Gas in GRB hosts Yuri Shchekinov Southern Federal University Many faces, SAO, Nizhny Arkhyz, Oct

H2 in GRB hosts No vr excited H2 is seen in any of 5 GRB environment Tumlinson etal 2008 More effective H2 destruction in GRB hosts than in LMC/SMC ? GRB itself photodissociates only its parent molecular cloud ??

H2 absorption in optical GRB afterglows

H2 destruction by a GRB progenitor HII H2 Evacuated dust 10 of 25 M_sun cluster 10 of 40 M_sun cluster 5/ccm 10/ccm

H2 destruction ob larger scales GRB HI → HII H2 → HI ~50 pc

Two-phase ISM in GRB hosts T cooling rate (erg cm3/s) Metals always provide radiative cooling →

Two-phase ISM in GRB hosts Metals always provide radiative cooling → temperature distribution after a merging Temperature, K Mass contained, g

Two-phase ISM in GRB hosts Mean density → Burkert profile n ~ M_sun M () 1/3 /ccm

H2 formation Primordial gas H+e → H → H +H → H2 +e inefficient -- Metal enriched gas H+H+dust surface → H2 + dust surface able to convert all HI in H2

H2 formation on dust surface Depletion on dust surface Dust is present !

H2 formation on dust surface t H2 ~ Z(solar) Z n Gyr

H2 formation on dust & photodestruction

H2 collisional destruction Dark matter haloes mergers → overall heating, dispersal of gas, destruction of clouds

Metal absorption in long-GRB Mg absorptions in GRBs are 3 times more frequent than in QSOs absorptions Savaglio etal 2003, 2006 Extended (upto 30 — 50 kpc) enriched haloes

Patchy distribution of metals in MW Luck etal 2006 [Z] in Solar vicinity Bochkarev etal 2009: t_mix ≥ 1 Gyr L ~ 2 kpc

Patchy distribution of metals in MW Bochkarev etal 2009 Cyg X-1 − α Cam

Metal mixing in merging events

Metal distribution in merging events

GRB luminosity vs redshift (Beskin etal)

What I would like to conclude The ISM in GRB hosts is well-mixed and 2-phase  H2 molecules are to form efficiently  but are not seen in GRB absorptions because are destroyed collisionally in merging events As (if) metals are well-mixed in galactic ISM mergers have to be frequent (<< Gyr) z-growing peak luminosity in optical post-GRB (Beskin etal, thursday) supports this conclusion

H2 formation on dust surface

Pironello etal 1999, … Shematovich & Tsvetkov 2000 Z=2Z=4