11,342 research outputs found
Extended Gas in Seyfert Galaxies: Near Infrared Observations of NGC 2110 and Circinus
We present results of near--IR long-slit spectroscopy in the J and K bands of
the Seyfert 2 galaxies NGC 2110 and Circinus, investigating the gaseous
distribution, excitation, reddening and kinematics. In NGC 2110, the emission
line ratio [FeII]/Pa beta increases towards the nucleus (to ~ 7). The nuclear
[Fe II]1.257 (microns) and Pa beta lines are broader (FWHM ~ 500 km/s) than the
H2 (2.121) line (FWHM ~ 300 km/s). Both these results suggest that shocks,
driven by the radio jet, are an important source of excitation of [Fe II]. The
H2 excitation appears to be dominated by X-rays from the nucleus. In Circinus,
both [FeII]/Pa beta and H2/Br gamma decrease from ~ 2 at 4 arcsec from the
nucleus to nuclear values of ~ 0.6 and ~ 1, respectively, suggesting that the
starburst dominates the nuclear excitation, while the AGN dominates the
excitation further out (r > 2 arcsec). For both galaxies, the gaseous
kinematics are consistent with circular rotation in the plane of the disk. Our
rotation curves suggest that the nucleus (identified with the peak of the IR
continuum) is displaced from the kinematic centre of the galaxies. This effect
has been observed previously in NGC 2110 based on the kinematics of optical
emission lines, but the displacement is smaller in the infrared, suggesting the
effect is related to obscuration. The continuum J-K colours of the nuclear
region indicate a red stellar population in NGC 2110 and a reddened young
stellar population in Circinus. Right at the nucleus of both galaxies, the
colours are redder, apparently a result of hot dust emission from the inner
edge of a circumnuclear torus.Comment: 11 pages, 14 figures, accepted for publication in MNRA
The issue of time in generally covariant theories and the Komar-Bergmann approach to observables in general relativity
Diffeomorphism-induced symmetry transformations and time evolution are
distinct operations in generally covariant theories formulated in phase space.
Time is not frozen. Diffeomorphism invariants are consequently not necessarily
constants of the motion. Time-dependent invariants arise through the choice of
an intrinsic time, or equivalently through the imposition of time-dependent
gauge fixation conditions. One example of such a time-dependent gauge fixing is
the Komar-Bergmann use of Weyl curvature scalars in general relativity. An
analogous gauge fixing is also imposed for the relativistic free particle and
the resulting complete set time-dependent invariants for this exactly solvable
model are displayed. In contrast with the free particle case, we show that
gauge invariants that are simultaneously constants of motion cannot exist in
general relativity. They vary with intrinsic time
Gemini/GMOS Transmission Spectral Survey: Complete Optical Transmission Spectrum of the hot Jupiter WASP-4b
We present the complete optical transmission spectrum of the hot Jupiter
WASP-4b from 440-940 nm at R ~ 400-1500 obtained with the Gemini Multi-Object
Spectrometers (GMOS); this is the first result from a comparative
exoplanetology survey program of close-in gas giants conducted with GMOS.
WASP-4b has an equilibrium temperature of 1700 K and is favorable to study in
transmission due to a large scale height (370 km). We derive the transmission
spectrum of WASP-4b using 4 transits observed with the MOS technique. We
demonstrate repeatable results across multiple epochs with GMOS, and derive a
combined transmission spectrum at a precision about twice above photon noise,
which is roughly equal to to one atmospheric scale height. The transmission
spectrum is well fitted with a uniform opacity as a function of wavelength. The
uniform opacity and absence of a Rayleigh slope from molecular hydrogen suggest
that the atmosphere is dominated by clouds with condensate grain size of ~1 um.
This result is consistent with previous observations of hot Jupiters since
clouds have been seen in planets with similar equilibrium temperatures to
WASP-4b. We describe a custom pipeline that we have written to reduce GMOS
time-series data of exoplanet transits, and present a thorough analysis of the
dominant noise sources in GMOS, which primarily consist of wavelength- and
time- dependent displacements of the spectra on the detector, mainly due to a
lack of atmospheric dispersion correction.Comment: 23 pages, 12 figures, accepted for publication in AJ, 2017 July
Gravitational Chern-Simons and the adiabatic limit
We compute the gravitational Chern-Simons term explicitly for an adiabatic
family of metrics using standard methods in general relativity. We use the fact
that our base three-manifold is a quasi-regular K-contact manifold heavily in
this computation. Our key observation is that this geometric assumption
corresponds exactly to a Kaluza-Klein Ansatz for the metric tensor on our three
manifold, which allows us to translate our problem into the language of general
relativity. Similar computations have been performed in a paper of Guralnik,
Iorio, Jackiw and Pi (2003), although not in the adiabatic context.Comment: 17 page
ARIA 2016 : Care pathways implementing emerging technologies for predictive medicine in rhinitis and asthma across the life cycle
European Innovation Partnership on Active and Healthy Ageing Reference Site MACVIA-France, EU Structural and Development Fund Languedoc-Roussillon, ARIA.Peer reviewedPublisher PD
Reparameterization invariants for anisotropic Bianchi I cosmology with a massless scalar source
Intrinsic time-dependent invariants are constructed for classical, flat,
homogeneous, anisotropic cosmology with a massless scalar material source.
Invariance under the time reparameterization-induced canonical symmetry group
is displayed explicitly.Comment: 28 pages, to appear in General Relativity and Gravitation.
Substantial revisions: added foundational overview section 2, chose new
intrinsic time variable, worked with dimensionless variables, added appendix
with comparison and criticism of other approache
The Physical Role of Gravitational and Gauge Degrees of Freedom in General Relativity - II: Dirac versus Bergmann observables and the Objectivity of Space-Time
(abridged)The achievements of the present work include: a) A clarification of
the multiple definition given by Bergmann of the concept of {\it (Bergmann)
observable. This clarification leads to the proposal of a {\it main conjecture}
asserting the existence of i) special Dirac's observables which are also
Bergmann's observables, ii) gauge variables that are coordinate independent
(namely they behave like the tetradic scalar fields of the Newman-Penrose
formalism). b) The analysis of the so-called {\it Hole} phenomenology in strict
connection with the Hamiltonian treatment of the initial value problem in
metric gravity for the class of Christoudoulou -Klainermann space-times, in
which the temporal evolution is ruled by the {\it weak} ADM energy. It is
crucial the re-interpretation of {\it active} diffeomorphisms as {\it passive
and metric-dependent} dynamical symmetries of Einstein's equations, a
re-interpretation which enables to disclose their (nearly unknown) connection
to gauge transformations on-shell; this is expounded in the first paper
(gr-qc/0403081). The use of the Bergmann-Komar {\it intrinsic
pseudo-coordinates} allows to construct a {\it physical atlas} of 4-coordinate
systems for the 4-dimensional {\it mathematical} manifold, in terms of the
highly non-local degrees of freedom of the gravitational field (its four
independent {\it Dirac observables}), and to realize the {\it physical
individuation} of the points of space-time as {\it point-events} as a
gauge-fixing problem, also associating a non-commutative structure to each
4-coordinate system.Comment: 41 pages, Revtex
Signals of R-parity violating supersymmetry in neutrino scattering at muon storage rings
Neutrino oscillation signals at muon storage rings can be faked by
supersymmetric (SUSY) interactions in an R-parity violating scenario. We
investigate the -appearance signals for both long-baseline and near-site
experiments, and conclude that the latter is of great use in distinguishing
between oscillation and SUSY effects. On the other hand, SUSY can cause a
manifold increase in the event rate for wrong-sign muons at a long-baseline
setting, thereby providing us with signatures of new physics.Comment: 7 pages LaTeX, 4 ps figures, accepted for publication in Phys. Rev.
Lagrangian approach to a symplectic formalism for singular systems
We develop a Lagrangian approach for constructing a symplectic structure for
singular systems. It gives a simple and unified framework for understanding the
origin of the pathologies that appear in the Dirac-Bergmann formalism, and
offers a more general approach for a symplectic formalism, even when there is
no Hamiltonian in a canonical sense. We can thus overcome the usual limitations
of the canonical quantization, and perform an algebraically consistent
quantization for a more general set of Lagrangian systems.Comment: 30 page
Lepton number violating interactions and their effects on neutrino oscillation experiments
Mixing between bosons that transform differently under the standard model
gauge group, but identically under its unbroken subgroup, can induce
interactions that violate the total lepton number. We discuss four-fermion
operators that mediate lepton number violating neutrino interactions both in a
model-independent framework and within supersymmetry (SUSY) without R-parity.
The effective couplings of such operators are constrained by: i) the upper
bounds on the relevant elementary couplings between the bosons and the
fermions, ii) by the limit on universality violation in pion decays, iii) by
the data on neutrinoless double beta decay and, iv) by loop-induced neutrino
masses. We find that the present bounds imply that lepton number violating
neutrino interactions are not relevant for the solar and atmospheric neutrino
problems. Within SUSY without R-parity also the LSND anomaly cannot be
explained by such interactions, but one cannot rule out an effect
model-independently. Possible consequences for future terrestrial neutrino
oscillation experiments and for neutrinos from a supernova are discussed.Comment: 28 pages, 2 figures, Late
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