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Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters

Sun, Fengwu and Egami, Eiichi and Pérez-González, Pablo G. and Smail, Ian and Caputi, Karina I. and Bauer, Franz E. and Rawle, Timothy D. and Fujimoto, Seiji and Kohno, Kotaro and Dudzevičiūtė, Ugnė and Atek, Hakim and Bianconi, Matteo and Chapman, Scott C. and Combes, Francoise and Jauzac, Mathilde and Jolly, Jean-Baptiste and Koekemoer, Anton M. and Magdis, Georgios E. and Rodighiero, Giulia and Rujopakarn, Wiphu and Schaerer, Daniel and Steinhardt, Charles L. and Van der Werf, Paul and Walth, Gregory L. and Weaver, John R. (2021) 'Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters.', The Astrophysical Journal, 922 (2). p. 114.

Abstract

We present a Spitzer/IRAC survey of H-faint (H160 ≳ 26.4, < 5σ) sources in 101 lensing cluster fields. Across a CANDELS/Wide-like survey area of ∼648 arcmin2 (effectively ∼221 arcmin2 in the source plane), we have securely discovered 53 sources in the IRAC Channel-2 band (CH2, 4.5 μm; median CH2 = 22.46 ± 0.11 AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable source in our sample, namely ES-009 in the field of Abell 2813, is the brightest H-faint galaxy at 4.5 μm known so far (CH2 = 20.48 ± 0.03 AB mag). We show that the H-faint sources in our sample are massive (median Mstar = 1010.3±0.3 M⊙), star-forming (median star formation rate $={100}_{-40}^{+60}$ M⊙ yr−1), and dust-obscured (AV = 2.6 ± 0.3) galaxies around a median photometric redshift of z = 3.9 ± 0.4. The stellar continua of 14 H-faint galaxies can be resolved in the CH2 band, suggesting a median circularized effective radius (Re,circ; lensing corrected) of 1.9 ± 0.2 kpc and <1.5 kpc for the resolved and whole samples, respectively. This is consistent with the sizes of massive unobscured galaxies at z ∼ 4, indicating that H-faint galaxies represent the dusty tail of the distribution of a wider galaxy population. Comparing with the ALMA dust continuum sizes of similar galaxies reported previously, we conclude that the heavy dust obscuration in H-faint galaxies is related to the compactness of both stellar and dust continua (Re,circ ∼ 1 kpc). These H-faint galaxies make up ${16}_{-7}^{+13}$% of the galaxies in the stellar-mass range of 1010 − 1011.2 M⊙ at z = 3 ∼ 5, contributing to ${8}_{-4}^{+8}$% of the cosmic star formation rate density in this epoch and likely tracing the early phase of massive galaxy formation

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.3847/1538-4357/ac2578
Date accepted:08 September 2021
Date deposited:21 December 2021
Date of first online publication:25 November 2021
Date first made open access:21 December 2021

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