Star Formation and Gas Alwin Mao March 21, 2019 10 2 1000 800 10 - - PowerPoint PPT Presentation

▶
star formation and gas
SMART_READER_LITE
LIVE PREVIEW

Star Formation and Gas Alwin Mao March 21, 2019 10 2 1000 800 10 - - PowerPoint PPT Presentation

Feb 17, 2024 341 likes •605 views

Star Formation and Gas Alwin Mao March 21, 2019 10 2 1000 800 10 1 600 ( M pc Y (pc) 400 2 ) 10 0 200 0 10 1 0 200 400 600 800 1000 X (pc) Collaborators: Eve Ostriker, Chang-Goo Kim Outline 1 Introduction: Efficiency of What Gas?

slide-1
SLIDE 1

Star Formation and Gas

Alwin Mao March 21, 2019

200 400 600 800 1000 X (pc) 200 400 600 800 1000 Y (pc) 10

1

100 101 102 (M pc

2)

Collaborators: Eve Ostriker, Chang-Goo Kim

slide-2
SLIDE 2

Outline

1 Introduction: Efficiency of What Gas? 2 Time Series: Delay and Variability 3 Correlation Comparison of Density vs. Energy 4 Plans++

Alwin Mao Star Formation and Gas March 21, 2019 2 / 23

slide-3
SLIDE 3

Outline

1 Introduction: Efficiency of What Gas? 2 Time Series: Delay and Variability 3 Correlation Comparison of Density vs. Energy 4 Plans++

Alwin Mao Star Formation and Gas March 21, 2019 3 / 23

slide-4
SLIDE 4

Motivation - Efficiency per free-fall time

  • SFR = ǫff

M tff

  • ǫff ∼ 10−2 on galactic scales
  • ǫff ∼ 1 for bound collapsing objects?
  • ǫff ∝ e−βtdyn/tff
  • β = 1.6 (Padoan, Haugbolle, and Nordlund 2012)
  • αv < 2?

Alwin Mao Star Formation and Gas March 21, 2019 4 / 23

slide-5
SLIDE 5

Motivation - TIGRESS

  • Athena MHD + self gravity + cooling/heating
  • Sink/star particles and supernova feedback
  • Galactic potential, kpc shearing box, tall box, pc resolution
  • Three-phase ISM in Galaxies Resolving Evolution with Star

formation and Supernova feedback.

Alwin Mao Star Formation and Gas March 21, 2019 5 / 23

slide-6
SLIDE 6

Density Threshold

200 400 600 800 1000 X (pc) 200 400 600 800 1000 Y (pc) 10

1

100 101 102 (M pc

2)

10

1

100 101 102 (M pc

2) Alwin Mao Star Formation and Gas March 21, 2019 6 / 23

slide-7
SLIDE 7

Gravitational Energy - Isocontour

Alwin Mao Star Formation and Gas March 21, 2019 7 / 23

slide-8
SLIDE 8
  • Grav. Energy - Well

AB A B a b ab ab AB A B a b ab

Alwin Mao Star Formation and Gas March 21, 2019 8 / 23

slide-9
SLIDE 9
  • Grav. Energy - Tree Example

10 20 30 40 50 60 Tree Index 320 310 300 290 280 270 260 250 240

411 200 400 600 800 1000 X (pc) 200 400 600 800 1000 Y (pc) 10

1

100 101 102 (M pc

2)

Alwin Mao Star Formation and Gas March 21, 2019 9 / 23

slide-10
SLIDE 10
  • Grav. Energy - Tree (Merged Example)

2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 Tree Index 820 810 800 790 780

555

Alwin Mao Star Formation and Gas March 21, 2019 10 / 23

slide-11
SLIDE 11
  • Grav. Energy - Movie

200 400 600 800 1000 X (pc) 200 400 600 800 1000 Y (pc) 10

1

100 101 102 (M pc

2) Alwin Mao Star Formation and Gas March 21, 2019 11 / 23

slide-12
SLIDE 12

Outline

1 Introduction: Efficiency of What Gas? 2 Time Series: Delay and Variability 3 Correlation Comparison of Density vs. Energy 4 Plans++

Alwin Mao Star Formation and Gas March 21, 2019 12 / 23

slide-13
SLIDE 13

Time Series - Density

10

1

100 101 nH 10

0.5 0cm 3

SFR density bin delayed 10

1

100 101 nH 100

0.5cm 3

300 350 400 450 500 550 600 650 700 Time (Myr) 10

1

100 101 nH 100.5

1cm 3 ff (Mass / tff) / <SFR>

Alwin Mao Star Formation and Gas March 21, 2019 13 / 23

slide-14
SLIDE 14

Time Series - High Density

10

1

100 101 nH 101

1.5cm 3

SFR density bin delayed 10

1

100 101 nH 101.5

2cm 3

300 350 400 450 500 550 600 650 700 Time (Myr) 10

1

100 101 nH 102

2.5cm 3 ff (Mass / tff) / <SFR>

Alwin Mao Star Formation and Gas March 21, 2019 14 / 23

slide-15
SLIDE 15

Time Series - Density Time Delay

101 102 nH, min(cm

3)

101 Time (Myr) Time Series tff, min tff, max

Alwin Mao Star Formation and Gas March 21, 2019 15 / 23

slide-16
SLIDE 16

Time Series - Energy-selected

10

1

100 101 HBR SFR density bin delayed 300 350 400 450 500 550 600 650 700 Time (Myr) 10

1

100 101 HBP

ff (Mass / tff) / <SFR> Alwin Mao Star Formation and Gas March 21, 2019 16 / 23

slide-17
SLIDE 17

Outline

1 Introduction: Efficiency of What Gas? 2 Time Series: Delay and Variability 3 Correlation Comparison of Density vs. Energy 4 Plans++

Alwin Mao Star Formation and Gas March 21, 2019 17 / 23

slide-18
SLIDE 18

Correlation - Constant ǫff Model between 10−2 − 1

nH > 10 nH > 30 nH > 100 HBR 10

2

10

1

100

ff

nH > 10 nH > 30 nH > 100 HBR 0.0 0.2 0.4 0.6 0.8 1.0

SFR/ < SFR >

Alwin Mao Star Formation and Gas March 21, 2019 18 / 23

slide-19
SLIDE 19

Correlation - ǫff ∝ e−βtdyn/tff Model

nH > 10 nH > 30 nH > 100 HBR 1.0 0.5 0.0 0.5 1.0 1.5 2.0 nH > 10 nH > 30 nH > 100 HBR 0.0 0.2 0.4 0.6 0.8 1.0

SFR/ < SFR >

Alwin Mao Star Formation and Gas March 21, 2019 19 / 23

slide-20
SLIDE 20

Correlation - αv < Cutoff αv Model

nH > 10 nH > 30 nH > 100 HBR 1 2 3 4 5 6 7 8 9 Cutoff

v

nH > 10 nH > 30 nH > 100 HBR 0.0 0.2 0.4 0.6 0.8 1.0

SFR/ < SFR >

Alwin Mao Star Formation and Gas March 21, 2019 20 / 23

slide-21
SLIDE 21

Outline

1 Introduction: Efficiency of What Gas? 2 Time Series: Delay and Variability 3 Correlation Comparison of Density vs. Energy 4 Plans++

Alwin Mao Star Formation and Gas March 21, 2019 21 / 23

slide-22
SLIDE 22

Plans++

  • Form stellar cores in turbulent boxes in dense (100-10000 cm−3)

gas

  • Compare various Lagrangian Tracer Particle implementations
  • Figure out ways to distill understanding

Alwin Mao Star Formation and Gas March 21, 2019 22 / 23

slide-23
SLIDE 23

Conclusions

  • Time delay ≈ tff
  • ǫff depends on gas selection
  • More sophisticated energy-based selection not necessarily closer

to SFR

  • Most mass is unbound, and does not stay bound for long (few

Myr)

  • Unbound objects are involved in star formation

Alwin Mao Star Formation and Gas March 21, 2019 23 / 23