158 research outputs found
Molecular gas observations of the reddened quasar 3C 318
3C 318 is a z=1.574 radio-loud quasar. The small physical size of its radio
jets indicate that these jets were triggered relatively recently. In addition
to the ultraviolet continuum emission being reddened by dust, detections with
IRAS and SCUBA show it to have an exceptionally high far-infrared luminosity.
We present CO(2-1) observations of 3C 318 made with the IRAM Plateau de Bure
Interferometer. We detect CO(2-1) emission with a FWHM=200 km/s at a
signal-to-noise ratio of 5.4. There is evidence for positional (~ 20 kpc) and
velocity (~ -400 km/s) offsets between the molecular gas and the quasar which
may be due to the quasar experiencing a major merger. The mass of molecular gas
inferred from our observations is M_{H_2}=(3.0 +/- 0.6) x 10^{10} M_sun. This
molecular gas mass is comparable to that in sub-mm-selected galaxies at similar
redshifts. The large molecular gas mass is consistent with the primary source
of heating for the cool dust in this quasar to be massive star formation with a
star formation rate of 1700 M_sun/yr and a gas depletion timescale of 20 Myr.
Our observations support the idea that star formation episodes and jet
triggering can be synchronised.Comment: 4 pages, 3 b/w figures, AJ, in pres
Resolved nuclear CO(1-0) emission in APM08279+5255: Gravitational lensing by a naked cusp?
The ultraluminous broad absorption line quasar APM08279+5255 is one of the
most luminous systems known. Here, we present an analysis of its nuclear
CO(1-0) emission. Its extended distribution suggests that the gravitational
lens in this system is highly elliptical, probably a highly inclined disk. The
quasar core, however, lies in the vicinity of naked cusp, indicating that
APM08279+5255 is truly the only odd-image gravitational lens. This source is
the second system for which the gravitational lens can be used to study
structure on sub-kpc scales in the molecular gas associated with the AGN host
galaxy. The observations and lens model require CO distributed on a scale of
pc. Using this scale, we find that the molecular gas mass makes a
significant, and perhaps dominant, contribution to the total mass within a
couple hundred parsecs of the nucleus of APM08279+5255.Comment: 5 Pages, 2 Figures, to appear in MNRAS Letters - Resolution of Figure
2 reduce
A massive reservoir of low-excitation molecular gas at high redshift
Molecular hydrogen is an important component of galaxies because it fuels
star formation and accretion onto AGN, the two processes that generate the
large infrared luminosities of gas-rich galaxies. Observations of spectral-line
emission from the tracer molecule CO are used to probe the properties of this
gas. But the lines that have been studied in the local Universe, mostly the
lower rotational transitions of J = 1-0 and J = 2-1, have hitherto been
unobservable in high-redshift galaxies. Instead, higher transitions have been
used, although the densities and temperatures required to excite these higher
transitions may not be reached by much of the gas. As a result, past
observations may have underestimated the total amount of molecular gas by a
substantial amount. Here we report the discovery of large amounts of
low-excitation molecular gas around the infrared-luminous quasar, APM
08279+5255 at z = 3.91, using the two lowest excitation lines of 12CO (J = 1-0
and J = 2-1). The maps confirm the presence of hot and dense gas near the
nucleus, and reveal an extended reservoir of molecular gas with low excitation
that is 10 to 100 times more massive than the gas traced by higher-excitation
observations. This raises the possibility that significant amounts of
low-excitation molecular gas may lurk in the environments of high-redshift (z >
3) galaxies.Comment: To appear as a Letter to Nature, 4th January 200
The First Two Years of Electromagnetic Follow-Up with Advanced LIGO and Virgo
We anticipate the first direct detections of gravitational waves (GWs) with
Advanced LIGO and Virgo later this decade. Though this groundbreaking technical
achievement will be its own reward, a still greater prize could be observations
of compact binary mergers in both gravitational and electromagnetic channels
simultaneously. During Advanced LIGO and Virgo's first two years of operation,
2015 through 2016, we expect the global GW detector array to improve in
sensitivity and livetime and expand from two to three detectors. We model the
detection rate and the sky localization accuracy for binary neutron star (BNS)
mergers across this transition. We have analyzed a large, astrophysically
motivated source population using real-time detection and sky localization
codes and higher-latency parameter estimation codes that have been expressly
built for operation in the Advanced LIGO/Virgo era. We show that for most BNS
events the rapid sky localization, available about a minute after a detection,
is as accurate as the full parameter estimation. We demonstrate that Advanced
Virgo will play an important role in sky localization, even though it is
anticipated to come online with only one-third as much sensitivity as the
Advanced LIGO detectors. We find that the median 90% confidence region shrinks
from ~500 square degrees in 2015 to ~200 square degrees in 2016. A few distinct
scenarios for the first LIGO/Virgo detections emerge from our simulations.Comment: 17 pages, 11 figures, 5 tables. For accompanying data, see
http://www.ligo.org/scientists/first2year
Serum vascular endothelial growth factor levels in the IVAN trial; relationships with drug, dosing and systemic serious adverse events:Serum VEGF associations with drug, dosing and systemic SAEs
Purpose: To describe serum vascular endothelial growth factor (sVEGF) in patients with neovascular age-related macular degeneration (nAMD) receiving anti-VEGF agents and associations between sVEGF and systemic serious adverse events (SSAEs). Design: Exploratory analyses of a randomized controlled trial that enrolled 610 participants with nAMD and compared 2 anti-VEGF antibodies, ranibizumab and bevacizumab, and 2 treatment regimens, monthly vs. discontinuous, with 2 yearsâ follow-up. Participants: Adults aged 50+ years with treatment-naĂŻve nAMD and a visual acuity of â„25 letters (Snellen equivalent 20/320) in the affected eye. Methods: Intravitreal injection of anti-VEGF antibodies. Main Outcome Measures: sVEGF and occurrence of SSAE, with particular interest in arteriothromboembolic events (ATE) and immunologically mediated events (IME). Results: On average, sVEGF (measured at months 0, 1, 11, 12, 23, and 24) decreased from a geometric mean of 168 pg/mL at baseline to 64 pg/mL at month 24. The decrease was greater with bevacizumab than with ranibizumab and was dependent on time since last treatment; at month 24 sVEGF was 11% lower with bevacizumab if treated â„3 months previously, 51% lower if treated 2 months previously, and 76% lower if treated the previous month, compared with ranibizumab. The hazard of experiencing an ATE increased with age (hazard ratio [HR] = 2.01; 95% confidence interval [CI] = 1.32â3.05; P = 0.001) and higher sVEGF (HR = 1.16; 95% CI = 1.03â1.30, per 100 unit rise in sVEGF; P = 0.013). There was no association between sVEGF and the hazard of an IME (HR = 1.01; 95% CI = 0.76â1.33; P = 0.942); however, the hazard of an IME was significantly increased by treatment with bevacizumab compared with ranibizumab (HR = 3.53; 95% CI = 1.35â9.22; P = 0.010). The hazard of an âother SSAEâ (not categorized as ATE or IME) increased with age (HR 1.51, 95% CI 1.14â2.01, P = 0.005) and decreased if an injection had been administered within the previous month (HR = 0.68; 95% CI = 0.45â1.03; P = 0.069). Conclusions: The decrease in sVEGF is greater with bevacizumab than with ranibizumab, but this difference is eliminated when treatment is withheld for 3 months. Higher sVEGF increased the hazard of an ATE and bevacizumab increases the hazard of an IME compared with ranibizumab.</p
Molecular Gas in the Host Galaxy of a Quasar at Redshift z=6.42
Observations of the molecular gas phase in quasar host galaxies provide
fundamental constraints on galaxy evolution at the highest redshifts. Molecular
gas is the material out of which stars form; it can be traced by spectral line
emission of carbon--monoxide (CO). To date, CO emission has been detected in
more than a dozen quasar host galaxies with redshifts (z) larger 2, the record
holder being at z=4.69. At these distances the CO lines are shifted to longer
wavelengths, enabling their observation with sensitive radio and millimetre
interferometers. Here we present the discovery of CO emission toward the quasar
SDSS J114816.64+525150.3 (hereafter J1148+5251) at a redshift of z=6.42, when
the universe was only 1/16 of its present age. This is the first detection of
molecular gas at the end of cosmic reionization. The presence of large amounts
of molecular gas (M(H_2)=2.2e10 M_sun) in an object at this time demonstrates
that heavy element enriched molecular gas can be generated rapidly in the
earliest galaxies.Comment: 12 pages, 2 figures. To appear in Nature, July, 200
Millimetre observations of a sample of high-redshift obscured quasars
We present observations at 1.2 mm with MAMBO-II of a sample of z>~2
radio-intermediate obscured quasars, as well as CO observations of two sources
with the Plateau de Bure Interferometer. Five out of 21 sources (24%) are
detected at a significance of >=3sigma. Stacking all sources leads to a
statistical detection of = 0.96+-0.11 mJy and stacking only the
non-detections also yields a statistical detection, with = 0.51+-0.13
mJy. This corresponds to a typical far-infrared luminosity L_FIR~4x10^12 Lsol.
If the far-infrared luminosity is powered entirely by star-formation, and not
by AGN-heated dust, then the characteristic inferred star-formation rate is
~700 Msol yr-1. This far-infrared luminosity implies a dust mass of
M_dust~3x10^8 Msol. We estimate that such large dust masses on kpc scales can
plausibly cause the obscuration of the quasars. We present dust SEDs for our
sample and derive a mean SED for our sample. This mean SED is not well fitted
by clumpy torus models, unless additional extinction and far-infrared
re-emission due to cool dust are included. There is a hint that the host
galaxies of obscured quasars must have higher far-infrared luminosities and
cool-dust masses and are therefore often found at an earlier evolutionary phase
than those of unobscured quasars. For one source at z=2.767, we detect the
CO(3-2) transition, with S_CO Delta nu=630+-50 mJy km s-1, corresponding to
L_CO(3-2)= 3.2x10^7 Lsol, or L'_CO(3-2)=2.4x10^10 K km s-1 pc2. For another
source at z=4.17, the lack of detection of the CO(4-3) line yields a limit of
L'_CO(4-3)<1x10^10 K km s-1 pc2. Molecular gas masses, gas depletion timescales
and gas-to-dust ratios are estimated (Abridged).Comment: Accepted by ApJ, 25 pages, 11 figures, 4 table
Molecular Gas in Redshift 6 Quasar Host Galaxies
We report our new observations of redshifted carbon monoxide emission from
six z~6 quasars, using the PdBI. CO (6-5) or (5-4) line emission was detected
in all six sources. Together with two other previous CO detections, these
observations provide unique constraints on the molecular gas emission
properties in these quasar systems close to the end of the cosmic reionization.
Complementary results are also presented for low-J CO lines observed at the GBT
and the VLA, and dust continuum from five of these sources with the SHARC-II
bolometer camera at the CSO. We then present a study of the molecular gas
properties in our combined sample of eight CO-detected quasars at z~6. The
detections of high-order CO line emission in these objects indicates the
presence of highly excited molecular gas, with estimated masses on the order of
10^10 M_sun within the quasar host galaxies. No significant difference is found
in the gas mass and CO line width distributions between our z~6 quasars and
samples of CO-detected quasars and submillimeter galaxies.
Most of the CO-detected quasars at z~6 follow the far infrared-CO luminosity
relationship defined by actively star-forming galaxies at low and high
redshifts. This suggests that ongoing star formation in their hosts contributes
significantly to the dust heating at FIR wavelengths. The result is consistent
with the picture of galaxy formation co-eval with supermassive black hole
(SMBH) accretion in the earliest quasar-host systems. We investigate the black
hole--bulge relationships of our quasar sample, using the CO dynamics as a
tracer for the dynamical mass of the quasar host. The results place important
constraints on the formation and evolution of the most massive SMBH-spheroidal
host systems at the highest redshift.Comment: 34 pages, 8 figures, accepted for publication in Ap
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Multi-parameter phenotyping of platelet reactivity for stratification of human cohorts
Accurate and comprehensive assessment of platelet function across cohorts of donors may be key to understanding the risk of thrombotic events associated with cardiovascular disease, and hence help personalise the application of antiplatelet drugs. However, platelet function tests can be difficult to perform and analyse, unreliable or uninformative and poorly standardised across studies. The Platelet Phenomic Analysis (PPAnalysis) assay and associated open-source software platform was developed in response to these challenges. PPAnalysis utilises pre-prepared freeze-dried microtitre plates to provide a detailed characterisation of platelet function. The automated analysis of the high-dimensional data enables the identification of sub-populations of donors with distinct platelet function phenotypes. Using this approach we identified that the Sensitivity of a donorâs platelets to an agonist and their Capacity to generate a functional response are distinct independent metrics of platelet reactivity. Hierarchical clustering of these metrics identified six subgroups with distinct platelet phenotypes within healthy cohorts, indicating that platelet reactivity does not fit into the traditional simple categories of âhighâ and âlowâ responders. These platelet phenotypes were found to exist in two independent cohorts of healthy donors and were stable on recall. PPAnalysis is a powerful tool for stratification of cohorts on the basis of platelet reactivity which will enable investigation of the causes and consequences of differences in platelet function and drive progress towards precision medicine
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