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CO(J=3-2) observations toward the dust lane in Centaurus A

"The Many Faces of Centaurus A " 28th June ­ 4th July 2009 Sydney, Australia Takeshi Okuda (Nagoya University ), Kotaro Kohno (University of Tokyo), Satoru Iguchi (NAOJ)


Tables of Contents



Introduction
ADIoS Project




Motivation ASTE Observation Highlight Results
CO(3-2) maps



Discussion & Summary


ASTE Dense gas Imaging of Star-forming galaxies

ADIoS Project
Goals of the project: (1) SFE variation Wide area CO(3-2) imaging survey of nearby galaxies CO(1-0) data from 45m+BEARS, Mopra, etc + Ha, radio/Mir continuum etc understand spatial variation of star formation efficiency in terms of "dense gas fraction CO(J=3-2/1-0)" Goals of the project: (2) ISM phase variation CI(490 & 800 GHz RX in ASTE, in progress) CII(from AKARI etc.) understand global "phase" variation of ISM, from atomic gas to dense gas (and eventually ionized gas) Templates for redshifted CO(3-2) & CI observations of high-z galaxies in the ALMA era


ADIoS image gallery
Kohno et al. 2008, PASJ, 60, 457 Tosaki et al. 2007, PASJ, 59, 33 M31 NGC986

NGC604 (M33) Muraoka et al.,2007, NG J, 59, PASC253 43

NGC253 Nakanishi et al, in prep. Tosaki et al. 2007, ApJ, 664, L27


Science goals:
CO(J=3-2) mapping toward Centaurs A


To Reveal a relation between star formation and dense gas in Cen A




Molecular gas distribution Physical property of dense molecular gas Gas temperature & number density Kinematics property Star formation in the dust lane SFR/SFE in the dust lane "Schmidt law" in CO(3-2)

linear correlation ! (Similar to HCN)
M83: Muraoka 2007 (PhD thesis)


Early study: CO in CenA


Single-dish (SEST/CSO/JCMT) Phillips et al. (1987), Eckart et al. (1990), Israel et al (1990, 1991), Quillen et al (1992), Israel (1992), Rydebeck et al. (1993), Liszt (2001), etc M(H ) = 2x108 M 2 sun (Eckart et al. 1990)


Tkin=10-30 K n(H2) ~ 104 cm
-3



(Wild et al. 1997) Interferometer (SMA) Espada et al. (2009)
CO(1-0/2-1) maps CO(3-2) profile map(100"x100") Liszt (2001) Wiklind et al. (1997)


CO(J=3-2) Observations w/ASTE
Antennas: ASTE 10m telescope Receiver: CATS345 (Tsys ~ 300 K in SSB) (IoA, Univ. of Tokyo) Spectrometer: WHSF 2048MHz mode On-the-Fly mapping: 7' x 3.5' CO cube Spatial resolution: 22 arcsec Velocity resolution: 10 km/s Sensitivity: dTmb=60 mK : rms(M(H2))/B = 1.5x106 Msu cf. Liszt 2001 dv = 3.26 km/s, dT = 55mK
n

Fig. Spitzer IRAC image (Quillen et al. 2006) White Box: Liszt 2001(100"x100") Red Box: This work


CATS345(2SB RX)+WHSF:
4096MHz(USB/LSB) x 2 = 8192MHz


IRC+10216 w/ the WHSF + CATS345 on ASTE
4GHz~3,400 km/s @ CO(3-2)

CO

H13CN SiC2 HCN HCN HCN USB
Okuda & Iguchi (2007), Iguchi & Okuda (2008), Okuda et al. (in prep.)

CS

SiS SiC2 LSB


CO(J=3-2) Observations w/ASTE
Antennas: ASTE 10m telescope Receiver: CATS345 (345GHz 2SB RX) (IoA, Univ. of Tokyo) Spectrometer: WHSF 2048MHz mode On-the-Fly mapping: 7' x 3.5' CO cube Spatial resolution: 22 arcsec Velocity resolution: 10 km/s Sensitivity: dTmb=60 mK : rms(M(H2))/B = 1.5x106 Msu cf. Liszt 2001 dv = 3.26 km/s, dT = 55mK
n

Fig. Spitzer IRAC image (Quillen et al. 2006) White Box: Liszt 2001(100"x100") Red Box: This work


CO(3-2) maps and spectra in Cen A



a


CO(3-2) maps of Cen A w/ ASTE
Contour: CO(J=3-2) Color: MIPS 24um



CO(J=3-2) emission nicely coincides with the dust lane. L'CO(3-2) = 9.8x107 [K km/s pc2] Assuming X(CO) = 1.8x1020 [cm-2/(K km s-1)] and CO(3-2)/(1-0) ratio of 0.5, M(H2) = 1.6 x 109 Msun (CO(1-0) data taken from Eckart et al 1990 )


Kinematics parameters: P-V diagram & Dynamical Mass


Kinematic parameters derived from CO(3-2) velocity field
Dynamical center RA(J2000) : 13h25m27.23s Dec(J2000): -43d01'18.2" I=77deg, PA=-56deg Vmax = 310 km/s




P-V diagram along PA=-56deg


Mdyn = 5 x 1010 Msun( r<2 kpc ) M(H2) = 1.4 x 109 Msun (r<2kpc) M(H2) / Mdyn = 0.03


CO line ratio along the dust lane
MIPS 24um
NW R(2-1/1-0)

R(3-2/1-0) CO(1-0) &(2-1) From Eckart et al. (1990)

SE

Offset=-30" Offset=+120" NW

SE



R(3-2/1-0) (offset<60") > R(3-2/1-0) (offset >90") Tdust(r<90") ~ 40K, Tdust (r>90") ~ 30K (Leeuw et al. 2002) The variation of CO(3-2)/(1-0) ratios along caused by temperature effect (?)


Comparison between Centaurus A and FR-I type RG 3C 31


Centaurus A Mdust ~ 106 M

sun

,T

dust

= 30-40 K

(Leeuw & Eckart 2002) R(2-1)/(1-0) ~ 0.85-1.1 (Wild et al. 1997) M(H2) ~ 1x109Msun, Mgas/Mdyn=0.03


3C 31 (D=70Mpc) Mdust = 107 Msun, T

dust

= 24 K

(Muller et al. 2004) R(2-1)/(1-0) ~ 1 (Lim et al. 2000) M(H2) ~ 1x109Msun, Mgas/Mdyn=0.02

Fig. (a) HST R-band image; (b) NMA/RAINBOW CO(1-0) image superposed on HST image; (c) NMA/RAINBOW CO(1-0) image. beam size = 1".6.x 1".2; (d) NMA/RAINBOW CO(1-0) mean velocity map +: nucleus (8GHz peak) (Okuda et al. 2005)

No evidence of massive star formation (Owen et al. 1990) What is a trigger of star formation RGs ? Gravitationally instability? Cloud-cloud collision as a result of mergers?


Summary


CO(J=3-2) observations of Centaurs A have been made using ASTE and newly developed spectrometer WHSF. Our image shows CO(3-2) emission closely coincides with the dust lane. It is suggested that CO(3-2)/(1-0) ratios along the dust lane are influenced by temperature of ISM.







Future CO(4-3) & CI OTF mapping w/ ASTE LVG analysis to determine physical properties



Channel map (1)


Channel map (2)


New 345 GHz RX

CATS345




2SB technologies implemented by Asayama et al. (NAOJ) IF band 4.0 ­ 8.0 GHz Side band rejection ratio >10 dB

Cartridge Inoue Hirofumi, Sakai Takeshi (Univ. of Tokyo) et al.

CATS345 installed in the RX cabin


LVG analysis in Cen A
Offse t - 30" 0" +30" +60" +90" +120" R(2-1/1-0) (45") 0.3±0.08 0.9±0.09 0.5±0.09 0.4±0.09 0.3±0.1 0.5±0.3 R(3-2/1-0) (45") 0.47±0.03 0.59±0.04 0.69±0.05 0.63±0.05 0.28±0.03 0.30±0.08 R(3-2/2-1) (45") 1.6±0.4 0.68±0.07 1.4±0.3 1.5±0.3 0.92±0.32 0.65±0.4

Wild et al. (1997)


Early study on HCN-FIR correlation in galaxies
IR luminosity [L_solar] ULIRGs ULIRGs

Sanders et al. 1991





Non-linear correlation between L_CO and L_FIR Linear and tight correlation between L_HCN and L_FIR

Solomon et al. 1992 ApJ, 387, L55


Star formation in M83: (1) Schmidt law in CO(3-2) "Schmidt law" in CO(3-2)




SFR: extinction corrected by MIPS 24 um data: L(Ha)true = L(Ha)obs + 0.031*L(24um) (Calzetti et al. 2007) Results: linear correlation ! (Similar to HCN)
Wu et al. 2005, ApJ, 635, L173
ic act gal tra ding s) Ex u SO incl z Q ( high

L_FIR [Lsun] or SFR

ti c lac Ga

M83 Muraoka 2007 PhD thesis

L_HCN or dense gas mass


Star formation in M83: (2) SFE vs dense gas fraction traced by CO(3-2)/CO(1-0) ratio


SFE vs "dense gas fraction" traced by CO(3-2)/CO(1-0)? roughly correlated ! Scatters caused by temperature effect?

Muraoka 2007, PhD thesis. M83 SFE map
Radiallyaveraged SFE and CO line ratios

Muraoka et al.,2007, PASJ, 59, 43