The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs. (arXiv:2011.11616v1 [astro-ph.SR])

The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs. (arXiv:2011.11616v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kirkpatrick_J/0/1/0/all/0/1">J. Davy Kirkpatrick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gelino_C/0/1/0/all/0/1">Christopher R. Gelino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Faherty_J/0/1/0/all/0/1">Jacqueline K. Faherty</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Meisner_A/0/1/0/all/0/1">Aaron M. Meisner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caselden_D/0/1/0/all/0/1">Dan Caselden</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schneider_A/0/1/0/all/0/1">Adam C. Schneider</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marocco_F/0/1/0/all/0/1">Federico Marocco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cayago_A/0/1/0/all/0/1">Alfred J. Cayago</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smart_R/0/1/0/all/0/1">R. L. Smart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eisenhardt_P/0/1/0/all/0/1">Peter R. Eisenhardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuchner_M/0/1/0/all/0/1">Marc J. Kuchner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wright_E/0/1/0/all/0/1">Edward L. Wright</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cushing_M/0/1/0/all/0/1">Michael C. Cushing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Allers_K/0/1/0/all/0/1">Katelyn N. Allers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gagliuffi_D/0/1/0/all/0/1">Daniella C. Bardalez Gagliuffi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burgasser_A/0/1/0/all/0/1">Adam J. Burgasser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gagne_J/0/1/0/all/0/1">Jonathan Gagne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Logsdon_S/0/1/0/all/0/1">Sarah E. Logsdon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martin_E/0/1/0/all/0/1">Emily C. Martin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ingalls_J/0/1/0/all/0/1">James G. Ingalls</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lowrance_P/0/1/0/all/0/1">Patrick J. Lowrance</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abrahams_E/0/1/0/all/0/1">Ellianna S. Abrahams</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aganze_C/0/1/0/all/0/1">Christian Aganze</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gerasimov_R/0/1/0/all/0/1">Roman Gerasimov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzales_E/0/1/0/all/0/1">Eileen C. Gonzales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hsu_C/0/1/0/all/0/1">Chih-Chun Hsu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamraj_N/0/1/0/all/0/1">Nikita Kamraj</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kiman_R/0/1/0/all/0/1">Rocio Kiman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rees_J/0/1/0/all/0/1">Jon Rees</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Theissen_C/0/1/0/all/0/1">Christopher Theissen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ammar_K/0/1/0/all/0/1">Kareem Ammar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Andersen_N/0/1/0/all/0/1">Nikolaj Stevnbak Andersen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beaulieu_P/0/1/0/all/0/1">Paul Beaulieu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Colin_G/0/1/0/all/0/1">Guillaume Colin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Elachi_C/0/1/0/all/0/1">Charles A. Elachi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goodman_S/0/1/0/all/0/1">Samuel J. Goodman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gramaize_L/0/1/0/all/0/1">Leopold Gramaize</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hamlet_L/0/1/0/all/0/1">Leslie K. Hamlet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hong_J/0/1/0/all/0/1">Justin Hong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jonkeren_A/0/1/0/all/0/1">Alexander Jonkeren</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Khalil_M/0/1/0/all/0/1">Mohammed Khalil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martin_D/0/1/0/all/0/1">David W. Martin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pendrill_W/0/1/0/all/0/1">William Pendrill</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pumphrey_B/0/1/0/all/0/1">Benjamin Pumphrey</a>, et al. (8 additional authors not shown)

We present final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs.
We combine these with prior studies to build a list of 525 known L, T, and Y
dwarfs within 20 pc of the Sun, 38 of which are presented here for the first
time. Using published photometry and spectroscopy as well as our own follow-up,
we present an array of color-magnitude and color-color diagrams to further
characterize census members, and we provide polynomial fits to the bulk trends.
Using these characterizations, we assign each object a $T_{rm eff}$ value and
judge sample completeness over bins of $T_{rm eff}$ and spectral type. Except
for types $ge$ T8 and $T_{rm eff} <$ 600K, our census is statistically
complete to the 20-pc limit. We compare our measured space densities to
simulated density distributions and find that the best fit is a power law
($dN/dM propto M^{-alpha}$) with $alpha = 0.6{pm}0.1$. We find that the
evolutionary models of Saumon & Marley correctly predict the observed magnitude
of the space density spike seen at 1200K $< T_{rm eff} <$ 1350K, believed to
be caused by an increase in the cooling timescale across the L/T transition.
Defining the low-mass terminus using this sample requires a more statistically
robust and complete sample of dwarfs $ge$Y0.5 and with $T_{rm eff} <$ 400K.
We conclude that such frigid objects must exist in substantial numbers, despite
the fact that few have so far been identified, and we discuss possible reasons
why they have largely eluded detection.

http://arxiv.org/icons/sfx.gif