94 research outputs found
TDCOSMO. XI. New lensing galaxy redshift and velocity dispersion measurements from Keck spectroscopy of eight lensed quasar systems
We have measured the redshifts and single-aperture velocity dispersions of
eight lens galaxies using the data collected by the Echellette Spectrograph and
Imager (ESI) and Low Resolution Imaging Spectrometer (LRIS) at W.M. Keck
observatory on different observing nights spread over three years (2018-2020).
These results, combined with other ancillary data, such as high-resolution
images of the lens systems, and time delays, are necessary to increase the
sample size of the quasar-galaxy lens systems for which the Hubble constant can
be measured, using the time-delay strong lensing method, hence increasing the
precision of its inference. Typically, the 2D spectra of the quasar-galaxy lens
systems get spatially blended due to seeing by ground-based observations. As a
result, the extracted lensing galaxy (deflector) spectra become significantly
contaminated by quasar light, which affects the ability to extract meaningful
information about the deflector. To account for spatial blending and extract
less contaminated and higher signal-to-noise ratio (S/N) 1D spectra of the
deflectors, a forward modeling method has been implemented. From the extracted
spectra, we have measured redshifts using prominent absorption lines and single
aperture velocity dispersions using the penalized pixel fitting code pPXF. In
this paper, we report the redshifts and single aperture velocity dispersions of
eight lens galaxies - J0147+4630, B0445+123, B0631+519, J0659+1629, J0818-2613,
J0924+0219, J1433+6007, and J1817+2729. Among these systems, six do not have
previously measured velocity dispersions; for the other two, our measurements
are consistent with previously reported values. Additionally, we have measured
the previously unknown redshifts of the deflectors in J0818-2613 and J1817+2729
to be and , respectively.Comment: 13 pages, 6 figures, 3 tables; accepted in A&
The Hubble Constant determined through an inverse distance ladder including quasar time delays and Type Ia supernovae
Context. The precise determination of the present-day expansion rate of the
Universe, expressed through the Hubble constant , is one of the most
pressing challenges in modern cosmology. Assuming flat CDM,
inference at high redshift using cosmic-microwave-background data from Planck
disagrees at the 4.4 level with measurements based on the local
distance ladder made up of parallaxes, Cepheids and Type Ia supernovae (SNe
Ia), often referred to as "Hubble tension". Independent,
cosmological-model-insensitive ways to infer are of critical importance.
Aims. We apply an inverse-distance-ladder approach, combining strong-lensing
time-delay-distance measurements with SN Ia data. By themselves, SNe Ia are
merely good relative distance indicators, but by anchoring them to strong
gravitational lenses one can obtain an measurement that is relatively
insensitive to other cosmological parameters. Methods. A cosmological parameter
estimate is performed for different cosmological background models, both for
strong-lensing data alone and for the combined lensing + SNe Ia data sets.
Results. The cosmological-model dependence of strong-lensing measurements
is significantly mitigated through the inverse distance ladder. In combination
with SN Ia data, the inferred consistently lies around 73-74 km s
Mpc, regardless of the assumed cosmological background model. Our
results agree nicely with those from the local distance ladder, but there is a
>2 tension with Planck results, and a ~1.5 discrepancy with
results from an inverse distance ladder including Planck, Baryon Acoustic
Oscillations and SNe Ia. Future strong-lensing distance measurements will
reduce the uncertainties in from our inverse distance ladder.Comment: 5 pages, 3 figures, A&A letters accepted versio
TDCOSMO XI. Automated Modeling of 9 Strongly Lensed Quasars and Comparison Between Lens Modeling Software
To use strong gravitational lenses as an astrophysical or cosmological probe,
models of their mass distributions are often needed. We present a new,
time-efficient automation code for uniform modeling of strongly lensed quasars
with GLEE, a lens modeling software, for high-resolution multi-band data. By
using the observed positions of the lensed quasars and the spatially extended
surface brightness distribution of the lensed quasar host galaxy, we obtain a
model of the mass distribution of the lens galaxy. We apply this uniform
modeling pipeline to a sample of nine strongly lensed quasars with HST WFC 3
images. The models show in most cases well reconstructed light components and a
good alignment between mass and light centroids. We find that the automated
modeling code significantly reduces the user input time during the modeling
process. The preparation time of required input files is reduced significantly.
This automated modeling pipeline can efficiently produce uniform models of
extensive lens system samples which can be used for further cosmological
analysis. A blind test through a comparison with the results of an independent
automated modeling pipeline based on the modeling software Lenstronomy reveals
important lessons. Quantities such as Einstein radius, astrometry, mass
flattening and position angle are generally robustly determined. Other
quantities depend crucially on the quality of the data and the accuracy of the
PSF reconstruction. Better data and/or more detailed analysis will be necessary
to elevate our automated models to cosmography grade. Nevertheless, our
pipeline enables the quick selection of lenses for follow-up monitoring and
further modeling, significantly speeding up the construction of
cosmography-grade models. This is an important step forward to take advantage
of the orders of magnitude increase in the number of lenses expected in the
coming decade.Comment: 36 pages, 13 figures, submitted to A&
STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408-5354
We present a blind time-delay cosmographic analysis for the lens system DES J0408-5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine the measured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the 'effective' time-delay distance corresponding to the redshifts of the deflector and the lensed quasar DΔ t eff=3382-115+146 Mpc and the angular diameter distance to the deflector Dd = 1711-280+376 Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H0= 74.2-3.0+2.7 km s-1 Mpc-1 assuming a flat ΛCDM cosmology and a uniform prior for ωm as \Omega m ∼ \mathcal {U(0.05, 0.5). This measurement gives the most precise constraint on H0 to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H0 Lenses in COSMOGRAIL's Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H0 based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
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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
H0LiCOW - IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant
We present a blind time-delay strong lensing (TDSL) cosmographic analysis of
the doubly imaged quasar SDSS 1206+4332. We combine the relative time delay
between the quasar images, Hubble Space Telescope imaging, the Keck stellar
velocity dispersion of the lensing galaxy, and wide-field photometric and
spectroscopic data of the field to constrain two angular diameter distance
relations. The combined analysis is performed by forward modelling the
individual data sets through a Bayesian hierarchical framework, and it is kept
blind until the very end to prevent experimenter bias. After unblinding, the
inferred distances imply a Hubble constant
kmsMpc, assuming a flat Lambda cold dark matter cosmology with
uniform prior on in [0.05, 0.5]. The precision of our
cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is
comparable with those of quadruply imaged quasars and opens the path to perform
on selected doubles the same analysis as anticipated for quads. Our analysis is
based on a completely independent lensing code than our previous three H0LiCOW
systems and the new measurement is fully consistent with those. We provide the
analysis scripts paired with the publicly available software to facilitate
independent analysis. The consistency between blind measurements with
independent codes provides an important sanity check on lens modelling
systematics. By combining the likelihoods of the four systems under the same
prior, we obtain kmsMpc. This
measurement is independent of the distance ladder and other cosmological
probes.Comment: 30 pages, 17 figures, MNRAS published likelihood available here:
http://shsuyu.github.io/H0LiCOW/site/notebooks/H0_from_lenses.html, all
modeling and analysis scripts available upon reques
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
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
LensWatch: I. Resolved HST Observations and Constraints on the Strongly-Lensed Type Ia Supernova 2022qmx ("SN Zwicky")
Supernovae (SNe) that have been multiply-imaged by gravitational lensing are
rare and powerful probes for cosmology. Each detection is an opportunity to
develop the critical tools and methodologies needed as the sample of lensed SNe
increases by orders of magnitude with the upcoming Vera C. Rubin Observatory
and Nancy Grace Roman Space Telescope. The latest such discovery is of the
quadruply-imaged Type Ia SN 2022qmx (aka, "SN Zwicky"; Goobar et al. 2022) at z
= 0.3544. SN Zwicky was discovered by the Zwicky Transient Facility (ZTF) in
spatially unresolved data. Here we present follow-up Hubble Space Telescope
observations of SN Zwicky, the first from the multi-cycle "LensWatch" program
(www.lenswatch.org). We measure photometry for each of the four images of SN
Zwicky, which are resolved in three WFC3/UVIS filters (F475W, F625W, F814W) but
unresolved with WFC3/IR F160W, and produce an analysis of the lensing system
using a variety of independent lens modeling methods. We find consistency
between time delays estimated with the single epoch of HST photometry and the
lens model predictions constrained through the multiple image positions, with
both inferring time delays of <1 day. Our lens models converge to an Einstein
radius of (0.168+0.009-0.005)", the smallest yet seen in a lensed SN. The
"standard candle" nature of SN Zwicky provides magnification estimates
independent of the lens modeling that are brighter by ~1.5 mag and ~0.8 mag for
two of the four images, suggesting significant microlensing and/or additional
substructure beyond the flexibility of our image-position mass models
TDCOSMO. IX. Systematic comparison between lens modelling software programs: time delay prediction for WGD 2038-4008
peer reviewedThe importance of alternative methods for measuring the Hubble constant, such
as time-delay cosmography, is highlighted by the recent Hubble tension. It is
paramount to thoroughly investigate and rule out systematic biases in all
measurement methods before we can accept new physics as the source of this
tension. In this study, we perform a check for systematic biases in the lens
modelling procedure of time-delay cosmography by comparing independent and
blind time-delay predictions of the system WGD 2038-4008 from two teams using
two different software programs: GLEE and LENSTRONOMY. The predicted time
delays from the two teams incorporate the stellar kinematics of the deflector
and the external convergence from line-of-sight structures. The un-blinded
time-delay predictions from the two teams agree within , implying
that once the time delay is measured the inferred Hubble constant will also be
mutually consistent. However, there is a 4 discrepancy between
the power-law model slope and external shear, which is a significant
discrepancy at the level of lens models before the stellar kinematics and the
external convergence are incorporated. We identify the difference in the
reconstructed point spread function (PSF) to be the source of this discrepancy.
When the same reconstructed PSF was used by both teams, we achieved excellent
agreement, within 0.6, indicating that potential systematics
stemming from source reconstruction algorithms and investigator choices are
well under control. We recommend that future studies supersample the PSF as
needed and marginalize over multiple algorithms or realizations for the PSF
reconstruction to mitigate the systematics associated with the PSF. A future
study will measure the time delays of the system WGD 2038-4008 and infer the
Hubble constant based on our mass models
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