241 research outputs found
L-band ATS 5/Orion/S. S. Manhattan marine navigation and communication experiment Final report
L-band signals relayed by synchronous satellite for navigation and data communicatio
Search for grain growth towards the center of L1544
In dense and cold molecular clouds dust grains are surrounded by thick icy
mantles. It is however not clear if dust growth and coagulation take place
before the switch-on of a protostar. This is an important issue, as the
presence of large grains may affect the chemical structure of dense cloud
cores, including the dynamically important ionization fraction, and the future
evolution of solids in protoplanetary disks. To study this further, we focus on
L1544, one of the most centrally concentrated pre-stellar cores on the verge of
star formation, and with a well-known physical structure. We observed L1544 at
1.2 and 2 mm using NIKA, a new receiver at the IRAM 30 m telescope, and we used
data from the Herschel Space Observatory archive. We find no evidence of grain
growth towards the center of L1544 at the available angular resolution.
Therefore, we conclude that single dish observations do not allow us to
investigate grain growth toward the pre-stellar core L1544 and high sensitivity
interferometer observations are needed. We predict that dust grains can grow to
200 m in size toward the central ~300 au of L1544. This will imply a dust
opacity change by a factor of ~2.5 at 1.2 mm, which can be detected using the
Atacama Large Millimeter and submillimeter Array (ALMA) at different
wavelengths and with an angular resolution of 2".Comment: 12 pages, 14 figures. Accepted for publication in A&
Search for Interstellar Water in the Translucent Molecular Cloud toward HD 154368
We report an upper limit of 9 x 10^{12} cm-2 on the column density of water
in the translucent cloud along the line of sight toward HD 154368. This result
is based upon a search for the C-X band of water near 1240 \AA carried out
using the Goddard High Resolution Spectrograph of the Hubble Space Telescope.
Our observational limit on the water abundance together with detailed chemical
models of translucent clouds and previous measurements of OH along the line of
sight constrain the branching ratio in the dissociative recombination of H_3O+
to form water. We find at the level that no more than 30% of
dissociative recombinations of H_3O+ can lead to H_2O. The observed spectrum
also yielded high-resolution observations of the Mg II doublet at 1239.9 \AA
and 1240.4 \AA, allowing the velocity structure of the dominant ionization
state of magnesium to be studied along the line of sight. The Mg II spectrum is
consistent with GHRS observations at lower spectral resolution that were
obtained previously but allow an additional velocity component to be
identified.Comment: Accepted by ApJ, uses aasp
Models for Dusty Lyman alpha Emitters at High Redshift
Models are presented for the Lyman alpha emission of dusty high-redshift
galaxies by combining the Press-Schechter formalism with a treatment of the
inhomogeneous dust distribution inside galaxies. It is found that the amount of
Lyman alpha radiation escaping from the galaxies strongly depends on the time
over which the dust is produced through stellar activity, and on the ambient
inhomogeneity of the HII regions that surround the ionizing OB stars. Good
agreement is found with recent observations, as well as previous
non-detections. Our models indicate that the dust content builds up in no more
than approximately 5x10^8 yr, the galactic HII regions are inhomogeneous with a
cloud covering factor of order unity, and the overall star formation efficiency
is at least about 5%. It is predicted that future observations can detect these
Lyman alpha galaxies upto redshifts of about 8.Comment: 16 pages, 4 figures, submitted to Ap
Far-Infrared and Sub-Millimeter Observations and Physical Models of the Reflection Nebula Ced 201
ISO [C II] 158 micron, [O I] 63 micron, and H_2 9 and 17 micron observations are presented of the reflection nebula Ced 201, which is a photon-dominated region illuminated by a B9.5 star with a color temperature of 10,000 K (a cool PDR). In combination with ground based [C I] 609 micron, CO, 13CO, CS and HCO+ data, the carbon budget and physical structure of the reflection nebula are constrained. The obtained data set is the first one to contain all important cooling lines of a cool PDR, and allows a comparison to be made with classical PDRs. To this effect one- and three-dimensional PDR models are presented which incorporate the physical characteristics of the source, and are aimed at understanding the dominant heating processes of the cloud. The contribution of very small grains to the photo-electric heating rate is estimated from these models and used to constrain the total abundance of PAHs and small grains. Observations of the pure rotational H_2 lines with ISO, in particular the S(3) line, indicate the presence of a small amount of very warm, approximately 330 K, molecular gas. This gas cannot be accommodated by the presented models
Molecular line emission in NGC1068 imaged with ALMA: II. The chemistry of the dense molecular gas
We present a detailed analysis of ALMA Bands 7 and 9 data of CO, HCO+, HCN
and CS, augmented with Plateau de Bure Interferometer (PdBI) data of the ~ 200
pc circumnuclear disk (CND) and the ~ 1.3 kpc starburst ring (SB ring) of
NGC~1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy. We aim at determining
the physical characteristics of the dense gas present in the CND and whether
the different line intensity ratios we find within the CND as well as between
the CND and the SB ring are due to excitation effects (gas density and
temperature differences) or to a different chemistry. We estimate the column
densities of each species in Local Thermodynamic Equilibrium (LTE). We then
compute large one-dimensional non-LTE radiative transfer grids (using RADEX) by
using first only the CO transitions, and then all the available molecules in
order to constrain the densities, temperatures and column densities within the
CND. We finally present a preliminary set of chemical models to determine the
origin of the gas. We find that in general the gas in the CND is very dense (>
10^5 cm^-3) and hot (T> 150K), with differences especially in the temperature
across the CND. The AGN position has the lowest CO/HCO+, CO/HCN and CO/CS
column density ratios. RADEX analyses seem to indicate that there is chemical
differentiation across the CND. We also find differences between the chemistry
of the SB ring and some regions of the CND; the SB ring is also much colder and
less dense than the CND. Chemical modelling does not succeed in reproducing all
the molecular ratios with one model per region, suggesting the presence of
multi-gas phase components. The LTE, RADEX and chemical analyses all indicate
that more than one gas-phase component is necessary to uniquely fit all the
available molecular ratios within the CND.Comment: Accepted by A&A; please contact the author for a better version of
the pdf where the resolution and positions of figures are as they will appear
in the Journa
Healthcare reimbursement costs of children with type 1 diabetes in the Netherlands, a observational nationwide study (Young Dudes-4)
Background: Type 1 diabetes mellitus (T1DM) is one of the most common chronic diseases in children. Studies on costs related to T1DM are scarce and focused primarily on the costs directly related to diabetes. We aimed to investigate both the overall healthcare costs and the more specific costs related to the management of diabetes.Methods: This is a retrospective and observational, nationwide cohort study of all Dutch children (aged 0-18 years) with T1DM. Data were collected from the national registry for healthcare reimbursement, in which all Dutch insurance companies combine their reimbursement data. In the Netherlands for all Dutch citizens health care is covered by law and all children are treated by hospital-based paediatricians.Results: We analysed 6710 children distributed over 81 hospitals: 475 children in 6 university hospitals and 6235 children in 75 general hospitals. Total reimbursement for all children with T1DM over the period 2009 to 2011 was (sic) 167,494,732 corresponding to an annual mean of (sic) 55,831,577 of total costs and (sic) 8326 euros per child. When comparing small (between 26 and 54 patients), medium (57-84 patients) and large (88-248 patients) general hospitals, costs per patient were highest in the hospitals with the highest number of T1DM patients. The costs for devices, secondary care and pharmaceutics had most impact on total expenditures. Over the study period, there was a slight decrease in per person costs.Conclusion: The overall health expenditure of a child with T1DM is more than (sic) 8000 per patient per annum. Given the move towards more device-intensive multidisciplinary care for these patients, the costs of treating T1DM in children are likely to increase further in the coming years.</p
The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
(Ultra) Luminous Infrared Galaxies ((U)LIRGs) are objects characterized by
their extreme infrared (8-1000 m) luminosities (L and L). The Herschel Comprehensive ULIRG
Emission Survey (HerCULES; PI van der Werf) presents a representative
flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of
these objects (10). With the \emph{Herschel
Space Observatory}, we observe [CII] 157 m, [OI] 63 m, and [OI] 145
m line emission with PACS, CO J=4-3 through J=13-12, [CI] 370 m, and
[CI] 609 m with SPIRE, and low-J CO transitions with ground-based
telescopes. The CO ladders of the sample are separated into three classes based
on their excitation level. In 13 of the galaxies, the [OI] 63 m emission
line is self absorbed. Comparing the CO excitation to the IRAS 60/100 m
ratio and to far infrared luminosity, we find that the CO excitation is more
correlated to the far infrared colors. We present cooling budgets for the
galaxies and find fine-structure line flux deficits in the [CII], [SiII], [OI],
and [CI] lines in the objects with the highest far IR fluxes, but do not
observe this for CO . In order to study the heating of the
molecular gas, we present a combination of three diagnostic quantities to help
determine the dominant heating source. Using the CO excitation, the CO J=1-0
linewidth, and the AGN contribution, we conclude that galaxies with large CO
linewidths always have high-excitation CO ladders, and often low AGN
contributions, suggesting that mechanical heating is important
Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231
We present a full high resolution SPIRE FTS spectrum of the nearby
ultraluminous infrared galaxy Mrk231. In total 25 lines are detected, including
CO J=5-4 through J=13-12, 7 rotational lines of H2O, 3 of OH+ and one line each
of H2O+, CH+, and HF. We find that the excitation of the CO rotational levels
up to J=8 can be accounted for by UV radiation from star formation. However,
the approximately flat luminosity distribution of the CO lines over the
rotational ladder above J=8 requires the presence of a separate source of
excitation for the highest CO lines. We explore X-ray heating by the accreting
supermassive black hole in Mrk231 as a source of excitation for these lines,
and find that it can reproduce the observed luminosities. We also consider a
model with dense gas in a strong UV radiation field to produce the highest CO
lines, but find that this model strongly overpredicts the hot dust mass in
Mrk231. Our favoured model consists of a star forming disk of radius 560 pc,
containing clumps of dense gas exposed to strong UV radiation, dominating the
emission of CO lines up to J=8. X-rays from the accreting supermassive black
hole in Mrk231 dominate the excitation and chemistry of the inner disk out to a
radius of 160 pc, consistent with the X-ray power of the AGN in Mrk231. The
extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of
X-ray driven excitation and chemistry in this region.Comment: 5 pages, 2 figures, accepted for publication in Astronomy &
Astrophysics Special Issue on Herschel first result
Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN
We present high resolution (0."4) IRAM PdBI and ALMA mm and submm
observations of the (ultra) luminous infrared galaxies ((U)LIRGs)
IRAS17208-0014, Arp220, IC860 and Zw049.057 that reveal intense line emission
from vibrationally excited (=1) J=3-2 and 4-3 HCN. The emission is
emerging from buried, compact (r<17-70 pc) nuclei that have very high implied
mid-infrared surface brightness L kpc.
These nuclei are likely powered by accreting supermassive black holes (SMBHs)
and/or hot (>200 K) extreme starbursts. Vibrational, =1, lines of HCN
are excited by intense 14 micron mid-infrared emission and are excellent probes
of the dynamics, masses, and physical conditions of (U)LIRG nuclei when H
column densities exceed cm. It is clear that these lines open
up a new interesting avenue to gain access to the most obscured AGNs and
starbursts. Vibrationally excited HCN acts as a proxy for the absorbed
mid-infrared emission from the embedded nuclei, which allows for reconstruction
of the intrinsic, hotter dust SED. In contrast, we show strong evidence that
the ground vibrational state (=0), J=3-2 and 4-3 rotational lines of HCN
and HCO fail to probe the highly enshrouded, compact nuclear regions owing
to strong self- and continuum absorption. The HCN and HCO line profiles are
double-peaked because of the absorption and show evidence of non-circular
motions - possibly in the form of in- or outflows. Detections of vibrationally
excited HCN in external galaxies are so far limited to ULIRGs and early-type
spiral LIRGs, and we discuss possible causes for this. We tentatively suggest
that the peak of vibrationally excited HCN emission is connected to a rapid
stage of nuclear growth, before the phase of strong feedback.Comment: 13 pages, 7 figures, accepted for publication in Astronomy and
Astrophysic
- …