373 research outputs found
1.4-GHz Luminosity Function of Galaxies from the Las Campanas Redshift Survey
A preliminary 1.4 GHz RLF at redshift of about 0.14 is derived from the Las
Campanas Redshift Survey (LCRS) and the NVSS radio data. No significant
evolution has been found at this redshift in comparison to the 'local' RLF.Comment: 2 pages including 2 Postscript figures, uses crckapb10.st
The new sample of giant radio sources III. Statistical trends and correlations
In this paper we analyse whether `giant' radio galaxies (GRGs) differ from
`normal'-size galaxies (NSGs) except for the linear extent of their radio
structure. We compare a number of properties of GRGs with the corresponding
properties of NSGs, and analyse the statistical trends and correlations of
physical parameters, homogeneously determined for the sources, with their
`fundamental' parameters. Using the Pearson partial-correlation test on the
correlation between two variables in the presence of one or two other
variables, we examine which correlation is the strongest. The analysis clearly
shows that GRGs do not form a separate class of radio sources. They most likely
evolve with time from smaller sources, however under specific circumstances.
Analysing properties of GRGs and NSGs together, we find that (i) the core
prominence does not correlate with the total radio luminosity (as does the core
power), but it anti-correlates with the surface brightness of the lobes of
sources, (ii) the energy density (and possibly the internal pressure) in the
lobes is independent of redshift for constant radio luminosity and size of the
sources, (iii) the equipartition magnetic-field strength, transformed into
constant source luminosity and redshift, strongly correlates with the source
size. We argue that this B_{eq} - D correlation reflects a more fundamental
correlation between B_{eq} and the source age, (iv) both the rotation and
depolarisation measures suggest Faraday screens local to the lobes of sources,
however their geometry and the composition of intervening material cannot be
determined from the global polarisation characteristics.Comment: 10 pages, 8 figures, 6 tables. Accepted for publication in A&
GB2 0909+353: One of the Largest Double Radio Source
The evidence are given that the radio source GB2 0909+353 (GB2 catalogue:
Machalski 1978; ICRS 2000.0 coordinates: 09 12 51.7, +35 10 10) is likely one
of the largest classical doubles known, though its optical identification is
not certain. Our deep VLA observations at 5 GHz did not reveal a radio core
brighter than 0.5 mJy/beam at this frequency. Thus a distance to the source is
evaluated using photometric -- redshift estimates of the faint galaxies in the
optical field. The equipartition magnetic field and energy density in the
source is calculated and compared with corresponding parameters of other
`giant' radio sources known, showing extremely low values of both physical
parameters of the source investigated. On the other hand, the age of
relativistic electrons, and the advance speed of the `hot spot' in the source
are typical for much smaller and brighter 3CR sources.Comment: 10 pages with 3 Postscript figures, accepted to Acta Astronomic
First pterosaur remains from the Cretaceous of Poland
The first records of pterosaurs from the Cretaceous of Poland are reported, on the basis of fragmentary remains from the marine Upper Albian (Lower Cretaceous) of the Annopol Anticline, central Poland. The new material consists of four bone fragments, tentatively interpreted as: 1) a portion of wing phalanx; 2) a medial element of fused skull bones (parietal crest?); 3) a fragmentary carpal or tarsal; and 4) a distal phalanx of the pes (or a very small fragment of a long cervical vertebra). Previously, only the remains of marine vertebrates have been reported from the Cretaceous of the Annopol area. The pterosaur fossils studied most probably belonged to individuals that died while over the sea. The possibility that they represent remains dropped from floating carcasses, introduced into the marine environment by rivers, is regarded as less probable, as there are no remains of dinosaurs or other terrestrial fauna in the Annopol deposits
Giant Radio Sources in View of the Dynamical Evolution of FRII-type Population
The time evolution of giant (D>1 Mpc) lobe-dominated galaxies is analysed on
the basis of dynamical evolution of the entire FRII-type population.Comment: 4 pages, 2 Postscript figures, uses baltlat1.sty To be published in
"Radio astronomy at 70: from Karl Jansky to microjansky", JENAM-2003
Symposium, eds. L.Gurvits and S.Frey, (Baltic Astronomy
Giant Radio Sources in View of the Dynamical Evolution of FRII-type Population. I. The Observational Data, and Basic Physical Parameters of Sources Derived from the Analytical Model
The time evolution of giant lobe-dominated radio galaxies (with projected
linear size D>1 Mpc if H_{0}=50 km/s/Mpc and q_{0}=0.5 is analysed on the basis
of dynamical evolution of the entire FRII-type population. Two basic physical
parameters, namely the jet power Q_{0} and central density of the galaxy
nucleus rho0 are derived for a sample of giants with synchrotron ages reliably
determined, and compared with the relevant parameters in a comparison sample of
normal-size sources consisting of 3C, B2, and other sources. Having the
apparent radio luminosity P and linear size D of each sample source, Q_{0} and
rho_{0} are obtained by fitting the dynamical model of Kaiser et al. (1997). We
find that: (i) there is not a unique factor governing the source size; they are
old sources with temperate jet power (Q_{0}) evolved in a relatively
low-density environment (rho_{0}). The size is dependent, in order of
decreasing partial correlation coefficients, on age; then on Q_{0}; next on
rho_{0}. (ii) A self-similar expansion of the sources' cocoon seems to be
feasible if the power supplied by the jets is a few orders of magnitude above
the minimum-energy value. In other cases the expansion can only initially be
self-similar; a departure from self-similarity for large and old sources is
justified by observational data of giant sources. (iii) An apparent increase of
the lowest internal pressure value observed within the largest sources' cocoon
with redshift is obscured by the intrinsic dependence of their size on age and
the age on redshift, which hinders us from making definite conclusions about a
cosmological evolution of intergalactic medium (IGM) pressure.Comment: 36 pages, 8 figures, 7 table
A dynamical model for FR II type radio sources with terminated jet activity
The extension of the KDA analytical model of FR II-type source evolution
originally assuming a continuum injection process in the jet-IGM (intergalactic
medium) interaction towards a case of the jet's termination is presented and
briefly discussed. The dynamical evolution of FR II-type sources predicted with
this extended model, hereafter referred to as KDA EXT, and its application to
the chosen radio sources. Following the classical approach based on the
source's continuous injection and self-similarity, I propose the effective
formulae describing the length and luminosity evolution of the lobes during an
absence of the jet flow, and present the resulting diagrams for the
characteristics mentioned. Using an algorithm based on the numerical
integration of a modified formula for jet power, the KDA EXT model is fitted to
three radio galaxies. Their predicted spectra are then compared to the observed
spectra, proving that these fits are better than the best spectral fit provided
by the original KDA model of the FR II-type sources dynamical evolution
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