1,635 research outputs found
Correlation length of X-ray brightest Abell clusters
We compute the cluster auto-correlation function of an X-ray
flux limited sample of Abell clusters (XBACs, \cite{ebe}). For the total XBACs
sample we find a power-law fit with Mpc
hand consistent with the results of Abell
clusters. We also analyze for subsamples defined by different
X-ray luminosity thresholds where we find a weak tendency of larger values of
with increasing X-ray luminosity although with a low statistical
significance. In the different subsamples analyzed we find Mpc
h and . Our analysis suggests that cluster X-ray
luminosities may be used for a reliable confrontation of cluster spatial
distribution properties in models and observations.Comment: Accepted for publication in Astrophysical Journa
Photometric validation of a model independent procedure to extract galaxy clusters
By means of CCD photometry in three bands (Gunn g, r, i) we investigate the
existence of 12 candidate clusters extracted via a model independent peak
finding algorithm (\cite{memsait}) from DPOSS data. The derived color-magnitude
diagrams allow us to confirm the physical nature of 9 of the cluster
candidates, and to estimate their photometric redshifts. Of the other
candidates, one is a fortuitous detection of a true cluster at z~0.4, one is a
false detection and the last is undecidable on the basis of the available data.
The accuracy of the photometric redshifts is tested on an additional sample of
8 clusters with known spectroscopic redshifts. Photometric redshifts turn out
to be accurate within z~0.01 (interquartile range).Comment: A&A in pres
Radio-optically selected clusters of galaxies. II. The cluster sample
We present a sample of 171 candidate groups and clusters of galaxies at
intermediate redshift over an area of ~550 square degrees at the South Galactic
Pole selected by using optically identified radio sources from the NRAO VLA Sky
Survey as tracers of dense environment. Out of these 171 candidates, 76 have a
counterpart in the literature while 95 of them are previously unknown clusters.
This paper presents the cluster selection technique, based on the search of
excesses in the optical surface density of galaxies near identified
radiogalaxies, and the first spectroscopic results aimed to confirm the
presence of a cluster. Spectroscopy for 11 candidates led to the detection of 9
clusters at redshift in the range 0.13 - 0.3, with estimated velocity
dispersions ranging from values typical of clusters to those of galaxy groups.
These results show that this technique represents a powerful tool for the
selection of homogeneous samples of intermediate redshift clusters over a wide
range of richness.Comment: 13 pages, 3 Postscript and 2 GIF figures. Accepted for publication in
A&
River Restoration in the Twenty-First Century: Data and Experiential Knowledge to Inform Future Efforts
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71999/1/j.1526-100X.2007.00243.x.pd
Successful use of axonal transport for drug delivery by synthetic molecular vehicles
We report the use of axonal transport to achieve intraneural drug delivery. We constructed a novel tripartite complex of an axonal transport facilitator conjugated to a linker molecule bearing up to a hundred reversibly attached drug molecules. The complex efficiently enters nerve terminals after intramuscular or intradermal administration and travels within axonal processes to neuron cell bodies. The tripartite agent provided 100-fold amplification of saturable neural uptake events, delivering multiple drug molecules per complex. _In vivo_, analgesic drug delivery to systemic and to non-targeted neural tissues was greatly reduced compared to existing routes of administration, thus exemplifying the possibility of specific nerve root targeting and effectively increasing the potency of the candidate drug gabapentin 300-fold relative to oral administration
Searching (the) FIRST radio arcs near ACO clusters
Gravitational lensing (GL) of distant radio sources by galaxy clusters should
produce radio arc(let)s. We extracted radio sources from the FIRST survey near
Abell cluster cores and found their radio position angles to be uniformly
distributed with respect to the cluster centres. This result holds even when we
restrict the sample to the richest or most centrally condensed clusters, and to
sources with high S/N and large axial ratio. Our failure to detect GL with
statistical methods may be due to poor cluster centre positions. We did not
find convincing candidates for arcs either. Our result agrees with theoretical
estimates predicting that surveys much deeper than FIRST are required to detect
the effect. This is in apparent conflict with the detection of such an effect
claimed by Bagchi & Kapahi (1995).Comment: 6 pages; 8 figures and 1 style file are included; to appear in Proc.
"Observational Cosmology with the New Radio Surveys", eds. M. Bremer, N.
Jackson & I. Perez-Fournon, Kluwer Acad. Pres
Radio-optically selected clusters of galaxies. I. The radiogalaxy sample
In order to study the status and the possible evolution of clusters of
galaxies at intermediate redshifts (z ~ 0.1 - 0.3), as well as their spatial
correlation and relationship with the local environment, we built a sample of
candidate groups and clusters of galaxies using radiogalaxies as tracers of
dense environments. This technique - complementary to purely optical or X-ray
cluster selection methods - represents an interesting tool for the selection of
clusters in a wide range of richness, so to make it possible to study the
global properties of groups and clusters of galaxies, such as their
morphological content, dynamical status and number density, as well as the
effect of the environment on the radio emission phenomena. In this paper we
describe the compilation of a catalogue of 16000 radio sources in the region of
the South Galactic Pole extracted from the publicly available NRAO VLA Sky
Survey maps, and the optical identification procedure with galaxies brighter
than b_J=20.0 in the EDSGC Catalogue. The radiogalaxy sample, valuable for the
study of radio source populations down to low flux levels, consists of 1288
identifications and has been used to detect candidate groups and clusters
associated to NVSS radio sources. In a companion paper we will discuss the
cluster detection method, the cluster sample as well as first spectroscopic
results.Comment: 15 pages, 6 Postscript and 1 GIF figures. Accepted for publication in
A&
Purification, N-terminal amino acid sequence and properties of hydroxymethylbilane synthase (porphobilinogen deaminase) from Escherichia coli
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