Image credit: M. S. Povich

Christoph Federrath

Astrophysical Gas Dynamics

ASTR4012 / ASTR8002

ANU – 2nd semester 2018

Course and Tutorials: Mondays and Wednesdays 9-11

Webpage:

Image credit: M. S. Povich

Topics:- Motivation (most of astrophysics is gas dynamics: stars, accretion discs, galaxies)- Hydrodynamical Equations (derivation, Eulerian, Lagrangian, conservation laws)- Waves and Shocks- Turbulence- Magnetohydrodynamics- Accretion and Winds

- Computational Fluid dynamics (numerical solution of hydro equations, advection)- -> get computer account at RSAA; application form on course web page

Astrophysical Gas Dynamics

Resources:Lecture notes by Ogilvie, Sormani, Bai, Zaroubi, ZingaleSijaki: https://www.ast.cam.ac.uk/students/undergrad/part_ii/lectures/fluids

Fluid Mechanics Films:http://web.mit.edu/hml/ncfmf.html

Image credit: M. S. Povich

- Need at least one student rep (by end of week 2) -> Rosie Iervasi- Student rep communicates with students and course convener- Student rep name and email address published on Wattle website- Please nominate yourself or someone else, if you are interested

Astrophysical Gas Dynamics

Image credit: M. S. Povich

Astrophysical Gas Dynamics

- assessment based on 4 assignments in total- 4th assignment counts double as final exam- one assignment per about every 2-3 weeks- assignments published on webpage- submission via email (christoph.federrath@anu.edu.au) or directly to me- feedback within two weeks after submission

The Gas Dynamics inStar Formation and Turbulence

Image Credit: ESA and the HFI Consortium, IRAS 2010

Christoph FederrathANU – 01 August 2018

Density PDF → Star Formation Rate

Why is star formation so inefficient?

Turbulence → Density PDF

Carina Nebula, NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team (STScI/AURA), and NOAO/AURA/NSF

Turbulence Stars Feedback

Clouds è Cores è Disk + Star + Jet / Outflow

The Star Formation Paradigm

Beuther 2008

Star Formation

Jets and Outflows

Outflow mass:

Outflow velocity:

Outflow angular momentum:

Federrath et al. 2014, ApJ 790, 128

Sink Particles as Star Formation Subgrid Model

Jet/Outflow Feedback

Federrath et al. 2014, ApJ 790, 128Movies available: https://www.mso.anu.edu.au/~chfeder/pubs/outflow_model/outflow_model.html

Federrath – SFDE 2017

NGC1333Image credit: Gutermuth & Porras

Star Formation – Outflow/Jet Feedback

The role of outflow/jet feedback for star cluster formation

SGS off SGS onFederrath et al. 2014, ApJ 790, 128

Movies available: https://www.mso.anu.edu.au/~chfeder/pubs/outflow_model/outflow_model.html

Efficiency~ 30-40%?

Alves et al. (2007); Andre et al (2010)

RESULTS:

- Outflow/Jet feedback reduces the SFR by factor ~ 2

- Outflow/Jet feedback reduces average star mass by factor ~ 3

1/3

The role of outflow/jet feedback for star cluster formation

Why is Star Formation is so Inefficient?

Turb+Mag+Jets

Turb

Turb+Mag

Gravityonly

Movies available: http://www.mso.anu.edu.au/~chfeder/pubs/ineff_sf/ineff_sf.html

Federrath – SFDE 2017

Federrath 2015, MNRAS 450, 4035

Star Formation is Inefficient

Conclusions

� Jet/outflow feedback in star cluster formation:

� Supersonic, magnetized turbulence is key for star formation

- Star formation rate reduced by ~2x- Average star mass reduced by ~3x → Initial Mass Function!

- SFR from density PDF depends onvirial parameter, forcing parameter, Mach number, plasma beta

- Very good agreement between theory, simulations and observations

� Star Formation is inefficient → Only combination of Turb+Mag+Feedback gives realistic SFRs

Image credit: M. S. Povich

Astrophysical Gas Dynamics

ASTR4012 / ASTR8002

NEXT: Hydrodynamical Equations

Astrophysical Fluid Dynamics

(Bai lecture notes)

Derivation of Hydrodynamical Equations

- Introduction of fluid variables

- Conservation of mass, momentum, energy

- Equation of state to close the system

- Validity of the fluid approach

→ White board