1,814 research outputs found
Direct reconstruction of dynamical dark energy from observational Hubble parameter data
Reconstructing the evolution history of the dark energy equation of state
parameter directly from observational data is highly valuable in
cosmology, since it contains substantial clues in understanding the nature of
the accelerated expansion of the Universe. Many works have focused on
reconstructing using Type Ia supernova data, however, only a few studies
pay attention to Hubble parameter data. In the present work, we explore the
merit of Hubble parameter data and make an attempt to reconstruct from
them through the principle component analysis approach. We find that current
Hubble parameter data perform well in reconstructing ; though, when
compared to supernova data, the data are scant and their quality is worse. Both
CDM and evolving models can be constrained within at
redshifts
and even at redshifts 0.1 z 1 by
using simulated data of observational quality.Comment: 25 pages, 11 figure
Bulge formation from SSCs in a responding cuspy dark matter halo
We simulate the bulge formation in very late-type dwarf galaxies from
circumnuclear super star clusters (SSCs) moving in a responding cuspy dark
matter halo (DMH). The simulations show that (1) the response of DMH to sinking
of SSCs is detectable only in the region interior to about 200 pc. The mean
logarithmic slope of the responding DM density profile over that area displays
two different phases: the very early descent followed by ascent till
approaching to 1.2 at the age of 2 Gyrs. (2) the detectable feedbacks of the
DMH response on the bulge formation turned out to be very small, in the sense
that the formed bulges and their paired nuclear cusps in the fixed and the
responding DMH are basically the same, both are consistent with
observations. (3) the yielded mass correlation of bulges to their nuclear
(stellar) cusps and the time evolution of cusps' mass are accordance with
recent findings on relevant relations. In combination with the consistent
effective radii of nuclear cusps with observed quantities of nuclear clusters,
we believe that the bulge formation scenario that we proposed could be a very
promising mechanism to form nuclear clusters.Comment: 27 pages, 11 figures, accepted for publication in Ap
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