from
the galactic caps is well approximated by the z = r sin (b) scaling of
the distributions obtained in the polar regions.
We used the factor analysis of multivariate mathematical statistics in
order to extract the effect of absorption from the photometric data. To
identify the factor component describing the interstellar reddening we
invoked the corresponding IRAS Sky Flux Data. We computed the spatial
densities for the F8 - G5 dwarfs and the K giants separately. We used a
maximum likelihood algorithm for oblating the space densities. We arrived
at the following main conclusions in our paper: The absorbing material
concentrates closer than 150 pc in our area. There is a weak but still
significant correlation between the optical measures of absorption and the
IRAS 100 micron Sky Flux Maps data. The spatial densities of F8 - G5
dwarfs essentially reflect the densities obtained in the galactic plane.
The distribution of distance moduli of K giants in our sample can be well
modelled by the z = sin (b) scaling of Upgren's data from the North Polar
region. The actual form of the space density curve of the K giants
can be satisfactorily fitted both by an isothermal model and an
exponential model.

Key words: late-type stars - galactic structure - multicolour photometry
- interstellar matter

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