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ABSTRACT Atomic hydrogen (H i) serves a crucial role in connecting galactic-scale properties such as star formation with the large-scale structure of the Universe. While recent numerical simulations have successfully matched the observed covering fraction of H i near Lyman Break Galaxies (LBGs) and in the foreground of luminous quasars at redshifts $$z \lesssim 3$$, the low-mass end remains as-of-yet unexplored in observational and computational surveys. We employ a cosmological, hydrodynamical simulation (FIREbox) supplemented with zoom-in simulations (MassiveFIRE) from the Feedback In Realistic Environments (FIRE) project to investigate the H i covering fraction of Lyman Limit Systems ($$N_{{\text{H}}\, \rm{{\small I}}} \gtrsim 10^{17.2}$$ cm$$^{-2}$$) across a wide range of redshifts ($z=0-6$) and halo masses ($$10^8-10^{13} \, \,\mathrm{ M}_{\odot }$$ at $z=0$, $$10^8-10^{11}\, \,\mathrm{ M}_{\odot }$$ at $z=6$) in the absence of feedback from active galactic nuclei. We find that the covering fraction inside haloes exhibits a strong increase with redshift, with only a weak dependence on halo mass for higher mass haloes. For massive haloes ($$M_{\mathrm{vir}} \sim 10^{11}-10^{12} \,\mathrm{ M}_{\odot }$$), the radial profiles showcase scale-invariance and remain independent of mass. The radial dependence is well captured by a fitting function. The covering fractions in our simulations are in good agreement with measurements of the covering fraction in LBGs. Our comprehensive analysis unveils a complex dependence with redshift and halo mass for haloes with $$M_{\mathrm{vir}} \lesssim 10^{10} \,\mathrm{ M}_{\odot }$$ that future observations aim to constrain, providing key insights into the physics of structure formation and gas assembly.
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On the expected purity of photometric galaxy surveys targeting the Cosmic Dawn
ABSTRACT Over the last three decades, photometric galaxy selection using the Lyman-break technique has transformed our understanding of the high-z Universe, providing large samples of galaxies at $$3 \lesssim z \lesssim 8$$ with relatively small contamination. With the advent of the JWST, the Lyman-break technique has now been extended to z ∼ 17. However, the purity of the resulting samples has not been tested. Here, we use a simple model, built on the robust foundation of the dark matter halo mass function, to show that the expected level of contamination rises dramatically at $$z \gtrsim 10$$, especially for luminous galaxies, placing stringent requirements on the selection process. The most luminous sources at $$z \gtrsim 12$$ are likely at least 10 000 times rarer than potential contaminants, so extensive spectroscopic follow-up campaigns may be required to identify a small number of target sources.
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- PAR ID:
- 10426369
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 523
- Issue:
- 4
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 5274-5279
- Size(s):
- p. 5274-5279
- Sponsoring Org:
- National Science Foundation
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