SLIDE 1
Tie (chemo)-dynamics
- f gas accretion
- nto star-forming galaxies
Tie (chemo)-dynamics of gas accretion onto star-forming galaxies - - PowerPoint PPT Presentation
Tie (chemo)-dynamics of gas accretion onto star-forming galaxies - - PowerPoint PPT Presentation
Tie (chemo)-dynamics of gas accretion onto star-forming galaxies Gabriele Pezzulli (ETH Zurich) Filippo Fraternali (Bologna; Groningen) James Binney (Oxford) The role of gas in galaxy dynamics Valletta, 4 October 2017 Accretion on
SLIDE 2
SLIDE 3
Modes of gas accretion
Condensation above the disc Directly available to star formation Fueling outer discs Radial fmows within the disc to fuel SF What dominant mode for star-forming galaxies at low z? COLD MODE
DISC CORONA
HOT MODE
DISC
Filament Filament
SLIDE 4
Indications from observations
M33
Zheng + 17a Ionized infmow Ho+17 MgII “corotating” absorptions @ R ~ 0.4 Rvir
DISC
Filament Filament
DISC CORONA
? ?
SLIDE 5
Chemo-dynamical approach
Data: disc structure, metallicity gradients, kinematics. “easy” (easier) Modeling: Chemo-dynamics: much more diffjcult?
(Fe
α-elements ISM
(Stars
Time-delay efgects) Multiple populations, migration.)
Star formation (source) Accretion (dilution) Normalized abundance Linear equation Closed-form solution GP & Fraternali (2016)
Schönrich & Binney (2009)
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Purely vertical accretion
DISC
“Independent annuli” TIME Spatially resolved → surface densities Abundance gradient
SLIDE 7
Purely vertical accretion
DISC
“Independent annuli”
MW obs gradient Genovali et al. (2015) Ways out, tuning:
- accretion time-scales
- star formation effjciencies
- .
Spatially resolved → surface densities Abundance gradient
SLIDE 8
Purely radial accretion
DISC Filament Filament
RADIAL MASS FLUX RADIAL VELOCITY
Incoming fmow Gradual consumption (star formation)
SLIDE 9
Purely radial accretion
Edmunds & Greenhow (1995) GP & Fraternali (2016)
DISC Filament Filament
Along gas trajectories (Method of characteristics) RADIAL VELOCITY Abundance gradient
SLIDE 10
Is the truth in the middle?
SLIDE 11
Dynamics of gas accretion
To the stars? (spiral structure; bar interactions) To the gas itself? (viscosity? violent disc instability?) To the dark matter?
- Purely radial accretion -
Who to transfer the angular momentum to?
DISC Filament F i l a m e n t
SLIDE 12
DISC INNER CORONA
Dynamics of gas accretion
- Purely vertical accretion -
ONLY IF
Cold disc Pressure negligible Hot corona rotation + pressure
SLIDE 13
Dynamics of gas accretion
Vertical accretion + radial fmows!
Cold disc Pressure negligible Hot corona rotation + pressure
DISC INNER CORONA
Radial fmows
e.g. Pitts & Tayler (1989) Bilitewski & Schönrich (2012)
Dynamically coupled fmows! One parameter: AM mismatch (due to )
GP & Fraternali (2016)
Solved with “method of characteristics”
SLIDE 14
Hot-mode accretion with radial fmows
GP & Fraternali (2016) Bilitewski & Schönrich (2012) Model requirement First direct observation (Hodges-Kluck, Miller & Bregman 2016)
SLIDE 15
A hydrodynamical cosmological model
Angular momentum distribution (AMD)
From Cosmology (tidal torques)
Rotating equilibrium
GP, Fraternali & Binney (2017) Required velocity matched with minimal assumptions and cosmological AMD
SLIDE 16
Summary
Chemo-dynamics is.
- “not so diffjcult”
- sensitive to the mode of accretion