363 research outputs found
High-resolution imaging follow-up of doubly imaged quasars
We report upon three years of follow-up and confirmation of doubly imaged
quasar lenses through imaging campaigns from 2016-2018 with the Near-Infrared
Camera2 (NIRC2) on the W. M. Keck Observatory. A sample of 57 quasar lens
candidates are imaged in adaptive-optics-assisted or seeing-limited
-band observations. Out of these 57 candidates, 15 are confirmed as
lenses. We form a sample of 20 lenses adding in a number of previously-known
lenses that were imaged with NIRC2 in 2013-14 as part of a pilot study. By
modelling these 20 lenses, we obtain -band relative photometry and
astrometry of the quasar images and the lens galaxy. We also provide the lens
properties and predicted time delays to aid planning of follow-up observations
necessary for various astrophysical applications, e.g., spectroscopic follow-up
to obtain the deflector redshifts for the newly confirmed systems. We compare
the departure of the observed flux ratios from the smooth-model predictions
between doubly and quadruply imaged quasar systems. We find that the departure
is consistent between these two types of lenses if the modelling uncertainty is
comparable.Comment: 11 pages, 8 figures, 5 tables. This version: accepted to MNRA
Recommended from our members
H0LiCOW X: Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI2033-4723
Galaxies and galaxy groups located along the line of sight towards
gravitationally lensed quasars produce high-order perturbations of the
gravitational potential at the lens position. When these perturbation are too
large, they can induce a systematic error on of a few-percent if the lens
system is used for cosmological inference and the perturbers are not explicitly
accounted for in the lens model. In this work, we present a detailed
characterization of the environment of the lens system WFI2033-4723 (, = 0.6575), one of the core targets of the H0LICOW
project for which we present cosmological inferences in a companion paper (Rusu
et al. 2019). We use the Gemini and ESO-Very Large telescopes to measure the
spectroscopic redshifts of the brightest galaxies towards the lens, and use the
ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the
lens ( km/s) and of several nearby
galaxies. In addition, we measure photometric redshifts and stellar masses of
all galaxies down to mag, mainly based on Dark Energy Survey imaging
(DR1). Our new catalog, complemented with literature data, more than doubles
the number of known galaxy spectroscopic redshifts in the direct vicinity of
the lens, expanding to 116 (64) the number of spectroscopic redshifts for
galaxies separated by less than 3 arcmin (2 arcmin) from the lens. Using the
flexion-shift as a measure of the amplitude of the gravitational perturbation,
we identify 2 galaxy groups and 3 galaxies that require specific attention in
the lens models. The ESO MUSE data enable us to measure the
velocity-dispersions of three of these galaxies. These results are essential
for the cosmological inference analysis presented in Rusu et al. (2019).Comment: Matches the version accepted for publication by MNRAS. Note that this
paper previously appeared as H0LICOW X
Gas Accretion and Galactic Chemical Evolution: Theory and Observations
This chapter reviews how galactic inflows influence galaxy metallicity. The
goal is to discuss predictions from theoretical models, but particular emphasis
is placed on the insights that result from using models to interpret
observations. Even as the classical G-dwarf problem endures in the latest round
of observational confirmation, a rich and tantalizing new phenomenology of
relationships between , , SFR, and gas fraction is emerging both in
observations and in theoretical models. A consensus interpretation is emerging
in which star-forming galaxies do most of their growing in a quiescent way that
balances gas inflows and gas processing, and metal dilution with enrichment.
Models that explicitly invoke this idea via equilibrium conditions can be used
to infer inflow rates from observations, while models that do not assume
equilibrium growth tend to recover it self-consistently. Mergers are an overall
subdominant mechanism for delivering fresh gas to galaxies, but they trigger
radial flows of previously-accreted gas that flatten radial gas-phase
metallicity gradients and temporarily suppress central metallicities. Radial
gradients are generically expected to be steep at early times and then
flattened by mergers and enriched inflows of recycled gas at late times.
However, further theoretical work is required in order to understand how to
interpret observations. Likewise, more observational work is needed in order to
understand how metallicity gradients evolve to high redshifts.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springer. 29 pages, 2 figure
Unveiling the Universe with emerging cosmological probes
The detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (Cosmic Microwave Background, Supernovae Type Ia, Baryon Acoustic Oscillations) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmological model. In parallel to that, however, the percent precision achieved has recently revealed apparent tensions between measurements obtained from different methods. These are either indicating some unaccounted systematic effects, or are pointing toward new physics. Following the development of CMB, SNe, and BAO cosmology, it is critical to extend our selection of cosmological probes. Novel probes can be exploited to validate results, control or mitigate systematic effects, and, most importantly, to increase the accuracy and robustness of our results. This review is meant to provide a state-of-art benchmark of the latest advances in emerging “beyond-standard” cosmological probes. We present how several different methods can become a key resource for observational cosmology. In particular, we review cosmic chronometers, quasars, gamma-ray bursts, standard sirens, lensing time-delay with galaxies and clusters, cosmic voids, neutral hydrogen intensity mapping, surface brightness fluctuations, stellar ages of the oldest objects, secular redshift drift, and clustering of standard candles. The review describes the method, systematics, and results of each probe in a homogeneous way, giving the reader a clear picture of the available innovative methods that have been introduced in recent years and how to apply them. The review also discusses the potential synergies and complementarities between the various probes, exploring how they will contribute to the future of modern cosmology
Double dark matter vision: Twice the number of compact-source lenses with narrow-line lensing and the WFC3 grism
Indexación: Scopus.The magnifications of compact-source lenses are extremely sensitive to the presence of lowmass darkmatter haloes along the entire sightline from the source to the observer. Traditionally, the study of darkmatter structure in compact-source strong gravitational lenses has been limited to radio-loud systems, as the radio emission is extended and thus unaffected by microlensing which can mimic the signal of dark matter structure. An alternate approach is to measure quasar nuclear-narrow-line emission, which is free from microlensing and present in virtually all quasar lenses. In this paper, we double the number of systems which can be used for gravitational lensing analyses by presenting measurements of narrow-line emission from a sample of eight quadruply imaged quasar lens systems, WGD J0405-3308, HS 0810+2554, RX J0911+0551, SDSS J1330+1810, PS J1606-2333, WFI 2026-4536, WFI 2033-4723, and WGD J2038-4008. We describe our updated grism spectral modelling pipeline, which we use to measure narrow-line fluxes with uncertainties of 2-10 per cent, presented here. We fit the lensed image positions with smooth mass models and demonstrate that these models fail to produce the observed distribution of image fluxes over the entire sample of lenses. Furthermore, typical deviations are larger than those expected from macromodel uncertainties. This discrepancy indicates the presence of perturbations caused by small-scale dark matter structure. The interpretation of this result in terms of dark matter models is presented in a companion paper.https://academic.oup.com/mnras/article/492/4/5314/568672
Rucaparib maintenance treatment for recurrent ovarian carcinoma after response to platinum therapy (ARIEL3): a randomised, double-blind, placebo-controlled, phase 3 trial
Background:
Rucaparib, a poly(ADP-ribose) polymerase inhibitor, has anticancer activity in recurrent ovarian carcinoma harbouring a BRCA mutation or high percentage of genome-wide loss of heterozygosity. In this trial we assessed rucaparib versus placebo after response to second-line or later platinum-based chemotherapy in patients with high-grade, recurrent, platinum-sensitive ovarian carcinoma.
Methods:
In this randomised, double-blind, placebo-controlled, phase 3 trial, we recruited patients from 87 hospitals and cancer centres across 11 countries. Eligible patients were aged 18 years or older, had a platinum-sensitive, high-grade serous or endometrioid ovarian, primary peritoneal, or fallopian tube carcinoma, had received at least two previous platinum-based chemotherapy regimens, had achieved complete or partial response to their last platinum-based regimen, had a cancer antigen 125 concentration of less than the upper limit of normal, had a performance status of 0–1, and had adequate organ function. Patients were ineligible if they had symptomatic or untreated central nervous system metastases, had received anticancer therapy 14 days or fewer before starting the study, or had received previous treatment with a poly(ADP-ribose) polymerase inhibitor. We randomly allocated patients 2:1 to receive oral rucaparib 600 mg twice daily or placebo in 28 day cycles using a computer-generated sequence (block size of six, stratified by homologous recombination repair gene mutation status, progression-free interval after the penultimate platinum-based regimen, and best response to the most recent platinum-based regimen). Patients, investigators, site staff, assessors, and the funder were masked to assignments. The primary outcome was investigator-assessed progression-free survival evaluated with use of an ordered step-down procedure for three nested cohorts: patients with BRCA mutations (carcinoma associated with deleterious germline or somatic BRCA mutations), patients with homologous recombination deficiencies (BRCA mutant or BRCA wild-type and high loss of heterozygosity), and the intention-to-treat population, assessed at screening and every 12 weeks thereafter. This trial is registered with ClinicalTrials.gov, number NCT01968213; enrolment is complete.
Findings:
Between April 7, 2014, and July 19, 2016, we randomly allocated 564 patients: 375 (66%) to rucaparib and 189 (34%) to placebo. Median progression-free survival in patients with a BRCA-mutant carcinoma was 16·6 months (95% CI 13·4–22·9; 130 [35%] patients) in the rucaparib group versus 5·4 months (3·4–6·7; 66 [35%] patients) in the placebo group (hazard ratio 0·23 [95% CI 0·16–0·34]; p<0·0001). In patients with a homologous recombination deficient carcinoma (236 [63%] vs 118 [62%]), it was 13·6 months (10·9–16·2) versus 5·4 months (5·1–5·6; 0·32 [0·24–0·42]; p<0·0001). In the intention-to-treat population, it was 10·8 months (8·3–11·4) versus 5·4 months (5·3–5·5; 0·36 [0·30–0·45]; p<0·0001). Treatment-emergent adverse events of grade 3 or higher in the safety population (372 [99%] patients in the rucaparib group vs 189 [100%] in the placebo group) were reported in 209 (56%) patients in the rucaparib group versus 28 (15%) in the placebo group, the most common of which were anaemia or decreased haemoglobin concentration (70 [19%] vs one [1%]) and increased alanine or aspartate aminotransferase concentration (39 [10%] vs none).
Interpretation:
Across all primary analysis groups, rucaparib significantly improved progression-free survival in patients with platinum-sensitive ovarian cancer who had achieved a response to platinum-based chemotherapy. ARIEL3 provides further evidence that use of a poly(ADP-ribose) polymerase inhibitor in the maintenance treatment setting versus placebo could be considered a new standard of care for women with platinum-sensitive ovarian cancer following a complete or partial response to second-line or later platinum-based chemotherapy.
Funding:
Clovis Oncology
Time Delay Lens Modelling Challenge
In recent years, breakthroughs in methods and data have enabled gravitational
time delays to emerge as a very powerful tool to measure the Hubble constant
. However, published state-of-the-art analyses require of order 1 year of
expert investigator time and up to a million hours of computing time per
system. Furthermore, as precision improves, it is crucial to identify and
mitigate systematic uncertainties. With this time delay lens modelling
challenge we aim to assess the level of precision and accuracy of the modelling
techniques that are currently fast enough to handle of order 50 lenses, via the
blind analysis of simulated datasets. The results in Rung 1 and Rung 2 show
that methods that use only the point source positions tend to have lower
precision () while remaining accurate. In Rung 2, the methods that
exploit the full information of the imaging and kinematic datasets can recover
within the target accuracy () and precision ( per
system), even in the presence of poorly known point spread function and complex
source morphology. A post-unblinding analysis of Rung 3 showed the numerical
precision of the ray-traced cosmological simulations to be insufficient to test
lens modelling methodology at the percent level, making the results difficult
to interpret. A new challenge with improved simulations is needed to make
further progress in the investigation of systematic uncertainties. For
completeness, we present the Rung 3 results in an appendix, and use them to
discuss various approaches to mitigating against similar subtle data generation
effects in future blind challenges.Comment: 23 pages, 12 figures, 6 tables, MNRAS accepte
The Spectrometer/Telescope for Imaging X-rays (STIX)
Aims. The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and therefore provides diagnostics of the hottest (⪆10 MK) flare plasma while quantifying the location, spectrum, and energy content of flare-accelerated nonthermal electrons.
Methods. To accomplish this, STIX applies an indirect bigrid Fourier imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated CdTe detectors to provide information on angular scales from 7 to 180 arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of STIX has intrinsically low telemetry and it is therefore well-suited to the limited resources available to the Solar Orbiter payload. To further reduce the downlinked data volume, STIX data are binned on board into 32 selectable energy bins and dynamically-adjusted time bins with a typical duration of 1 s during flares.
Results. Through hard X-ray diagnostics, STIX provides critical information for understanding the acceleration of electrons at the Sun and their transport into interplanetary space and for determining the magnetic connection of Solar Orbiter back to the Sun. In this way, STIX serves to link Solar Orbiter’s remote and in-situ measurements
TDCOSMO:IV. Hierarchical time-delay cosmography – joint inference of the Hubble constant and galaxy density profiles
The H0LiCOW collaboration inferred via gravitational lensing time delays a
Hubble constant km s, describing
deflector mass density profiles by either a power-law or stars plus standard
dark matter halos. The mass-sheet transform (MST) that leaves the lensing
observables unchanged is considered the dominant source of residual uncertainty
in . We quantify any potential effect of the MST with flexible mass models
that are maximally degenerate with H0. Our calculation is based on a new
hierarchical approach in which the MST is only constrained by stellar
kinematics. The approach is validated on hydrodynamically simulated lenses. We
apply the method to the TDCOSMO sample of 7 lenses (6 from H0LiCOW) and measure
km s. In order to further
constrain the deflector mass profiles, we then add imaging and spectroscopy for
33 strong gravitational lenses from the SLACS sample. For 9 of the SLAC lenses
we use resolved kinematics to constrain the stellar anisotropy. From the joint
analysis of the TDCOSMO+SLACS sample, we measure km
s, assuming that the TDCOSMO and SLACS galaxies are drawn
from the same parent population. The blind H0LiCOW, TDCOSMO-only and
TDCOSMO+SLACS analyses are in mutual statistical agreement. The TDCOSMO+SLACS
analysis prefers marginally shallower mass profiles than H0LiCOW or
TDCOSMO-only. While our new analysis does not statistically invalidate the mass
profile assumptions by H0LiCOW, and thus their measurement relying on
those, it demonstrates the importance of understanding the mass density profile
of elliptical galaxies. The uncertainties on derived in this paper can be
reduced by physical or observational priors on the form of the mass profile, or
by additional data, chiefly spatially resolved kinematics of lens galaxies.Comment: accepted by A&A. Full analysis available at
https://github.com/TDCOSMO/hierarchy_analysis_2020_public updated permanent
analysis script link
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