6,738 research outputs found
High sensitivity operation of discrete solid state detectors at 4 K
Techniques are described to allow operation of discrete, solid state detectors at 4 K with optimized JFET amplifiers. Three detector types cover the 0.6 to 4 mm spectral range with NEP approximately equal to 10 to the 16th power Hz (-1/2) for two of the types and potential improvement to this performance for the third. Lower NEP's are anticipated at longer infrared wavelengths
The WISE AGN Catalog
We present two large catalogs of AGN candidates identified across ~75% of the
sky from the Wide-field Infrared Survey Explorer's AllWISE Data Release. Both
catalogs, some of the largest such catalogs published to date, are selected
purely on the basis of mid-IR photometry in the WISE W1 and W2 bands. The
catalogs are designed to be appropriate for a broad range of scientific
investigations, with one catalog emphasizing reliability while the other
emphasizes completeness. Specifically, the R90 catalog consists of 4,543,530
AGN candidates with 90% reliability, while the C75 catalog consists of
20,907,127 AGN candidates with 75% completeness. We provide a detailed
discussion of potential artifacts, and excise portions of the sky close to the
Galactic Center, Galactic Plane, nearby galaxies, and other expected
contaminating sources. Our final catalogs cover 30,093 deg^2 of extragalactic
sky. These catalogs are expected to enable a broad range of science, and we
present a few simple illustrative cases. From the R90 sample we identify 45
highly variable AGN lacking radio counterparts in the FIRST survey, implying
they are unlikely to be blazars. One of these sources, WISEA
J142846.71+172353.1, is a mid-IR-identified changing-look quasar at z=0.104. We
characterize our catalogs by comparing them to large, wide-area AGN catalogs in
the literature, specifically UV-to-near-IR quasar selections from SDSS and
XDQSOz, mid-IR selection from Secrest et al. (2015) and X-ray selection from
ROSAT. From the latter work, we identify four ROSAT X-ray sources that each are
matched to three WISE-selected AGN in the R90 sample within 30". Palomar
spectroscopy reveals one of these systems, 2RXS J150158.6+691029, to consist of
a triplet of quasars at z=1.133 +/- 0.004, suggestive of a rich group or
forming galaxy cluster.(Abridged)Comment: Accepted for publication in the Astrophysical Journal Supplements.
Updated with comments from the referee. 20 pages, 15 figures, 8 tables. The
WISE AGN Catalogs can be made available upon request by writing to
[email protected]
The detection and photometric redshift determination of distant galaxies using SIRTF's Infrared Array Camera
We investigate the ability of the Space Infrared Telescope Facility's
Infrared Array Camera to detect distant (z ~ 3)galaxies and measure their
photometric redshifts. Our analysis shows that changing the original long
wavelength filter specifications provides significant improvements in
performance in this and other areas.Comment: 28 pages incl 12 figures; to appear in June 1999 PASP. Fig.12
replaced with corrected versio
Bringing genetics into primary care: findings from a national evaluation of pilots in England
Objectives: Developments in genetic knowledge and clinical applications are seen as rendering traditional modes of organizing genetics provision increasingly inappropriate. In common with a number of developed world countries the UK has sought to increase the role of primary care in delivering such services. However, efforts to reconfigure service delivery face multiple challenges associated with divergent policy objectives, organizational boundaries and professional cultures. This paper presents findings from an evaluation of an English initiative to integrate genetics into 'mainstream' clinical provision in the National Health Service. Methods: Qualitative research in 11 case-study sites focusing on attempts by pilots funded by the initiative to embed knowledge and provision within primary care illustrating barriers faced and the ways in which these were surmounted. Results: Lack of intrinsic interest in clinical genetics among primary care staff was compounded by national targets that focused their attention elsewhere and by service structures that rendered genetics a peripheral concern demanding minimal engagement. Established divisions between the commissioning of mainstream and specialist services, along with the pressures of shorter-term targets, impeded ongoing funding. Conclusions: More wide-ranging policy and organizational support is required if the aim of entrenching genetics knowledge and practice across the Health Service is to be realized
The Galaxy Population of Cluster RXJ0848+4453 at z=1.27
We present a study of the galaxy population in the cluster RXJ0848+4453 at
z=1.27, using deep HST NICMOS and WFPC2 images. We morphologically classify all
galaxies to K_s=20.6 that are covered by the HST imaging, and determine
photometric redshifts using deep ground based BRIzJK_s photometry. Of 22 likely
cluster members with morphological classifications, eleven (50%) are classified
as early-type galaxies, nine (41%) as spiral galaxies, and two (9%) as
``merger/peculiar''. At HST resolution the second brightest cluster galaxy is
resolved into a spectacular merger between three red galaxies of similar
luminosity, separated from each other by ~6 kpc, with an integrated magnitude
K=17.6 (~3 L* at z=1.27). The two most luminous early-type galaxies also show
evidence for recent or ongoing interactions. Mergers and interactions between
galaxies are possible because RXJ0848+4453 is not yet relaxed. The fraction of
early-type galaxies in our sample is similar to that in clusters at 0.5<z<1,
and consistent with a gradual decrease of the number of early-type galaxies in
clusters from z=0 to z=1.3. We find evidence that the color-magnitude relation
of the early-type galaxies is less steep than in the nearby Coma cluster. This
may indicate that the brightest early-type galaxies have young stellar
populations at z=1.27, but is also consistent with predictions of single age
``monolithic'' models with a galactic wind. The scatter in the color-magnitude
relation is ~0.04 in rest frame U-V, similar to that in clusters at 0<z<1.
Taken together, these results show that luminous early-type galaxies exist in
clusters at z~1.3, but that their number density may be smaller than in the
local Universe. Additional observations are needed to determine whether the
brightest early-type galaxies harbor young stellar populations.Comment: Accepted for publication in The Astrophysical Journal Letter
Multiple case-study analysis of quality management practices within UK Six Sigma and non-Six Sigma manufacturing small- and medium-sized enterprises
This paper examines multiple case-study analysis of quality management practices within UK Six Sigma and non-Six Sigma manufacturing small- and medium-sized enterprises
Multiaperture Photometry of Galaxies in the Coma Cluster
We present a set of photometry for 745 band selected
objects in a region centered on the core of the Coma
cluster. This includes 516 galaxies and is at least 80% complete to H=16, with
a spectroscopically complete sample of 111 cluster members (nearly all with
morphological classification) for . For each object we present total
\cite{kron80} magnitudes and aperture photometry. As an example, we use these
data to derive color-magnitude relations for Coma early-type galaxies, measure
the intrinsic scatter of these relations and its dependence on galaxy mass, and
address the issue of color gradients. We find that the color gradients are mild
and that the intrinsic scatter about the color-magnitude relation is small
( mag in and less than in , or ).
There is no evidence that the intrinsic scatter varies with galaxy luminosity,
suggesting that the cluster red sequence is established at early epochs over a
range of in stellar mass.Comment: 41 pages, 5 figures, 18 data tables attached to source files or
available on request from R. De propris. Accepted for publication in
Astrophysical Journal Supplement Serie
Heavy X-ray obscuration in the most-luminous galaxies discovered by WISE
Hot Dust-Obscured Galaxies (Hot DOGs) are hyperluminous
() infrared galaxies with
extremely high (up to hundreds of K) dust temperatures. The sources powering
both their extremely high luminosities and dust temperatures are thought to be
deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs
could therefore represent a key evolutionary phase in which the SMBH growth
peaks. X-ray observations can be used to study their obscuration levels and
luminosities. In this work, we present the X-ray properties of the 20
most-luminous () known Hot DOGs at
. Five of them are covered by long-exposure ( ks) Chandra and
XMM-Newton observations, with three being X-ray detected, and we study their
individual properties. One of these sources (W01160505) is a Compton-thick
candidate, with column density
derived from X-ray spectral fitting. The remaining 15 Hot DOGs have been
targeted by a Chandra snapshot (3.1 ks) survey. None of these 15 is
individually detected; therefore we applied a stacking analysis to investigate
their average emission. From hardness-ratio analysis, we constrained the
average obscuring column density and intrinsic luminosity to be
log and
, which are consistent with
results for individually detected sources. We also investigated the
and relations, finding hints that Hot
DOGs are typically X-ray weaker than expected, although larger samples of
luminous obscured QSOs are needed to derive solid conclusions.Comment: MNRAS, accepted 2017 November 29 . Received 2017 November 29 ; in
original form 2017 October 11. 15 pages, 6 figure
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