A3COSMOS A3GOODSS: Continuum Source Catalogues and Multi-band Number Counts
arxiv(2024)
摘要
Galaxy submillimetre number counts are a fundamental measurement in our
understanding of galaxy evolution models. Most early measurements are obtained
via single-dish telescopes with substantial source confusion, whereas recent
interferometric observations are limited to small areas. We used a large
database of ALMA continuum observations to accurately measure galaxy number
counts in multiple (sub)millimetre bands, thus bridging the flux density range
between single-dish surveys and deep interferometric studies. We continued the
Automated Mining of the ALMA Archive in the COSMOS Field project (A3COSMOS) and
extended it with observations from the GOODS-South field (A3GOODSS). The
database consists of 4,000 pipeline-processed continuum images from the public
ALMA archive, yielding 2,050 unique detected sources. To infer galaxy number
counts, we constructed a method to reduce the observational bias inherent to
targeted pointings that dominate the database. This method comprises a
combination of image selection, masking, and source weighting. The effective
area was calculated by accounting for inhomogeneous wavelengths, sensitivities,
and resolutions and for spatial overlap between images. We tested and
calibrated our method with simulations. We obtained the first number counts
derived in a consistent and homogeneous way in four different ALMA bands
covering a relatively large area. The results are consistent with number counts
from the literature within the uncertainties. We extended the available depth
in ALMA Band 4 by 0.4 dex with respect to previous studies. In Band 7, at the
depth of the inferred number counts, 40
resolved into discrete sources. This fraction, however, decreases with
wavelength, reaching 4
models of dusty galaxy evolution, and find a good agreement within the
uncertainties.
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