Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1097

Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1097 Lien-Hsuan Lin (林蓮宣 ) Academia Sinica Institute of Astronomy and Astrophysics (ASIAA, Taiwan) Collaborators: Hsiang-Hsu Wang, Pei-Ying Hsieh (ASIAA) Ronald Taam (ASIAA, Northwestern Univ.) Chao-Chin Yang (Lund Observatory) David C.C. Yen (Fu Jen Univ., ASIAA) 1 NGC 1097 [SB(s)b Seyfert 1] Elliptical galaxy NGC 1097A Nuclear starburst ring with a high star formation rate of 3 solar masses per year Dust lanes 2 12CO (J=2-1) intensity maps observed by SMA Hsieh et al. 2008 &2011 3 4 Gas response in different bar models (Athanassoula,1992) Stronger bar The gaseous disk is placed under an external gravitational potential which consists of three components: a stellar bulge, a Kuzmin/Toomre disk, and a Ferrers ellipsoid. 5 Kim et al. 2012 M : fraction of the mass of the bar relative to the spheroidal component R : ratio of the bar semi-major axis to the semi-minor axis 6 Comerón et al. 2010 7 NGC 1300 0.84/16 NGC 1097 1.4/16 NGC 1512 0.8/9.4 8 NGC 4314 NGC 4303 0.8/8.3 0.85/8.5 NGC 6782 2.5/15 9 Our Model for Simulations 10 Governing Equations (i) Equation of continuity V = V0 +V1 +Vg ∂σ dV v(r)2 + ∇⋅(σ v) = 0 0 = rΩ2 (r) = ∂t dr r (ii) Equation of motion V1(R,φ,t) = Ψ(R)cos[2(φ −Ω pt)] ∂(v) ∇P 2 + v⋅∇v = − − ∇V R ∂t σ Ψ(R) = −Ψ0 2 2 2 (A1 + R ) (iii) Equation of state Ψ(R) ∝ R2 as R → 0 2 P = a σ (isothermal gas) Ψ(R) → R−2 as R → ∞ a 1 r A1 ≡ , R ≡ r s r s 2 ∇ Vg = 4π Gσδ (z) 11 Governing Equations (i) Equation of continuity V = V0 +V1 +Vg ∂σ dV v(r)2 + ∇⋅(σ v) = 0 0 = rΩ2 (r) = ∂t dr r (ii) Equation of motion V1(R,φ,t) = Ψ(R)cos[2(φ −Ω pt)] ∂(v) ∇P 2 + v⋅∇v = − − ∇V R ∂t σ Ψ(R) = −Ψ0 2 2 2 (A1 + R ) (iii) Equation of state Ψ(R) ∝ R2 as R → 0 2 P = a σ (isothermal gas) Ψ(R) → R−2 as R → ∞ a r A ≡ 1 , R ≡ 1 r r r s s v(r) v ( ) 2 = 0 B 1−A V 4 G (z) r + r ∇ g = π σδ (Elmegreen & Elmegreen 1990) 12 Governing Equations (i) Equation of continuity V = V0 +V1 +Vg ∂σ dV v(r)2 + ∇⋅(σ v) = 0 0 = rΩ2 (r) = ∂t dr r (ii) Equation of motion V1(R,φ,t) = Ψ(R)cos[2(φ −Ω pt)] ∂(v) ∇P 2 + v⋅∇v = − − ∇V R ∂t σ Ψ(R) = −Ψ0 2 2 2 (A1 + R ) (iii) Equation of state Ψ(R) ∝ R2 as R → 0 2 P = a σ (isothermal gas) Ψ(R) → R−2 as R → ∞ a r A ≡ 1 , R ≡ 1 r r r s s v(r) v ( ) 2 = 0 B 1−A V 4 G (z) r + r ∇ g = π σδ (Elmegreen & Elmegreen 1990) 13 Evolution of the gas disk for NGC 1097 -10 0 10 kpc 14 Comparison between the simulated density distribution and the optical image for NGC 1097 The bright nuclear starburst ring, dust lanes and the prominent spiral arms in the simulation match well with the observations. 15 Comparison between the simulated density distribution and the HI surface density map for NGC 1097 16 Comparison between the central part of the simulated density distribution and 12CO(J=2-1) intensity map for NGC 1097 17 Toomre Q values 18 Comparison between the simulated and observed HI and 12CO(J=2-1) velocity fields for NGC 1097 19 Mass inflow rates slope = 0.11Mʘ/yr Average star formation rate : slope = 0.17 Mʘ/yr 3.1 Mʘ/yr (Hsieh et al. 2011) Accretion rate for the AGN : 0.017 Mʘ/yr (Nemmen et al. 2011) Mass in the starburst ring: Mass in the circumnuclear disk: 11.6 × 108 Mʘ (Sim.) 9.47 × 107 Mʘ (Sim.) 5.8 +/- 0.6 × 108 Mʘ (Hsieh et al. 2008) 6.5 × 107 Mʘ (Hsieh et al. 2008) 20 Summary We have successfully applied our model to NGC 1097 to reproduce most of its observed gas morphology and kinematical features. Based on these results, we have also derived the bar parameters and probed the properties of the rotating bar. In the future, similar studies on more barred spiral galaxies will help us better understand the evolution of the bar parameters. Thank you! 21 .

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