317 research outputs found
Galaxy transmutations: The double ringed galaxy ESO 474-G26
Surface photometry and a 21cm HI line spectrum of the giant double-ringed
galaxy ESO 474-G26 are presented. The morphology of this system is unique among
the 30,000 galaxies with >B15. Two almost orthogonal optical rings with
diameters of 60 and 40 kpc surround the central body (assuming H0=70 km/s/Mpc).
The outer one is an equatorial ring, while the inner ring lies in a nearly
polar plane. The rings have blue optical colors typical of late-type spirals.
Both appear to be rotating around the central galaxy, so that this system can
be considered as a kinematically confirmed polar ring galaxy. Its observational
characteristics are typical of galaxy merger remnants. Although the central
object has a surface brightness distribution typical of elliptical galaxies, it
has a higher surface brightness for its effective radius than ordinary
ellipticals. Possible origins of this galaxy are discussed and numerical
simulations are presented that illustrate the formation of the two rings in the
merging process of two spiral galaxies, in which the observed appearance of ESO
474-G26 appears to be a transient stage.Comment: Accepted for publication in A&
The origin of polar ring galaxies: evidence for galaxy formation by cold accretion
Polar ring galaxies are flattened stellar systems with an extended ring of
gas and stars rotating in a plane almost perpendicular to the central galaxy.
We show that their formation can occur naturally in a hierarchical universe
where most low mass galaxies are assembled through the accretion of cold gas
infalling along megaparsec scale filamentary structures. Within a large
cosmological hydrodynamical simulation we find a system that closely resembles
the classic polar ring galaxy NGC 4650A. How galaxies acquire their gas is a
major uncertainty in models of galaxy formation and recent theoretical work has
argued that cold accretion plays a major role. This idea is supported by our
numerical simulations and the fact that polar ring galaxies are typically low
mass systems.Comment: 4 pages, 5 figures, stability of the ring discussed, minor changes to
match the accepted version by ApJL. A preprint with high-resolution figures
is available at http://krone.physik.unizh.ch/~andrea/PolarRing/PolarRing.p
Polar Ring Galaxies and the Tully Fisher relation: implications for the dark halo shape
We have investigated the Tully-Fisher relation for Polar Ring Galaxies
(PRGs), based on near infrared, optical and HI data available for a sample of
these peculiar objects. The total K-band luminosity, which mainly comes from
the central host galaxy, and the measured HI linewidth at 20% of the peak line
flux density, which traces the potential in the polar plane, place most polar
rings of the sample far from the Tully-Fisher relation defined for spiral
galaxies, with many PRGs showing larger HI linewidths than expected for the
observed K band luminosity. This result is confirmed by a larger sample of
objects, based on B-band data. This observational evidence may be related to
the dark halo shape and orientation in these systems, which we study by
numerical modeling of PRG formation and dynamics: the larger rotation
velocities observed in PRGs can be explained by a flattened polar halo, aligned
with the polar ring.Comment: 22 pages, 8 postscript figures, accepted for publication in
Astrophysical Journa
Formation of a polar-ring galaxy in a galaxy merger
We numerically investigate stellar and gas dynamics in star-forming and
dissipative galaxy mergers between two disk galaxies with specific orbital
configurations. We find that violent relaxation combined with gaseous
dissipation in galaxy merging transforms two disk galaxies into one S0 galaxy
with polar-rings: Both the central S0-like host and the polar-ring component in
a polar-ring galaxy are originally disk galaxies. We also find that morphology
of the developed polar-rings reflects both the initial orbit configuration of
galaxy merging and the initial mass ratio of the two merger progenitor disk
galaxies. Based upon these results, we discuss the origin of the fundamental
observational properties of polar-ring galaxies, such as the prevalence of S0
galaxies among polar-ring galaxies, the rarity of polar-ring galaxies among S0
galaxies, the dichotomy between narrow polar-rings and annular ones, shapes of
polar-ring warps, and an appreciably larger amount of interstellar gas in the
polar-ring component.Comment: 42 pages, 19 figures, ApJ in pres
A neutral hydrogen survey of polar ring galaxies IV. Parkes observations
A total of 33 polar ring galaxies and polar ring galaxy candidates were
observed in the 21-cm HI line with the 64-m Parkes radio telescope. The
objects, selected by their optical morphology, are all south of declination -39
degrees and in only 5 of them HI had been reported previously. HI line emission
was detected towards 18 objects, though in 3 cases the detection may be
confused by another galaxy in the telescope beam, and one is a marginal
detection. Eight objects were detected for the first time in HI, of which 5 did
not have previously known redshifts.Comment: Accepted by Astronomy and Astrophysics, 12/2/2002; new references
added on 20/2/200
Программное обеспечение для обучения в малых группах
This article focuses on the method of group training which represents one of the most actual and perspective forms of the organization of educational process. Authors confirm the theoretical conclusions with the experiment made with students of specialty "Information Systems and Technologies". Besides, article includes the description opportunities of the program adapted for work in small groups.В данной статье рассматривается метод группового обучения, который представляет собой одну из наиболее актуальных и перспективных форм организации учебного процесса. Авторы подтверждают свои теоретические выводы экспериментом, проведенным со студентами старших курсов специальности «Информационные системы и технологии». Кроме того, статья включает описание возможностей программы, адаптированной для выполнения общего задания в группах
Circulating markers of vascular damage as predictors of cardiovascular events in atherosclerosis and metabolic disorders
The article presents the results of cluster analysis of the contribution of immune inflammation and endothelial dysfunction (ED) markers to the frequency and severity of cardiovascular events (CVE) in cohorts of patients with asymptomatic atherosclerosis (AAS), coronary artery disease (CAD), type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS) during a 3-year prospective observation.
Results Circulating markers of ED and immune inflammation, such as ET-1, IL-1β, TNF-α, antibodies to collagen type I and III, and antibodies to chondroitine sulfate (CS) contribute to cardiovascular (CV) manifestation in AAS. In CAD patients ET-1, eNOs, antibodies to collagen, as well as IL-6 and vWf are the main contributors. In T2DM without clinical manifestation of CAD, the set of markers associated with the adverse events includes ET-1, eNOs, IL-6, anti-C, and anti-HA. In CAD combined with T2DM, the cluster of markers associated with the adverse events includes vWf, TNF-α, eNOs, IL-6, anti-C, anti-HA and CRP. In AAS without MS, the key contributors are ET-1 and vWf, and the presence of anti-C and anti-ChS; in AAS/MS patients, the key markers are IL-1β, TNF-α, anti-C, anti-ChS, anti-HA, and CRP. In CAD without MS, the cluster of markers associated with adverse events includes ET-1, eNOs and anti-HA; in CAD/MS it includes anti-C, ET-1, and IL-6.
Conclusion. The obtained results confirm the role of systemic inflammation in the development of atherosclerosis-associated angiopathy in coronary pathology and disorders of carbohydrate metabolism, and also suggest a set of circulating markers as predictors of adverse CVE
The Formation of Polar Disk Galaxies
Polar Ring Galaxies, such as NGC4650A, are a class of galaxy which have two
kinematically distinct components that are inclined by almost 90 degrees to
each other. These striking galaxies challenge our understanding of how galaxies
form; the origin of their distinct components has remained uncertain, and the
subject of much debate. We use high-resolution cosmological simulations of
galaxy formation to show that Polar Ring Galaxies are simply an extreme example
of the angular moment misalignment that occurs during the hierarchical
structure formation characteristic of Cold Dark Matter cosmology. In our model,
Polar Ring Galaxies form through the continuous accretion of gas whose angular
momentum is misaligned with the central galaxy.Comment: Submitted to ApJ. 8 pages in emulate ApJ style. 2 associated
animations are found at: http://www.youtube.com/watch?v=c-H3WzaewdY
http://www.youtube.com/watch?v=9Xf3fJkgWE
Near-Infrared photometry in the J, H and Kn bands for Polar Ring Galaxies: II. Global Properties
We discuss the properties of the host galaxy and ring light distributions in
the optical and near infrared bands for a sample of Polar Ring Galaxies (PRGs),
presented in Paper I (Iodice et al. 2002, Paper I). The goal of this work is to
test different formation scenarios for PRGs, proposed by different authors in
the last decades, by comparing their predictions with these new data. The
strategy is twofold: i) the integrated colors of the main components in these
systems are compared with those of standard morphological galaxy types, to
investigate whether differences in colors are caused by dust absorption or
difference in stellar populations. We then derived an estimate of the stellar
population ages in PRGs, which can be used to set constrains on the dynamical
modeling and the time evolution of these systems; ii) we analyse the structural
parameters of the host galaxy in order to understand whether this component is
a standard early-type system as its morphology suggests, and the light
distribution in the polar ring to measure its radial extension. These
observational results indicate that the global properties of PRGs are better
explained by dissipative merging of disks with un-equal masses as proposed by
Bekki (1998), rather than the accretion-or stripping-of gas by a pre-existing
early-type galaxy.Comment: 11 pages, 7 postscript figures, accepted for publication in A&
Intergalactic HII Regions Discovered in SINGG
A number of very small isolated HII regions have been discovered at projected
distances up to 30 kpc from their nearest galaxy. These HII regions appear as
tiny emission line objects in narrow band images obtained by the NOAO Survey
for Ionization in Neutral Gas Galaxies (SINGG). We present spectroscopic
confirmation of four isolated HII regions in two systems, both systems have
tidal HI features. The results are consistent with stars forming in interactive
debris due to cloud-cloud collisions. The H-alpha luminosities of the isolated
HII regions are equivalent to the ionizing flux of only a few O stars each.
They are most likely ionized by stars formed in situ, and represent atypical
star formation in the low density environment of the outer parts of galaxies. A
small but finite intergalactic star formation rate will enrich and ionize the
surrounding medium. In one system, NGC 1533, we calculate a star formation rate
of 1.5e-3 msun/yr, resulting in a metal enrichment of ~1e-3 solar for the
continuous formation of stars. Such systems may have been more common in the
past and a similar enrichment level is measured for the `metallicity floor' in
damped Lyman-alpha absorption systems.Comment: accepted for publication in the Astronomical Journal, 19 pages,
including 5 figures, some low resolution. Paper with high resolution images
can be downloaded from
http://astro.ph.unimelb.edu.au/~eryan/publications/eldots.ps.g
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