338 research outputs found
Mid-Infrared Imaging of the Bipolar Planetary Nebula M2-9 from SOFIA
We have imaged the bipolar planetary nebula M2-9 using SOFIA's FORCAST
instrument in six wavelength bands between 6.6 and 37.1 . A bright
central point source, unresolved with SOFIA's 4-to-5 beam,
is seen at each wavelength, and the extended bipolar lobes are clearly seen at
19.7 and beyond. The photometry between 10 and 25 is well fit
by the emission predicted from a stratified disk seen at large inclination, as
has been proposed for this source by Lykou et al and by Smith and Gehrz. The
principal new results in this paper relate to the distribution and properties
of the dust that emits the infrared radiation. In particular, a considerable
fraction of this material is spread uniformly through the lobes, although the
dust density does increase at the sharp outer edge seen in higher resolution
optical images of M2-9. The dust grain population in the lobes shows that small
( 1 ) particles appear to be present in
roughly equal amounts by mass. We suggest that collisional processing within
the bipolar outflow plays an important role in establishing the particle size
distribution.Comment: 40 pages, 9 figures, 2 table
Detection of [O III] at z~3: A Galaxy above the Main Sequence, Rapidly Assembling its Stellar Mass
We detect bright emission in the far infrared fine structure [O III] 88m
line from a strong lensing candidate galaxy, H-ATLAS J113526.3-014605,
hereafter G12v2.43, at z=3.127, using the generation Redshift (z)
and Early Universe Spectrometer (ZEUS-2) at the Atacama Pathfinder Experiment
Telescope (APEX). This is only the fifth detection of this far-IR line from a
sub-millimeter galaxy at the epoch of galaxy assembly. The observed [O III]
luminosity of likely
arises from HII regions around massive stars, and the amount of Lyman continuum
photons required to support the ionization indicate the presence of
equivalent O5.5 or higher stars;
where would be the lensing magnification factor. The observed line
luminosity also requires a minimum mass of in ionized gas, that is
of the estimated total molecular gas mass of
. We compile multi-band
photometry tracing rest-frame UV to millimeter continuum emission to further
constrain the properties of this dusty high redshift star-forming galaxy. Via
SED modeling we find G12v2.43 is forming stars at a rate of 916
and already has a stellar
mass of . We also
constrain the age of the current starburst to be 5 million years,
making G12v2.43 a gas rich galaxy lying above the star-forming main sequence at
z3, undergoing a growth spurt and, could be on the main sequence within
the derived gas depletion timescale of 66 million years.Comment: 11 pages, 3 figures, accepted for publication in The Astrophysical
Journa
Acceptability and feasibility of peer assisted supervision and support for intervention practitioners: a Q-methodology evaluation
Evidence-based interventions often include quality improvement methods to support fidelity and improve client outcomes. Clinical supervision is promoted as an effective way of developing practitioner confidence and competence in delivery; however, supervision is often inconsistent and embedded in hierarchical line management structures that may limit the opportunity for reflective learning. The Peer Assisted Supervision and Support (PASS) supervision model uses peer relationships to promote the self-regulatory capacity of practitioners to improve intervention delivery. The aim of the present study was to assess the acceptability and feasibility of PASS amongst parenting intervention practitioners. A Q-methodology approach was used to generate data and 30 practitioners volunteered to participate in the study. Data were analyzed and interpreted using standard Q-methodology procedures and by-person factor analysis yielded three factors. There was consensus that PASS was acceptable. Participants shared the view that PASS facilitated an environment of support where negative aspects of interpersonal relationships that might develop in supervision were not evident. Two factors represented the viewpoint that PASS was also a feasible model of supervision. However, the third factor was comprised of practitioners who reported that PASS could be time consuming and difficult to fit into existing work demands. There were differences across the three factors in the extent to which practitioners considered PASS impacted on their intervention delivery. The findings highlight the importance of organizational mechanisms that support practitioner engagement in supervision
First science results from SOFIA/FORCAST: The mid-infrared view of the compact HII region W3A
The massive star forming region W3 was observed with the faint object
infrared camera for the SOFIA telescope (FORCAST) as part of the Short Science
program. The 6.4, 6.6, 7.7, 19.7, 24.2, 31.5 and 37.1 \um bandpasses were used
to observe the emission of Polycyclic Aromatic Hydrocarbon (PAH) molecules,
Very Small Grains and Big Grains. Optical depth and color temperature maps of
W3A show that IRS2 has blown a bubble devoid of gas and dust of 0.05 pc
radius. It is embedded in a dusty shell of ionized gas that contributes 40% of
the total 24 \um emission of W3A. This dust component is mostly heated by far
ultraviolet, rather than trapped Ly photons. This shell is itself
surrounded by a thin (0.01 pc) photodissociation region where PAHs show
intense emission. The infrared spectral energy distribution (SED) of three
different zones located at 8, 20 and 25\arcsec from IRS2, show that the peak of
the SED shifts towards longer wavelengths, when moving away from the star.
Adopting the stellar radiation field for these three positions, DUSTEM model
fits to these SEDs yield a dust-to-gas mass ratio in the ionized gas similar to
that in the diffuse ISM. However, the ratio of the IR-to-UV opacity of the dust
in the ionized shell is increased by a factor 3 compared to the diffuse
ISM.Comment: Accepted for publication in ApJ letters; 13 pages, 3 figures 1 tabl
Performance Analysis of a Hardware Implemented Complex Signal Kurtosis Radio-Frequency Interference Detector
In the field of microwave radiometry, Radio Frequency Interference (RFI) consistently degrades the value of scientific results. Through the use of digital receivers and signal processing, the effects of RFI on scientific measurements can be reduced depending on certain circumstances. As technology allows us to implement wider band digital receivers for radiometry, the problem of RFI mitigation changes. Our work focuses on finding a detector that outperforms real kurtosis in wide band scenarios. The algorithm implemented is a complex signal kurtosis detector which was modeled and simulated. The performance of both complex and real signal kurtosis is evaluated for continuous wave, pulsed continuous wave, and wide band quadrature phase shift keying (QPSK) modulations. The use of complex signal kurtosis increased the detectability of interference
Performance Analysis of a Hardware Implemented Complex Signal Kurtosis Radio-Frequency Interference Detector
Radio-frequency interference (RFI) is a known problem for passive remote sensing as evidenced in the L-band radiometers SMOS, Aquarius and more recently, SMAP. Various algorithms have been developed and implemented on SMAP to improve science measurements. This was achieved by the use of a digital microwave radiometer. RFI mitigation becomes more challenging for microwave radiometers operating at higher frequencies in shared allocations. At higher frequencies larger bandwidths are also desirable for lower measurement noise further adding to processing challenges. This work focuses on finding improved RFI mitigation techniques that will be effective at additional frequencies and at higher bandwidths. To aid the development and testing of applicable detection and mitigation techniques, a wide-band RFI algorithm testing environment has been developed using the Reconfigurable Open Architecture Computing Hardware System (ROACH) built by the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) Group. The testing environment also consists of various test equipment used to reproduce typical signals that a radiometer may see including those with and without RFI. The testing environment permits quick evaluations of RFI mitigation algorithms as well as show that they are implementable in hardware. The algorithm implemented is a complex signal kurtosis detector which was modeled and simulated. The complex signal kurtosis detector showed improved performance over the real kurtosis detector under certain conditions. The real kurtosis is implemented on SMAP at 24 MHz bandwidth. The complex signal kurtosis algorithm was then implemented in hardware at 200 MHz bandwidth using the ROACH. In this work, performance of the complex signal kurtosis and the real signal kurtosis are compared. Performance evaluations and comparisons in both simulation as well as experimental hardware implementations were done with the use of receiver operating characteristic (ROC) curves. The complex kurtosis algorithm has the potential to reduce data rate due to onboard processing in addition to improving RFI detection performance
Wideband Digital Signal Processing Test-Bed for Radiometric RFI Mitigation
Radio Frequency Interference (RFI) is a persistent and growing problem experienced by spaceborne microwave radiometers. Recent missions such as SMOS, SMAP, and GPM has detected RFI in L, C, X, and K bands. To proactively deal with this issue, microwave radiometers must (1) Utilize new algorithms for RFI detection (2) Utilize fast digital back-ends that sample at hundreds of MHz. The wideband digital signal processing testbed (WB-RFI) is a platform that allows rapid deelopment and testing various RFI detection and mitigation algorithms
Wideband Digital Signal Processing Test-Bed for Radiometric RFI Mitigation
Radio Frequency Interference (RFI) is a persistent and growing problem experienced by spaceborne microwave radiometers. Recent missions such as SMOS, SMAP, and GPM have detected RFI in L, C, X, and K bands. To proactively deal with this issue, microwave radiometers must (1) Utilize new algorithms for RFI detection (2) Utilize fast digital back-ends that sample at hundreds of MHz. The wideband digital signal processing testbed (WB-RFI) is a platform that allows rapid development and testing various RFI detection and mitigation algorithms
An RFI Detection Algorithm for Microwave Radiometers Using Sparse Component Analysis
Radio Frequency Interference (RFI) is a threat to passive microwave measurements and if undetected, can corrupt science retrievals. The sparse component analysis (SCA) for blind source separation has been investigated to detect RFI in microwave radiometer data. Various techniques using SCA have been simulated to determine detection performance with continuous wave (CW) RFI
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