11,187 research outputs found
Separating the conjoined red clump in the Galactic Bulge: Kinematics and Abundances
We have used the AAOMEGA spectrograph to obtain R spectra of 714
stars that are members of two red clumps in the Plaut Window Galactic bulge
field . We discern no difference between the clump
populations based on radial velocities or abundances measured from the Mg
index. The velocity dispersion has a strong trend with Mg-index metallicity,
in the sense of a declining velocity dispersion at higher metallicity. We also
find a strong trend in mean radial velocity with abundance. Our red clump
sample shows distinctly different kinematics for stars with [Fe/H] , which
may plausibly be attributable to a minority classical bulge or inner halo
population. The transition between the two groups is smooth. The
chemo-dynamical properties of our sample are reminiscent of those of the Milky
Way globular cluster system. If correct, this argues for no bulge/halo
dichotomy and a relatively rapid star formation history. Large surveys of the
composition and kinematics of the bulge clump and red giant branch are needed
to define further these trends.Comment: 5 pages, 4 figures, Accepted for Publication in the Astrophysical
Journal Letters Fixed typos, updated affiliations and added some references
upon reques
Position space versions of Magueijo-Smolin doubly special relativity proposal and the problem of total momentum
We present and discuss two different possibilities to construct position
space version for Magueijo-Smolin (MS) doubly special relativity proposal. The
first possibility is to start from ordinary special relativity and then to
define conserved momentum in special way. It generates MS invariant as well as
nonlinear MS transformations on the momentum space, leading to consistent
picture for one-particle sector of the theory. The second possibility is based
on the following observation. Besides the nonlinear MS transformations, the MS
energy-momentum relation is invariant also under some inhomogeneous linear
transformations. The latter are induced starting from linearly realized Lorentz
group in five-dimensional position space. Particle dynamics and kinematics are
formulated starting from the corresponding five-dimensional interval. There is
no problem of total momentum in the theory. The formulation admits two observer
independent scales, the speed of light, , and with dimension of
velocity. We speculate on different possibilities to relate with
fundamental constants. In particular, expression of in terms of vacuum
energy suggests emergence of (minimum) quantum of mass.Comment: Latex twice, 14 pages, revised in accordance with the version
publishedin Phys. Rev.
Deep spectroscopy of z~1 6C radio galaxies - II. Breaking the redshift-radio power degeneracy
The results of a spectroscopic analysis of 3CR and 6C radio galaxies at
redshift z~1 are contrasted with the properties of lower redshift radio
galaxies, chosen to be matched in radio luminosity to the 6C sources studied at
z~1, thus enabling the P-z degeneracy to be broken. Partial rank correlations
and principal component analysis have been used to determine which of z and P
are the critical parameters underlying the observed variation of the ionization
state andd kinematics of the emission line gas. [OII]/H-beta is shown to be a
useful ionization mechanism diagnostic. Statistical analysis of the data shows
that the ionization state of the emission line gas is strongly correlated with
radio power, once the effects of other parameters are removed. No dependence of
ionization state on z is observed, implying that the ionization state of the
emission line gas is solely a function of the AGN properties rather than the
hostt galaxy and/or environment. Statistical analysis of the kinematic
properties of the emission line gas shows that these are strongly correlated
independently withh both P and z. The correlation with redshift is the stronger
of the two, suggesting that host galaxy composition or environment may play a
role in producing the less extreme gas kinematics observed in the emission line
regions of low redshift galaxies. For both the ionization and kinematic
properties of thee galaxies, the independent correlations observed with radio
size are strongest. Radio source age is a determining factor for the extended
emission line regions.Comment: 10 pages, 5 figures, accepted for publication in MNRA
Effects of Rescattering in (e,e'p) Reactions within a Semiclassical Model
The contribution of rescattering to final state interactions in (e,e'p) cross
sections is studied for medium and high missing energies using a semiclassical
model. This approach considers two-step processes that lead to the emission of
both nucleons.
The effects of nuclear transparency are accounted for in a Glauber inspired
approach and the dispersion effects of the medium at low energies are included.
It is found that rescattering is strongly reduced in parallel kinematics.
At high missing energy and momenta, the distortion of the short-range
correlated tail of the spectral function is dominated by a rearrangement of
that strength itself. In perpendicular kinematics, a further enhancement of the
experimental yield is due to strength that is originally in the mean field
region.
This contribution becomes negligible at large missing momenta.Comment: 10 pages, 9 figures. Minor corrections: improved figures and few
comments adde
Probing the kinematics of early-type galaxy halos using planetary nebulae
We present first results of a study of the halo kinematics for a sample of
early type galaxies using planetary nebulae (PNe) as kinematical tracers. PNe
allow to extend up to several effective radii (Re) the information from
absorption line kinematics (confined to within 1 or 2 Re), providing valuable
information and constraints for merger simulations and galaxy formation models.
We find that the specific angular momentum per unit mass has a more complex
radial dependence when the halo region is taken into account and that the halo
velocity dispersion is related to the total galaxy luminosity, isophotal shape,
and number of PNe per unit of luminosityComment: 4 pages, 3 figures. refereed proceeding of the "Galactic and Stellar
Dynamics 2008" conference, Ed. C.M. Boily. To be published in AN, year: 2008,
vol: 329, Issue: 9-10, pages: 912-91
Top quark mass: Latest CDF results, Tevatron combination and electroweak implications
A summary of the most up-to-date top quark mass measurements at CDF is
presented. These analyses use top-antitop candidate events detected in the CDF
experiment at the Tevatron collider with an integrated luminosity of up to
~3/fb. The combination of all those measurements together with the
corresponding top mass measurements from the concurrently running D0 experiment
at the Tevatron yields a world average of M_t=[173.1+/-0.6(stat.)+/-1.1(syst.)]
GeV/c^2.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072
Dynamical models of NGC 3115
We present new dynamical models of the S0 galaxy N3115, making use of the
available published photometry and kinematics as well as of two-dimensional
TIGER spectrography. We first examined the kinematics in the central 40 arcsec
in the light of two integral f(E,J) models. Jeans equations were used to
constrain the mass to light ratio, and the central dark mass whose existence
was suggested by previous studies. The even part of the distribution function
was then retrieved via the Hunter & Qian formalism. We thus confirmed that the
velocity and dispersion profiles in the central region could be well fit with a
two-integral model, given the presence of a central dark mass of ~10^9 Msun.
However, no two integral model could fit the h_3 profile around a radius of 25
arcsec where the outer disc dominates the surface brightness distribution.
Three integral analytical models were therefore built using a Quadratic
Programming technique. These models showed that three integral components do
indeed provide a reasonable fit to the kinematics, including the higher
Gauss-Hermite moments. Again, models without a central dark mass failed to
reproduce the observed kinematics in the central arcseconds. This clearly
supports the presence of a nuclear black hole of at least 6.5 10^8 Msun in the
centre of NGC 3115. These models were finally used to estimate the importance
of the dark matter in the outer part of NGC 3115, suggested by the flat stellar
rotation curve observed by Capaccioli et al. (1993).Comment: 18 pages, 22 figures, accepted for publication in MNRA
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