The development of a protoplanetary disk from its natal envelope

Class 0 protostars, the youngest type of young stellar objects, show many signs of rapid development from their initial, spheroidal configurations, and therefore are studied intensively for details of the formation of protoplanetary disks within protostellar envelopes. At millimetre wavelengths, kinematic signatures of collapse have been observed in several such protostars, through observations of molecular lines that probe their outer envelopes. It has been suggested that one or more components of the proto-multiple system NGC 1333-IRAS 4 (refs 1, 2) may display signs of an embedded region that is warmer and denser than the bulk of the envelope(3,4). Here we report observations that reveal details of the core on Solar System dimensions. We detect in NGC 1333-IRAS 4B a rich emission spectrum of H2O, at wavelengths 20-37 mu m, which indicates an origin in extremely dense, warm gas. We can model the emission as infall from a protostellar envelope onto the surface of a deeply embedded, dense disk, and therefore see the development of a protoplanetary disk. This is the only example of mid-infrared water emission from a sample of 30 class 0 objects, perhaps arising from a favourable orientation; alternatively, this may be an early and short-lived stage in the evolution of a protoplanetary disk.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62894/1/nature06087.pd

The Alchemist

JOURThis is the final version of the article. It was first published by IOP Publishing for the Royal Astronomical Society via http://dx.doi.org/10.3847/0004-637X/817/2/167We present a first look at the SCUBA-2 observations of three sub-regions of the Orion B molecular cloud: LDN 1622, NGC 2023/2024, and NGC 2068/2071, from the JCMT Gould Belt Legacy Survey. We identify 29, 564, and 322 dense cores in L1622, NGC 2023/2024, and NGC 2068/2071 respectively, using the SCUBA-2 850 μm map, and present their basic properties, including their peak fluxes, total fluxes, and sizes, and an estimate of the corresponding 450 μm peak fluxes and total fluxes, using the FellWalker source extraction algorithm. Assuming a constant temperature of 20 K, the starless dense cores have a mass function similar to that found in previous dense core analyses, with a Salpeter-like slope at the high-mass end. The majority of cores appear stable to gravitational collapse when considering only thermal pressure; indeed, most of the cores which have masses above the thermal Jeans mass are already associated with at least one protostar. At higher cloud column densities, above 1–2 × 1023 cm‑2, most of the mass is found within dense cores, while at lower cloud column densities, below 1 × 1023 cm‑2, this fraction drops to 10% or lower. Overall, the fraction of dense cores associated with a protostar is quite small (<8%), but becomes larger for the densest and most centrally concentrated cores. NGC 2023/2024 and NGC 2068/2071 appear to be on the path to forming a significant number of stars in the future, while L1622 has little additional mass in dense cores to form many new stars

A non-absolutely convergent integral which admits C1C^1-transformations

This is the final version of the article. Available from OUP via the DOI in this record.This paper presents observations of the Lupus I molecular cloud at 450 and 850 µm with SCUBA-2 as part of the James Clerk Maxwell Telescope Gould Belt Survey (JCMT GBS). Nine compact sources, assumed to be the disks of young stellar objects (YSOs), twelve extended protostellar, pre-stellar and starless cores, and one isolated, low luminosity protostar, are detected in the region. Spectral Energy Distributions (SEDs), including submillimetre fluxes, are produced for 15 YSOs, and each is fitted with the models of Robitaille et al. (2006). The proportion of Class 0 / I protostars is higher than that seen in other Gould Belt regions such as Ophiuchus and Serpens. Circumstellar disk masses are calculated for more evolved sources, while protostellar envelope masses are calculated for protostars. Up to four Very Low Luminosity Objects are found, a large fraction when compared to other Spitzer c2d regions. One YSO has a disk mass greater than the minimum mass solar nebula (MMSN). Twelve starless / protostellar cores are detected by SCUBA-2, and their masses are calculated. The stability of these cores is examined using both the thermal Jeans mass and a turbulent virial mass when possible. Two cores in Lupus I are super-Jeans and contain no known YSOs. One of these cores has a virial parameter of 1.1 ± 0.4, and could therefore be prestellar. The high ratio of Class 0 / I to Class III YSOs (1:1), and the presence of a prestellar core candidate, provides support for the hypothesis that a shock recently triggered star formation in Lupus I.The JCMT has historically been operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council (STFC) 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 programme under which the SCUBA-2 data used in this paper was obtained is MJLSG34. Chris Mowat is supported by an STFC studentship. This research has made use of NASA’s Astrophysics Data System. 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 used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency. Starlink software (Currie et al. 2014) is supported by the East Asian Observatory. MATPLOTLIB is a 2D graphics package used for PYTHON for application development, interactive scripting and publication-quality image generation across user interfaces and operating systems. This research made use of APLPY (Robitaille & Bressert 2012), an open-source plotting package for PYTHON hosted at http://aplpy.github.com. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publication makes use of data products from the 2MASS that is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research uses observations with AKARI, a JAXA project with the participation of ESA. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. 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 authors would also like to thank the anonymous referee for their help in clarifying the content of this paper