157 research outputs found
Search for point sources and diffuse emission from the Galactic plane with the HEGRA-IACT-system
The HEGRA-IACT-system with a FoV of ~1.5 deg radius has been used for
surveying one quater of the Galactic disc in respect to point sources,
moderately extended sources and for diffuse emission in the energy range above
1 TeV. In total 140 h of good observation time were accumulated.
No new source has been discoverd. Limits on the level of 20% or lower of the
Crab flux on about 87 potential sources like SNR, Pulsars and EGRET sources are
derived. A limit on the diffuse emission is given on the level of dPhi/dE(E=1
TeV) = 6.1 10^-15 ph cm-2 s-1 sr-1 Mev-1 resulting in a lower limit of 2.5 on
the spectral index for the extrapolation of the meassured EGRET flux for the
diffuse emission.Comment: 4 pages, 5 figures, 1 table, Submitted to ICRC, Hambur
Very Extended X-ray and H-alpha Emission in M82: Implications for the Superwind Phenomenon
We discuss the properties and implications of a 3.7x0.9 kpc region of
spatially-coincident X-ray and H-alpha emission about 11.6 kpc to the north of
the galaxy M82 previously discussed by Devine and Bally (1999). The PSPC X-ray
spectrum is fit by thermal plasma (kT=0.80+-0.17 keV) absorbed by only the
Galactic foreground column density. We evaluate the relationship of the
X-ray/H-alpha ridge to the M82 superwind. The main properties of the X-ray
emission can all be explained as being due to shock-heating driven as the
superwind encounters a massive ionized cloud in the halo of M82. This encounter
drives a slow shock into the cloud, which contributes to the excitation of the
observed H-alpha emission. At the same time, a fast bow-shock develops in the
superwind just upstream of the cloud, and this produces the observed X-ray
emission. This interpretation would imply that the superwind has an outflow
speed of roughly 800 km/s, consistent with indirect estimates based on its
general X-ray properties and the kinematics of the inner kpc-scale region of
H-alpha filaments. The gas in the M82 ridge is roughly two orders-of-magnitude
hotter than the minimum "escape temperature" at this radius, so this gas will
not be retained by M82.
(abridged)Comment: 24 pages (latex), 3 figures (2 gif files and one postscript),
accepted for publication in Part 1 of The Astrophysical Journa
Multicolour Optical Imaging of IR-Warm Seyfert Galaxies. V. Morphologies and Interactions. Challenging the Orientation Model
This paper is the last in a series, investigating the optical properties of a
sample of mid-IR Warm Seyfert galaxies and of a control sample of mid-IR cold
galaxies. In the present paper we parametrize the morphologies and interaction
properties of the host galaxies and combine these with the major conclusions in
our previous papers. Our results confirm that nuclear activity is linked to
galactic interactions. We suggest an alternative view for the simple
orientation-obscuration model postulated for Seyfert types 1 and 2, that takes
into account the time evolution of their environmental and morphological
properties. Within this view, an evolutionary link between starburst-dominated
and AGN-dominated IR emission is also suggested, to account for the
observational discriminator (mid-IR excess) between our Warm and Cold samples.Comment: 24 pages, including 6 figures and 3 tables (figure 5 included as
independent file), Submitted to Ap
Physical Conditions and Star Formation Activity in the Intragroup Medium of Stephan's Quintet
New multi-band observations of the famous compact group of galaxies Stephan's
Quintet (SQ) are presented and analyzed. These include far infrared (FIR)
images at 60 and 100 (ISOPHOT C-100 camera), radio continuum
images at 1.4 GHz (VLA B-array) and 4.86 GHz (VLA C-array), and long-slit
optical spectrographs (Palomar telescope). With these new data, we aim
to learn more about the X-ray/radio ridge in the middle of the intragroup
medium (IGM) and the IGM starburst SQ-A, both are likely to be caused by the
high speed collision ( km s) between the intruder galaxy NGC
7318b ( km s) and the IGM ( km s).Comment: 31 pages text, 17 figures. Accepted by ApJ. A PS file including all
figures can be found in
http://spider.ipac.caltech.edu/staff/cxu/preprints/sq/apj_sq.ps.g
The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes, Part II: mirror alignment and point spread function
Mirror facets of the H.E.S.S. imaging atmospheric Cherenkov telescopes are
aligned using stars imaged onto the closed lid of the PMT camera, viewed by a
CCD camera. The alignment procedure works reliably and includes the automatic
analysis of CCD images and control of the facet alignment actuators. On-axis,
80% of the reflected light is contained in a circle of less than 1 mrad
diameter. The spot widens with increasing angle to the telescope axis. In
accordance with simulations, the spot size has roughly doubled at an angle of
1.4 degr. from the axis. The expected variation of spot size with elevation due
to deformations of the support structure is visible, but is completely
non-critical over the usual working range. Overall, the optical quality of the
telescope exceeds the specifications.Comment: 23 pages, 13 figure
Stellar Evolutionary Effects on the Abundances of PAH and SN-Condensed Dust in Galaxies
Spectral and photometric observations of nearby galaxies show a correlation
between the strength of their mid-IR aromatic features, attributed to PAH
molecules, and their metal abundance, leading to a deficiency of these features
in low-metallicity galaxies. In this paper, we suggest that the observed
correlation represents a trend of PAH abundance with galactic age, reflecting
the delayed injection of carbon dust into the ISM by AGB stars in the final
post-AGB phase of their evolution. AGB stars are the primary sources of PAHs
and carbon dust in galaxies, and recycle their ejecta back to the interstellar
medium only after a few hundred million years of evolution on the main
sequence. In contrast, more massive stars that explode as Type II supernovae
inject their metals and dust almost instantaneously after their formation. We
first determined the PAH abundance in galaxies by constructing detailed models
of UV-to-radio SED of galaxies that estimate the contribution of dust in
PAH-free HII regions, and PAHs and dust from photodissociation regions, to the
IR emission. All model components: the galaxies' stellar content, properties of
their HII regions, and their ionizing and non-ionizing radiation fields and
dust abundances, are constrained by their observed multiwavelength spectrum.
After determining the PAH and dust abundances in 35 nearby galaxies using our
SED model, we use a chemical evolution model to show that the delayed injection
of carbon dust by AGB stars provides a natural explanation to the dependence of
the PAH content in galaxies with metallicity. We also show that larger dust
particles giving rise to the far-IR emission follow a distinct evolutionary
trend closely related to the injection of dust by massive stars into the ISM.Comment: ApJ, 69 pages, 46 figures, Accepte
The development and application of a new tool to assess the adequacy of the content and timing of antenatal care
Abstract
Background: Current measures of antenatal care use are limited to initiation of care and number of visits. This
study aimed to describe the development and application of a tool to assess the adequacy of the content and
timing of antenatal care.
Methods: The Content and Timing of care in Pregnancy (CTP) tool was developed based on clinical relevance for
ongoing antenatal care and recommendations in national and international guidelines. The tool reflects minimal
care recommended in every pregnancy, regardless of parity or risk status. CTP measures timing of initiation of care,
content of care (number of blood pressure readings, blood tests and ultrasound scans) and whether the
interventions were received at an appropriate time. Antenatal care trajectories for 333 pregnant women were then
described using a standard tool (the APNCU index), that measures the quantity of care only, and the new CTP tool.
Both tools categorise care into 4 categories, from âInadequateâ (both tools) to âAdequate plusâ (APNCU) or
âAppropriateâ (CTP). Participants recorded the timing and content of their antenatal care prospectively using diaries.
Analysis included an examination of similarities and differences in categorisation of care episodes between the
tools.
Results: According to the CTP tool, the care trajectory of 10,2% of the women was classified as inadequate, 8,4%
as intermediate, 36% as sufficient and 45,3% as appropriate. The assessment of quality of care differed significantly
between the two tools. Seventeen care trajectories classified as âAdequateâ or âAdequate plusâ by the APNCU were
deemed âInadequateâ by the CTP. This suggests that, despite a high number of visits, these women did not receive
the minimal recommended content and timing of care.
Conclusions: The CTP tool provides a more detailed assessment of the adequacy of antenatal care than the
current standard index. However, guidelines for the content of antenatal care vary, and the tool does not at the
moment grade over-use of interventions as âInappropriateâ. Further work needs to be done to refine the content
items prior to larger scale testing of the impact of the new measure
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