-
[show abstract]
[hide abstract]
ABSTRACT: The imaging spectroscopic observations of the Magellanic irregular galaxy NGC 4449 were made to show the detailed kinematic structure of the galaxy. Many filamentary structures and Several bubble-like structures are recognized in a 3D data cube of Hff emission line. Velocity field shows the kpc-scale mosaic structure and counterrotation of ionized gas. Key Words : irregular galaxies, internal motion I. INTRODUCTION NGC 4449 is a nearby (at distance of 5.4 Mpc) Magellanic irregular galaxy which has many H II regions and a huge H I envelope. The galaxy shows violent star formation activities, and it has been the target of numerous observations. We performed imaging spectroscopic observations of the galaxy. We obtained tridimensional data cube of Hff emission line to show detailed kinematic structure and then to investigate the star formation mechanism of NGC 4449. II. OBSERVATIONS The imaging spectroscopic observations were made on 1992 April 25--28 with the 188-cm reflector equipped...
04/1997;
-
[show abstract]
[hide abstract]
ABSTRACT: We obtained an H-alpha velocity field for the entire optical region of
NGC 1569, a very actively star-forming dwarf irregular galaxy. The
H-alpha velocities have two components with separations of several tens
to one hundred km/s at about one-fourth of the observed positions, and
show bumpy features over the entire region. We suggest that these
features are due to expanding bubbles. Kinematically, the peculiar
'H-alpha arm' feature is also part of a large-scale expanding bubble. We
discuss some possible triggering mechanisms for the current star
formation in NGC 1569.
Publications- Astronomical Society of Japan 07/1994; 46:335-341. · 2.44 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have systematically searched for IRAS galaxies with 60-m flux density
larger than 0.6 Jy by means of the UK Schmidt Atlases in the Milky Way
region between l = 230 deg and 350 deg. We find that 869 IRAS point
sources are associated with galaxy images, about half of them being
known galaxies and the other half newly identified galaxy candidates.
There is some evidence that our sample is little contaminated by
Galactic objects. Enhancements of the projected density of IRAS galaxies
appear, even in the Milky Way region, along the extensions of three
large angular scale filamentary structures visible in the distribution
of galaxies in the ESO catalogue. In the enhanced density region at
Puppis, around l = 240 deg, the density of IRAS galaxies is higher at
absolute value of b less than 5 deg than at b between -15 deg and -5 deg
and b between 5 deg and 15 deg.
Monthly Notices of the Royal Astronomical Society 04/1993; 262:79-84. · 4.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The correlation between the CO-to-H2 conversion factor and the physical
properties of galaxies is investigated by examining results of CO
observations of five nearby dwarf irregular galaxies, made with a beam
size of 15 arcsec, which is comparable to the size of a giant molecular
cloud in the galaxies. The relation between the CO luminosities and the
line widths of molecular clouds was examined in 12 galaxies, including
previous observations. It was found that the CO luminosity for the same
line width decreases with decreasing metallicity (O/H) of a galaxy and
that the CO-to-H2 conversion factor increases as the metallicity of a
galaxy decreases.
Publications- Astronomical Society of Japan 03/1993; 45:L21-L26. · 2.44 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Slit spectral observations of the irregular galaxy IC 10 were made for
the H alpha emission line in the central 4.2 x 1.0 arcmin region
covering most of the star-forming regions of the galaxy; the H-alpha
velocities were obtained at about 500 points with a spatial resolution
of about 3 arcsec. The H-alpha velocities are similar to the velocities
of CO molecules, while on most of the observed H II regions the H-alpha
velocities are redshifted by 5-10 km/s or so relative to the velocities
of the surrounding H I gas. It is suggested from a simple hydrodynamical
consideration that the star-forming clouds originated due to the
collision of high-velocity infalling gas with the central H I disk.
Publications- Astronomical Society of Japan 11/1992; 44:593-600. · 2.44 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We carried out aperture synthesis observations of the dwarf irregular
galaxy IC 10 with the Nobeyama Millimeter Array in the (C-12)O (J = 1-0)
line. The observations have revealed the presence of three molecular
clouds in the most active star-forming region; the line widths, masses,
and deconvolved sizes of the molecular clouds are about 7 km/s, about 10
exp 5 solar masses, and 30-40 pc, respectively. The sizes and line
widths of the molecular clouds are consistent with the size line width
relation for giant molecular clouds in our Galaxy. The H II regions and
other features showing star-formation activity are adjacent to these
molecular clouds. All of these properties of the molecular clouds are
very similar to those of the giant molecular clouds in our Galaxy, M31,
and M33, indicating that giant molecular clouds are formed in the dwarf
irregular galaxy without any density wave. The results of CO and optical
observations suggest that the molecular clouds are receding from the
galactic plane of IC 10 with velocities of a few km/s.
Publications- Astronomical Society of Japan 11/1992; 44:585-592. · 2.44 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: (C-12)O (J = 1-0) observations of a Magellanic irregular galaxy, NGC
4449, were made, using the 45-m telescope of the Nobeyama Radio
Observatory. CO emissions were detected within two regions of the
central region of the galaxy. The molecular clouds in these regions form
molecular cloud complexes with masses of the order of 10 to the 7th
solar masses and sizes of several hundred pc. These sizes are comparable
to those of bright H II regions in the galaxy, indicating that they are
a characteristic scale of star-forming regions in this irregular galaxy.
The molecular cloud complexes are compared with molecular clouds in the
LMC and IC 10, the metallicities of which are similar to that of NGC
4449. The molecular cloud complexes in NGC 4449 fall around a regression
line of CO luminosity vs width for the molecular clouds in the LMC and
IC 10.
Publications- Astronomical Society of Japan 05/1990; 42:361-369. · 2.44 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Velocity field in the central region of M82 has drawn in detail mainly from H. This velocity field is consistent with that of Neii 12.8 m except for the region near a huge dust lane, and it cannot be explained by pure rotation around the galactic center. Origin of peculiarities of the velocity field is briefly discussed.
Astrophysics and Space Science 12/1985; 119(1):181-184. · 1.69 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: (C-12)O (J = 1-0) observations of the dwarf irregular galaxy, IC 10, are
presented. In star forming regions of IC 10, the CO clouds are
associated with a dark lane, a maser source, IRAS point sources, and
radio continuum peaks. Most of the CO clouds are located at the edge of
the optical galaxy. The emission parameters, positional correlations
with the optical galaxy, H I peaks, and star forming features of the CO
clouds in IC 10 are similar to those in the LMC. The results suggest
that there is a threshold of H I column density, below which molecular
clouds are not observed.
Publications- Astronomical Society of Japan 40:653-664. · 2.44 Impact Factor
