Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Tiger Yu-Yang Hsiao, Fengwu Sun, Xiaojing Lin, Dan Coe, Eiichi Egami
| Summary:
Population III stars, the hypothetical first generation metal-free stars,
have yet to be discovered. Even after three years of successful JWST
operations, studies have shown that most galaxies identified to date at $z > 5$
exhibit a metallicity floor of $Zgtrsim2%,Z_{odot}$, possibly due to
unknown selection biases toward bright galaxies or rapid metal enrichment. To
address this question, we search for galaxies with low
R3$=$[OIII]$,lambda$5008/H$beta$ ratios as part of the JWST Cycle-3 large
treasury program, the Slitless Areal Pure-Parallel HIgh-Redshift Emission
Survey (SAPPHIRES). Using deep NIRCam Wide-Field Slitless Spectrscopy (WFSS)
data, we report the discovery of seven extremely metal-poor galaxy candidates
in the SAPPHIRES Early Data Release field, with estimated $12+{rm
log(O/H)}<7.0$ at $zsim5-7$, including two sources with $Z<1%,Z_{odot}$,
significantly breaking the metallicity floor observed both locally and at high
redshift. These candidates appear extremely faint ($sim28-30,$ F200W AB mag)
and low-mass (${rm log}(M_{*}/M_{odot})sim6.8-7.8$), as expected from the
mass-metallicity relation. They also exhibit very blue UV slopes
($-2.6lesssimbetalesssim-2.0$), likely due to low dust content
$A_{V}lesssim0.2,{rm mag}$ or young stellar ages $sim5-20,{rm Myr}$.
Compared to galaxies at similar redshift, they appear exceptionally bursty in
their star formation activity. Our results highlight the power of NIRCam/WFSS
in identifying extremely metal-poor galaxies, from just a single pointing, with
more data to come in SAPPHIRES. This underscores the potential of pure-parallel
programs towards achieving JWST’s primary science goal: discovering the first
pristine stars and galaxies. Deep JWST/NIRSpec follow-up observations will also
be essential to confirm their nature and perform detailed chemical abundance
analyses.
| Search Query: ArXiv Query: search_query=au:”Roberto Maiolino”&id_list=&start=0&max_results=3