Galactic winds driven by starformation in the local Universe
Dragan SalakTomonaga Center for the History of the Universe
University of Tsukuba
21 November 2019461983B9• 2007/6• 2011/3

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Star formation and molecular gas• Star formation is observed to take place predominantly in molecular clouds.
• Molecular clouds are giant gaseous bodies (size 10-100 pc) that consist mostly of H2 gas
and dust particles (size ~0.1 μm).
• Cold (T ~ 10 K) and low density (n ~ 103 cm-3), so many molecular rotational lines(e.g., CO J=1-0) can be detected at μm~mm wavelengths by radio telescopes.

Milky Way galaxy (NASA)

TCHoU193

Formation and evolution of stars
molecular cloud

molecular cloud

molecular cloudwith young stars

high-density cores –gravitational collapse

supernovae, stellarremnants

old stars

main sequencestars (e.g., Sun)
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total Milky Way galaxy“Physics of the ISM and IGM” Draine
4Baryon cycle in galaxies
galactic wind (outflow)

molecular cloudwind

NGC1482barinflow

starburst

iskdc
it
c
alga
wind
(ionized gas: Hα)e.g., Veilleux+ (2005)
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Starburst galaxy M82
star formation rate 5-10 M⦿/yr(solar masses/year)

HST5

Molecular gas in galactic winds• Classical example: starburst galaxy M82

Large-scale molecular gas outflow was
detected by the Nobeyama 45-m telescope.
Up to 40% of total molecular gas mass in
M82 is in the outflow.

Contours: CO (J=1-0)
DS+ 2013 PASJ, 65, 66
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Starburst galaxy NGC 1808
tiorpstudelansn• Starburst in central 500 pc• Evidence for neutral gas outflow

R band negativesoab• Nearby (~11 Mpc)

emissionfarfar

pr
aloem
ar ar
nene

ion
issabsorption

B band negative (Phillips 1993)
Na I (Phillips 1993)

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Carnegie-Irvine Galaxy Survey(Ho+ 2011) 7

ALMA observations of NGC 1808
Atacama Large Millimeter/submillimeter ArrayCycle

12

Resolution2”(100 pc)

0.5”-1”(25-50 pc)

Spectral line

CO (1-0)

CO (3-2)

Optical (CGS)TCHoU19

optical(Hubble Space Telescope)8• d

29:30.0

fa

Position Y

Molecular gas distribution
id esr-37:30:00.0! [Jy]

1 kpc

30.0

beam

Optical (CGS)

oPosition X

ne

31:00.0

48.0

lVe

arsid
e

30.0

Vytci

Intensity ! = !(0, 2, &)

46.0

44.0

42.0 5:07:40.0 38.0

∫ ! -&

36.0

750
850intensity
900(DS+ 2016)950
CO (1-0) 800
integrated
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Integrated
intensity:

1000

1050 & [km1100
s *+ ]

1150
9

Molecular gas kinematics
CO (1-0) line intensity

29:30.0

Velocity field
Emission spectrum (e.g. CO J=1-0)
object approaching-37:30:00.0

object receding

intensity

30.0

29:30.0

31:00.0-37:30:00.0

30.0

1 kpc

30.0

galactic rotation
blue: approaching
red: receding

31:00.0

beam
48.0

46.0

44.0

42.0 5:07:40.0 38.0

beam

36.0
48.0

750
DS+ 2016800

750

850

900

1 kpc

30.0

950

46.0

44.0

800

42.0 5:07:40.0 38.0
850

1000

900

1050

line-of-sight velocity

36.0
950

1000

1100

1050

11001150

1150

Line-of-sight velocity (km/s)
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Molecular wind in NGC 1808
CO gas

OpticalCND
dust filame
nts

minor

CNDax
islinesplitting
100-150
km/s

CND

DS+ 2017

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Outflow dynamics• Velocity
Outflow velocity ~200 km/s at radius 1 kpc• Mass outflow rate dM/dt ~1-10 M⦿/yr~ total star formation rate (R<500 pc) ~5 M⦿/yr

DS+ 2017

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Molecular wind in NGC 253

White: molecular gas (intensityof emission line CO J=1-0 na 2.6mm) captured by ALMA
Blue: ionized gas (X-rays)
Bolatto+ (2013)

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Molecular wind in NGC 253• The molecular wind speed ~60 km/s relative to the center of the galaxy• Mass outflow rate (3-9 solar masses/year) > star formation rate (1-3 solar masses/year)• Conclusion: Star formation suppressed by the windwind (far side)rogal tatinactg
ic disk

wind (near side)
Bolatto+ (2013)

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14

Green: stars
Violet: hot gasConclusions• Galactic winds remove molecular gas and thus affect starformation activity and galaxy evolution.
• CO observations by ALMA revealed molecular winds in nearby
galaxies NGC NGC 1808 and NGC 253.
• NGC 1808: mass outflow rate ~ star formation rate
• NGC 253: mass outflow rate ~> star formation rateà suppressing star formation?

• Future work: How molecular winds form and evolve?
• In progress: ALMA observations of NGC 1482

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