A deep near-infrared view of the Ophiuchus galaxy cluster
  Context: The Ophiuchus cluster of galaxies, located at low latitudes in the
direction of the Galactic bulge, has been relatively poorly studied in
comparison with other rich galaxy clusters like Coma, Virgo and Fornax, in
spite of being the 2nd brightest X-ray cluster in the sky. Methods: Deep
near-infrared images and photometry from the VISTA Variables in the V\'ia
L\'actea eXtended survey (VVVX) were used to detect galaxy member candidates of
Ophiuchus cluster up to 2 Mpc from the cD galaxy 2MASX J17122774-2322108 using
the Galdeano et al. criteria to select the galaxies among the foreground
sources. We also perform a morphological visual classification, color-magnitude
diagram and density profiles. Results: We identified 537 candidate galaxy
members of the Ophiuchus cluster up to 2 Mpc from the cD galaxy, increasing 7
times the number of galaxies reported in previous catalogs. In addition, we
performed a morphological classification of these galaxy candidates finding
that the fraction of Ellipticals reaches more than the 60% in the central
region of the cluster. On the other hand the Spirals fraction is lower than the
20% remaining almost constant throughout the cluster. Moreover, we study the
red sequence of galaxy member candidates and use mock catalogs to explore the
density profile of the cluster, finding that the value derived from the mock
catalog towards an overdense region is in agreement with the galaxy excess of
the central zone of the Ophiuchus cluster. Conclusions: Our investigation of
the hidden population of Ophiuchus galaxies underscores the importance of this
cluster as a prime target for future photometric and spectroscopic studies.
Moreover the results of this work highlights the potential of VVVX survey to
study extragalactic objects in the Zone of Avoidance.
