Interstellar Reddening in the North Galactic Polar Cap I. The Dependence on Distance from the Galactic Plane

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.

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Detection of New Planetary Nebulae by IPHAS, the Hα Survey of the North Galactic Plane

10.1063/1.2146213 ◽

2005 ◽

Author(s):

R. L. M. Corradi

Keyword(s):

Galactic Plane ◽

Planetary Nebulae ◽

The North ◽

North Galactic

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

Highlights of Astronomy ◽

10.1017/s1539299600002926 ◽

1977 ◽

Vol 4 (2) ◽

pp. 31-31 ◽

Cited By ~ 2

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.

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900047811 ◽

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.

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The Gravitational Field of the Galaxy in the Z Direction

Highlights of Astronomy ◽

10.1017/s1539299600003051 ◽

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.

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Star counts, local density and KZ force

Symposium - International Astronomical Union ◽

10.1017/s0074180900242289 ◽

1985 ◽

Vol 106 ◽

pp. 153-160

Author(s):

Bengt Strömgren

Keyword(s):

Galactic Plane ◽

Local Density ◽

Mass Density ◽

Homogeneous Groups ◽

Local Mass ◽

The North ◽

Galaxy Model ◽

F Stars ◽

North Galactic

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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RR Lyrae-Type Stars in the Sonneberg Fields in the Vicinity of the North Galactic Pole

Astronomische Nachrichten ◽

10.1002/asna.19772980308 ◽

1977 ◽

Vol 298 (3) ◽

pp. 171-177 ◽

Cited By ~ 6

Author(s):

I. Meinunger

Keyword(s):

The North ◽

Rr Lyrae ◽

North Galactic

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Kinematics and stellar content of the Milky Way populations toward the North Galactic Pole

Astronomy and Astrophysics ◽

10.1051/0004-6361:20054712 ◽

2006 ◽

Vol 451 (1) ◽

pp. 125-139 ◽

Cited By ~ 39

Author(s):

A. Vallenari ◽

S. Pasetto ◽

G. Bertelli ◽

C. Chiosi ◽

A. Spagna ◽

...

Keyword(s):

Milky Way ◽

Stellar Content ◽

The North ◽

North Galactic

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Avalanches of the martian north polar cap

10.5194/egusphere-egu2020-22331 ◽

2020 ◽

Author(s):

Patricio Becerra ◽

Susan Conway ◽

Nicholas Thomas ◽

Keyword(s):

Polar Regions ◽

Martian Surface ◽

Polar Cap ◽

Water Ice ◽

The North ◽

Imaging Science ◽

Resolution Imaging ◽

North Polar ◽

Gas Expansion ◽

Trigger Mechanisms

In 2008, the High Resolution Imaging Science Experiment (HiRISE) on board NASA&#8217;s MRO fortuitously captured several discrete clouds of material in the process of cascading down a steep scarp of the water-ice-rich north polar layered deposits (NPLD). The events were only seen during a period of ~4 weeks, near the onset of martian northern spring in 2008, when the seasonal cover of CO2 is beginning to sublimate from the north polar regions. Russell et al. [1] analyzed the morphology of the clouds, inferring that the particles involved were mechanically analogous to terrestrial &#8220;dry, loose snow or dust&#8221;, so that the events were similar to terrestrial &#8220;powder avalanches&#8221; [2]. HiRISE confirmed the seasonality of avalanche occurrence the following spring, and continued to capture between 30 and 50 avalanches per season (fig. 1b,c) between 2008 and 2019, for a total of 7 Mars Years (MY29&#8211;MY35) of continuous scarp monitoring.In this work we will present statistics on these events, in an attempt to quantify their effect on the mass balance of the NPLD, and with respect to competing processes such as viscous deformation and stress-induced block falls that do not trigger avalanches [3,4]. We also use a 1D thermal model [5] to investigate the sources and trigger mechanisms of these events. The model tracks the accumulation and ablation of seasonal CO2 frost on a martian surface. Russell et al. [1] support an initiation through gas-expansion related to the presence of CO2 frost on the scarp. Therefore the amount of frost that lingers on different sections of the model scarp at the observed time of the avalanches will provide evidence either for or against this particular mechanism. We will present preliminary results and discuss their implications.References: [1] P. Russell et al. (2008) Geophys. Res. Lett. 35, L23204. [2] D. McClung, P.A. Schaerer (2006), Mountaineers, Seattle Wash. [3] Sori, M. M., et al., Geophys. Res. Lett., 43. [4] Byrne et al. (2016), 6th Int. Conf. Mars Polar Sci. Exploration [4] C. M. Dundas and S. Byrne (2010) Icarus 206, 716.

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