H II regions as extragalactic distance indicators. IV - The Virgo cluster

1981 ◽  
Vol 247 ◽  
pp. 9 ◽  
Author(s):  
R. C., Jr. Kennicutt
Keyword(s):  
Virgo Cluster ◽  
H Ii Regions ◽  
Distance Indicators

scholarly journals Brightest Stars in Galaxies as Distance Indicators

1986 ◽  
Vol 116 ◽  
pp. 31-41 ◽  
Author(s):  
Allan Sandage
Keyword(s):  
Local Group ◽  
Hubble Constant ◽  
Absolute Magnitude ◽  
Virgo Cluster ◽  
Current Status ◽  
Type I ◽  
Red Supergiants ◽  
Absolute Magnitudes ◽  
Distance Indicators ◽  
Eddington Limit

The current status of the absolute magnitude calibration of the brightest blue and red supergiants in galaxies of different absolute magnitudes shows trends of M(star) with M(parent galaxy). Red supergiants show a more shallow correlation than the blue stars for galaxies brighter than MB = −14. For fainter galaxies, the red supergiant method appears to become totally degenerate.Four areas of application of the brightest star data are discussed as (1) determining MB of the Eddington limit to be ∼−10 for blue supergiants, (2) calibration of MB(max) = −20.0±0.4 for type I supernovae, leading to a Hubble constant of HO = 43±10 km s−1 Mpc−1, (3) detection of the deceleration of the cosmological expansion by the Local Group leading to a Local Group mass of 4×1011 M⊙ and a mass-to-blue light ratio of 3, and (4) use of the brightest stars to map the Virgo cluster velocity perturbation of the Hubble flow.

scholarly journals The Cosmic Distance Scale

1987 ◽  
Vol 124 ◽  
pp. 151-185 ◽  
Author(s):  
G.A. Tammann
Keyword(s):  
Selection Bias ◽  
Linear Expansion ◽  
Zero Point ◽  
Absolute Magnitude ◽  
Virgo Cluster ◽  
Distance Scale ◽  
Coma Cluster ◽  
Cluster Galaxies ◽  
True Value ◽  
Distance Indicators

The zero-point of the extragalactic distance scale, defined by about two dozens of nearby, late-type galaxies, has remained nearly unchanged for the last decade, in spite of the advent of new techniques and great efforts. The distances are essentially tied to trigonometric parallax stars and hence independent of the Hyades modulus; they are consistent with RR Lyr stars. The mean zero-point is therefore probably secure to better than 10%.All known secondary distance indicators are still affected by zero-point errors, by problems in the definition of their relation between distance indicator and absolute magnitude (or linear size), and/or by selection bias. The effect of the very important selection bias (Malmquist effect), which causes a seemingly non-linear expansion field, is illustrated by two examples. To test for any true deviations from a linear expansion the Hubble diagram of nearly bias-free first-ranked cluster galaxies and supernovae Ia is shown; this imposes stringent limits on any non-linearity of the Hubble flow within v<5000 km s−1.After freeing the available distances of field galaxies from selection bias and after reducing them to a common zero-point, one finds HO=55–65. Several distance indicators require a best Virgo cluster modulus of (m-M)=31.60, which implies for the Coma cluster (m-M)=35.38 and, with v(Coma)=7217 km s−1, HO=60. Supernovae Ia and first-ranked cluster galaxies out to large distances give HO (global)=53. Thus the evidence from clusters and field galaxies is best satisfied by HO=55; the assigned mean error of ±7 is to indicate a 3σ range of 35<HO<75.Purely physical methods to determine extragalactic distances have modest weight yet; they will contribute eventually much to the determination of HO.If HO were as large as 100, several paradoxa would arise. The Milky Way would have a very high supernova frequency, our Galaxy and M31 would be oversized, the baryon density would fall short to bind clusters, and Friedman universes were excluded.Because all systematic errors have conspired and probably still conspire to measure HO too high, the true value could well be 40. Until new, decisive evidence becomes available, it is suggested for all practical purposes to use HO=50.

Magellanic Cloud Eclipsing Binaries: Primary Distance Indicators

1999 ◽  
Vol 190 ◽  
pp. 563-566
Author(s):  
J. D. Pritchard ◽  
W. Tobin ◽  
J. V. Clausen ◽  
E. F. Guinan ◽  
E. L. Fitzpatrick ◽  
...  
Keyword(s):  
New Zealand ◽  
Magellanic Cloud ◽  
Eclipsing Binaries ◽  
Fundamental Parameters ◽  
Distance Indicators

Our collaboration involves groups in Denmark, the U.S.A. Spain and of course New Zealand. Combining ground-based and satellite (IUEandHST) observations we aim to determine accurate and precise stellar fundamental parameters for the components of Magellanic Cloud Eclipsing Binaries as well as the distances to these systems and hence the parent galaxies themselves. This poster presents our latest progress.

Malmquist Bias and the Distance to the Virgo Cluster

1997 ◽  
Vol 485 (1) ◽  
pp. 80-86 ◽  
Author(s):  
Anthony H. Gonzalez ◽  
S. M. Faber
Keyword(s):  
Virgo Cluster
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