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Abstract We investigate the effects of stellar populations and sizes on Lyαescape in 27 spectroscopically confirmed and 35 photometric Lyαemitters (LAEs) atz≈ 2.65 in seven fields of the Boötes region of the NOAO Deep Wide-Field Survey. We use deep HST/WFC3 imaging to supplement ground-based observations and infer key galaxy properties. Compared to typical star-forming galaxies (SFGs) at similar redshifts, the LAEs are less massive (M⋆≈ 107–109M⊙), younger (ages ≲1 Gyr), smaller (re< 1 kpc), and less dust-attenuated (E(B−V) ≤ 0.26 mag) but have comparable star formation rates (SFRs ≈ 1–100M⊙yr−1). Some of the LAEs in the sample may be very young galaxies having low nebular metallicities (Zneb≲ 0.2Z⊙) and/or high ionization parameters ( ). Motivated by previous studies, we examine the effects of the concentration of star formation and gravitational potential on Lyαescape by computing SFR surface density, ΣSFR, and specific SFR surface density, ΣsSFR. For a given ΣSFR, the Lyαescape fraction is higher for LAEs with lower stellar masses. The LAEs have a higher ΣsSFR, on average, compared to SFGs. Our results suggest that compact star formation in a low gravitational potential yields conditions amenable to the escape of Lyαphotons. These results have important implications for the physics of Lyαradiative transfer and for the type of galaxies that may contribute significantly to cosmic reionization.
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This content will become publicly available on June 1, 2026
Galaxy populations in protoclusters at cosmic noon
Aims.We investigate the physical properties and redshift evolution of simulated galaxies residing in unvirialized cosmic structures (i.e., protoclusters) at cosmic noon, to understand the influence of the environment on galaxy formation. This work is intended to build clear expectations for the ongoing ODIN (One-hundred-deg2DECam Imaging in Narrowbands) survey, which is mapping large-scale structures atz= 2.4,3.1, and 4.5 using Lyα-emitting galaxies (LAEs) as tracers. Methods.From the IllustrisTNG simulations, we define subregions centered on the most massive clusters ranked by total stellar mass atz= 0 and study the properties of galaxies within, including those of LAEs. To model the LAE population, we take a semi-analytical approach that assigns Lyαluminosity and equivalent width based on the UV luminosities to galaxies in a probabilistic manner. We investigate stellar mass, star formation rate (SFR), major merger events, and specific star formation rate of the population of star-forming galaxies and LAEs in the field- and protocluster environment and trace their evolution across cosmic time betweenz= 0−4. Results.We find that the overall shape of the UV luminosity function in simulated protocluster environments is characterized by a substantially shallower faint-end slope and a large excess on the bright end, signaling different formation histories for galaxies therein. The difference is milder for the Lyαluminosity function. While protocluster galaxies follow the same SFR-M★scaling relation as average field galaxies, a larger fraction appears to have experienced major mergers in the last 200 Myr and as a result shows enhanced star formation at a ≈60% level, leading to a flatter distribution in both SFR and M★relative to galaxies in the average field. We find that protocluster galaxies, including LAEs, begin to quench much earlier (z∼0.8−1.6) than field galaxies (z∼0.5−0.9); our result is in qualitative agreement with recent observational results and highlights the importance of large-scale environment on the overall formation history of galaxies.
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- PAR ID:
- 10636304
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Astronomy & Astrophysics
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 698
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A280
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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