14 research outputs found
Aperture Synthesis CO(J=1-0) Observations and Near-Infrared Photometry of the Non-Barred Seyfert Galaxy NGC 5033
Aperture synthesis observations of CO(J=1-0) emission and near-infrared
broad-band photometry of the non-barred Seyfert galaxy NGC 5033 (D = 18.7 Mpc)
were performed. Our 3".9 x 3".6 resolution CO observations reveal a perturbed
distribution and the kinematics of molecular gas in the center of NGC 5033; we
find the characteristic gaseous features that are widely observed in barred
spiral galaxies, such as two bright CO peaks near the center (separated by ~
3'' or 270 pc from the nucleus), two offset ridges of CO emission emanating
from the CO peaks, and a CO ring (with a radius of ~ 14'' or 1.3 kpc).
Double-peaked velocity profiles are also evident near the two CO peaks,
implying that these CO peaks are orbit crowding zones in a barred/oval
potential. Although NIR data only give an upper limit of the possible bar
lengths, due to a large inclination of the NGC 5033 disk (i = 68 deg), our CO
data clearly suggests the presence of a small (the semi-major axis of about
12'' - 15'' or 1.1 - 1.4 kpc) nuclear bar (or oval structure) in the center of
the ``non-barred'' galaxy NGC 5033. Our results demonstrate that
high-resolution CO imaging-spectroscopy is useful to search for nuclear bars,
even in highly inclined systems where isophoto fitting techniques are not
applicable. We find that the gas mass-to-dynamical mass ratio, M_gas/M_dyn, is
small (< 1%) within a radius of 2'' or 180 pc, in contrast to starburst nuclei.
This implies that the starburst does not cohabitate in the type-1.5 Seyfert
nucleus of N GC 5033.Comment: 23 pages, 14 figures, accepted for publication in PASJ. For high
resolution figures see http://www.nro.nao.ac.jp/~f0151kk/n5033
The Millimeter Sky Transparency Imager (MiSTI)
The Millimeter Sky Transparency Imager (MiSTI) is a small millimeter-wave
scanning telescope with a 25-cm diameter dish operating at 183 GHz. MiSTI is
installed at Atacama, Chile, and it measures emission from atmospheric water
vapor and its fluctuations to estimate atmospheric absorption in the millimeter
to submillimeter. MiSTI observes the water vapor distribution at a spatial
resolution of 0.5 deg, and it is sensitive enough to detect an excess path
length of <~ 0.05 mm for an integration time of 1 s. By comparing the MiSTI
measurements with those by a 220 GHz tipper, we validate that the 183 GHz
measurements of MiSTI are correct, down to the level of any residual systematic
errors in the 220 GHz measurements. Since 2008, MiSTI has provided real-time
(every 1 hr) monitoring of the all-sky opacity distribution and atmospheric
transmission curves in the (sub)millimeter through the internet, allowing to
know the (sub)millimeter sky conditions at Atacama.Comment: 12 pages, 1 table, 10 figures, accepted for publication in PAS
Dense Molecular Gas Associated with the Circumnuclear Star Forming Ring in the Barred Spiral Galaxy NGC 6951
We present high resolution (3" - 5") observations of CO(1-0) and HCN(1-0)
emission from the circumnuclear star forming ring in the barred spiral galaxy
NGC 6951, a host of a type-2 Seyfert, using the Nobeyama Millimeter Array and
45 m telescope. We find that most of the HCN emission is associated with the
circumnuclear ring, where vigorous star formation occurs. The HCN to CO
integrated intensity ratio is also enhanced in the star forming ring; the peak
value of HCN/CO ratio is 0.18, which is comparable to the ratio in the
starbursts NGC 253 and M82. The formation mechanism of dense molecular gas has
been investigated. We find that the shocks along the orbit crowding do not
promote the formation of the dense molecular gas effectively but enhance the
presence of low density GMCs. Instead, gravitational instabilities of the gas
can account for the dense molecular gas formation. The HCN/CO ratio toward the
Seyfert nucleus of NGC 6951 is a rather normal value (0.086), in contrast with
other Seyferts NGC 1068 and M51 where extremely high HCN/CO value of ~ 0.5 have
been reported.Comment: 33 pages, 17 figures, to appear in the Astrophysical Journa
Starburst at the Expanding Molecular Superbubble in M82: Self-Induced Starburst at the Inner Edge of the Superbubble
We present high spatial resolution (2.3"x1.9" or 43 pc x 36 pc at D = 3.9
Mpc) 100 GHz millimeter-wave continuum emission observations with the Nobeyama
Millimeter Array toward an expanding molecular superbubble in the central
region of M82. The 100 GHz continuum image, which is dominated by free-free
emission, revealed that the four strongest peaks are concentrated at the inner
edge of the superbubble along the galactic disk. The production rates of Lyman
continuum photons calculated from 100 GHz continuum flux at these peaks are an
order of magnitude higher than those from the most massive star forming regions
in our Galaxy. At these regions, high velocity ionized gas (traced by H41a and
[Ne II]) can be seen, and H2O and OH masers are also concentrated. The center
of the superbubble, on the other hand, is weak in molecular and free-free
emissions and strong in diffuse hard X-ray emission. These observations suggest
that a strong starburst produced energetic explosions and resultant plasma and
superbubble expansions, and induced the present starburst regions traced by our
100 GHz continuum observations at the inner edge of the molecular superbubble.
These results, therefore, provide the first clear evidence of self-induced
starburst in external galaxies. Starburst at the center of the superbubble, on
the other hand, begins to cease because of a lack of molecular gas. This kind
of intense starburst seems to have occurred several times within 10^6-10^7
years in the central region of M82.Comment: 30 pages, 6 figures. To be appeared in ApJ, 617, 20 December 2004
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Interaction design challenges and solutions for ALMA operations monitoring and control
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