Studies of A and F stars in the region of the North Galactic Pole

The approach by Bahcall and Soneira to the determination of galactic parameters through the use of star counts is referred to, and tests of the Bahcall-Soneira Galaxy model based on additional observational data are discussed.The determination of the local mass density by Hill, Hilditch and Barnes through studies of A and F stars in the region of the North Galactic Pole is briefly discussed, as is a recent investigation of the problem by Bahcall.In the determination of the galactic force Kz and the local mass density from the density distribution ν(z) and the distribution f(W) of velocities at right angles to the galactic plane for a group of tracer stars, it is important to secure homogeneity of the tracer group. This has led Hill, Hilditch and Barnes in a continuation of their investigation to use photoelectric uvby photometry to segregate homogeneous groups of F stars. A similar approach is followed by Danish astronomers, whose work is briefly described.

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Studies of A and F stars in the region of the North Galactic Pole - IV. A determination of the local mass density

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/186.4.813 ◽

1979 ◽

Vol 186 (4) ◽

pp. 813-829 ◽

Cited By ~ 35

Author(s):

G. Hill ◽

R. W. Hilditch ◽

J. V. Barnes

Keyword(s):

Mass Density ◽

Local Mass ◽

The North ◽

F Stars ◽

North Galactic

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Kinematics and properties of F stars near the North Galactic Pole - II. The isothermal disc

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/230.2.273 ◽

1988 ◽

Vol 230 (2) ◽

pp. 273-320 ◽

Cited By ~ 3

Author(s):

A. J. Adamson ◽

G. Hill ◽

W. Fisher ◽

R. W. Hilditch ◽

C. D. Sinclair

Keyword(s):

The North ◽

F Stars ◽

North Galactic

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Studies of a and F Stars in the Region of the North Galactic Pole

Highlights of Astronomy ◽

10.1017/s1539299600003087 ◽

1977 ◽

Vol 4 (2) ◽

pp. 71-71

Author(s):

R. W. Hilditch ◽

Graham Hill

Keyword(s):

Total Mass ◽

Mass Density ◽

Coma Cluster ◽

Broad Distribution ◽

Short Account ◽

Component Distribution ◽

Narrow Component ◽

The North ◽

F Stars ◽

North Galactic

A short account was given of results recently published (Hill et al. 1976; Hilditch et al. 1976a, b) of a spectroscopic and photometric study of 310 A0-F8 stars within 15° of the north galactic pole. Using these data, it has been found that δmo for the programme stars is constant out to 250 pc and corresponds, via Crawford’s (1975) calibration, to the solar value of [Fe/H]. The distribution of radial velocities of A0-F8 stars is asymmetric and may be interpreted as showing a broad distribution of mean −7 kms−1 and dispersion σ ~ 11 kms−1 together with a superposed narrow distribution of mean 0 kms-1 and dispersion σ ~ 3 kms-1. The narrow component originates from a group of 37 stars which appear to be kinematically and spatially associated with the Coma cluster. Only 14 of these 37 stars are recognised members of the Coma cluster. Removal of these 37 stars from the sample results in a distribution which matches closely the W component distribution of A0-F8 stars in Gliese’s (1969) catalogue. Thus Oort’s “well-mixed” hypothesis seems to be confirmed out to 250 pc. Much additional work on the space motions is required before the hypothesis of the ‘Coma group’ can be thoroughly tested. Results of this analysis and a preliminary value for the total mass density in the solar neighbourhood is expected to be completed during the next few months.

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