CO Atlas of Nearby Spiral Glaxies
- Sample galaxies
How are stars formed in galaxies?
How are molecular clouds, the place of star formation, formed? These are fundamental
questions for understanding of galaxy evolution. Since molecular gas is a
key material for these processes, observations of the molecular gas in galaxies
are essential to understand these formation mechanisms. However, it is difficult
to know the distribution and kinematics of molecular gas in galactic scale
from the observation of our Galaxy, since we are inside of the Galaxy. Therefore,
observations of external galaxies are required to get information about distribution
and kinematis of the moleculr gas in galaxies.
Some CO surveys of spiral galaxies
have been done so far and gotten excellent results. Observations performed
with interferometers reveal detail structures of molecular gas, especially
in the cetral regions of galaxies. On the other hand, although single dish
telescopes are of advantage to measure total flux, the angular resolution
was not sufficient to resolve the structure, such as spiral arms and bars.
The surveys by large single dish telescopes with high angular resolution have
been limited to strip scans. While mapping survey with a large single dish
telescope are highly desirable, the difficulty of such survey is that it
takes so much time to map an external galaxy with a single-beam receiver.
The 25-Beam Array Receiver System (BEARS) mounted on the Nobeyama 45-m telescope
is one of the most suitable instruments for such observations (Sunada et al.
SPIE 4015, 237, 2000). We can get a high performance for mapping observations
with BEARS. We made CO mapping survey of nearby spiral galaxies with this
The purposes of this project is
to investigate large scale distribution and kinematics of molecular gas in
spiral galaxies. We examine about the formation mechanism of molecular clouds
and stars by comparing with other data, such as optical, IR and HI:
- The relation between galaxy type
(Hubble type, bar/non-bar, arm class, nuclear activity, starburst phase) and
distribution of molecular gas.
- The variation of molecular gas
fraction in galaxy type and location in a galaxy (arm/interarm, bar).
- The relation between star formation
rate and neutral gas mass or molecular gas mass (Schmidt law).
- The variation of star formation
efficiency in galaxy type and location in a galaxy. The relation between
SFE and the amplitude of arms or bars.
- The relation between arm class
(in optical and near infrared) and molecular gas distribution and kinematics.
Comparison between our Galaxy and
various type of galaxies to get information about the structure of our Galaxy.
See Kuno et al. (2007) for more details
of the observations.
- Telescope : NRO 45m telescope
- Receiver : BEARS, S115Q, S100
- Spectrometer : AOS, digital spectrometer
- Position switching
- Beam size : 15"
- Noise level : 40-100mK (velocity
resolution = 5 km/s, Tmb)
3. Sample galaxies
- Sample criteria
- Morphological type : Sa-Scd (RC3)
- Distance : < 25Mpc
- Inclination angle : < 79deg
- IRAS 100¦Ìm flux : > 10Jy
- The morphology is not highly disturbed
by interaction with other galaxies.
- xxxxICO.FITS : CO integrated intensity
- xxxxRD.FITS : Re-gridded cube
data (RA, Dec)
- xxxxXY.FITS : Cube data (observed
grid: See Kuno et al. 2007)
- xxxx.dat : Newstar sp file
- KUNO, Nario (National Astronomical
Observatory of Japan; SOKENDAI)
- CEPA, Jordi (Instituto de Astrofisica
- HIROTA, Akihiko (The University
- ISHIHARA, Yuko (Koriyama City
Fureai Science Center)
- NAKAI, Naomasa (Tsukuba University)
- NAKANISHI, Hiroyuki (National
Astronomical Observatory of Japan)
- NISHIYAMA, Kota (Japan Spaceguard
- SATO, Naoko (Wakayama University)
- SHIOYA, Yasuhiro (Tohoku University)
- SORAI, Kazuo (Hokkaido University)
- TOSAKI, Tomoka (National Astronomical
Observatory of Japan)
- VILA-VILARO, Baltasar (National
Astronomical Observatory of Japan)
Nakai, N. &
Kuno, N., 1995, PASJ 47, 761; Kuno, N. & Nakai, N., 1997, PASJ 49, 279
- Kuno N. et al. 2007, PASJ 59, 117
- NGC 253 : Sorai, K. et al. 2000,
PASJ 52, 785
- NGC 3504 : Kuno, N. et al. 2000,
PASJ 52, 775
- NGC 5055 : Kuno, N. et al. 1997,
PASJ 49, 275
- NGC 5194 : Nakai, N. et al. 1994,
PASJ 46, 527; Kuno, N. et al. 1995, PASJ 47, 745;
- IC 342 : Sato, N., PhD thesis,
Hokkaido university, 2006
- Virgo cluster : Nakanishi, H.,
PhD thesis, The University of Tokyo, 2005; Nakanishi et al. ApJ 651, 804,