A CO(3-2) Survey of Warm Molecular Gas in Nearby Galaxies
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A CO(3-2) Survey of Warm Molecular Gas in Nearby
Galaxies
Rui-Qing Mao (毛瑞青 )(Purple Mountain Observatory, Nanjing)
C. Henkel (MPIfR) R. Mauersberger (IRAM) Dinh-Van-Trung (ASIAA)
“Universe Probed by Radio” Sino-German Workshop on Radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005
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Introduction:CO as a tracer of H2 in galaxies
Lower lying CO rotational line transitions are often used as tracers of H2.
CO(1-0), (2-1) surveys in galaxies Young et al. (1995) 300 galaxies @ FCRAO Braine & Combes (1992) 81 spirals @ IRAM-30m …
CO is a good tracer of density waves, spirals, bars, rings.
High spatial resolution CO(1-0) surveys in galaxies BIMA-SONG (Regan et al. 2001; Helfer et al. 2003) NUGA (S. García-Burillo F. Combes et al ) NMA (Sakamoto et al. 1999)
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Introduction: Is CO a Good Tracer of SF in galaxies?
LHCN ~ LIR tight linear correlation Star formation driven LIR
CO(1-0): poor tracer?
Gao & Solomon (2004 ApJL)
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Introduction:How about sub-mm CO lines?
Better tracers for the warmer/denser molecular gas
R31 = ICO(3-2)/ICO(1-0) is more sensitive to the excitation of molecular gas than R21 = ICO(2-1)/ICO(1-0)
R31 is expected to be peaked in regions of active SF High J CO lines will put more constraints to the
excitation of molecular gas
Ju 1 2 3 4 5 6 7Eu(K) 5.5 17 33 55 83 116 155nc(cm-
3)7.4•10
24.9•1
031.5•1
04… … … ~106
LVG model of R31
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Mao, Henkel, Mauersberger et al. 2000 A&A
Introduction:M82 as an example
Weiss et al. 2005 A&A
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Introduction:CO SED
M82 CO(7-6): first time the weakening in CO SED
The CO SED turnover can serve as an indicator of gas excitation
M82, NGC 253: 6-5 Henize 2-10, BR1202-0725(z=4.7), Cloverleaf (z=2.6): >7-6 SMM J16359+6612: 5-4
Weiss et al. 2005 astro-ph
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Introduction:Extragalactic CO(3-2) surveys
Devereux et al. (1994) 7 starbursts; <R31>=0.64+/-0.06
Mauersberger et al. (1999) 28 nearby galaxies + 1 ULIRG; <R31>=0.63 (0.2-0.7)
Dumke et al. (2001) Mapping Meier et al. (2001) 8 Dwarf starbursts; <R31>=0.60+/-0.06
Yao et al. (2003) 60 SLUGS cz 1900 km s-1; S60m 5.24 Jy; LFIR 1010LO
<R31>=0.66 Vila-vilaro B. et al. (2003) 10 eraly-type galaxies Hafok et al. (2003) 16 in Virgo Cluster; <R31>=0.14-0.35 Narayanan et al. (2005) 15 Starbursts + (U)LIRGs
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What’s the general properties of warm molecular gas in various galaxies?
Can CO(3-2) be a good tracer of SF? Can R31 be a good tracer of the
excitation of molecular gas? Any correlation between R31 and LIR,
Hubble type, IR colors, merging sequence?
Motivations
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Observations
The Telescope:@ D=10.5 m@ = 22" at 345 GHz@ 3100m
The Sample: 120@ Normal galaxies: 49 (S100m>50 Jy; Braine et al. 1993)
@ Seyfert & LINER: 61 (v<7000 km/s; Seyfert: 41; LINER:44; Sy+LINER:17)
@ (U)LIRGs: 10 (Solomon et al. 1997)
(Sy+LINER: 8; Sbrst: 1; UN: 1)
The Heinrich-Hertz-Telescope (HHT) @ Mt. Graham, Arizona
@Early type: 23 @Virgo cluster galaxies: 10
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HHT CO(3-2) spectra of
nearby galaxies.
ResultsI. The spectra
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Detection rate -- 85/120 (71%) Normal galaxies: 35/49 (71%) Seyfert & LINER: 42/61 (69%) (U)LIRGs: 8/10 (80%)
Early type: 11/23 (48%) Virgo cluster galaxies: 8/10 (80%)
ResultsII. Detection rates
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0 2000 4000 6000 8000 10000 12000 140000
10
20
30
Nu
mb
er
of g
ala
xie
s
Velocity (km s-1)
7 8 9 10 11 120
10
20
30
Nu
mb
er
of g
ala
xie
slog(L/L
O)
ResultsIII. The statistics
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0 50 100 150 2000
1
2
3
R3
1
D (Mpc)
8 9 10 11 12 13
0
1
2
3
N1068
Arp 193
N7679N1275
IIIZW35
N6240 Arp 220
Mrk 273
17208-0014N7469
N3077
Mrk 231
R3
1
log(L/LO)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.50
5
10
15
20
Nu
mb
er
of g
ala
xie
s
R31
= I32
/ I10
ResultsIV. The statistics – R31
Matching beam line ratios R31 (@ 22”, 51 galaxies) <R31> =0.71+/-0.05, median=0.65
(Seyfert: <R13>=0.68 [0.4:1], ULIRG: <R13>=0.77 [0.4:1.2]) No obvious correlation to LFIR, Hubble type, IR colors Caution: (U)LIRGs: global, unresolved, R31 / Nearby starbursts: centers-only
0.0 0.5 1.0 1.5 2.00
2
4
6
8
10
Nu
mb
er
of
ga
laxi
es
R31
= I32
/ I10
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Mapping needed-R31 distribution in M82Weiss et al. 2005
Mao, Henkel, Mauersberger et al. 2000
12CO(1-0)V-band
OVRO + IRAM30m
• lower R31 than in the central molecular disk• gas properties are similar to the nuclear ‘low’ excitation components
streamer/outflow regions
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Discussion-CO SED of M82
Shift to cosmological distance: M82(total) (U)LIRGs & @high z
Weiss et al. 2005 A&A3x3 kpc
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High Resolution SMA CO(3-2) in M51
Strong central concentration Weak north-west arm High line ratio: I32/I10 ~ 2
hot and dense mol. Gas High R31 in outflow and shocked
gas around SNRs in the MW gas dynamics around the
Seyfert 2 nucleus heating by the central AGN?
Common for Seyfert galaxies? Looking for more Seyfert
(Matsushita et al. 2004 ApJL)
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Results V. LCO(3-2) vs. LFIR
9 10 11 121.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
log10
LCO(3-2)
= -5.4+/-0.5 + 0.90+/-0.05 log10
LFIR
log 10
(LC
O(3
-2)/
[K k
m s
-1 M
pc2 ])
log10
(LFIR
/LO)
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Results V. LCO(3-2) vs. LFIR
9 10 11 12
2
3
4
5
6
log10
LCO(1-0)
= -4.8+/-0.6 + 0.87+/-0.06log10L
FIR
lo
g 10(
L CO
(1-0
)/ [K
km
s-1 M
pc2
b])
log10
(LFIR
/LO)
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CO(3-2) in LIRGsI. The Merging sequence
total H2 content decreases as the projected separation of merger nuclei decreases (Gao & Solomon 1999)
What about the excitation conditions of the molecular gas? Are these also affected by the interaction?
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CO(3-2) in LIRGsII. The sample The sample (16) (Lo et al. 1997;2000; Gao et al. 1997;2001)
Early Mergers UGC 2369, Arp 303, UGC 8335, Arp 240, Arp 302, Arp
293, NGC 6670 Intermediate Mergers
Arp 256, Mrk 848, Arp 55, NGC 7592 Advanced Mergers
NGC 1614, NGC 5256, NGC 6090, NGC 3110, NGC 3147
16 LIRGs/22 pointings (5 overlaps with the SLUGS sample)
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CO(3-2) in LIRGsIII. The spectra
12 LIRGs/18 positions observed, all detected in CO(3-2)
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Results V. LCO(3-2) vs. LFIR
9 10 11 121.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
log10
LCO(3-2)
= -5.4+/-0.5 + 0.90+/-0.05 log10
LFIR
log 10
(LC
O(3
-2)/
[K k
m s
-1 M
pc2 ])
log10
(LFIR
/LO)
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9 10 11 12 13
2
3
4
5
6
log10
LCO(3-2)
= -5.8+/-0.5 + 0.95+/-0.05log10L
FIR
lo
g 10(L
CO
(3-2
)/ [K
km
s-1 M
pc2 ])
log10
(LFIR
/LO)
Results V. LCO(3-2) vs. LFIR
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9 10 11 12 13
2
3
4
5
6
log10
LCO(3-2)
= -5.8+/-0.5 + 0.95+/-0.05log10L
FIR
lo
g 10(L
CO
(3-2
)/ [K
km
s-1 M
pc2 ])
log10
(LFIR
/LO)
Results V. LCO(3-2) vs. LFIR
LIRGsLIRGsULIRGsULIRGs
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9 10 11 12 13
2
3
4
5
6
log10
LCO(3-2)
= -5.8+/-0.5 + 0.95+/-0.05log10L
FIR
lo
g 10(L
CO
(3-2
)/ [K
km
s-1 M
pc2 ])
log10
(LFIR
/LO)
Results V. LCO(3-2) vs. LFIR
60 SLUGS: log10LCO(3-2) = -2.4+/-0.5 + 0.70+/- 0.04 log10LFIR (Yao et al.
2004 )
28 nearby gals: log10LCO(3-2) = -3.44 + 1.08 log10LFIR (Mauersberger et al. 1999)
0.58 for CO(1-0)
LIRGsLIRGsULIRGsULIRGs
Almost linear
14(U)LIRGs+SLUGS: log10LCO(3-2) = -3.56 + 1.09 log10LFIR (Narayanan et al. astro-ph/0504412)
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Summary Almost linear correlation of LCO(3-2)-LFIR @ 22”
With a power of 0.95 CO(3-2) can trace warm-dense star forming gas
<R31> =0.71, median=0.65 No obvious correlations are found between
R31 and Hubble type, LFIR, infrared colors at 22” resolution
Mapping is needed for the nearby galaxies to make their R31 compared to that of (U)LIRGs
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@ High resolutionNGC6946 seen with the SMA
CO(2-1) in color 2.4" x3.0" Multiple arms Gas lane along bar
CO(3-2) in contours 0.7"x1.0" ! Streaming motion Possible molecular nuclear mini-bar
The key issue is to understand the dynamics: ‘feeding the nucleus’
Mao R.-Q et al., (2005 in preparation)
D=5.5 Mpc
““Cosmos probed by radio” Sino-German workshop on radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005Cosmos probed by radio” Sino-German workshop on radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005
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““Universe Probed by Radio” Sino-German workshop on radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005Universe Probed by Radio” Sino-German workshop on radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005