75 research outputs found
Signatures of Galaxy-Cluster Interactions: Spiral Galaxy Rotation Curve Asymmetry, Shape, and Extent
The environmental dependencies of the characteristics of spiral galaxy
rotation curves are studied in this work. We use our large, homogeneously
collected sample of 510 cluster spiral galaxy rotation curves to test the claim
that the shape of a galaxy's rotation curve strongly depends on its location
within the cluster, and thus presumably on the strength of the local
intracluster medium and on the frequency and strength of tidal interactions
with the cluster and cluster galaxies. Our data do not corroborate such a
scenario, consistent with the fact that Tully-Fisher residuals are independent
of galaxy location within the cluster; while the average late-type spiral
galaxy shows more rise in the outer parts of its rotation curve than does the
typical early-type spiral galaxy, there is no apparent trend for either subset
with cluster environment. We also investigate as a function of cluster
environment rotation curve asymmetry and the radial distribution of H II region
tracers within galactic disks. Mild trends with projected cluster-centric
distance are observed: (i) the (normalized) radial extent of optical line
emission averaged over all spiral galaxy types shows a 4%+/-2% increase per Mpc
of galaxy-cluster core separation, and (ii) rotation curve asymmetry falls by a
factor of two between the inner and outer cluster for early-type spirals (a
negligible decrease is found for late-type spirals). Such trends are consistent
with spiral disk perturbations or even the stripping of the diffuse, outermost
gaseous regions within the disks as galaxies pass through the dense cluster
cores.Comment: 17 pages; to appear in the April 2001 Astronomical Journa
Seeking the Local Convergence Depth. V. Tully-Fisher Peculiar Velocities for 52 Abell Clusters
We have obtained I band Tully-Fisher (TF) measurements for 522 late-type
galaxies in the fields of 52 rich Abell clusters distributed throughout the sky
between 50 and 200\h Mpc. Here we estimate corrections to the data for various
forms of observational bias, most notably Malmquist and cluster population
incompleteness bias. The bias-corrected data are applied to the construction of
an I band TF template, resulting in a relation with a dispersion of 0.38
magnitudes and a kinematical zero-point accurate to 0.02 magnitudes. This
represents the most accurate TF template relation currently available.
Individual cluster TF relations are referred to the average template relation
to compute cluster peculiar motions. The line-of-sight dispersion in the
peculiar motions is 341+/-93 km/s, in general agreement with that found for the
cluster sample of Giovanelli and coworkers.Comment: 31 pages, 14 figures, uses AAS LaTeX; to appear in the Astronomical
Journa
Gemini and Chandra observations of Abell 586, a relaxed strong-lensing cluster
We analyze the mass content of the massive strong-lensing cluster Abell 586
(). We use optical data (imaging and spectroscopy) obtained with the
Gemini Multi-Object Spectrograph (GMOS) mounted on the 8-m Gemini-North
telescope, together with publicly available X-ray data taken with the
\textit{Chandra} space telescope. Employing different techniques -- velocity
distribution of galaxies, weak gravitational lensing, and X-ray spatially
resolved spectroscopy -- we derive mass and velocity dispersion estimates from
each of them. All estimates agree well with each other, within a 68% confidence
level, indicating a velocity dispersion of 1000 -- 1250 \kms. The projected
mass distributions obtained through weak-lensing and X-ray emission are
strikingly similar, having nearly circular geometry. We suggest that Abell 586
is probably a truly relaxed cluster, whose last major merger occurred more than
Gyr agoComment: ApJ accepted, 20 pages, 11 figures; Figure 1 fixe
Overuse of health care in the emergency services in Chile
Indexación ScopusThe Public Health Service in Chile consists of different levels of complexity and coverage depending on the severity and degree of specialization of the pathology to be treated. From primary to tertiary care, tertiary care is highly complex and has low coverage. This work focuses on an analysis of the public health system with emphasis on the healthcare network and tertiary care, whose objectives are designed to respond to the needs of each patient. A review of the literature and a field study of the problem of studying the perception of internal and external users is presented. This study intends to be a contribution in the detection of opportunities for the relevant actors and the processes involved through the performance of Triage. The main causes and limitations of the excessive use of emergency services in Chile are analyzed and concrete proposals are generated aiming to benefit clinical care in emergency services. Finally, improvements related to management are proposed and the main aspects are determined to improve decision-making in hospitals, which could be a contribution to public health policies. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.https://www.mdpi.com/1660-4601/18/6/308
The Age-Redshift Relation for Standard Cosmology
We present compact, analytic expressions for the age-redshift relation
for standard Friedmann-Lema\^ \itre-Robertson-Walker (FLRW)
cosmology. The new expressions are given in terms of incomplete Legendre
elliptic integrals and evaluate much faster than by direct numerical
integration.Comment: 13 pages, 3 figure
Discovery of a cluster of galaxies behind the Milky Way: X-ray and optical observations
We report the discovery of Cl 2334+48, a rich cluster of galaxies in the Zone
of Avoidance, identified in public images from the XMM-Newton archive. We
present the main properties of this cluster using the XMM-Newton X-ray data,
along with new optical spectroscopic and photometric observations. Cl 2334+48
is located at z = 0.271 +/- 0.001, as derived from the optical spectrum of the
brightest member galaxy. Such redshift agrees with a determination from the
X-ray spectrum (z = 0.263 (+0.012/-0.010)), in which an intense emission line
is matched to the rest wavelength of the Fe Kalpha complex. Its intracluster
medium has a plasma temperature of 4.92 (+0.50/-0.48) keV, sub-solar abundance
(0.38 +/- 0.12 Zsun), and a bolometric luminosity of 3.2 x 10^44 erg/s. A
density contrast delta = 2500 is obtained in a radius of 0.5 Mpc/h70, and the
corresponding enclosed mass is 1.5 x 10^14 Msun. Optical images show an
enhancement of g'-i' > 2.5 galaxies around the central galaxy, as expected if
these were cluster members. The central object is a luminous E-type galaxy,
which is displaced ~ 40 kpc/h70 from the cluster X-ray center. In addition, it
has a neighbouring arc-like feature (~ 22" or 90 kpc/h70 from it), probably due
to strong gravitational lensing. The discovery of Cl 2334+48 emphasises the
remarkable capability of the XMM-Newton to reveal new clusters of galaxies in
the Zone of Avoidance.Comment: 9 pages, 11 figures, Accepted for publication in A&A (on July 12,
2006
The Double Infared Source Toward the Soft Gamma-Ray Repeater SGR 1900+14
We report the results of an extensive set of optical and near-infrared photometry and spectroscopy of the double infrared source reported by Hartmann et al. (1995) as a potential counterpart for the Galatic soft gamma-ray repeater SGR 1900 + 14. These objects are found to be variable but otherwise normal M5 supergiant stars at a distance of ~ 12-15 kpc and extinguised by Av ~ 19.2 mag, primarily by the general interstellar medium. We argue that the supergiants are likely gravitationally bround. These stars are positionally coincident with both quiescent X-ray and IRAS sources, suggestive of a yet-undetected third component to the system which may be responsible for the SGR
Physical properties of two low-luminosity z ~ 1.9 galaxies behind the lensing cluster AC 114
We present VLT/ISAAC near-infrared spectroscopy of two gravitationally-lensed
z ~ 1.9 galaxies, A2 and S2, located behind the cluster AC 114. Thanks to large
magnification factors, we have been successful in detecting rest-frame optical
emission lines in star-forming galaxies 1 to 2 magnitudes fainter than in
previous studies of Lyman break galaxies (LBGs) at z ~ 3. From the Ha
luminosity, we estimate star formation rates (SFRs) which are 7 to 15 times
higher than those inferred from the UV continuum flux at 1500 ang without dust
extinction correction. The behavior of S2 and A2 in terms of O/H and N/O
abundance ratios are very different, and they are also different from typical
LBGs at z ~ 3. S2 is a low-metallicity object (Z ~ 0.03 Zsun) with a low N/O
ratio, similar to those derived in the most metal-poor nearby HII galaxies. In
contrast, A2 is a high-metallicity galaxy (Z ~ 1.3 Zsun) with a high N/O
abundance ratio, similar to those derived in the most metal-rich starburst
nucleus galaxies. The virial masses, derived from emission-line widths, are 0.5
and 2.4 x 10^10 Msun, for S2 and A2 respectively. Thanks to the gravitational
amplification, the line profiles of S2 are spatially resolved, leading to a
velocity gradient of +- 240 km/s, which yields a dynamical mass of ~ 1.3 x
10^10 Msun within the inner 1 kpc radius. Combining these new data with the
sample of LBGs at z ~ 3, we conclude that these three galaxies exhibit
different physical properties in terms of SFRs, abundance and mass-to-light
ratios, and reddening. High-redshift galaxies of different luminosities could
thus have quite different star formation histories (abridged version).Comment: 11 pages, 8 figures. Accepted for publication in A&
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