LOFAR properties of SILVERRUSH Ly$\alpha$ emitter candidates in the ELAIS-N1 field

Abstract

Lyman alpha emitters (LAEs) in the Epoch of Reionization (EoR) offer valuable probes of early galaxy evolution and the process of reionization; however, the exact evolution of their abundance and the nature of their emission remain open questions. We combine samples of 229 and 349 LAE candidates at $z=5.7$ and $z=6.6,$ respectively, from the SILVERRUSH narrowband survey with deep Low Frequency Array (LOFAR) radio continuum observations in the ELAIS-N1 field to search for radio galaxies in the EoR and study the low-frequency radio properties of $z\gtrsim 5.7$ LAE emitters. Our LOFAR observations reach an unprecedented noise level of $\sim 20\mu$Jy beam${}^{-1}$ at 150MHz, and we detect five candidate LAEs at $>5\sigma$ significance. Based on detailed spectral energy distribution modelling of independent multi-wavelength observations, we conclude that these sources are likely [OII] emitters at $z=1.47$, yielding no reliable $z\gtrsim 5.7$ radio galaxy candidates. We examine the 111 $z=5.7$ and $z=6.6$ LAE candidates from our panchromatic photometry catalogue that are undetected by LOFAR, finding contamination rates of 81-92% for the $z=5.7$ and $z=6.6$ subset of the LAE candidate samples. This subset is biased towards brighter magnitudes and redder near-infrared colours. The contamination rates of the full sample will therefore likely be lower than the reported values. Contamination is lowered significantly through constraints on the near-infrared colours, highlighting the need for infrared observations to robustly identify bright LAEs in narrowband surveys. Finally, the stacking of radio continuum observations for the robust LAE samples yields 2$\sigma$ upper limits on radio luminosity of 8.2$\times$10${}^{23}$ and 8.7$\times$10${}^{23}$ W Hz${}^{-1}$ at $z=5.7$ and $6.6$, respectively, corresponding to limits on their median star-formation rates of $<$53 and $<$56 M${}_{\odot }$ yr${}^{-1}$.

17 pages, 11 figures, accepted for publication in A&A. The abstract is abridged. This paper is part of the 1st data release of the LoTSS Deep Fields

References in corpus (23)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• The Subaru/XMM-Newton Deep Survey (SXDS). IV. Evolution of Lya Emitters from z=3.1 to 5.7 in the 1 deg^2 Field: Luminosity Functions and AGN
• The mass evolution of the first galaxies: stellar mass functions and star formation rates at $4<z<7$ in the CANDELS GOODS-South field
• The galaxy stellar mass function at 3.5<z<7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields
• The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging
• The MUSE 3D view of the Hubble Deep Field South
• LOFAR/H-ATLAS: The low-frequency radio luminosity - star-formation rate relation
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• Identification of the brightest Lyα emitters at z=6.6: implications for the evolution of the luminosity function in the re-ionisation era
• Accelerated Evolution of Ly$\alpha$ Luminosity Function at $\text{z}\gtrsim 7$ Revealed by the Subaru Ultra-Deep Survey for Ly$\alpha$ Emitters at $\text{z}=7.3$
• The LOFAR Two Metre Sky Survey: Deep Fields Data Release 1 -- III. Host-galaxy identifications and value added catalogues
• Evolution of the H$\beta$+[OIII] and [OII] luminosity functions and the [OII] star-formation history of the Universe up to $z$ ~ 5 from HiZELS
• The CALYMHA survey: Lya luminosity function and global escape fraction of Lya photons at z=2.23
• A Hard Ionizing Spectrum in z=3-4 Ly-alpha Emitters with Intense [OIII] Emission: Analogs of Galaxies in the Reionization Era?
• The LOFAR Two-metre Sky Survey Deep fields: The star formation rate - radio luminosity relation at low frequencies
• Photometric redshifts for the next generation of deep radio continuum surveys - I: Template fitting
• Spectroscopic properties of luminous Lyman-α emitters at $z\approx 6-7$ and comparison to the Lyman-break population
• The Stellar Mass, Star Formation Rate and Dark Matter Halo Properties of LAEs at $z\sim 2$
• Modelling the luminosities and sizes of radio galaxies: radio luminosity function at z = 6
• A Faint Flux-Limited Lyman Alpha Emitter Sample at $z\sim 0.3$
• A search for faint high-redshift radio galaxy candidates at 150 MHz
• The MOSDEF Survey: Calibrating the relationship between H$\alpha$ star-formation rate and radio continuum luminosity at $1.4<z<2.6$

Cited by in corpus (7)

• The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
• HELP: The Herschel Extragalactic Legacy Project
• Discovery of 24 radio-bright quasars at $4.9\le z\le 6.6$ using low-frequency radio observations
• Radio and Far-IR Emission Associated with a Massive Star-forming Galaxy Candidate at z$\simeq$6.8: A Radio-Loud AGN in the Reionization Era?
• Exploring the cosmic dawn and epoch of reionization with 21cm line
• The LOFAR Two-metre Sky Survey: Deep Fields Data Release 2. I. The ELAIS-N1 field
• Distinguishing AGN from starbursts as the origin of double peaked Lyman-Alpha Emitters in the reionization era