37 research outputs found
Microlensing Constraints on Broad Absorption and Emission Line Flows in the Quasar H1413+117
We present new integral field spectroscopy of the gravitationally lensed
broad absorption line (BAL) quasar H1413+117, covering the ultraviolet to
visible rest-frame spectral range. We observe strong microlensing signatures in
lensed image D, and we use this microlensing to simultaneously constrain both
the broad emission and broad absorption line gas. By modeling the lens system
over the range of probable lensing galaxy redshifts and using on a new argument
based on the wavelength-independence of the broad line lensing magnifications,
we determine that there is no significant broad line emission from smaller than
~20 light days. We also perform spectral decomposition to derive the intrinsic
broad emission line (BEL) and continuum spectrum, subject to BAL absorption. We
also reconstruct the intrinsic BAL absorption profile, whose features allow us
to constrain outflow kinematics in the context of a disk-wind model. We find a
very sharp, blueshifted onset of absorption of 1,500 km/s in both C IV and N V
that may correspond to an inner edge of a disk-wind's radial outflow. The lower
ionization Si IV and Al III have higher-velocity absorption onsets, consistent
with a decreasing ionization parameter with radius in an accelerating outflow.
There is evidence of strong absorption in the BEL component which indicates a
high covering factor for absorption over two orders of magnitude in outflow
radius.Comment: 29 pages, 8 figure
The Most Powerful Lenses in the Universe: Quasar Microlensing as a Probe of the Lensing Galaxy
Optical and X-ray observations of strongly gravitationally lensed quasars
(especially when four separate images of the quasar are produced) determine not
only the amount of matter in the lensing galaxy but also how much is in a
smooth component and how much is composed of compact masses (e.g., stars,
stellar remnants, primordial black holes, CDM sub-halos, and planets). Future
optical surveys will discover hundreds to thousands of quadruply lensed
quasars, and sensitive X-ray observations will unambiguously determine the
ratio of smooth to clumpy matter at specific locations in the lensing galaxies
and calibrate the stellar mass fundamental plane, providing a determination of
the stellar . A modest observing program with a sensitive, sub-arcsecond
X-ray imager, combined with the planned optical observations, can make those
determinations for a large number (hundreds) of the lensing galaxies, which
will span a redshift range of Comment: Astro2020 Science White Pape
Latent Stochastic Differential Equations for Modeling Quasar Variability and Inferring Black Hole Properties
Active galactic nuclei (AGN) are believed to be powered by the accretion of
matter around supermassive black holes at the centers of galaxies. The
variability of an AGN's brightness over time can reveal important information
about the physical properties of the underlying black hole. The temporal
variability is believed to follow a stochastic process, often represented as a
damped random walk described by a stochastic differential equation (SDE). With
upcoming wide-field surveys set to observe 100 million AGN in multiple bandpass
filters, there is a need for efficient and automated modeling techniques that
can handle the large volume of data. Latent SDEs are well-suited for modeling
AGN time series data, as they can explicitly capture the underlying stochastic
dynamics. In this work, we modify latent SDEs to jointly reconstruct the
unobserved portions of multivariate AGN light curves and infer their physical
properties such as the black hole mass. Our model is trained on a realistic
physics-based simulation of ten-year AGN light curves, and we demonstrate its
ability to fit AGN light curves even in the presence of long seasonal gaps and
irregular sampling across different bands, outperforming a multi-output
Gaussian process regression baseline.Comment: 10 pages, 5 figures, accepted at the ICLR 2023 Workshop on Physics
for Machine Learnin
The HST Survey of BL Lac Objects: Gravitational Lens Candidates and Other Unusual Sources
We present HST observations of seven unusual objects from the HST ``snapshot
survey'' of BL Lac objects, of which four are gravitational lens candidates. In
three cases a double point sources is observed: 0033+595, with 1.58 arcsec
separation, and 0502+675 and 1440+122, each with arcsec separation.
The last two also show one or more galaxies, which could be either host or
lensing galaxies. If any are confirmed as lenses, these BL Lac objects are
excellent candidates for measuring H via gravitational time delay because
of their characteristic rapid, high amplitude variability. An additional
advantage is that, like other blazars, they are likely superluminal radio
sources, in which case the source plane is mapped out over a period of years,
providing strong additional constraints on the lensing mass distribution. The
fourth gravitational lens candidate is 1517+656, which is surrounded by three
arclets forming an almost perfect ring of radius 2.4 arcsec. If this is indeed
an Einstein ring, it is most likely a background source gravitationally lensed
by the BL Lac object host galaxy and possibly a surrounding group or cluster.
In the extreme case that all four candidates are true lenses, the derived
frequency of gravitational lensing in this BL Lac sample would be an order of
magnitude higher than in comparable quasar samples.
We also report on three other remarkable BL Lac objects: 0138-097, which is
surrounded by a large number of close companion galaxies; 0806+524, whose host
galaxy contains an uncommon arc-like structure; and 1959+650, which is hosted
by a gas rich elliptical galaxy with a prominent dust lane of .Comment: 29 pages in total, 12 figure
Selection of eligible participants for screening for lung cancer using primary care data
Lung cancer screening is effective if offered to people at increased risk of the disease. Currently, direct contact with potential participants is required for evaluating risk. A way to reduce the number of ineligible people contacted might be to apply risk-prediction models directly to digital primary care data, but model performance in this setting is unknown.Method: The Clinical Practice Research Datalink, a computerised, longitudinal primary care database, was used to evaluate the LLPv2 and PLCOm2012 models. Lung cancer occurrence over 5-6 years was measured in ever-smokers aged 50-80 years and compared with 5-year (LLPv2) and 6-year (PLCOm2012) predicted risk. Results: Over 5 and 6 years, 7,123 and 7,876 lung cancers occurred respectively from a cohort of 842,109 ever smokers. After recalibration, LLPV2 produced a c-statistic of 0.700 (0.694-0.710) but mean predicted risk was over-estimated (predicted: 4.61%, actual: 0.9%). PLCOm2012 showed similar performance (c-statistic: 0.679 (0.673–0.685), predicted risk: 3.76%. Applying risk-thresholds of 1% (LLPv2) and 0.15% (PLCOm2012), would avoid contacting 42.7% and 27.4% of ever-smokers who did not develop lung cancer for screening eligibility assessment, at the cost of missing 15.6% and 11.4% of lung cancers.Conclusion: Risk-prediction models showed only moderate discrimination when applied to routinely collected primary care data, which may be explained by quality and completeness of data. However, they may substantially reduce the number of people for initial evaluation of screening eligibility, at the cost of missing some lung cancers. Further work is needed to establish whether newer models have improved performance in primary care data
Risk of COVID-19 death for people with a pre-existing cancer diagnosis prior to COVID-19-vaccination : A systematic review and meta-analysis
Research Funding National Health and Medical Research Council. Grant Number: APP1194679 World Health Organization Article Funding Open access publishing facilitated by The University of Sydney, as part of the Wiley - The University of Sydney agreement via the Council of Australian University Librarians.Peer reviewedPublisher PD
Risk of COVID-19 death for people with a pre-existing cancer diagnosis prior to COVID-19-vaccination:A systematic review and meta-analysis
While previous reviews found a positive association between pre-existing cancer diagnosis and COVID-19-related death, most early studies did not distinguish long-term cancer survivors from those recently diagnosed/treated, nor adjust for important confounders including age. We aimed to consolidate higher-quality evidence on risk of COVID-19-related death for people with recent/active cancer (compared to people without) in the pre-COVID-19-vaccination period. We searched the WHO COVID-19 Global Research Database (20 December 2021), and Medline and Embase (10 May 2023). We included studies adjusting for age and sex, and providing details of cancer status. Risk-of-bias assessment was based on the Newcastle-Ottawa Scale. Pooled adjusted odds or risk ratios (aORs, aRRs) or hazard ratios (aHRs) and 95% confidence intervals (95% CIs) were calculated using generic inverse-variance random-effects models. Random-effects meta-regressions were used to assess associations between effect estimates and time since cancer diagnosis/treatment. Of 23 773 unique title/abstract records, 39 studies were eligible for inclusion (2 low, 17 moderate, 20 high risk of bias). Risk of COVID-19-related death was higher for people with active or recently diagnosed/treated cancer (general population: aOR = 1.48, 95% CI: 1.36-1.61, I2 = 0; people with COVID-19: aOR = 1.58, 95% CI: 1.41-1.77, I2 = 0.58; inpatients with COVID-19: aOR = 1.66, 95% CI: 1.34-2.06, I2 = 0.98). Risks were more elevated for lung (general population: aOR = 3.4, 95% CI: 2.4-4.7) and hematological cancers (general population: aOR = 2.13, 95% CI: 1.68-2.68, I2 = 0.43), and for metastatic cancers. Meta-regression suggested risk of COVID-19-related death decreased with time since diagnosis/treatment, for example, for any/solid cancers, fitted aOR = 1.55 (95% CI: 1.37-1.75) at 1 year and aOR = 0.98 (95% CI: 0.80-1.20) at 5 years post-cancer diagnosis/treatment. In conclusion, before COVID-19-vaccination, risk of COVID-19-related death was higher for people with recent cancer, with risk depending on cancer type and time since diagnosis/treatment.</p