scholarly journals The Gravitational Field of the Galaxy in the Z Direction

1977 ◽  
Vol 4 (2) ◽  
pp. 65-66
Author(s):  
R. F. Griffin
Keyword(s):  
Galactic Plane ◽  
Narrow Band ◽  
Radial Velocities ◽  
Photoelectric Photometry ◽  
Giant Stars ◽  
The North ◽  
The Galaxy ◽  
Absolute Magnitudes ◽  
North Galactic ◽  
K Giants

This is a progress report of a project designed to find the component, perpendicular to the Galactic plane, of the gravitational potential of the Galaxy. The principle is to measure the radial velocities and distances of a large number of K-giant stars near the North Galactic Pole. My student G. A. Radford is masterminding the project; collaborating with us are Drs. J. E. Gunn of the Hale Observatories and L. Hansen and K. Gyldenkerne of Copenhagen.We have measured the radial velocities of all the HD stars of type KO and later, and many of the G5 stars, within 15°of the Galactic Pole, using the Cambridge photoelectric spectrometer. In addition, we have observed all the stars classified as K giants by Upgren in his declination zones 25° to 31°, using the spectrometer on the Hale telescope. There are about 900 stars observed altogether, including about 200 Upgren stars, running down to twelfth magnitude or so, which are not in the Henry Draper Catalogue. To determine the distances of all these stars we are now trying to determine the absolute magnitudes by narrow-band photoelectric photometry in the Copenhagen system. Most of the observations have been made, thanks largely to the very generous grants of observing time given by the Hale Observatories earlier this year; but the reductions have only been completed for about 300 stars (including 244 K giants) which were observed last year at Kitt Peak, and the present, very preliminary, discussion is based on those stars alone.

scholarly journals The Frequency of Faint M Giant Stars at High Galactic Latitudes

1977 ◽  
Vol 4 (2) ◽  
pp. 35-36 ◽  
Author(s):  
N. Sanduleak
Keyword(s):  
Main Sequence ◽  
Galactic Plane ◽  
Absolute Magnitude ◽  
Main Sequence Stars ◽  
Giant Stars ◽  
The North ◽  
Objective Prism ◽  
M Stars ◽  
Low Dispersion ◽  
North Galactic

Based on the observations of M giant stars in the north galactic polar objective-prism survey of Upgren (1960) and the data summarized by Blanco (1965) the overall space density of all M-type giants as a function of distance from the galactic plane at the position of the sun can be approximated by,where z is in kpc and ρ(z) is the number of stars per 106 pc3. This relationship is derived from the observed fall-off in space densities up to a distance of about 2 kpc.The question arises as to the validity of extrapolation equation (1) to larger z distances so as to predict the number of faint M giants expected per unit area near the galactic poles. Adopting for the M giants a mean visual absolute magnitude of −1.0 (Blanco 1965), one finds that equation (1) predicts that less than one giant fainter than V~12 should be expected in a region of 200 square degrees. This expectation formed the hypothesis of a thesis study (Sanduleak 1965) in which it was assumed that the very faint M stars detected in a deep, infrared objective-prism survey at the NGP were main-sequence stars, since this could not be ascertained spectroscopically on the very low-dispersion plates used.

scholarly journals The Luminosity Function of Late-Type Main-Sequence Stars in the Direction of the North Galactic Cap

1977 ◽  
Vol 4 (2) ◽  
pp. 31-31 ◽  
Author(s):  
Donna Weistrop
Keyword(s):  
Luminosity Function ◽  
Main Sequence ◽  
Galactic Plane ◽  
Absolute Magnitude ◽  
Apparent Magnitude ◽  
Late Type ◽  
Main Sequence Stars ◽  
Photoelectric Photometry ◽  
The North ◽  
North Galactic

As a result of the recent discussion concerning the luminosity function of late-type main-sequence stars (Weistrop 1976 and references therein), a program of photoelectric photometry of all red stars in a field near the North Galactic Pole was undertaken. The sample is complete for stars redder than (B - V) = 1.40 magnitude for the following apparent magnitude and area limits: V = 12.0-14.0 magnitudes, 13.5 square degrees; V = 14.0-15.0 magnitudes, 3.0 square degrees; V = 15.0-17.5 magnitudes, 1.0 square degree. Observations in BVRI have been obtained for the 44 stars in the sample. Giants and dwarfs are distinguished by their location in the (B - V)-(V - I) diagram or from published proper motion data, where available. The absolute magnitudes of the dwarfs are determined from the MR - (R - I) relation.The density distribution perpendicular to the galactic plane of the dwarfs is consistent with the distribution for K giants found by Oort (1960). The derived luminosity function does not differ significantly from that determined by Wielen (1974) for stars close to the Sun. The local space density for stars in the interval MV = 8.5-14.0 magnitudes is 0.099 stars pc−3. The corresponding stellar density derived from Wielen’s luminosity function is >0.066 stars pc−3. Sixty-six percent of the density derived here is contributed by two stars with absolute magnitude in the range MV = 13.0−14.0 magnitudes.

scholarly journals An Hα Survey of the Galactic Plane

1998 ◽  
Vol 179 ◽  
pp. 179-181
Author(s):  
Q.A. Parker ◽  
S. Phillipps
Keyword(s):  
Galactic Plane ◽  
Narrow Band ◽  
Interference Filter ◽  
Low Noise ◽  
Magellanic Clouds ◽  
Coverage Depth ◽  
Ionized Gas ◽  
Fine Grain ◽  
The Galaxy ◽  
Very High

We describe a major new Anglo-Australian proposal for a U.K. Schmidt Telescope (UKST) Hα survey of the Southern Galactic plane, Magellanic clouds and selected regions. The agreed survey will use a new 12 × 12 inch monolithic Hα interference filter of very high specification in combination with Tech Pan film. Tech Pan offers significant advantages for this work due to an inherent sensitivity at Hα and its extremely fine grain, high resolution, exceptional DQE, excellent imaging and low noise (e.g., Parker et al. 1994). The combination of Tech Pan and a narrow band Hα filter will provide a survey of unprecendented area coverage, depth and resolution, superior to any previous optical survey of ionized gas in the galaxy. It should to lead to exciting new discoveries and avenues of research.

Radial velocities for interesting G-type stars at the North Galactic Pole

1987 ◽  
Vol 93 ◽  
pp. 1439 ◽  
Author(s):  
Peter B. Stetson ◽  
Christopher L. Aikman
Keyword(s):  
Radial Velocities ◽  
The North ◽  
North Galactic

scholarly journals A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

2019 ◽  
Vol 623 ◽  
pp. A52 ◽  
Author(s):  
A. Boselli ◽  
M. Fossati ◽  
A. Longobardi ◽  
G. Consolandi ◽  
P. Amram ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Narrow Band ◽  
Elliptical Galaxy ◽  
Virgo Cluster ◽  
Environmental Survey ◽  
Narrow Band Image ◽  
The North ◽  
Optical Images ◽  
The Galaxy ◽  
North Western

We observed the giant elliptical galaxy M 87 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Hα+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada French Hawaii Telescope (CFHT). The deep narrow-band image confirmed the presence of a filament of ionised gas extending up to ≃3 kpc in the north-western direction and ≃8 kpc to the southeast, with a couple of plumes of ionised gas, the weakest of which, at ≃18 kpc from the nucleus, was previously unknown. The analysis of deep optical images taken from the NGVS survey confirms that this gas filament is associated with dust seen in absorption which is now detected up to ≃2.4 kpc from the nucleus. We also analysed the physical and kinematical properties of the ionised gas filament using deep IFU MUSE data covering the central 4.8 × 4.8 kpc2 of the galaxy. The spectroscopic data confirm a perturbed kinematics of the ionised gas, with differences in velocity of ≃700–800 km s−1 on scales of ≲1 kpc. The analysis of 2D diagnostic diagrams and the observed relationship between the shock-sensitive [OI]/Hα line ratio and the velocity dispersion of the gas suggest that the gas is shock-ionised.

Radial velocities of 40 F5-K stars near the North Galactic Pole

1993 ◽  
Vol 2 (2) ◽  
Author(s):  
S. Bartašiūtė ◽  
Yu. V. Kulagin ◽  
N. N. Samus
Keyword(s):  
Radial Velocities ◽  
The North ◽  
North Galactic

scholarly journals Deep Multi-Colour Starcounts

1994 ◽  
Vol 161 ◽  
pp. 423-424
Author(s):  
I.N. Reid ◽  
S.R. Majewski
Keyword(s):  
Standard Model ◽  
Stellar Population ◽  
Stellar Populations ◽  
The North ◽  
Halo Stars ◽  
The Standard Model ◽  
The Galaxy ◽  
Best Fitting ◽  
Galactic Stellar Populations ◽  
North Galactic

Starcounts remain one of the most effective methods of probing the structure of the Galactic stellar populations. However, studies of the distribution at large distances above the Plane demand accurate photometry extending to faint magnitudes (V > 20), and such datasets are still rare. We (Reid & Majewski 1993) have analyzed data from one field — Majewski's (1992) UJF observations of SA57, the North Galactic Pole field. Our results revealed significant discrepancies with the standard model of the Galaxy (see refs. in Reid & Majewski), notably a paucity in the number of halo stars by a factor of two and the presence of a factor of two more disk stars than predicted — sufficient stars that the disk is the majority stellar population, outnumbering halo stars 2:1 even at V = 21. Majewski et al. (1993) has obtained UJFN photographic data for several other fields, and Fig. 1 shows a preliminary comparison of these observations with the predictions of the best-fitting SA57 model. Given that none of the parameters have been modified, the agreement is surprisingly good.

scholarly journals The Absolute Luminosity of RR Lyrae Variables

1988 ◽  
Vol 126 ◽  
pp. 587-588
Author(s):  
C. Cacciari ◽  
G. Clementini ◽  
L. Prevot
Keyword(s):  
Surface Brightness ◽  
Radial Velocities ◽  
Photoelectric Photometry ◽  
Rr Lyrae ◽  
Metal Abundance ◽  
Metal Abundances ◽  
Complete Set ◽  
Effective Temperatures ◽  
Absolute Magnitudes ◽  
Absolute Luminosity

We have taken UBVRI photoelectric photometry and CORAVEL radial velocities for 6 field RR Lyraes, i.e. SW And, YZ Cap, SW Dra, SS For, RV Phe and V440 Sgr, with the purpose of applying the Baade-Wesselink (B-W) method and determining their absolute magnitudes. The present improvements with respect to previous applications of the method are: a) the use of the (V-I) color, which shows the smallest sensitivity to gravity and metal abundance in the color-visual surface brightness plane. b) the use of a new grid of model atmospheres by Buser and Kurucz (1986), which include an improved treatment of opacity and convection. They provide a complete set of models for the relevant values of effective temperatures, gravities and metal abundances, thus avoiding the need of inaccurate interpolations or extrapolations.

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