1,276 research outputs found
Generation of Noise Time Series with arbitrary Power Spectrum
Noise simulation is a very powerful tool in signal analysis helping to
foresee the system performance in real experimental situations. Time series
generation is however a hard challenge when a robust model of the noise sources
is missing. We present here a simple computational technique which allows the
generation of noise samples of fixed length, given a desired power spectrum. A
few applications of the method are also discussed.Comment: 4 pages, 7 figure
Extragalactic planetary nebulae as mass tracers: biases in the estimate of dynamical quantities
Planetary Nebulae (PNe) are very important kinematical tracers of the outer
regions of early-type galaxies, where the integrated light techniques fail.
Under ad hoc assumptions, they allow measurements of rotation velocity and
velocity dispersion profile from descrete radial velocity fields. We present
the results on the precision allowed by different set of radial velocity
samples, discuss the hypotheses in the analysis of descrete velocity fields and
their impact on the inferred kinematics of the stellar population.Comment: 4 pages, 2 figures. To appear on ``Galaxy Dynamics: from Early
Universe to the Present'', ASP Conf. Ser., F. Combes, G.A. Mamon and V.
Charmandaris (eds.
Spectral decomposition of the stellar kinematics in the polar disk galaxy NGC 4650A
Context. The prototype of Polar Ring Galaxies NGC 4650A contains two main
structural components, a central spheroid, which is the host galaxy, and an
extended polar disk. Both photometric and kinematic studies revealed that these
two components co-exist on two different planes within the central regions of
the galaxy. Aims. The aim of this work is to study the spectroscopic and
kinematic properties of the host galaxy and the polar disk in the central
regions of NGC 4650A by disentangling their contributions to the observed
galaxy spectrum.
Methods. We applied the spectral decomposition technique introduced in
previous works to long-slit spectroscopic observations in the CaII triplet
region. We focused the analysis along the PA = 152 that corresponds to the
photometric minor axis of the host galaxy, where the superimposition of the two
components is more relevant and the spectral decomposition is necessary. We aim
to disentangle the stars that move in the equatorial plane of the host galaxy
from those that move in the meridan plane, which is along the polar disk.
Results. We successfully disentangled the spectra of the two structural
components of NGC 4650A and measured their line-of-sight velocity and velocity
dispersion profiles, and the stellar content along PA = 152. The host galaxy
shows significant rotation along its photometric minor axis, indicating that
the gravitational potential is not axisymmetric. The polar disk shows a
kinematic decoupling: the inner regions counter-rotating with respect the
outer-regions and the host spheroid. This suggests a complex formation history
for the polar disk, characterised by mass accretion with decoupled angular
momenta.Comment: Accepted for publication in Astronomy and Astrophysics. 7 pages, 5
figure
Characterization of ZnSe scintillating bolometers for Double Beta Decay
ZnSe scintillating bolometers are good candidates for future Double Beta
Decay searches, because of the 82Se high Q-value and thanks to the possibility
of alpha background rejection on the basis of the scintillation signal. In this
paper we report the characteristics and the anomalies observed in an extensive
study of these devices. Among them, an unexpected high emission from alpha
particles, accompanied with an unusual pattern of the light vs. heat scatter
plot. The perspectives for the application of this kind of detectors to search
for the Neutrinoless Double Beta Decay of 82Se are presented.Comment: 12 pages, 10 figure
CdWO4 scintillating bolometer for Double Beta Decay: Light and Heat anticorrelation, light yield and quenching factors
We report the performances of a 0.51 kg CdWO4 scintillating bolometer to be
used for future Double Beta Decay Experiments. The simultaneous read-out of the
heat and the scintillation light allows to discriminate between different
interacting particles aiming at the disentanglement and the reduction of
background contribution, key issue for next generation experiments. We will
describe the observed anticorrelation between the heat and the light signal and
we will show how this feature can be used in order to increase the energy
resolution of the bolometer over the entire energy spectrum, improving up to a
factor 2.6 on the 2615 keV line of 208Tl. The detector was tested in a 433 h
background measurement that permitted to estimate extremely low internal trace
contaminations of 232Th and 238U. The light yield of gamma/beta, alpha and
neutrons is presented. Furthermore we developed a method in order to correctly
evaluate the absolute thermal quenching factor of alpha particles in
scintillating bolometers.Comment: 8 pages 7 figure
Metallicity of the polar disk in NGC4650A: constraints for cold accretion scenario
We used high resolution spectra in the optical and near-infrared wavelength
range to study the abundance ratios and metallicities of the HII regions
associated with the polar disk in NGC4650A, in order to put constraints on the
formation of the polar disk through cold gas accretion along a filament; this
might be the most realistic way by which galaxies get their gas. We have
compared the measured metallicities for the polar structure in NGC4650A with
those of different morphological types and we have found that they are similar
to those of late-type galaxies: such results is consistent with a polar disk
formed by accretion from cosmic web filaments of external cold gas.Comment: Proceeding of the conference "Hunting for the Dark: The Hidden Side
of Galaxy Formation", Malta, 19-23 Oct. 200
Monte Carlo evaluation of the external gamma, neutron and muon induced background sources in the CUORE experiment
CUORE is a 1 ton scale cryogenic experiment aiming at the measurement of the
Majorana mass of the electron neutrino. The detector is an array of 988 TeO2
bolometers used for a calorimetric detection of the two electrons emitted in
the BB0n of 130Te. The sensitivity of the experiment to the lowest Majorana
mass is determined by the rate of background events that can mimic a BB0n. In
this paper we investigate the contribution of external sources i.e.
environmental gammas, neutrons and cosmic ray muons to the CUORE background and
show that the shielding setup designed for CUORE guarantees a reduction of this
external background down to a level <1.0E-02 c/keV/kg/y at the Q-value, as
required by the physical goal of the experiment.Comment: 14 pages, 7 figure
Diffuse light and galaxy interactions in the core of nearby clusters
The kinematics of the diffuse light in the densest regions of the nearby
clusters can be unmasked using the planetary nebulae (PNs) as probes of the
stellar motions. The position-velocity diagrams around the brightest cluster
galaxies (BCGs) identify the relative contributions from the outer halos and
the intracluster light (ICL), defined as the light radiated by the stars
floating in the cluster potential. The kinematics of the ICL can then be used
to asses the dynamical status of the nearby cluster cores and to infer their
formation histories. The cores of the Virgo and Coma are observed to be far
from equilibrium, with mergers currently on-going, while the ICL properties in
the Fornax and Hydra clusters show the presence of sub-components being
accreted in their cores, but superposed to an otherwise relaxed population of
stars. Finally the comparison of the observed ICL properties with those
predicted from Lambda-CDM simulations indicates a qualitative agreement and
provides insights on the ICL formation. Both observations and simulations
indicate that BCG halos and ICL are physically distinct components, with the
``hotter" ICL dominating at large radial distances from the BCGs halos as the
latter become progressively fainter.Comment: 14 pages, 5 figures. Invited review to appear in the proceedings of
"Galaxies and their masks" eds. Block, D.L., Freeman, K.C. and Puerari, I.,
2010, Springer (New York
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