24 research outputs found
Dark matter halos of massive elliptical galaxies at are well described by the Navarro-Frenk-White profile
We investigate the internal structure of elliptical galaxies at
from a joint lensing-dynamics analysis. We model Hubble Space Telescope images
of a sample of 23 galaxy-galaxy lenses selected from the Sloan Lens ACS (SLACS)
survey. Whereas the original SLACS analysis estimated the logarithmic slopes by
combining the kinematics with the imaging data, we estimate the logarithmic
slopes only from the imaging data. We find that the distribution of the
lensing-only logarithmic slopes has a median and intrinsic
scatter , consistent with the original SLACS analysis. We
combine the lensing constraints with the stellar kinematics and weak lensing
measurements, and constrain the amount of adiabatic contraction in the dark
matter (DM) halos. We find that the DM halos are well described by a standard
Navarro-Frenk-White halo with no contraction on average for both of a constant
stellar mass-to-light ratio () model and a stellar gradient model.
For the gradient model, we find that most galaxies are consistent with no
gradient. Comparison of our inferred stellar masses with those obtained
from the stellar population synthesis method supports a heavy initial mass
function (IMF) such as the Salpeter IMF. We discuss our results in the context
of previous observations and simulations, and argue that our result is
consistent with a scenario in which active galactic nucleus feedback
counteracts the baryonic-cooling-driven contraction in the DM halos.Comment: 26 pages, 19 figures, 3 tables. This version: accepted to MNRA
Strong lensing selection effects
Context. Strong lenses are a biased subset of the general population of
galaxies.
Aims. The goal of this work is to quantify how lens galaxies and lensed
sources differ from their parent distribution, namely the strong lensing bias.
Methods. We first studied how the strong lensing cross-section varies as a
function of lens and source properties. Then, we simulated strong lensing
surveys with data similar to that expected for Euclid and measured the strong
lensing bias in different scenarios. We focused particularly on two quantities:
the stellar population synthesis mismatch parameter, , defined as
the ratio between the true stellar mass of a galaxy and the stellar mass
obtained from photometry, and the central dark matter mass at fixed stellar
mass and size.
Results. Strong lens galaxies are biased towards larger stellar masses,
smaller half-mass radii and larger dark matter masses. The amplitude of the
bias depends on the intrinsic scatter in the mass-related parameters of the
galaxy population and on the completeness in Einstein radius of the lens
sample. For values of the scatter that are consistent with observed scaling
relations and a minimum detectable Einstein radius of , the strong
lensing bias in is , while that in the central dark matter
mass is . The bias has little dependence on the properties of the source
population: samples of galaxy-galaxy lenses and galaxy-quasar lenses that probe
the same Einstein radius distribution are biased in a very similar way.
Conclusions. Given current uncertainties, strong lensing observations can be
used directly to improve our current knowledge of the inner structure of
galaxies, without the need to correct for selection effects. Time-delay
measurements of from lensed quasars can take advantage of prior
information obtained from galaxy-galaxy lenses with similar Einstein radii.Comment: Published on Astronomy & Astrophysics. A two-minute summary video of
this paper is available at https://youtu.be/UmS9jRHTmZ
Measuring the Hubble Constant Near and Far in the Era of ELT's
Many of the fundamental physical constants in Physics, as a discipline, are
measured to exquisite levels of precision. The fundamental constants that
define Cosmology, however, are largely determined via a handful of independent
techniques that are applied to even fewer datasets. The history of the
measurement of the Hubble Constant (H0), which serves to anchor the expansion
history of the Universe to its current value, is an exemplar of the
difficulties of cosmological measurement; indeed, as we approach the centennial
of its first measurement, the quest for H0 still consumes a great number of
resources. In this white paper, we demonstrate how the approaching era of
Extremely Large Telescopes (ELTs) will transform the astrophysical measure of
H0 from the limited and few into a fundamentally new regime where (i) multiple,
independent techniques are employed with modest use of large aperture
facilities and (ii) 1% or better precision is readily attainable. This quantum
leap in how we approach H0 is due to the unparalleled sensitivity and spatial
resolution of ELT's and the ability to use integral field observations for
simultaneous spectroscopy and photometry, which together permit both familiar
and new techniques to effectively by-pass the conventional 'ladder' framework
to minimize total uncertainty. Three independent techniques are discussed --
(i) standard candles via a two-step distance ladder applied to metal, poor
stellar populations, (ii) standard clocks via gravitational lens cosmography,
and (iii) standard sirens via gravitational wave sources -- each of which can
reach 1% with relatively modest investment from 30-m class facilities.Comment: Submitted as an Astro2020 White Paper. Please send comments to both
Rachael Beaton & Simon Birrer. Development of this paper occurred as part of
the The US Extremely Large Telescope Program Workshop in Oct 2018. We wish to
acknowledge NOAO for bringing the co-authors together, in particular the
enthusiasm and tireless leadership of Mark Dickinso
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
H0LiCOW XII. Lens mass model of WFI2033-4723 and blind measurement of its time-delay distance and
We present the lens mass model of the quadruply-imaged gravitationally lensed
quasar WFI2033-4723, and perform a blind cosmographical analysis based on this
system. Our analysis combines (1) time-delay measurements from 14 years of data
obtained by the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL)
collaboration, (2) high-resolution imaging,
(3) a measurement of the velocity dispersion of the lens galaxy based on
ESO-MUSE data, and (4) multi-band, wide-field imaging and spectroscopy
characterizing the lens environment. We account for all known sources of
systematics, including the influence of nearby perturbers and complex
line-of-sight structure, as well as the parametrization of the light and mass
profiles of the lensing galaxy. After unblinding, we determine the effective
time-delay distance to be , an average
precision of . This translates to a Hubble constant , assuming a flat CDM
cosmology with a uniform prior on in the range [0.05, 0.5].
This work is part of the Lenses in COSMOGRAIL's Wellspring (H0LiCOW)
collaboration, and the full time-delay cosmography results from a total of six
strongly lensed systems are presented in a companion paper (H0LiCOW XIII).Comment: Version accepted by MNRAS. 29 pages including appendix, 17 figures, 6
tables. arXiv admin note: text overlap with arXiv:1607.0140
H_0 from Lensed Quasars
Strong gravitational lens systems with time delays between the multiple images are a powerful probe of cosmology, particularly of the Hubble constant (H0). The H0 Lenses In COSMOGRAIL's Wellspring (H0LiCOW) project has measured H0 from lensed quasars using deep Hubble Space Telescope and AO imaging, precise time delay measurements from the COSMOGRAIL monitoring project, a measurement of the velocity dispersion of the lens galaxies, and a characterization of the mass distribution along the line of sight. Our latest results from a total of six lenses constrains H0 to be 73.3(-1.8,+1.7) km/s/Mpc for a flat Lambda CDM cosmology, which is a measurement to 2.4% precision. These results are consistent with independent determinations of H0 using type Ia supernovae calibrated by the distance ladder method, and are in 3.1-sigma tension with the results of Planck CMB measurements. Combined with the latest distance ladder results from the SH0ES project, we find a 5.3-sigma tension between Planck and late-Universe probes, hinting at possible new physics beyond the standard LCDM model and highlighting the importance of this independent probe