Star Formation in a Barred Spiral Galaxy in Simulations

Shu Horie Takashi Okamoto (Hokkaido University) 1. Introduction

gas surface density ] higher SFE Σ = 2 Σ = SFR surface density pc 1 yr lower SFE Star formation efficiency • 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 [M 1 2 1 ⌃SFR [M yr pc ] SFE [yr ]= ⌃ [M pc 2]

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2 This mechanism is not well [M pc ] Ø log ⌃ 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Perform a simulation of a barred spiral galaxy the star formation criteria used in cosmological simulations Estimate SFE in bar and arm region

Investigate whether the star formation criteria used in cosmological simulations can reproduce the observational result of barred spiral galaxies. 2. Simulation

• Code : GIZMO (Hopkins 2015) • Barred spiral galaxy Øgalactic potentials

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• Mass per a gas particle : ~ 800 M⨀ bar & arm potentials 2. Simulation

• Star formation criteria (Hopkins+ 2013, 2018) • virial parameter � → locally gravitationally bound or not sound speed gas velocity gas particle size

2 2 2 v +(c /h) @v s v 2 = i ↵local = kr ⌦ k ,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 kr ⌦ k @xj

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• � < 1 ⇒ gas is locally gravitationally bound. • � > 1 ⇒ gas is locally gravitationally unbound. 2. Simulation

• Star formation criteria gas particle star particle probability t p =1 exp c ⇤ t

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� < 100 K 3⇡ t = � < 1 cAAACjXichVG7SgNBFL1ZXzE+ErURbIIhIhZhNlEUUQlaaJmHeUCUsDtO4pJ9sTsJxOAPWNpYxEbBQvwBext/wCKfIJYRbCy8u1kQDca77N4zZ+65e2aubKqKzQnp+ISh4ZHRMf94YGJyajoYmpnN20bdoixHDdWwirJkM1XRWY4rXGVF02KSJqusINf2nP1Cg1m2YuiHvGmyY02q6kpFoRJHqkjLK9skRhLlUASTG+F+IHogAl6kjNAjHMEJGEChDhow0IEjVkECG58SiEDARO4YWshZiBR3n8E5BFBbxyqGFRKyNfxWcVXyWB3XTk/bVVP8i4qvhcowRMkLuSdd8kweyCv5/LNXy+3heGlilntaZpaDF/PZj39VGmYOp9+qgZ45VGDD9aqgd9NlnFPQnr5xdtXNbmairSVyS97Q/w3pkCc8gd54p3dplmkP8COjF+fGAjgi8fdA+kE+HhMTsXh6NZLc9YblhwVYhGWcyDok4QBSkHMncQltuBaCwpqwJez0SgWfp5mDHyHsfwECh5HA =0.03 ff

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� = 560 Myr 3. Result Arm

• analysis (KS plot) 1. divide whole region into cells whose size is comparable to observational resolution (250 pc) Bar 2. estimate Σ and Σ in each cell

250 pc • 100 Myr constant SFR (Calzetti+ 2007) M (< 100 Myr) SFR = star

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 100 Myr 3. Result median SFE (Bar) ~ 2×10 yr KS plot median SFE (Arm) ~ 6×10 yr

Bar yr yr . 10 10 = . yr Arm = SFE

] SFE 10 = yr SFE SFE in bar is higher than in arm. 10 = pc SFE . yr 10 = yr SFE yr 10 = ⊙ SFE SF criteria used in cosmological M [ simulations cannot reproduce Σ the observational results.

Need to introduce better models for [ ] Σ M⊙ pc star formation in galaxy simulations 3. Result total gas mass of each density 7.0 . Arm • 10 < � < 10 [cm ] Almost the same gas mass in ] Bar Ø ⊙ 6.0 bar and arm. M . • 10 < � [cm ] 5.0 ØMore gas in bar than in arm.

4.0 log gas mass [ SFR in bar is higher than in arm. 3.0 3.0 4.0 5.0 log H number density [cm] 3. Result

How much cold dense gas is locally self-gravitationally bound

100

M (dense, cold, bound) gas 100 [%] M (dense, cold) AAACdHichVHLSiNBFD1px1GjTqJuhJlFSMggCOG2LhRXQTez9BUNJCF0txWnsF90VwIx6Ae4Fly4GlFE5jPc+AMu8gniUtGNC286AdHgzC2q6tSpe26dqjJ9W4aKqB3TBr4Mfh0aHomPjo1/SyQnJrdCrx5YomB5thcUTSMUtnRFQUlli6IfCMMxbbFt7q109rcbIgil526qpi8qjrHrypq0DMVUNZkoK+mIMKUTHZbK2Uo1maEcRZHqB3oPZPLp8uxxO99c9ZKXKGMHHizU4UDAhWJsw0DIrQQdBJ+5ClrMBYxktC9wgDhr65wlOMNgdo/HXV6VeqzL607NMFJbfIrNPWBlClm6pSt6oBv6S3f08mmtVlSj46XJs9nVCr+aOJreeP6vyuFZ4feb6p+eFWpYjLxK9u5HTOcWVlff2D952Fhaz7Z+0hnds/8/1KZrvoHbeLQu1sT6KeL8AfrH5+4HW3M5fT43t6Zn8svoxjC+I40Zfu8F5PELqyhEf3KKc1zEnrQfWkbLdlO1WE8zhXeh5V4BIimSMw== 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 gas ⇥ Almost all cold dense gas is Arm locally self-gravitationally bound.

Bar � > 1000 cm ⟹ dense 0 � < 100 K ⟹ cold 500 600 � [Myr] � < 1 ⟹ bound 5. Conclusion

• Recent observations of barred spiral galaxies suggest that SFE in bar is lower than in arm. • We perform the simulation to investigate whether the star formation criteria used in cosmological simulations can reproduce the observational results of barred spiral galaxies. • The star formation criteria cannot reproduce the observational results. • Almost all gas which is cold and dense in bar and arm is locally self-gravitationally bound.