scholarly journals The Space Density of M Dwarfs - An Observational Program

1977 ◽  
Vol 4 (2) ◽  
pp. 29-30
Author(s):  
Peter Pesch
Keyword(s):  
Proper Motion ◽  
Wavelength Region ◽  
Schmidt Telescope ◽  
M Dwarfs ◽  
Dwarf Stars ◽  
Space Density ◽  
The North ◽  
Cool Stars ◽  
Objective Prism ◽  
North Galactic

In spite of extensive proper motion surveys, there remains some uncertainty about the space density and the kinematics of late-type dwarf stars. This uncertainty is primarily due to the unknown kinematic bias introduced by the proper motion discovery technique.A spectrographic search, especially one using an objective prism on a Schmidt telescope, can identify significant numbers of intrinsically (and actually) faint stars, free from any kinematic bias. To find faint and cool stars, one chooses an objective prism with low dispersion and emulsions sensitive to the red and near photographic infrared. At low dispersions, in this wavelength region, there are no reliable luminosity criteria. Thus Sanduleak conducted his survey in the direction of the north galactic pole, with the expectation that very few remote giants would contaminate his results. A catalog of 273 probable dwarf stars of type M3 and later (Sanduleak, N. 1976, A.J., 81, 350) based on his objective prism survey in the direction of the north galactic pole is now available. Thanks to W.J. Luyten (1976, Proper Motion Survey with the Forty-Eight Inch Schmidt Telescope XLVI (Univ. Minnesota, Minneapolis)) proper motions have been measured for all of these stars.

scholarly journals The Space Density of Faint M-Dwarfs

1974 ◽  
Vol 3 ◽  
pp. 417-418
Author(s):  
J. H. Oort
Keyword(s):  
Coming Out ◽  
Mass Density ◽  
M Dwarfs ◽  
Space Density ◽  
Gas Density ◽  
The North ◽  
Solar Motion ◽  
Objective Prism ◽  
High Space ◽  
North Galactic

Donna Weistrop, a student of Maarten Schmidt’s, has found evidence for an unexpectedly high space density of very faint M-dwarfs. This was confirmed by Murray and Sanduleak. The space density inferred from these investigations is comparable to, or possibly higher than, the local gas density. Because there is evidence that the stars concerned are young this appears to present a problem.As the investigation by Murray and Sanduleak is the simpler and more direct of the two I confine my discussion to this. The authors determined proper motions for 21 M dwarfs down to 17m found in an objective-prism survey at the Warner and Swasey Observatory in regions close to the North Galactic Pole. The distance of the stars can be inferred from the reflection of the solar motion. Assuming the ‘basic’ solar motion they found and a space density of 0.23 pc-3 for these stars, corresponding with a mass density of about 0.04 M⊚ pc-3. This is exceedingly high, in view of the fact that the average gas density near z = 0 is only 0.03 M⊚ pc-3. The problem is aggravated by the fact that the stars have low velocities, the dispersion in velocity in one coordinate coming out ± 10kms-1. This is considerably lower than the velocity dispersion of A-type stars, and shows that the stars are young, perhaps about 108 yr. How is it then that the gas has not been completely used up long ago?

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.

Double Stars with Common Proper Motion

1965 ◽  
Vol 5 ◽  
pp. 49-51
Author(s):  
Willem J. Luyten
Keyword(s):  
Proper Motion ◽  
Galactic Latitude ◽  
Schmidt Telescope ◽  
Polar Cap ◽  
Double Stars ◽  
The North ◽  
North Polar

The proper Motion Survey with the 48-in Schmidt telescope has now progressed far enough such that we may begin to make some meaningful statistical discussions of the results obtained. Altogether 135 regions have been blinked – one seventh of the total -and in particular all fifty plates covering the area of the North Polar Cap, north of declination +69 (1855) have been blinked and completely measured. This area covers 1360 square degrees, almost exactly one thirtieth of the entire sphere, and, since the galactic latitude of the Pole is 27°, and its distance from the ‘average’ solar apex is about 55° this region may be considered as not too unrepresentative for the whole sky.

scholarly journals Stellar Kinematics in the Galactic North Pole Region on the Basis of Tautenburg Schmidt Telescope Plates

1994 ◽  
Vol 161 ◽  
pp. 444-446
Author(s):  
N.V. Kharchenko ◽  
E. Schilbach ◽  
R.-D. Scholz
Keyword(s):  
Spatial Distribution ◽  
Galactic Plane ◽  
North Pole ◽  
Proper Motions ◽  
Stellar Kinematics ◽  
Schmidt Telescope ◽  
The North ◽  
Spatial Velocity ◽  
North Galactic

The spatial velocity components and their dispersions in the Galactocentric and rotation directions, eccentricities of Galactic orbits, parameters of spatial distribution and the change of all these characteristics with distance from the Galactic plane are detennined. These data have been obtained on the basis of absolute proper motions and stellar B, V magnitudes in two sky regions near the North Galactic Pole (NGP) by means of a plate set of the Tautenburg Schmidt telescope.

scholarly journals Kiss: A New Digital Survey for Emission-Line Objects

1998 ◽  
Vol 179 ◽  
pp. 302-304 ◽  
Author(s):  
A. Kniazev ◽  
J. Salzer ◽  
V. Lipovetsky ◽  
T. Boroson ◽  
J. Moody ◽  
...  
Keyword(s):  
Emission Line ◽  
Rest Frame ◽  
Pilot Project ◽  
The North ◽  
Ccd Detector ◽  
Redshift Survey ◽  
Objective Prism ◽  
Emission Line Galaxies ◽  
Digital Survey ◽  
North Galactic

We have initiated a major new survey for emission-line galaxies (ELGs) which we call the KPNO International Spectroscopic Survey (KISS). Survey observations began in March 1994 with the 0.61-m Burrell Schmidt telescope. The technique we employ combines the benefits of a traditional photographic objective-prism survey with the advantages of using a CCD detector. The field of view of our CCD is 1.1° square, and the prism employed provides a dispersion of 19 Å/pixel at 5000 Å. The spectral range covered (4800-5500 Å) is restricted by a specially designed filter that transmits from rest-frame Hβ to just shortward of the strong night-sky line at 5577 Å; this greatly reduces the sky background. We expect KISS to be sensitive to galaxies with magnitudes as faint as B = 20m–21m, much deeper than existing photographic surveys. Our initial pilot project covers 100 square degrees (Salzer et al. 1994) and overlaps the CfA/Dartmouth Century Redshift Survey (α = 8h30m–16h45m and δ = 29°–30°) in the North Galactic cap.

A search for early-G dwarf stars towards the north Galactic pole

1988 ◽  
Vol 95 ◽  
pp. 745 ◽  
Author(s):  
Christopher J. Corbally ◽  
Robert F. Garrison
Keyword(s):  
Dwarf Stars ◽  
The North ◽  
North Galactic
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