Evolution of molecular clouds
in the superwind galaxy NGC 1808
Dragan SALAK1*, Yuto TOMIYASU2, Naomasa NAKAI2, Yusuke MIYAMOTO3,Nario KUNO2 & Hiroyuki KANEKO3
1Kwansei Gakuin University, 2Tsukuba University, 3National Astronomical Observatory of Japan*d.salak@kwansei.ac.jp

Abstract

Case'study:'starburst'galaxy'NGC'1808

ALMA observations of the cold molecular medium traced by CO (J=1-0) and (J=3-2) in the nearby starburst galaxy NGC
1808 have revealed molecular winds from the central 1 kpc starburst region, with expansion speeds of the order 100-200 km
s-1, consistent with starburst-driven winds. The CO (3-2)/(1-0) brightness ratio in the starburst region indicates an evolutionof molecular clouds
from accretion
molecular gas onto a 500 pc ring, to enhanced star formation inside the ring, andMorphology' of'(R)SAB(s)a'(de'Vaucouleurs'et'al.'1991)'
outflows as feedback. The clouds in the ring entrain in an outflow, and partially inflow toward the galactic center region
Distance'''10.8'Mpc'(Tully'1988)'
where they feed the nuclear starburst and entrain in a nuclear outflow. The mass outflow rate is an order of magnitude
AcSvity' rate' assuming'Starburst'+'maybe'Seyfert'2'(Veron[Cedy'&'Veron'1985)'
smaller than the starformation
optically thin CO (1-0) emission in the outflow; star formation in NGC 1808 at
this stage is not significantly suppressed by the wind. (References: Salak et al. 2016, ApJ, 823, 68; Salak et al. 2017, ApJ,89, 90)(a)(b)
ALMA observations
Band
3: CO (1-0) @ 2”
Starburst'
Cycle&1&science'Band
7: CO (3-2) @ 1”
nucleus
12m + Atacama Compact ArrayEvoluSon'of'molecular'(ACA) + total power Bar''
clouds'in'starburst'

far side

Hα'(6563'Å)

Eskridge'et'al.'(2002)

Mutchler'et'al.'HST

Position-velocity
diagrams(PVDs) parallel to the galactic
minor axis reveal moleculargas
outflows
fromthecircumnuclear disk (CND)
and 500 pc ring. The outflow
velocities are ~75 km/s in thering and ~180 km/s in theCND. The mass outflow rateis ~0.1 of the SFR (foroptically
thinCO1-0emission),suggesting
inefficient suppression of starformation.
30:30.0outflow

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

30:30.0500 pcpseudoring

CMCsCND
nuclearspiralbar (ridge)

Outflow from the 500 pc starburst ringCO (1-0)

PVD-NW

PVD-SE

shell
PVD-NW

shell

PVD-SE

Offset [arcsec]

Clump flux
[Jy km/s]
Clumpflux [Jy km/s]

CO (3-2) velocity
CO (3-2)field
velocity field

Evolution of molecular clouds
35.0

bar (ridge)

Intensity [Jy beam-1]

Intensity ratio

PVD

outflow

Integrated intensity [Jy beam-1 km s-1]

CO (1-0)

0.9 mmIntegrated intensity [Jy beam-1 km s-1]

Intensity [Jy beam-1]

Intensity [Jy beam-1]

outflow

Credit: ALMA

Molecular gas outflows

CO (3-2)

CO (1-0)(d)(c)

B[band'(4360'Å)

Nuclear (CND) outflow
Vsys(HII'regions) feeding'and'feedback

imaged region
near side

Velocity LSR [km s-1]

Dust'ouelow'(feedback)

CO (3-2)

Integrated intensity [Jy beam-1 km s-1]

R-band (HST)Intensity [Jy beam-1]

Basic data
Morphology:(R)SAB(s)aDistance:
10.8 Mpc
Linear scale:1” = 52 pc
Inclination:i = 57°
Activity:
Starburst/Sy2Results

500 pcObservations

CO (3-2)/CO(1-0) intensity ratio>150CO (3-2)/CO (1-0) intensity ratio>15035.02504030
2011000<5050-100

100-150<50>150

100-150>150

Integrated flux [Jy km/s]

Integrated flux [Jy km/s]

12100

1190

1080

9

Number of clumps

Number of clumps

50-1008765437060
50
4030
202

10100

<1010-20

20-30

Integrated flux [Jy km/s]>30<1010-20

20-30

Integrated flux [Jy km/s]>3005.030:30.0

Clump flux [Jy km/s]
Clump flux [Jy km/s]>150>150

30:30.0

35.0

35.0

100-150

45.0
05.0

55.0
45.0

40.0
45.0
50.0
55.0

-37:31:00.0

100-15040.0

50-10050-100

45.0

25-50

25-50

50.0

<2555.0500 pc ring360500 pc ring

4Declination J2000

570

Declination J2000

80

6on J2000
Declination J2000

90

7ion J2000
Declination J2000

1008

DeclinationDeclination
J2000
J2000
J2000
DeclinationDeclination
J2000
tion J2000

110

9DeclinationDeclination
J2000
J2000
J2000
DeclinationDeclination
J2000
ation J2000

10

Number of clumps

Number of clumps

CLUMPFIND algorithm (Williams et al. 1994) was applied to theClumpflux[Jy 100-150km/s]
100-150
Clump
flux [Jy km/s]
30:30.0 30:30.0
40.0 in 40.0
high-resolution CO (3-2) data cube to identify clouds
the starburst
>150
>150
region. The CO luminosity function is plotted below.
TheCO(3-2)
50-100 50-100
35.0
35.0
45.0
45.0
flux was converted to CO (1-0) using the line intensity ratio map.
100-150 100-150
Clump
flux
[Jy km/s]
500 pc ring
Outer region
CMCCenterClump
flux [Jy km/s]
Thecloud40.0 luminosity
40.0
25-50
30:30.0
(a)
(b)
25-50
50.0 30:30.0
50.0
CO (3-2)
CO (3-2)>150
function is different in>150
50-100 50-100
35.0center
45.0
the 45.0(CND;
35.055.0<2555.0<25
primary
barprimary bar
Clump
flux
[Jy 100-150km/s]
R<3”),CMC (3”<R<6”),100-150
Clump
flux [Jykm/s]
inflow
25-50
30:30.0
CO (3-2)
CLUMPFIND
inflowbar
25-50
30:30.0
50.0
bar
40.0
50.0
Clump
flux
[Jykm/s]
40.0-37:31:00.0
Clump
flux
[Jykm/s]
500 pcring (6”<R<15”)
result-37:31:00.0>150
30:30.0 30:30.0
integrated>150 rotational rotational
cloud growth
cloud growthhalf-period>150 half-period
flux
50-100 crowding
crowdingand 55.0
region50-10035.0 outer
6 years >150
35.0
8x10
6 years<2545.08x10
55.0<2545.0
05.0[Jy km/s]
05.0
35.0(R>15”).
star100-150
formation
35.0
star100-150
formation
CMCCenter
500 pc ring
Outer region(c)(d)
Clump25-50
flux[Jy km/s]
CND
Clumpflux [Jykm/s]
40.0
CND
CND
100-150
Theclouds
40.0evolve as
30:30.0
CND
25-50
CO (1-0)
CO (1-0) -37:31:00.0100-150
50.0
30:30.0-37:31:00.0
Clump flux
[Jykm/s]
50.0
Clump flux [Jy km/s]
44.0 30:30.0
42.5
42.0
41.5
41.0
feedback
40.0 5:07:43.0
44.0
43.5
42.5
42.0
41.5
41.0stellar>150
stellar>150
feedback
40.0 5:07:43.0
they enter
the43.550030:30.0
pc
50-100 50-100>150
Right ascension
J2000 J2000
>150
45.0
Rightascension
45.0
35.0
05.0
50-100
55.0
35.0
<25
ring from 05.0
the 45.0
primary
50-10055.0<2535.045.0
35.0
100-150
bar, 50.0
fuel star formation,
25-50 100-150
25-50204060
80
100
120
20
40
60
80
100
120 100-150
50.0
outflow
100-15040.0
baroutflow-37:31:00.0
40.0
bar
44.0 in 43.5
5:07:43.0
42.5
42.0
41.5
41.0
-37:31:00.0
25-50
44.0
43.5
5:07:43.0
42.5
42.0
41.5
41.0
and entrain
outflows
25-50
nuclearoutflowfrom ring from ring
50.0
40.0
nuclearoutflow
50.0
40.0
Rightascension
J2000
50-100 50-100
Right ascension J2000(see55.0
illustration).
<2555.0<2545.0<25-37:31:00.0

05.0

05.0

44.0

43.5 5:07:43.0 42.5
42.0
41.544.0
43.5 5:07:43.0 42.5

41.0
42.0

41.5

41.0

Right ascensionRightJ2000
ascension J2000
2040
2060

4080

55.0 26-27, 2017 @ NAOJ, Tokyo
45.0
ALMA/45m/ASTE Users Meeting 2017, December
20
40
60
80

60

100

12080

100

100

120

120

50-100<2550-100<25