1,965 research outputs found
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
Magnetic Order in the 2D Heavy-Fermion System CePt2In7 studied by muSR
The low-temperature microscopic magnetic properties of the quasi-2D
heavyfermion compound, CePt2In7 are investigated by using a positive muon-spin
rotation and relaxation (?muSR) technique. Clear evidence for the formation of
a commensurate antiferromagnetic order below TN=5.40 K is presented. The
magnetic order parameter is shown to fit well to a modified BSC gap-energy
function in a strong-coupling scenario.Comment: Accepted in Journal of Physics: Conference Series (2014
Testing the Evolution of the Correlations between Supermassive Black Holes and their Host Galaxies using Eight Strongly Lensed Quasars
One of the main challenges in using high redshift active galactic nuclei to
study the correlations between the mass of the supermassive Black Hole (MBH)
and the properties of their active host galaxies is instrumental resolution.
Strong lensing magnification effectively increases instrumental resolution and
thus helps to address this challenge. In this work, we study eight strongly
lensed active galactic nuclei (AGN) with deep Hubble Space Telescope imaging,
using the lens modelling code Lenstronomy to reconstruct the image of the
source. Using the reconstructed brightness of the host galaxy, we infer the
host galaxy stellar mass based on stellar population models. MBH are estimated
from broad emission lines using standard methods. Our results are in good
agreement with recent work based on non-lensed AGN, demonstrating the potential
of using strongly lensed AGNs to extend the study of the correlations to higher
redshifts. At the moment, the sample size of lensed AGN is small and thus they
provide mostly a consistency check on systematic errors related to resolution
for the non-lensed AGN. However, the number of known lensed AGN is expected to
increase dramatically in the next few years, through dedicated searches in
ground and space based wide field surveys, and they may become a key diagnostic
of black hole and galaxy co-evolution.Comment: 12 pages, 4 figures, 3 tables. MNRAS in press. Comments welcom
A proposal for a new type of thin-film field-emission display by edge breakdown of MIS structure
A new type of field emission display(FED) based on an edge-enhance electron
emission from metal-insulator-semiconductor (MIS) thin film structure is
proposed. The electrons produced by an avalanche breakdown in the semiconductor
near the edge of a top metal electrode are initially injected to the thin film
of an insulator with a negative electron affinity (NEA), and then are injected
into vacuum in proximity to the top electrode edge. The condition for the
deep-depletition breakdown near the edge of the top metal electrode is
analytically found in terms of ratio of the insulator thickness to the maximum
(breakdown) width of the semiconductor depletition region: this ratio should be
less than 2/(3 \pi - 2) = 0.27. The influence of a neighboring metal electrode
and an electrode thickness on this condition are analyzed. Different practical
schemes of the proposed display with a special reference to M/CaF_2/Si
structure are considered.Comment: 11 pages, 5 figure
Level-3 Calorimetric Resolution available for the Level-1 and Level-2 CDF Triggers
As the Tevatron luminosity increases sophisticated selections are required to
be efficient in selecting rare events among a very huge background. To cope
with this problem, CDF has pushed the offline calorimeter algorithm
reconstruction resolution up to Level 2 and, when possible, even up to Level 1,
increasing efficiency and, at the same time, keeping under control the rates.
The CDF Run II Level 2 calorimeter trigger is implemented in hardware and is
based on a simple algorithm that was used in Run I. This system has worked well
for Run II at low luminosity. As the Tevatron instantaneous luminosity
increases, the limitation due to this simple algorithm starts to become clear:
some of the most important jet and MET (Missing ET) related triggers have large
growth terms in cross section at higher luminosity. In this paper, we present
an upgrade of the Level 2 Calorimeter system which makes the calorimeter
trigger tower information available directly to a CPU allowing more
sophisticated algorithms to be implemented in software. Both Level 2 jets and
MET can be made nearly equivalent to offline quality, thus significantly
improving the performance and flexibility of the jet and MET related triggers.
However in order to fully take advantage of the new L2 triggering capabilities
having at Level 1 the same L2 MET resolution is necessary. The new Level-1 MET
resolution is calculated by dedicated hardware. This paper describes the
design, the hardware and software implementation and the performance of the
upgraded calorimeter trigger system both at Level 2 and Level 1.Comment: 5 pages, 5 figures,34th International Conference on High Energy
Physics, Philadelphia, 200
H0LiCOW III. Quantifying the effect of mass along the line of sight to the gravitational lens HE 0435-1223 through weighted galaxy counts
Based on spectroscopy and multiband wide-field observations of the
gravitationally lensed quasar HE 0435-1223, we determine the probability
distribution function of the external convergence for
this system. We measure the under/overdensity of the line of sight towards the
lens system and compare it to the average line of sight throughout the
universe, determined by using the CFHTLenS as a control field. Aiming to
constrain as tightly as possible, we determine
under/overdensities using various combinations of relevant informative weighing
schemes for the galaxy counts, such as projected distance to the lens,
redshift, and stellar mass. We then convert the measured under/overdensities
into a distribution, using ray-tracing through the
Millennium Simulation. We explore several limiting magnitudes and apertures,
and account for systematic and statistical uncertainties relevant to the
quality of the observational data, which we further test through simulations.
Our most robust estimate of has a median value
and a standard deviation of
. The measured corresponds to
uncertainty on the time delay distance, and hence the Hubble constant
inference from this system. The median value
is robust to (i.e. on ) regardless of the adopted
aperture radius, limiting magnitude and weighting scheme, as long as the latter
incorporates galaxy number counts, the projected distance to the main lens, and
a prior on the external shear obtained from mass modeling. The availability of
a well-constrained makes \hequad\ a valuable system for
measuring cosmological parameters using strong gravitational lens time delays.Comment: 24 pages, 17 figures, 6 tables. Submitted 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
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