4,150 research outputs found
The TNG Near Infrared Camera Spectrometer
NICS (acronym for Near Infrared Camera Spectrometer) is the near-infrared
cooled camera-spectrometer that has been developed by the Arcetri Infrared
Group at the Arcetri Astrophysical Observatory, in collaboration with the
CAISMI-CNR for the TNG (the Italian National Telescope Galileo at La Palma,
Canary Islands, Spain).
As NICS is in its scientific commissioning phase, we report its observing
capabilities in the near-infrared bands at the TNG, along with the measured
performance and the limiting magnitudes. We also describe some technical
details of the project, such as cryogenics, mechanics, and the system which
executes data acquisition and control, along with the related software.Comment: 7 pages, 5 figures, compiled with A&A macros. A&A in pres
The connection between the peaks in velocity dispersion and star-forming clumps of turbulent galaxies
We present Keck/OSIRIS adaptive optics observations with 150-400 pc spatial
sampling of 7 turbulent, clumpy disc galaxies from the DYNAMO sample
(). DYNAMO galaxies have previously been shown to be well matched
in properties to main sequence galaxies at . Integral field
spectroscopy observations using adaptive optics are subject to a number of
systematics including a variable PSF and spatial sampling, which we account for
in our analysis. We present gas velocity dispersion maps corrected for these
effects, and confirm that DYNAMO galaxies do have high gas velocity dispersion
(\kms), even at high spatial sampling. We find statistically
significant structure in 6 out of 7 galaxies. The most common distance between
the peaks in velocity dispersion and emission line peaks is ~kpc, we
note this is very similar to the average size of a clump measured with HST
H maps. This could suggest that the peaks in velocity dispersion in
clumpy galaxies likely arise due to some interaction between the clump and the
surrounding ISM of the galaxy, though our observations cannot distinguish
between outflows, inflows or velocity shear. Observations covering a wider area
of the galaxies will be needed to confirm this result.Comment: Accepted for publication in MNRA
GPCALMA: a Grid Approach to Mammographic Screening
The next generation of High Energy Physics experiments requires a GRID
approach to a distributed computing system and the associated data management:
the key concept is the "Virtual Organisation" (VO), a group of geographycally
distributed users with a common goal and the will to share their resources. A
similar approach is being applied to a group of Hospitals which joined the
GPCALMA project (Grid Platform for Computer Assisted Library for MAmmography),
which will allow common screening programs for early diagnosis of breast and,
in the future, lung cancer. HEP techniques come into play in writing the
application code, which makes use of neural networks for the image analysis and
shows performances similar to radiologists in the diagnosis. GRID technologies
will allow remote image analysis and interactive online diagnosis, with a
relevant reduction of the delays presently associated to screening programs.Comment: 4 pages, 3 figures; to appear in the Proceedings of Frontier
Detectors For Frontier Physics, 9th Pisa Meeting on Advanced Detectors, 25-31
May 2003, La Biodola, Isola d'Elba, Ital
Ethylene-propene copolymerization. Monomer reactivity and reaction mechanism
The relative reactivity of ethylene and propene in the first insertion steps of Ziegler-Natta copolymerization has been evaluated by analyzing via 13CNMR the %enriched end groups of copolymer fractionsofdifferentstereoregularity. Somepossibleinferencesconcerningreactionmechanismarereported
AGN Black Hole Masses and Bolometric Luminosities
Black hole mass, along with mass accretion rate, is a fundamental property of
active galactic nuclei. Black hole mass sets an approximate upper limit to AGN
energetics via the Eddington limit. We collect and compare all AGN black hole
mass estimates from the literature; these 177 masses are mostly based on the
virial assumption for the broad emission lines, with the broad-line region size
determined from either reverberation mapping or optical luminosity. We
introduce 200 additional black hole mass estimates based on properties of the
host galaxy bulges, using either the observed stellar velocity dispersion or
using the fundamental plane relation to infer ; these methods assume
that AGN hosts are normal galaxies. We compare 36 cases for which black hole
mass has been generated by different methods and find, for individual objects,
a scatter as high as a couple of orders of magnitude. The less direct the
method, the larger the discrepancy with other estimates, probably due to the
large scatter in the underlying correlations assumed. Using published fluxes,
we calculate bolometric luminosities for 234 AGNs and investigate the relation
between black hole mass and luminosity. In contrast to other studies, we find
no significant correlation of black hole mass with luminosity, other than those
induced by circular reasoning in the estimation of black hole mass. The
Eddington limit defines an approximate upper envelope to the distribution of
luminosities, but the lower envelope depends entirely on the sample of AGN
included. For any given black hole mass, there is a range in Eddington ratio of
up to three orders of magnitude.Comment: 43 pages with 10 figures. Accepted for publication in Ap
2-d Zo Crs Stack By Considering An Acquisition Line With Smooth Topography
The land seismic data suffers from effects due to the near surface irregularities and the existence of topography, For obtaining a high resolution seismic image, these effects should be corrected by using seismic processing techniques, e.g. field and residual static corrections. The Common-Reflection- Surface (CRS) stack method is a new processing technique to simulate zero-offset (ZO) seismic sections from multi-coverage seismic data. It is based on a second-order hyperbolic paraxial traveltime approximation referred to a central normal ray. By considering a planar measurement surface, the CRS stacking operator is defined by means of three parameters, namely the emergence angle of the normal ray, the curvature of the normal incidence point (NIP) wave, and the curvature of the normal (N) wave. In this paper the 2-D ZO CRS stack method is modified in order to consider effects due to the smooth topography. By means of this new CRS formalism, we obtain a high resolution ZO seismic section, without applying static corrections. As by-products the 2-D ZO CRS stack method we estimate at each point of the ZO seismic section the three relevant parameters associated to the CRS stack process. © 2005 Sociedade Brasileira de GeofĂsica.2311525BARD, B., (1974) Nonlinear parameter estimation, , Academic PressBIRGIN, E., BILOTI, R., TYGEL, M., SANTOS, L.T., Restricted optimization: A clue to a fast and accurate implementation of the common reflection surface stack (1999) Journal of Applied Geophysics, 42, pp. 143-155ÄERVENĂ, V., PSENSIK, I., (1988) Ray tracing program, , Charles University, CzechoslovakiaCHIRA, P., (2003) Empilhamento pelo mĂ©todo SuperfĂcie, , de ReflexĂŁo Comum 2-D com topografia e introdução ao caso 3-D, Ph.D. thesis, Federal University of Para, BrazilCHIRA-OLIVA, P., HUBRAL, P., Traveltime formulas of near-zero-offset primary reflections for a curved 2-D measurement surface (2003) Geophysics, 68 (1), pp. 255-261CHIRA-OLIVA, P., TYGEL, M., ZHANG, Y., HUBRAL, P., Analytic CRS stack formula for a 2D curved measurement surface and finite-offset reflections (2001) Journal of Seismic Exploration, 10, pp. 245-262GARABITO, G., CRUZ, J.C., HUBRAL, P., COSTA, J., Common Reflection Surface Stack: A new parameter search strategy by global optimization, 71th, SEG Mtg (2001) Expanded Abstracts, , San Antonio, Texas,USAGILL, P.E., MURRAY, W., WRIGHT, M.H., (1981) Practical optimization, , Academic PressGUO, N., FAGIN, S., Becoming effective velocity-model builders and depth imagers, part 2 - the basics of velocity-model building, examples and discussions Multifocusing (2002) The Leading Edge, pp. 1210-1216HUBRAL, P., Computing true amplitude reflections in a laterally inhomogeneous earth (1983) Geophysics, 48, pp. 1051-1062MANN, J., JĂGER, R., MĂLLER, T., HĂCHT, G., HUBRAL, P., Common-reflection-surface stack - A real data example (1999) Journal of Applied Geophysics, 42, pp. 301-318MĂLLER, T., (1999) The common reflection surface stack method - seismic imaging without explicit knowledge of the velocity model, , Ph.D. Thesis, University of Karlsruhe, GermanySEN, M., STOFFA, P., (1995) Global optimization methods in geophysical inversion, , Elsevier, Science Publ. CoZHANG, Y., HĂCHT, G., HUBRAL, P., 2D and 3D ZO CRS stack for a complex top-surface topography, Expanded (2002) 64th EAGE Conference and Technical Exhibition, , Abstract of th
Stellar and gaseous abundances in M82
The near infrared (IR) absorption spectra of starburst galaxies show several
atomic and molecular lines from red supergiants which can be used to infer
reliable stellar abundances. The metals locked in stars give a picture of the
galaxy metallicity prior to the last burst of star formation. The enrichment of
the new generation of stars born in the last burst can be traced by measuring
the hot gas in the X-rays. For the first time detailed stellar abundances in
the nuclear region of the starburst galaxy M82 have been obtained. They are
compared with those of the hot gas as derived from an accurate re-analysis of
the XMM and Chandra nuclear X-ray spectra. The cool stars and the hot gas
suggest [Fe/H]=-0.35+/-0.2 dex, and an overall [Si,Mg/Fe] enhancement by 0.4
and 0.5 dex, respectively. This is consistent with a major chemical enrichment
by SNe II explosions in recursive bursts on short timescales. Oxygen is more
puzzling to interpret since it is enhanced by 0.3 dex in stars and depleted by
0.2 dex in the hot gas. None of the standard enrichment scenarios can fully
explain such a behavior when compared with the other alpha-elements.Comment: APJ, in pres
The Nuclear Stellar Cluster in the Seyfert~1 Galaxy NGC 3227: High Angular Resolution NIR Imaging and Spectroscopy
NIR high angular resolution speckle imaging and imaging spectroscopy of the
nuclear region (10'' ~ 840pc) of the Seyfert1 galaxy NGC3227 are presented. A
nuclear stellar cluster is slightly resolved in the J and H band with
increasing contribution to the NIR continuum from the K to the J band. The
stellar absorption lines are extended compared to the neighboring continuum
suggesting a cluster size of ~ 70pc FWHM. Analysis of those lines suggests that
the stars are contributing about 65% (40%) of the total continuum emission in
the H (K) band in a 3.6'' aperture. Population synthesis in conjunction with
NIR spectral synthesis indicates an age of 25 to 50 Myr when red supergiants
contribute most to the NIR light. This is supported by published optical data
on the MgIb line and the CaII triplet. Although a higher age of ~ 0.5 Gyr where
AGB stars dominate the NIR light can not be excluded, the observed parameters
are at the limit of those expected for a cluster dominated by AGB stars.
However, in either case the resolved stellar cluster contributes only about ~
15 % of the total dynamical mass in the inner 300pc implying another much older
stellar population. Pure constant star formation over the last 10 Gyr can be
excluded. Therefore, at least two star formation/starburst events took place in
the nucleus of NGC3227. Since such sequences in the nuclear star formation
history are also observed in the nuclei of other galaxies a link between the
activity of the star formation and the AGN itself seems likely.Comment: accepted for publication in the Astrophysical Journal, 46 pages, 15
figure
Four physics jars
Experimental activities have a crucial role in physics education, because they represent one of the methods peculiar to discipline and facilitate the connection between experience and interpretation. They acquire particular significance if related and linked to every day experience. In this context we propose a reasoned sequence of experiences based on easy found and low-cost materials,
suitable to shed light on essential concepts connected to a variety of physics fields. All illustrated four didactic proposals are carried out by using tinplate jars and each one drives at an integrated balancing between formal and informal education by scheduling various teaching methodologies in order to engage students having different learning styles
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