134 research outputs found
The Nature of Blue Cores in Spheroids: a Possible Connection with AGN and Star Formation
We investigate the physical nature of blue cores in early-type galaxies
through the first multi-wavelength analysis of a serendipitously discovered
field blue-nucleated spheroid in the background of the deep ACS/WFC griz
multicolor observations of the cluster Abell 1689. The resolved g-r, r-i and
i-z color maps reveal a prominent blue core identifying this galaxy as a
``typical'' case study, exhibiting variations of 0.5-1.0 mag in color between
the center and the outer regions, opposite to the expectations of reddened
metallicity induced gradients in passively evolved ellipticals. From a
Magellan-Clay spectrum we secure the galaxy redshift at . We find a
strong X-ray source coincident with the spheroid galaxy. Spectral features and
a high X-ray luminosity indicate the presence of an AGN in the galaxy. However,
a comparison of the X-ray luminosity to a sample derived from the Chandra Deep
Field South displays Lx to be comparable to Type I/QSO galaxies while the
optical flux is consistent with a normal star-forming galaxy. We conclude that
the galaxy's non-thermal component dominates at high-energy wavelengths while
we associate the spheroid blue light with the stellar spectrum of normal
star-forming galaxies. We argue about a probable association between the
presence of blue cores in spheroids and AGN activity.Comment: Accepted for publication in the Astrophysical Journal. 6 pages, 3
figures. Full resolution images available at
http://acs.pha.jhu.edu/~felipe/e-print
The Ultraviolet Emission Properties of Five Low-Redshift Active Galactic Nuclei at High Signal to Noise and Spectral Resolution
We analyze the ultraviolet (UV) emission line and continuum properties of
five low-redshift active galactic nuclei (four luminous quasars:
PKS~0405123, H1821+643, PG~0953+414, and 3C273, and one bright Seyfert 1
galaxy: Mrk~205). The HST spectra have higher signal-to-noise ratios (typically
per resolution element) and spectral resolution () than all
previously- published UV spectra used to study the emission characteristics of
active galactic nuclei. We include in the analysis ground-based optical spectra
covering \hb\ and the narrow [O III] 4959,5007 doublet. The
following new results are obtained: \lyb/\lya=0.030.12 for the four quasars,
which is the first accurate measurement of the long-predicted \lyb\ intensity
in QSOs. The cores of \lya\ and C~IV are symmetric to an accuracy of better
than
2.5% within about 2000 km s of the line peak. This high degree of
symmetry of \lya\ argues against models in which the broad line cloud velocity
field has a significant radial component. The observed smoothness of the \lya\
and C~IV line profiles requires at least individual clouds if bulk
velocity is the only line-broadening mechanism. The overall similarity of the
\lya\ and C IV 1549 profiles rules out models for the broad line
region (BLR) with a radial distribution of virialized....Comment: 39 pages (+ 6 pages of tables + 16 of figures), AST 93/2
James Webb Space Telescope Optical Simulation Testbed I: Overview and First Results
The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a
tabletop workbench to study aspects of wavefront sensing and control for a
segmented space telescope, including both commissioning and maintenance
activities. JOST is complementary to existing optomechanical testbeds for JWST
(e.g. the Ball Aerospace Testbed Telescope, TBT) given its compact scale and
flexibility, ease of use, and colocation at the JWST Science & Operations
Center. We have developed an optical design that reproduces the physics of
JWST's three-mirror anastigmat using three aspheric lenses; it provides similar
image quality as JWST (80% Strehl ratio) over a field equivalent to a NIRCam
module, but at HeNe wavelength. A segmented deformable mirror stands in for the
segmented primary mirror and allows control of the 18 segments in piston, tip,
and tilt, while the secondary can be controlled in tip, tilt and x, y, z
position. This will be sufficient to model many commissioning activities, to
investigate field dependence and multiple field point sensing & control, to
evaluate alternate sensing algorithms, and develop contingency plans. Testbed
data will also be usable for cross-checking of the WFS&C Software Subsystem,
and for staff training and development during JWST's five- to ten-year mission.Comment: Proceedings of the SPIE, 9143-150. 13 pages, 8 figure
M87: A Misaligned BL LAC?
The nuclear region of M87 was observed with the Faint Object Spectrograph
(FOS) on the Hubble Space Telescope (HST) at 6 epochs, spanning 18 months,
after the HST image quality was improved with the deployment of the corrective
optics (COSTAR) in December 1993. From the FOS target acquisition data, we have
established that the flux from the optical nucleus of M87 varies by a factor ~2
on time scales of ~2.5 months and by as much as 25% over 3 weeks, and remains
unchanged (<= 2.5%) on time scales of ~1 day. The changes occur in an
unresolved central region <= 5 pc in diameter, with the physical size of the
emitting region limited by the observed time scales to a few hundred
gravitational radii. The featureless continuum spectrum becomes bluer as it
brightens while emission lines remain unchanged. This variability combined with
the observations of the continuum spectral shape, strong relativistic boosting
and the detection of significant superluminal motions in the jet, strongly
suggest that M87 belongs to the class of BL Lac objects but is viewed at an
angle too large to reveal the classical BL Lac properties.Comment: 12 pages, 3 Postscript figure
Discovery of Two Distant Type Ia Supernovae in the Hubble Deep Field North with the Advanced Camera for Surveys
We present observations of the first two supernovae discovered with the
recently installed Advanced Camera for Surveys (ACS) on the Hubble Space
Telescope. The supernovae were found in Wide Field Camera images of the Hubble
Deep Field North taken with the F775W, F850LP, and G800L optical elements as
part of the ACS guaranteed time observation program. Spectra extracted from the
ACS G800L grism exposures confirm that the objects are Type Ia supernovae (SNe
Ia) at redshifts z=0.47 and z=0.95. Follow-up HST observations have been
conducted with ACS in F775W and F850LP and with NICMOS in the near-infrared
F110W bandpass, yielding a total of 9 flux measurements in the 3 bandpasses
over a period of 50 days in the observed frame. We discuss many of the
important issues in doing accurate photometry with the ACS. We analyze the
multi-band light curves using two different fitting methods to calibrate the
supernovae luminosities and place them on the SNe Ia Hubble diagram. The
resulting distances are consistent with the redshift-distance relation of the
accelerating universe model, although evolving intergalactic grey dust remains
as a less likely possibility. The relative ease with which these SNe Ia were
found, confirmed, and monitored demonstrates the potential ACS holds for
revolutionizing the field of high-redshift SNe Ia, and therefore of testing the
accelerating universe cosmology and constraining the "epoch of deceleration".Comment: 11 pages, 8 embedded figures. Accepted for publication in Ap
Strong Lensing Analysis of A1689 from Deep Advanced Camera Images
We analyse deep multi-colour Advanced Camera images of the largest known
gravitational lens, A1689. Radial and tangential arcs delineate the critical
curves in unprecedented detail and many small counter-images are found near the
center of mass. We construct a flexible light deflection field to predict the
appearance and positions of counter-images. The model is refined as new
counter-images are identified and incorporated to improve the model, yielding a
total of 106 images of 30 multiply lensed background galaxies, spanning a wide
redshift range, 1.0z5.5. The resulting mass map is more circular in
projection than the clumpy distribution of cluster galaxies and the light is
more concentrated than the mass within . The projected mass profile
flattens steadily towards the center with a shallow mean slope of
, over the observed range,
r, matching well an NFW profile, but with a relatively high
concentration, . A softened isothermal profile
(\arcs) is not conclusively excluded, illustrating that
lensing constrains only projected quantities. Regarding cosmology, we clearly
detect the purely geometric increase of bend-angles with redshift. The
dependence on the cosmological parameters is weak due to the proximity of
A1689, , constraining the locus, .
This consistency with standard cosmology provides independent support for our
model, because the redshift information is not required to derive an accurate
mass map. Similarly, the relative fluxes of the multiple images are reproduced
well by our best fitting lens model.Comment: Accepted by ApJ. For high quality figures see
http://wise-obs.tau.ac.il/~kerens/A168
Paper Session II-B - The Advanced Camera for the Hubble Space Telescope
The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) will have a high throughput, wide field, optical and I-band camera (WFC), a critically sampled high resolution camera (HRC), and a high throughput, moderate field of view far ultraviolet, solar-blind camera (SBC). The key characteristics of the ACS are listed in Table 1. The throughputs include the geometrical, scattering, and reflectivity losses from the HST optical telescope assembly (Burrows, HST OTA Handbook). Two figures are listed for the ACS efficiencies. The first is the efficiency using the quantum efficiency (QE) of the Scientific Imaging Technologies (SITe) 2K x 4K WFC CCDs and the SITe HRC 1K ÂŽ 1K CCDs selected for the first build of the flight cameras. The second and higher efficiencies are those achieved with SITe CCDs processed and anti-reflection coated at Steward Observatory by Dr. Michael Lesser. We plan to use these better CCDs for the second build of the flight cameras
The weekend matters: Relationships between stress recovery and affective experiences
Non-work experiences during the weekend provide opportunities to recover from work demands and to replenish lost resources. This longitudinal study examined how specific recovery experiences during the weekend (relaxation, mastery, control, and detachment), as well as non-work hassles, were associated with specific positive and negative affective states during the following workweek. Participants (N 1â4 229) completed surveys before the week- end, during the weekend, and during the following workweek. Hierarchical regression analyses revealed that after controlling for affective states the previous week, recovery experiences during the weekend significantly explained variance in affective states at the end of the weekend and during the following workweek. Suggestions for future research include a closer examination of the role of individual differences, self-regulation, and specific work demands in employee stress recovery
Designing a multifaceted quality improvement intervention in primary care in a country where general practice is seeking recognition: the case of Cyprus
<p>Abstract</p> <p>Background</p> <p>Quality Improvement Interventions require significant financial investments, and therefore demand careful consideration in their design in order to maximize potential benefits. In this correspondence we present the methodological approach of a multifaceted quality improvement intervention aiming to improve quality of care in primary care, properly tailored for a country such as Cyprus where general practice is currently seeking recognition.</p> <p>Methods</p> <p>Our methodological approach was focused on the design of an open label, community-based intervention controlled trial using all patients from two urban and two rural public primary care centers diagnosed with hypertension and type II diabetes mellitus. The design of our intervention was grounded on a strong theoretical framework that included the Unified Theory of Acceptance and Use of Technology, and the Chronic Care Model, which synthesize evidence-based system changes in accordance with the Theory of Planned Behavior and the Theory of Reasoned Action. The primary outcome measure was improvement in the quality of care for two chronic diseases evaluated through specific clinical indicators, as well as the patient satisfaction assessed by the EUROPEP questionnaire and additional personal interviews.</p> <p>Results</p> <p>We designed a multifaceted quality improvement intervention model, supported by a varying degree of scientific evidence, tailored to local needs and specific country characteristics. Overall, the main components of the intervention were the development and adoption of an electronic medical record and the introduction of clinical guidelines for the management of the targeted chronic diseases facilitated by the necessary model of organizational changes.</p> <p>Conclusion</p> <p>Health planners and policy makers need to be aware of the potential use of certain theoretical models and applied methodology as well as inexpensive tools that may be suitably tailored to the local needs, in order to effectively design quality improvement interventions in primary care settings.</p
Beyond Environmental Regulatory Fragmentation: Signs of Integration in the Case of the Great Lakes Basin
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72007/1/j.1468-0491.1995.tb00197.x.pd
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