Analysis of the velocity-distance diagrams in the presence of the Great Attractor

Details Analysis of the velocity-distance diagrams in the presence of the Great Attractor Analysis of the velocity-distance diagrams in the presence of the Great Attractor

Apr 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...284..369e&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 284, no. 2, p. 369-385

Computer Science

Numerical Analysis

10

Astronomical Models, Distance, Numerical Analysis, Stellar Luminosity, Velocity Distribution, Cosmology, Elliptical Galaxies, Gravitation, Kinematics, Red Shift

Scientific paper

In the present paper we study the appearance of velocity-distance diagrams, when the distances are calculated by either the direct of the inverse Tully-Fisher (TF) relation and when the velocity field is generated by a spherically symmetric mass concentration, and try to understand some contradicting reports on the kinematics close to the Great Attractor (GA). Since the application of Malmquist corrections for the distance moduli is not a straightforward task in the presence of a general velocity field, we also searched for methods for obtaining a minimally biased subsample from the data with direct TF-distance and tested the influence of the chosen inverse relation. We first conducted a series of random number simulations by generating direct and inverse TF-distances and line-of-sight velocities for a synthetic data set. We conclude that instead of the V vs. RTF(sub dir) and V vs. RTF(sub inv) diagrams (both being difficult to correct for the general Malmquist bias), the R vs. V diagrams are the more basic ones when used together in such a way that in the RTF(sub dir) vs. V diagram one excludes galaxies having log VM values below some beforehand assigned limit (maximum bias allowed) and in the RTF(sub inv) vs. V diagram one calculates the mean value of RTF(sub inv) V values being careful with the galaxies in the central cone. These methods are -- however -- sensitive to the progressive incompleteness of the sample and to the uncertainty in the inverse TF-relation, respectively. We compared our model results with existing real data (Mathewson et al. 1992b). The log VM-class analysis reveals the frontside infall with the expected angular dependence. However, though there are galaxies that would seem to follow the S-curve in the central region, it seems to be impossible to extend the method beyond the putative center, because of the incompleteness of the data. On the other hand, by using a realistic slope for the inverse relation, also the backside infall was revealed up to distances far larger than in any previous sample studied. This is through only a tentative result, the uncertainty being traced back to our knowledge of the inverse TF-relation.

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