34 research outputs found
RF Conductivity and Surface Impedance of a Superconductor Taking into Account the Complex Superconducting gap Energy
AbstractThe Mattis-Bardeen theory for the anomalous skin effect in the superconductors has been extended taking the complex gap energy into account and the surface impedance of superconductors has been calculated using the extended Mattis-Bardeen theory. It is found that the surface resistance of the superconductor increases with increasing magnitude of the imaginary part of the gap energy. It is demonstrated that the calculated surface resistance for a NbN film quantitatively agrees with the measured one. Itis also found that temperature dependence of Q values of super conducting resonators is well describedby those calculated by the extended Mattis-Bardeen equation
N2H+ Observations of Molecular Cloud Cores in Taurus
N2H+ observations of molecular cloud cores in Taurus with the Nobeyama 45 m
radio telescope are reported. We compare ``cores with young stars'' with
``cores without young stars''. The differences in core radius, linewidth, and
core mass are small. Linewidth is dominated by thermal motions in both cases.
N2H+ maps show that the intensity distribution does not differ much between
cores without stars and those with stars. This is in contrast to the result
previously obtained in H13CO+ toward Taurus molecular cloud cores. Larger
degree of depletion of H13CO+ in starless cores will be one possible
explanation for this difference. We studied the physical state of molecular
cloud cores in terms of ``critical pressure'' for the surface (external)
pressure. There is no systematic difference between starless cores and cores
with stars in this analysis. Both are not far from the critical state for
pressure equilibrium. We suggest that molecular cloud cores in which thermal
support is dominated evolve toward star formation by keeping close to the
critical state. This result is in contrast with that obtained in the
intermediate-mass star forming region OMC-2/3, where molecular cloud cores
evolve by decreasing the critical pressure appreciably. We investigate the
radial distribution of the integrated intensity. Cores with stars are found to
have shallow (-1.8 to -1.6) power-law density profiles.Comment: 19 pages, 5 figure
Discovery of X rays from Class 0 protostar candidates in OMC-3
We have observed the Orion Molecular Clouds 2 and 3 (OMC-2 and OMC-3) with
the Chandra X-ray Observatory (CXO). The northern part of OMC-3 is found to be
particularly rich in new X-ray features; four hard X-ray sources are located in
and along the filament of cloud cores. Two sources coincide positionally with
the sub- dust condensations of MMS 2 and 3 or an outflow radio source
VLA 1, which are in a very early phase of star formation. The X-ray spectra of
these sources show an absorption column of (1-3) x 10^23 H cm-2. Assuming a
moderate temperature plasma, the X-ray luminosity in the 0.5-10 keV band is
estimated to be ~10^30 erg s^-1 at a distance of 450 pc. From the large
absorption, positional coincidence and moderate luminosity, we infer that the
hard X-rays are coming from very young stellar objects embedded in the
molecular cloud cores. We found another hard X-ray source near the edge of the
dust filament. The extremely high absorption of 3 x 10^23 H cm^-2 indicates
that the source must be surrounded by dense gas, suggesting that it is either a
YSO in an early accretion phase or a Type II AGN (e.g. a Seyfert 2), although
no counterpart is found at any other wavelength. In contrast to the hard X-ray
sources, soft X-ray sources are found spread around the dust filaments, most of
which are identified with IR sources in the T Tauri phase.Comment: 9 pages, To be appeared in ApJ v554 n2 Jun 20, 2001 issue, related
press release is available at http://science.psu.edu/alert/Tsuboi11-2000.htm,
Figure 1 and figure 2 with the best resolution is available at
ftp.astro.psu.edu/pub/tsuboi/OMC/010205
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