AKARI
infrared observations of interstellar dustin nearby starburst galaxies「あかり」による近傍スターバースト銀河のダストの赤外線観測

M.Yamagishi (Nagoya Univ.)
H.Kaneda, D.Ishihara (Nagoya Univ.),
T.Onaka, I.Sakon (Tokyo Univ.), T.Suzuki (NAOJ)

Kaneda et al. 2009 , Yamagishi et al. in prep

Contents


Introduction of Starburst galaxies- NGC 253 & NGC 3079

Observation of NGC 253
 Observation of NGC 3079
Compare NGC 253 with NGC 3079

NGC253 & NCG3079
NGC253
Type,DistanceNGC3079

Edge-on, SAB(s)c, Edge-on, Sbc,
3.5Mpc
15Mpc

Classification StarburstSeyfert2(Starburst)

Dust outflow??
Galactic superwind
Interesting
phenomenon (Radovich et al.2001) (Cecil et al.2001 etc)

NGC253 & NCG3079
NGC253
Type,Distance

NGC3079

Edge-on, SAB(s)c, Edge-on, Sbc,
3.5Mpc
15Mpc

Classification Starburst

Seyfert2(Starburst)

Dust outflow??
Galactic superwind
Interesting
phenomenon (Radovich et al.2001) (Cecil et al.2001 etc)

NGC253 & NCG3079

Type,
Distance

NGC253

NGC3079

Edge-on,SAB(s)c,3.5Mpc

Edge-on,Sbc,
15Mpc

Radovichet al. 2001
IRAS 100um Seyfert2
Classification
Starburst
But ! This is an effect of saturation.
(Starburst)(Melo et al.2002)
Dust outflow??
Galactic superwind
Interesting
phenomenon (Radovich et al.2001) (Cecil et al.2001 etc)

NGC253 & NCG3079

Type,
Distance

15”

NGC253

NGC3079

Edge-on,SAB(s)c,30”
3.5MpcEdge-on,Sbc,
15Mpc

Classification StarburstRed：Hα, Green：I
Seyfert2band,
Blue：X-ray (Starburst)
http://chandra.harvard.edu/photo/2003/ngc3079/
Dust
outflow??
Galactic superwind
Interesting
phenomenon (Radovich et al.2001) (Cecil et al.2001 etc)

AKARI satellite
Launched in on Feb 21,2006 (UT)
 13 photometric bands(2-180um)
 Now in phase 3 II
ＪＡＸＡ

10 IR bands for NGC3079

4 FIR bands for NGC253

Observation of NGC253
Instrument : FIS (Far-Infrared Surveyor ) 4 photometric bands (65,90,140,160um)
 Observation AOT : FIS01(CDS mode) Date : 2007 Jun 21
 We did not use narrow band images (65,160um) becauseof the ghost signals.
FIR emission
We detected FIR dust emissions in the halo of NGC 253.

(90um)(140um)4'4'

Dust mass in the halo(90um)

Emissivity power-low index beta = 1,mass density = 3g/cm^3 and dust size
0.1um are assumed.
 We adopt the grain emissivity factor
given by Hildebrand 1983.
4'R = 2 ’ ( ~ 2kpc )halo1 :Td = 20K, Md = 1.1×10^6 Msun
 halo2 :23K,9.1×10^5 Msun
Other results
90um + X-ray contour

B: optical G: HI 21cm R: X-ray

Boomsma et al. 2005

Dust emissions is correlated
HI gas also extends to the halo.
with X-ray emission.

Sputtering timescale
How long does the dust survive without sputtering?
Does the dust escape from the galactic potential?
Draine & Salpeter 1979:
1
6  a   nH t sput ~ 10   3  [ yr ] um   cm → 4-30 Myr.
(Bauer et al. 2008)
300-2000 km/s isrequired to travel up to
9kpc in this timescale.

Escape velocity :280 km/s
(Heesen et al.2009)

Temperatures of the dust
90/140um + 90um contour

4'33K
20K
31K
48K

Grayscale : X-ray
Contour : HI
Boomsma et al. 2004 + regions

Temperatures of the dust are
getting higher in the halo!

Interaction between X-ray
superwind and HI clouds ?

Observation of NGC3079
Instrument : IRC (InfraRed Camera) + FIS
 10 photometric bands(3,4,7,11,15,24,65,90,140,160 um)
 Observation AOT : IRC02,FIS01
 Date : 2007 April 30 & May 1
10 band images
3um

4um

7um

11um

90um

140um

160um

15um

24um

2’65umLog Scale
0.1~100%
for NIR,MIR
5~100% for FIR

15um

SED

TOTAL
DISK1

Flux Density [Jy]NGC 3079 SED
100

CENTERCENTER

TOTAL

DISK2

10１’

DISK1,210.1

TOTAL: FFIR ~ 100Jy
 CENTER:
7um emission is strong

10

Wavelength[um]1007,11um PAH
7um

11um

Emissions from PAH are
dominant at 7,11umbands.
 7/11um ratio varies withlocation.

7/11 um +3um contour

MIR spectrum (Spitzer IRS,Weedman et al. 2005)
１’0.6

1.0

1.4

AKARI SED

Flux [Jy]Gas/dust ratio 100 TOTAL<TOTAL>
Tdust = 31K, 1 component (β=1)
Tdust = 32,20,12K, 3 components(β=2, Klass & Walker 2002)
Mdust = 1.4×10^7 Msun
10
Mgas=6×10^9Msun(Scoville et al. 1985)
Gas to dust mass ratio ~ 500100

1001000[um]1001000[um]

TOTAL

Flux [Jy]<CENTER>Tdust = 33K (β=1)
Mdust = 5.6×10^6 Msun
Mgas = 5×10^9 Msun
(Koda et al. 2002)
Gas to dust mass ratio ~ 1000

CENTER

10

Relation with center activity
3,7,24um
3 color image

1’Puffed-up structure at galactic center→ Relation with galactic superwinds?

30”

Compare NGC253 with NGC3079
CENTER
RegionDust[Msun]

Gas[Msun]

Gas/dust
ratio

FIR
Luminosity[Msun]

NGC253

8.3×10^6

6.7×10^880

5.8×10^9NGC3079

5.6×10^65×10^91000

4.6×10^9Kaneda et al. 2009, Koda et al. 2002, Nicholas & Judith 1990, Scoville et al. 1985

R=2kpc Not so much differences in dust mass and FIR luminosity.
 Huge amounts of gas in NGC3079, resulting in unusuallyhigh gas/dust.
Summary

We observed NGC253 & 3079 with AKARI.

<NGC253>
 We detect FIR dust emissions in the halo.
 There are high-temperature regions in the halo.
<NGC3079> 7/11um ratio varies with location.
 Possible relationship between galactic superwinds andpuffed-up structure of 24um image.
 Gas to dust mass ratio is very large .
→ Early evolutionary stages of ISM? There are large
amounts of gas which is not linking to star formation.
Active star formation will occur in future?