265 research outputs found
The Correspondence between Convergence Peaks from Weak Lensing and Massive Dark Matter Haloes
The convergence peaks, constructed from galaxy shape measurement in weak
lensing, is a powerful probe of cosmology as the peaks can be connected with
the underlined dark matter haloes. However the capability of convergence peak
statistic is affected by the noise in galaxy shape measurement, signal to noise
ratio as well as the contribution from the projected mass distribution from the
large-scale structures along the line of sight (LOS). In this paper we use the
ray-tracing simulation on a curved sky to investigate the correspondence
between the convergence peak and the dark matter haloes at the LOS. We find
that, in case of no noise and for source galaxies at , more than
peaks with (signal to noise ratio) are related to
more than one massive haloes with mass larger than .
Those massive haloes contribute to high peaks ()
with the remaining contributions are from the large-scale structures. On the
other hand, the peaks distribution is skewed by the noise in galaxy shape
measurement, especially for lower SNR peaks. In the noisy field where the shape
noise is modelled as a Gaussian distribution, about high peaks
() are true peaks and the fraction decreases to for
lower peaks (). Furthermore, we find that high peaks
() are dominated by very massive haloes larger than .Comment: 13 pages, 11 figures, 4 tables, accepted for publication in MNRAS.
Our mock galaxy catalog is available upon request by email to the author
([email protected]
Blue straggler evolution caught in the act in the Large Magellanic Cloud globular cluster Hodge 11
High-resolution {\sl Hubble Space Telescope} imaging observations show that
the radial distribution of the field-decontaminated sample of 162 'blue
straggler' stars (BSs) in the Gyr-old Large Magellanic
Cloud cluster Hodge 11 exhibits a clear bimodality. In combination with their
distinct loci in color--magnitude space, this offers new evidence in support of
theoretical expectations that suggest different BS formation channels as a
function of stellar density. In the cluster's color--magnitude diagram, the BSs
in the inner 15 (roughly corresponding to the cluster's core radius) are
located more closely to the theoretical sequence resulting from stellar
collisions, while those in the periphery (at radii between 85 and 100)
are preferentially found in the region expected to contain objects formed
through binary mass transfer or coalescence. In addition, the objects'
distribution in color--magntiude space provides us with the rare opportunity in
an extragalactic environment to quantify the evolution of the cluster's
collisionally induced BS population and the likely period that has elapsed
since their formation epoch, which we estimate to have occurred 4--5 Gyr
ago.Comment: 13 pages, 4 figure, accepted by Astrophysical Journal Letter
S-antigen specific T helper type 1 response is present in Behcet’s disease
PURPOSE: To investigate the frequency and phenotypic and functional characteristics of S-antigen (S-Ag) specific T cells in patients with Behcet's disease (BD). METHODS: Blood was taken from 23 active BD patients, 12 inactive BD patients, and 14 healthy controls. The clinical features of the patients were summarized. T cell response against 40 mixed S-Ag peptides was identified by interferon gamma (IFN-gamma) enzyme-linked immunospot assay (ELISPOT). CD69 and CD45RO were used to characterize the phenotype of S-Ag specific T cells. The functional property of S-Ag specific T cells was investigated by measuring the production of cytokines. RESULTS: Response to the mixed S-Ag peptides was found in 56.5% and 25% of active and inactive BD patients, respectively. The responsiveness to S-Ag peptides was unrelated to the clinical features of the patients. About 65.8% of IFN-gamma(+) CD4(+) T cells in active BD patients expressed CD69 and CD45RO concomitantly. S-Ag peptides significantly induced a production of IFN-gamma and tumor necrosis factor (TNF)-alpha but not interleukin (IL)-2, IL-4, and IL-17 by peripheral blood mononuclear cells (PBMCs) in active BD patients with a response to S-Ag. CONCLUSIONS: S-Ag specific T cells are present in certain active BD patients, and most of them are activated memory CD4(+) T cells. These T cells may be involved in the pathogenesis of BD via producing Th1-dominant cytokine
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