In order for the Wide-Field Infrared Survey Telescope (WFIRST) and other stage IV dark energy experiments (e.g., Large Synoptic Survey Telescope, LSST; and Euclid) to infer cosmological parameters ...not limited by systematic errors, accurate redshift measurements are needed. This accuracy can be met by using spectroscopic subsamples to calibrate the photometric redshifts for the full sample. In this work, we find the minimal number of spectra required for the WFIRST weak-lensing redshift calibration by employing the Self-Organizing Map (SOM) spectroscopic sampling technique. We use galaxies from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) to build the LSST+WFIRST lensing analog sample of ∼36,000 objects and to train the LSST+WFIRST SOM. We find that 26% of the WFIRST lensing sample consists of sources fainter than the Euclid depth in the optical, 91% of which live in color cells already occupied by brighter galaxies. We demonstrate the similarity between faint and bright galaxies as well as the feasibility of redshift measurements at different brightness levels. Our results suggest that the spectroscopic sample acquired for calibration to the Euclid depth is sufficient for calibrating the majority of the WFIRST color space. For the spectroscopic sample to fully represent the synthetic color space of WFIRST, we recommend obtaining additional spectroscopy of ∼0.2-1.2k new sources in cells occupied by mostly faint galaxies. We argue that either the small area of the CANDELS fields and the small overall sample size or the large photometric errors might be the reason for no/fewer bright galaxies mapped to these cells. Acquiring the spectra of these sources will confirm the above findings and will enable the comprehensive calibration of the WFIRST color-redshift relation.
Analyses of spectra obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, together with spectra from the Copernicus and interstellar medium absorption profile spectrograph ...(IMAPS) instruments, reveal an unexplained, very wide range in the observed deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic disk beyond the Local Bubble. We argue that spatial variations in the depletion of deuterium onto dust grains can explain these local variations in the observed gas-phase D/H ratios. We present a variable deuterium depletion model that naturally explains the constant measured values of D/H inside the Local Bubble, the wide range of gas-phase D/H ratios observed in the intermediate regime log N(H super(I)) = 19.2-20.7, and the low gas-phase D/H ratios observed at larger hydrogen column densities. We consider empirical tests of the deuterium depletion hypothesis: (1) correlations of gas-phase D/H ratios with depletions of the refractory metals iron and silicon, and (2) correlation with the H sub(2) rotational temperature. Both of these tests are consistent with deuterium depletion from the gas phase in cold, not recently shocked regions of the ISM, and high gas-phase D/H ratios in gas that has been shocked or otherwise heated recently. We argue that the most representative value for the total (gas plus dust) D/H ratio within 1 kpc of the Sun is .23.1 c 2.4(1 s) parts per million (ppm). This ratio constrains Galactic chemical evolution models to have a very small deuterium astration factor, the ratio of primordial to total (D/H) ratio in the local region of the Galactic disk, which we estimate to be f sub(d),1.19 super(-0.15 +0.16) (1 s) or ,1.12 c 0.14(1 s) depending on the adopted light-element nuclear reaction rates.
Unlike optical CCDs, near-infrared detectors, which are based on CMOS hybrid readout technology, typically suffer from electrical crosstalk between the pixels. The interpixel capacitance (IPC) ...responsible for the crosstalk affects the point-spread function (PSF) of the telescope, increasing the size and modifying the shape of all objects in the images while correlating the Poisson noise. Upcoming weak lensing surveys that use these detectors, such as WFIRST, place stringent requirements on the PSF size and shape (and the level at which these are known), which in turn must be translated into requirements on IPC. To facilitate this process, we present a first study of the effect of IPC on WFIRST PSF sizes and shapes. Realistic PSFs are forward-simulated from physical principles for each WFIRST bandpass. We explore how the PSF size and shape depends on the range of IPC coupling with pixels that are connected along an edge or corner; for the expected level of IPC in WFIRST, IPC increases the PSF sizes by ∼5%. We present a linear fitting formula that describes the uncertainty in the PSF size or shape due to uncertainty in the IPC, which could arise for example due to unknown time evolution of IPC as the detectors age or due to spatial variation of IPC across the detector. We also study of the effect of a small anisotropy in the IPC, which further modifies the PSF shapes. Our results are a first, critical step in determining the hardware and characterization requirements for the detectors used in the WFIRST survey.
Comorbidity of substance use and psychiatric disorders, particularly depressive disorders, are well established. The impact of comorbidity on treatment outcomes, particularly following short-term ...inpatient detoxification and medical management units, has yet to be fully explored. This study reviewed 456 records of patients voluntarily presenting for medical management of substance misuse in Sydney, Australia. Documented psychiatric comorbidities and primary substance of misuse were extracted and used to predict length of stay, discharge against medical advice and number of readmissions. Our results showed that psychiatric comorbidity did not significantly predict treatment outcomes, although depression was reported in more than half our cohort, along with elevated rates of Post-traumatic Stress Disorder, anxiety disorders and bipolar affective disorders. Medication non-compliance and primary substance of misuse significantly predicted length of stay and discharge against medical advice. Further research into how specific substances interact and affect specific psychiatric disorders is needed to guide optimal treatment options.
We report on the first detection of the noble gases krypton (Z = 36) and xenon (54) in a white dwarf. About 20 Kr VI-VII and Xe VI-VII lines were discovered in the ultraviolet spectrum of the hot ...DO-type white dwarf RE 0503-289. The observations, performed with the Far Ultraviolet Spectroscopic Explorer, also reveal highly ionized photospheric lines from other trans-iron group elements, namely Ga (31), Ge (32), As (33), Se (34), Mo (42), Sn (50), Te (52), and I (53), from which gallium and molybdenum are new discoveries in white dwarfs, too. For Kr and Xe, we performed an NLTE analysis and derived mass fractions of log Kr = -4.3 + or - 0.5 and log Xe = -4.2 + or - 0.6, corresponding to an enrichment by factors of 450 and 3800, respectively, relative to the Sun. The origin of the large overabundances is unclear. We discuss the roles of neutron-capture nucleosynthesis in the precursor star and radiation-driven diffusion. It is possible that diffusion is insignificant and that the observed metal abundances constrain the evolutionary history of the star. Its hydrogen deficiency may be the consequence of a late helium-shell flash or a binary white dwarf merger.
Substance use disorder is a chronic disease carrying a high risk of morbidity and mortality. We report a case of a patient on long-term opioid agonist treatment who was diagnosed with metastatic ...cholangiocarcinoma and was referred to palliative care services almost contemporaneously with this diagnosis. In this report, we explore the challenges posed in offering holistic care during the end of life of a patient with a history of opioid dependence. A coordinated approach by addiction medicine and palliative care teams can allow patients from this complex cohort to ultimately die with dignity.
To probe the distribution and physical characteristics of interstellar gas at temperatures T approximately 3 x 10 super(5) K in the disk of the Milky Way, we have used the Far Ultraviolet ...Spectroscopic Explorer (FUSE) to observe absorption lines of O VI lambda 1032 toward 148 early-type stars situated at distances >1 kpc. After subtracting off a mild excess of O vI arising from the Local Bubble, combining our new results with earlier surveys of O vI, and eliminating stars that show conspicuous localized X-ray emission, we find an average O vI midplane density no = 1.3 x 10 super(-8) cm super(-3). The density decreases away from the plane of the Galaxy in a way that is consistent with an exponential scale height of 3.2 kpc at negative latitudes or 4.6 kpc at positive latitudes. Average volume densities of O vI along different sight lines exhibit a dispersion of about 0.26 dex, irrespective of the distances to the target stars. This indicates that O vI does not arise in randomly situated clouds of a fixed size and density, but instead is distributed in regions that have a very broad range of column densities, with the more strongly absorbing clouds having a lower space density. Line widths and centroid velocities are much larger than those expected from differential Galactic rotation, but they are nevertheless correlated with distance and N(O vI), which reinforces our picture of a diverse population of hot plasma regions that are ubiquitous over the entire Galactic disk. The velocity extremes of the O vI profiles show a loose correlation with those of very strong lines of less ionized species, supporting a picture of a turbulent, multiphase medium churned by shock-heated gas from multiple supernova explosions.
Geosynchronous orbits are appealing for solar or astrophysical observatories because they permit continuous data downlink at high rates. The radiation environment in these orbits presents unique ...challenges, however. This paper describes both the characteristics of the radiation environment in geosynchronous orbit and the mechanisms by which this radiation generates backgrounds in photon detectors. Shielding considerations are described, and a preliminary shielding design for the proposed Wide-Field InfraRed Survey Telescope observatory is presented as a reference for future space telescope concept studies that consider a geosynchronous orbit.
Detection of Iron in PG1159 Stars Werner, Klaus; Rauch, Thomas; Kruk, Jeffrey W
Astrophysical journal. Letters,
08/2010, Letnik:
719, Številka:
1
Journal Article
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Odprti dostop
Up to now, iron had not been found in any hydrogen-deficient (pre-) white dwarf of spectral type PG1159, despite intense searching in a number of objects. Consequently, an iron deficiency was ...claimed, in some cases at least 1 dex. The primary indicators were UV lines of Fe VII. Therefore, the search was confined to relatively cool PG1159 stars (T{sub eff} {approx}<150,000 K), otherwise Fe is too strongly ionized for a significant population of Fe VII. In this Letter, we announce the discovery of iron in the very hottest PG1159 stars (T{sub eff} = 150,000-200,000 K; RX J2117.1+3412, K 1-16, Longmore 4, NGC 246, H1504+65), based on the identification of the Fe X {lambda}{lambda}979.3, 1022.9 lines in spectra obtained with the Far Ultraviolet Spectroscopic Explorer. Surprisingly, our analysis results in a solar iron abundance for these stars. It is conspicuous that they are among the most massive PG1159 stars (0.71-0.82 M{sub sun}), in contrast to those objects for which strongest Fe deficiency was claimed (0.53-0.56 M{sub sun}).
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