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Radial Velocities and <Emphasis Type= J. Astrophys. Astr. (1997) 18, 161–227 Radial Velocities and DDO, BV Photometry of Henry Draper G5 – M Stars near the North Galactic Pole K. M. YOSS, University of Illinois, Astronomy Department, Urbana-Champaign, Urbana, Illinois 61801, USA R. F. Griffin, The Observatories, Madingley Road, Cambridge CB3 OHA, England Received 1997 July 19; accepted 1997 October 24 Abstract. Radial velocities are given for some 900 stars within 15° of the North Galactic Pole, including almost all such stars classified G5 or later in the Henry Draper Catalogue. Luminosities, two-dimensional spectral classes, composition indices, and distances are derived for the majority of the sample through DDO and BV photometry. More than half of the stars are classified as G5 – K5 giants: they show a clear relationship between composition and velocity dispersion for the two Galactic components V and W, and a less well-defined trend for U. Four abun- dance groups exhibit characteristics which imply association with, respectively, the thick disk, old thin disk, young thin disk, and Roman's "4150" group. The sample is contained within l kpc of the Galactic plane, and no trends with distance are evident. Keywords. North Galactic Pole—radial velocities—BV and DDO photometry—space velocities—abundances—Galactic structure. 1. Introduction Interest in Galactic structure, particularly after the epic work of Eggen, Lynden-Bell & Sandage (1962), has prompted a vigorous effort to establish some of the principal parameters of our Galaxy, such as the number of discrete Galactic-model components and their scaling factors (or density normalization, the relative numbers of each component in the Galactic plane), and the run of abundance and velocity dispersion with z, the distance from the plane. The relationship between the kinematics and the chemical abundances of stars is central to establishing the reality of the various proposed components of the Galaxy: the "thin disk", the "thick disk", and the "halo", proposed by Gilmore and associates (Gilmore & Reid 1983), or the two-component model, advocated by Bahcall and coworkers (e.g. Bahcall & Soneira 1980). Alternatively, rather than distinct components, a continuum may exist (e.g. Norris 1986; Norris & Ryan 1991), in which the kinematic and abundance characteristics gradually change with formation time, possibly owing to an infall of protogalactic fragments into dynamical equilibrium (Searle & Zinn 1978). Chemical-abundance and velocity-dispersion gradients as functions of z require samples extending well into the halo region. In recent studies, Gilmore, Wyse & Jones 161 162 K. M. Yoss & R. F. Griffin (1995), Chen (1997), and Reid et al. (1997) found no gradient of abundance from 1 to 3 kpc, contrary, for example, to the results of Norris & Ryan (1991) and Morrison (1993). Excellent and comprehensive reviews of the status of Galactic research and results are found in Gilmore, Wyse & Kuijken (1989), Sandage (1989), and more recently in Majewski (1993a), as well as the seminar series edited by Majewski (1993b), especially his own section (Part I). In particular, a number of invited papers in the "Preston-Fest" conference (Morrison & Sarjedini 1996) gives up-to-date reviews of current ideas on Galactic Halo history and formation. The present study involves approximately 900 late-type stars (mean distance from the Galactic plane 244 pc), a sample which is large enough to establish a trend of chemical abundance with velocity dispersion. The sample includes stars with classical thick-disk properties, albeit in small numbers, as they pass through the vicinity of the plane. The emphasis here is to determine the runs of velocity disper- sion with abundance and with regard to the lag in the Galactic velocity component in the direction of Galactic rotation, to see how they relate to the thin and thick disks. The sample does not extend to sufficient distances to allow an extensive study of the gradients of velocity dispersion and abundance as functions of z. Our analysis involves utilization of proper motions and DDO-derived distances (through the DDO-derived Mv). In the cases of very distant stars, the resulting tangent- tial velocities often contain large errors, so we restrict our analysis to stars with DDO luminosity class II-III and fainter. We furthermore restrict the analysis to the spectral range G5 – K5 (the valid DDO range). Henceforth, we use the terms "giant" to mean G5 – K5 stars with luminosities II III, III, and III–IV, "subgiants" to mean luminosity IV, and "dwarfs" to mean G5 – KS stars with the fainter luminosity classes IV-V and V. Stars falling outside these limits nonetheless are listed in the appropriate tables. 2. The sample One of us (R.F.G.) embarked nearly 30 years ago on a project whose goal was to determine the radial velocities of all the stars that are listed in the Henry Draper Catalogue as being of type G5 or later and are within 15° of the North Galactic Pole. About 800 stars meet those two criteria; they were identified in the Catalogue within an area of sky that was only rather roughly bounded by the small circle of Galactic latitude corresponding to b = +75°, so the sample is not strictly confined within, nor quite complete for, the nominal area. About 100 non-HD stars were additionally observed, as described in the concluding paragraph of this section. Since they were not selected either for kinematic or for abundance reasons, and they generally fall within the spectral-type range of the HD stars, they do not bias the sample and have been retained in the discussion. The result is that the final sample includes 914 stars. The project was made possible by the development at Cambridge of the technique of measuring stellar radial velocities by spectroscopic cross-correlation (Griffin -1 1967), which for late-type stars offers accuracies better than 1 km s . Radial-velocity spectrometers operating on that principle subsequently proliferated, and several of them (enumerated below) have been used in this effort. Later, DDO and BV photometry were initiated by K.M.Y. at Mount Laguna Observatory. From the DDO photometry, mk class (designated by lower case to Henry Draper G5 – M Stars near the NGP 163 distinguish from that derived from spectrographic inspection), MV (DDO),and a composition index (designated [Fe/H] DDO) were derived, and with the aid of visual magnitude the z-distance was then calculated. The HD star numbers (Cannon & Pickering 1919, 1920) are given in Table 1, followed in many cases by additional identifications, e.g. number in the Bright Star Catalogue (BSC, Hoffleit 1982), constellation designation (Bayer 1603; Flamsteed 1725), number in Upgren's (1962) lists of Galactic-Pole stars or (Upgren 1960) M- type stars, numbers given by Trumpler (1938) to stars in the field of the Coma Cluster, Gliese (1969) numbers from the Catalogue of Nearby Stars, or numbers in the double-star catalogues BDS (Burnham 1906), ADS (Aitken 1932) or Cou (Couteau 1990). Those stars whose HD numbers are followed by asterisks are in the Supple- ment to the Bright Star Catalogue (Hoffleit, Saladyga & Wlasuk 1983). In quite a number of instances, stars that were seen in the same telescopic fields as the HD stars were also observed, with a view to assessing whether or not they are physically related to their respective HD 'primaries'. They have been designated in Table 1 and subsequently by the corresponding HD number suffixed by the letter B, or sometimes C. Such entries are, of course, not recognized HD designations. In most cases the stars concerned have already been identified in one or more of the catalogues and lists mentioned above, or in the BD (Argelander 1859, 1861) or the SAO (Smithsonian 1966). In cases where the subsidiary stars are not readily identified from existing publications, their approximate distances and position angles from their respective HD primaries are given; they are estimated, not astrometric, relative positions. Following the identifications are dates (to a hundredth of a day) of mid-observation, radial velocities in km s–1, and codes for the telescopes/spectrometers used. A colon after the velocity implies uncertainty, while brackets indicate rejection. A few comments at the end of the table are signified by the letters a–h following the associated velocities. 3. Radial velocities The radial velocities are from seven sources, all of which involve photoelectric radial- velocity spectrometers: these sources and pertinent information are listed in Table 2. Observations made at Cambridge, and elsewhere by R.F.G., were standardized either directly (series 1, 2, 4, 5) or indirectly (series 3, 6) against measurements of the primary reference star HD 113996 = 41 Com (Griffin 1967); it is a pure coincidence (P < 1/500) that the primary reference star, which was chosen years before the presently described project was conceived, is situated so conveniently close to the -1 Galactic Pole (b ∽ 86·5). The radial velocity of 41 Com is taken to be –14.7 km s (Griffin 1969). It has been found (e.g. Griffin & Herbig 1981) that such standardization tends to lead to velocities that are about 0.8 km s–1 more positive than ones that are tied to the IAU scale (Pearce 1957). Since, however, the IAU scale is itself not well defined and has for a long time been in course of revision (Batten 1985; Andersen 1988; IAU 1990, 1992; Stefanik & Scarfe 1994), we have seen fit to retain our own standardization. A zero-point adjustment of +1.8 km s–1 was applied to observations by K.M.Y. (series 7), which were initially standardized against a hollow-cathode lamp giving a spectrum of iron, to bring them into systematic agreement with the others. 164 K. M. Yoss & R. F. Griffin Table 1. Spectrometer Measurements of the Radial Velocities of North Galactic Pole G5-M Stars.
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