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

We present a Spitzer/IRAC survey of H-faint ($H_{160} \gtrsim 26.4$, $<5\sigma$) sources in 101 lensing cluster fields. Across CANDELS/Wide-like area $\sim$648 arcmin$^2$ (effectively $\sim$221 the source plane), we have securely discovered 53 IRAC Channel-2 band (CH2, 4.5 $\mathrm{\mu m}$; median CH2$=22.46\pm0.11$ AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable our sample, namely ES-009 field Abell 2813, is brightest galaxy at m}$ known so far ($\mathrm{CH2}=20.48\pm0.03$ mag). show sample are massive (median $M_\mathrm{star} = 10^{10.3\pm 0.3}$ $M_\odot$), star-forming star formation rate $=100_{-40}^{+60}$ $M_\odot$yr$^{-1}$) and dust-obscured ($A_V=2.6\pm0.3$) galaxies around photometric redshift $z=3.9\pm0.4$. stellar continua 14 can be resolved CH2 band, suggesting circularized effective radius ($R_\mathrm{e,circ}$; corrected) $1.9\pm0.2$ kpc $<1.5$ for whole samples, respectively. This consistent with sizes unobscured $z\sim4$, indicating represent dusty tail distribution wider population. Comparing ALMA dust continuum similar reported previously, conclude heavy obscuration related to compactness both ($R_\mathrm{e,circ}\sim 1$ kpc). These make up $16_{-7}^{+13}$% mass range $10^{10}-10^{11.2}$ $M_\odot$ $z=3\sim5$, contributing $8_{-4}^{+8}$% cosmic density this epoch likely tracing early phase formation.