The gaseous halos of spiral galaxies

1. The gaseous halos of spiral galaxies Filippo Fraternali1 James Binney1 Rense Boomsma2 Tom Oosterloo3 Renzo Sancisi2,4 1 Theoretical Physics - University of Oxford (UK) 2 Kapteyn Astronomical Institute (NL) 3 ASTRON - Dwingeloo (NL) 4 INAF - Osservatorio di Bologna (I)

2. Inflow and outflow processes Gas out-flow Galactic fountain(Shapiro & Field 1976) - Winds, SN explosions - Gas circulation 2. Accretion from the IGM - Companions - minor mergers (Sancisi & Van der Hulst 1988) - Primordial gas (Oort 1970) Thin disk Cold gas infall Gas accretion Thin disk  Study of the extra-planar (halo) gas

3. Outline HI observations: edge-on: NGC891 slow rotation non-edge-on: NGC2403 slow rotation + inflow other galaxies Dynamical model: model description application to NGC891 and NGC2403

4. NGC 891 . Distance: 9.5 Mpc . Type: Sb/SBb . Inclination ~ 90o . LB = 8 x 1010 LO . Non-interacting . Very similar to the Milky Way

5. The gaseous halo of NGC891 Total HI maps WSRT 10 kpc Oosterloo, Fraternali & Sancisi 2005 Sancisi & Allen 1979 Swaters et al. 1997

6. Extra-planar gas in NGC 891 • Sancisi & Allen 1979 NH ≈ 5 1020 cm-2 • Swaters et al. 1997 NH ≈ 7 1019 cm-2 • Oosterloo et al. 2005 NH ≈ 1.7 1019 cm-2 • Sancisi & Allen 1979 NH ≈ 5 1020 cm-2 • Swaters et al. 1997 NH ≈ 7 1019 cm-2 • Oosterloo et al. 2005 NH ≈ 1.7 1019 cm-2 • Sancisi & Allen 1979 NH ≈ 5 1020 cm-2 • Swaters et al. 1997 NH ≈ 7 1019 cm-2 • Oosterloo et al. 2005 NH ≈ 1.7 1019 cm-2 200+ hours at the WSRT

7. NGC891: data cube

8. vrot~15 km s-1 kpc-1 NGC891: Low rotation of extra-planar gas Fraternali 2005 See also poster by G. Heald et al.

9. NGC 2403 .Distance: 3 Mpc .Type: Sc .Inclination ~ 62 .Non-interacting .Very similar to M33

10. Thin disc model Extra-planar gas in non–edge-on galaxies NGC2403: total HI map Velocity field Fraternali, van Moorsel, Sancisi, Oosterloo, AJ, 2002

11. Thin disc model NGC2403: Extra-planar gas Forbidden gas 130 km/s Extra-planar gas Fraternali, Oosterloo, Sancisi, van Moorsel 2001

12. 5 kpc 8 kpc 107Moof H I Extra-planar gas and accretion NGC2403

13. Thin disc Lagging halo V NGC2403: Non circular motions Thin disc Extra-planar gas

14. Non-circular motions

15. Summary (observations) • Extra-planar detected up to 15 kpc from plane • Rotation lower than the disc • Global inflow motion • High velocities (100-200 km s-1) • Link with star formation? • Evidence for accretion?

16. How common is halo gas? • Halo gas (HI) found and studied in 7 galaxies: NGC891, N2403, N6946, N253 (Boomsma et al. 2005), N4559 (Barbieri et al. 2005), UGC7321 (Matthews & Wood 2003), NGC2613 (Irwin & Chaves 2003).

17. NGC6946: Extra-planar gas and SF WRST Boomsma PhD 2005

18. How common is halo gas? • Halo gas (HI) found and studied in 7 galaxies: NGC891, N2403, N6946, N253 (Boomsma et al. 2005), N4559 (Barbieri et al. 2005), UGC7321 (Matthews & Wood 2003), NGC2613 (Irwin & Chaves 2003). • Hints of halo gas (HI) in other galaxies: NGC 5055 (Battaglia et al. 2005) M33 (van der Hulst, private) UGC 1281 (P. Kamphuis, PhD) UGC 12632 (new WSRT observations) HVCs in Milky Way (Wakker et al.) HVCs in M83 and M51 (Miller & Bregman 2005) HVCs in M31 (R. Braun et al.) • Ionised gas found and studied in several galaxies (e.g. Rand)  Origin: fountain and/or accretion?

19. Dynamical models Previous works: • A barotropic [p=p(r)] fluid in a gravitational field corotates (Poincaré, 1893) • Hydrostatic models for non-barotropic fluid show gradient in rotation velocity but also high temperatures (Barnabé, Ciotti, Fraternali, Sancisi, A&A, submitted) • Galactic fountain: gas circulation (disc-halo-disc) (Shapiro & Field, ApJ 1976; Bregman, ApJ 1980) • Ballistic models: disagreement between predicted gradient in rotation velocity and H data (Collins, Benjamin & Rand, A&A 2002)

20. Dynamical model • Continuous flow of particles from the disc to the halo • Initial conditions: distribution of kick velocities • Potential: exponential discs + bulge + DM halo • Integration in the (R,z) plane, then distribution along  • At each dt projection along the line of sight • Stop at the first or second passage through the disc • Pseudo-cube to be compared with HI data cube

21. Model constraint: vertical distribution Vkick ~ 75 km s-1 Mhalo ~2 109 M

22. N891: inflow/outflow Travel times Energy input <4 % of energy from SNe

23. NGC891: Lack of low angular momentum Fast rotating gas NEED FOR LOW ANGULAR MOMENTUM MATERIAL

24. Thick disc 60o Thin disc NGC2403: lagging gas Vkick ~ 70 km s-1 Mhalo ~ 5 108 M

25. Thin disc gas Extra-planar gas V VR Vz NGC2403: inflow/outflow Radial outflow NEED FOR INFALLING MATERIAL

26. Second-passage models V VR Vz V VR Vz

27. Summary (models) • Models reproduce the vertical extent with reasonable energy input (<4 % SN energy) • Failure in NGC891: lack of low angular momentum  Need for interactions or accretion • Failure in NGC2403: lack of inflow  Need for accretion

28. High Velocity Clouds Forbidden gas v 100 km s-1 M  5 · 106 MO Complex C v 100 km s-1 If d  10 kpc M  107 MO Complex A M  106 MO d  8-10 kpc v 100 km s-1 Filament v 80 km s-1 M  107 MO Low metallicity Z=0.1-0.3 solar (Tripp et at. 2003) Wakker et al. 2003; Wakker & Van Woerden 1997

29. Conclusions • Extra-planar gas: maybe common up to 10-15 kpc from the plane • Kinematics: Low rotation (gradient) + vertical motions (up to 100-200 km/s) + overall inflow • Dynamical models: galactic fountains alone do not reproduce the kinematics of the extra-planar gas and require accretion from IGM Evolution of spiral galaxies influenced both by: - Star formation (gas to the halo, to the outer parts...) - Accretion of cold material