Gas stripping: mass-loss rates in galaxy clusters Pavel JÁCHYM, Jan PALOUŠ, Joachim KÖPPEN, and Françoise COMBES Prague

ViennaSatP.Jáchym et al.: Gas stripping2 Content of the talk Ram pressure stripping Our simulations examples Current analytic description Detailed study of the stripping event Simulations results Conclusions

ViennaSatP.Jáchym et al.: Gas stripping3 Ram pressure stripping Interaction of ISM of galaxies with ICM in clusters and groups of galaxies Butcher-Oemler effect morphological segregation HI deficient galaxies Source of metals in ICM ICM distribution: ß-profile Pressure of the encountered ICM vs. gravitational restoring force

ViennaSatP.Jáchym et al.: Gas stripping4 Numerical simulations I 3D tree/SPH calculations (GADGET) face-on galactic configuration radial orbits: free-fall from the cluster periphery, half of the orbital period 3-component (disk/bulge/halo) galaxy: –Miyamoto-Nagai disk (stellar and isothermal gaseous) –Plummer bulge & DM halo Standard model (corresponding to M87 Virgo subclump): –ß ICM = 0.5, ρ 0 = 4·10 -3 cm -3, r c = 13.4 kpc –ß DM = 1, ρ 0 = cm -3, r c = 320 kpc

ViennaSatP.Jáchym et al.: Gas stripping5 Numerical simulations II model galaxy: initial situation:

ViennaSatP.Jáchym et al.: Gas stripping6 example of a stripping event

ViennaSatP.Jáchym et al.: Gas stripping7 Gunn & Gott’s approach Gunn & Gott (1972), analytic description Face-on orientation of galaxy G&G criterion - ram pressure exceeds the restoring force: Thus, decisive factors of a stripping event: –value of the maximum ICM density ρ max –maximum orbital speed of the galaxy υ max –mass distribution in galaxy (the restoring force)

ViennaSatP.Jáchym et al.: Gas stripping8 Gunn & Gott’s assumptions Then: –galaxies of one cluster at orbits with different maximum ICM density ρ max should experience different stripping –& galaxies of one cluster at various orbits with constant ρ max value should show the same amount of stripping Alternatively: –galaxies at constant orbits in clusters with different ρ 0 values should be unequally stripped –& galaxies at constant orbits through equally peaked but variously wide clusters should be equally stripped

ViennaSatP.Jáchym et al.: Gas stripping9 Numerical simulations – different ρ 0 ‘s simulations with ρ 0 = 4·10 -3 cm , 0.5, 2, and 4 multiples of r c = 13.4 kpc

ViennaSatP.Jáchym et al.: Gas stripping10 Numerical simulations – different r c ‘s simulations with r c = 13.4 kpc , 0.5, 2, and 4 multiples of ρ 0 = 4·10 -3 cm -3

ViennaSatP.Jáchym et al.: Gas stripping11 Gunn & Gott’s constraints no regards to the facts that: –orbital trajectories of galaxies through clusters differ –galactic restoring force is f(z) –ISM disks accumulate the encountered ICM –the restoring force is further f(t) –shifted ISM can be re-accreted

ViennaSatP.Jáchym et al.: Gas stripping12 What’s really happening? Equation of motion (EOM) of a disk element ΔA located at a galactic radius r: where υ gal... orbital speed of the galaxy υ el... speed of the element with respect to the disk plane Φ... galactic potential Σ el... surface density of the element ΔA.

ViennaSatP.Jáchym et al.: Gas stripping13 EOM solution I element shifts out of the disk plane –it encounters less ICM –it has lower velocity and thus lower ram pressure –local value of the escape velocity model galaxy: –Miyamoto-Nagai disk potential Φ d –Plummer bulge and halo potentials Φ b, Φ h stripping criterion: υ el > υ esc

ViennaSatP.Jáchym et al.: Gas stripping14 EOM solution II A stripped element

ViennaSatP.Jáchym et al.: Gas stripping15 EOM solution III A kept element

ViennaSatP.Jáchym et al.: Gas stripping16 EOM solution IV element at radius r = 8kpc EOM Gunn & Gott no criterion

ViennaSatP.Jáchym et al.: Gas stripping17 EOM solution V Gunn & Gott’s predictions (dashed) compared to analytic results (solid) for various ρ 0, r c

ViennaSatP.Jáchym et al.: Gas stripping18 Simulation results r c = 0.25 r c = 1 r c = 4 ρ 0 = 0.25 ρ 0 = 2 ρ 0 = 4

ViennaSatP.Jáchym et al.: Gas stripping19 Simulation results stripping mass M strip : stripping radius R strip : (of 16kpc) ρ 0 R c 1/414 99%95%78% 191%70%37% 473%40%14% ρ 0 R c 1/

ViennaSatP.Jáchym et al.: Gas stripping20 Different galaxies various galactic types – different profiles of the restoring force => different amount of stripping LMLmEMEm disk:MdMd M sol adad kpc4466 bulge:MbMb M sol abab kpc halo:MhMh M sol ahah kpc20 25

ViennaSatP.Jáchym et al.: Gas stripping21 Different galaxies LM,Lm EM,Em following the GG, one should obtain vertical growth of the stripping level that is constant for a given central density

ViennaSatP.Jáchym et al.: Gas stripping22 Current conclusions We study in detail the process of stripping : Gunn & Gott’s criterion –strongly overestimates stripping results –doesn’t work at all for narrow clusters Decisive factors of the ram pressure stripping event: –orbital history of the galaxy mass accumulation duration of the ICM-ISM interaction

ViennaSatP.Jáchym et al.: Gas stripping23 Further conclusions We are looking for a “new stripping criterion” that would employ observable quantities...