21-Cm Line Absorption Study of Extended Supernova Remnants
نویسندگان
چکیده
منابع مشابه
Visibility of Old Supernova Remnants in Hi 21 - cm
We estimate the number of old, radiative supernova remnants (SNRs) detectable in Hi 21-cm emission line in the Galaxy. We assume that old SNRs consist of expanding Hi shells and that they are visible if the line-of-sight velocities are sufficiently outside the velocity range of the Galactic background Hi emission. This criterion of visibility makes it possible to calculate the background contam...
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Although some 20–30,000 supernova remnants (SNRs) are expected to exist in the Milky Way, only about 230 are presently known. This implies that most SNRs are “missing”. Recently, we proposed that small ( < ∼ 1 ), faint, high-velocity features seen in large-scale 21-cm line surveys of atomic hydrogen (Hi) in the Galactic plane could be examples of such missing old SNRs. Here we report on high-re...
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Compact OH(1720 MHz) masers have proven to be excellent signposts for the interaction of supernova remnants with adjacent molecular clouds. Less appreciated has been the weak, extended OH(1720 MHz) emission which accompanies strong compact maser sources. Recent single-dish and interferometric observations reveal the majority of maser-emitting supernova remnants(SNRs) have accompanying regions o...
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Using the recently completed Giant Meterwave Radio Telescope, we have detected the HI 21 cm-line absorption from the peculiar galaxy C153 in the galaxy cluster Abell 2125. The HI absorption is at a redshift of 0.2533, with a peak optical depth of 0.36. The full width at half minimum of the absorption line is 100 km s. The estimated column density of atomic Hydrogen is 0.7×1022(Ts/100) cm . The ...
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We review the theory of measuring spectral lines in emission/absorption observations and apply it to a new survey of the 21-cm line against 79 continuum sources. We develop an observing technique and least-squares procedure to determine the opacity profile, the expected emission profile, and their uncertainty profiles. We discuss the radiative transfer for the two-component interstellar HI gas ...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1974
ISSN: 0074-1809
DOI: 10.1017/s007418090002667x