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Complex Ly a Profiles in z=6.6 Ultraluminous Ly a Emitters

Complex Ly a Profiles in z=6.6 Ultraluminous Ly a Emitters. Amy Barger E. Hu, A. Songaila, L. Cowie, G. Hasinger, B. Rosenwasser, C. Waters. Multi-Component Ly a Profiles at Low z.

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Complex Ly a Profiles in z=6.6 Ultraluminous Ly a Emitters

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  1. Complex Lya Profiles in z=6.6 Ultraluminous Lya Emitters Amy Barger E. Hu, A. Songaila, L. Cowie, G. Hasinger, B. Rosenwasser, C. Waters

  2. Multi-Component Lya Profiles at Low z • At low z, where LAEs are not expected to be strongly affected by IGM opacity, a variety of profiles are observed (see also Kulas+12): • multi-component profiles • red tails and sharp blue-side cutoffs (so this type of profile can arise even without IGM scattering) Yamada+12 Scarlata+18 Scarlata+18 • These features are a consequence of Lya scattering in the galaxy itself • At low z, ~30-50% of LAEs are found to have a blue wing

  3. Multi-Component Profiles at High z? • In contrast, at z~6.6, the blue wing is expected to be removed by scattering from intergalactic HI • Indeed, this is observed for nearly all z~6.6 LAEs with Lya luminosities <1043.5 erg/s • However, the most luminous LAEs may be able to ionize a sufficiently large HII region around them to enable the full Lya profile of the galaxy to get out • If so, and if the underlying galaxy properties are similar at high z to those at low z, then one might find multi-component profiles to be a common feature Hubble Deep Field-Proper

  4. Science Goal • Our goal is to develop a substantial sample (several 10s) of ultraluminous LAEs with Lya luminosities >1043.5 erg/s and see whether any of them show complex profiles • Ultimately, we would like to find whether there is a characteristic Lya luminosity above which one sees the intrinsic galaxy profile Hubble Deep Field-Proper

  5. HEROES Survey of the North Ecliptic Pole (NEP) to search for ultraluminous LAEs • A planned 120 deg2 area NB921 survey using the 1.5 deg diameter Hyper Suprime-Cam (HSC), with 55 deg2 so far (most uniform area is 30 deg2) • The 1s noise in a 2’’ diameter aperture ranges from 25.4 to 26.1 • Also includes g’, r’, i’, z’, y’, and NB816 images from HSC, and U and J from MegaPrime/MegaCam and WIRCam on CFHT • In z’, the 1s noise in a 2’’ diameter aperture ranges from 26.2 to 27.0 Blue circle: area of current observations Red circle: area of full HEROES survey There are other examples of ultraluminous LAEs in, e.g., Ouchi+09, Matthee+15, Konno+18, Sobral+18, but our sample has uniform Keck/DEIMOS spectroscopic followup Close-packed stepping pattern of 1 deg offsets and the N-Shot mosaic pattern with NDITH = 5

  6. LAE Candidate Selection 5 - 9s selection criterion throughout the area Candidate LAEs at z=6.6, if also not detected above 2s in any of the g’, r’, and i’ bands 2.8 million sources on figure!

  7. Spectroscopic Follow-up with Keck/DEIMOS of ultraluminous LAE candidates (prioritize z’ detections) NEP COSMOS 5 spectroscopically confirmed LAEs (red) 1 high-z AGN (gold) 1 [OIII] emitter (blue) 3 spectroscopically confirmed LAEs (red) (2 were previously confirmed by Sobral+15) Rectangle: uniform 30 deg2 area used here Shaded area: 3 deg2 field of Hu+16 Rectangle: smaller area of Sobral+15

  8. AGN Contamination • NB surveys pick up AGN, so this is a source of contamination in photometric samples • 1/7 of our NEP ultraluminous LAE candidates is a broad-line AGN • NEP chosen to match deepest areas of eROSITA to look for high-z AGN (Merloni et al. 2012) • Note: the other LAEs do not show NV in the optical and also do not show CIV in the NIR (or HeII)

  9. COSMOS Ultraluminous LAEs Blue wing Broader Secondary red component Lya profiles (black) are compared with the composite profile of 31 lower luminosity LAEs from Hu+10 (red; normalized to the peak flux in each spectrum)

  10. NEP Ultraluminous LAEs

  11. Concern: small doublet separation in [OII] may produce spectra that look like complex Lya profiles However, [OII] emitters are generally fairly easily seen in the g-band, while LAEs, including COLA1 and NEPLA4, are much fainter (i.e., undetected) NB921, z’, r’ g’,r,i’ Only [OIII] emitters contain any sources that satisfy our LAE selection z’ – NB > 1.3 (these will contaminate a photometrically selected sample)

  12. Moreover, for NEPLA4, the velocity separation between the blue wing and the peak is larger than the [OII] doublet separation • It also has a strong red tail

  13. Summary • The most ultraluminous LAEs (Lya luminosities >1043.5 erg/s) at z~6.6 also seem to show a range of profiles, including ones with complex profiles • Numbers are small currently, but the complex profile fraction seems similar to that at low z (~30%) • Thus, we may be able to determine the characteristic Lya luminosity where the bubbles are both large enough and ionized enough for us to see the intrinsic galaxy profile • This could perhaps let us estimate the ionizing escape from the LAE galaxy Hubble Deep Field-Proper

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