We present a generalization of the giant molecular cloud identification problem based on cluster analysis. The method we designed, SCIMES (Spectral Clustering for Interstellar Molecular Emission ...Segmentation) considers the dendrogram of emission in the broader framework of graph theory and utilizes spectral clustering to find discrete regions with similar emission properties. For Galactic molecular cloud structures, we show that the characteristic volume and/or integrated CO luminosity are useful criteria to define the clustering, yielding emission structures that closely reproduce 'by-eye' identification results. SCIMES performs best on well-resolved, high-resolution data, making it complementary to other available algorithms. Using ...CO(1-0) data for the Orion-Monoceros complex, we demonstrate that SCIMES provides robust results against changes of the dendrogram-construction parameters, noise realizations and degraded resolution. By comparing SCIMES with other cloud decomposition approaches, we show that our method is able to identify all canonical clouds of the Orion-Monoceros region, avoiding the overdivision within high-resolution survey data that represents a common limitation of several decomposition algorithms. The Orion-Monoceros objects exhibit hierarchies and size-line width relationships typical to the turbulent gas in molecular clouds, although 'the Scissors' region deviates from this common description. SCIMES represents a significant step forward in moving away from pixel-based cloud segmentation towards a more physical-oriented approach, where virtually all properties of the ISM can be used for the segmentation of discrete objects. (ProQuest: ... denotes formulae/symbols omitted.)
ABSTRACT
ATLASGAL is an 870-µm dust survey of 420 deg2 the inner Galactic plane and has been used to identify ∼10 000 dense molecular clumps. Dedicated follow-up observations and complementary ...surveys are used to characterize the physical properties of these clumps, map their Galactic distribution, and investigate the evolutionary sequence for high-mass star formation. The analysis of the ATLASGAL data is ongoing: We present an up-to-date version of the catalogue. We have classified 5007 clumps into four evolutionary stages (quiescent, protostellar, young stellar objects and H ii regions) and find similar numbers of clumps in each stage, suggesting a similar lifetime. The luminosity-to-mass (Lbol/Mfwhm) ratio curve shows a smooth distribution with no significant kinks or discontinuities when compared to the mean values for evolutionary stages indicating that the star formation process is continuous and that the observational stages do not represent fundamentally different stages or changes in the physical mechanisms involved. We compare the evolutionary sample with other star formation tracers (methanol and water masers, extended green objects and molecular outflows) and find that the association rates with these increases as a function of evolutionary stage, confirming that our classification is reliable. This also reveals a high association rate between quiescent sources and molecular outflows, revealing that outflows are the earliest indication that star formation has begun and that star formation is already ongoing in many of the clumps that are dark even at 70 µm.
Rotation of molecular clouds in M 51 Braine, J.; Hughes, A.; Rosolowsky, E. ...
Astronomy and astrophysics (Berlin),
01/2020, Letnik:
633
Journal Article
Recenzirano
Odprti dostop
The grand-design spiral galaxy M 51 was observed at 40 pc resolution in CO(1–0) by the PAWS project. A large number of molecular clouds were identified and we search for velocity gradients in two ...high signal-to-noise subsamples, containing 682 and 376 clouds. The velocity gradients are found to be systematically prograde oriented, as was previously found for the rather flocculent spiral M 33. This strongly supports the idea that the velocity gradients reflect cloud rotation, rather than more random dynamical forces, such as turbulence. Not only are the gradients prograde, but their
∂v
/
∂x
and
∂v
/
∂y
coefficients follow galactic shear in sign, although with a lower amplitude. No link is found between the orientation of the gradient and the orientation of the cloud. The values of the cloud angular momenta appear to be an extension of the values noted for galactic clouds despite the orders of magnitude difference in cloud mass. Roughly 30% of the clouds show retrograde velocity gradients. For a strictly rising rotation curve, as in M 51, gravitational contraction would be expected to yield strictly prograde rotators within an axisymmetric potential. In M 51, the fraction of retrograde rotators is found to be higher in the spiral arms than in the disk as a whole. Along the leading edge of the spiral arms, a majority of the clouds are retrograde rotators. While this work should be continued on other nearby galaxies, the M 33 and M 51 studies have shown that clouds rotate and that they rotate mostly prograde, although the amplitudes are not such that rotational energy is a significant support mechanism against gravitation. In this work, we show that retrograde rotation is linked to the presence of a spiral gravitational potential.
Summary
Background
Chronic spontaneous urticaria (CSU) is a common skin disease, but there is a paucity of precise epidemiological data on this disease.
Objectives
To obtain information on the ...epidemiology of CSU in Italy.
Methods
The data source was the Health Search IMS Health Longitudinal Patient Database. The study population was formed by patients aged ≥ 15 years, registered with a total of 700 general practitioners, homogeneously distributed across Italy. An algorithm based on the International Classification of Diseases, ninth revision, Clinical Modification was used for the identification of patients with CSU. The annual prevalence and incidence rates of CSU over a 12‐year period (2002–2013) were estimated, along with demographic and clinical determinants.
Results
The annual prevalence of CSU ranged from 0·02% in 2002 to 0·38% in 2013. The incidence was 0·10–1·50 per 1000 person‐years. For both prevalence and incidence rates, female patients outnumbered male. The risk of CSU was statistically significantly higher in the presence of the following variables: obesity; anxiety, dissociative and somatoform disorders; malignancies; use of immunosuppressive drugs; and chronic use of systemic corticosteroids. History of autoimmune thyroiditis showed a trend towards an increased risk of CSU, though it was not statistically significant. Smoking was associated with a significantly reduced risk of CSU.
Conclusions
Our findings on CSU prevalence are consistent with those obtained in previous studies. Furthermore, this large population‐based study provides important information regarding the association of CSU with demographic and clinical determinants, which have been examined in the primary‐care setting.
What's already known about this topic?
Precise information on the epidemiology of chronic spontaneous urticaria (CSU) in Italy is lacking.
What does this study add?
Annual incidence and prevalence rates of CSU in Italy were calculated from 2002 to 2013 using data from a national database of general practitioners.
Demographic and clinical determinants associated with the occurrence of CSU were determined.
Pompilidae are a cosmopolitan family of aculeate parasitoid wasps with 24 extinct species. Here, we provide a new species description for an enigmatic species of Pepsinae: Paleogenia indomini Colombo ...& Waichert sp. nov. The new taxon is easily distinguished from congeners by having a long tibial spur, ~0.8× longer than the first tarsomere, and by the presence of a large basal pale line extending medially on the clypeus. A key for the species of Paleogenia is provided.
zoobank.org:pub:1C8D3CD5-1215-46B1-9742-658B2A50A40C
zoobank.org:act:E1E412D6-6D1F-49E9-B62C-F620CE500D5F
The flat wasp family Bethylidae Haliday lacks global scale literature on their alpha taxonomy. The only world revision for the family was by Kieffer in 1914 and is fully out of date and somewhat ...useless; the only catalog for the family was made by Gordh Móczár in 1990 and does not include hundreds of changes made since then; and the most recent world genera keys were proposed by Terayama in 2003, but do not reflect the current knowledge we have for the family. Given this scenario, we present a global guide of Bethylidae with diagnoses, taxonomic evaluation, keys, and a checklist of all their extant genera and subfamilies. We visited the main collections around the world, analyzed about 2,000 holotypes, and examined at least 400,000 specimens. To eliminate homonymies, we add the prefix "neo" to the original specific epithet when possible. The family is now composed by 2,920 species allocated in 96 genera distributed in eight subfamilies: Bethylinae, Pristocerinae, Epyrinae, Mesitiinae, Scleroderminae, Lancepyrinae, Holopsenellinae and Protopristocerinae. The latter three are extinct. One new family-group synonym is proposed: Fushunochrysidae Hong syn. nov. of Bethylidae. Two incertae sedis genera are allocated into Bethylinae: Cretobethylellus Rasnytsyn and Omaloderus Walker. One new genus-group synonym is revalidated: Pristepyris Kieffer stat. rev. from Acrepyris Kieffer. Sixteen new genus-group synonyms are proposed: Fushunochrysites Hong syn. nov. and Sinibethylus Hong syn. nov. of Eupsenella Westwood; Messoria Meunier syn. nov. of Goniozus Förster; Acrepyris Kieffer syn. nov. of Pristepyris Kieffer; Apristocera Kieffer syn. nov. and Parapristocera Brues syn. nov. of Pristocera Klug; Usakosia Kieffer syn. nov. of Prosapenesia Kieffer; Isobrachium Förster syn. nov., Leptepyris Kieffer syn. nov., Neodisepyris Kurian syn. nov., Rhabdepyris Kieffer syn. nov. of Epyris Westwood; Codorcas Nagy syn. nov., Hamusmus Argaman syn. nov. and Ukayakos Argaman syn. nov. of Heterocoelia Dahlbom; Domonkos Argaman syn. nov. of Incertosulcus Móczár; Ateleopterus Förster syn. nov. of Sclerodermus Latreille. One new genus-group synonym is revalidated: Topcobius Nagy syn. rev. of Sulcomesitius Móczár. One new genus-group revalidation is proposed: Incertosulcus Móczár stat. rev. from Anaylax Móczár. The following species-group nomenclatural acts are established: 153 new or revalidated combinations, 16 new names to avoid secondary homonyms, 11 species with revalidated status, and one synonym. Keys to the subfamilies and genera are provided. The text is supported by 599 illustrations organized onto 92 plates.
A 3D fully coupled hydromechanical model for the simulation of fluid-driven fracture propagation through poroelastic saturated media is presented and compared to several analytical or numerical ...benchmarks. The hydromechanical coupling in the porous matrix is derived within the framework of the generalized Biot theory and the fluid flow in the fractures satisfies the lubrication equation. The presence and propagation of fluid-driven fractures is handled with the extended finite element method and the propagation of the fluid-driven fractures is governed by a mixed linear cohesive law relying on a stable mortar formalism. A comparison between numerical results and a semi-analytical solution for plane fluid-driven fractures in porous media assess the validity of the proposed model. Then, a procedure for the propagation of fluid-driven fractures on non predefined paths is detailed. In particular, the fracture reorientation angle is computed exclusively from cohesive quantities. Various numerical experiments are performed to study the interferences between neighboring fluid-driven fractures as well as the reorientation of fluid-driven fractures under complex stress conditions. Finally, the model is extended to discontinuity junctions and an application to arrays of vertical fractures initiated from horizontal wells is presented.
We present a study correlating the spatial locations of young star clusters with those of molecular clouds in NGC 5194, in order to investigate the time-scale over which clusters separate from their ...birth clouds. The star cluster catalogues are from the Legacy ExtraGalactic UV Survey (LEGUS) and the molecular clouds from the Plateau de Bure Interefrometer Arcsecond Whirpool Survey (PAWS). We find that younger star clusters are spatially closer to molecular clouds than older star clusters. The median age for clusters associated with clouds is 4 Myr, whereas it is 50 Myr for clusters that are sufficiently separated from a molecular cloud to be considered unassociated. After ∼6 Myr, the majority of the star clusters lose association with their molecular gas. Younger star clusters are also preferentially located in stellar spiral arms where they are hierarchically distributed in kpc-size regions for 50-100 Myr before dispersing. The youngest star clusters are more strongly clustered, yielding a two-point correlation function with α = -0.28 ± 0.04, than the giant molecular cloud (GMCs) (α = -0.09 ± 0.03) within the same PAWS field. However, the clustering strength of the most massive GMCs, supposedly the progenitors of the young clusters for a star formation efficiency of a few per cent, is comparable (α = -0.35 ± 0.05) to that of the clusters. We find a galactocentric dependence for the coherence of star formation, in which clusters located in the inner region of the galaxy reside in smaller star-forming complexes and display more homogeneous distributions than clusters further from the centre. This result suggests a correlation between the survival of a cluster complex and its environment.
PDF
