355 research outputs found
Gemini spectroscopy of the outer disk star cluster BH176
BH176 is an old metal-rich star cluster. It is spatially and kinematically
consistent with belonging to the Monoceros Ring. It is larger in size and more
distant from the Galactic plane than typical open clusters, and it does not
belong to the Galactic bulge. Our aim is to determine the origin of this unique
object by accurately determining its distance, metallicity, and age. The best
way to reach this goal is to combine spectroscopic and photometric methods. We
present medium-resolution observations of red clump and red giant branch stars
in BH176 obtained with the Gemini South Multi-Object Spectrograph.We derive
radial velocities, metallicities, effective temperatures, and surface gravities
of the observed stars and use these parameters to distinguish member stars from
field objects. We determine the following parameters for BH176:
km/s, , age Gyr, , distance
kpc, -element abundance dex (the
mean of [Mg/Fe], and [Ca/Fe]). BH176 is a member of old Galactic open clusters
that presumably belong to the thick disk. It may have originated as a massive
star cluster after the encounter of the forming thin disk with a high-velocity
gas cloud or as a satellite dwarf galaxy.Comment: 15 pages, 7 fufures, Accepted for publication in Astronomy &
Astrophysic
A G1-like globular cluster in NGC 1023
The structure of a very bright (MV = -10.9) globular cluster in NGC 1023 is
analyzed on two sets of images taken with the Hubble Space Telescope. From
careful modeling of King profile fits to the cluster image, a core radius of
0.55+/-0.1 pc, effective radius 3.7+/-0.3 pc and a central V-band surface
brightness of 12.9+/-0.5 mag / square arcsec are derived. This makes the
cluster much more compact than Omega Cen, but very similar to the brightest
globular cluster in M31, G1 = Mayall II. The cluster in NGC 1023 appears to be
very highly flattened with an ellipticity of about 0.37, even higher than for
Omega Cen and G1, and similar to the most flattened clusters in the Large
Magellanic Cloud.Comment: 14 pages, 3 figures, 1 table. Accepted for AJ, Oct 200
Survey of Canine Dirofilaria immitis Infection in New Caledonia
Canine dirofilariosis is a frequent parasitic disease in New-Caledonia. A survey of canine heartworm (Dirofilaria immitis) infection among dogs from the cities of Tontouta, Nandaï and Nouméa, was performed in March 2009 using two antigen test kits; the microwell ELISA test: DiroCHE (Synbiotics Europe) and the Rapid Immuno Migration (RIM) test: WITNESS DIROFILARIA (Synbiotics Europe). Blood samples were collected from 64 dogs: 49 strays and 15 military working dogs. The military dogs received a permanent chemoprophylaxis (moxidectin). In 11 stray dogs, both tests were positive (22.4%). All the military dogs were negative, showing efficiency of chemoprophaxis. Results were discrepant in 6 dogs, negative with one test and doubtful with the other. Antigen heartworm test kits are available and reliable diagnostic tools. They are useful to evaluate the efficiency of chemoprophylaxis and to detect infected animals in order to treat them and to prevent the spreading of the disease
Morphological classification and structural parameters for early-type galaxies in the Coma cluster
We present the results of an isophotal shape analysis of three samples of
galaxies in the Coma cluster. Quantitative morphology, together with structural
and photometric parameters, is given for each galaxy. Special emphasis has been
placed on the detailed classification of early-type galaxies.
The three samples are: i) a sample of 97 early-type galaxies brighter than
m = 17.00 falling within one degree from the center of the Coma cluster;
these galaxies were observed with CCD cameras, mostly in good to excellent
resolution conditions; ii) a magnitude complete sample of 107 galaxies of all
morphological types down to m = 17.00 falling in a circular region of 50
arcmin diameter, slightly offcentered to the North-West of the cluster center;
the images for this and the next sample come from digitized photographic
plates; iii) a complete comparison sample of 26 galaxies of all morphological
types down to m = 16.05 (or m 17.5), also in a region of 50
arcmin diameter, but centered 2.6 degrees West of the cluster center.
The reliability of our morphological classifications and structural
parameters of galaxies, down to the adopted magnitude limits, is assessed by
comparing the results on those galaxies for which we had images taken with
different instrumentation and/or seeing conditions, and by comparing our
results with similar data from other observers.Comment: 22 pages, including 4 figures and 4 tables, uuencoded, gzipped
postscrip
A CH star in the globular cluster NGC 6426
We report on the serendipitous discovery of a carbon star near the centre of
the low-metallicity globular cluster NGC 6426. We determined its membership and
chemical properties using medium-resolution spectra. The radial velocity of
-159 km/s makes it a member of the cluster. We used photometric data from the
literature and the COMARCS stellar atmospheric models to derive its luminosity,
effective temperature, surface gravity, metallicity, and approximate C, N, and
O abundance ratios. According to these properties, we suggest that this star is
a genuine carbon rich low-metallicity AGB star.Comment: 5 pages, accepted for publication in MNRA
The construction of non-spherical models of quasi-relaxed stellar systems
Spherical models of collisionless but quasi-relaxed stellar systems have long
been studied as a natural framework for the description of globular clusters.
Here we consider the construction of self-consistent models under the same
physical conditions, but including explicitly the ingredients that lead to
departures from spherical symmetry. In particular, we focus on the effects of
the tidal field associated with the hosting galaxy. We then take a stellar
system on a circular orbit inside a galaxy represented as a "frozen" external
field. The equilibrium distribution function is obtained from the one
describing the spherical case by replacing the energy integral with the
relevant Jacobi integral in the presence of the external tidal field. Then the
construction of the model requires the investigation of a singular perturbation
problem for an elliptic partial differential equation with a free boundary, for
which we provide a method of solution to any desired order, with explicit
solutions to two orders. We outline the relevant parameter space, thus opening
the way to a systematic study of the properties of a two-parameter family of
physically justified non-spherical models of quasi-relaxed stellar systems. The
general method developed here can also be used to construct models for which
the non-spherical shape is due to internal rotation. Eventually, the models
will be a useful tool to investigate whether the shapes of globular clusters
are primarily determined by internal rotation, by external tides, or by
pressure anisotropy.Comment: AASTeX v5.2, 37 pages with 2 figures, accepted for publication in The
Astrophysical Journa
Epidemiological study of canine trypanosomosis in an urban area of Ivory Coast
Following confirmed cases of trypanosomosis in military working dogs, c cross-sectional study was undertaken to evaluate the source of infection and determine the prevalence of canine infection with Trypanosoma congolense in the urban focus of Abidjan, Ivory Coast. Blood from 123 dogs were collected and subjected to PCR using specific primers for Trypanosoma congolense "forest type". In addition, an entomological study was conducted in an urban area near the forest surronding the military camp. The observed prevalence was 30.1% end PCR positivity to Trypanosoma congolense was not significantly associated with sex or age of animals. This study demonstrates the high contamination rate of dogs in enzootic zones, the potential risk of introduction of the disease in free animal populations and the ability of Glossina palpalis to adopt to urban areas and to transmit trypanosomosis in such areas. The factors leading to a possible emergence of canine trypanosomiasis in enzootic zones need further investigations
Accumulation of Immature Langerhans Cells in Human Lymph Nodes Draining Chronically Inflamed Skin
The coordinated migration and maturation of dendritic cells (DCs) such as intraepithelial Langerhans cells (LCs) is considered critical for T cell priming in response to inflammation in the periphery. However, little is known about the role of inflammatory mediators for LC maturation and recruitment to lymph nodes in vivo. Here we show in human dermatopathic lymphadenitis (DL), which features an expanded population of LCs in one draining lymph node associated with inflammatory lesions in its tributary skin area, that the Langerin/CD207+ LCs constitute a predominant population of immature DCs, which express CD1a, and CD68, but not CD83, CD86, and DC–lysosomal-associated membrane protein (LAMP)/CD208. Using LC-type cells generated in vitro in the presence of transforming growth factor (TGF)-β1, we further found that tumor necrosis factor (TNF)-α, as a prototype proinflammatory factor, and a variety of inflammatory stimuli and bacterial products, increase Langerin expression and Langerin dependent Birbeck granules formation in cell which nevertheless lack costimulatory molecules, DC–LAMP/CD208 and potent T cell stimulatory activity but express CCR7 and respond to the lymph node homing chemokines CCL19 and CCL21. This indicates that LC migration and maturation can be independently regulated events. We suggest that during DL, inflammatory stimuli in the skin increase the migration of LCs to the lymph node but without associated maturation. Immature LCs might regulate immune responses during chronic inflammation
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