On the multiplicity of ALMA Compact Array counterparts of far-infrared bright quasars

Hatziminaoglou, E.; Farrah, D.; Humphreys, E.; Manrique, A.; Pérez-Fournon, I.; Pitchford, L. K.; Salvador-Solé, E.; Wang, L.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 4, p.4974-4990

Advertised on:
11
2018
Number of authors
8
IAC number of authors
1
Citations
13
Refereed citations
12
Description
We present ALMA Atacama Compact Array (ACA) 870 μm continuum maps of 28 infrared-bright SDSS quasars with Herschel/SPIRE detections at redshifts 2-4, the largest such sample ever observed with ALMA. The ACA detections are centred on the SDSS coordinates to within 1 ″ for about 80 per cent of the sample. Larger offsets indicate that the far-infrared (FIR) emission detected by Herschel might come from a companion source. The majority of the objects (˜70 per cent) have unique ACA counterparts within the SPIRE beam down to 3″-4″ resolution. Only 30 per cent of the sample shows clear evidence for multiple sources with secondary counterparts contributing to the total 870 μm flux within the SPIRE beam to at least 25 per cent. We discuss the limitations of the data based on simulated pairs of point-like sources at the resolution of the ACA and present an extensive comparison of our findings with recent works on the multiplicities of sub-millimetre galaxies. We conclude that, despite the coarse resolution of the ACA, our data support the idea that, for a large fraction of FIR-bright quasars, the sub-mm emission comes from single sources. Our results suggest that, on average, optically bright quasars with strong FIR emission are not triggered by early-stage mergers but are, instead, together with their associated star formation rates, the outcome of either late-stage mergers or secular processes.
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Formation and Evolution of Galaxies: Observations in Infrared and other Wavelengths
This IAC research group carries out several extragalactic projects in different spectral ranges, using space as well as ground-based telescopes, to study the cosmological evolution of galaxies and the origin of nuclear activity in active galaxies. The group is a member of the international consortium which built the SPIRE instrument for the
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