Publication: Differences and similarities of stellar populations in LAEs and LBGs at z ∼ 3.4−6.8
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2020-06
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Oxford University Press.
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Abstract
Lyman alpha emitters (LAEs) and Lyman break galaxies (LBGs) represent the most common groups of star-forming galaxies at high z, and the differences between their inherent stellar populations (SPs) are a key factor in understanding early galaxy formation and evolution. We have run a set of SP burst-like models for a sample of 1558 sources at 3.4 <z< 6.8 from the Survey for High-z Absorption Red and Dead Sources (SHARDS) over the GOODS-N field. This work focuses on the differences between the three different observational subfamilies of our sample: LAE–LBGs, no-Ly α LBGs, and pure LAEs. Single and double SP synthetic spectra were used to model the spectral energy distributions, adopting a Bayesian information criterion to analyze under which situations a second SP is required. We find that the sources are well modelled using a single SP in ∼ 79 per cent of the cases. The best models suggest that pure LAEs are typically young low-mass galaxies (t ∼ 26^(+41)_(−25) Myr; M_(star) ∼ 5.6^(+12.0) _(−5.5) × 10^(8) Mͽ), undergoing one of their first bursts of star formation. On the other hand, no-Ly α LBGs require older SPs (t ∼ 71 ± 12 Myr), and they are substantially more massive (M_(star) ∼ 3.5 ± 1.1 × 10^(9) Mͽ). LAE–LBGs appear as the subgroup that more frequently needs the addition of a second SP, representing an old and massive galaxy caught in a strong recent star-forming episode. The relative number of sources found from each subfamily at each z supports an evolutionary scenario from pure LAEs and single SP LAE–LBGs to more massive LBGs. Stellar mass functions are also derived, finding an increase of M∗ with cosmic time and a possible steepening of the low-mass slope from z ∼ 6 to z ∼ 5 with no significant change to z ∼ 4. Additionally, we have derived the SFR–M_(star) relation, finding an SFR ∝ M^(β)_(star) behaviour with negligible evolution from z ∼ 4 to z ∼ 6.
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© 2020 The Author(s). We want to acknowledge support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grants AYA2015- 70498-C2-1-R, AYA2013-47742-C4-2-P, and AYA2016-79724- C4-2-P. Based on observations made with the Gran Telescopio Canarias, installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. We would like to thank Dr. Jairo Méndez Abreu for his help on the use and calibration of the Bayesian information criterion and Dr. J. Miguel Mass Hesse for several discussions about stellar population models. Special thanks to the anonymous referee for very useful and detailed comments that have really improved this work.