1,637 research outputs found
The extraordinary mid-infrared spectral properties of FeLoBAL Quasars
We present mid-infrared spectra of six FeLoBAL QSOs at 1<z<1.8, taken with
the Spitzer space telescope. The spectra span a range of shapes, from hot dust
dominated AGN with silicate emission at 9.7 microns, to moderately obscured
starbursts with strong Polycyclic Aromatic Hydrocarbon (PAH) emission. The
spectrum of one object, SDSS 1214-0001, shows the most prominent PAHs yet seen
in any QSO at any redshift, implying that the starburst dominates the mid-IR
emission with an associated star formation rate of order 2700 solar masses per
year. With the caveats that our sample is small and not robustly selected, we
combine our mid-IR spectral diagnostics with previous observations to propose
that FeLoBAL QSOs are at least largely comprised of systems in which (a) a
merger driven starburst is ending, (b) a luminous AGN is in the last stages of
burning through its surrounding dust, and (c) which we may be viewing over a
restricted line of sight range.Comment: ApJ, accepte
The Impact of Competitive Foods on Children’s Fruit and Vegetable Consumption: An Observational Plate Waste Study
Little is known about the effect of competitive foods on children’s consumption of lunch meals in elementary schools in Mississippi. The objective of this observational study was to examine how competitive food purchases affect entrée, fruit, and vegetable consumption using the quarter-waste method. A total of 862 meals and purchase of competitive foods were observed. Children who purchased ice cream or pudding were 1.6 times more likely to throw away more than 50% of their entrée, 3.5 times more likely to not eat their vegetables, and more than two times more likely to not eat their fruit than children who did not purchase ice cream or pudding. Children who purchased chips were also less likely to consume more than 50% of their entrée. These findings suggest that competitive foods can impact children’s fruit and vegetable consumption
The optically-powerful quasar E1821+643 is associated with a 300-kpc scale FRI radio structure
We present a deep image of the optically-powerful quasar E1821+643 at 18cm
made with the Very Large Array (VLA). This image reveals radio emission, over
280 kpc in extent, elongated way beyond the quasar's host galaxy. Its radio
structure has decreasing surface brightness with increasing distance from the
bright core, characteristic of FRI sources (Fanaroff & Riley 1974). Its radio
luminosity at 5GHz falls in the classification for `radio-quiet' quasars (it is
only 10^23.9 W/Hz/sr; see e.g. Kellermann et al 1994). Its radio luminosity at
151MHz (which is 10^25.3 W/Hz/sr) is at the transition luminosity observed to
separate FRIs and FRIIs. Hitherto, no optically-powerful quasar had been found
to have a conventional FRI radio structure. For searches at low-frequency this
is unsurprising given current sensitivity and plausible radio spectral indices
for radio-quiet quasars. We demonstrate the inevitability of the extent of any
FRqI radio structures being seriously under-estimated by existing targetted
follow-up observations of other optically-selected quasars, which are typically
short exposures of z > 0.3 objects, and discuss the implications for the
purported radio bimodality in quasars.
The nature of the inner arcsec-scale jet in E1821+643, together with its
large-scale radio structure, suggest that the jet-axis in this quasar is
precessing (cf. Galactic jet sources such as SS433). A possible explanation for
this is that its central engine is a binary whose black holes have yet to
coalesce. The ubiquity of precession in `radio-quiet' quasars, perhaps as a
means of reducing the observable radio luminosity expected in highly-accreting
systems, remains to be established.Comment: Accepted by ApJ Letters; higher quality versions of figures available
at http://www-astro.physics.ox.ac.uk/~km
Intravenous Prenatal Nicotine Exposure Alters METH-Induced Hyperactivity, Conditioned Hyperactivity, and BDNF in Adult Rat Offspring
In the USA, approximately 15% of women smoke tobacco cigarettes during pregnancy. In utero tobacco smoke exposure produces somatic growth deficits like intrauterine growth restriction and low birth w
The line-of-sight distribution of the gas in the inner 60 pc of the Galaxy
2MASS K_S band data of the inner 60 pc of the Galaxy are used to reconstruct
the line-of-sight distances of the giant molecular clouds located in this
region. Using the 2MASS H band image of the same region, two different
populations of point sources are identified according to their flux ratio in
the two bands. The population of blue point sources forms a homogeneous
foreground that has to be subtracted before analyzing the K_S band image. The
reconstruction is made using two basic assumptions: (i) an axis-symmetric
stellar distribution in the region of interest and
(ii) optically thick clouds with an area filling factor of ~1 that block all
light of stars located behind them. Due to the reconstruction method, the
relative distance between the different cloud complexes is a robust result,
whereas it is not excluded that the absolute distance with respect to Sgr A* of
structures located more than 10 pc in front of Sgr A* are understimated by up
to a factor of 2. It is shown that all structures observed in the 1.2 mm
continuum and in the CS(2-1) line are present in absorption. We place the 50 km
s^-1 cloud complex close to, but in front of, Sgr A*. The 20 km s^-1 cloud
complex is located in front of the 50 km s^-1 cloud complex and has a large LOS
distance gradient along the direction of the galactic longitude. The bulk of
the Circumnuclear Disk is not seen in absorption. This leads to an upper limit
of the cloud sizes within the Circumnuclear Disk of ~0.06 pc.Comment: 12 pages with 17 figures. Accepted for publication in A&
The Clusters AgeS Experiment (CASE). IV. Analysis of the Eclipsing Binary V69 in the Globular Cluster 47 Tuc
We use photometric and spectroscopic observations of the eclipsing binary
V69-47 Tuc to derive the masses, radii, and luminosities of the component
stars. Based on measured systemic velocity, distance, and proper motion, the
system is a member of the globular cluster 47 Tuc. The system has an orbital
period of 29.5 d and the orbit is slightly eccentric with e=0.056. We obtain
Mp=0.8762 +- 0.0048 M(Sun), Rp=1.3148 +-0.0051 R(Sun), Lp=1.94 +- 0.21 L(Sun)
for the primary and Ms=0.8588 +- 0.0060 M(Sun), Rs=1.1616 +- 0.0062 R(Sun),
Ls=1.53 +- 0.17 L(Sun) for the secondary. These components of V69 are the first
Population II stars with masses and radii derived directly and with an accuracy
of better than 1%. We measure an apparent distance modulus of (m-M)v=13.35 +-
0.08 to V69. We compare the absolute parameters of V69 with five sets of
stellar evolution models and estimate the age of V69 using mass-luminosity-age,
mass-radius-age, and turnoff mass - age relations. The masses, radii, and
luminosities of the component stars are determined well enough that the
measurement of ages is dominated by systematic differences between the
evolutionary models, in particular, the adopted helium abundance. By comparing
the observations to Dartmouth model isochrones we estimate the age of V69 to be
11.25 +- 0.21(random) +- 0.85(systematic) Gyr assuming [Fe/H]=-0.70,
[alpha/Fe]=0.4, and Y=0.255. The determination of the distance to V69, and
hence to 47Tuc, can be further improved when infrared eclipse photometry is
obtained for the variable.Comment: 49 pages, 15 figures, submitted to A
Barriers to enrollment in a randomized controlled trial of hydrocortisone for cardiovascular insufficiency in term and late preterm newborn infants.
ObjectiveTo analyze reasons for low enrollment in a randomized controlled trial (RCT) of the effect of hydrocortisone for cardiovascular insufficiency on survival without neurodevelopmental impairment (NDI) in term/late preterm newborns.Study designThe original study was a multicenter RCT. Eligibility: ⩾34 weeks' gestation, <72 h old, mechanically ventilated, receiving inotrope. Primary outcome was NDI at 2 years; infants with diagnoses at high risk for NDI were excluded. This paper presents an analysis of reasons for low patient enrollment.ResultsTwo hundred and fifty-seven of the 932 otherwise eligible infants received inotropes; however, 207 (81%) had exclusionary diagnoses. Only 12 infants were randomized over 10 months; therefore, the study was terminated. Contributing factors included few eligible infants after exclusions, open-label steroid therapy and a narrow enrollment window.ConclusionDespite an observational study to estimate the population, very few infants were enrolled. Successful RCTs of emergent therapy may require fewer exclusions, a short-term primary outcome, waiver of consent and/or other alternatives
The dynamics of the Circumnuclear Disk and its environment in the Galactic centre
We address the question of the dynamics in the inner 50 pc of the Galactic
Centre. In a first step we investigate the cloud-cloud collision rate in the
Circumnuclear Disk (CND) with the help of a three dimensional N-body code using
gas particles that can have inelastic collisions. The CND might be a longer
lived structure than previously assumed. The whole disk-like structure of the
CND can thus survive for several million years. A realistic simulation of the
CND shows the observed disk height structure. In a second step the environment
of the CND is taken into account. Retrograde and prograde encounters of a cloud
of several 10^4 M_solar falling onto an already existing nuclear disk using
different energy loss rates per collision are simulated. The influence of the
energy loss rate per collision on the evolution of the mass accretion and cloud
collision rates is strongest for a prograde encounter. A composite data cube of
two different snapshots of a prograde encounter together with the CND shows
striking similarity with the observed Sgr A cloud complex. The current
appearance of the Galactic Centre environment can thus be explained by at least
two dynamically distinct features together with the CND. The current mass
accretion rate within the CND ranges between 10^-3 and 10^-4 M_solar yr^-1. It
can rise up to several 10^-2 M_solar yr^-1 during massive accretion events.Comment: 14 pages with 22 figures. Accepted for publication in A&
RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514
A strong emission line at 6703A has been detected in the optical spectrum for
the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This
radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850
MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky
strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of
the identification of this line with Ly\alpha at redshift z=4.514. In this
case, the object belongs to the group of extremely distant radio galaxies of
ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be
provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a
time less than the age of the Universe at the observed z(1.3 Gyr) or had a
primordial origin.Comment: 8 pages, 3 figure
In-flight performance and calibration of the Infrared Array Camera (IRAC) for the Spitzer Space Telescope
The Infrared Array Camera (IRAC) is one of three focal plane instruments on board the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 μm in two nearly adjacent fields of view. We summarize here the in-flight scientific, technical, and operational performance of IRAC
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