Streblyanska, A.; Aguado-Barahona, A.; Ferragamo, A.; Barrena, R.; Rubiño-Martín, J. A.; Tramonte, D.; Genova-Santos, R. T.; Lietzen, H.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 628, id.A13, 13 pp.
Fecha de publicación:
8
2019
Revista
Número de citas
12
Número de citas referidas
10
Descripción
Aims: The second catalogue of Planck Sunyaev-Zeldovich (SZ)
sources, hereafter PSZ2, is the largest sample of galaxy clusters
selected through their SZ signature in the full sky. At the time of
publication, 21% of these objects had no known counterpart at other
wavelengths. Using telescopes at the Canary Island observatories, we
conducted the long-term observational programme 128-MULTIPLE-16/15B
(hereafter LP15), a large and complete optical follow-up campaign of all
the unidentified PSZ2 sources in the northern sky, with declinations
above -15° and no correspondence in the first Planck catalogue PSZ1.
The main aim of LP15 is to validate all those SZ cluster candidates, and
to contribute to the characterization of the actual purity and
completeness of full Planck SZ sample. In this paper, we describe the
full programme and present the results of the first year of
observations. Methods: The LP15 programme was awarded 44
observing nights, spread over two years in three telescopes at the Roque
de los Muchachos Observatory. The full LP15 sample comprises 190
previously unidentified PSZ2 sources. For each target, we performed deep
optical imaging and spectroscopy. Our validation procedure combined this
optical information with SZ emission as traced by the publicly available
Planck Compton y-maps. The final classification of the new galaxy
clusters as optical counterparts of the SZ signal is established
according to several quantitative criteria based on the redshift,
velocity dispersion, and richness of the clusters. Results: This
paper presents the detailed study of 106 objects out of the LP15 sample,
corresponding to all the observations carried out during the first year
of the programme. We confirmed the optical counterpart for 41 new PSZ2
sources, 31 of them being validated using also velocity dispersion based
on our spectroscopic information. This is the largest dataset of newly
confirmed PSZ2 sources without any previous optical information. All the
confirmed counterparts are rich structures (i.e. they show high velocity
dispersion), and are well aligned with the nominal Planck coordinates
(i.e. ˜70% of them are located at less than 3' distance). In
total, 65 SZ sources are classified as unconfirmed, 57 of them being due
to the absence of an optical over-density, and eight of them due to a
weak association with the observed SZ decrement. Most of the sources
with no optical counterpart are located at low galactic latitudes and
present strong galactic cirrus in the optical images, the dust
contamination being the most probable explanation for their inclusion in
the PSZ2 catalogue.
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