Triggers of bar formation: internal or external? A cosmological - - PowerPoint PPT Presentation

Triggers of bar formation: internal or external?

A cosmological insight

Tommaso Zana

Università degli Studi dell'Insubria

Valletta, 3/10/2017

Collaborators

• M. Dotti, P. R. Capelo, S. Bonoli, F. Haardt, L. Mayer, D. Spinoso

Fraction of bars in massive disc galaxies ( ) ~60 % - NIR ~40 % - optical

(Marinova & Jogee, 2007, Gavazzi et al., 2015)

Bars play a key role in the evolution of disc galaxies

Bars play a key role in the evolution of disc galaxies

where the gas becomes denser

• Triggering bursts of star formation

NGC 6782

Bars play a key role in the evolution of disc galaxies

in the inner disc, once the bursts have depleted the gas

• Triggering bursts of star formation
• Quenching the star formation

NGC 1073

Bars play a key role in the evolution of disc galaxies

if the gas is funneld toward the very inner part of the galaxy

• Triggering bursts of star formation
• Quenching the star formation
• Prompting AGN activity?

NGC 1365

Bars play a key role in the evolution of disc galaxies

dynamically different kind of galactic bulge

• Triggering bursts of star formation
• Quenching the star formation
• Prompting AGN activity?
• Building-up of a pseudo bulge

NGC 1353

What causes a bar?

What causes a bar?

• Secular evolution

What causes a bar?

• Secular evolution
• Tidal Interaction

ErisBH simulation

(Bonoli et al. 2016)

High-resolution cosmological hydrodynamical simulation Milky Way-type galaxy from z = 90 up to z = 0 At z = 0 the galaxy shows a strong bar of about 2 kpc in radius

(Spinoso et al. 2016)

The idea

In ErisBH, the bar growth follows temporally a minor merger at z ~ 1.2

The idea

different evolution of five slightly different initial condition sets:

• 1. ErisBH twin simulation (reduced) - WM
• 2. System deprived of the satellite responsible for the merger - NM

In ErisBH, the bar growth follows temporally a minor merger at z ~ 1.2

The idea

different evolution of five slightly different initial condition sets:

• 1. ErisBH twin simulation (reduced) - WM
• 2. System deprived of the satellite responsible for the merger - NM
• 3. System also deprived of the major fly-by (z > 0.7) - NF

In ErisBH, the bar growth follows temporally a minor merger at z ~ 1.2

The idea

different evolution of five slightly different initial condition sets:

• 1. ErisBH twin simulation (reduced) - WM
• 2. System deprived of the satellite responsible for the merger - NM
• 3. System also deprived of the major fly-by (z > 0.7) - NF
• 4. Fly-by satellite pushed away from the main galaxy - PF
• 5. Dark matter mass of the Fly-by satellite doubled - HF

In ErisBH, the bar growth follows temporally a minor merger at z ~ 1.2

The simulations

• gas, dark matter and star particles
• Spatial resolution
• Mass resolution
• Cooling and SN feedback

The simulations

• gas, dark matter and star particles
• Spatial resolution
• Mass resolution
• Cooling and SN feedback

ChaNGa (Menon et al., 2015)

• treeSPH-code built on the SPH code Gasoline (Wadsley et al., 2004)

and implemented with the Charm++ libraries

The code

With the merger Stellar density Gas density Without the merger

5 kpc

Without the fly-by

The simulations

With the merger Stellar density Gas density Without the merger

5 kpc

Without the fly-by

The simulations

With the merger Stellar density Gas density Without the merger

5 kpc

Without the fly-by

The simulations

With the merger Stellar density Gas density Without the merger

5 kpc

Without the fly-by

The simulations

Fourier decomposition

Z = 1.20 Z = 0.30 Z = 0

Fourier decomposition

Fourier decomposition

Fourier decomposition

Fourier decomposition

Fourier decomposition

X-shaped bulge emergence

WM NM NF HF With the merger Without the merger Heavier fly-by Without the fly-by

Conclusions

• The origin of the bar forming in ErisBH run is not linked to any

particular tidal event As long as the galactic potential is prone to bar instability, a bar develops independently of any interaction

• It seems that the fly-by could delay the growth of a bar

Gravitational perturbers inhibit the bar formation process Zana et al. 2017 (In press)