THE FORMATION OF THE HIGH-VELOCITY CLOUDS OF THE MILKY WAY

Transcription

1 THE FORMATION OF THE HIGH-VELOCITY CLOUDS OF THE MILKY WAY Antonino Marasco Kapteyn Astronomical Institute, Groningen In collaboration with: Filippo Fraternali (University of Bologna) Federico Marinacci (MIT Kavli Institute) Lucia Armillotta (University of Bologna) The Periphery of disks, 4/11/2014, Sydney

2 The High Velocity Clouds van Woerden et al. (2004)

3 The High Velocity Clouds van Woerden et al. (2004)

4 Possible origins

5 Possible origins Bregman 1980 Galactic fountain

6 Possible origins Bregman 1980 Galactic fountain Gas ejected from satellites Olano 2008

7 Possible origins Bregman 1980 Galactic fountain Gas ejected from satellites Olano 2008 Direct cooling of the corona Kaufmann et al 2006

8 Possible origins Bregman 1980 Galactic fountain Gas ejected from satellites Olano 2008 Direct cooling of the corona Gas condensation in filaments Kaufmann et al 2006 Fernàndez et al 2012

9 Possible origins Bregman 1980 Galactic fountain Gas ejected from satellites Olano 2008 Direct cooling of the corona Gas condensation in filaments Kaufmann et al 2006 Fernàndez et al 2012

10 Supernova-driven gas accretion Fraternali et al. (2013)

11 Supernova-driven gas accretion Fraternali et al. (2013)

12 Supernova-driven gas accretion Fraternali et al. (2013)

13 Dynamical model & application to the MW Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona

14 Dynamical model & application to the MW Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona FIT TO THE MILKY WAY: NEUTRAL GAS Free parameters: kick velocity, condensation rate, ionisation fraction

15 Dynamical model & application to the MW FIT TO THE MILKY WAY: NEUTRAL GAS Free parameters: kick velocity, condensation rate, ionisation fraction MODEL Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona HI DATA (LAB Survey) (Marasco et al. 2012)

16 Dynamical model & application to the MW FIT TO THE MILKY WAY: NEUTRAL GAS Free parameters: kick velocity, condensation rate, ionisation fraction MODEL Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona HI DATA (LAB Survey) Intermediate-velocity HI is produced by GF coronal gas accretion rate ~ SFR (Marasco et al. 2012)

17 Dynamical model & application to the MW FIT TO THE MILKY WAY: IONISED GAS Free parameters: none Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona Ionised gas follows the simulations

18 Dynamical model & application to the MW FIT TO THE MILKY WAY: IONISED GAS Free parameters: none Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona Ionised gas follows the simulations MODEL - gas at <T< in the wakes of the fountain clouds DATA - UV absorption systems (Lehner et al. 2012) (Fraternali et al. 2013; Marasco et al. 2013)

19 Dynamical model & application to the MW FIT TO THE MILKY WAY: IONISED GAS Free parameters: none Axisymmetric Ballistic Fixed gravitational potential (GD, Model I) Ejection rate prop. to SFRD Exponential gas accretion from the corona Ionised gas follows the simulations MODEL - gas at <T< in the wakes of the fountain clouds DATA - UV absorption systems (Lehner et al. 2012) KS test gives 95% match The vast majority of the UV absorption systems are produced at the disc-corona interface (Fraternali et al. 2013; Marasco et al. 2013)

20 Application to Complex C

21 Application to Complex C New assumptions: ejection along a spiral arm ejection limited in location and time

22 Application to Complex C New assumptions: ejection along a spiral arm ejection limited in location and time New ingredients: Spiral arm model: Steiman-Cameron et al Pattern speed: 25 km/s (Gerhard 2011)

23 Application to Complex C New assumptions: ejection along a spiral arm ejection limited in location and time New ingredients: Spiral arm model: Steiman-Cameron et al Pattern speed: 25 km/s (Gerhard 2011) Free parameters: ejection velocity location size look-back time duration condensation rate

24 Application to Complex C New assumptions: ejection along a spiral arm ejection limited in location and time New ingredients: Spiral arm model: Steiman-Cameron et al Pattern speed: 25 km/s (Gerhard 2011) Free parameters: ejection velocity location size look-back time duration condensation rate Best-fit to the HI data via MCMC

25 Best-fit model to Complex C

26 Best-fit model to Complex C

27 Best-fit model to Complex C

28 Best-fit model to Complex C

29 Best-fit model to Complex C 2x10 54 erg ->1-2x10 6 Mo of stars in 50 Myr -> SFRD of 0.01 Mo/yr/kpc 2

30 Predictions Distance Metallicity

31 Predictions Distance Metallicity from the dynamical model

32 Predictions Distance Metallicity from the dynamical model from the hydrodynamical simulation for Zcloud=0.8 Zo; Zcorona=0.1 Zo

33 Predictions Distance Metallicity from the dynamical model from the hydrodynamical simulation for Zcloud=0.8 Zo; Zcorona=0.1 Zo Accretion rate < 0.2 Mo/yr

34 Conclusions A model of SN-driven gas accretion can reproduce: kinematics distance metallicity of the HVC Complex C.

35 Conclusions A model of SN-driven gas accretion can reproduce: kinematics distance metallicity of the HVC Complex C. Blowout occurred ~ 150 Myr ago in the Cygnus-Outer arm region and lasted ~ 50 Myr

36 Conclusions A model of SN-driven gas accretion can reproduce: kinematics distance metallicity of the HVC Complex C. Blowout occurred ~ 150 Myr ago in the Cygnus-Outer arm region and lasted ~ 50 Myr The model is energetically plausible