Deep ALMA redshift search of a z ∼ 12 GLASS-JWST galaxy candidate

Abstract

The James Webb Space Telescope (JWST) has discovered a surprising abundance of bright galaxy candidates in the very early Universe (≤500 Myrs after the Big Bang), calling into question current galaxy formation models. Spectroscopy is needed to confirm the primeval nature of these candidates, as well as to understand how the first galaxies form stars and grow. Here we present deep spectroscopic and continuum ALMA observations towards GHZ2/GLASS-z12, one of the brightest and most robust candidates at z > 10 identified in the GLASS-JWST Early Release Science Program. We detect a 5.8σ line, offset 0.″5 from the JWST position of GHZ2/GLASS-z12 that, associating it with the [O iii] 88 $\mu {\rm m}$ transition, implies a spectroscopic redshift of z = 12.117 ± 0.001. We verify the detection using extensive statistical tests. The oxygen line luminosity places GHZ2/GLASS-z12 above the [O iii]-SFR relation for metal-poor galaxies, implying an enhancement of [O iii] emission in this system while the JWST-observed emission is likely a lower-metallicity region. The lack of dust emission seen by these observations is consistent with the blue UV slope observed by JWST, which suggest little dust attenuation in galaxies at this early epoch. Further observations will unambiguously confirm the redshift and shed light on the origins of the wide and offset line and physical properties of this early galaxy. This work illustrates the synergy between JWST and ALMA and paves the way for future spectroscopic surveys of z > 10 galaxy candidates.

An upper limit on [O III] 88 μm and 1.2 mm continuum emission from a JWSTz ≈ 12–13 galaxy candidate with ALMA

“…A.1). These results are consistent with the findings by Bakx et al (2023), who did not find [O iii] 88 µm line emission at the location of GLASS-z13 either. I used the Findclump algorithm (Walter et al 2016) that was designed to identify emission lines in an automated fashion to search for a line using a more objective approach.…”

“…The lack of detected [O iii] 88 µm emission suggests that no [O iii] 88 µm emission line is present in the explored frequency range, or it is fainter than the sensitivity limit of the data. Bakx et al (2023) report a tentative ∼5σ extended detection approximately 0.5 offset from the location of GLASS-z13. Findclump identifies this line, but assigns it a fidelity of only 0.04 (with a probability of the line being real of 4%).…”

The Gas and Stellar Content of a Metal-poor Galaxy at z = 8.496 as Revealed by JWST and ALMA

“…JWST and ALMA thus jointly provide a unique and comprehensive view of the gas, dust, and metal content of the first galaxies. While the first such combined studies of some of the highest-redshift galaxy candidates identified by JWST remain inconclusive (Bakx et al 2023;Fujimoto et al 2022a;Popping 2023;Yoon et al 2022), it is still not entirely clear whether this is due to their likely low metallicities or to their potentially erroneous photometric redshifts.…”

Broad Emission Lines in Optical Spectra of Hot, Dust-obscured Galaxies Can Contribute Significantly to JWST/NIRCam Photometry

“…Spectroscopic confirmation is needed to verify these redshifts. However, some early attempts at spectroscopic followup using facilities such as ALMA have yielded upper limits or tentative low-signal-to-noiseratio (SNR) detections (e.g., Bakx et al 2023;Fujimoto et al 2022;Kaasinen et al 2023;Yoon et al 2022). JWST/NIRSpec has proven capable of spectroscopically detecting the rest-frame optical light from galaxies up to z ∼ 9-10 (Carnall et al 2023;Roberts-Borsani et al 2022), but this might not be well suited for rapidly validating redshifts in statistical samples.…”