view the Intergalactic Medium The Milky Way s HI Clouds in the Halo of our Galaxy Gerhard Hensler Galaxies Gas Environment Infall Outflow Stripping

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Galaxies and their Interaction with the Intergalactic Medium Galaxies Gas Environment Infall Outflow Stripping Gerhard Hensler Institute of Astronomy University Observ.

1 Galaxies and their Interaction with the Intergalactic Medium Galaxies Gas Environment Infall Outflow Stripping Gerhard Hensler Institute of Astronomy University Observ. Observ. of Vienna The Spiral Galaxies view Reminder: Our own Milky Way is a typical spiral galaxy with characteristics: gaseous and stellar Disk with Spiral Arms, central Bulge, old spherical stellar Halo NGC 891 The Milky Way s view NIR: old cool stars: flat disk, centrally concentrated; Sun not in the galactic center; central peanut-shaped Bulge CO: molecular gas: very flat, central disk; northern extentions; single structures (clouds) in the outermost regions 21cm: dense flat HI gaseous disk; diffuse fraying structures M 73 HI Clouds in the Halo of our Galaxy

2 Infalling HI Gas; the Milky Way is : HVCs Infalling Gas stems partly from the tidal disruption of satellite galaxies. Gas bridges between the Magellanic Clouds and the Milky Way s Disk The M81 Group Gas Infall triggers M82 SB Model parameters: Model: R cl = 1 kpc V cl = 10 km/s T cl = 5000 K M cl depending on length here: z = 6 kpc Cloud Infall chemo-dynamical Simulation Hirche 2003 Infalling cloud enhances SF without hitting the disk. Hot gas outflow decelerates infall.

Hot Gas is expelled from Galaxies into the Halo The turbulent Milky Way Observations (round view) in different wavelength ranges reveal dynamical structures: H-alpha: ionized gas patchy, but

3 Hot Gas is expelled from Galaxies into the Halo The turbulent Milky Way Observations (round view) in different wavelength ranges reveal dynamical structures: H-alpha: ionized gas patchy, but diffusely extended FIR: produced by warm dust; thick disk with diffuse filaments : a starburst galaxy Supernova Remnants massive Stars (> M ) explode as Supernovae (typeii); Most of their mass is ejected at high energies (1051 ergs) in fastly expanding bubbles; Hitting an inhomogeneous environment, shock fronts and clumps form; Shock fronts radiate in collisionally excited em. lines, the bubble s interior cools by X-ray emission Vela Supernova Remnant Radio at 6cm: n-thermal radiation of hot gas (magnetic field) within the disk: spots stem from Supernova Bubbles; Loops and filaments indicate gaseous outflows. Superbubbles HII-Region W4 Cumulative Stellar Winds + Explosions in Stellar Associations form Superbubbles of hot Gas Superbubbles expand out of the gaseous disk and feed a hot gaseous halo

Superbubble Models Magnetic Fields in Galaxies Stars are born in associations. Massive stars have short lifetimes (few Mio. years). Sequential supernova explos.s form huge hot gas Bubbles.

4 Superbubble Models Magnetic Fields in Galaxies Stars are born in associations. Massive stars have short lifetimes (few Mio. years). Sequential supernova explos.s form huge hot gas Bubbles. Superbubbles expand out of a Galaxy. Mass loading due to cloud evaporation. Supernova gas is metal rich. Galaxies are losing metals. Vehement expansion leads to froth of ionization stages. T and Z determinations diffic. X-ray gas in our Milky Way (RASS) Magn. fields parallel to the gal. plane are bent vertically due to superbubble s overpressure and open to the halo; CR diffusion facilitates galactic winds Breitschwerdt et al Dwarf Galaxies (low masses) can expel all their Gas into the Intergalactic Space. Gas is stripped off by tidal and dynamical drag leading to des and dsphs. Sculptur (Carignan 1996) bright spots: hot bubbles red: soft ( kev) blue: hard ( kev) light blue: middle ( kev) Leo A

The Virgo Cluster X-ray Gas in Galaxy Clusters Virgo Coma ellipticals: M86 M84 M87 spirals: D = 16.8 Mpc T 10 7 K n 10-4... -3 cm -3 Z 0.2... 0.4 Z Galactic disks within a hot ICM: evaporation?

5 The Virgo Cluster X-ray Gas in Galaxy Clusters Virgo Coma ellipticals: M86 M84 M87 spirals: D = 16.8 Mpc T 10 7 K n cm -3 Z Z Galactic disks within a hot ICM: evaporation? Galaxies on their passage through the ICM Cowie & Songaila Preliminary conclusions: (thin) Galactic disks cannot form in a hot ICM environment. Is their a cluster galaxy population that reflects the formation epoch? Galactic disks should be evaporated within 1-10 Gyrs. Present spiral clusters galaxies are formed in the field and falling into the grav. potential. But! Does evaporation act as in analytical approaches? B Hα e.g. NGC 4522 (Kenney & Koopmann, 1999)

6 τ λ λ NGC 4569 flies through the Virgo Cluster ICM R image of NGC 4569 X-ray contours of the Virgo Cluster (Boselli, private) (Schindler et al., 1999) Hydrodynamic al Simulations Model parameters: T ICM = 5x10 7 K Ma = 0.7, 1.5 n ICM = 10-3 cm -3 M ISM = 10 9 M M disk = M s = 133 pc Self gravitation and cooling let clumps grow and stabilize. Aims: How does the stripped material evolve? Additional effect of heat conduction (and radiation)? (Schumacher 2003) Relative motion of gaseous galaxies in the cluster gas leads to ram-pressure stripping Gas outflows: e.g. NGC 4569 (Tschöke, G.H., Junkes 2001) Ram pressure: Bindingenergy density: kick off timescale: p e ram grav = ρ = ρ esc v Gyrs v ISM esc v 2 ICM v 2 rot 1cm n -3 v km/s v How to treat RPS dynamically? esc mean free path of electrons : mean free path within HI gas : e HI 6 2 (T/10 K) 3 ( n /10 cm ( n /1 cm 3 3 pc ) pc ) R contours over Hα (soft) X-ray contours over Hα Hydrodynamical treatment requires multi-scale description!

7 Conclusions Galaxies intimately coupled to their environm. Interstellar and Intergalactic Media are at extreme plasma states. Astrophysical Objects are ideal Laboratories of Plasmaphysics. IS clouds Galact. wind

Chapter 15.3 Galaxy Evolution

Chapter 15.3 Galaxy Evolution Elliptical Galaxies Spiral Galaxies Irregular Galaxies Are there any connections between the three types of galaxies? How do galaxies form? How do galaxies evolve? P.S. You