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“Universe Probed by Radio” Sino-German Workshop on Radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005. 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).

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a co 3 2 survey of warm molecular gas in nearby galaxies

“Universe Probed by Radio” Sino-German Workshop on Radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005

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)

introduction co as a tracer of h 2 in galaxies
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
Introduction: Is CO a Good Tracer ofSF in galaxies?

Gao & Solomon (2004 ApJL)

LHCN ~ LIR tightlinear correlation  Star formation driven LIR

CO(1-0): poor tracer?

introduction how about sub mm co lines
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

LVG model of R31

introduction m82 as an example
Introduction:M82 as an example

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

Weiss et al. 2005 A&A

introduction co sed
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
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; S60m  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
slide8

Motivations

  • 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?
observations
Observations

The Telescope:

@ D=10.5 m

@  = 22" at 345 GHz

@ 3100m

The Sample:120

@ Normal galaxies: 49

(S100m>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

slide10

Results

I. The spectra

HHT CO(3-2) spectra of nearby galaxies.

slide11

Results

II. Detection rates

  • 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%)
slide12

Results

III. The statistics

slide13

Results

IV. 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
mapping needed r 31 distribution in m82
Mapping needed-R31 distribution in M82

Weiss et al. 2005

V-band

12CO(1-0)

OVRO + IRAM30m

Mao, Henkel, Mauersberger et al. 2000

streamer/outflow regions

  • lower R31 than in the central molecular disk
  • gas properties are similar to the nuclear ‘low’ excitation components
discussion co sed of m82
Discussion-CO SED of M82

Weiss et al. 2005 A&A

3x3 kpc

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

high resolution sma co 3 2 in m51
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)

slide17

Results

V. LCO(3-2) vs. LFIR

slide18

Results

V. LCO(3-2) vs. LFIR

co 3 2 in lirgs i the merging sequence
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 lirgs ii the sample
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 lirgs iii the spectra
CO(3-2) in LIRGsIII. The spectra

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

slide22

Results

V. LCO(3-2) vs. LFIR

slide23

Results

V. LCO(3-2) vs. LFIR

slide24

Results

V. LCO(3-2) vs. LFIR

ULIRGs

LIRGs

slide25

Results

V. LCO(3-2) vs. LFIR

Almost linear

ULIRGs

LIRGs

28 nearby gals: log10LCO(3-2) = -3.44 + 1.08 log10LFIR (Mauersberger et al. 1999)

60 SLUGS: log10LCO(3-2) = -2.4+/-0.5 + 0.70+/- 0.04 log10LFIR (Yao et al. 2004 )

14(U)LIRGs+SLUGS: log10LCO(3-2) = -3.56 + 1.09 log10LFIR (Narayanan et al. astro-ph/0504412)

0.58 for CO(1-0)

summary
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 resolution ngc6946 seen with the sma

“Cosmos probed by radio” Sino-German workshop on radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005

@ 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’

D=5.5 Mpc

Mao R.-Q et al., (2005 in preparation)

slide28

“Universe Probed by Radio” Sino-German workshop on radioastronomy, Kashi/Urumqi, Sept. 7-13, 2005