169 research outputs found
Young stars and reflection nebulae near the lower "edge" of the Galactic molecular disc
We investigate the star formation occurring in a region well below the
Galactic plane towards the optical reflection nebula ESO 368-8 (IRAS
07383-3325). We confirm the presence of a small young stellar cluster (or
aggregate of tens of YSOs) identified earlier, embedded in a molecular cloud
located near the lower "edge" of the Galactic disc, and characterise the young
stellar population. We report the discovery of a near-infrared nebula, and
present a CO map revealing a new dense, dynamic cloud core. We used
near-infrared JHKs images, millimetre CO spectra and optical V-band images.
This star formation region displays an optical reflection nebula (ESO 368-8)
and a near-infrared nebula located about 46" (1.1 pc) from each other. The two
nebulae are likely to be coeval and to represent two manifestations of the same
single star formation episode with about 1 Myr age. The near-IR nebula reveals
an embedded, optically and near-IR invisible source whose light scatters off a
cavity carved by previous stellar jets or molecular outflows and into our
line-of-sight. The molecular cloud is fully covered by our CO(J=1-0) maps and,
traced by this line, extends over a region of 7.8 x 7.8 pc^2, exhibiting an
angular size 5.4' x 5.4' and shape (close to circular) similar to spherical (or
slightly cometary) globules. Towards the direction of the near-IR nebula, the
molecular cloud contains a dense core where the molecular gas exhibits large
line widths indicative of a very dynamical state, with stirred gas and
supersonic motions. Our estimates of the mass of the molecular gas in this
region range from 600 to 1600 solar masses. The extinction Av towards the
positions of the optical reflection nebula and of the near-IR nebula was found
to be Av=3-4 mag and Av=12-15 mag, respectively.Comment: 11 pages, 13 figure
A Uniform CO Survey of the Molecular Clouds in Orion and Monoceros
We report the results of a new large scale survey of the Orion-Monoceros
complex of molecular clouds made in the J = 1->0 line of CO with the
Harvard-Smithsonian 1.2m millimetre-wave telescope. The survey consists of
52,288 uniformly spaced spectra that cover an area of 432 square degrees on the
sky and is the most sensitive large-scale survey of the region to date.
Distances to the constituent molecular clouds of the complex, estimated from an
analysis of foreground and background stars, have provided information on the
three dimensional structure of the entire complex.Comment: Accepted for publication in Astronomy and Astrophysics. 19 pages with
17 colour figures - 39 if you count the sub-figures separately. The figures
here have been bit-mapped with some loss of quality and beauty. The paper
version in A&A will be in greyscale with the on-line version in colour. In
the meantime the colour version can be obtained by following links at
http://www.star.bris.ac.uk/mrwm . The 9MB PostScript is recommended if you
have appropriate bandwidth or otherwise the 2.3MB PDF is usabl
Long-term functional outcome of distal radius fractures is associated with early post-fracture bone stiffness of the fracture region:An HR-pQCT exploratory study
\u3cp\u3eIdentifying determinants of long-term functional outcome after a distal radius fracture is challenging. Previously, we reported on the association between early HR-pQCT measurements and clinical outcome 12 weeks after a conservatively treated distal radius fracture. We extended the follow-up and assessed functional outcome after two years in relation to early HR-pQCT derived bone parameters. HR-pQCT scans of the fracture region were performed in 15 postmenopausal women with a distal radius fracture at 1-2 (baseline), 3-4 weeks and 26 months post-fracture. Additionally, the contralateral distal radius was scanned at baseline. Bone density, micro-architecture parameters and bone stiffness using micro-finite element analysis (μFEA) were evaluated. During all visits, wrist pain and function were assessed using the patient-rated wrist evaluation questionnaire (PRWE), quantifying functional outcome with a score between 0 and 100. Two-year PRWE was associated with torsional and bending stiffness 3-4 weeks post-fracture (R2: 0.49, p = 0.006 and R2: 0.54, p = 0.003, respectively). In contrast, early micro-architecture parameters of the fracture region or contralateral bone parameters did not show any association with long-term outcome. This exploratory study indicates that HR-pQCT with μFEA performed within four weeks after a distal radius fracture captures biomechanical fracture characteristics that are associated with long-term functional outcome and therefore could be a valuable early outcome measure in clinical trials and clinical practice.\u3c/p\u3
Does police size matter?:A review of the evidence regarding restructuring police organisations
Restructuring and merging public sector organisations is often seen as a way to enhance efficiency and efficacy. There is ongoing debate about the impact of police force sizes, structures and mergers as police organisations attempt to adapt to reductions in their budgets and changes in patterns of criminality. The article reviews the evidence regarding key aspects of police reform: finding mixed evidence regarding the links between size and performance, while noting risks that mergers may impair local policing. The article discusses the impact of mergers on protective services, governance and accountability, while also discussing potential risks and opportunities associated with the merger process itself. The review finds significant gaps in the available evidence, and significant opportunities to expand the evidence base on this topic. Given current gaps in the evidence regarding size, efficacy and efficiency, it is important to give due consideration to symbolic and rhetorical aspects of mergers
Grain growth signatures in the protoplanetary discs of Chamaeleon and Lupus
We present ATCA results of a 3 and 7 mm continuum survey of 20 T Tauri stars
in the Chamaeleon and Lupus star forming regions. This survey aims to identify
protoplanetary discs with signs of grain growth. We detected 90% of the sources
at 3 and 7 mm, and determined the spectral slopes, dust opacity indices and
dust disc masses. We also present temporal monitoring results of a small
sub-set of sources at 7, 15 mm and 3+6 cm to investigate grain growth to cm
sizes and constrain emission mechanisms in these sources. Additionally, we
investigated the potential correlation between grain growth signatures in the
infrared (10 \mu m silicate feature) and millimetre (1-3 mm spectral slope,
{\alpha}). Eleven sources at 3 and 7 mm have dominant thermal dust emission up
to 7 mm, with 7 of these having a 1-3 mm dust opacity index less than unity,
suggesting grain growth up to at least mm sizes. The Chamaeleon sources
observed at 15 mm and beyond show the presence of excess emission from an
ionised wind and/or chromo- spheric emission. Long-timescale monitoring at 7 mm
indicated that cm-sized pebbles are present in at least four sources.
Short-timescale monitoring at 15 mm suggests the excess emission is from
thermal free-free emission. Finally, a weak correlation was found between the
strength of the 10 \mum feature and {\alpha}, suggesting simultaneous dust
evolution of the inner and outer parts of the disc. This survey shows that
grain growth up to cm-sized pebbles and the presence of excess emission at 15
mm and beyond are common in these systems, and that temporal monitoring is
required to disentangle these emission mechanisms.Comment: 31 pages, 13 figures, 11 tables, accepted for publication in MNRA
A VLT/NACO Survey for Triple and Quadruple Systems among Visual Pre-Main Sequence Binaries
This paper describes a systematic search for high-order multiplicity among
wide visual Pre-Main Sequence (PMS) binaries. We conducted an Adaptive Optics
survey of a sample of 58 PMS wide binaries from various star-forming regions,
which include 52 T Tauri systems with mostly K- and M-type primaries, with the
NIR instrument NACO at the VLT. Of these 52 systems, 7 are found to be triple
(2 new) and 7 quadruple (1 new). The new close companions are most likely
physically bound based on their probability of chance projection and, for some
of them, on their position on a color-color diagram. The corresponding degree
of multiplicity among wide binaries (number of triples and quadruples divided
by the number of systems) is 26.9 +/- 7.2% in the projected separation range
0.07-12 arcsec, with the largest contribution from the Taurus-Auriga cloud. We
also found that this degree of multiplicity is twice in Taurus compared to
Ophiuchus and Chamaeleon for which the same number of sources are present in
our sample. Considering a restricted sample composed of systems at distance
140-190pc, the degree of multiplicity is 26.8 +/- 8.1%, in the separation range
10/14 AU - 1700/2300 AU (30 binaries, 5 triples, 6 quadruples). The observed
frequency agrees with results from previous multiplicity surveys within the
uncertainties, although a significant overabundance of quadruple systems
compared to triple systems is apparent. Tentatively including the spectroscopic
pairs in our restricted sample and comparing the multiplicity fractions to
those measured for solar-type main-sequence stars in the solar neighborhood
leads to the conclusion that both the ratio of triples to binaries and the
ratio of quadruples to triples seems to be in excess among young stars. [...]Comment: 24 pages, accepted for publication in Astronomy & Astrophysic
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
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