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Large-scale mapping observations of the CI(3P1-3P0) and CO(J=3-2) lines toward the Orion A molecular cloud
Large scale mapping observations of the 3P1-3P0 fine structure transition of
atomic carbon (CI, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the
Orion A molecular cloud have been carried out with the Mt. Fuji
submillimeter-wave telescope. The observations cover 9 square degrees, and
include the Orion nebula M42 and the L1641 dark cloud complex. The CI emission
extends over almost the entire region of the Orion A cloud and is surprisingly
similar to that of 13CO(J=1-0).The CO(J=3-2) emission shows a more featureless
and extended distribution than CI.The CI/CO(J=3-2) integrated intensity ratio
shows a spatial gradient running from the north (0.10) to the south (1.2) of
the Orion A cloud, which we interpret as a consequence of the temperature
gradient. On the other hand, the CI/13CO(J=1-0) intensity ratio shows no
systematic gradient. We have found a good correlation between the CI and
13CO(J=1-0) intensities over the Orion A cloud. This result is discussed on the
basis of photodissociation region models.Comment: Text file is 13 pages long, and 3 figure files (pdf format). NRO
Report No. 508 (1999). University of Tokyo, Resceu 41/9
Spatial and Temporal Characteristics of Snow Cover in the Tizinafu Watershed of the Western Kunlun Mountains
The Tizinafu watershed has a complex mountainous terrain in the western Kunlun Mountains; little study has been done on the spatial and temporal characteristics of snow cover in the region. Daily snow cover data of 10 hydrological years (October 2002 to September 2012) in the watershed were generated by combining MODIS Terra (MOD10A1) and Aqua (MYD10A1) snow cover products and employing a nine-day temporal filter for cloud reduction. The accuracy and window size of the temporal filter were assessed using a simulation approach. Spatial and temporal characteristics of snow cover in the watershed were then analyzed. Our results showed that snow generally starts melting in March and reaches the minimum in early August in the watershed. Snow cover percentages (SCPs) in all five elevation zones increase consistently with the rise of elevation. Slope doesn’t play a major role in snow cover distribution when it exceeds 10°. The largest SCP difference is between the south and the other aspects and occurs between mid-October and mid-November with decreasing SCP, indicating direct solar radiation may cause the reduction of snow cover. While both the mean snow cover durations (SCDs) of the hydrological years and of the snowmelt seasons share a similar spatial pattern to the topography of the watershed, the coefficient of variation of the SCDs exhibits an opposite spatial distribution. There is a significant correlation between annual mean SCP and annual total stream flow, indicating that snowmelt is a major source of stream runoff that might be predictable with SCP
Large scale IRAM 30m CO-observations in the giant molecular cloud complex W43
We aim to give a full description of the distribution and location of dense
molecular clouds in the giant molecular cloud complex W43. It has previously
been identified as one of the most massive star-forming regions in our Galaxy.
To trace the moderately dense molecular clouds in the W43 region, we initiated
an IRAM 30m large program, named W43-HERO, covering a large dynamic range of
scales (from 0.3 to 140 pc). We obtained on-the-fly-maps in 13CO (2-1) and C18O
(2-1) with a high spectral resolution of 0.1 km/s and a spatial resolution of
12". These maps cover an area of ~1.5 square degrees and include the two main
clouds of W43, as well as the lower density gas surrounding them. A comparison
with Galactic models and previous distance calculations confirms the location
of W43 near the tangential point of the Scutum arm at a distance from the Sun
of approximately 6 kpc. The resulting intensity cubes of the observed region
are separated into sub-cubes, centered on single clouds which are then analyzed
in detail. The optical depth, excitation temperature, and H2 column density
maps are derived out of the 13CO and C18O data. These results are then compared
with those derived from Herschel dust maps. The mass of a typical cloud is
several 10^4 solar masses while the total mass in the dense molecular gas (>100
cm^-3) in W43 is found to be about 1.9e6 solar masses. Probability distribution
functions obtained from column density maps derived from molecular line data
and Herschel imaging show a log-normal distribution for low column densities
and a power-law tail for high densities. A flatter slope for the molecular line
data PDF may imply that those selectively show the gravitationally collapsing
gas
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