Tidally induced bars in gas-rich dwarf galaxies orbiting the Milky - PowerPoint PPT Presentation

Introduction The simulations Tidally induced bars in gas-rich dwarf galaxies orbiting the Milky Way Grzegorz Gajda PhD student (last year) at N. Copernicus Astronomical Center (Warsaw, Poland) and Laboratoire d’Astrophysique de Marseille (France) in collaboration with Ewa L. � Lokas (Warsaw) and Lia Athanassoula (Marseille) 5th October 2017 Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 1 / 12

Introduction The simulations Dwarf galaxies in the Local Group A. Z. Colvin, wikipedia.org Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 2 / 12

Introduction The simulations Dwarf galaxies in the Local Group Two type of of dwarf galaxies Dwarf spheroidals Dwarf irregulars ellipsoidal disky gas-poor gas-rich random motions of stars rotating (usually) close to big spirals (usually) far away from big spirals Fornax dSph WLM dIrr ESO/VST/Omegacam Local Group Survey ESO/Digitized Sky Survey 2 Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 2 / 12

Introduction The simulations Dwarf galaxies in the Local Group HI mass-to-light ratio McConnachie (2012) Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 2 / 12

Introduction The simulations Motivation Sagittarius is one of the largest dwarf galaxies, currently very close to the MW Top: distribution of M giants Bottom: stellar surface density from simulation Is it a bar? � Lokas et al. (2010) Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 3 / 12

Introduction The simulations Motivation In the Local Group Hercules: Ursa Major II: Coleman et al. (2007) Mu˜ noz et al. (2010) Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 3 / 12

Introduction The simulations Motivation Beyond the Local Group SDSS Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 3 / 12

Introduction The simulations Simulation setup Dwarf galaxy: 10 9 M ⊙ dark matter halo 2 × 10 7 M ⊙ barionic disc 70% gas fraction Milky Way-like host: 10 12 M ⊙ dark matter halo Three simulations N -body Hydrodynamical without SF Hydrodynamical with SF following the evolution for 10 Gyr using Gadget3 . Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 4 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Simulation overview Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 5 / 12

Introduction The simulations Surface density after the first pericenter stars ⇒ gas ⇒ Gaseous component and star formation weaken the bar compared to the N -body case Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 6 / 12

Introduction The simulations Bar strength after the first pericenter Bars in gas-rich galaxies are less elongated in the centers Gas remains axisymmetric Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 7 / 12

Introduction The simulations Evolution of bar strength Bars form at the first pericenter Weaker for gas-rich dwarfs Disappear over time for gas-rich dwarfs Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 8 / 12

Introduction The simulations Pattern speed Initially, all have almost the same Ω p Later, gas-rich bars are slowed down Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 9 / 12

Introduction The simulations Final apocenter stars ⇒ gas ⇒ N -body model remained barred, while the gas-rich regained axisymmetry Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 10 / 12

Introduction The simulations Star formation Star formation rate is slightly enhanced at the pericenters Overall, SFR drops due to tidal stripping of gas Star formation and SN feedback modelled as in Springel & Hernquist (2003) Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 11 / 12

Introduction The simulations Summary Interaction may drive bar formation in the gas-rich disk galaxies Bars in gas-rich galaxies are weaker more easily destroyed than in N -body case Caveat: we did not include hot gas halo of the Milky Way, thus there was no ram pressure stripping Thank you for your attention! Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 12 / 12

WLM Leaman et al. (2012) M ∗ = 1 . 1 × 10 7 M ⊙ , M gas = 6 . 3 × 10 7 M ⊙ Grzegorz Gajda (Warsaw | Marseille) Tidally induced bars in gas-rich dwarf galaxies 1 / 1