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

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)

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)

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

Mao, Henkel, Mauersberger et al. 2000 A&A

Introduction:M82 as an example

Weiss et al. 2005 A&A

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

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

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

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

HHT CO(3-2) spectra of

nearby galaxies.

ResultsI. The spectra

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

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

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

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

Discussion-CO SED of M82

Shift to cosmological distance: M82(total) (U)LIRGs & @high z

Weiss et al. 2005 A&A3x3 kpc

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)

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)

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)

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?

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)

CO(3-2) in LIRGsIII. The spectra

12 LIRGs/18 positions observed, all detected in CO(3-2)

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)

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

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

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)

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

@ 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

““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