Title:

	Minivoids in the Local Volume



Igor Karachentsev
Special Astrophysical Observatory, Russian Academy of Science



Abstract:

A neighboring volume of 7.5 Mpc radius is considered, which contains
355 galaxies with accurately measured distances, to detect the nearest
empty volumes. Using a simple void detection algorithm, we found six
large minivoids, each of more than 30 Mpc^3. Besides them, 24 middle-
size "bubbles" of more than 5 Mpc^3 volume are detected, as well as 52
small "pores". The six largest minivoids occupy 58% of the considered
volume. Addition of the bubbles and pores to them increase the total
empty volume up to 81%. The detected local voids look like oblong
potatoes with typical axial ratios 0.75 and 0.62 in the triaxial
ellipsoid approximation.  A correlation Gamma-function of the Local
Volume galaxies follows a power law with a formally calculated fractal
dimension D = 1.5.

We found that galaxies surrounding the local minivoids do not differ
significantly from other nearby galaxies in their luminosity, but have
appreciably higher hydrogen mass-to-luminosity ratios and also higher
star formation rates. An effect of local expansion of typical minivoid
is recognized to be about (28+-19) km/s or delta H/Ho = (25+-15)%.

Some properties of more distant local voids within 25 Mpc are briefly
outlined too.