title: Y-NBS
title: surveying star formation from the epoch of reionisation to the local universe
titleType: Subtitle
Creators: name: Wade, Heather
Publisher: name: Lancaster University
Year: 2024
Subjects: galaxies: evolution
galaxies: high-redshift
Galaxies: luminosity function, mass function

description: The first galaxies, inside the epoch of reionisation, are very different
 to those locally (13.7 billion years later) and understanding this
 evolution is one of the most fundamental areas of research in
 observational astrophysics. The star formation history of the Universe
 probes the growth of galaxies and shows that the star formation rate
 densities (SFRD) of galaxies increase from the early Universe, during the
 epoch of reionisation, until it peaks at z = 2 − 3, at cosmic noon. After
 cosmic noon, the star formation rate density of galaxies decreases to the
 present day. To understand this evolution and its causes requires
 measuring the evolving SFRD for different types of galaxies. One method to
 probe the Universe and its star formation history is to select samples of
 line emitting galaxies in a self-consistent way. In this work, we present
 a wide-area narrowband survey, Y-NBS, conducted on VLT/HAWK-I with the
 NB1060 filter in the COSMOS field. We complement this with a deeper
 archival VLT/HAWK-I pointing covering GOODS-S. We present the full data
 reduction pipeline for the COSMOS data and then combine it with
 complementary broadband and redshift data. Using spectroscopic redshifts,
 photometric redshifts and colour-colour selection, we select samples of
 Hα, [Oiii] and [Oii] emitting galaxies at z = 0.62, z = 1.12 and z = 1.85,
 respectively. Luminosity functions of these samples are plotted and
 Schechter functions are fitted with all three parameters free, which is
 only possible due to our simultaneously wide survey with deep regions. Our
 results for the faint-end slope (α) are α = −1.48+0.17−0.17,
 −1.95+0.18−0.15 and −2.43+0.19−0.16 for Hα, [Oiii] and [Oii] respectively.
 Our measurements are consistent with previous studies of these luminosity
 functions at similar redshifts but we probe deeper or over a wider range
 of luminosities than many other surveys. Star formation rate densities
 calculated from our luminosity functions are consistent with others, but
 our [Oii] result is ∼ 0.3 dex higher than expected, likely because we
 observed a steeper faint-end slope than other surveys. Y-NBS also targets
 z = 7.7 Lyα emitters, probing into the epoch of reionisation. Although we
 do not find any, we place robust constraints on the z = 7.7 Lyα luminosity
 function, which are in agreement with spectroscopically confirmed sources
 at this redshift. We constrain the neutral fraction of hydrogen to be χHI
 &gt; 0.4 at z = 7.7, which is consistent with previous studies at z =
 7.0 − 7.3. Overall, our work highlights the need for future narrowband
 surveys to be wide and deep, specifically in the same field, to help
 overcome cosmic variance and to simultaneously constrain both the faint
 and bright ends of the luminosities functions. If the deep and shallow
 regions were in the same field, it would help to rule out the possibility
 that any observed differences in the density between the deep and shallow
 regions were the result of cosmic variance. Such work would further our
 understanding of the star formation history of the Universe from the epoch
 of reionisation, through cosmic noon, to the local Universe.