1. Barred Galaxies Chang, Seo-Won

2. Contents 1.Overview 2.Vertical structure of bars 3.Rings in SB galaxies 4.Dust lanes in SB galaxies 5.Lop-sidedness in SB galaxies

3. Overview What is the true fraction of Barred Spiral Galaxies? - F(bar) ~ as a function of redshift : understanding galaxy evolution - Difficult to find at intermediate and high redshift (not entirely a selection effect, need a high angular resolution and adequate wavelength band) 2004ApJ_612_191

4. Overview General properties (Bump and peak)

5. Overview Problems 1.Inclination ㅡㅡ ; 2.Bulge component ㅡㅡ ;; -> Athanassoula et al. (1990), “Bulge masking method” -> Fourier coefficient method -> Least Square method

6. Overview ε c N-body simulation

7. Overview Surface brightness profile -> Elmegreen et al. (1985, 1996) = Early–type system= Late–type system

8. Vertical structure of bars We must obtain photometry of edge-on barred galaxies. -> Almost impossible.. ㅜㅡ Numerical simulations, 1.Thin bars seem to be unstable structures which buckle about their midpoints out of the plane of the bar -> thickened double-lobed structure 2.Round-bulge peanut-shaped bulge ~25% edge-on Bulges seem to have boxy or peanut-shaped isophotes. => barred galaxies ~75% => unbarred or barred galaxies

9. Vertical structure of bars However, this evidence is not conclusive. Non-axisymmetric cases, Kuijken & Merrifield(1995).. 1.Orbits followed by material in a barred potential 2.Optical spectra to study the motions of the gas (Doppler shifts) 3. Non-circular orbits

10. Rings in SB galaxies Often contain rings and/or lenses. Buta (1986) - Ringed galaxies based on the UK Schmidt and ESO B Sky Survey films. - Diameters, q, and PA up to the time of this writing (1200 objects up to the time of this writing) - Connection between rings and galactic orbital resonances * SA (nonbarred), SAB( weakly barred), SB (barred)

11. Rings in SB galaxies Observation Gas density distribution model

12. Rings in SB galaxies Results, 1.Inner ring : ~75 % of samples 2.q ≥ 0.9 (SA), q = 0.8 (SB) 3.True major axis of the ring = that of the bar (reproduced by a Model) 4.Outer rings : ~ 50 % of those (almost all in SBs) 5.Slightly less elliptical than inner rings 6.Two alignment modes : perpendicular and parallel 7.Some galaxies have more than one ring -> dynamical pattern? Diameter ratio, width

13. Rings in galaxies Rings are visible in NIR and B-band frame, 1.B-band : young stars (Resonance Hypothesis) 2.NIR : old stars

14. Rings in Early-type galaxy?

17. Many SB gals display characteristic dust lanes. 1. Not quite radially from the ends of the bar 2. Keep toward the side of the bar which leads in the rotation of whole galaxy NGC 1300(SBb) Dust lane in SB galaxies

18. In case of late-type rather than the SBb, 1. Further removed from the principal axis of the bar, and through the less-well-illuminated disk 2. In VERY late-type ones, these may be seen to curve in toward the nucleus, thus partially obscuring the center of the galaxy. -> double peaked core

19. Lop-sidedness in SB galaxies Commonly lopsided. Most clearly seen in the Magellanic-type galaxies (usually have rather egg-shaped bars) and in giant SB systems (NGC4548)

20. Lop-sidedness in SB galaxies NGC4548 in the Hubble atlas (right)

21. Lop-sidedness in SB galaxies Asymmetries in disk galaxies (Richter & Sancisi 1994) Lopsided HI distributions and kinematics usually result in an asymmetry of the global HI profile. 1 2 a b c d