Narrow-band surveys for very high redshift Lyman-$\mathsf{\alpha}$ emitters

Abstract

Context. Many current and future surveys aim to detect the highest redshift (z > ∼ 7) sources through their Lyman-α (Lyα) emission, using the narrow-band imaging method. However, to date the surveys have only yielded non-detections and upper limits as no survey has reached the necessary combination of depth and area to detect these very young star forming galaxies. Aims. We aim to calculate model luminosity functions and mock surveys of Lyα emitters at z > ∼ 7 based on a variety of approaches calibrated and tested on observational data at lower redshifts. Methods. We calculate model luminosity functions at different redshifts based on three different approaches: a semi-analytical model based on CDM, a simple phenomenological model, and an extrapolation of observed Schechter functions at lower redshifts. The results of the first two models are compared with observations made at redshifts z ∼ 5.7 and z ∼ 6.5, and they are then extrapolated to higher redshift.Results. We present model luminosity functions for redshifts between z = 7−12.5 and give specific number predictions for future planned or possible narrow-band surveys for Lyα emitters. We also investigate what constraints future observations will be able to place on the Lyα luminosity function at very high redshift. Conclusions. It should be possible to observe z = 7−10 Lyα emitters with present or near-future instruments if enough observing time is allocated. In particular, large area surveys such as ELVIS (Emission Line galaxies with VISTA Survey) will be useful in collecting a large sample. However, to get a large enough sample to constrain well the z ≥ 10 Lyα luminosity function, instruments further in the future, such as an ELT, will be necessary.

Discovery of very high energy gamma-ray emission from the blazar 1ES 1727+502 with the MAGIC Telescopes

“…1ES 1727+502 has a bright host galaxy, contributing >50% to the flux in the optical R-band (Nilsson et al 2007). To derive the νF ν in the optical band, this contribution is subtracted from the measured flux and, in addition, the brightness is corrected for galactic absorption by R = 0.079 mag (Schlegel et al 1998).…”

“…Therefore we only used this dataset for the compilation of the SED. The host galaxy contribution in the V and B bands was extrapolated from the R-band values from Nilsson et al (2007) using the galaxy colours at z = 0 from Fukugita et al (1995). The host galaxy contribution in the U and ultraviolet bands is negligible.…”

Limits on the luminosity function of Lyαemitters atz= 7.7

“…Finally, we note that other models that predict the evolution of the LF of high-z LAEs are available in the literature (Baugh et al 2005;Le Delliou et al 2006;Cole et al 2000;Mao et al 2007; Thommes & Meisenheimer 2005;Mesinger & Furlanetto 2008), see also Nilsson et al (2007) for a comparison of some of these models. These models add various ingredients into the simulations, and discussing our results in the light of each of these models is beyond the scope of this paper.…”

Probing the first galaxies with the Square Kilometer Array

“…At z ∼ 20, direct emission from stars will be below the threshold of JWST observations and new techniques will be required to probe the onset of reionization. One possibility is Lyman-α emitter surveys over the next decade, but even these surveys will only be able to detect the brightest galaxies for selected redshift ranges at z ≤ 10 (e.g., Ouchi et al 2008;Nilsson et al 2007;Cuby et al 2007;Stark et al 2007;Willis et al 2008;McMahon et al 2008;Hibon et al 2010), but not the fainter, first galaxies at redshift z ≥ 20. The next generation of large ground based telescopes, like the European Extremely Large Telescope (E-ELT 2 ), Thirty Meter Telescope (TMT 3 ), and Giant Magellan Telescope (GMT 4 ), will Hubble Fellow.only be capable of detecting at most the very brightest galaxies at redshifts z ≈ 20.…”