渦状銀河における GMC の進化と星形成Evolution of GMCs and star formation in spiral galaxies

Nario KunoNobeyama Radio Observatory

1. NRO M33 All-Disk Survey of Giant Molecular Clouds (NRO MAGiC)

2. Preliminary results of ALMA cycle 0 observations of M833. CO Galactic Plane Survey by NRO 45-m telescope

CollaboratorsT. Tosaki1, S.Onodera2, R. Miura3, K. Muraoka5, S. Komugi3, T. Sawada3, K. Nakanishi3, K. Kohno4, H. Kaneko6, A. Hirota7, N. Arimoto7, H. Nakanisi8, R. Kawabe3, F. Egusa9, K. Wada8

1 Joetsu University of Education2 Meisei university3 Chile observatory, NAOJ4 University of Tokyo5 Osaka Prefecture University6 Tsukuba university, 7 NAOJ 8 Kagoshima University9 ISAS

Introduction• Cycle of matter in galaxies

– Evolution of molecular clouds (from atomic gas to dense gas) are one of the main themes of radio astronomy

Observations of GMCs in nearby galaxies

– LMC: Kawamura et al. 2009, Hughes et al. 2010…– M33: Rosolowsky et al. 2007, Gratier et al. 2012…– M51: Koda et al. 2011, Egusa et al. 2011…– IC10: Leroy et al. 2006– M31: Rosolowsky et al. 2007

Scientific objectives: • Basic properties of GMCs （ mass, size, … ） • Evolution of ISM star formation process⇔

– GMC formation → dense gas → stars → destruction of GMCs

GMCs in M33 and M83

1. NRO M33 All-Disk Survey of Giant Molecular Clouds (NRO MAGiC)

Close to our Galaxy (D = 840 kpc)　 each GMC can be resolved　　 (NRO 45m resolution ：

20"~ 80 pc)

The best target for studying GMCs and star formation within a whole galaxy

Moderately face-on

GMCs are distributed throughout the disk and are in relation to other components(e.g. star-forming regions, arms,…)

(Arimoto et al.)

Many star-forming regions over the whole disk

• Data– Molecular gas : 12CO(1-0) (45m)– Warm and dense molecular gas : 12CO （ 3-2 ）（ ASTE ）

: 13CO(1-0) (45m)

– Cold dust : 1.1mm （ ASTE ：AzTEC ）

– Star-forming region : Ha （ SUBARU ）– Stars : B,V,R,I （ SUBARU ）– Atomic gas, IR … : （ Archived data ）Properties and evolution of GMCs

High resolution & wide field mapping w/ NRO 45m/ASTE 10m + OTF

• HPBW=16” @ CO(1-0)• 25 beams! + OTF

Array receivers“25BEARS”

• HPBW=22” @ CO(3-2)• Tsys~150K! + OTF

NRO 45m Atacama Submillimeter Telescope Experiment

“CATS345”

Highly uniform quality

12CO(1-0) map with NRO 45m

12CO(1-0) with 45m Velocity field

1 kpcMany GMCs are identified Globally galactic rotation

Tosaki et al. 2011

Color : 12CO(3-2) with ASTEGrey & contour : 12CO(1-0) with NRO 45m

ΔTmb ~ 13 -20 mk

5×5

7.3×3.3

4.2×4.2

5.2×5.6

2.5×3 3.3×3.3

4.4×4

2.5×2.5

Total ~ 140 arcmin2

Wide range of CO(3-2)/CO(1-0)

Miura et al. 2012

1.1 mm mapKomugi et al. 2011

1.1 Formation of molecular clouds1.2 Relation between molecular gas and star formation1.3 Evolution of Giant Molecular Clouds1.4 Radial gradient of dust temperature

1.1 Formation of molecular clouds– Molecular gas is formed more efficiently in inner region

than outer region （ Tosaki et al. 2011 ）

CO+HI CO+SFR

Correlation between gas surface density and fmol

Two distinct sequences on the Σgas – fmol

Σgas

fmol

2

2mol HHI

H

f

Molecular gas fraction; fmol

Function of 1. metallicity Z2. radiation field U3. gas pressure (or gas volume density n)(Elmegreen 1993)

high Z/high n efficient H2 formation⇒high U efficient H2 destruction⇒

Vilchez et al. 1988

• Sharp increase of metallicity in the central region from ~2kpc

• Model calculations are consistent with the observed results quantitatively

2 kpc

1.2 Relation between molecular gas and star formation

Kennicutt-Schmidt law• global correlation between

surface density of gas and star formation rate

To what scale is the Kennicutt-Schmidt law valid?

(Kennicutt et al. 2007)

M51

0.5-2kpc scale

Check by changing spatial resolution from 1kpc to 80pc

Becomes looser with higher spatial resolution

⇒The Kennicutt-Schmidt law becomes invalid in GMC scale (~80pc)

Difference of evolutionary stage of GMCs

Σ(SF

R) H

α,co

rr [M

oyr-1

pc-2]

(Onodera et al. 2010)Σ(H2)[Mo pc-2]

Resolution~80pc ~250pc

~500pc ~1kpc

2σ

• Breakdown of the Kennicutt-Schmidt law at high resolution (~ 80 pc)

(Onodera et al. 2012 PASJ in press)

SFR vs. CO(3-2) intensitySFR vs. CO(1-0) intensity

Correlation between CO(3-2) and SFR => CO(3-2) traces denser and warmer gas

1.3 Evolution of Giant Molecular Clouds– Variation of star-forming activity in molecular clouds （ Miura et al. 2012 ）

Type C:With HII regions With young stellar groups (< 10 Myr)

71 GMCs• Ha, 24um => HII regions • Stellar groupsOptical data => age of stars

CO(3-2)/CO(1-0)

CO(3-2) + young stars CO(1-0) + young stars

Ha + young stars

Classification of GMCs: 4 types of GMCs

Type A:No HII regions No young stellar groups1 %

Type B:With HII regions No young stellar groups20 %

Type C:With HII regions With young stellar groups (< 10 Myr)45 %

Type D:With HII regions With old stellar groups (10-30 Myr)34 %

Þ Life time of a GMC with a mass > 105 M => 20-40 Myr

CO(3-2)/CO(1-0) => fraction of warm and dense gas

• GMCs with high SFR have higher CO(3-2)/CO(1-0) ratio

=> higher dense and warm gas fraction (Consistent with the correltion between CO(3-2) and SFR)

• Higher mass GMCs have higher CO(3-2)/CO(1-0) ratio (for GMCs with low SFR)

=> higher dense gas fraction

Red > 5x10-9Mo yr-1 pc-2

Blue < 5x10-9Mo yr-1 pc-2

1.3 Evolution of Giant Molecular Clouds– Relation between properties of molecular clouds (evolutionary

stage, mass) and dense gas fraction （ Onodera et al. 2012 ）

Muraoka+ 2007

M33 AzTEC / ASTE

・ D= 0.84 Mpc, opt. size = 70’ x 40’

・ obsered 2007-08, 30 hours on source avg. 　 τ220GHz = 0.06

・ 30’ x 30’ x 2 field, 28” = 120pc res. most of SF disk

・ 1σ = 4-5 mJy/b = ~ 600 Modust

・ 1100 um concentrated along spiral arms, SF regions. Good spatial correlation w/ HI overdensity regions

・ can be used for : Dust physics (w/ AKARI, Spitzer, Herschel) GMC evolution, SF studies (w/ CO, HI) star cluster / galaxy evolution (w/ Subaru)

1kpc

Komugi et al. 2011

Cold dust temperature mapfrom 1.1mm and Spitzer data

Smooth gradient from G.C> to outer R

1.4 Radial gradient of dust temperature

2. Preliminary results of ALMA cycle 0 observations of M83 (PI: A. Hirota)• Mapping of M83 in

12CO(1-0)• HPBW=2.3”~50pc• GMC can be

resolved

• Best target for the comparison of GMC properties in spiral arms, bar, and central region

=> Influence on the GMC properties and their star forming activityHubble

45m+NMA200pcX100pc

ALMA Cycle 1 observations (PI: A. Hirota)

3 ． CO Galactic Plane Survey with the NRO 45-m telescope

• OTF mapping of the Galactic plane and the outer disk in 12CO(1-0), 13(1-0), C18O(1-0) (simultaneously) with FOREST

• Mapping area– l ： 10° ～ 50° 　 b ： ±1° 　（ 80 deg2)

• Spiral arms （ Perseus, Sagittarius. Scutum-Centarus arms ） , bar sturcture, molecular gas ring

– l ： 198° ～ 236° 　 b ： ±1°• Comparison between inner and outer regions (GemOB1,

MonOB1, Maddalena cloud, CMa OB1 etc)• Closer than the inner region => Noise level ~ 3 times higher

than the inner region=> Observing time : ~1/9

FOREST2X2 beam X 2 Pols X 2SB

NASA/R. Hurt

• Advantages of NRO survey– High angular resolution

Þ Can resolve clumps in the main Galactic structures (arm, bar, inner disk, outer disk)

– Multi-line observation (simultaneously)Þ Structure of molecular clouds : Diffuse molecular gas – dense gas

– Collaboration with VERAÞ measurements of the distance with VERA

GRSNRO survey

Nakanishi et al. 2006

Members• Kagoshima univ.

Handa, T., Nakanishi, H., Omodaka, T., Tanaka, A.（ M2 ） , Matsuo, T. （ M2 ） , Kamezaki(D1), Yoshida(M1),

• Osaka prefecture univ.Onishi, T., Nishimura (D2), Tokuda (M2)

• Joetsu education univ.Tosaki, T., Odaka(M1)

• Meisei univ.Onodera, S., Sofue, Y., Tsuda, Y.（ M2 ） , Ozawa, T. （ M2 ）

• ISASTsuboi, M.

• NROKuno, N., Umemoto, T., Hirota, A. （ PD ） , Matsui K. (PD)

• Chili observatoryHiguchi, A. （ PD ）

• Mizusawa VLBI observatoryHonma, M. et al. 　

• JCMT: CO(3-2)• Mini-TAO: Paα

Summary• M33

– Molecular gas is formed more efficiently in the inner region than outer region

– The Kennicutt-Schmidt law becomes invalid in GMC scale (~80pc) for CO(1-0), but it is still valid for CO(3-2)

– Life time of GMCs is estimated to be 20-40 Myr– Correlations between

• star forming activity and CO(3-2)/CO(1-0) ratio of GMCs• GMC mass and CO(3-2)/CO(1-0) ratio

– The cold dust temperature gradually decreases with radius• M83

– Excellent data of the ALMA cycle 0– Larger area will be mapped by ALMA cycle 1 observations

• CO Galactic Plane Survey with the NRO 45-m– GMC evolution and dense clump formation