Nobeyama CO Atlas of Nearby Spiral Glaxies

 
1. Introduction
2. Observations
3. Sample galaxies
4. Data
5. Members
6. References

1. Introduction


    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 powerful tool.
    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.

2. 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)

See Kuno et al. (2007) for more details of the observations.

3. Sample galaxies

• Sample criteria

 
• Morphological type : Sa-Scd (RC3)
• Distance : < 25Mpc
• Inclination angle : < 79deg
• IRAS 100μm flux : > 10Jy
• The morphology is not highly disturbed by interaction with other galaxies.

• Sample galaxies

NGC 253*	Maffei 2*	NGC 1068	IC 342	UGC 2855	NGC 2903
NGC 3184	NGC 3351	NGC 3504*	NGC 3521	NGC 3627	NGC 3631
NGC 4051	NGC 4102	NGC 4192	NGC 4212	NGC 4254	NGC 4303*
NGC 4321*	NGC 4402	NGC 4414	NGC 4419	NGC 4501*	NGC 4535
NGC 4536	NGC 4548	NGC 4569	NGC 4579	NGC 4654	NGC 4689
NGC 4736	NGC 5055*	NGC 5194**	NGC 5236*	NGC 5247	NGC 5248
NGC 5457	NGC 6217*	NGC 6946	NGC 6951*

        *S115Q  **S100
 

Hubble type

Sa+Sab	Sb	Sbc	Sc	Scd
5	8	14	8	5

 

bar/non-bar

SA	SAB	SB
11	24	4

 

Arm Class

Flocculent (1-4)	Multiple (5-7)	Grand-design (8-12)
8	7	19

4. Data

NGC 253	Maffei 2	NGC 1068	IC 342	UGC 2855	NGC 2903
NGC 3184	NGC 3351	NGC 3504	NGC 3521	NGC 3627	NGC 3631
NGC 4051	NGC 4102	NGC 4192	NGC 4212	NGC 4254	NGC 4303
NGC 4321	NGC 4402	NGC 4414	NGC 4419	NGC 4501	NGC 4535
NGC 4536	NGC 4548	NGC 4569	NGC 4579	NGC 4654	NGC 4689
NGC 4736	NGC 5055	NGC 5194	NGC 5236	NGC 5247	NGC 5248
NGC 5457	NGC 6217	NGC 6946	NGC 6951


 
• xxxxICO.FITS : CO integrated intensity map 
• xxxxRD.FITS : Re-gridded cube data (RA, Dec)
• xxxxXY.FITS : Cube data (observed grid: See Kuno et al. 2007)
• xxxx.dat : Newstar sp file

5. Members

• KUNO, Nario  (National Astronomical Observatory of Japan; SOKENDAI)
• CEPA, Jordi  (Instituto de Astrofisica de Canarias)
• HIROTA, Akihiko  (The University of Tokyo)
• ISHIHARA, Yuko  (Koriyama City Fureai Science Center)
• NAKAI, Naomasa  (Tsukuba University)
• NAKANISHI, Hiroyuki  (National Astronomical Observatory of Japan)
• NISHIYAMA, Kota  (Japan Spaceguard Center)
• 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)

6. References

• 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;
                     Nakai, N. & Kuno, N., 1995, PASJ 47, 761; Kuno, N. & Nakai, N., 1997, PASJ 49, 279
• 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, 2006