Mid-J CO Shock Tracing Observations of Infrared Dark Clouds I

Infrared dark clouds (IRDCs) are dense, molecular structures in the interstellar medium that can harbour sites of high-mass star formation. IRDCs contain supersonic turbulence, which is expected to generate shocks that locally heat pockets of gas within the clouds. We present observations of the CO J = 8-7, 9-8, and 10-9 transitions, taken with the Herschel Space Observatory, towards four dense, starless clumps within IRDCs (C1 in G028.37+00.07, F1 and F2 in G034.43+0007, and G2 in G034.77-0.55). We detect the CO J = 8-7 and 9-8 transitions towards three of the clumps (C1, F1, and F2) at intensity levels greater than expected from photodissociation region (PDR) models. The average ratio of the 8-7 to 9-8 lines is also found to be between 1.6 and 2.6 in the three clumps with detections, significantly smaller than expected from PDR models. These low line ratios and large line intensities strongly suggest that the C1, F1, and F2 clumps contain a hot gas component not accounted for by standard PDR models. Such a hot gas component could be generated by turbulence dissipating in low velocity shocks.Comment: 14 pages, 8 figures, 5 tables, accepted by A&A, minor updates to match the final published versio

Tuna fisheries in India: Recent trends

Tuna is one of the least exploited resources of the Indian seas accounting for 0.98 % of the total marine fish catch of India at the 1978 level. On the other hand tuna resources have been exploited by countries such as Japan, Korea and Taiwan from the Indian Ocean. Relevant portions of the recommendations of the 'Symposium on scombroid fishes' held at Mandapam camp. The authorities involved with the planning of the Indian Ocean Expedition give due consideration to gathering and collating the information which should be useful in aiding the development of high seas fisheries for scombroid fishes in the Indian Ocean. In the context of these developments and the need for efficient utilisation of the resources of the Exclusive Economic Zone, a brief account on the trend in the tuna fisheries in the country is presented here

Is copyright blind to the visual?

This article argues that, with respect to the copyright protection of works of visual art, the general uneasiness that has always pervaded the relationship between copyright law and concepts of creativity produces three anomalous results. One of these is that copyright lacks much in the way of a central concept of 'visual art' and, to the extent that it embraces any concept of the 'visual', it is rooted in the rhetorical discourse of the Renaissance. This means that copyright is poorly equipped to deal with modern developments in the visual arts. Secondly, the pervasive effect of rhetorical discourse appears to have made it particularly difficult for copyright law to strike a meaningful balance between protecting creativity and permitting its use in further creative works. Thirdly, just when rhetorical discourse might have been useful in identifying the significance and materiality of the unique one-off work of visual art, copyright law chooses to ignore its implications

The JCMT Gould Belt Survey: properties of star-forming filaments in Orion A North

We develop and apply a Hessian-based filament detection algorithm to submillimetre continuum observations of Orion A North. The resultant filament radial density profiles are fitted with beam-convolved line-of-sight Plummer-profiles using Markov chain Monte Carlo techniques. The posterior distribution of the radial decay parameter demonstrates that the majority of filaments exhibit p = 1.5–3, with a mode at p = 2.2, suggesting deviation from the Ostriker p = 4 isothermal, equilibrium, self-gravitating cylinder. The spatial distribution of young stellar objects relative to the high column density filaments is investigated, yielding a lower limit on the star-forming age of the integral-shaped filament ∼1.4 Myr. Additionally, inferred lifetimes of filaments are examined which suggest long-term filament accretion, varying rates of star formation, or both. Theoretical filament stability measures are determined with the aid of HARP C18O J = 3–2 observations and indicate that the majority of filaments are gravitationally subcritical, despite the presence of young protostars. The results from this investigation are consistent with the one-dimensional accretion flow filament model recently observed in numerical simulations

The spine of the swan: A Herschel study of the DR21 ridge and filaments in Cygnus X

In order to characterise the cloud structures responsible for the formation of high-mass stars, we present Herschel observations of the DR21 environment. Maps of the column density and dust temperature unveil the structure of the DR21 ridge and several connected filaments. The ridge has column densities larger than 1e23/cm^2 over a region of 2.3 pc^2. It shows substructured column density profiles and branching into two major filaments in the north. The masses in the studied filaments range between 130 and 1400 Msun whereas the mass in the ridge is 15000 Msun. The accretion of these filaments onto the DR21 ridge, suggested by a previous molecular line study, could provide a continuous mass inflow to the ridge. In contrast to the striations seen in e.g., the Taurus region, these filaments are gravitationally unstable and form cores and protostars. These cores formed in the filaments potentially fall into the ridge. Both inflow and collisions of cores could be important to drive the observed high-mass star formation. The evolutionary gradient of star formation running from DR21 in the south to the northern branching is traced by decreasing dust temperature. This evolution and the ridge structure can be explained by two main filamentary components of the ridge that merged first in the south.Comment: 8 pages, 5 figures, accepted for publication as a Letter in Astronomy and Astrophysic

The 28 November 2020 Landslide, Tsunami, and Outburst Flood – A Hazard Cascade Associated With Rapid Deglaciation at Elliot Creek, British Columbia, Canada

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m3 of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km2 glacier lake and producing >100-m high run-up. Water overtopped the lake outlet and scoured a 10-km long channel before depositing debris on a 2-km2 fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real-time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose

Microfinance at the Margin: Experimental Evidence from Bosnia and Herzegovina

We use an RCT to analyse the impact of microcredit on poverty reduction in Bosnia. The study population are loan applicants that would normally have just been rejected based on regular screening. We find that access to credit allowed borrowers to start and expand small-scale businesses. Households that already had a business and where the borrower had more education ran down their savings, presumably to complement the loan and to achieve the minimum amount necessary to expand their business. In less-educated households, however, consumption went down. A key new result is that there was a substantial increase in the labor supply of young adults (16-19 year olds). This was accompanied by a reduction in school attendance

The JCMT Transient Survey: Identifying Submillimeter Continuum Variability over Several Year Timescales Using Archival JCMT Gould Belt Survey Observations

This is the final version of the article. Available from American Astronomical Society via the DOI in this record.Investigating variability at the earliest stages of low-mass star formation is fundamental in understanding how a protostar assembles mass. While many simulations of protostellar disks predict non-steady accretion onto protostars, deeper investigation requires robust observational constraints on the frequency and amplitude of variability events characterized across the observable SED. In this study, we develop methods to robustly analyze repeated observations of an area of the sky for submillimeter variability in order to determine constraints on the magnitude and frequency of deeply embedded protostars. We compare 850 μm JCMT Transient Survey data with archival JCMT Gould Belt Survey data to investigate variability over 2–4 year timescales. Out of 175 bright, independent emission sources identified in the overlapping fields, we find seven variable candidates, five of which we classify as Strong, and the remaining two we classify as Extended to indicate that the latter are associated with larger-scale structure. For the Strong variable candidates, we find an average fractional peak brightness change per year of $| 4.0| \% \,{\mathrm{yr}}^{-1}$, with a standard deviation of $2.7 \% \,{\mathrm{yr}}^{-1}$. In total, 7% of the protostars associated with 850 μm emission in our sample show signs of variability. Four of the five Strong sources are associated with a known protostar. The remaining source is a good follow-up target for an object that is anticipated to contain an enshrouded, deeply embedded protostar. In addition, we estimate the 850 μm periodicity of the submillimeter variable source, EC 53, to be 567 ± 32 days, based on the archival Gould Belt Survey data.Steve Mairs was partially supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada graduate scholarship program. Doug Johnstone is supported by the National Research Council of Canada and by an NSERC Discovery Grant. Gregory Herczeg is supported by general grant 11473005 awarded by the National Science Foundation of China. Andy Pon received partial salary support from a Canadian Institute for Theoretical Astrophysics (CITA) National Fellowship. Miju Kang was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT, & Future Planning (No. NRF-2015R1C1A1A01052160). J.-E. Lee was supported by the Basic Science Research Program through the National Research Foundation of Korea (grant No. NRF-2015R1A2A2A01004769) and the Korea Astronomy and Space Science Institute under the R&D program (Project No. 2015-1-320-18) supervised by the Ministry of Science and ICT. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The James Clerk Maxwell Telescope is operated by the East Asian Observatory on behalf of the National Astronomical Observatory of Japan, Academia Sinica Institute of Astronomy and Astrophysics, the Korea Astronomy and Space Science Institute, the National Astronomical Observatories of China, and the Chinese Academy of Sciences (Grant No. XDB09000000), with additional funding support from the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada. The James Clerk Maxwell Telescope has historically been operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the National Research Council of Canada, and the Netherlands Organisation for Scientific Research. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation. The identification number for the JCMT Transient Survey data used in this paper is M16AL001. The identification numbers for the archival Gould Belt Survey data used in this paper are MJLSG31, MJLSG32, MJLSG33, MJLSG38, and MJLSG41. The authors thank the JCMT staff for their support of the data collection and reduction efforts. This research has made use of NASA's Astrophysics Data System and the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada, with the support of the Canadian Space Agency. The authors would especially like to thank Chang Won Lee and Harriet Parsons for their useful insights and suggestions, along with the extended JCMT Transient Team21 for their support. This research used the services of the Canadian Advanced Network for Astronomy Research (CANFAR), which in turn is supported by CANARIE, Compute Canada, University of Victoria, the National Research Council of Canada, and the Canadian Space Agency. This research made use of APLpy, an open-source plotting package for Python hosted at http://aplpy.github.com, and matplotlib, a 2D plotting library for Python (Hunter 2007)

The JCMT Gould Belt Survey: A First Look at IC 5146

We present 450 and 850 μm submillimeter continuum observations of the IC 5146 star-forming region taken as part of the James Clerk Maxwell Telescope Gould Belt Survey. We investigate the location of bright submillimeter (clumped) emission with the larger-scale molecular cloud through comparison with extinction maps, and find that these denser structures correlate with higher cloud column density. Ninety-six individual submillimeter clumps are identified using FellWalker, and their physical properties are examined. These clumps are found to be relatively massive, ranging from 0.5 M⊙ to 116 M⊙ with a mean mass of 8 M⊙ and a median mass of 3.7 M⊙. A stability analysis for the clumps suggests that the majority are (thermally) Jeans stable, with M/MJ < 1. We further compare the locations of known protostars with the observed submillimeter emission, finding that younger protostars, i.e., Class 0 and I sources, are strongly correlated with submillimeter peaks and that the clumps with protostars are among the most Jeans unstable. Finally, we contrast the evolutionary conditions in the two major star-forming regions within IC 5146: the young cluster associated with the Cocoon Nebula and the more distributed star formation associated with the Northern Streamer filaments. The Cocoon Nebula appears to have converted a higher fraction of its mass into dense clumps and protostars, the clumps are more likely to be Jeans unstable, and a larger fraction of these remaining clumps contain embedded protostars. The Northern Streamer, however, has a larger number of clumps in total and a larger fraction of the known protostars are still embedded within these clumps

The JCMT Transient Survey: Stochastic and Secular Variability of Protostars and Disks In the Submillimeter Region Observed over 18 Months

This is the final version of the article. Available from American Astronomical Society via the DOI in this record.We analyze results from the first 18 months of monthly submillimeter monitoring of eight star-forming regions in the JCMT Transient Survey. In our search for stochastic variability in 1643 bright peaks, only the previously identified source, EC 53, shows behavior well above the expected measurement uncertainty. Another four sources—two disks and two protostars—show moderately enhanced standard deviations in brightness, as expected for stochastic variables. For the two protostars, this apparent variability is the result of single epochs that are much brighter than the mean. In our search for secular brightness variations that are linear in time, we measure the fractional brightness change per year for 150 bright peaks, 50 of which are protostellar. The ensemble distribution of slopes is well fit by a normal distribution with σ ~ 0.023. Most sources are not rapidly brightening or fading at submillimeter wavelengths. Comparison against time-randomized realizations shows that the width of the distribution is dominated by the uncertainty in the individual brightness measurements of the sources. A toy model for secular variability reveals that an underlying Gaussian distribution of linear fractional brightness change σ = 0.005 would be unobservable in the present sample, whereas an underlying distribution with σ = 0.02 is ruled out. Five protostellar sources, 10% of the protostellar sample, are found to have robust secular measures deviating from a constant flux. The sensitivity to secular brightness variations will improve significantly with a sample over a longer time duration, with an improvement by factor of two expected by the conclusion of our 36 month survey.The JCMT is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan, Academia Sinica Institute of Astronomy and Astrophysics, the Korea Astronomy and Space Science Institute, the National Astronomical Observatories of China and the Chinese Academy of Sciences (Grant No. XDB09000000), with additional funding support from the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada. The identification number for the JCMT Transient Survey under which the SCUBA-2 data used in this paper can be found is M16AL001. The authors thank the JCMT staff for their support of the GBS team in data collection and reduction efforts. The Starlink software (Currie et al. 2014) is supported by the East Asian Observatory. This research has made use of NASA's Astrophysics Data System and the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency. This research used the services of the Canadian Advanced Network for Astronomy Research (CANFAR), which in turn is supported by CANARIE, Compute Canada, University of Victoria, the National Research Council of Canada, and the Canadian Space Agency