10,605 research outputs found
Interaction Between Supernova Remnant G22.7-0.2 And The Ambient Molecular Clouds
We have carried out 12CO (J=1-0 and 2-1), 13CO (J=1-0), and C18O (J=1-0)
observations in the direction of the supernova remnant (SNR) G22.7-0.2. A
filamentary molecular gas structure, which is likely part of a larger molecular
complex with VLSR~75-79 km/s, is detected and is found to surround the southern
boundary of the remnant. In particular, the high-velocity wing (77-110 km/s) in
the 12CO (J=1-0 and J=2-1) emission shows convincing evidence of the
interaction between SNR G22.7-0.2 and the 75-79 km/s molecular clouds (MCs).
Spectra with redshifted profiles, a signature of shocked molecular gas, are
seen in the southeastern boundary of the remnant. The association between the
remnant and the 77 km/s MCs places the remnant at the near distance of 4.0-4.8
kpc, which agrees with a location on the Scutum-Crux arm. We suggest that SNR
G22.7-0.2, SNR W41, and HII region G022.760-0.485 are at the same distance and
are associated with GMC G23.0-0.4.Comment: 9 pages, 9 figures, 3 tables, accepted for publication in Ap
Asymptotic Analysis of the Paradox in Log-Stretch Dip Moveout
There exists a paradox in dip moveout (DMO) in seismic data processing. The
paradox is why Notfors and Godfrey's approximate time log-stretched DMO can
produce better impulse responses than the full log DMO, and why Hale's f-k DMO
is correct although it was based on two inaccurate assumptions for the midpoint
repositioning and the DMO time relationship? Based on the asymptotic analysis
of the DMO algorithms, we find that any form of correctly formulated DMO must
handle both space and time coordinates properly in order to deal with all dips
accurately. The surprising improvement of Notfors and Godfrey's log DMO on Bale
and Jakubowicz's full log DMO was due to the equivalent midpoint repositioning
by transforming the time-related phase shift to the space-related phase shift.
The explanation of why Hale's f-k DMO is correct although it was based on two
inaccurate assumptions is that the two approximations exactly cancel each other
in the f-k domain to give the correct final result
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