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101.
M.P. Collings J.W. Dever H.J. Fraser M.R.S. McCoustra 《Astrophysics and Space Science》2003,285(3-4):633-659
The interaction of carbon monoxide (CO) with vapour-deposited water(H2O) ices has been studied using temperature programmed desorption (TPD) and Fourier transform reflection-absorption infrared
spectroscopy (FT-RAIRS) over a range of astrophysically relevant temperatures. Such measurements have shown that CO desorption
from amorphous H2Oices is a much more complex process than current astrochemical models suggest. Re-visiting previously reported laboratory
experiments (Collings et al., 2003), a rate model has been constructed to explain, in a phenomenological manner, the desorption
of CO over astronomically relevant time scales. The model presented here can be widely applied to a range of astronomical
environments where depletion of CO from the gas phase is relevant. The model accounts for the two competing processes of CO
desorption and migration, and also enables the entrapment of some of the CO in the ice matrix and its subsequent release as
the water ice crystallises and then desorbs. The astronomical implications of this model are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
102.
With the advent of either sensitive space-born infrared cameras, or their high-resolution ground-based siblings, we are uncovering
a new category of star clusters: the dust-enshrouded super-star clusters. These manifest themselves only beyond a few microns,
as their shroud of dust is able to block all light emitted by the stars themselves. Here we present our results on the spectacular
cluster in SBS 0335-052, a very metal-poor galaxy. We also point to the growing number of galaxy analogs to SBS 0335-052,
revealing the possibility that these clusters signal a major mode of star formation in starbursts. We conclude by listing
a number of open points these clusters raise, in particular with respect to high-redshift counterparts.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
103.
104.
Interplanetary field enhancements were first discovered in the vicinity of Venus. These events are characterised by an increase in the magnitude of the heliospheric magnetic field with a near-symmetrical, sometimes thorn-shaped profile, and last from minutes to hours. Surveys of the events near Venus and Earth indicated clustering of the events in inertial space, which suggested that their sources were Solar System objects other than the Sun. A survey is presented of strong events of this type detected by the Ulysses spacecraft from 1990 to late 2001. Most of the events are accompanied by a discontinuity in the field direction near the events' centres. Other discontinuities are often symmetrical about the enhancement. The majority of events last less than two hours. When examined as a whole, the events tend to be accompanied by subtle changes in some plasma parameters. The majority of the enhancements are accompanied by magnetic holes on their fringes. The enhancements' occurrence rate increases with decreasing heliocentric distance. Possible formation mechanisms are discussed. No link was found with solar, or solar wind sources. Several aspects of the survey results are consistent with an origin related to cometary dust trails. Possible processes associated with a dust-solar wind interaction are discussed. 相似文献
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107.
Frédéric Zagury 《Monthly notices of the Royal Astronomical Society》2006,370(4):1763-1770
The hypothesis of an extended red emission (ERE) in diffuse Galactic light (DGL) has been put forward in 1998 by Gordon, Witt & Friedmann who found that scattered starlight was not enough to explain the amount of DGL in the R band, in some high Galactic latitude directions. This paper re-investigates, for high Galactic latitudes, the brightnesses and colours of DGL, integrated star and galaxy light (ISGL), and of the total extrasolar light (ISGL+DGL) measured by Pioneer. Under the traditional assumption that DGL is forward scattering of background starlight by interstellar dust on the line of sight, ISGL and Pioneer have very close colours, as it is found by Gordon, Witt & Friedmann. Pioneer observations at high |b| thus accept an alternative and simple interpretation, with no involvement of ERE in DGL. 相似文献
108.
Philippe André 《Astrophysics and Space Science》2002,281(1-2):51-66
Detailed studies of nearby cluster-forming molecular clouds can help us understand the physical processes by which most stars
form in galaxies. I review recent advances made on this subject. Submillimeter observations of nearby protoclusters suggest
that stars are generally built from finite, detached reservoirs of mass inside molecular cloud cores, and point to a cloud
fragmentation origin for the IMF. Much progress in this field will come from future large submillimeter instruments such as
Herschel and ALMA.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
109.
NathanSmith † 《Monthly notices of the Royal Astronomical Society》2002,331(1):7-12
Narrow-band infrared and optical images of the Keyhole Nebula in NGC 3372 reveal which structures are caused by extinction, and show the underlying morphology of photoionized and shock-excited gas. Dark clouds conspire with ionized gas to create the apparent keyhole shape, which is prominent at blue wavelengths and less apparent in the infrared. The Pa β /H α line ratio shows the spatial distribution of foreground extinction. The wavelength dependence of this extinction indicates a reddening law with R ≈4.8 , different from the normal interstellar medium. This confirms previous estimates of reddening toward the Carina Nebula determined from stellar photometry, and reveals that the anomalous extinction is patchy and within the H ii region. The morphology of the ionized gas is different from the extinction clouds; it shows an edge-on ionization front running NE to SW, with a limb-brightened indentation that forms the upper outline of the keyhole shape. A fast polar wind from η Carinae may have punctured the ionization front, since the indentation is directly along a projection of the polar axis of the star. This is supported by the morphology of shock-excited gas revealed by a high [S ii ]/H α ratio. High-excitation gas emitting [O iii ] and He i has a smoother distribution. Molecular clumps in the region are also discussed. 相似文献
110.