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Expanding the Y Dwarf Census with Spitzer Follow-up of the Coldest CatWISE Solar Neighborhood Discoveries

Meisner, Aaron M. and Caselden, Dan and Kirkpatrick, J. Davy and Marocco, Federico and Gelino, Christopher R. and Cushing, Michael C. and Eisenhardt, Peter R. M. and Wright, Edward L. and Faherty, Jacqueline K. and Koontz, Renata and Marchese, Elijah J. and Khalil, Mohammed and Fowler, John W. and Schlafly, Edward F. (2020) Expanding the Y Dwarf Census with Spitzer Follow-up of the Coldest CatWISE Solar Neighborhood Discoveries. Astrophysical Journal, 889 (2). Art. No. 74. ISSN 1538-4357. doi:10.3847/1538-4357/ab6215.

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We present Spitzer 3.6 and 4.5 μm follow-up of 170 candidate extremely cool brown dwarfs newly discovered via the combination of Wide-field Infrared Survey Explorer (WISE) and NEOWISE imaging at 3–5 μm. CatWISE, a joint analysis of archival WISE and NEOWISE data, has improved upon the motion measurements of AllWISE by leveraging a >10× time baseline enhancement, from 0.5 yr (AllWISE) to 6.5 yr (CatWISE). As a result, CatWISE motion selection has yielded a large sample of previously unrecognized brown dwarf candidates, many of which have archival detections exclusively in the WISE 4.6 μm (W2) channel, suggesting that they could be both exceptionally cold and nearby. Where these objects go undetected in WISE W1 (3.4 μm), Spitzer can provide critically informative detections at 3.6 μm. Of our motion-confirmed discoveries, 17 have a best-fit Spitzer [3.6]–[4.5] color most consistent with spectral type Y. It is likely that CWISEP J144606.62–231717.8 (μ ≈ 1.”3 yr⁻¹) is the reddest, and therefore potentially coldest, member of our sample with a very uncertain [3.6]–[4.5] color of 3.71 ± 0.44 mag. We also highlight our highest proper-motion discovery, WISEA J153429.75–104303.3, with μ ≈ 2.”7 yr⁻¹. Given that the prior list of confirmed and presumed Y dwarfs consists of just 27 objects, the Spitzer follow-up presented in this work has substantially expanded the sample of identified Y dwarfs. Our new discoveries thus represent significant progress toward understanding the bottom of the substellar mass function, investigating the diversity of the Y dwarf population, and selecting optimal brown dwarf targets for James Webb Space Telescope spectroscopy.

Item Type:Article
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URLURL TypeDescription Paper
Meisner, Aaron M.0000-0002-1125-7384
Caselden, Dan0000-0001-7896-5791
Kirkpatrick, J. Davy0000-0003-4269-260X
Marocco, Federico0000-0001-7519-1700
Cushing, Michael C.0000-0001-7780-3352
Wright, Edward L.0000-0001-5058-1593
Faherty, Jacqueline K.0000-0001-6251-0573
Schlafly, Edward F.0000-0002-3569-7421
Additional Information:© 2020 The American Astronomical Society. Received 2019 October 17; revised 2019 November 25; accepted 2019 November 27; published 2020 January 28. We wish to thank the anonymous referee. We thank Nicholas Cross for assistance with compiling archival UKIRT/VISTA detections. This research was partially carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. CatWISE is funded by NASA under Proposal No. 16-ADAP16-0077 issued through the Astrophysics Data Analysis Program and uses data from the NASA-funded WISE and NEOWISE projects. A.M.M. acknowledges support from Hubble Fellowship HST-HF2-51415.001-A. F.M. is supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by the Universities Space Research Association under contract with NASA. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Based in part on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Facilities: Spitzer(IRAC) - Spitzer Space Telescope satellite, WISE/NEOWISE - , Gemini(FLAMINGOS-2) - , Hale(WIRC) - Palomar Observatory's 5.1m Hale Telescope, UKIRT(WFCAM) - United Kingdom Infrared Telescope, VISTA(VIRCAM) - , 2MASS. - Software: XGBoost (Chen & Guestrin 2016), MOPEX (Makovoz & Khan 2005; Makovoz & Marleau 2005), WiseView (Caselden et al. 2018).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51415.001-A
NASA Postdoctoral ProgramUNSPECIFIED
Subject Keywords:Brown dwarfs; Y dwarfs; Solar neighborhood; T dwarfs; Proper motions
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Brown dwarfs (185); Y dwarfs (1827); Solar neighborhood (1509); T dwarfs (1679); Proper motions (1295)
Record Number:CaltechAUTHORS:20200128-145716977
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Official Citation:Aaron M. Meisner et al 2020 ApJ 889 74
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100976
Deposited By: Tony Diaz
Deposited On:28 Jan 2020 23:07
Last Modified:16 Nov 2021 17:58

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