1,900 research outputs found
Molecular Gas in the Powerful Radio Galaxies 3C~31 and 3C~264: Major or Minor Mergers?
We report the detection of CO~() and CO~()
emission from the central regions (--) of the two
powerful radio galaxies 3C~31 and 3C~264. Their individual CO emission exhibits
a double-horned line profile that is characteristic of an inclined rotating
disk with a central depression at the rising part of its rotation curve. The
inferred disk or ring distributions of the molecular gas is consistent with the
observed presence of dust disks or rings detected optically in the cores of
both galaxies. For a CO to H conversion factor similar to that of our
Galaxy, the corresponding total mass in molecular hydrogen gas is in 3C~31 and in 3C~264. Despite their relatively large molecular-gas masses
and other peculiarities, both 3C~31 and 3C~264, as well as many other powerful
radio galaxies in the (revised) 3C catalog, are known to lie within the
fundamental plane of normal elliptical galaxies. We reason that if their gas
originates from the mergers of two gas-rich disk galaxies, as has been invoked
to explain the molecular gas in other radio galaxies, then both 3C~31 and
3C~264 must have merged a long time (a few billion years or more) ago but their
remnant elliptical galaxies only recently (last tens of millions of years or
less) become active in radio. Instead, we argue that the cannibalism of
gas-rich galaxies provides a simpler explanation for the origin of molecular
gas in the elliptical hosts of radio galaxies. Given the transient nature of
their observed disturbances, these galaxies probably become active in radio
soon after the accretion event when sufficient molecular gas agglomerates in
their nuclei.Comment: 16 pages, 1 JPEG figure attached, accepted for publication in ApJ
Hubble Frontier Field Free-Form Mass Mapping of the Massive Multiple-Merging Cluster MACSJ0717.5+3745
We examine the latest data on the cluster MACSJ0717.5+3745 from the Hubble
Frontier Fields campaign. The critically lensed area is the largest known of
any lens and very irregular making it a challenge for parametric modelling.
Using our Free-Form method we obtain an accurate solution, identify here many
new sets of multiple images, doubling the number of constraints and improving
the reconstruction of the dark matter distribution. Our reconstructed mass map
shows several distinct central substructures with shallow density profiles,
clarifying earlier work and defining well the relation between the dark matter
distribution and the luminous and X-ray peaks within the critically lensed
region. Using our free-form method, we are able to meaningfully subtract the
mass contribution from cluster members to the deflection field to trace the
smoothly distributed cluster dark matter distribution. We find 4 distinct
concentrations, 3 of which are coincident with the luminous matter. The fourth
peak has a significant offset from both the closest luminous and X-ray peaks.
These findings, together with dynamical data from the motions of galaxies and
gas will be important for uncovering the potentially important implications of
this extremely massive and intriguing system.Comment: 16 pages, 10 figures, 2 tables. Matches the verson submitted to
mnras. New table (A2) included with additional system candidate
A Rigorous Free-form Lens Model of Abell 2744 to Meet the Hubble Frontier Fields Challenge
Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters
provides access to the most magnified distant galaxies. The challenge is to
construct lens models capable of describing these complex massive, merging
clusters so that individual lensed systems can be reliably identified and their
intrinsic properties accurately derived. We apply the free-form lensing method
(WSLAP+) to A2744, providing a model independent map of the cluster mass,
magnification, and geometric distance estimates to multiply-lensed sources. We
solve simultaneously for a smooth cluster component on a pixel grid, together
with local deflections by the cluster member galaxies. Combining model
prediction with photometric redshift measurements, we correct and complete
several systems recently claimed, and identify 4 new systems - totalling 65
images of 21 systems spanning a redshift range of 1.4<z<9.8. The reconstructed
mass shows small enhancements in the directions where significant amounts of
hot plasma can be seen in X-ray. We compare photometric redshifts with
"geometric redshifts", finding a high level of self-consistency. We find
excellent agreement between predicted and observed fluxes - with a best-fit
slope of 0.999+-0.013 and an RMS of ~0.25 mag, demonstrating that our
magnification correction of the lensed background galaxies is very reliable.
Intriguingly, few multiply-lensed galaxies are detected beyond z~7.0, despite
the high magnification and the limiting redshift of z~11.5 permitted by the HFF
filters. With the additional HFF clusters we can better examine the
plausibility of any pronounced high-z deficit, with potentially important
implications for the reionization epoch and the nature of dark matter.Comment: Accepted for publication in ApJ with newly identified lensed images
in complete HFF dat
A Free-Form Prediction for the Reappearance of Supernova Refsdal in the Hubble Frontier Fields Cluster MACSJ1149.5+2223
The massive cluster MACSJ1149.5+2223(z=0.544) displays five very large lensed
images of a well resolved spiral galaxy at . It is within
one of these images that the first example of a multiply-lensed supernova has
been detected recently as part of the Grism Lens-Amplified Survey from Space.
The depth of this data also reveals many HII regions within the lensed spiral
galaxy which we identify between the five counter-images. Here we expand the
capability of our free-form method to incorporate these HII regions locally,
with other reliable lensed galaxies added for a global solution. This improved
accuracy allows us to estimate when the Refsdal supernova will appear within
the other lensed images of the spiral galaxy to an accuracy of 7\%. We
predict this supernova will reappear in one of the counter-images
(RA=11:49:36.025, DEC=+22:23:48.11, J2000) and on November 1 2015 (with
an estimated error of 25 days) it will be at the same phase as it was
when it was originally discovered, offering a unique opportunity to study the
early phases of this supernova and to examine the consistency of the mass model
and the cosmological model that have an impact on the time delay prediction.Comment: 12 images, 11 pages. Mateches accepted version in MNRAS. MNRAS in
pres
Free-form lensing implications for the collision of dark matter and gas in the frontier fields cluster MACS J0416.1-2403
We present a free-form mass reconstruction of the massive lensing cluster MACS J0416.1-2403 using the latest Hubble Frontier Fields data. Our free-form method finds that the extended lensing pattern is generated by two elongated, closely projected clusters of similar mass. Our lens model identifies new lensed images with which we improve the accuracy of the dark matter distribution. We find that the bimodal mass distribution is nearly coincident with the bimodal X-ray emission, but with the two dark matter peaks lying closer together than the centroids of the X-ray emission. We can reproduce this behaviour with our hydrodynamical model, concluding that the clusters are significantly deflected around each other with the plane of the collision lying close to the line of sight. The projected mass profiles of both subclusters are well constrained in the region 30-165 kpc because of the many interior lensed images, leading to surprisingly flat mass profiles of both components at distances 30-100 kpc from the centre, in agreement with recent simulations of self-interacting dark matter. Using N-body simulations, we discuss the extent to which this may be generated by projection effects in our model as the cores graze each other. The relative velocity between the two cores is estimated to be about 1200 km s-1 and mostly along the line of sight so that our simulation is consistent with the relative redshift difference between the two cD galaxies (δz ≈ 0.04).JMD acknowledges support of the consolider project CAD2010-00064 and AYA2012-39475-C02-01 funded by the Ministerio de Economia y Competitividad.Peer Reviewe
Geometric Corroboration of the Earliest Lensed Galaxy at z ≃ 10.8 from Robust Free-form Modelling
A multiply lensed galaxy, MACS0647-JD, with a probable photometric redshift of z ≃ 10.7_(-0.4)^(+0.6) is claimed to constitute one of the very earliest known galaxies, formed well before reionization was completed. However, spectral evidence that MACS0647-JD lies at high redshift has proven infeasible and so here we seek an independent-lensing-based "geometric redshift" derived from the angles between the three lensed images of MACS0647-JD, using our free-form mass model (WSLAP+) for the lensing cluster MACSJ0647.7+7015 (at z = 0.591). Our lens model uses the nine sets of multiple images, including those of MACS0647-JD, identified by the CLASH survey toward this cluster. We convincingly exclude the low-redshift regime of z < 3, for which convoluted critical curves are generated by our method, as the solution bends to accommodate the wide angles of MACS0647-JD for this low redshift. Instead, a best fit to all sets of lensed galaxy positions and redshifts provides a geometric redshift of z≃ 10.8_(-0.4)^(+0.3) for MACS0647-JD, strongly supporting the higher photometric redshift solution. Importantly, we find a tight linear relation between the relative brightnesses of all nine sets of multiply lensed images and their relative magnifications as predicted by our model. This agreement provides a benchmark for the quality of the lens model, and establishes the robustness of our free-form lensing method for measuring model-independent geometric source distances and for deriving objective central cluster mass distributions. After correcting for its magnification the luminosity of MACS0647-JD remains relatively high at M UV = −19.4, which is within a factor of a few in flux of some surprisingly luminous z sime 10–11 candidates discovered recently in Hubble blank field surveys
Geometric Corroboration of the Earliest Lensed Galaxy at z ≃ 10.8 from Robust Free-form Modelling
A multiply lensed galaxy, MACS0647-JD, with a probable photometric redshift of z ≃ 10.7_(-0.4)^(+0.6) is claimed to constitute one of the very earliest known galaxies, formed well before reionization was completed. However, spectral evidence that MACS0647-JD lies at high redshift has proven infeasible and so here we seek an independent-lensing-based "geometric redshift" derived from the angles between the three lensed images of MACS0647-JD, using our free-form mass model (WSLAP+) for the lensing cluster MACSJ0647.7+7015 (at z = 0.591). Our lens model uses the nine sets of multiple images, including those of MACS0647-JD, identified by the CLASH survey toward this cluster. We convincingly exclude the low-redshift regime of z < 3, for which convoluted critical curves are generated by our method, as the solution bends to accommodate the wide angles of MACS0647-JD for this low redshift. Instead, a best fit to all sets of lensed galaxy positions and redshifts provides a geometric redshift of z≃ 10.8_(-0.4)^(+0.3) for MACS0647-JD, strongly supporting the higher photometric redshift solution. Importantly, we find a tight linear relation between the relative brightnesses of all nine sets of multiply lensed images and their relative magnifications as predicted by our model. This agreement provides a benchmark for the quality of the lens model, and establishes the robustness of our free-form lensing method for measuring model-independent geometric source distances and for deriving objective central cluster mass distributions. After correcting for its magnification the luminosity of MACS0647-JD remains relatively high at M UV = −19.4, which is within a factor of a few in flux of some surprisingly luminous z sime 10–11 candidates discovered recently in Hubble blank field surveys
Prevention, screening and treatment of colorectal cancer: a global and regional generalized cost effectiveness analysis
<p>Abstract</p> <p>Background</p> <p>Regional generalized cost-effectiveness estimates of prevention, screening and treatment interventions for colorectal cancer are presented.</p> <p>Methods</p> <p>Standardised WHO-CHOICE methodology was used. A colorectal cancer model was employed to provide estimates of screening and treatment effectiveness. Intervention effectiveness was determined via a population state-transition model (PopMod) that simulates the evolution of a sub-regional population accounting for births, deaths and disease epidemiology. Economic costs of procedures and treatment were estimated, including programme overhead and training costs.</p> <p>Results</p> <p>In regions characterised by high income, low mortality and high existing treatment coverage, the addition of screening to the current high treatment levels is very cost-effective, although no particular intervention stands out in cost-effectiveness terms relative to the others.</p> <p>In regions characterised by low income, low mortality with existing treatment coverage around 50%, expanding treatment with or without screening is cost-effective or very cost-effective. Abandoning treatment in favour of screening (no treatment scenario) would not be cost effective.</p> <p>In regions characterised by low income, high mortality and low treatment levels, the most cost-effective intervention is expanding treatment.</p> <p>Conclusions</p> <p>From a cost-effectiveness standpoint, screening programmes should be expanded in developed regions and treatment programmes should be established for colorectal cancer in regions with low treatment coverage.</p
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