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Astron. Astrophys. 334, 395-403 (1998)


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The radial space distribution of KLUN-galaxies up to 200 Mpc: incompleteness or evidence for the behaviour predicted by fractal dimension [FORMULA] 2?

P. Teerikorpi 1, M. Hanski 1, G. Theureau 2, Yu. Baryshev 3, G. Paturel 4, L. Bottinelli 2, 5 and L. Gouguenheim 2, 5

1 Tuorla Observatory, FIN-21500 Piikkiö, Finland
2 Observatoire de Paris-Meudon, CNRS URA1757, F-92195 Meudon Principal Cedex, France
3 Astronomical Institute of the Saint-Petersburg University, 198904 St. Petersburg, Russia
4 Observatoire de Lyon, F-69230 Saint-Genis Laval, France
5 Université Paris-Sud, F-91405 Orsay, France

Received 19 March 1997 / Accepted 4 February 1998

Abstract

We have studied using the KLUN sample of 5171 spiral galaxies having Tully-Fisher distance moduli, the average radial space distribution of galaxies out to a distance of about 200 Mpc (for [FORMULA]  km s-1  Mpc-1). One motivation came from the debate on the fractal dimension [FORMULA] and maximum fractality scale [FORMULA] of the large-scale galaxy distribution (Davis 1997, Guzzo 1997, Pietronero et al. 1997). A specific recent study is the 3-dimensional correlation analysis of the all-sky LEDA data base by Di Nella et al. (1996) who concluded that the galaxy distribution is fractal up to scales of at least 300 Mpc, with fractal dimension [FORMULA]. One would expect to see a signal of this result in the radial space distribution of the all-sky KLUN sample. We have studied this question with a new method based on photometric TF distances, independent of redshift, to construct the number density distribution.

Our main results are:

  1. While scattered below about 20 Mpc, at larger distances the radial distribution starts to follow, in terms of distance modulus [FORMULA], the law [FORMULA] const., using diameter TF relation, and [FORMULA] const. for magnitudes. These are the predictions based on fractal dimensions 2.3 and 2.0, respectively. These radial density gradients are valid up to the limits of KLUN, or about 200 Mpc.
  2. We have tried to understand the derived radial density behaviour as a result of some bias in KLUN or our analysis, however, without success. Numerical simulations have shown that the method itself works, though it somewhat underestimates the radial distribution exponent. If the density law is caused by incompleteness in the diameter limited KLUN sample, then the incompleteness should start at widely different angular diameters [FORMULA] for different values of rotation parameter [FORMULA], which would be quite unexpected. On the other hand, if the derived distribution is correct, the completeness is good down to [FORMULA], as originally intended and previously concluded.
  3. If correlation studies favoring long scale fractality (200 Mpc or more) and [FORMULA] 2 are correct, the position of our Galaxy would be close to average in the Universe, with the galaxy density decreasing around us according to the expected law (Mandelbrot 1982).

Key words: galaxies: spiral – galaxies: distances and redshifts – cosmology: large-scale structure of Universe

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998

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