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ABSTRACT The shape of the low-mass (faint) end of the galaxy stellar mass function (SMF) or ultraviolet luminosity function (UVLF) at $$z \gtrsim 6$$ is an open question for understanding which galaxies primarily drove cosmic reionization. Resolved photometry of Local Group low-mass galaxies allows us to reconstruct their star formation histories, stellar masses, and UV luminosities at early times, and this fossil record provides a powerful ‘near-far’ technique for studying the reionization-era SMF/UVLF, probing orders of magnitude lower in mass than direct HST/JWST observations. Using 882 low-mass ($$M_{\rm star}\lesssim 10^{9}\, \rm {M_\odot }$$) galaxies across 11 Milky Way (MW)- and Local Group-analogue environments from the FIRE-2 cosmological baryonic zoom-in simulations, we characterize their progenitors at $$z=6\!-\!9$$, the mergers/disruption of those progenitors over time, and how well their present-day fossil record traces the high-redshift SMF. A present-day galaxy with $$M_{\rm star}\sim 10^5\, \rm {M_\odot }$$ ($$\sim 10^9\, \rm {M_\odot }$$) had $$\approx 1$$ ($$\approx 30$$) progenitors at $$z\approx 7$$, and its main progenitor comprised $$\approx 100~{{\ \rm per\ cent}}$$ ($$\approx 10~{{\ \rm per\ cent}}$$) of the total stellar mass of all its progenitors at $$z\approx 7$$. We show that although only $$\sim 15~{{\ \rm per\ cent}}$$ of the early population of low-mass galaxies survives to present day, the fossil record of surviving Local Group galaxies accurately traces the low-mass slope of the SMF at $$z \sim 6 \!-\! 9$$. We find no obvious mass dependence to the mergers and accretion, and show that applying this reconstruction technique to just low-mass galaxies at $z = 0$ and not the MW/M31 hosts correctly recovers the slope of the SMF down to $$M_{\rm star} \sim 10^{4.5}\, \rm {{\rm M}_{\odot }}$$ at $$z \gtrsim 6$$. Thus, we validate the ‘near-far’ approach as an unbiased tool for probing low-mass reionization-era galaxies.
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This content will become publicly available on August 21, 2025
An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: an unbiased study of SMG environments measured with narrow-band imaging
ABSTRACT Submillimetre galaxies (SMGs) are some of the most extreme star-forming systems in the Universe, whose place in the framework of galaxy evolution is as yet uncertain. It has been hypothesized that SMGs are progenitors of local early-type galaxies, requiring that SMGs generally reside in galaxy cluster progenitors at high redshift. We test this hypothesis and explore SMG environments using a narrow-band VLT/HAWK-I+GRAAL study of H $$\alpha$$ and [O iii] emitters around an unbiased sample of three ALMA-identified and spectroscopically confirmed SMGs at $$z \sim 2.3$$ and $$\sim 3.3$$, where these SMGs were selected solely on spectroscopic redshift. Comparing with blank-field observations at similar epochs, we find that one of the three SMGs lies in an overdensity of emission-line sources on the $$\sim 4$$ Mpc scale of the HAWK-I field of view, with overdensity parameter $$\delta _{g} = 2.6^{+1.4}_{-1.2}$$. A second SMG is significantly overdense only on $$\lesssim 1.6$$ Mpc scales and the final SMG is consistent with residing in a blank field environment. The total masses of the two overdensities are estimated to be $$\log (M_{h}/{\rm M}_{\odot }) =$$ 12.1–14.4, leading to present-day masses of $$\log (M_{h,z=0}/{\rm M}_{\odot }) =$$ 12.9–15.9. These results imply that SMGs occupy a range of environments, from overdense protoclusters or protogroups to the blank field, suggesting that while some SMGs are strong candidates for the progenitors of massive elliptical galaxies in clusters, this may not be their only possible evolutionary pathway.
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- Award ID(s):
- 2407089
- PAR ID:
- 10593033
- Publisher / Repository:
- Monthly Notices of the Royal Astronomical Society
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 533
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 2399 to 2419
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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