1,671 research outputs found
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The influence of shocks on star formation in the OMC1 Ridge
Observations are presented of the OMC1 Ridge (a narrow band of molecular gas containing high-mass embedded sources), in the transitions CN N = 2 - 1, 13CO J = 2 - 1 and 13S J = 5 - 4. Variations in velocities and line widths indicate that three distinct regions are present in the area mapped, and that at least one of these is rotating. The resulting shocks when these fragments collided will have compressed the gas to a density nH2~107-8cm-3, sufficient to trigger collapse and to explain the presence of high-mass stars at the edges of the cloud fragments, rather than in their cores. These observational results support theoretical predictions of the importance of collisions in star formation
X-ray variability of the quasar 3C273
Observations of the quasar 3C273 made during 1975-77 have shown that the X-ray flux varied on a time scale of several months. No similar variation was present in radio and optical data taken at similar times. If this variation results from luminosity variations of a central compact object, then an upper limit of ≤4 x 1017cm can be set on its dimensions
GENIE observations of small scale astrophysical processes in star forming regions and quasars
The VLTI/GENIE configuration will operate using at least 4 of the VLTI
telescopes (and possibly with one or more of the AT telescopes in the future if
adaptive optics become available on them). GENIE effectively can be thought of
as a 'smart' coronagraph, enabling high dynamic range imaging to be achieved at
moderate spatial resolution, with high rejection of the emission of a central
bright point source. However, but this bright source rejection may only provide
a rather moderate image quality (due to the few baselines and transfer function
on the sky). Operated in this way, only limited image reconstruction is
possible since classical radio and millimeter wavelength interferometry
techniques are not directly applicable to the outputs of optical
interferometers because the absolute phases are generally not measured.
However, measurements of visibility and closure phase could lead to situations
where image reconstruction becomes possible. This paper addresses the issue of
whether there are areas outside of the exoplanet search where it might be able
to make a useful impact on astronomy.Comment: Proceedings of the Genie-Darwin Workshop - Hunting for Planet
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Molecular line maps of the Galactic Centre Circumnuclear Disk
Prelimary results are discussed for a long-term programme carried out with the James Clerk Maxwell 15m Telescope, to map the structure and dynamics of the Circumnuclear Disc at the Galactic Centre in a wide range of millimetre and submilletre wavelength molecular line transitions
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CO and CI observations of shock excited gas in IC443C
The blast-wave at the edge of the supernova remnant IC443 is colliding with nearby quiescent gas. In this paper a multi-transition study of CO J = 1 - 0 → J = 4 - 3 is presented of one of these clouds, IC443C, and the detection of atomic carbon, CI, reported. The CO is optically thin with Tex ~ 45K, a measured isotopic ratio CO/13CO = 80, and N(CO) ~ 2 - 4 1017. Atomic carbon emission was detected for the first time in shocked gas only towards the IC443C C-shocked region, with an abundance ratio CI/CO ~ 1.3 - 2.9. CI is overabundant by one order of magnitude compared with quiescent molecular cloud cores, suggesting that shock(s), or an enhanced cosmic ray flux density, has increased the CI/CO ratio. A narrow CO absorption line towards the shocked region IC443G has Tex ~ 13-18K, and nH2 ~ 2-3 103 cm-3, which may be typical of conditions in the pre-shock gas
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LYNDS 379 - a new source of bipolar molecular flow
A study has been made incorporating molecular line CO J = 2-1 and optical star counting techniques of the sharp-edged Lynds dark cloud 379. It is found to lie at a distance of 200 pc, and to have an average extinction, AB, of <2 mag. Molecular mapping has revealed the presence of a new bipolar molecular flow source coincident with a strong IRAS far infrared peak. This indicates the presence of active star formation at the edge of the cloud - possibly as a consequence of the mechanism (such as an interstellar shock) which has led to compression of the edge of L379
Towards a Molecular Inventory of Protostellar Discs
The chemical environment in circumstellar discs is a unique diagnostic of the
thermal, physical and chemical environment. In this paper we examine the
structure of star formation regions giving rise to low mass stars, and the
chemical environment inside them, and the circumstellar discs around the
developing stars.Comment: 9 page PDF, 550 kbyte
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A high resolution millimetre and submillimetre study of W3
The continuum bolometer receiver on the James Clerk Maxwell telescope has been used to map the dense core of the star formation region W3 with a spatial resolution of 15-20 arcsec. At 350 and 800 μm, the region appears as two principal peaks around the known IR sources IRS4 and IRS5, while at 1100 μm, a further peak is noted which is interpreted as being due to free-free emission around IRS2. Taking into account the free-free contribution to the intensity, the continuum dust emission from the region is found to be consistent with optically thin emission at all of the three wavelengths considered. Values for the dust optical depth, hydrogen column density, mass, and central density have been obtained for each of the main peaks
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