Anna Raiter (ESO) Supervisor: Robert Fosbury (ST-ECF)

1. Observational characteristics of stellar sources of (re)ionizing radiation Anna Raiter (ESO) Supervisor: Robert Fosbury (ST-ECF) In collaboration with Daniel Schaerer (Geneva Observatory) Allahabad 19 February 2010

2. Outline Nebular emission in Case B approximation Photoionization modeling Lyα line Nebular continuum emission He II 1640 Å line other emission lines

3. Nebular emission in case B approximation nr of H ionizing photons L(Lyα) ~ Q(H) * fcoll accounts for 2s2p mixing in H atom (at higher densities) At low density L(2γ) = 0.5(Lyα) L(HeII 1640 Å) ~ Q(He+) • But: depends on the detailed conditions in the gas → electron temperature Synthesis models: low density + constant electron temperature

4. Lyα – equivalent width – case B Depends on the IMF, age, metallicity and SFH of stellar population

5. He II – equivalent width – case B

6. Photoionization modeling • CLOUDY • Input Tbb, U, nH, Zneb • Output: L(Lyα) +EW, L(2γ), L(HeII) +EW and other lines appear in case of Zneb > 0 →to be compared with case B predictions U = Q(H) / 4 π rin2 c nH nebular gas bb

7. L(Lyα) CLOUDY / case B Pop III: 2.2-1.3 => 0 – 50 Myrs Stellar population + nebular physics <E> / 13.6 eV ionizing photons carry energies > 13.6 eV L(Lyα) ~ Q(H) * fcoll *<E>/13.6

8. Stellar population: IMF, metallicity, SFH, age 912 Å 912 Å Schaerer 2003 <E> = 30.033 – 21.657 eV

9. L(HeII 1640 Å) CLOUDY / case B Stellar population + nebular physics High U (0.1) Low U (0.0001) Stasinska-Tylenda effect

10. HeII 1640 Å equivalent width (CLOUDY) Case B prediction • Importance of 2γ continuum: • enhanced like Lyα • can be dominant at 1216-1600 Å • decreases EW of UV emission lines • can produce blue SED slopes • (Bouwens 2010)

11. 2γ continuum Enhanced (~ x 2) 2γ emission Case B hot ionizing source resulting nebular emission

12. Other emission lines: NIV] The Lynx arc (Fosbury et al 2003)

13. Other emission lines: NIV] GDS J033218.92-275302.7 @ z=5.563 GOODS data (Raiter et al 2010)

14. Conclusions Lyα : can be enhanced (especially for hot ionizing stars) – can help to explain high EWs found in some surveys 2γ continuum: enhanced in the same way, changes EWs of UV emission lines He II 1640 Å can be weaker than expected from synthesis models (maybe we need to observe deeper to detect it at high-z) Case B approximation might not be good in case of the nebular emission coming from the gas at high-z It is worth looking for other emission lines at high-z (to distinguish the ionization mechanism and determine the effective temperature of the source)