307 research outputs found
A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219
We analyze the optical, UV, and X-ray microlensing variability of the lensed
quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands
(spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of
F275W (rest-frame 1089A) Hubble Space Telescope data, and high-cadence R-band
(rest-frame 2770A) monitoring spanning eleven years. Our joint analysis
provides robust constraints on the extent of the X-ray continuum emission
region and the projected area of the accretion disk. The best-fit half-light
radius of the soft X-ray continuum emission region is between 5x10^13 and 10^15
cm, and we find an upper limit of 10^15 cm for the hard X-rays. The best-fit
soft-band size is about 13 times smaller than the optical size, and roughly 7
GM_BH/c^2 for a 2.8x10^8 M_sol black hole, similar to the results for other
systems. We find that the UV emitting region falls in between the optical and
X-ray emitting regions at 10^14 cm < r_1/2,UV < 3x10^15 cm. Finally, the
optical size is significantly larger, by 1.5*sigma, than the theoretical
thin-disk estimate based on the observed, magnification-corrected I-band flux,
suggesting a shallower temperature profile than expected for a standard disk.Comment: Replaced with accepted version to Ap
Very large Magneto-impedance and its scaling behavior in amorphous Fe73.5Nb3Cu1Si13.5B9 ribbon
Magneto-impedance (MI) effects have been observed for amorphous
Fe73.5Nb3Cu1Si13.5B9 ribbon which has been excited by an a.c. magnetic field
parallel to the length of the ribbon. Maximum relative change in MI as large as
-99% was observed which has never been reported before. The relative change in
MI, when plotted against scaled field was found to be nearly frequency
independent. A phenomenological formula for magneto-impedance, Z(H), in a
ferromagnetic material, is proposed based on Pade approximant to describe the
scaled behavior of MI.Comment: 20 pages, 7 figures, article in press, Physica B (2007
Psychometric characteristics of the FertiQoL questionnaire in a German sample of infertile individuals and couples.
Background: FertiQoL is a questionnaire internationally developed to measure fertility-specific quality of life. It has been validated with infertile populations in many countries and used in several studies focusing on the psychosocial consequences of infertility in Europe, Asia, and North America.
Methods: Over a period of two years, 596 infertile women and men took part in the study conducted at three German fertility clinics. Psychometric properties of FertiQoL were tested by performing confirmatory factor analyses, calculating average variance extracted values, reliability and correlation coefficients. Hierarchical regression analyses were conducted to determine the relations between FertiQoL subscales and both sociodemographic and medical variables. Individual and cross-partner effects were tested for.
Results: The confirmatory factor analyses conducted on our FertiQoL data supported the original four-factor solution for both women and men but, resulted in some unsatisfactory indices. Family and friends’ support items loaded weakly on the Social subscale of FertiQoL (.27 and .34 in women, .32 and .19 in men). The Emotional and Mind/Body subscales revealed a strong intercorrelation (r = .77, p < .001 in women, r = .74, p < .001 in men). Women scored lower than men on the Emotional and Mind/Body subscales only, and they reported better fertility-specific relational QoL. In women, the perceived cause of infertility and already mothering a child related significantly to individual FertiQoL scores, while in men, age, educational level, and the duration of their wish for a child had an impact on the FertiQoL subscales (all p < .05). The men’s educational level, the women’s educational level, and the subjective perceived medical cause of fertility problems exerted cross-partner effects on QoL (all p < .05).
Conclusions: Our study results represent a contribution both to research and clinical practice. The findings suggest the importance of considering the personal experience of infertility in different cultural and gender specific settings and that the strong connections between the emotional, physical, and cognitive aspects of an individual’s fertility-specific quality of life should be regarded as a more coherent system.
Trial registration DRKS: DRKS00014707.
Registered: 1 May 2018 (retrospectively registered)
Dark energy with gravitational lens time delays
Strong lensing gravitational time delays are a powerful and cost effective
probe of dark energy. Recent studies have shown that a single lens can provide
a distance measurement with 6-7 % accuracy (including random and systematic
uncertainties), provided sufficient data are available to determine the time
delay and reconstruct the gravitational potential of the deflector.
Gravitational-time delays are a low redshift (z~0-2) probe and thus allow one
to break degeneracies in the interpretation of data from higher-redshift probes
like the cosmic microwave background in terms of the dark energy equation of
state. Current studies are limited by the size of the sample of known lensed
quasars, but this situation is about to change. Even in this decade, wide field
imaging surveys are likely to discover thousands of lensed quasars, enabling
the targeted study of ~100 of these systems and resulting in substantial gains
in the dark energy figure of merit. In the next decade, a further order of
magnitude improvement will be possible with the 10000 systems expected to be
detected and measured with LSST and Euclid. To fully exploit these gains, we
identify three priorities. First, support for the development of software
required for the analysis of the data. Second, in this decade, small robotic
telescopes (1-4m in diameter) dedicated to monitoring of lensed quasars will
transform the field by delivering accurate time delays for ~100 systems. Third,
in the 2020's, LSST will deliver 1000's of time delays; the bottleneck will
instead be the aquisition and analysis of high resolution imaging follow-up.
Thus, the top priority for the next decade is to support fast high resolution
imaging capabilities, such as those enabled by the James Webb Space Telescope
and next generation adaptive optics systems on large ground based telescopes.Comment: White paper submitted to SNOWMASS201
COSMOGRAIL XVI: Time delays for the quadruply imaged quasar DES J0408-5354 with high-cadence photometric monitoring
We present time-delay measurements for the new quadruply imaged quasar DES
J0408-5354, the first quadruply imaged quasar found in the Dark Energy Survey
(DES). Our result is made possible by implementing a new observational strategy
using almost daily observations with the MPIA 2.2m telescope at La Silla
observatory and deep exposures reaching a signal-to-noise ratio of about 1000
per quasar image. This data quality allows us to catch small photometric
variations (a few mmag rms) of the quasar, acting on temporal scales much
shorter than microlensing, hence making the time delay measurement very robust
against microlensing. In only 7 months we measure very accurately one of the
time delays in DES J0408-5354: Dt(AB) = -112.1 +- 2.1 days (1.8%) using only
the MPIA 2.2m data. In combination with data taken with the 1.2m Euler Swiss
telescope, we also measure two delays involving the D component of the system
Dt(AD) = -155.5 +- 12.8 days (8.2%) and Dt(BD) = -42.4 +- 17.6 days (41%),
where all the error bars include systematics. Turning these time delays into
cosmological constraints will require deep HST imaging or ground-based Adaptive
Optics (AO), and information on the velocity field of the lensing galaxy.Comment: 9 pages, 5 figures, accepted for publication in Astronomy &
Astrophysic
Euclid Collaboration IV: Impact of Undetected Galaxies on Weak-Lensing Shear Measurements
In modern weak-lensing surveys, the common approach to correct for residual
systematic biases in the shear is to calibrate shape measurement algorithms
using simulations. These simulations must fully capture the complexity of the
observations to avoid introducing any additional bias. In this paper we study
the importance of faint galaxies below the observational detection limit of a
survey. We simulate simplified Euclid VIS images including and excluding this
faint population, and measure the shift in the multiplicative shear bias
between the two sets of simulations. We measure the shear with three different
algorithms: a moment-based approach, model fitting, and machine learning. We
find that for all methods, a spatially uniform random distribution of faint
galaxies introduces a shear multiplicative bias of the order of a few times
. This value increases to the order of when including the
clustering of the faint galaxies, as measured in the Hubble Space Telescope
Ultra-Deep Field. The magnification of the faint background galaxies due to the
brighter galaxies along the line of sight is found to have a negligible impact
on the multiplicative bias. We conclude that the undetected galaxies must be
included in the calibration simulations with proper clustering properties down
to magnitude 28 in order to reach a residual uncertainty on the multiplicative
shear bias calibration of a few times , in line with the
total accuracy budget required by the scientific objectives of
the Euclid survey. We propose two complementary methods for including faint
galaxy clustering in the calibration simulations.Comment: Version published in A&
Image analysis for cosmology: results from the GREAT10 Galaxy Challenge
In this paper, we present results from the weak-lensing shape measurement GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Galaxy Challenge. This marks an order of magnitude step change in the level of scrutiny employed in weak-lensing shape measurement analysis. We provide descriptions of each method tested and include 10 evaluation metrics over 24 simulation branches. GREAT10 was the first shape measurement challenge to include variable fields; both the shear field and the point spread function (PSF) vary across the images in a realistic manner. The variable fields enable a variety of metrics that are inaccessible to constant shear simulations, including a direct measure of the impact of shape measurement inaccuracies, and the impact of PSF size and ellipticity, on the shear power spectrum. To assess the impact of shape measurement bias for cosmic shear, we present a general pseudo-Câ„“ formalism that propagates spatially varying systematics in cosmic shear through to power spectrum estimates. We also show how one-point estimators of bias can be extracted from variable shear simulations. The GREAT10 Galaxy Challenge received 95 submissions and saw a factor of 3 improvement in the accuracy achieved by other shape measurement methods. The best methods achieve sub-per cent average biases. We find a strong dependence on accuracy as a function of signal-to-noise ratio, and indications of a weak dependence on galaxy type and size. Some requirements for the most ambitious cosmic shear experiments are met above a signal-to-noise ratio of 20. These results have the caveat that the simulated PSF was a ground-based PSF. Our results are a snapshot of the accuracy of current shape measurement methods and are a benchmark upon which improvement can be brought. This provides a foundation for a better understanding of the strengths and limitations of shape measurement method
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Bevacizumab in combination with biweekly capecitabine and irinotecan, as first-line treatment for patients with metastatic colorectal cancer
Aging and Error Processing: Age Related Increase in the Variability of the Error-Negativity Is Not Accompanied by Increase in Response Variability
Background: Several studies report an amplitude reduction of the error negativity (Ne or ERN), an event-related potential occurring after erroneous responses, in older participants. In earlier studies it was shown that the Ne can be explained by a single independent component. In the present study we aimed to investigate whether the Ne reduction usually found in older subjects is due to an altered component structure, i.e., a true alteration in response monitoring in older subjects. Methodology/Principal Findings: Two age groups conducted two tasks with different stimulus response mappings and task difficulty. Both groups received fully balanced speed or accuracy instructions and an individually adapted deadline in both tasks. Event-related potentials, Independent Component analysis of EEG-data and between trial variability of the Ne were combined with analysis of error rates, coefficients of variation of RT-data and ex-Gaussian fittings to reaction times. The Ne was examined by means of ICA and PCA, yielding a prominent independent component on error trials, the Ne-IC. The Ne-IC was smaller in the older than the younger subjects for both speed and accuracy instructions. Also, the Ne-IC contributed to a much lesser extent to the Ne in older than in younger subjects. RT distribution parameters were not related to Ne/ERP-variability. Conclusions/Significance: The results show a genuine reduction as well as a different component structure of the Ne in older compared to young subjects. This reduction is not reflected in behaviour, apart from a general slowing of olde
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