CO imaging surveys of nearby galaxies

Report
CO imaging surveys of
nearby galaxies
Nario Kuno
Nobeyama Radio Observatory
CO imaging survey of nearby galaxies
• Gas distribution & dynamics
<=> structures of galaxies
• Molecular gas <=> Star formation
• Physical properties of molecular gas
• Causes of difference of galaxy type
• Formation mechanism of various structures of
galaxies
• Galaxy evolution
CO imaging survey of nearby galaxies
• Molecular gas distribution and dynamics
• Molecular gas - Star formation
• Physical properties of molecular gas
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•
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Hubble type
AGN activity
Starburst activity
Environmental effects (cluster/isolated)
Galaxy interaction
Structures
– Bar properties
– Spiral arm strength
CO imaging survey of nearby galaxies
• Many sample covering various type of galaxies
• High angular resolution to resolve main
structures of galaxies
• Wide-field imaging to cover whole distribution
of molecular gas
CO survey of nearby galaxies with
interferometer
• OVRO + NMA (20 galaxies, central region)
(Sakamoto et al. 1999a, Sakamoto et al. 1999b, …)
• BIMA (44 galaxies)
– The BIMA CO Survey of Nearby Galaxies (SONG)
(Regan et al. 2001, Regan et al. 2002, …)
• PdBI (25 galaxies, central region)
– Molecular Gas in NUclei of Galaxies (NUGA)
(Garcia-Burillo, et al. 2003, Combes et al. 2004, …)
CO survey of nearby galaxies with
single dish telescope
• NRO 45-m
– Nobeyama CO Atlas of Nearby Spiral Galaxies
(Kuno et al. 2007, Nakanishi et al. 2006, …)
• IRAM 30-m
– The HERA CO Line Extragalactic Survey (HERACLES)
(Leroy et al. 2009, Bigiel et al. 2011, …)
• JCMT 15-m
– JCMT Nearby Galaxy Legacy Survey (NGLS)
(Wilson et al. 2009, Warren et al. 2010, …)
• FCRAO 14m
– Virgo spiral galaxy survey
(Chung et al. 2009)
Imaging survey with single dish
Line
Number of
sample
Number of
beam
Angular
resolution
Velocity
resolution
Sensitivity
(3sigma)
NRO45m
IRAM30m
JCMT15m
CO(1-0)
CO(2-1)
CO(3-2)
40
48
155
25
9 X dual pol.
16
15”
13”
14.5”
5km/s
2.6km/s
20km/s
0.6-1.8
Kkm/s
0.2 Kkm/s
1.9 Kkm/s
Target selection
• Complementary to other wavelength data
– HI : The HI Nearby Galaxy Survey (THINGS) (34
galaxies)
– IR : The Spitzer Infrared Nearby Galaxy Survey
(SINGS) (75 galaxies)
– UV : The GALEX Nearby Galaxy Atlas (1034 galaxies)
– Ha : many
Imaging with single dish telescope
• Importance of single dish
– Total flux measurement
– Wide field imaging
BIMA SONG
(Regan et al. 2001)
NRO CO Atlas (Kuno et al. 2007)
M33
Integrated intensity map
Tosaki et al. 2011
Velocity field
Many GMCs are resolved
[K km/s]
[km/s]
Imaging with single dish telescope
• Total flux measurement
• Wide field imaging
Large scale distribution of molecular gas
Molecular gas fraction
Star formation efficiency
Line ratio : physical properties of molecular gas
Central concentration of molecular gas
f in 
M H 2 R  RK 20 8
M H 2 R  RK 20 2
RK20
Rbar
Rcen
Concentration of molecular gas in bar region
f out 
M H 2 R  RK 20 2
M H 2 R  RK 20 
RK20
Rbar
Rcen
Comparisons with properties of galaxies
Bar strength (Laurikainen, Salo 2002) vs. fin
Molecular gas vs. star formation rate
Schruba et al. 2011
Molecular gas vs. star formation rate
HI
HI+H2
Schruba et al. 2011
H2
SFE vs. CO(3-2)/CO(1-0)
Warren et al. 2010
SFE vs. CO(3-2)/CO(1-0)
CO(1-0)
CO(3-2)
Muraoka et al. 2007
CO imaging survey of nearby galaxies
with new single dish telescope
• Increase number of sample galaxies drastically
– High performance of mapping observations
• Multi-beam + wide band spectrometer
– Multi-line
• CO(1-0), CO(2-1), CO(3-2), 13CO
• Complementary to other wavelength data
– Ha Galaxy Survey (HaGS) (James et al. 2004) (334
galaxies)
– GALEX Nearby Galaxy Survey (1034 galaxies)
– Local Volume HI Survey (120 galaxies)
– Hershel ATLAS (250,000 galaxies < z~3,4)
High demand of a large CO imaging survey
CO survey of nearby galaxies with
ALMA
• Sakamoto (2008)
– CO(2-1) Tsys=170K
– Beam size=1” Trms=0.1K (3σ~10Mo/pc2)
dV=10km/s
– D = 1-25Mpc later than S0/a
– R < 25mag arcsec-2 in B band
– 622 galaxies 2 deg2
– 1000 hours
Survey of nearby galaxies with new
single dish telescope
• New telescope
–
–
–
–
–
–
–
–
Diameter =50m
CO(2-1) Tsys=170K
Beam size = 7”
OTF 3.5” grid
main-beam efficiency 0.5
1 beam : 3’x3’ 0.1K ~50hr
Total : 2 arcdeg^2 80000 hr/N beam
Multi-beam
100 beams : 800 hr
50 beams : 1600 hr
25 beams : 3200 hr
CO survey with new multi-beam RX
FOREST on NRO 45-m telescope
• FOREST
– 2 x 2 beam x 2 pol. x 2 SB
– Mapping efficiency will be 3-4 times higher than
BEARS (much lower Tsys than BEARS)
– Wide bandwidth (USB4-12GHz) (12CO + 13CO)
– OTF technique
Science cases for nearby galaxies with FOREST
– Large CO(1-0) survey of nearby galaxies
– Mapping of nearby galaxies by denser gas tracer
than 12CO (e.g., 13CO)
13CO(1-0)
IC342
Hirota et al. 2010
12CO(1-0)
CO imaging survey of nearby galaxies
with new single dish telescope
• Increase number of sample galaxies drastically
– High performance of mapping observations
• Multi-beam + wide band spectrometer
– Multi-line
• CO(1-0), CO(2-1), CO(3-2), 13CO
• Complementary to other wavelength data
– Ha Galaxy Survey (HaGS) (James et al. 2004) (334
galaxies)
– GALEX Nearby Galaxy Survey (1034 galaxies)
– Local Volume HI Survey (120 galaxies)
– Hershel ATLAS (250,000 galaxies < z~3,4)
High demand of a large CO imaging survey

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