CO, 13CO, and C18O J = 3–2 observations are presented of the Ophiuchus molecular cloud. The 13CO and C18O emission is dominated by the Oph A clump, and the Oph B1, B2, C, E, F, and J regions. The ...optically thin(ner) C18O line is used as a column density tracer, from which the gravitational binding energy is estimated to be 4.5 × 1039 J (2282 M⊙ km2 s−2). The turbulent kinetic energy is 6.3 × 1038 J (320 M⊙ km2 s−2), or seven times less than this, and therefore the Oph cloud as a whole is gravitationally bound. 30 protostars were searched for high-velocity gas, with 8 showing outflows, and 20 more having evidence of high-velocity gas along their lines of sight. The total outflow kinetic energy is 1.3 × 1038 J (67 M⊙ km2 s−2), corresponding to 21 per cent of the cloud's turbulent kinetic energy. Although turbulent injection by outflows is significant, but does not appear to be the dominant source of turbulence in the cloud. 105 dense molecular clumplets were identified, which had radii ∼0.01–0.05 pc, virial masses ∼0.1–12 M⊙, luminosities ∼0.001–0.1 K km s−1 pc−2, and excitation temperatures ∼10–50 K. These are consistent with the standard Giant Molecular Cloud (GMC) based size–linewidth relationships, showing that the scaling laws extend down to size scales of hundredths of a parsec, and to subsolar-mass condensations. There is however no compelling evidence that the majority of clumplets are undergoing free-fall collapse, nor that they are pressure confined.
This white paper gives a brief summary of the time domain science that has been performed with the JCMT in recent years and highlights the opportunities for continuing work in this field over the ...next decade. The main focus of this document is the JCMT Transient Survey, a large program initiated in 2015 to measure the frequency and amplitude of variability events associated with protostars in nearby star-forming regions. After summarising the major accomplishments so far, an outline is given for extensions to the current survey, featuring a discussion on what will be possible with the new 850 micron camera that is expected to be installed in late 2022. We also discuss possible applications of submillimetre monitoring to active galactic nuclei, X-ray binaries, asymptotic giant branch stars, and flare stars.
The majority of the ultimate main-sequence mass of a star is assembled in the
protostellar phase, where a forming star is embedded in an infalling envelope
and encircled by a protoplanetary disk. ...Studying mass accretion in protostars
is thus a key to understanding how stars gain their mass and ultimately how
their disks and planets form and evolve. At this early stage, the dense
envelope reprocesses most of the luminosity generated by accretion to
far-infrared and submillimeter wavelengths. Time-domain photometry at these
wavelengths is needed to probe the physics of accretion onto protostars, but
variability studies have so far been limited, in large part because of the
difficulty in accessing these wavelengths from the ground. We discuss the
scientific progress that would be enabled with far-infrared and submillimeter
programs to probe protostellar variability in the nearest kiloparsec.
We present observations of the Cepheus Flare obtained as part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Legacy Survey (GBLS) with the SCUBA-2 instrument. We produce a catalogue of ...sources found by SCUBA-2, and separate these into starless cores and protostars. We determine masses and densities for each of our sources, using source temperatures determined by the Herschel Gould Belt Survey. We compare the properties of starless cores in four different molecular clouds: L1147/58, L1172/74, L1251 and L1228. We find that the core mass functions for each region typically show shallower-than-Salpeter behaviour. We find that L1147/58 and L1228 have a high ratio of starless cores to Class II protostars, while L1251 and L1174 have a low ratio, consistent with the latter regions being more active sites of current star formation, while the former are forming stars less actively. We determine that, if modelled as thermally-supported Bonnor-Ebert spheres, most of our cores have stable configurations accessible to them. We estimate the external pressures on our cores using archival \(^{13}\)CO velocity dispersion measurements and find that our cores are typically pressure-confined, rather than gravitationally bound. We perform a virial analysis on our cores, and find that they typically cannot be supported against collapse by internal thermal energy alone, due primarily to the measured external pressures. This suggests that the dominant mode of internal support in starless cores in the Cepheus Flare is either non-thermal motions or internal magnetic fields.
CO, \(^{13}\)CO and C\(^{18}\)O \({\it J}\) = 3--2 observations are presented of the Ophiuchus molecular cloud. The \(^{13}\)CO and C\(^{18}\)O emission is dominated by the Oph A clump, and the Oph ...B1, B2, C, E, F and J regions. The optically thin(ner) C\(^{18}\)O line is used as a column density tracer, from which the gravitational binding energy is estimated to be \(4.5 \times 10^{39}\) J (2282 \(M_\odot\) km\(^2\) s\(^{-2}\)). The turbulent kinetic energy is \(6.3 \times 10^{38}\) J (320 \(M_\odot\) km\(^2\) s\(^{-2}\)), or 7 times less than this, and therefore the Oph cloud as a whole is gravitationally bound. Thirty protostars were searched for high velocity gas, with eight showing outflows, and twenty more having evidence of high velocity gas along their lines-of-sight. The total outflow kinetic energy is \(1.3 \times 10^{38}\) J (67 \(M_\odot\) km\(^2\) s\(^{-2}\)), corresponding to 21\(\%\) of the cloud's turbulent kinetic energy. Although turbulent injection by outflows is significant, but does \({\it not}\) appear to be the dominant source of turbulence in the cloud. 105 dense molecular clumplets were identified, which had radii \(\sim\) 0.01--0.05 pc, virial masses \(\sim\) 0.1--12 \(M_\odot\), luminosities \(\sim\) 0.001--0.1 K~km s\(^{-1}\) pc\(^{-2}\), and excitation temperatures \(\sim\) 10--50K. These are consistent with the standard GMC based size-line width relationships, showing that the scaling laws extend down to size scales of hundredths of a parsec, and to sub solar-mass condensations. There is however no compelling evidence that the majority of clumplets are undergoing free-fall collapse, nor that they are pressure confined.
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