Beyond the Local Volume. I. Surface Densities of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields. (arXiv:2110.07672v4 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Aganze_C/0/1/0/all/0/1">Christian Aganze</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Burgasser_A/0/1/0/all/0/1">Adam J Burgasser</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Malkan_M/0/1/0/all/0/1">Mathew Malkan</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Theissen_C/0/1/0/all/0/1">Christopher A Theissen</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Arevalo_R/0/1/0/all/0/1">Roberto A Tejada Arevalo</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Hsu_C/0/1/0/all/0/1">Chih-Chun Hsu</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Gagliuffi_D/0/1/0/all/0/1">Daniella C Bardalez Gagliuffi</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Ryan_R/0/1/0/all/0/1">Russell E Ryan Jr</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Holwerda_B/0/1/0/all/0/1">Benne Holwerda</a> (6) ((1) University of California, San Diego, (2) University of California, Los Angeles, (3) Princeton University, Princeton, (4) American Museum of Natural History, NY (5) Space Telescope Science Institute, Baltimore, (6) University of Louisville, Louisville)
Ultracool dwarf stars and brown dwarfs provide a unique probe of large-scale
Galactic structure and evolution; however, until recently spectroscopic samples
of sufficient size, depth, and fidelity have been unavailable. Here, we present
the identification of 164 M7–T9 ultracool dwarfs in 0.6~deg$^2$ of deep,
low-resolution, near-infrared spectroscopic data obtained with the Hubble Space
Telescope Wide Field Camera 3 instrument as part of the WFC3 Infrared
Spectroscopic Parallel Survey and the 3D-HST survey. We describe the
methodology by which we isolate ultracool dwarf candidates from over 200,000
spectra, and show that selection by machine learning classification is superior
to spectral index-based methods in terms of completeness and contamination. We
use the spectra to accurately determine classifications and spectrophotometric
distances, the latter reaching to ~2 kpc for L dwarfs and ~400pc for T dwarfs.
Ultracool dwarf stars and brown dwarfs provide a unique probe of large-scale
Galactic structure and evolution; however, until recently spectroscopic samples
of sufficient size, depth, and fidelity have been unavailable. Here, we present
the identification of 164 M7–T9 ultracool dwarfs in 0.6~deg$^2$ of deep,
low-resolution, near-infrared spectroscopic data obtained with the Hubble Space
Telescope Wide Field Camera 3 instrument as part of the WFC3 Infrared
Spectroscopic Parallel Survey and the 3D-HST survey. We describe the
methodology by which we isolate ultracool dwarf candidates from over 200,000
spectra, and show that selection by machine learning classification is superior
to spectral index-based methods in terms of completeness and contamination. We
use the spectra to accurately determine classifications and spectrophotometric
distances, the latter reaching to ~2 kpc for L dwarfs and ~400pc for T dwarfs.
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