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Characterizing elusive, faint dusty star-forming galaxies: A lensed, optically undetected ALMA galaxy at z ∼ 3.3

Published version
Peer-reviewed

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Authors

Santini, P 
Castellano, M 
Fontana, A 
Merlin, E 

Abstract

We present the serendipitous ALMA detection of a faint submillimeter galaxy (SMG) lensed by a foreground z ∼ 1 galaxy. By optimizing the source detection to deblend the system, we accurately build the full spectral energy distribution of the distant galaxy from the I814 band to radio wavelengths. It is extremely red, with a I-K colour larger than 2.5. We estimate a photometric redshift of 3.28 and determine the physical parameters. The distant galaxy turns out to be magnified by the foreground lens by a factor of ∼1.5, which implies an intrinsic Ks-band magnitude of ∼24.5, a submillimeter flux at 870 μm of ∼2.5 mJy and a SFR of ∼150-300 M/yr, depending on the adopted tracer. These values place our source towards the faint end of the distribution of observed SMGs, and in particular among the still few faint SMGs with a fully characterized spectral energy distribution, which allows us not only to accurately estimate its redshift, but also to measure its stellar mass and other physical properties. The galaxy studied in this work is a representative of the population of faint SMGs, of which only few objects are known to date, that are undetected in optical and therefore are not typically accounted for when measuring the cosmic star formation history (SFH). This faint galaxy population thus likely represents an important and missing piece in our understanding of the cosmic SFH. Its observation and characterization is of major importance to achieve a solid picture of galaxy evolution.

Description

Keywords

galaxies: evolution, galaxies: fundamental parameters, galaxies: high-redshift, galaxies: photometry, submillimeter: galaxies, cosmology: observations

Journal Title

Astronomy and Astrophysics

Conference Name

Journal ISSN

0004-6361
1432-0746

Volume Title

596

Publisher

EDP Sciences
Sponsorship
European Research Council (695671)
Science and Technology Facilities Council (ST/K003119/1)
Science and Technology Facilities Council (ST/M001172/1)
The research leading to these results has received funding from the European Union Seventh Framework Programme ASTRODEEP (FP7/2007-2013) under grant agreement No. 312725. R.M. and R.A. acknowledge support from the ERC Advanced Grant 695671 QUENCH.