Pushing FORS to the Limit—A New Population of Faint Extended Lyα Emitters at z˜3

Haehnelt, Martin G.; Rauch, Michael; Bunker, Andrew; Becker, George; Marleau, Francine; Graham, James; Cristiani, Stefano; Jarvis, Matt J.; Lacey, Cedric; Morris, Simon; Peroux, Celine; Rottgering, Huub; Theuns, Tom

Abstract

We present here the results of an ambitious attempt to push searches for spatially extended emission from damped Lyα absorption sustems (DLAS) and Lyman limit systems (LLS) to fainter surface brightness limits with observations performed in service mode in periods of bad seeing. For this purpose we have initiated a program of long-slit spectroscopy with FORS2 at the VLT to search for extended Lyα emission in a mostly blank field (LP 173.A-0440). Because of the small volume covered this is not a viable solution for a search for objects as rare as Lyman break galaxies, which are hard to hit with a single randomly positioned slit, but the rate of incidence of LLS with neutral hydrogen column densities exceeding (N(HI)>1019 cm−2) per unit redshift is approximately unity at redshift ∼3 i.e., the objects essentially cover the sky, and there should be numerous hits in a single setting for a typical long slit spectrograph. A major motivation for our deep spectroscopic search was thereby the prospect of reaching sufficiently low surface brightness levels to detect or place interesting upper limits on the the fluorescent Lyα emission from optically thick regions induced by the metagalactic ionizing UV background 1,2. The project resulted in (after overheads) 92 hours of on-source exposure, finally reaching a 1σ surface brightness detection threshold of 8×10−20 erg cm−2 s−1 □′′−1. The results presented here will be published in detail as Rauch et al. [Astrophys. J., in press, arXiv:0711.1354 (2007)].

Citation

Haehnelt, M. G., Rauch, M., Bunker, A., Becker, G., Marleau, F., Graham, J., Cristiani, S., Jarvis, M. J., Lacey, C., Morris, S., Peroux, C., Rottgering, H., & Theuns, T. (2009, December). Pushing FORS to the Limit—A New Population of Faint Extended Lyα Emitters at z˜3. Presented at ESO Workshop 'Science with the VLT in the ELT era'

• Presentation Conference Type: Conference Paper (published)
• Conference Name: ESO Workshop 'Science with the VLT in the ELT era'
• Publication Date: 2009
• Deposit Date: Feb 16, 2012
• Publisher: Springer Verlag
• Pages: 23-26
• Series Title: Astrophysics and Space Science Proceedings
• Book Title: Science with the VLT in the ELT Era
• ISBN: 9781402091896
• DOI: https://doi.org/10.1007/978-1-4020-9190-2_3
• Public URL: https://durham-repository.worktribe.com/output/1157781