Observing galaxies at z = 8.8 — is it worth the effort? | Niels Bohr Institutet | Københavns Universitet Peter Laursen, with Bo Milvang, Jesper Sommer-Larsen, Johan Fynbo & Alex Razoumov

2 ≡ “A galaxy that is bright in Lyα”. Recombination nebulae re-process ~ 1/3 of the raw, ionizing power into a single, narrow ( ~ 1 Å) emission line. Gas accreting in potential wells cools and emit Lyα. LAEs can tell us not only about the first galaxies, but also about the Universe itself (the Epoch of Reionization). Current “record”: z = Lyman α emitters

3 The UltraVISTA survey NIR survey with the 4.1 m VISTA telescope 16 NB118 filters provided by the Dark Cosmology Centre 180 hours of NB observations => Hα emitters at z = 0.8 Hβ and [O III ] emitters at z = 1.4 [OII] emitters at z = 2.2 Lyα emitters at z = 8.8

4 The UltraVISTA survey Legend Stats

5 The UltraVISTA survey Y, J, H, & K ultra- deep imaging NB118 imaging Y, J, H, & K deep imaging HST/ACS imaging

6 Previous predictions Luminosity functions at z = 8.8 Explain the different models Nilsson et al. (2007)

7 Our approach 1. Calculate the number of DM halos in the volume probed by UltraVISTA. 2. Calculate the properties of “galaxies” occupied by those halos. 3. Calculate the observationability of those galaxies.

8 Volume Not all regions are exposed equally long Not all regions are equally sensitive Each of the 16 filters has its own transmission curve Milvang-Jensen+ (2013) First order approximation: A = 1.07 deg 2 dλ = 123 Å  A = 150 h –2 Mpc 2  d = 2 h –1 Mpc  V = 300 h –3 Mpc 3 (physical)

9 Halo mass function

10 Galactic properties Hydro-simulation with on-the-fly ionizing UV RT Resimulations of galaxy-forming regions Post-processing with accurate UV RT Five different implementations of stellar feedback/winds

11 Lyman α radiative transfer Emit Lyα from star-forming and cooling regions.

12 Lyman α radiative transfer Emit Lyα from star-forming and cooling regions. Trace individual photons out to 10 r vir.

13 Lyman α radiative transfer Emit Lyα from star-forming and cooling regions. Trace individual photons out to 10 r vir. Multiply spectrum with e –.

14 Lyman α radiative transfer Emit Lyα from star-forming and cooling regions. Trace individual photons out to 10 r vir. Multiply spectrum with e –. Collect photons in 2” aperture.

15 Lyman α radiative transfer

16 Lyman α luminosity function

17 Best aperture Resonant scattering complicates escape, creating a large halo around the objects. The effective radius is broadened to several arcsec

18 More galactic properties Star formation rates Intrinsic luminosities

19 More galactic properties Star formation rates Intrinsic luminosities Metallicities HI column densities Color excesses

20 More galactic properties Star formation rates Intrinsic luminosities Metallicities HI column densities Color excesses Stellar masses Lyα escape fractions

21 Conclusions Prospects of detecting galaxies at z = 8.8 are dire Standard apertures may be suboptimal