9,594 research outputs found
Secondary Accceleration of Cosmic Rays by Supernova Shocks
In the common model supernova shock-acceleration of cosmic rays there are two
open questions: 1. where does the high energy cosmic rays below the knee
(10 Gev) come from, and 2. are cosmic ray accelerated only at their
origin or contineuosly during their residence in the Galaxy. We show that
eV light nuclei are probably accelerted by associations of supernovae.
The ratio of the spectra of secondary to primary cosmic rays would be affected
by repeated acceleration (also called reacceleration or secondary acceleration)
in the ISM during their propagation in the galaxy. The observed secondary and
primary CR spectra are used to constrain the amount of such reacceleration by
supernova remnants (SNR). Two cases are considered: weak shocks () of
old, dispersed remnants, and strong shocks () of relatively young
remnants. It is shown that weak shocks produce more reacceleration than what is
permitted in the framework of the standard leaky box (SLB) model, making it
inconsistent with dispersed acceleration that should be produced by SNR. If the
SLB is modified to allow a moderate amount of RA by week shocks, the RA
produced by old SNRs agrees with the rate required to fit the secondary-to
primaray cosmic-ray data, making a self consistent picture. Significant
reacceleration by strong shocks of young SNRs should lead to flattening of the
secondary-to primaray ratio at high energies, near 1TeV/nucleon.Comment: 4 page latex file. Complete uuencoded compressed PS file is also
available at ftp://saba.fiz.huji.ac.il/pub/wandel/cr_icrc.uu or at
http://shum.cc.huji.ac.il/~amri/papers/cr_icrc(tex,ps) In the procceeding of
the 25th ICRC, v.4 p.41
Black Holes and Hosts of Active and Quiescent Galaxies: I. The Black Hole-Bulge Relation revisited
Massive Black Holes detected in the centers of many nearby galaxies show an
approximately linear relation with the luminosity of the host bulge, with the
black hole mass being 0.001-0.002 of the bulge mass. Previous work suggested
that black holes of active (Seyfert 1) galaxies follow a similar relation, but
apparently with a significantly lower value of
(Wandel 1999). New data show that this difference was mainly due to
overestimating the black hole mass in quiescent galaxies and overestimating the
bulge magnitude of Seyfert galaxies. Using new and updated data we show that
AGNs (Seyfert galaxies and quasars) follow the same BH-bulge relation as
ordinary (inactive) galaxies. We derive the BH-bulge relation for a sample of
55 AGNs and 35 quiescent galaxies, finding that broad line AGNs have an average
black hole/bulge mass fraction of with a strong correlation (Mbh
~ Lbulge^{0.9\pm 0.16}). This BH-bulge relation is consistent with the BH-bulge
relation of quiescent galaxies and much tighter than previous results. Narrow
line AGNs appear to have a lower ratio, Mbh/Mbulge ~ 10^{-4}-10^{-3}. We find
this to be a more general feature, the BH/bulge ratio in AGNs being inversely
correlated with the emission-line width, implying a strong linear relation
between the size of the broad emission line region and the luminosity of the
bulge. Finally, combining AGNs with observed and estimated stellar velocity
dispersion, we find a significant correlation (Mbh ~ v^{3.5-5}), consistent
with that of quiescent galaxies.Comment: 11 pages, 7 figures, accepted for publication in the Astrophysical
Journal, submitted July 1
Evolutionary Baldwin Effect in AGN
Assuming Active Galactic Nuclei are powered by accretion onto a massive black
holes we suggest that the growth of the central black hole due to the matter
accreted over the AGN lifetime causes an evolution of the luminosity and
spectrum. We show that the effective temperature of the UV continuum spectrum
is likely to be anti-correlated with the black-hole mass and with the
accretion-powered luminosity. We estimate the change in the equivalent width of
the emission lines due to the growth of the black hole and show that for
plausible evolutionary tracks and effective-temperature models the equivalent
width is anti-correlated with continuum luminosity thus implying an
evolutionary origin to the Baldwin effect.Comment: 12 pages LaTeX, 1 enclosed figure. To appear in the proceedings of
"Quasars as Standard Candles for Cosmology" (May 18-22, 1998, La Serena,
Chile), to be published by ASP, ed. G. Ferlan
Riesz transform for Dunkl Hermite expansion
In the present paper, we establish that Riesz transforms for Dunkl Hermite
expansion as introduced in [4] are singular integral operators with
H\"ormander's type conditions and we show that are bounded on
$L^p(\mathbb{R}^d; d\mu_k) 1 < p < 1.Comment: 13 page
On the BH-galaxy relation of AGN and Narrow Line Seyfert 1 Galaxies
Massive black holes (BHs) are detected in the centers of many nearby galaxies
are linearly correlated with the luminosity of the host bulge (spheroid), the
black hole mass being about 0.1% of the stellar mass. In active galaxies, the
BH mass is best measured by the reverberation mapping (light echo) technique.
We and others have shown that in AGNs the BH mass follows the same relation
with the luminosity of the host galaxy as in ordinary (inactive) galaxies, with
the exception of narrow line AGNs which apparently have significantly lower
values of the BH/bulge mass (or BH/bulge luminosity) ratio. The BH/bulge ratio
is also found to be strongly correlated with the velocity dispersion of the
broad line-emitting gas in the active nucleus. However, in the BH-stellar
velocity relation the difference between broad- and narrow-line AGNs (in
particular NLS1s) seems to be less obvious. We review the subject adding recent
updates and suggestions.Comment: 9 pages, 6 figures, Narrow-Line Seyfert 1 Galaxies and Their Place in
the Universe (NLS1 Milan, Italy
Quantum Behavior of Measurement Apparatus
We precise for the first time the quantum behavior of a measurement apparatus
in the framework of the usual interpretation of quantum physics. We show how
such a behavior can also be studied by the retrodiction of pre-measurement
states corresponding to its responses. We translate in terms of these states
some interesting properties of the behavior of an apparatus, such as the
projectivity, the fidelity, the non-Gaussian character, or the non-classicality
of measurements performed by this one. We also propose an experimental
procedure allowing the tomography of these pre-measurement states for optical
detectors. We illustrate the relevance of these new notions for measurements,
by evaluating them for two detectors widely used in quantum optics: the
avalanche photodiode and the homodyne detection.Comment: APS Preprint format : 19 pages with 6 figures, a new figure (Fig. 2)
was added. Questions and comments are welcom
On the bio-habitability of M-dwarf planets
The recent detection of Earth-sized planets in the habitable zone of Proxima
Centauri, Trappist-1 and many other nearby M-type stars has led to
speculations, whether liquid water and life actually exist on these planets. To
a large extent, the answer depends on their yet unknown atmospheres, which may
though be within observational reach in the near future by JWST, ELT and other
planned telescopes. We consider the habitability of planets of M-type stars in
the context of their atmospheric properties, heat transport and irradiation.
Instead of the traditional definition of the habitable zone, we define the
bio-habitable zone, where liquid water and complex organic molecules can
survive on at least part of the planetary surface. The atmospheric impact on
the temperature is quantified in terms of the heating factor (a combination of
greenhouse heating, stellar irradiation, albedo etc.) and heat redistribution
(horizontal energy transport). We investigate the bio-habitable domain (where
planets can support surface liquid water and organics) in terms of these two
factors. Our results suggest that planets orbiting M-type stars may have
life-supporting temperatures, at least on part of their surface, for a wide
range of atmospheric properties. We apply this analyses to Proxima b and the
Trappist-1 system. Finally we discuss the implications to the search of
biosignatures and demonstrate how they may be used to estimate the abundance of
photosynthesis and biotic planets.Comment: 33 pages, 15 figure
On the integral representations for Dunkl kernels of type
We give an explicit integral formula for the Dunkl kernel associated to root
system of type and parameter , by exploiting recent result in [1]
The Mass-Luminosity Relation in AGN
Probably the most fundamental characteristic of the quasar-AGN power house,
the mass of the central black hole, is the least well known. I review the three
main classes of mass estimation methods---broad emission-line kinematics, X-ray
variability and accretion-disk modeling, and the masses they give in terms of
the Eddington ratio, . The broad emission lines are probably the
best probe of the central mass. They provide mass estimates that suggest a
narrow spread for the Eddington ratio - 1--2 orders of magnitude over more than
six orders of magnitude in continuum luminosity, possibly indicating a
universal ratio for AGN. However, other methods give a larger spread and
possibly a luminosity- dependent Eddington ratio. Potential sources of errors
and bias are discussed.Comment: 13 pages, Latex (aspconf.sty), 4 postscript figures. Also available
at http://shum.cc.huji.ac.il/~amri/papers/ml Review to appear in procs. of
"Structure and Kinematics of Quasar Broad Line Regions" (23-26 March 1998,
Lincoln, Nebraska) eds. Gaskell, C. M., Brandt, W. N., Dietrich, M.,
Dultzin-Hacyan, D. & Eracleous, M. (ASP Press: San Francisco
Spectral Dependence of the Broad Emission-Line Region in AGN
We derive a theoretical relation between , the size of the
broad-emission-line region of active galactic nuclei, and the observed soft
X-ray luminosity and spectrum. We show that in addition to the well known
scaling, should depend also on the soft X-ray
spectral slope and derive the expected relation between and the X-ray
luminosity and spectral index. Applying this relation to calculate a predicted
BLR radius for ten AGN with reverberation data, we show that including the
dependence on the spectrum improves the agreement between the calculated BLR
radius and the radius independently determined from reverberation mapping.
Similarly, we evaluate an expression for the line width, and show that
including the dependence on the spectrum significantly improves the agreement
between the calculated BLR velocity dispersion and the observed FWHM of the
H line.Comment: 8 pages, Latex (aas2pp4.sty), 5 postscript figures. Also available at
http://shum.cc.huji.ac.il/~amri/papers/blr Accepted for publication in the
Astrophysical Journal Letter
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