Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Vertical distribution of Galactic disk stars. I. Kinematics and metallicity
Nearly 400 Tycho-2 stars have been observed in a 720 square degree fieldin the direction of the North Galactic Pole with the high resolutionechelle spectrograph ELODIE. Absolute magnitudes, effectivetemperatures, gravities and metallicities have been estimated, as wellas distances and 3D velocities. Most of these stars are clump giants andspan typical distances from 200 pc to 800 pc to the galactic mid-plane.This new sample, free of any kinematical and metallicity bias, is usedto investigate the vertical distribution of disk stars. The old thindisk and thick disk populations are deconvolved from thevelocity-metallicity distribution of the sample and their parameters aredetermined. The thick disk is found to have a moderate rotational lag of-51 +/- 5 km s-1 with respect to the Sun with velocityellipsoid (sigmaU , sigmaV , sigmaW )=(63+/- 6, 39+/- 4, 39+/- 4) km s-1, mean metallicity of[Fe/H] = -0.48 +/- 0.05 and a high local normalization of 15 +/- 7%.Combining this NGP sample with a local sample of giant stars from theHipparcos catalogue, the orientation of the velocity ellipsoid isinvestigated as a function of distance to the plane and metallicity. Wefind no vertex deviation for old stars, consistent with an axisymmetricGalaxy. Paper II is devoted to the dynamical analysis of the sample,puting new constraints on the vertical force perpendicular to thegalactic plane and on the total mass density in the galactic plane.Based on observations made at the Observatoire de Haute Provence(France). Data are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/141
| FAUST observations near the North Galactic Pole
We analyse a UV observation with FAUST in the direction of the NorthGalactic Pole. The region includes a cirrus cloud (G251.2+73.3) and adark globule, and the FAUST image contains 75 UV sources. We discuss theUV source detection and their identification with optical counterparts.We use, for the first time, low-resolution spectral information as theprimary means of identifying possible optical counterparts. This iscomplemented, and sometimes modified, by optical information availablefrom existing data bases. The results are interpreted with the help ofmaps of the distribution of far-infrared emission and of the neutralhydrogen gas. We discuss the types of objects found, the degree ofmatching with the predictions of our UV Galaxy model, and the generalbehaviour of the Galactic UV extinction in this Milky Way part. Wecompare the UV results for this region with similar observations in thesame neighbourhood, which are less affected by dust, and attempt toexplain the peculiar distribution of UV magnitudes as a result of apeculiar distribution of foreground dust, which does not follow theaccepted dust-to-gas relation.
| UBV photometry of stars whose positions are accurately known.
Photometric indices V, B-V, and U-B were measured for about 560 stars ofthe AGK3R and NPZT catalogs between BD declinations 11 deg and 23 deg,using the 40-cm Cassegrain telescope of the Kvistaberg Observatory fromApril 1986 to May 1987. The observation procedure and the reductiontechnique were the same as in the earlier papers of this series by Oja(1984, 1985, 1986, and 1987). The mean errors were calculated from theinternal consistency of the data. The accuracy was found to be the sameas for the earlier parts of the survey.
| Photoelectric photometry of stars near the north Galactic pole. II
UBV photometric observations of about 700 stars near the north Galacticpole, obtained using single-channel photometers on the 40-cm and 60-cmCassegrain telescopes at Kvistaberg Observatory (during 1976-1983) andthe Spanish International Observatory (during 1984), respectively, aspart of a program including the stars to be observed by the Hipparcosspacecraft, are reported. The data are presented in a series of tablesand briefly characterized.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Bereniké Haja |
| Rektaszcenzió: | 12h18m23.91s |
| Deklináció: | +19°08'51.2" |
| Vizuális fényesség: | 8.774 |
| Távolság: | 625 parszek |
| RA sajátmozgás: | 0.1 |
| Dec sajátmozgás: | -3.4 |
| B-T magnitude: | 9.992 |
| V-T magnitude: | 8.875 |
Katalógusok és elnevezések:
|
