58,440 research outputs found
Cluster of galaxies around seven radio-loud QSOs at 1<z<1.6: K-band images
We have conducted a NIR study of the environments of seven radio-loud quasars
at redshifts 1<z<1.6. In present paper we describe deep band images
obtained for the fields of ~6X6 arcmin around the quasars with 3
limiting magnitudes of K~20.5. These fields were previously studied using deep
B and R band images (Sanchez & Gonzalez-Serrano 1999). Using together optical
and NIR data, it has been found a significant excess of galaxies which
optical-NIR colours, luminosity, spatial scale, and number of galaxies are
compatible with clusters at the redshift of the quasar.
We have selected a sample of cluster candidates analyzing the R-K vs. K
diagram. A ~25% of the candidates present red optical-NIR colours and an
ultraviolet excess. This population has been also found in clusters around
quasars at the same redshifts (Tanaka et al. 2000; Haines et al. 2001). These
galaxies seem to follow a mixed evolution: a main passive evolution plus late
starformation processes. The quasars do not inhabit the core of the clusters,
being found in the outer regions. This result agrees with the hypothesis that
the origin/feeding mechanism of the nuclear activity were merging processes.
The quasars inhabit the region were a collision is most probably to produce a
merger.Comment: 15 pages. A&A, accepted for publishin
SAOLIM, a prototype of a low cost System for Adaptive Optics with Lucky Imaging
A prototype of a low cost Adaptive Optics (AO) system has been developed at
the Instituto de Astrofisica de Andalucia (CSIC) and tested at the 2.2m
telescope of the Calar Alto observatory. We present here the status of the
project, which includes the image stabilization system and compensation of high
order wavefront aberrations with a membrane deformable mirror. The image
stabilization system consists of magnet driven tip-tilt mirror. The higher
order compensation system comprises of a Shack-Hartmann sensor, a membrane
deformable mirror with 39 actuators and the control computer that allows
operations up to 420Hz in closed loop mode. We have successfully closed the
high order AO loop on natural guide stars. An improvement of 4 times in terms
of FWHM was achieved. The description and the results obtained on the sky are
presented in this paper.Comment: Accepted for publishing in PASP, 11 pages, 14 figures, 6 table
Higgs Boson Masses in the MSSM with Heavy Majorana Neutrinos
We present a full diagrammatic computation of the one-loop corrections from
the neutrino/sneutrino sector to the renormalized neutral CP-even Higgs boson
self-energies and the lightest Higgs boson mass, Mh, within the context of the
so-called MSSM-seesaw scenario. This consists of the Minimal Supersymmetric
Standard Model with the addition of massive right handed Majorana neutrinos and
their supersymmetric partners, and where the seesaw mechanism is used for the
lightest neutrino mass generation. We explore the dependence on all the
parameters involved, with particular emphasis in the role played by the heavy
Majorana scale. We restrict ourselves to the case of one generation of
neutrinos/sneutrinos. For the numerical part of the study, we consider a very
wide range of values for all the parameters involved. We find sizeable
corrections to Mh, which are negative in the region where the Majorana scale is
large (10^{13}-10^{15} GeV) and the lightest neutrino mass is within a range
inspired by data (0.1-1 eV). For some regions of the MSSM-seesaw parameter
space, the corrections to Mh are substantially larger than the anticipated
Large Hadron Collider precision.Comment: Latex, 50 pages, 15 figures, 6 tables. Discussion improved. Comments
and some new approximate formulae have been added. Published version on JHE
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