ACCELERATED EVOLUTION OF THE Lyα LUMINOSITY FUNCTION ATz≳ 7 REVEALED BY THE SUBARU ULTRA-DEEP SURVEY FOR Lyα EMITTERS ATz= 7.3

Abstract

We present the deepest study to date of the Lyα luminosity function in a blank field using blind integral field spectroscopy from MUSE. We constructed a sample of 604 Lyα emitters (LAEs) across the redshift range 2.91 < z < 6.64 using automatic detection software in the Hubble Ultra Deep Field. The deep data cubes allowed us to calculate accurate total Lyα fluxes capturing low surface-brightness extended Lyα emission now known to be a generic property of high-redshift star-forming galaxies. We simulated realistic extended LAEs to fully characterise the selection function of our samples, and performed flux-recovery experiments to test and correct for bias in our determination of total Lyα fluxes. We find that an accurate completeness correction accounting for extended emission reveals a very steep faint-end slope of the luminosity function, α, down to luminosities of log 10 L erg s −1 < 41.5, applying both the 1/V max and maximum likelihood estimators. Splitting the sample into three broad redshift bins, we see the faint-end slope increasing from −2.03 +1.42 −0.07 at z ≈ 3.44 to −2.86 +0.76 −∞ at z ≈ 5.48, however no strong evolution is seen between the 68% confidence regions in L *-α parameter space. Using the Lyα line flux as a proxy for star formation activity, and integrating the observed luminosity functions, we find that LAEs' contribution to the cosmic star formation rate density rises with redshift until it is comparable to that from continuum-selected samples by z ≈ 6. This implies that LAEs may contribute more to the star-formation activity of the early Universe than previously thought, as any additional inter-glactic medium (IGM) correction would act to further boost the Lyα luminosities. Finally, assuming fiducial values for the escape of Lyα and LyC radiation, and the clumpiness of the IGM, we integrated the maximum likelihood luminosity function at 5.00 < z < 6.64 and find we require only a small extrapolation beyond the data (< 1 dex in luminosity) for LAEs alone to maintain an ionised IGM at z ≈ 6.

The Impact of JWST Broadband Filter Choice on Photometric Redshift Estimation

“…We Redshift distribution of the three galaxy samples considered in this work: a galaxy sample with spectroscopic redshifts in the GOODS-S field (filled gray; sample 1), a galaxy sample with well-established CANDELS photometric redshifts, also in GOODS-S (red line; sample 2), and a sample of simulated galaxies with known input redshifts (dashed line; sample 3). explicitly decided not to include the Lyα line because the importance of its emission in galaxies at > z 7 is still unclear (e.g., Stark et al 2013;Konno et al 2014;Pentericci et al 2014). Finally, we normalized every model at 29AB mag at 1.5 μm (corresponding to the NIRCam F150W filter pivot wavelength).…”

Narrowband selected high-redshift galaxy candidates contaminated by lower redshift [OIII] ultra-strong emitter line galaxies

“…These objects have magnitude differences ranging from 2.3 to 3.5 between the five optical (ugriz) bands and the NB1060 band. This represents large colour breaks, considering that the optical-NB breaks used for selecting LAE samples at high redshift is of the order of 1.5 to 2.5 mag in most studies (for instance, Hibon et al 2012;Shibuya et al 2012;Konno et al 2014). Indeed, from Table 1, we infer that with the use of colour breaks of one magnitude lower, the three objects would have been selected as LAE candidates.…”

“…Thus far, only one of the LAE candidates from these searches has been confirmed spectroscopically at z ∼ 7.3. It was found with the Suprime-Cam CCD camera equipped with a special NB filter at the Subaru telescope (Konno et al 2014). Both the LBG and the NB observations have now convincingly pointed to a decline of the Lyα radiation at redshifts >7, possibly because of an increasing fraction of neutral hydrogen from z ∼ 6 when the Universe was completely re-ionized.…”

“…Cuby et al (2007), Willis et al (2008) for pioneering searches at redshifts 8.8 with small format near IR detectors. With the advent of large mosaics of near IR arrays, more recent searches have been carried out at redshifts 7.3, 7.7 and 8.8 (Tilvi et al 2010;Hibon et al 2010Hibon et al , 2011Krug et al 2012;Clément et al 2012;Shibuya et al 2012;Milvang-Jensen et al 2013;Matthee et al 2014;Konno et al 2014). Thus far, only one of the LAE candidates from these searches has been confirmed spectroscopically at z ∼ 7.3.…”

Constraining the epoch-of-reionization model parameters with the 21-cm bispectrum

“…For example, high-z QSO absorption lines imprinted in their spectra indicate that reionization concluded by z ∼ 6(e.g. (Fan et al 2006)), and the rapid evolution of the Ly-α luminosity function with redshift constrains the neutral hydrogen fraction at z > 6 (Konno et al 2014). Furthermore, the optical depth of Thomson scattering has been measured and the value obtained by PLANCK is τe = 0.066 ± 0.016 (Planck Collaboration 2015).…”