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Published January 2014 | Published + Submitted
Journal Article Open

The Next Generation Virgo Cluster Survey-Infrared (NGVS-IR). I. A New Near-Ultraviolet, Optical, and Near-Infrared Globular Cluster Selection Tool

Abstract

The NGVS-IR project (Next Generation Virgo Cluster Survey-Infrared) is a contiguous, near-infrared imaging survey of the Virgo cluster of galaxies. It complements the optical wide-field survey of Virgo (NGVS). In its current state, NGVS-IR consists of K_s -band imaging of 4 deg^2 centered on M87 and J- and K_s -band imaging of ~16 deg^2 covering the region between M49 and M87. We present observations of the central 4 deg^2 centered on Virgo's core region. The data were acquired with WIRCam on the Canada-France-Hawaii Telescope, and the total integration time was 41 hr distributed over 34 contiguous tiles. A survey-specific strategy was designed to account for extended galaxies while still measuring accurate sky brightness within the survey area. The average 5σ limiting magnitude is K_s = 24.4 AB mag, and the 50% completeness limit is K_s = 23.75 AB mag for point-source detections, when using only images with better than 0."7 seeing (median seeing 0."54). Star clusters are marginally resolved in these image stacks, and Virgo galaxies with µ_K_s ≃ 24.4 AB mag arcsec^(–2) are detected. Combining the K_s data with optical and ultraviolet data, we build the uiK_s color-color diagram, which allows a very clean color-based selection of globular clusters in Virgo. This diagnostic plot will provide reliable globular cluster candidates for spectroscopic follow-up campaigns, needed to continue the exploration of Virgo's photometric and kinematic substructures, and will help the design of future searches for globular clusters in extragalactic systems. We show that the new uiK_s diagram displays significantly clearer substructure in the distribution of stars, globular clusters, and galaxies than the gzK_s diagram—the NGVS + NGVS-IR equivalent of the BzK diagram that is widely used in cosmological surveys. Equipped with this powerful new tool, future NGVS-IR investigations based on the uiK_s diagram will address the mapping and analysis of extended structures and compact stellar systems in and around Virgo galaxies.

Additional Information

© 2014 American Astronomical Society. Received 2013 August 22; accepted 2013 October 31; published 2013 December 11. Based on observations obtained with WIRCam, a joint project of Canada–France–Hawaii Telescope (CFHT), Taiwan, Korea, Canada, France, and the CFHT, which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. This research was supported by CONICYT through Gemini–CONICYT Project 32100022, FONDECYT Regular Project 1121005, FONDECYT Postdoctoral Fellowship Project 3130750, the FONDAP Center for Astrophysics (15010003), the BASAL Center for Astrophysics and Associated Technologies (PFB-06), and the French Agence Nationale de la Recherche (ANR) Grant Programme Blanc VIRAGE (ANR10-BANC-0506-01). R.P.M. and A.L. acknowledge support from the Scientific Council of Strasbourg University. A.L. is grateful for the hospitality and financial support during her stay at the Instituto de Astrofísica of Pontificia Universidad Catόlica de Chile, which was funded by the UMI International Academic Exchange Fund. E.W.P. acknowledges support from the National Natural Science Foundation of China (grant 11173003) and from the Laboratoire International Associé "ORIGINS." C.L. acknowledges support from the National Natural Science Foundation of China (grant 11203017). Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, at the Canada–France–Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work is based in part on data obtained as part of the UKIRT Infrared Deep Sky Survey (found on the UKIRT site). This research has made use of the VizieR catalogue access tool and the Aladin plot tool at CDS, Strasbourg, France. We thank Sebastien Foucaud for providing a version of the SWarp software that includes the sigma-clipping rejection method. The authors acknowledge useful discussions with Simon Angel, Sibilla Perina, Ryan Quadri, Alvio Renzini, Mirko Simunovic, and Jin-Cheng Yu. Facilities: CFHT (WIRCam, MegaCam)

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Submitted - 1311.0873v1.pdf

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August 22, 2023
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October 25, 2023