New Galactic star clusters discovered in the disc area of the VVVX survey

Creators: Borissova, J.; Ivanov, V. D.; Lucas, P. W.; Kurtev, R.; Alonso-Garcia, J.; Ramírez Alegría, S.; Minniti, D.; Froebrich, D.; Hempel, M.; Medina, N.; Chené, A.-N.; Kuhn, M. A.

Abstract

The 'VISTA Variables in the Vía Láctea eXtended (VVVX)' ESO Public Survey is a near-infrared photometric sky survey that covers nearly 1700 deg2 towards the Galactic disc and bulge. It is well-suited to search for new open clusters, hidden behind dust and gas. The pipeline processed and calibrated KS-band tile images of 40 per cent of the disc area covered by VVVX was visually inspected for stellar overdensities. Then, we identified cluster candidates by examination of the composite JHKS colour images. The colour-magnitude diagrams of the cluster candidates are constructed. Whenever possible the Gaia DR2 parameters are used to calculate the mean proper motions, radial velocities, reddening and distances. We report the discovery of 120 new infrared clusters and stellar groups. Approximately half of them (47 per cent) are faint, compact, highly reddened, and they seem to be associated with other indicators of recent star formation, such as nearby Young Stellar Objects, Masers, H II regions or bubbles. The preliminary distance determinations allow us to trace the clusters up to 4.5 kpc, but most of the cluster candidates are centred at 2.2 kpc. The mean proper motions of the clusters show that in general they follow the disc motion of the Galaxy.

Additional Information

© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) Accepted 2018 August 28. Received 2018 August 28; in original form 2018 January 31. We gratefully acknowledge data from the ESO Public Survey programme ID 198.B-2004 taken with the VISTA telescope, and products from the Cambridge Astronomical Survey Unit (CASU). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Support is provided by the Ministry for the Economy, Development and Tourism, Programa Iniciativa Cientica Milenio grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). JB and RK thank ESO for the financial support during their 2018 January visit. ANC's work is supported by the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., on behalf of the international Gemini partnership of Argentina, Brazil, Canada, Chile, and the United States of America. SRA thanks the support by the FONDECYT Iniciación project No. 11171025 and the CONICYT + PAI 'Concurso Nacional Inserción de Capital Humano Avanzado en la Academia 2017' project PAI 79170089. JA-G also acknowledges support by FONDECYT Iniciación 11150916. MH acknowledges support by the BASAL Centre for Astrophysics and Associated Technologies (CATA) through grant PFB-06. We thank anonymous referee for useful comments and suggestions.

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