4,498 research outputs found
The Universality of the Fundamental Plane of E and S0 Galaxies. Spectroscopic data
We present here central velocity dispersion measurements for 325 early-type
galaxies in eight clusters and groups of galaxies, including new observations
for 212 galaxies. The clusters and groups are the A262, A1367, Coma (A1656),
A2634, Cancer and Pegasus clusters, and the NGC 383 and NGC 507 groups. The new
measurements were derived from medium dispersion spectra, that cover 600 A
centered on the Mg Ib triplet at lambda ~ 5175. Velocity dispersions were
measured using the Tonry & Davis cross-correlation method, with a typical
accuracy of 6%. A detailed comparison with other data sources is made.Comment: 12 pages, 5 tables, 3 figures, to appear in AJ. Note that tables 2
and 3 are in separate files, as they should be printed in landscape forma
Structure of the SMC - Stellar component distribution from 2MASS data
The spatial distribution of the SMC stellar component is investigated from
2MASS data. The morphology of the different age populations is presented. The
center of the distribution is calculated and compared with previous
estimations. The rotation of the stellar content and possible consequence of
dark matter presence are discussed. The different stellar populations are
identified through a CMD diagram of the 2MASS data. Isopleth contour maps are
produced in every case, to reveal the spatial distribution. The derived density
profiles are discussed. The older stellar population follows an exponential
profile at projected diameters of about 5 kpc (~5 deg) for the major axis and
~4 kpc for the minor axis, centred at RA: 0h:51min, Dec: -73deg 7' (J2000.0).
The centre coordinates are found the same for all the different age population
maps and are in good accordance with the kinematical centre of the SMC. However
they are found considerably different from the coordinates of the centre of the
gas distribution. The fact that the older population found on an exponential
disk, gives evidence that the stellar content is rotating, with a possible
consequence of dark matter presence. The strong interactions between the MCs
and the MilkyWay might explain the difference in the distributions of the
stellar and gas components. The lack in the observed velocity element, that
implies absence of rotation, and contradicts with the consequences of
exponential profile of the stellar component, may also be a result of the
gravitational interactions.Comment: 7 Pages, 6 figures, accepted for publication in A&
Influence of Rat Strain and Arthritogen on Actions of Gold Drugs in Adjuvant-Induced Polyarthritis
The article examines the effects of aurothiomalate (ATM) and auranofin (AF) on adjuvant-induced polyarthritis and serum gold levels in three different strains of rats
Information and Communication Technology (ICT) and International Business Travel: Mobility Allies?
Like forecasts about the paperless office, technological solutions to the problem of international business travel continue to be deferred. As with the increased use of office paper, international business travel is defying predictions of its decline. There is growing evidence to suggest that business sectors which seem ideally placed to substitute information and communication technology (ICT) for travel, are actually generating more physical travel than other sectors. This paper develops a case study of the Irish software industry to exemplify why international travel is not diminishing in importance how and the ICT and business travel relationship is changing in this sector. The paper presents research findings that suggest that a cycle of substitution, generation and modification relationships have occurred as mobility interdependencies have developed.Peer Reviewe
The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA.
These targets are drawn from a larger sample of systems that were not uniquely
identified with optical counterparts during ALFALFA processing, and as such
have unusually high HI mass to light ratios. These candidate "Almost Dark"
objects fall into 4 categories: 1) objects with nearby HI neighbors that are
likely of tidal origin; 2) objects that appear to be part of a system of
multiple HI sources, but which may not be tidal in origin; 3) objects isolated
from nearby ALFALFA HI detections, but located near a gas-poor early-type
galaxy; 4) apparently isolated sources, with no object of coincident redshift
within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts
in the .40 database (Haynes et al. 2011) fall into category 1. This
pilot sample contains the first five sources observed as part of a larger
effort to characterize HI sources with no readily identifiable optical
counterpart at single dish resolution. These objects span a range of HI mass
[7.41 < log(M) < 9.51] and HI mass to B-band luminosity ratios (3 <
M/L < 9). We compare the HI total intensity and velocity
fields to SDSS optical imaging and to archival GALEX UV imaging. Four of the
sources with uncertain or no optical counterpart in the ALFALFA data are
identified with low surface brightness optical counterparts in SDSS imaging
when compared with VLA HI intensity maps, and appear to be galaxies with clear
signs of ordered rotation. One source (AGC 208602) is likely tidal in nature.
We find no "dark galaxies" in this limited sample. The present observations
reveal complex sources with suppressed star formation, highlighting both the
observational difficulties and the necessity of synthesis follow-up
observations to understand these extreme objects. (abridged)Comment: Astronomical Journal, in pres
Explosive Particle Dispersion in Plasma Turbulence
Particle dynamics are investigated in plasma turbulence, using
self-consistent kinetic simulations, in two dimensions. In steady state, the
trajectories of single protons and proton-pairs are studied, at different
values of plasma "beta" (ratio between kinetic and magnetic pressure). For
single-particle displacements, results are consistent with fluids and magnetic
field line dynamics, where particles undergo normal diffusion for very long
times, with higher "beta" being more diffusive. In an intermediate time range,
with separations lying in the inertial range, particles experience an explosive
dispersion in time, consistent with the Richardson prediction. These results,
obtained for the first time with a self-consistent kinetic model, are relevant
for astrophysical and laboratory plasmas, where turbulence is crucial for
heating, mixing and acceleration processes
Health-related quality of life and psychological distress do not return to population norms 12 months after joint replacement surgery (JRS)
New Observations of Extra-Disk Molecular Gas in Interacting Galaxy Systems, Including a Two-Component System in Stephan's Quintet
We present new CO (1 - 0) observations of eleven extragalactic tails and
bridges in nine interacting galaxy systems, almost doubling the number of such
features with sensitive CO measurements. Eight of these eleven features were
undetected in CO to very low CO/HI limits, with the most extreme case being the
NGC 7714/5 bridge. This bridge contains luminous H II regions and has a very
high HI column density (1.6 X 10^21 cm^-2 in the 55" CO beam), yet was
undetected in CO to rms T(R)* = 2.4 mK. The HI column density is higher than
standard H2 and CO self-shielding limits for solar-metallicity gas, suggesting
that the gas in this bridge is metal-poor and has an enhanced N(H2)/I(CO) ratio
compared to the Galactic value. Only one of the eleven features in our sample
was unambiguously detected in CO, a luminous HI-rich star formation region near
an optical tail in the compact group Stephan's Quintet. We detect CO at two
widely separated velocities in this feature, at ~6000 km/s and ~6700 km/s. Both
of these components have HI and H-alpha counterparts. These velocities
correspond to those of galaxies in the group, suggesting that this gas is
material that has been removed from two galaxies in the group. The
CO/HI/H-alpha ratios for both components are similar to global values for
spiral galaxies.Comment: 39 pages, Latex, 15 figures, Astronomical Journal, in pres
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