200 research outputs found
Not In Our Backyard: Spectroscopic Support for the CLASH z=11 Candidate MACS0647-JD
We report on our first set of spectroscopic Hubble Space Telescope
observations of the z~11 candidate galaxy strongly lensed by the
MACSJ0647.7+7015 galaxy cluster. The three lensed images are faint and we show
that these early slitless grism observations are of sufficient depth to
investigate whether this high-redshift candidate, identified by its strong
photometric break at ~1.5 micron, could possibly be an emission line galaxy at
a much lower redshift. While such an interloper would imply the existence of a
rather peculiar object, we show here that such strong emission lines would
clearly have been detected. Comparing realistic, two-dimensional simulations to
these new observations we would expect the necessary emission lines to be
detected at >5 sigma while we see no evidence for such lines in the dispersed
data of any of the three lensed images. We therefore exclude that this object
could be a low redshift emission line interloper, which significantly increases
the likelihood of this candidate being a bona fide z~11 galaxy.Comment: 14 Pages. 6 Figures. 2nd revised version. Accepted. To appear in ApJ.
Please contact [email protected] for comments on this pape
Shock cooling of a red-supergiant supernova at redshift 3 in lensed images
The core-collapse supernova of a massive star rapidly brightens when a shock,
produced following the collapse of its core, reaches the stellar surface. As
the shock-heated star subsequently expands and cools, its early-time light
curve should have a simple dependence on the progenitor's size and therefore
final evolutionary state. Measurements of the progenitor's radius from early
light curves exist for only a small sample of nearby supernovae, and almost all
lack constraining ultraviolet observations within a day of explosion. The
several-day time delays and magnifying ability of galaxy-scale gravitational
lenses, however, should provide a powerful tool for measuring the early light
curves of distant supernovae, and thereby studying massive stellar populations
at high redshift. Here we analyse individual rest-frame
ultraviolet-through-optical exposures taken with the Hubble Space Telescope
that simultaneously capture, in three separate gravitationally lensed images,
the early phases of a supernova at redshift beginning within
hr of explosion. The supernova, seen at a lookback time of
billion years, is strongly lensed by an early-type galaxy in the
Abell 370 cluster. We constrain the pre-explosion radius to be
solar radii, consistent with a red supergiant. Highly
confined and massive circumstellar material at the same radius can also
reproduce the light curve, but is unlikely since no similar low-redshift
examples are known.Comment: 69 pages, 12 figures/tables (4 main text, 8 extended data). Published
in Natur
Flashlights: Properties of Highly Magnified Images Near Cluster Critical Curves in the Presence of Dark Matter Subhalos
Dark matter subhalos with extended profiles and density cores, and globular
stars clusters of mass , that live near the critical curves
in galaxy cluster lenses can potentially be detected through their lensing
magnification of stars in background galaxies. In this work we study the effect
such subhalos have on lensed images, and compare to the case of more well
studied microlensing by stars and black holes near critical curves. We find
that the cluster density gradient and the extended mass distribution of
subhalos are important in determining image properties. Both lead to an
asymmetry between the image properties on the positive and negative parity
sides of the cluster that is more pronounced than in the case of microlensing.
For example, on the negative parity side, subhalos with cores larger than about
pc do not generate any images with magnification above outside
of the immediate vicinity of the cluster critical curve. We discuss these
factors using analytical and numerical analysis, and exploit them to identify
observable signatures of subhalos: subhalos create pixel-to-pixel flux
variations of magnitudes, on the positive parity side of
clusters. These pixels tend to cluster around (otherwise invisible) subhalos.
Unlike in the case of microlensing, signatures of subhalo lensing can be found
up to away from the critical curves of massive clusters.Comment: ApJ, submitted, 21 pages, 17 figure
Searching for Highly Magnified Stars at Cosmological Distances: Discovery of a Redshift 0.94 Blue Supergiant in Archival Images of the Galaxy Cluster MACS J0416.1-2403
Individual highly magnified stars have been recently discovered at lookback
times of more than half the age of the Universe, in lensed galaxies that
straddle the critical curves of massive galaxy clusters. Having confirmed their
detectability, it is now important to carry out systematic searches for them in
order to establish their frequency, and in turn learn about the statistical
properties of high-redshift stars and of the granularity of matter in the
foreground deflector. Here we report the discovery of a highly magnified star
at redshift in a strongly lensed arc behind a Hubble Frontier Field
galaxy cluster, MACS J0416.1-2403, discovered as part of a systematic archival
search. The bright transient (dubbed "Warhol") was discovered in Hubble Space
Telescope data taken on 2014 September 15 and 16. This single image faded over
a period of two weeks, and observations taken on 2014 September 1 show that the
duration of the microlensing event was at most four weeks in total. The light
curve may also exhibit slow changes over a period of years consistent with the
level of microlensing expected from stars responsible for the intracluster
light (ICL) of the cluster. Optical and infrared observations taken near peak
brightness can be fit by a stellar spectrum with moderate host-galaxy
extinction. A blue supergiant matches the measured spectral energy distribution
near peak, implying a temporary magnification of at least several thousand.
While the spectrum of an O-type star would also fit the transient's spectral
energy distribution, extremely luminous O-type stars are much less common than
blue supergiants. The short timescale of the event and the estimated effective
temperature indicate that the lensed source is an extremely magnified star
Metabolomics enables precision medicine: “A White Paper, Community Perspective”
Introduction: Background to metabolomics: Metabolomics is the comprehensive study of the metabolome, the repertoire of biochemicals (or small molecules) present in cells, tissues, and body fluids. The study of metabolism at the global or “-omics” level is a rapidly growing field that has the potential to have a profound impact upon medical practice. At the center of metabolomics, is the concept that a person’s metabolic state provides a close representation of that individual’s overall health status. This metabolic state reflects what has been encoded by the genome, and modified by diet, environmental factors, and the gut microbiome. The metabolic profile provides a quantifiable readout of biochemical state from normal physiology to diverse pathophysiologies in a manner that is often not obvious from gene expression analyses. Today, clinicians capture only a very small part of the information contained in the metabolome, as they routinely measure only a narrow set of blood chemistry analytes to assess health and disease states. Examples include measuring glucose to monitor diabetes, measuring cholesterol and high density lipoprotein/low density lipoprotein ratio to assess cardiovascular health, BUN and creatinine for renal disorders, and measuring a panel of metabolites to diagnose potential inborn errors of metabolism in neonates. Objectives of White Paper—expected treatment outcomes and metabolomics enabling tool for precision medicine: We anticipate that the narrow range of chemical analyses in current use by the medical community today will be replaced in the future by analyses that reveal a far more comprehensive metabolic signature. This signature is expected to describe global biochemical aberrations that reflect patterns of variance in states of wellness, more accurately describe specific diseases and their progression, and greatly aid in differential diagnosis. Such future metabolic signatures will: (1) provide predictive, prognostic, diagnostic, and surrogate markers of diverse disease states; (2) inform on underlying molecular mechanisms of diseases; (3) allow for sub-classification of diseases, and stratification of patients based on metabolic pathways impacted; (4) reveal biomarkers for drug response phenotypes, providing an effective means to predict variation in a subject’s response to treatment (pharmacometabolomics); (5) define a metabotype for each specific genotype, offering a functional read-out for genetic variants: (6) provide a means to monitor response and recurrence of diseases, such as cancers: (7) describe the molecular landscape in human performance applications and extreme environments. Importantly, sophisticated metabolomic analytical platforms and informatics tools have recently been developed that make it possible to measure thousands of metabolites in blood, other body fluids, and tissues. Such tools also enable more robust analysis of response to treatment. New insights have been gained about mechanisms of diseases, including neuropsychiatric disorders, cardiovascular disease, cancers, diabetes and a range of pathologies. A series of ground breaking studies supported by National Institute of Health (NIH) through the Pharmacometabolomics Research Network and its partnership with the Pharmacogenomics Research Network illustrate how a patient’s metabotype at baseline, prior to treatment, during treatment, and post-treatment, can inform about treatment outcomes and variations in responsiveness to drugs (e.g., statins, antidepressants, antihypertensives and antiplatelet therapies). These studies along with several others also exemplify how metabolomics data can complement and inform genetic data in defining ethnic, sex, and gender basis for variation in responses to treatment, which illustrates how pharmacometabolomics and pharmacogenomics are complementary and powerful tools for precision medicine. Conclusions: Key scientific concepts and recommendations for precision medicine: Our metabolomics community believes that inclusion of metabolomics data in precision medicine initiatives is timely and will provide an extremely valuable layer of data that compliments and informs other data obtained by these important initiatives. Our Metabolomics Society, through its “Precision Medicine and Pharmacometabolomics Task Group”, with input from our metabolomics community at large, has developed this White Paper where we discuss the value and approaches for including metabolomics data in large precision medicine initiatives. This White Paper offers recommendations for the selection of state of-the-art metabolomics platforms and approaches that offer the widest biochemical coverage, considers critical sample collection and preservation, as well as standardization of measurements, among other important topics. We anticipate that our metabolomics community will have representation in large precision medicine initiatives to provide input with regard to sample acquisition/preservation, selection of optimal omics technologies, and key issues regarding data collection, interpretation, and dissemination. We strongly recommend the collection and biobanking of samples for precision medicine initiatives that will take into consideration needs for large-scale metabolic phenotyping studie
The PN.S Elliptical Galaxy Survey: the dark matter in NGC 4494
We present new Planetary Nebula Spectrograph observations of the ordinary
elliptical galaxy NGC 4494, resulting in positions and velocities of 255 PNe
out to 7 effective radii (25 kpc). We also present new wide-field surface
photometry from MMT/Megacam, and long-slit stellar kinematics from VLT/FORS2.
The spatial and kinematical distributions of the PNe agree with the field stars
in the region of overlap. The mean rotation is relatively low, with a possible
kinematic axis twist outside 1 Re. The velocity dispersion profile declines
with radius, though not very steeply, down to ~70 km/s at the last data point.
We have constructed spherical dynamical models of the system, including Jeans
analyses with multi-component LCDM-motivated galaxies as well as logarithmic
potentials. These models include special attention to orbital anisotropy, which
we constrain using fourth-order velocity moments. Given several different sets
of modelling methods and assumptions, we find consistent results for the mass
profile within the radial range constrained by the data. Some dark matter (DM)
is required by the data; our best-fit solution has a radially anisotropic
stellar halo, a plausible stellar mass-to-light ratio, and a DM halo with an
unexpectedly low central density. We find that this result does not
substantially change with a flattened axisymmetric model.
Taken together with other results for galaxy halo masses, we find suggestions
for a puzzling pattern wherein most intermediate-luminosity galaxies have very
low concentration halos, while some high-mass ellipticals have very high
concentrations. We discuss some possible implications of these results for DM
and galaxy formation.Comment: 29 pages, 17 figures. MNRAS, accepte
Flashlights: More than A Dozen High-Significance Microlensing Events of Extremely Magnified Stars in Galaxies at Redshifts z=0.7-1.5
Once only accessible in nearby galaxies, we can now study individual stars
across much of the observable universe aided by galaxy-cluster gravitational
lenses. When a star, compact object, or multiple such objects in the foreground
galaxy-cluster lens become aligned, they can magnify a background individual
star, and the timescale of a magnification peak can limit its size to tens of
AU. The number and frequency of microlensing events therefore opens a window
into the population of stars and compact objects, as well as high-redshift
stars. To assemble the first statistical sample of stars in order to constrain
the initial mass function (IMF) of massive stars at redshift z=0.7-1.5, the
abundance of primordial black holes in galaxy-cluster dark matter, and the IMF
of the stars making up the intracluster light, we are carrying out a 192-orbit
program with the Hubble Space Telescope called "Flashlights," which is now
two-thirds complete owing to scheduling challenges. We use the ultrawide F200LP
and F350LP long-pass WFC3 UVIS filters and conduct two 16-orbit visits
separated by one year. Having an identical roll angle during both visits, while
difficult to schedule, yields extremely clean subtraction. Here we report the
discovery of more than a dozen bright microlensing events, including multiple
examples in the famous "Dragon Arc" discovered in the 1980s, as well as the
"Spocks" and "Warhol" arcs that have hosted already known supergiants. The
ultradeep observer-frame ultraviolet-through-optical imaging is sensitive to
hot stars, which will complement deep James Webb Space Telescope infrared
imaging. We are also acquiring Large Binocular Telescope LUCI and Keck-I
MOSFIRE near-infrared spectra of the highly magnified arcs to constrain their
recent star-formation histories
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