J/A+A/689/A44 COLA1 [OIII] emitter sample (Torralba-Torregrosa+, 2024)
Anatomy of an ionized bubble: NIRCam grism spectroscopy of the z = 6.6
double-peaked Lyman-α emitter COLA1 and its environment.
Torralba-Torregrosa A., Matthee J., Naidu R.P., Mackenzie R., Pezzulli G.,
Hutter A., Arnalte-Mur P., Gurung-Lopez S., Tacchella S., Oesch P.,
Kashino D., Conroy C., Sobral D.
<Astron. Astrophys. 689, A44 (2024)>
=2024A&A...689A..44T 2024A&A...689A..44T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Redshifts ; Infrared
Keywords: techniques: spectroscopic - galaxies: high-redshift - dark ages -
reionization - first stars
Abstract:
The increasingly neutral intergalactic gas at z>6 impacts the
Lyman-α (Lyα) flux observed from galaxies. One luminous
galaxy, COLA1, stands out because of its unique double-peaked
Lyα line at z=6.6, unseen in any simulation of
reionization. Here, we present JWST/NIRCam wide-field slitless
spectroscopy in a 21 arcmin2 field centered on COLA1. We find 141
galaxies spectroscopically selected through the [OIII] doublet at
5.35<z<6.95, with 40 of these sources showing Hβ. For COLA1, we
additionally detect [OIII]4363 as well as Hγ. We measure a
systemic redshift of z=6.5917 for COLA1, confirming the
classical double-peak nature of the Lyα profile. This implies
that it resides in a highly ionized bubble and that it is leaking
ionizing photons with a high escape fraction of fesc(LyC)=20-50%,
making it a prime laboratory to study Lyman continuum escape in the
Epoch of Reionization. COLA1 shows all the signs of a prolific ionizer
with a Lyα escape fraction of 81±5%, Balmer decrement
indicating no dust, a steep UV slope (βUV=-3.2±0.4), and a
star-formation surface density ≳10x that of typical galaxies at
similar redshift. We detect five galaxies in COLA1's close environment
({DELTA}z<0.02). Exploiting the high spectroscopic completeness
inherent to grism surveys, and using mock simulations that fully mimic
the selection function, we show that the number of detected companions
is very typical for a normal similarly UV-bright (MUV~-21.3) galaxy
- that is, the ionized bubble around COLA1 is unlikely to be due to an
excessively large over-density. Instead, the measured ionizing
properties suggest that COLA1 by itself might be powering the bubble
required to explain its double-peaked Lyα profile
(Rion∼0.7pMpc), with only minor contributions from detected neighbors
(-19.5≲MUV≲-17.5).
Description:
We use imaging and Wide Field Slitless Spectroscopy (WFSS) with NIRCam
targeting a mosaic centered around COLA1 through JWST program 1933
(PIs Matthee & Naidu). Observations were performed on January 6 and 7,
2023. The coverage consists of four visits in a 2x2 mosaic with a
position angle of 295 deg, which yields three slightly separated
regions of 2.5'x2.8'. The total area of the COLA1 field (hereafter
C1F) is 21 arcmin2.
In this work, we presented results from a new JWST program that took
WFSS and photometric data of the COLA1 field, in combination with
VLT/X-shooter spectroscopy. The aim of this program was to describe
the UV and optical properties of the galaxy COLA1, and to
simultaneously characterise its over-density, traced by [OIII]
emitters that are part of the sample of 141 [OIII] emitters at
5.35<z<6.9 that were selected through [OIII] doublet identification
in the grism data.
A complete list of all the selected sources is found in Table A.1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 59 141 Catalog of the C1F [OIII] emitter sample
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7- 8 I2 h RAh Right ascension (J2000)
10- 11 I2 min RAm Right ascension (J2000)
13- 17 F5.2 s RAs Right ascension (J2000)
19 A1 --- DE- Declination sign (J2000)
20- 21 I2 deg DEd Declination (J2000)
23- 24 I2 arcmin DEm Declination (J2000)
26- 30 F5.2 arcsec DEs Declination (J2000)
32- 36 F5.3 --- z Redshift
38- 43 F6.2 mag UVMAG ?=- Absolute UV magnitude
45- 48 F4.2 mag e_UVMAG ? Absolute UV magnitude error
50- 54 F5.2 [10-7W] logL[OIII] Luminosity of [OIII]λ5008 line
56- 59 F4.2 [10-7W] e_logL[OIII] Luminosity of [OIII]λ5008 line error
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Feb-2025