1,117 research outputs found
Extreme Galactic-Winds and Starburst in IR Mergers and IR QSOs
We report -as a part of a long-term study of mergers and IR QSOs- detailed
spectroscopic evidences for outflow (OF) and/or Wolf Rayet features in: (i) low
velocity OF in the ongoing mergers NGC 4038/39 and IRAS 23128-5919; (ii)
extreme velocity OF (EVOF) in the QSOs IRAS 01003-2238 and IRAS 13218+0552;
(iii) OF and EVOF in a complete sample of ultra-luminous IR galaxies/QSOs ("The
IRAS 1 Jy MKO-KPNO Survey", of 118 objects). We found EVOF in IRAS 11119+3257,
14394+5332, 15130+1958 and 15462-0450. The OF components detected in these
objects were mainly associated to starburst processes: i.e., to galactic-winds
generated in multiple type II SN explosions and massive stars. The EVOF were
detected in objects with strong starburst plus obscured IR QSOs; which suggest
that interaction of both processes could generate EVOF. In addition, we analyze
the presence of Wolf Rayet features in the large sample of Bright PG-QSOs
(Boroson and Green 1992), and nearby mergers and galactic-wind galaxies. We
found clear WR features in the Fe II QSOs (type I): PG 1244+026, 1444+407,
1448+273, 1535+547; and in the IR merger Arp 220. HST archive images of IR+BAL
QSOs show in practically all of these objects "arc or shell" features probably
associated to galactic-winds (i.e., to multiple type II SN explosions) and/or
merger processes. Finally, we discuss the presence of extreme starburst and
galactic wind as a possible evolutive link between IR merger and IR QSOs; where
the relation between mergers and extreme starburst (with powerful
galactic-winds) plays in important role, in the evolution of galaxies.Comment: 14 pages, 6 figure
Comparison of 3-Dimensional and 1-Dimensional Schemes in the calculation of Atmospheric Neutrinos
A 3-dimensional calculation of atmospheric neutrinos flux is presented, and
the results are compared with those of a 1-dimensional one. In this study,
interaction and propagation of particles is treated in a 3-dimensional way
including the curvature of charged particles due to the geomagnetic field,
which is assumed to be a dipole field. The purpose of this paper is limited to
the comparison of calculation schemes. The updated flux value with new
interaction model and primary flux model will be reported in a separate paper.
Except for nearly horizontal directions, the flux is very similar to the
result of 1 dimensional calculations. However, for near-horizontal directions
an enhancement of the neutrino flux is seen even at energies as high as 1 GeV.
The production height of neutrinos is lower than the prediction by
1-dimensional calculation for near-horizontal directions, and is a little
higher for near-vertical directions. However, the difference is not evident
except for near-horizontal directions.Comment: 22 pages, 15figure
Getting the Best of Both Worlds? Developing Complementary Equation-Based and Agent-Based Models
We argue that building agent-based and equation-based versions of the same theoretical model is a fruitful way of gaining insights into real-world phenomena. We use the epistemological concept of “models as isolations and surrogate systems” as the philosophical underpinning of this argument. In particular, we show that agent-based and equation-based approaches align well when used simultaneously and, contrary to some common misconceptions, should be considered complements rather than substitutes. We illustrate the usefulness of the approach by examining a model of the long-run relationship between economic development and inequality (i.e., the Kuznets hypothesis)
GeV to TeV astrophysical tau neutrinos
Neutrinos with energy greater than GeV are copiously produced in the p(A,p)
interactions occurring in several astrophysical sites such as (i) the earth
atmosphere, (ii) our galactic plane as well as in (iii) the galaxy clusters. A
comparison of the tau and mu neutrino flux in the presence of neutrino
oscillations from these three representative astrophysical sites is presented.
It is pointed out that the non-atmospheric tau neutrino flux starts dominating
over the downward going atmospheric tau neutrino flux for neutrino energy E as
low as 10 GeV. This energy value is much lower than the energy value, E \geq
5\times 10^4 GeV, estimated for the dominance of the non-atmospheric mu
neutrino flux, in the presence of neutrino oscillations. Future prospects for
possible observations of non-atmospheric tau neutrino flux are briefly
mentioned.Comment: 17 pages, 5 figures (to appear in PLB
Atmospheric neutrino flux from 3-dimensional simulation
The atmospheric muon and neutrino flux have been simulated using the same
approach which successfully accounted for the recent secondary proton, electron
and positron flux measurements in orbit by the AMS experiment. For the muon
flux, a good agreement is obtained with the CAPRICE and HEAT data for altitudes
ranging from sea level up to about 38 km. The general features of the
calculated atmospheric neutrino flux are reported and discussed. The flux
obtained at the Super-Kamiokande experiment location are reported and compared
with other calculations. For low neutrino energies the flux obtained is
significantly smaller than that used in the data analysis of underground
experiment. The simulation results for the SOUDAN experiment site are also
reported.Comment: 33 pages, 27 figures, 12 tables, final version for Phys. Rev.
Simulation of Atmospheric Muon and Neutrino Fluxes with CORSIKA
The fluxes of atmospheric muons and neutrinos are calculated by a three
dimensional Monte Carlo simulation with the air shower code CORSIKA using the
hadronic interaction models DPMJET, VENUS, GHEISHA, and UrQMD. For the
simulation of low energy primary particles the original CORSIKA has been
extended by a parametrization of the solar modulation and a microscopic
calculation of the directional dependence of the geomagnetic cut-off functions.
An accurate description for the geography of the Earth has been included by a
digital elevation model, tables for the local magnetic field in the atmosphere,
and various atmospheric models for different geographic latitudes and annual
seasons. CORSIKA is used to calculate atmospheric muon fluxes for different
locations and the neutrino fluxes for Kamioka. The results of CORSIKA for the
muon fluxes are verified by an extensive comparison with recent measurements.
The obtained neutrino fluxes are compared with other calculations and the
influence of the hadronic interaction model, the geomagnetic cut-off and the
local magnetic field on the neutrino fluxes is investigated.Comment: revtex, 19 pages, 19 Postscript figures, submitted to Phys. Rev.
The Unified Model of Active Galactic Nuclei: II. Evolutionary Connection
(Abbreviated) We assemble a sample composed of 243 nearby Seyfert galaxies
with redshifts to test the unification scheme. The sample contains
94 BLS1s, 44 NLS1s, 36 X-ray absorbed HBLR S2s, 42 X-ray absorbed non-HBLR S2s
and 27 X-ray unabsorbed Seyfert 2s (unabsorbed non-HBLR S2s and HBLR S2s). We
find that: 1) NLS1s have less massive black hole masses than BLS1s; 2) HBLRS2s
have the same mass distribution of the black holes with BLS1s; 3) the absorbed
non-HBLR S2s have less massive black holes than HBLR S2s; 4) unabsorbed
non-HBLR S2s have the most massive black holes. We thus have a queue of black
hole masses from small to large: narrow to broad line Seyfert galaxies,
providing new evidence for the evolutionary sequence of Seyfert galaxies. We
find that the opening angles of the torus in NLS1s and absorbed non-HBLR S2s
are significantly smaller than that in BLS1s and HBLR S2s. The growth of the
black holes and increases of the opening angles of the tori determine the
various appearances of Seyfert galaxies. We also find that the unabsorbed
Seyfert 2 galaxies could be caused by low gas-to-dust ratios in the present
sample. This indicates that the star formation histories could be different in
the unabsorbed from in absorbed Seyfert 2 galaxies, showing evidence for
suppressed star formation by black hole activities. We outline a new
unification scheme based on the orientation hypothesis: Seyfert galaxies can be
unified by including growth of black holes, Eddington ratios, changing opening
angles of tori and gas-to-dust ratios in the tori. Seyfert galaxies are tending
to finally evolve to unabsorbed non-HBLR Seyfert 2 galaxies, in which the black
holes are accreting with low accretion rates and both the broad line region and
dusty torus disappear.Comment: ApJ, vol 661 (2007), in pres
The central structure of Broad Absorption Line QSOs: observational characteristics in the cm-mm wavelength domain
Accounting for ~20% of the total QSO population, Broad Absorption Line QSOs
are still an unsolved problem in the AGN context. They present wide troughs in
the UV spectrum, due to material with velocities up to 0.2 c toward the
observer. The two models proposed in literature try to explain them as a
particular phase of the evolution of QSOs or as normal QSOs, but seen from a
particular line of sight.
We built a statistically complete sample of Radio-Loud BAL QSOs, and carried
out an observing campaign to piece together the whole spectrum in the cm
wavelength domain, and highlight all the possible differences with respect to a
comparison sample of Radio-Loud non-BAL QSOs. VLBI observations at high angular
resolution have been performed, to study the pc-scale morphology of these
objects. Finally, we tried to detect a possible dust component with
observations at mm-wavelengths.
Results do not seem to indicate a young age for all BAL QSOs. Instead a
variety of orientations and morphologies have been found, constraining the
outflows foreseen by the orientation model to have different possible angles
with respect to the jet axis
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