219 research outputs found
The light curve in supernova modeled by a continuous radioactive decay of Ni
The UVOIR bolometric light curves are usually modeled by the radioactive
decay. In order to model more precisely the absolute/apparent magnitude versus
time relationship the continuous production of radioactive isotopes is
introduced. A differential equation of the first order with separable variables
is solved.Comment: 5 pages 2 figure
A left and right truncated Schechter luminosity function for quasars
The luminosity function for quasars (QSOs) is usually fitted by a Schechter
function. The dependence of the number of quasars on the redshift, both in the
low and high luminosity regions, requires the inclusion of a lower and upper
boundary in the Schechter function. The normalization of the truncated
Schechter function is forced to be the same as that for the Schechter function,
and an analytical form for the average value is derived. Three astrophysical
applications for QSOs are provided: deduction of the parameters at low
redshifts, behavior of the average absolute magnitude at high redshifts, and
the location (in redshift) of the photometric maximum as a function of the
selected apparent magnitude. The truncated Schechter function with the double
power law and an improved Schechter function are compared as luminosity
functions for QSOs. The chosen cosmological framework is that of the flat
cosmology, for which we provided the luminosity distance, the inverse relation
for the luminosity distance, and the distance modulus.Comment: 18 pages and 10 figure
The oscillating behavior of the pair correlation function in galaxies
The pair correlation function (PCF) for galaxies presents typical
oscillations in the range 20-200 Mpc/h which are named baryon acoustic
oscillation (BAO). We first review and test the oscillations of the PCF when
the 2D/3D vertexes of the Poissonian Voronoi Tessellation (PVT) are considered.
We then model the behavior of the PCF at a small scale in the presence of an
auto gravitating medium having a line/plane of symmetry in 2D/3D. The analysis
of the PCF in an astrophysical context was split into two, adopting a
non-Poissonian Voronoi Tessellation (NPVT). We first analyzed the case of a 2D
cut which covers few voids and a 2D cut which covers approximately 50 voids.
The obtained PCF in the case of many voids was then discussed in comparison to
the bootstrap predictions for a PVT process and the observed PCF for an
astronomical catalog. An approximated formula which connects the averaged
radius of the cosmic voids to the first minimum of the PCF is given.Comment: 19 pages 14 figure
On the number of galaxies at high redshift
The number of galaxies at a given flux as a function of the redshift, , is
derived when the -distance relation is non-standard. In order to compare
different models, the same formalism is also applied to the standard cosmology.
The observed luminosity function for galaxies of the zCOSMOS catalog at
different redshifts is modelled by a new luminosity function for galaxies,
which is derived by the truncated beta probability density function. Three
astronomical tests, which are the photometric maximum as a function of the
redshift for a fixed flux, the mean value of the redshift for a fixed flux, and
the luminosity function for galaxies as a function of the redshift, compare the
theoretical values of the standard and non-standard model with the observed
value. The tests are performed on the FORS Deep Field (FDF) catalog up to
redshift and on the zCOSMOS catalog extending beyond . These three
tests show minimal differences between the standard and the non-standard
models.Comment: 26 pages and 19 figure
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