1,254 research outputs found
Strong lens search in the ESO public Survey KiDS
We have started a systematic search of strong lens candidates in the ESO
public survey KiDS based on the visual inspection of massive galaxies in the
redshift range . As a pilot program we have inspected 100 sq. deg.,
which overlap with SDSS and where there are known lenses to use as a control
sample. Taking advantage of the superb image quality of VST/OmegaCAM, the
colour information and accurate model subtracted images, we have found 18 new
lens candidates, for which spectroscopic confirmation will be needed to confirm
their lensing nature and study the mass profile of the lensing galaxies.Comment: 4 pages, 1 figure, to appear on the refereed Proceeding of the "The
Universe of Digital Sky Surveys" conference held at the INAF--OAC, Naples, on
25th-28th november 2014, to be published on Astrophysics and Space Science
Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic
Luminous Satellites of Early-Type Galaxies I: Spatial Distribution
We study the spatial distribution of faint satellites of intermediate
redshift (0.1<z<0.8), early-type galaxies, selected from the GOODS fields. We
combine high resolution HST images and state-of-the-art host subtraction
techniques to detect satellites of unprecedented faintness and proximity to
intermediate redshift host galaxies (up to 5.5 magnitudes fainter and as close
as 0."5/2.5 kpc to the host centers). We model the spatial distribution of
objects near the hosts as a combination of an isotropic, homogenous
background/foreground population and a satellite population with a power law
radial profile and an elliptical angular distribution. We detect a significant
population of satellites, Ns =1.7 (+0.9,-0.8) that is comparable to the number
of Milky Way satellites with similar host-satellite contrast.The average
projected radial profile of the satellite distribution is isothermal, gamma_p=
-1.0(+0.3,-0.4), which is consistent with the observed central mass density
profile of massive early-type galaxies. Furthermore, the satellite distribution
is highly anisotropic (isotropy is ruled out at a >99.99% confidence level).
Defining phi to be the offset between the major axis of the satellite spatial
distribution and the major axis of the host light profile, we find a maximum
posterior probability of phi = 0 and |phi| less than 42 degrees at the 68%
confidence level. The alignment of the satellite distribution with the light of
the host is consistent with simulations, assuming that light traces mass for
the host galaxy as observed for lens galaxies. The anisotropy of the satellite
population enhances its ability to produce the flux ratio anomalies observed in
gravitationally lensed quasars.Comment: 21 pages, 16 figures, Accepted for publication in Ap
The SWELLS Survey. I. A large spectroscopically selected sample of edge-on late-type lens galaxies
The relative contribution of baryons and dark matter to the inner regions of
spiral galaxies provides critical clues to their formation and evolution, but
it is generally difficult to determine. For spiral galaxies that are strong
gravitational lenses, however, the combination of lensing and kinematic
observations can be used to break the disk-halo degeneracy. In turn, such data
constrain fundamental parameters such as i) the mass density profile slope and
axis ratio of the dark matter halo, and by comparison with dark matter-only
numerical simulations the modifications imposed by baryons; ii) the mass in
stars and therefore the overall star formation efficiency, and the amount of
feedback; iii) by comparison with stellar population synthesis models, the
normalization of the stellar initial mass function. In this first paper of a
series, we present a sample of 16 secure, 1 probable, and 6 possible strong
lensing spiral galaxies, for which multi-band high-resolution images and
rotation curves were obtained using the Hubble Space Telescope and Keck-II
Telescope as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). The
sample includes 8 newly discovered secure systems. [abridged] We find that the
SWELLS sample of secure lenses spans a broad range of morphologies (from
lenticular to late-type spiral), spectral types (quantified by Halpha
emission), and bulge to total stellar mass ratio (0.22-0.85), while being
limited to M_*>10^{10.5} M_sun. The SWELLS sample is thus well-suited for
exploring the relationship between dark and luminous matter in a broad range of
galaxies. We find that the deflector galaxies obey the same size-mass relation
as that of a comparison sample of elongated non-lens galaxies selected from the
SDSS survey. We conclude that the SWELLS sample is consistent with being
representative of the overall population of high-mass high-inclination disky
galaxies.Comment: 21 pages, 6 figures, MNRAS, in pres
Screening for Hepatocellular Carcinoma among adults with HIV/Hepatitis B coinfection in Zambia: A Pilot Study
Background & aims: Chronic hepatitis B virus (HBV) infection is the main cause of hepatocellular carcinoma (HCC) in sub-Saharan Africa (SSA). In an established cohort of HIV/HBV-coinfected individuals on antiretroviral therapy (ART), we piloted an HCC screening initiative at two outpatient clinics in Lusaka, Zambia.
Methods: We performed abdominal ultrasound (AUS) and transient elastography in all patients.
Results: Among 279 HIV/HBV-coinfected patients, 165 (59.1%) were men, median age was 34 years (interquartile range 28-39) and median CD4 count 246 cells/µl (112-355). While 102 (36.6%) individuals had elevated transaminases, 114 (40.9%) had HBV levels >2000 IU/mL and 59 (24.6%) significant fibrosis. On AUS, 75 (26.9%) participants had hepatomegaly and 69 (24.7%) peri-portal fibrosis. Five patients had a liver lesion >1cm, an indication for confirmatory imaging.
Conclusions: In one of the first HCC screening initiatives in SSA, 2% of HIV/HBV-coinfected adults had significant liver lesions, and a quarter had findings suggestive of schistosomiasis-induced liver damage
Immunologic Risk Factors for Early Mortality After Starting Antiretroviral Therapy in HIV-Infected Zambian Children
To explore immunologic risk factors for death within 90 days of highly active antiretroviral therapy (HAART) initiation, CD4+ and CD8+ T cell subsets were measured by flow cytometry and characterized by logistic regression in 149 Zambian children between 9 months and 10 years of age enrolled in a prospective, observational study of the impact of HAART on measles immunity. Of 21 children who died during follow-up, 17 (81%) had known dates of death and 16 (76%) died within 90 days of initiating HAART. Young age and low weight-for-age z-scores were associated with increased risks of mortality within 90 days of starting HAART, whereas CD4+ T cell percentage was not associated with mortality. After adjusting for these factors, each 10% increase in CD8+ effector T cells increased the odds of overall mortality [OR=1.43 (95% CI: 1.08, 1.90)] and was marginally associated with early mortality [OR=1.29 (95% CI: 0.97, 1.72)]. Conversely, each 10% increase in CD4+ central memory T cells decreased the odds of overall [OR=0.06 (95% CI: 0.01, 0.59)] and early mortality [OR=0.09 (95% CI: 0.01, 0.97)]. Logistic regression prediction models demonstrated areas under the receiver-operator characteristic curves of ≥85% for early and overall mortality, with bootstrapped sensitivities of 82–85% upon validation, supporting the predictive accuracy of the models. CD4+ and CD8+ T cell subsets may be more accurate predictors of early mortality than CD4+ T cell percentages and could be used to identify children who would benefit from more frequent clinical monitoring after initiating HAART
Stars and dark matter in the spiral gravitational lens 2237+0305
We construct a mass model for the spiral lens galaxy 2237+0305, at redshift
z_l=0.04, based on gravitational-lensing constraints, HI rotation, and new
stellar-kinematic information, based on data taken with the ESI spectrograph on
the 10m Keck-II Telescope. High resolution rotation curves and velocity
dispersion profiles along two perpendicular directions, close to the major and
minor axes of the lens galaxy, were obtained by fitting the Mgb-Fe absorption
line region. The stellar rotation curve rises slowly and flattens at r~1.5"
(~1.1 kpc). The velocity dispersion profile is approximately flat. A
combination of photometric, kinematic and lensing information is used to
construct a mass model for the four major mass components of the system -- the
dark matter halo, disc, bulge, and bar. The best-fitting solution has a dark
matter halo with a logarithmic inner density slope of gamma=0.9+/-0.3 for
rho_DM propto r^-gamma, a bulge with M/L_B=6.6+/-0.3 Upsilon_odot, and a disc
with M/L_B =1.2+/-0.3 Upsilon_odot, in agreement with measurements of late-type
spirals. The bulge dominates support in the inner regions where the multiple
images are located and is therefore tightly constrained by the observations.
The disc is sub-maximal and contributes 45+/-11 per cent of the rotational
support of the galaxy at 2.2r_d. The halo mass is (2.0+/-0.6) x 10^12 M_odot,
and the stellar to virial mass ratio is 7.0+/-2.3 per cent, consistent with
typical galaxies of the same mass.Comment: 14 pages, 6 figures, MNRAS, in pres
Secular trends in pediatric antiretroviral treatment programs in rural and urban Zambia: a retrospective cohort study
<p>Abstract</p> <p>Background</p> <p>Since 2003 pediatric antiretroviral treatment (ART) programs have scaled-up in sub-Saharan Africa and should be evaluated to assess progress and identify areas for improvement. We evaluated secular trends in the characteristics and treatment outcomes of children in three pediatric ART clinics in urban and rural areas in Zambia.</p> <p>Methods</p> <p>Routinely collected data were analyzed from three ART programs in rural (Macha and Mukinge) and urban (Lusaka) Zambia between program implementation and July 2008. Data were obtained from electronic medical record systems and medical record abstraction, and were categorized by year of program implementation. Characteristics of all HIV-infected and exposed children enrolled in the programs and all children initiating treatment were compared by year of implementation.</p> <p>Results</p> <p>Age decreased and immunologic characteristics improved in all groups over time in both urban and rural clinics, with greater improvement observed in the rural clinics. Among children both eligible and ineligible for ART at clinic enrollment, the majority started treatment within a year. A high proportion of children, particularly those ineligible for ART at clinic enrollment, were lost to follow-up prior to initiating ART. Among children initiating ART, clinical and immunologic outcomes after six months of treatment improved in both urban and rural clinics. In the urban clinics, mortality after six months of treatment declined with program duration, and in the rural clinics, the proportion of children defaulting by six months increased with program duration.</p> <p>Conclusions</p> <p>Treatment programs are showing signs of progress in the care of HIV-infected children, particularly in the rural clinics where scale-up increased rapidly over the first three years of program implementation. However, continued efforts to optimize care are needed as many children continue to enroll in ART programs at a late stage of disease and thus are not receiving the full benefits of treatment.</p
Precursors to social and communication difficulties in infants at-risk for autism: gaze following and attentional engagement
Whilst joint attention (JA) impairments in autism have been widely studied, little is known about the early development of gaze following, a precursor to establishing JA. We employed eye-tracking to record gaze following longitudinally in infants with and without a family history of autism spectrum disorder (ASD) at 7 and 13 months. No group difference was found between at-risk and low-risk infants in gaze following behaviour at either age. However, despite following gaze successfully at 13 months, at-risk infants with later emerging socio-communication difficulties (both those with ASD and atypical development at 36 months of age) allocated less attention to the congruent object compared to typically developing at-risk siblings and low-risk controls. The findings suggest that the subtle emergence of difficulties in JA in infancy may be related to ASD and other atypical outcomes
Secondary infall model and dark matter scaling relations in intermediate redshift early - type galaxies
Scaling relations among dark matter (DM) and stellar quantities are a
valuable tool to constrain formation scenarios and the evolution of galactic
structures. However, most of the DM properties are actually not directly
measured, but derived through model dependent mass mapping procedures. It is
therefore crucial to adopt theoretically and observationally well founded
models. We use here an updated version of the secondary infall model (SIM) to
predict the halo density profile, taking into account the effects of angular
momentum, dissipative friction and baryons collapse. The resulting family of
halo profiles depends on one parameter only, the virial mass, and nicely fits
the projected mass and aperture velocity dispersion of a sample of intermediate
redshift lens galaxies. We derive DM related quantities (namely the column
density and the Newtonian acceleration) and investigate their correlations with
stellar mass, luminosity, effective radius and virial mass.Comment: 15 pages, 3 figures, 2 tables, accepted for publication on MNRA
- …