762 research outputs found
Extraction of a Pulse Wave Using a Piezoelectric Element Toward Energy Harvesting
Pulse waves are expected to be used as a power source for wearable devices. In this study, we examine whether a pulse wave can actually be extracted from a human body using commercially available piezoelectric elements. By improving the contact condition between the skin and the piezoelectric element, we confirmed that pulse waves could be extracted
Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: I. The HI Disk
We derived the three-dimensional distribution of HI gas in the Milky Way
Galaxy using the latest HI survey data cubes and rotation curves. The distance
of the HI gas was determined by the kinematic distance using a rotation curve.
We solved the near-far problem in the inner Galaxy by a fitting method which
involves introducing a model of vertical HI distribution.
In our resultant maps we could trace three prominent arms: the
Sagittarius-Carina arm, the Perseus arm, and the Outer arm. These three arms
were found to be logarithmic spiral arms. The pitch angles of the
Sagittarius-Carina, Perseus, and Outer arms were estimated to be about
11\arcdeg, 18\arcdeg, and 7\arcdeg, respectively. The Sun is located in a
region rich in HI gas between the Sagittarius-Carina arm and the Perseus arm.
The HI disk shows large and asymmetric warping in the outer disk: the HI disk
goes up to about 1.5 kpc above the Galactic plane in the northern hemisphere,
and down to about 1 kpc in the southern hemisphere, which means asymmetric
warping. The inner HI disk is also found to be tilting. The radius of the HI
disk is about 17 kpc and the HI mass within this radius is estimated to be M, which corresponds to 1.5 % of the dynamical mass
predicted from the rotation curve. We also found that the HI outskirt is
largely swelling in the fourth quadrant, and hence the Galaxy is significantly
lopsided. The scale-height of the HI layer increases with the radius, and is
correlated with the HI volume density at the centroid of the HI layer.Comment: 14 pages, 13 figure
The Schmidt Law at High Molecular Densities
We have combined Halpha and recent high resolution CO(J=1-0) data to consider
the quantitative relation between gas mass and star formation rate, or the
so-called Schmidt law in nearby spiral galaxies at regions of high molecular
density. The relation between gas quantity and star formation rate has not been
previously studied for high density regions, but using high resolution CO data
obtained at the NMA(Nobeyama Millimeter Array), we have found that the
Schmidt law is valid at densities as high as for the sample spiral galaxies, which is an order of
magnitude denser than what has been known to be the maximum density at which
the empirical law holds for non-starburst galaxies. Furthermore, we obtain a
Schmidt law index of and roughly constant star formation
efficiency over the entire disk, even within the several hundred parsecs of the
nucleus. These results imply that the physics of star formation does not change
in the central regions of spiral galaxies. Comparisons with starburst galaxies
are also given. We find a possible discontinuity in the
Schmidt law between normal and starburst galaxies
NRO M33 All Disk Survey of Giant Molecular Clouds (NRO MAGiC): I. HI to H_2 Transition
We present the results of the Nobeyama Radio Observatory (NRO) M33 All Disk
(30'x30' or 7.3 kpc x 7.3 kpc) Survey of Giant Molecular Clouds (NRO MAGiC)
based on 12CO (1-0) observations using the NRO 45-m telescope. The spatial
resolution of the resultant map is 19".3, corresponding to 81 pc, which is
sufficient to identify each Giant Molecular Cloud (GMC) in the disk. We found
clumpy structures with a typical spatial scale of ~100 pc, corresponding to
GMCs, and no diffuse, smoothly distributed component of molecular gas at this
sensitivity. Closer inspection of the CO and HI maps suggests that not every CO
emission is associated with local HI peaks, particularly in the inner portion
of the disk (r < 2 kpc), although most of CO emission is located at the local
HI peaks in the outer radii. We found that most uncovered GMCs are accompanied
by massive star-forming regions, although the star formation rates (SFRs) vary
widely from cloud to cloud. The azimuthally averaged H{\sc i} gas surface
density exhibits a flat radial distribution. However, the CO radial
distribution shows a significant enhancement within the central 1-2 kpc region,
which is very similar to that of the SFR. We obtained a map of the molecular
fraction, f_mol = Sigma_H_2/(Sigma_HI+Sigma_H_2, at a 100-pc resolution. This
is the first f_mol map covering an entire galaxy with a GMC-scale resolution.
We find that f_mol tends to be high near the center. The correlation between
f_mol and gas surface density shows two distinct sequences. The presence of two
correlation sequences can be explained by differences in metallicity, i.e.,
higher (~ 2-fold) metallicity in the central region (r< 1.5 kpc) than in the
outer parts. Alternatively, differences in scale height can also account for
the two sequences, i.e., increased scale height toward the outer disk.Comment: Accepted for publication in PASJ, See
http://www.juen.ac.jp/lab/tosaki/paper/astro-ph/2011/tosaki2011.pdf for a
version with full resolution figure
ASTE CO(3--2) Survey of Elliptical Galaxies
We report CO(3--2) observations of 15 nearby elliptical galaxies
carried out with the ASTE telescope. Thirteen were selected without regard to
the presence of other tracers of cold interstellar matter. CO emission was
detected from three of the galaxies, two of which are undetected by IRAS at 100
microns, suggesting that cold ISM may be present in more ellipticals than
previously thought. The molecular gas masses range from to
. The ratio of the CO(3--2) and (1--0) lines,
, has a lower value for elliptical galaxies than for spiral galaxies
except for NGC 855, for which the value is close to the mean for spirals. The
molecular gas in NGC 855 has a mean density in the range 300 -- 1000 cm
adopting a temperature range of 15 -- 100 K.Comment: 6 pages, 3 figures, Accepted for publication in PAS
Magnetic field vector maps of nearby spiral galaxies
We present a method for determining directions of magnetic field vectors in a
spiral galaxy using two synchrotron polarization maps, an optical image, and a
velocity field. The orientation of the transverse magnetic field is determined
with a synchrotron polarization map of higher frequency band and the
-ambiguity is solved by using sign of the Rotation Measure (RM)
after determining geometrical orientation of a disk based on a assumption of
trailing spiral arms. The advantage of this method is that direction of
magnetic vector for each line of sight through the galaxy can be inexpensively
determined with easily available data and with simple assumptions. We applied
this method to three nearby spiral galaxies using archival data obtained with
the Very Large Array (VLA) to demonstrate how it works. The three galaxies have
both clockwise and counter-clockwise magnetic fields, which implies that all
three galaxies are not classified in simple Axis-Symmetric type but types of
higher modes and that magnetic reversals commonly exist.Comment: 9 pages, 5figure
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