Exploring the Extremes: Characterizing a New Population of Old and Cold Brown Dwarfs

Meisner, Aaron M. and Leggett, S. K. and Logsdon, Sarah E. and Schneider, Adam C. and Tremblin, Pascal and Phillips, Mark (2023) Exploring the Extremes: Characterizing a New Population of Old and Cold Brown Dwarfs. The Astronomical Journal, 166 (2). p. 57. ISSN 0004-6256

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Abstract

Mapping out the populations of thick disk and halo brown dwarfs is important for understanding the metallicity dependence of low-temperature atmospheres and the substellar mass function. Recently, a new population of cold and metal-poor brown dwarfs has been discovered, with Teff ≲ 1400 K and metallicity ≲−1 dex. This population includes what may be the first known "extreme T-type subdwarfs" and possibly the first Y-type subdwarf, WISEA J153429.75−104303.3. We have conducted a Gemini YJHK/Ks photometric follow-up campaign targeting potentially metal-poor T and Y dwarfs, utilizing the GNIRS and Flamingos-2 instruments. We present 14 near-infrared photometric detections of eight unique targets: six T subdwarf candidates, one moderately metal-poor Y dwarf candidate, and one Y subdwarf candidate. We have obtained the first-ever ground-based detection of the highly anomalous object WISEA J153429.75−104303.3. The F110W − J color of WISEA J153429.75−104303.3 is significantly bluer than that of other late T and Y dwarfs, indicating that WISEA J153429.75−104303.3 has an unusual spectrum in the 0.9–1.4 μm wavelength range which encompasses the J-band peak. Our J-band detection of WISEA J153429.75−104303.3 and corresponding model comparisons suggest a subsolar metallicity and temperature of 400–550 K for this object. JWST spectroscopic follow-up at near-infrared and mid-infrared wavelengths would allow us to better understand the spectral peculiarities of WISEA J153429.75−104303.3, assess its physical properties, and conclusively determine whether or not it is the first Y-type subdwarf.

Item Type: Article
Subjects: Science Global Plos > Physics and Astronomy
Depositing User: Unnamed user with email support@science.globalplos.com
Date Deposited: 15 Nov 2023 07:31
Last Modified: 15 Nov 2023 07:31
URI: http://ebooks.manu2sent.com/id/eprint/2116

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