dynamical regulation of star formation Sharon E. Meidt (MPIA) A. - - PowerPoint PPT Presentation

Sharon E. Meidt (MPIA)

dynamical regulation of star formation

• A. Hughes, E. Schinnerer, S. Garcia-Burillo,
• D. Colombo, C. Dobbs, A. Leroy, C. Kramer,
• K. Schuster, G. Dumas, T. Thompson

Saturday, July 19, 14

Text

+ +

n≈1.5

Global Star Formation Relation

ΣSFR =ΣH2

power-law relation

n

n=1

‘starbursts’ ‘normal disks’

Kennicutt (1998)

ΣSFR =ΣH2/τ

τ = τff

= cloud free-

fall time??

Saturday, July 19, 14

Text

spatially-resolved Star Formation Relation

universal molecular gas depletion time ??

Bigiel et al. (2008;2011)

n=1 n=1.5

Saturday, July 19, 14

Text

spatially-resolved Star Formation Relation

universal molecular gas depletion time ??

Bigiel et al. (2008;2011)

n=1 n=1.5

τdep= ΣH2 /ΣSFR

constant molecular gas depletion time

Saturday, July 19, 14

Text

spatially-resolved Star Formation Relation

universal molecular gas depletion time ??

Bigiel et al. (2008;2011)

n=1 n=1.5

Is there a ‘universal cloud’? (one tff, one Σ?)

τdep= ΣH2 /ΣSFR

constant molecular gas depletion time

Saturday, July 19, 14

Text

spatially-resolved Star Formation Relation

universal molecular gas depletion time ??

Bigiel et al. (2008;2011)

n=1

Is there a ‘universal cloud’? (one tff, one Σ?)

τdep= ΣH2 /ΣSFR

constant molecular gas depletion time

Saturday, July 19, 14

Text

spatially-resolved Star Formation Relation

universal molecular gas depletion time ??

Bigiel et al. (2008;2011)

n=1

Is there a ‘universal cloud’? (one tff, one Σ?)

τdep= ΣH2 /ΣSFR

constant molecular gas depletion time

long τdep short τdep

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

Scatter in the Star Formation relation

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

• 2 modes of star formation?

(Krumholz et al. 2011)

• scale-dependent scatter:

‘discreteness +stochasticity’:

• temporal & spatial decoupling of

gas and stars (Feldman et al. 2011)

• stellar feedback--cloud dispersal/

destruction

Scatter in the Star Formation relation

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

• 2 modes of star formation?

(Krumholz et al. 2011)

• scale-dependent scatter:

‘discreteness +stochasticity’:

• temporal & spatial decoupling of

gas and stars (Feldman et al. 2011)

• stellar feedback--cloud dispersal/

destruction

Scatter in the Star Formation relation

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

• 2 modes of star formation?

(Krumholz et al. 2011)

• scale-dependent scatter:

‘discreteness +stochasticity’:

• temporal & spatial decoupling of

gas and stars (Feldman et al. 2011)

• stellar feedback--cloud dispersal/

destruction

Scatter in the Star Formation relation

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

• 2 modes of star formation?

(Krumholz et al. 2011)

• scale-dependent scatter:

‘discreteness +stochasticity’:

• temporal & spatial decoupling of

gas and stars (Feldman et al. 2011)

• stellar feedback--cloud dispersal/

destruction

Scatter in the Star Formation relation

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

• 2 modes of star formation?

(Krumholz et al. 2011)

• scale-dependent scatter:

‘discreteness +stochasticity’:

• temporal & spatial decoupling of

gas and stars (Feldman et al. 2011)

• stellar feedback--cloud dispersal/

destruction

Scatter in the Star Formation relation

Saturday, July 19, 14

Text

Bigiel et al. (2008)

250pc 500pc 750pc

log(star formation rate) log(gas surface density) M51

1kpc

• 2 modes of star formation?

(Krumholz et al. 2011)

• scale-dependent scatter:

‘discreteness +stochasticity’:

• temporal & spatial decoupling of

gas and stars (Feldman et al. 2011)

• stellar feedback--cloud dispersal/

destruction

• galaxy dynamics

Scatter in the Star Formation relation

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical regulation of star formation

large small

spatial scale

10s kpc pc 10s pc

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical regulation of star formation

• Torques drive large-scale gas motions in disk

large small

spatial scale

10s kpc pc 10s pc

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical regulation of star formation

• Torques drive large-scale gas motions in disk
• Gas brought from large to small R

large small

spatial scale

10s kpc pc 10s pc

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical regulation of star formation

• Torques drive large-scale gas motions in disk
• Gas brought from large to small R
• On the way, gas can be stabilized
• dynamical suppression of SF = ‘effective feedback’
• clouds can be sheared ⇒ finite lifetimes

large small

spatial scale

10s kpc pc 10s pc

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical regulation of star formation

• Torques drive large-scale gas motions in disk
• Gas brought from large to small R
• On the way, gas can be stabilized
• dynamical suppression of SF = ‘effective feedback’
• clouds can be sheared ⇒ finite lifetimes
• other gas makes it to center
• BH growth and feedback

large small

spatial scale

10s kpc pc 10s pc

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Outline

• Gas brought from large to small R
• On the way, gas can be stabilized
• dynamical suppression of SF = ‘effective feedback’
• clouds can be sheared ⇒ finite lifetimes

high resolution molecular gas key

• Torques drive large-scale gas motions in disk

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Outline

• Gas brought from large to small R
• On the way, gas can be stabilized
• dynamical suppression of SF = ‘effective feedback’
• clouds can be sheared ⇒ finite lifetimes

high resolution molecular gas key

• Torques drive large-scale gas motions in disk

(also: precise maps of stellar mass)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

gravitational Torques via non-axisymmetric perturbations

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

mergers and interactions

gravitational Torques via non-axisymmetric perturbations

Cox et al. 2008, MNRAS, 384, 386

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

disk galaxy potentials

Bars Spirals Late-type disks

gravitational Torques via non-axisymmetric perturbations

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

stellar mass distribution

M51

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

R×∇Φ

+ + + +

• CO

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

inflow

• utflow

inertial torques stellar mass distribution

M51

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

R×∇Φ

+ + + +

• CO

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

<Γ>(R)

azimuthal bins

R(arcsec)

inflow

• utflow

inertial torques stellar mass distribution

M51

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

R×∇Φ

+ + + +

• CO

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

<Γ>(R)

azimuthal bins

R(arcsec)

inflow

• utflow

inertial torques stellar mass distribution

M51

inflow to center!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

R×∇Φ

+ + + +

• CO

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

<Γ>(R)

azimuthal bins

R(arcsec)

inflow

• utflow

inertial torques stellar mass distribution

M51

bar end inflow to center!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

R×∇Φ

+ + + +

• CO

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

<Γ>(R)

azimuthal bins

R(arcsec)

inflow

• utflow

inertial torques stellar mass distribution

M51

bar end spiral corotation inflow to center!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Garcia-Burillo et al. (2005, 2009); NUGA Meidt et al. (2013)

Present-day gravitational Torques

Msol pc-2

R×∇Φ

+ + + +

• CO

Meidt et al. (2012a) Querjeta, Meidt et al (2014) Meidt et al. (2014)

<Γ>(R)

azimuthal bins

R(arcsec)

inflow

• utflow

inertial torques stellar mass distribution

M51

bar end ring pile-up spiral corotation inflow to center!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

gas kinematics

non-circular streaming motions

Vradial Vazimuthal

motions directed along and through spiral arm

(see Roberts & Stewart 1987; Wong, Blitz & Bosma 2004)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

gas kinematics

non-circular streaming motions

Vradial Vazimuthal

motions directed along and through spiral arm

(see Roberts & Stewart 1987; Wong, Blitz & Bosma 2004)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

gas kinematics

non-circular streaming motions

Vradial Vazimuthal

motions directed along and through spiral arm

(see Roberts & Stewart 1987; Wong, Blitz & Bosma 2004)

view depends on choice of tracer!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

non-circular streaming motions

different distributions == different kinematics

(Colombo, SEM et al. 2014b)

10 20 30 40 50

HI (6”) CO (6”) CO (1”)

gas kinematics

in M51

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

non-circular streaming motions

different distributions == different kinematics

(Colombo, SEM et al. 2014b)

10 20 30 40 50

HI (6”) CO (6”)

• molecular gas is
• clumpier (Leroy et al. 2013)
• denser, confined more to mid-plane
• in spiral potential well minimum

(HI typically offset; e.g. Rand & Kulkarni 1990)

CO (1”)

gas kinematics

in M51

Saturday, July 19, 14

Molecular Gas disk of M51

Schuster et al. (2007)

single dish (~ 500 pc)

Saturday, July 19, 14

Molecular Gas disk of M51

Schuster et al. (2007)

single dish (~ 500 pc)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

PAWS view

(PI:Schinnerer)

IRAM ¡ 30m: ¡40 ¡hr PdBI: ¡170 ¡hr

CO(1-­‑0) ¡in ¡central ¡9kpc ¡at GMC ¡resolution ¡(40pc, ¡105Msun)

(Pety et al. 2013; Schinnerer et al. 2013)

Colombo et al. (2014a): CPROPS catalog of over 1900 Molecular Clouds

Saturday, July 19, 14

Molecular Gas kinematics in M51

Colombo ¡et ¡al. ¡(2014b)

~40 km s-1 non- circular streaming motions!

bar twist

Saturday, July 19, 14

Molecular Gas kinematics in M51

Colombo ¡et ¡al. ¡(2014b)

~40 km s-1 non- circular streaming motions!

bar twist

Saturday, July 19, 14

Molecular Gas kinematics in M51

Colombo ¡et ¡al. ¡(2014b)

~40 km s-1 non- circular streaming motions!

bar twist

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• streaming motions funnel gas through/along spiral arms
• build up high densities
• + reduce shear

star formation (always?)

ORGANIZATION STRUCTURE

the role of spiral arms

& M51

HST ACS

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• streaming motions funnel gas through/along spiral arms
• build up high densities
• + reduce shear

star formation (always?)

ORGANIZATION STRUCTURE

the role of spiral arms

M51

HST ACS

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• streaming motions funnel gas through/along spiral arms
• build up high densities
• + reduce shear

star formation (always?)

ORGANIZATION STRUCTURE

the role of spiral arms

• large-scale down to scale of Giant Molecular Clouds,

the star-forming unit !!

M51

HST ACS

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• streaming motions funnel gas through/along spiral arms
• build up high densities
• + reduce shear
• massive clouds build/form in spiral arms via convergent

flows, collisions & self-gravity (M51, IC 342; Hirota et al. 2011; Koda

et al. 2009; Egusa, Koda & Scoville 2010)

star formation (always?)

ORGANIZATION STRUCTURE

the role of spiral arms

• large-scale down to scale of Giant Molecular Clouds,

the star-forming unit !!

M51

HST ACS

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• cloud Cumulative Mass Spectra

spiral arms help build more and larger clouds dispersal in inter- arm due to shear, feedback

the role of spiral arms

log Mlum [Msun] log Ncl [(m>M)/kpc2]

Columbo et al. (2014a)

• Colombo et al.

(2014a): PAWS GMC catalog of

• ver 1900 clouds

across central 9 kpc in M51

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• cloud Cumulative Mass Spectra

spiral arms help build more and larger clouds dispersal in inter- arm due to shear, feedback

the role of spiral arms

log Mlum [Msun] log Ncl [(m>M)/kpc2]

Columbo et al. (2014a)

• Colombo et al.

(2014a): PAWS GMC catalog of

• ver 1900 clouds

across central 9 kpc in M51

center spiral interarm

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• cloud Cumulative Mass Spectra

spiral arms help build more and larger clouds dispersal in inter- arm due to shear, feedback

the role of spiral arms

log Mlum [Msun] log Ncl [(m>M)/kpc2]

Columbo et al. (2014a)

• Colombo et al.

(2014a): PAWS GMC catalog of

• ver 1900 clouds

across central 9 kpc in M51

center spiral interarm

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• cloud Cumulative Mass Spectra

spiral arms help build more and larger clouds dispersal in inter- arm due to shear, feedback

the role of spiral arms

log Mlum [Msun] log Ncl [(m>M)/kpc2]

Columbo et al. (2014a)

more larger

• Colombo et al.

(2014a): PAWS GMC catalog of

• ver 1900 clouds

across central 9 kpc in M51

center spiral interarm

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• cloud properties, scaling relations

the role of spiral arms

M51 M33 LMC B08

Hughes et al. (2013b)

log (radius) log (velocity dispersion) no size-line width relation clouds are not (always) virialized log (radius) log (CO Luminosity)

¡ 4 4 4 ¡ Msun p c-­‑2 ΣH2= ¡4 ¡Msunpc-­‑2 M W ¡ ( S 8 7 )

• exgal. ¡(B08)

➱ ➱

completely unexpected:

large range of gas surface densities GMC properties are not universal no universal free-fall time! scatter in KS relation

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• cloud properties, scaling relations

the role of spiral arms

M51 M33 LMC B08

Hughes et al. (2013b)

log (radius) log (velocity dispersion) no size-line width relation clouds are not (always) virialized log (radius) log (CO Luminosity)

¡ 4 4 4 ¡ Msun p c-­‑2 ΣH2= ¡4 ¡Msunpc-­‑2 M W ¡ ( S 8 7 )

• exgal. ¡(B08)

➱ ➱

completely unexpected:

large range of gas surface densities GMC properties are not universal

clouds in ARM are

• brighter,
• more massive,
• higher gas surface density

compared to inter-ARM

no universal free-fall time! scatter in KS relation

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

varying properties with dynamical environment

the role of external pressure

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

varying properties with dynamical environment

• how do clouds inherit from

environment?

• Pint~Pext (Hughes, SEM et al. 2013a)

the role of external pressure

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

varying properties with dynamical environment

• how do clouds inherit from

environment?

• Pint~Pext (Hughes, SEM et al. 2013a)

Hughes, Meidt et al. (2013a)

the role of external pressure

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

varying properties with dynamical environment

• how do clouds inherit from

environment?

• Pint~Pext (Hughes, SEM et al. 2013a)

Hughes, Meidt et al. (2013a)

clouds coupled to surroundings

the role of external pressure

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

varying properties with dynamical environment

• how do clouds inherit from

environment?

• Pint~Pext (Hughes, SEM et al. 2013a)

Hughes, Meidt et al. (2013a)

KEY: surface pressure important!

clouds coupled to surroundings

• changes in pressure-balance (due

to non-circ motions) alter cloud stability (Meidt et al. 2013) the role of external pressure

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure Meidt et al. (2013)

• cf. Jog (2013a,b)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure Meidt et al. (2013)

• cf. Jog (2013a,b)

`

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure

• Bernoulli: gas in motion,

Meidt et al. (2013)

• cf. Jog (2013a,b)

` reduced pressure within gas, on clouds

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure

• Bernoulli: gas in motion,

Meidt et al. (2013)

• cf. Jog (2013a,b)
• increased cloud stable mass

(bigger before collapse)

• fewer collapse-unstable clouds
• lower star formation, longer τdep

` reduced pressure within gas, on clouds

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure

• Bernoulli: gas in motion,

Meidt et al. (2013)

• cf. Jog (2013a,b)
• increased cloud stable mass

(bigger before collapse)

• fewer collapse-unstable clouds
• lower star formation, longer τdep

` reduced pressure within gas, on clouds

log ¡Mlum ¡[Msun] ¡ log ¡Ncl ¡[(m>M)/kpc2] ¡

cloud mass spectrum

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure

• Bernoulli: gas in motion,

Meidt et al. (2013)

• cf. Jog (2013a,b)
• increased cloud stable mass

(bigger before collapse)

• fewer collapse-unstable clouds
• lower star formation, longer τdep

` reduced pressure within gas, on clouds

log ¡Mlum ¡[Msun] ¡ log ¡Ncl ¡[(m>M)/kpc2] ¡

cloud mass spectrum

unstable stable

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

dynamical pressure

• Bernoulli: gas in motion,

Meidt et al. (2013)

• cf. Jog (2013a,b)
• increased cloud stable mass

(bigger before collapse)

• fewer collapse-unstable clouds
• lower star formation, longer τdep

` reduced pressure within gas, on clouds

log ¡Mlum ¡[Msun] ¡ log ¡Ncl ¡[(m>M)/kpc2] ¡

cloud mass spectrum

unstable stable

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

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1.9 2.0 2.1 2.2 2.3 2.4 2.5

• 1.5
• 1.0
• 0.5

0.0 0.5 log10SH2 HMsol kpc-2L log10SSFR HMsol pc-2 yr-1L

log (molecular surface density) l

• g

( S F R s u r f . d e n s . )

velocity

PAWS CO Ha + 24 micron M51

depletion time variation due to dynamics

depletion time τdep= ΣH2 /ΣSFR

109.5 Gyr 109 Gyr 108.5 Gyr

lines of constant τdep

Saturday, July 19, 14

Molecular Gas disk of M51

¡

? ?

CO(1-0) in central 9kpc at cloud resolution (40pc, 105Msun)

Saturday, July 19, 14

white contours: CO

Spatial Relation b/n Gas and Star Formation

Saturday, July 19, 14

Spatial Relation b/n Gas and Star Formation

white contours: CO

Saturday, July 19, 14

Spatial Relation b/n Gas and Star Formation

ln gas depletion time

‘universal’ time (Bigiel et al. 2008)

white contours: CO

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

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1.9 2.0 2.1 2.2 2.3 2.4 2.5

• 1.5
• 1.0
• 0.5

0.0 0.5 log10SH2 HMsol kpc-2L log10SSFR HMsol pc-2 yr-1L

log (molecular surface density) l

• g

( S F R s u r f . d e n s . )

velocity

PAWS CO Ha + 24 micron M51

depletion time variation due to dynamics

depletion time τdep= ΣH2 /ΣSFR

109.5 Gyr 109 Gyr 108.5 Gyr

lines of constant τdep

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

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1.9 2.0 2.1 2.2 2.3 2.4 2.5

• 1.5
• 1.0
• 0.5

0.0 0.5 log10SH2 HMsol kpc-2L log10SSFR HMsol pc-2 yr-1L

log (molecular surface density) l

• g

( S F R s u r f . d e n s . )

velocity

PAWS CO Ha + 24 micron M51

depletion time variation due to dynamics

depletion time τdep= ΣH2 /ΣSFR

109.5 Gyr 109 Gyr 108.5 Gyr

lines of constant τdep

star formation still occurs near spiral arms, but not as efficiently as it ‘could’

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

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1.9 2.0 2.1 2.2 2.3 2.4 2.5

• 1.5
• 1.0
• 0.5

0.0 0.5 log10SH2 HMsol kpc-2L log10SSFR HMsol pc-2 yr-1L

log (molecular surface density) l

• g

( S F R s u r f . d e n s . )

velocity

PAWS CO Ha + 24 micron M51

depletion time variation due to dynamics

depletion time τdep= ΣH2 /ΣSFR

109.5 Gyr 109 Gyr 108.5 Gyr

lines of constant τdep

star formation still occurs near spiral arms, but not as efficiently as it ‘could’ stronger spiral (stronger streaming), more suppression

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

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1.9 2.0 2.1 2.2 2.3 2.4 2.5

• 1.5
• 1.0
• 0.5

0.0 0.5 log10SH2 HMsol kpc-2L log10SSFR HMsol pc-2 yr-1L

log (molecular surface density) l

• g

( S F R s u r f . d e n s . )

velocity

PAWS CO Ha + 24 micron M51

depletion time variation due to dynamics

depletion time τdep= ΣH2 /ΣSFR

109.5 Gyr 109 Gyr 108.5 Gyr

lines of constant τdep

star formation still occurs near spiral arms, but not as efficiently as it ‘could’ stronger spiral (stronger streaming), more suppression

NGC 4303

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

depletion time variation due to dynamics

since spirals stronger in more massive disks, τdep larger in

(well-defined dispersion relation)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

depletion time variation due to dynamics

what if we also limit cloud lifetimes?

Leroy et al. 2013

strong streaming weak streaming

‘starburst’

since spirals stronger in more massive disks, τdep larger in

mass

(well-defined dispersion relation)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Saintonge et al. (2013) COLD GASS global measurements

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

in massive Early-type galaxies

depletion time variation due to dynamics

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

in massive Early-type galaxies

Davis et al. (2014)

= rotation curve shape

shear

fast rising (flat) slow rising (solid-body=1)

depletion time variation due to dynamics

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

in massive Early-type galaxies

Davis et al. (2014)

= rotation curve shape

shear

fast rising (flat) slow rising (solid-body=1)

depletion time variation due to dynamics

(but β=0 in disks)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Shear limits cloud lifetimes

• cloud lifetime in M51 ~ shear timescale Oort A-1 (Meidt & PAWS in prep.)
• also found in numerical simulations (Dobbs & Pringle 2013)
• short cloud lifetimes<tff, perhaps not long enough for star formation

torb 1

π

(1-β)

= A-1

in disks, in the centers, β=0 and torb very long! β=0 but torb short!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Take Away

• not all cold, dense (molecular) clouds form stars.....

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Take Away

• not all cold, dense (molecular) clouds form stars.....

➡dynamics regulates organization, structure and stability of molecular gas

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Take Away

• not all cold, dense (molecular) clouds form stars.....

➡dynamics regulates organization, structure and stability of molecular gas ➡same large-scale processes that fuel centers also suppress star formation

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

‘upstream’ zone II ‘downstream’ zone I

ARM center

dynamical environments

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

‘upstream’ zone II ‘downstream’ zone I

ARM center

dynamical environments• mostly only destruction

• interarm easy to dynamically

characterize

• clouds follow circular paths (very little

radial excursion)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

‘upstream’ zone II ‘downstream’ zone I

ARM center

dynamical environments• mostly only destruction

• interarm easy to dynamically

characterize

• clouds follow circular paths (very little

radial excursion)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

‘upstream’ zone II ‘downstream’ zone I

ARM center

phase

zone I zone II

dynamical environments• mostly only destruction

• interarm easy to dynamically

characterize

• clouds follow circular paths (very little

radial excursion)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

• cloud numbers decreases from zone I to

zone II (Colombo et al. 2013)

• mass spectrum evolution: shear and star

formation feedback destroy clouds, limit lifetimes

‘upstream’ zone II ‘downstream’ zone I

ARM center

phase

zone I zone II

dynamical environments

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

• cloud numbers decreases from zone I to

zone II (Colombo et al. 2013)

• mass spectrum evolution: shear and star

formation feedback destroy clouds, limit lifetimes

‘upstream’ zone II ‘downstream’ zone I

ARM center

phase

zone I zone II

dynamical environments

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

• cloud numbers decreases from zone I to

zone II (Colombo et al. 2013)

• mass spectrum evolution: shear and star

formation feedback destroy clouds, limit lifetimes

‘upstream’ zone II ‘downstream’ zone I

ARM center

phase

zone I zone II

dynamical environments

shear feedback

Oort A =Ω-B =Ω/2

(for V flat)

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

• cloud numbers decreases from zone I to

zone II (Colombo et al. 2013)

• mass spectrum evolution: shear and star

formation feedback destroy clouds, limit lifetimes

‘upstream’ zone II ‘downstream’ zone I

ARM center

phase

zone I zone II

dynamical environments

shear feedback

Oort A =Ω-B =Ω/2

(for V flat)

mass loss and dispersal

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

short gmc lifetimes: an observational estimate with PAWS!

• cloud numbers decreases from zone I to

zone II (Colombo et al. 2013)

• mass spectrum evolution: shear and star

formation feedback destroy clouds, limit lifetimes

‘upstream’ zone II ‘downstream’ zone I

ARM center

phase

zone I zone II

dynamical environments

shear feedback

Oort A =Ω-B =Ω/2

(for V flat)

mass loss and dispersal transformation

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

a (simple) framework

if cloud numbers decrease from zone I to zone II then lifetime < travel time from arm to arm

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

a (simple) framework

if cloud numbers decrease from zone I to zone II then lifetime < travel time from arm to arm

arm arm I II

time Eulerian vs. Lagrangian

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

split interarm in half, count NI and NII

a (simple) framework

if cloud numbers decrease from zone I to zone II then lifetime < travel time from arm to arm

half arm-to-arm travel time; measure from torb lost

• riginal

arm arm I II

time Eulerian vs. Lagrangian

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014
• still sources + sinks (feedback cloud

splitting, etc.)

split interarm in half, count NI and NII

a (simple) framework

if cloud numbers decrease from zone I to zone II then lifetime < travel time from arm to arm

half arm-to-arm travel time; measure from torb lost

• riginal

when and i.e. mostly losses

arm arm I II

time Eulerian vs. Lagrangian

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

≈

• still sources + sinks (feedback cloud

splitting, etc.)

split interarm in half, count NI and NII

a (simple) framework

if cloud numbers decrease from zone I to zone II then lifetime < travel time from arm to arm

half arm-to-arm travel time; measure from torb lost

• riginal

when and i.e. mostly losses

high Flost

short τ

small Flost

long τ

• pop. growth

(transformation)

arm arm I II

time Eulerian vs. Lagrangian

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

many lost

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

many lost fewer lost

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

• shear timescale: short!

just a few free-fall times!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

• shear timescale: short!
• feedback timescale
• here transformation

τgrow≈τtrue so τ overestimates τtrue

• when Flost=low, in M51:

~25Myr

just a few free-fall times!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

• shear timescale: short!
• feedback timescale
• here transformation

τgrow≈τtrue so τ overestimates τtrue

• when Flost=low, in M51:

~25Myr

just a few free-fall times!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

• shear timescale: short!
• feedback timescale
• here transformation

τgrow≈τtrue so τ overestimates τtrue

• when Flost=low, in M51:

~25Myr feedback becomes dominant when A-1 exceeds 25 Myr

just a few free-fall times!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

• shear timescale: short!
• feedback timescale
• here transformation

τgrow≈τtrue so τ overestimates τtrue

• when Flost=low, in M51:

~25Myr

just a few free-fall times!

Saturday, July 19, 14

• S. E. Meidt--Q&Q July 2014

GMC lifetimes

• shear timescale: short!
• feedback timescale
• here transformation

τgrow≈τtrue so τ overestimates τtrue

• when Flost=low, in M51:

~25Myr

shear timescale > feedback timescale

spiral arms low mass disks

shear timescale < feedback timescale

centers of galaxies normal L* disks

τ is short ~15-20 Myr τ is longer ~25Myr

just a few free-fall times!

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

ln τdep≈-(γ+1) |vstream|2 4σ2 +ln τdep,0

Radius (arcsec)

Meidt et al. (2013)

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

ln τdep≈-(γ+1) |vstream|2 4σ2 +ln τdep,0

Radius (arcsec)

Meidt et al. (2013)

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

ln τdep≈-(γ+1) |vstream|2 4σ2 +ln τdep,0

Radius (arcsec)

Meidt et al. (2013)

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

ln τdep≈-(γ+1) |vstream|2 4σ2 +ln τdep,0

Radius (arcsec)

Meidt et al. (2013)

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

ln τdep≈-(γ+1) |vstream|2 4σ2 +ln τdep,0

Radius (arcsec)

Meidt et al. (2013)

streaming motions lengthen gas depletion time

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

gravitational disk stability

Meidt et al.(2013)

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

support not entirely from

Meidt et al. (2013)

GMC Stabilization in M51

• preferentially enhanced

turbulent motions (regular σ

along spiral)

• stellar feedback (little Hα, UV,

clusters <70Myr)

what shuts off star formation?

shear

A Aspiral

• spiral arm shear (Oort A;
• cf. Dib & Helou 2012)

ln gas depletion time

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

cloud stability

in the spiral shock

• cloud collisions/agglomeration:

σ increases (Bonnell et al. 2006; Kim, Kim &

Ostriker 2006), unbound fraction

increases?

• do we see individual bound clouds

embedded in a larger unbound structure?

• --> low overall SFE?

Schinnerer et al.(2013) Meidt et al.(2013)

Mclouds/Marm

angular offset (deg)

Saturday, July 19, 14

Sharon E. Meidt Colloquium, January 27, 2014

cloud stability

in the spiral shock

• cloud collisions/agglomeration:

σ increases (Bonnell et al. 2006; Kim, Kim &

Ostriker 2006), unbound fraction

increases?

• do we see individual bound clouds

embedded in a larger unbound structure?

• --> low overall SFE?

Schinnerer et al.(2013) Meidt et al.(2013)

Mclouds/Marm

angular offset (deg)

Saturday, July 19, 14