3 research outputs found
The luminosity function of field galaxies
Schmidt's method for construction of luminosity function of galaxies is
generalized by taking into account the dependence of density of galaxies from
the distance in the near Universe. The logarithmical luminosity function (LLF)
of field galaxies depending on morphological type is constructed. We show that
the LLF for all galaxies, and also separately for elliptical and lenticular
galaxies can be presented by Schechter function in narrow area of absolute
magnitudes. The LLF of spiral galaxies was presented by Schechter function for
enough wide area of absolute magnitudes: . Spiral galaxies differ slightly by
parameter . At transition from early spirals to the late spirals parameter in
Schechter function is reduced. The reduction of mean luminosity of galaxies is
observed at transition from elliptical galaxies to lenticular galaxies, to
early spiral galaxies, and further, to late spiral galaxies, in a bright end, .
The completeness and the average density of samples of galaxies of different
morphological types are estimated. In the range the mean number density of all
galaxies is equal 0.127 Mpc-3.Comment: 14 page, 8 figures, to appear in Astrophysic
Closest Star Seen Orbiting the Supermassive Black Hole at the Centre of the Milky Way
Measurements of stellar velocities and variable X-ray emission near the
centre of the Milky Way have provided the strongest evidence so far that the
dark mass concentrations seen in many galactic nuclei are likely supermassive
black holes, but have not yet excluded several alternative configurations. Here
we report ten years of high resolution astrometric imaging that allow us to
trace two thirds of the orbit of the star currently closest to the compact
radio source and massive black hole candidate SgrA*. In particular, we have
observed both peri- and apocentre passages. Our observations show that the star
is on a bound, highly elliptical Keplerian orbit around SgrA*, with an orbital
period of 15.2 years and a peri-centre distance of only 17 light hours. The
orbital elements require an enclosed point mass of 3.7+-1.5x10^6 solar masses.
The data exclude with high confidence that the central dark mass consists of a
cluster of astrophysical objects or massive, degenerate fermions, and strongly
constrain the central density structure.Comment: 13 pages, 3 figures, scheduled for publication in Nature on 17 Oct
200