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

Fengwu Sun, Eiichi Egami, Pablo G. Pérez-González, Ian Smail, Karina I. Caputi, Franz E. Bauer, Timothy D. Rawle, Seiji Fujimoto, Kotaro Kohno, Ugne Dudzevičiūtė, Hakim Atek, Matteo Bianconi, Scott C. Chapman, Francoise Combes, Mathilde Jauzac, Jean Baptiste Jolly, Anton M. Koekemoer, Georgios E. Magdis, Giulia Rodighiero, Wiphu RujopakarnDaniel Schaerer, Charles L. Steinhardt, Paul Van Der Werf, Gregory L. Walth, John R. Weaver

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We present a Spitzer/IRAC survey of H-faint (H 160 ⪆ 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 M star = 1010.3±0.3 M o˙), star-forming (median star formation rate 100-40+60 M o˙ yr-1), and dust-obscured (A V = 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 (R e,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 (R e,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 o˙ 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.

Original languageEnglish (US)
Article number114
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 1 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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