The ALMA Frontier Fields Survey

I. 1.1 mm continuum detections in Abell 2744, MACS J0416.1-2403 and MACS J1149.5+2223^⋆

¹ Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, 22 Santiago, Chile
e-mail: jgonzal@astro.puc.cl
² Millennium Institute of Astrophysics, 1515 Las Condes, Santiago, Chile
³ Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
⁴ Joint ALMA Observatory, 3107 Alonso de Córdova, Vitacura, Santiago, Chile
⁵ European Southern Observatory, 3107 Alonso de Córdova, Vitacura, 19001 Casilla, Santiago, Chile
⁶ Departamento de Ciencias Físicas, Universidad Andres Bello, 252 Avenida República, Santiago, Chile
⁷ Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, 441 Av. Ejército, Santiago, Chile
⁸ Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
⁹ Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
¹⁰ Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Philosophenweg 12, 69120 Heidelberg, Germany
¹¹ Department of Astronomy, Universidad de Concepcion, Casilla 160-C, Concepción, Chile
¹² Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
¹³ Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso, Chile
¹⁴ Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, OAL, Tapada da Ajuda, 1349-018 Lisboa, Portugal
¹⁵ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA
¹⁶ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
¹⁷ Physics Department, Ben-Gurion University of the Negev, PO Box 653, 84105 Be’er-Sheva, Israel

Received: 27 April 2016
Accepted: 26 September 2016

Abstract

Context. Dusty star-forming galaxies are among the most prodigious systems at high redshift (z > 1), characterized by high star-formation rates and huge dust reservoirs. The bright end of this population has been well characterized in recent years, but considerable uncertainties remain for fainter dusty star-forming galaxies, which are responsible for the bulk of star formation at high redshift and thus play a key role in galaxy growth and evolution.

Aims. In this first paper of our series, we describe our methods for finding high redshift faint dusty galaxies using millimeter observations with ALMA.

Methods. We obtained ALMA 1.1 mm mosaic images for three strong-lensing galaxy clusters from the Frontier Fields Survey, which constitute some of the best studied gravitational lenses to date. The ≈2′ × 2′ mosaics overlap with the deep HST WFC3/IR footprints and encompass the high magnification regions of each cluster for maximum intrinsic source sensitivity. The combination of extremely high ALMA sensitivity and the magnification power of these clusters allows us to systematically probe the sub-mJy population of dusty star-forming galaxies over a large surveyed area.

Results. We present a description of the reduction and analysis of the ALMA continuum observations for the galaxy clusters Abell 2744 (z = 0.308), MACS J0416.1-2403 (z = 0.396) and MACS J1149.5+2223 (z = 0.543), for which we reach observed rms sensitivities of 55, 59 and 71 μJy beam^-1 respectively. We detect 12 dusty star-forming galaxies at S/N ≥ 5.0 across the three clusters, all of them presenting coincidence with near-infrared detected counterparts in the HST images. None of the sources fall close to the lensing caustics, thus they are not strongly lensed. The observed 1.1 mm flux densities for the total sample of galaxies range from 0.41 to 2.82 mJy, with observed effective radii spanning ≲0.̋05 to 0.̋37 ± 0.̋21 . The lensing-corrected sizes of the detected sources appear to be in the same range as those measured in brighter samples, albeit with possibly larger dispersion.