Open AccessAn ultradeep submillimetre map: beneath the SCUBA confusion limit with lensing and robust source extraction
Author(s) -
Knudsen K. K.,
Barnard V. E.,
Van Der Werf P. P.,
Vielva P.,
Kneib J.P.,
Blain A. W.,
Barreiro R. B.,
Ivison R. J.,
Smail I.,
Peacock J. A.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10138.x
Subject(s) - physics , astrophysics , source counts , flux (metallurgy) , galaxy , confusion , bolometer , astronomy , redshift , optics , detector , psychology , materials science , psychoanalysis , metallurgy
Extracting sources with low signal‐to‐noise ratio (S/N) from maps with structured background is a non‐trivial task which has become important in studying the faint end of the submillimetre (submm) number counts. In this paper, we study the source extraction from submm jiggle‐maps from the Submillimetre Common‐User Bolometer Array (SCUBA) using the Mexican hat wavelet (MHW), an isotropic wavelet technique. As a case study, we use a large (11.8‐arcmin 2 ) jiggle‐map of the galaxy cluster Abell 2218 (A2218), with a 850‐μm 1σ rms sensitivity of 0.6–1 mJy. We show via simulations that MHW is a powerful tool for the reliable extraction of low‐S/N sources from the SCUBA jiggle‐maps and nine sources are detected in the A2218 850‐μm image. Three of these sources are identified as images of a single background source with an unlensed flux of 0.8 mJy. Further, two single‐imaged sources also have unlensed fluxes <2 mJy, below the blank‐field confusion limit. In this ultradeep map, the individual sources detected resolve nearly all of the extragalactic background light at 850 μm, and the deep data allow to put an upper limit of 44 sources arcmin −2 to 0.2 mJy at 850 μm.