Holes within galaxies : the egg or the hen ?

Unsustained matter distributions unescapely collapse unless fragmentation and centrifugal or pressure support take place. Starting from the above evidence, supermassive compact objects at the centre of large-mass galaxies (defined as “holes”) are conceived as the end-product of the gravitational collapse of local density maxima (defined as “central collapse”) around which positive density perturbations (overdensities) are located. At the beginning of evolution, assumed to occur at recombination epoch, local density maxima are idealized as homogeneous peaks, while the surrounding envelopes are described by a power-law density profile, ρ(r) ∝ rb−3, 0 ≤ b ≤ 3, where b = 0 represents a massless atmosphere and b = 3 a homogeneous layer. The dependence of the density profile on a second parameter, chosen to be the ratio between peak and total (truncated) mass, κ = Mpk/Mtr, is analysed. Overdensity evolution is discussed in the context of quintessence cosmological models, which should be useful in dealing with the virialized phase. Aiming to describe the central collapse, further investigation is devoted to a special case where the quintessence effect is equivalent to additional curvature (w = −1/3), and overdensities exhibit the selected density profile at recombination ∗Astronomy Department, Padua Univ., Vicolo Osservatorio 2, I-35122 Padova, Italy email: [email protected]