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| Main Authors: | , , , , |
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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2404.10998 |
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Table of Contents:
- We investigate the galaxy properties of $\sim$400 low-mass ($<10^9\,M_{\odot}$) H$α$ emitters (HAEs) at z $\sim$ 2.3 in the ZFOURGE survey. The selection of these HAEs is based on the excess in the observed $K_s$ broad-band flux compared to the stellar continuum estimated from the best-fit SED. These low-mass HAEs have elevated SFR(H$α$) above the star formation main sequence (SFMS), making them potential analogs of the galaxies that reionized the universe during the epoch of reionization. The ionizing photon production efficiencies ($ξ_{ion}$) of the low-mass HAEs have a median value of $\mathrm{log}(ξ_{ion}/erg^{-1} Hz)=25.24^{+0.10}_{-0.13}\ (25.35^{+0.12}_{-0.15})$, assuming the Calzetti (SMC) curve for the stellar continuum dust correction. This value is higher than that of main sequence galaxies by $\sim$0.2 dex at similar redshift, indicating that the low-mass HAEs are more efficient in producing ionizing photons. Our results also consolidate the trend of increasing $ξ_{ion}$ with redshift, but reveal a "downsizing" relationship between $ξ_{ion}$ and stellar mass ($M_{\odot}$) with increasing redshift. We further explore the dependence of $ξ_{ion}$ on other galaxy properties, such as the UV spectral slope ($β_{\mathrm{UV}}$), the UV magnitude ($M_{\mathrm{UV}}$), the equivalent widths ($EWs$) of H$α$ and [O{\sc iii}] emission lines. Galaxies with the bluer UV slopes, fainter UV luminosities and higher equivalent widths exhibit elevated $ξ_{ion}$ by a factor of $\sim$2 compared to the median $ξ_{ion}$ of our sample. JWST data will provide an opportunity to extend our method and further investigate the properties of low-mass galaxies at high redshifts.