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Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the cryogenic infrared space telescope recently pre-selected for a ‘Phase A’ concept study as one of the three remaining candidates for European Space Agency (ESA's) fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager [SPICA-POL, now called B-fields with BOlometers and Polarizers (B-BOP)], which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetised Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100–350
m images of linearly polarised dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200
m images will also have a factor
30 higher resolution than Planck polarisation data. This will make B-BOP a unique tool for characterising the statistical properties of the magnetised ISM and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing Galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.
This list reports measurements made at this laboratory since the preparation of the last list (Texas II). About twenty measurements are not reported because they are from series which are incomplete. Ages were calculated using a C14 half-life of 5568 yr and 1950 as the reference year. The modern standard used was 95% of NBS oxalic acid activity. The deviations reported are based on the counting statistics of the sample, background, and modern, and are ±1σ except that when the sample count approached either the modern standard or the background, 2σ limits are reported.
The Radiocarbon Dating Laboratory of the University of Texas was reorganized in late 1962. The dates reported in this list were obtained from February to November, 1963. The laboratory uses liquid scintillation counting with benzene solutions (Tamers, Stipp, and Collier, 1961; Noakes et al., 1963). The chemical synthesis has been modified and improved in several ways in order to permit one worker to produce a sample per day.
This list reports routine measurements made at this laboratory since the preparation of the last list (Texas III). It also includes measurements made on bone samples earlier as part of a study of the suitability of bone for C14 dating (Tamers and Pearson, 1965). In the absence of the laboratory director, M. A. Tamers, who has been on leave at the Caracas (IVIC) laboratory since October, 1963, laboratory operation and the selection and description of geologic samples have been handled by Pearson, and laboratory administration and archaeologic samples by Davis.
This list reports routine measurements made at this laboratory since the preparation of Texas IV. Samples numbered through Tx-309 were counted under the supervision of Pearson, who left the laboratory early in 1966. Valastro, Associate Director since August, 1966, is responsible for samples beginning with Tx-310. Laboratory administration and sample screening have been handled by Davis, M. A. Tamers, formerly Director, resigned in 1966.
The Herschel/HOBYS key program allows to statistically study the formation of 10−20 M⊙ stars. The IRAM/W43-HERO large program is itself dedicated to the much more extreme W43 molecular complex, which forms stars up to 50 M⊙. Both reveal high-density cloud filaments of several pc3, which are forming clusters of OB-type stars. Given their activity, these so-called mini-starburst cloud ridges could be seen as “miniature and instant models” of starburst galaxies. Both surveys also strongly suggest that high-mass prestellar cores do not exist, in agreement with the dynamical formation of cloud ridges. The HOBYS and W43 surveys are necessary steps towards Galaxy-wide studies of high-mass star formation.
The Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey aims to characterise the physical and chemical evolution of high-mass star-forming clumps. Exploiting the unique broad frequency range and on-the-fly mapping capabilities of the Australia Telescope National Facility Mopra 22 m single-dish telescope1, MALT90 has obtained 3′ × 3′ maps towards ~2 000 dense molecular clumps identified in the ATLASGAL 870 μm Galactic plane survey. The clumps were selected to host the early stages of high-mass star formation and to span the complete range in their evolutionary states (from prestellar, to protostellar, and on to
regions and photodissociation regions). Because MALT90 mapped 16 lines simultaneously with excellent spatial (38 arcsec) and spectral (0.11 km s−1) resolution, the data reveal a wealth of information about the clumps’ morphologies, chemistry, and kinematics. In this paper we outline the survey strategy, observing mode, data reduction procedure, and highlight some early science results. All MALT90 raw and processed data products are available to the community. With its unprecedented large sample of clumps, MALT90 is the largest survey of its type ever conducted and an excellent resource for identifying interesting candidates for high-resolution studies with ALMA.
The W43 region is one of the most massive star forming regions in our Galaxy. It is subject to a large IRAM 30m project that observes high spectral resolution maps of the complete complex in the 13CO (2–1) and C18O (2–1) lines. We find a variety of different sources of which we calculate excitation temperature, H2 column density and mass. We find the total mass of dense clouds in the complex to be 1.2×106 M⊙.
The Rosette molecular cloud has a characteristic morphology, where the central OB cluster NGC 2244 has blown a circular-shaped cavity into the cloud and the expanding HII-region now interacts with the cloud. We use continuum data obtained with the PACS (70 and 160 μm) and SPIRE instruments (250, 350, 500 μm) of the Herschel telescope to investigate the spatial distribution of cold and warm gas and to locate all star-forming sites in Rosette. We detected a clear negative temperature gradient and a positive density gradient (running from the HII-region/molecular cloud interface into the cloud), and an age-sequence (from more evolved to younger) with increasing distance to the cluster NGC 2244. The existence of such temperature and density gradients and the observed age-sequence imply that star formation in Rosette may indeed be influenced by the radiative impact of the central NGC 2244 cluster.
Submillimeter dust continuum emission traces high molecular column densities and, thus,
dense cloud regions in which new stars are forming. Surveys of the Galactic plane in such
emission have the potential of delivering an unbiased view of high-mass star formation
throughout the Milky Way. The location of the APEX telescope on the Chajnantor plateau in
Chile is ideally suited for mapping the inner Galaxy. ATLASGAL, The APEX Telescope Large
Area Survey of the Galaxy at 870 μm, is a survey of the Galactic plane
using the Large APEX Bolometer Camera (LABOCA), in the Galactic longitude and latitude
ranges of ±60 and ±1.5°, respectively. This survey is providing an unbiased sample of
cold dusty clumps in the Galaxy at submillimeter wavelength and a variety of molecular
line follow-up observations have been started to characterize the physical and chemical
conditions in the newly found clumps. Here, first results from this survey and its
follow-up programs are described.
Optical limiting in a solution of tetrabenzporphyrin (TBP) dissolved in tetrahydrofuran (THF) was measured in an f/5 optical focusing arrangement using 532 nm wavelength laser light with a 9 ns pulse duration. The performance of this solution was compared to a variety of other materials. In order to better understand the nonlinear behavior of this material, apertured and unapertured Z-scans were performed. From these measurements it was determined that the excited-state cross section and its ratio to ground-state cross section were large. The nonlinear refraction of this material is made up of contributions from thermal density change and population redistribution. Limiter performance was modeled in an f/64 limiter. The limiter behavior of a slightly modified compound and an additional solvent were measured.
A systematic, high angular-resolution study of IR-quiet Massive Dense Cores (MDCs) of Cygnus-X in continuum and high-density molecular tracers is presented. The results are compared with the quasi-static and the dynamical evolutionary scenario. We find that the fragmentation properties are not compatible with the quasi-static, monolithic collapse scenario, nor are they entirely compatible with the formation of a cluster of mostly low-mass stars. The kinematics of MDCs shows individual velocity components appearing as coherent flows, which indicate important dynamical processes at the scale of the mass reservoir around high-mass protostars.
Submillimeter continuum emission traces high molecular column densities and, thus, dense cloud regions in which new stars are forming. Surveys of the Galactic plane in such emission have the potential of delivering an unbiased view of high-mass star formation throughout the Milky Way. Here we present the scope, current status and first results of ATLASGAL, an ongoing survey of the Galactic plane using the Large APEX Bolometer Camera (LABOCA) on the Atacama Pathfinder Experiment (APEX) telescope at the Chajnantor plateau in Chile. Aimed at mapping 360 square degrees at 870 μm, with a uniform sensitivity of 50 mJy/beam, this survey will provide the first unbiased sample of cold dusty clumps in the Galaxy at submillimeter wavelengths. These will be targets for molecular line follow-up observations and high resolution studies with ALMA and the EVLA.
We review the theories and observations of high-mass star formation emphasizing the differences with those of low-mass star formation. We hereafter describe the progress expected to be achieved with Herschel, thanks notably to Key Programmes dedicated to the earliest phases of high-mass star formation.