Mathematics – Logic
Scientific paper
May 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983apj...268..451d&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 268, May 15, 1983, p. 451-475.
Mathematics
Logic
46
Calibrating, Cosmology, Distance, Galactic Clusters, Galactic Structure, Galactic Rotation, Kinematics, Magnitude, Metric Space
Scientific paper
A new version of the oldest approach to estimating the distances of galaxies-direct comparison with our Galaxy-is proposed to relate the extragalactic distance scale to the basic metric, photometric, and kinematic scale factors of the Galaxy. These include the galactocentric distance of the Sun, R0, the total magnitude of the Galaxy, M0T, and its spheroidal component, M0I, the galactic rotation velocity of the local standard of rest, V(Rsun), the central velocity dispersion συ (0) of the spheroidal component, and related parameters.
The following "most probable" values and their mean errors are adopted from a variety of recent determinations: morphological type of galaxy, SAB(rs)bc (T =4±0.5), Rsun = 8.5±0.5 kpc, M0T(B) = 20.2±0.15, (B-V)M0T = 0.53±0.04, M0I(B) = l8.2±0.3,(B-V) M0I = 0.65±0.05, V(Rsun) = 220±15km s-1, συ(0) = l30±7 km s-1.
1. The zero points of the Tully-Fisher (T-F) relations, - M0T(B) = a(B)+5(log VM -2.2), in the BT system, and - Mc(H) = a(H)+l0(log W20 - 2.5), in the system, are determined in terms of the galactocentric distance of the Sun, Rsun, and the galactic rotation velocity of the local standard of rest, V(Rsun) ≡ V0 ≍ VM, or the corresponding line width W20.
The galactic zero point a(B) agrees within 0.1 mag with that (19.4±0.15) previously derived on the short scale from 11 nearby calibrating galaxies.
Application of the galactic zero point a(H) to 12 local calibrators and 13 spirals in the Virgo S cloud leads to distance moduli only 0.1-0.2 mag smaller on the average than those previously derived on the short scale. The same moduli are, depending on distance, from 0.5 to 1.2 mag smaller than those implied by the long distance scale. The distance moduli derived from both the B- and H-band relations indicate the presence of a 12%- 13% scale error in the long distance scale.
2. The zero points of the Faber-Jackson (F-J) relations in the B0T and V0T systems, - M0T = a + b(log συ - 2.3), where b(B) = 9.0 and b(V) = 8.5, are determined in terms of the central velocity dispersion, συ ≡ συ(0), and total B, V absolute magnitudes, M0I, of the spheroidal component of the Galaxy.
Application to a sample of 10 spirals in the restricted interval 130 < συ < 180 leads to distance moduli μG0συ) in excellent systematic agreement (±0.2 mag) with moduli μ0 on the short distance scale. Comparison with distance moduli μ'0 listed in the RSA catalog on the long distance scale indicates a scale error of 9% per magnitude.
After necessary zero-point corrections, application to 17 E, L galaxies in the Virgo E cluster having συ in the interval 130 < συ < 260 leads to a mean modulus <μG0(συ)> = 30.32±0.14 (internal m.e., or ±0.50 including zero-point errors) in excellent agreement with the mean value (30.37±0.2:) previously derived from a variety of methods on the short distance scale, but 1.44 mag less than the value μ'0 = 31.76 on the long distance scale.
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