A SPHEREx Pipeline and Spectral Library for Ultracool Dwarfs
Abstract
We present a Python spectrophotometry extraction tool tailored for fast-moving point sources detected in the SPHEREx mission, and use it to construct a set of 0.75-5.0 m low-resolution () spectrophotometry data products based on the SPHEREx Quick Release 2 (QR2) for a set of 6003 L0-Y1 ultracool dwarfs: 2050 known ultracool dwarfs, 3008 known photometric ultracool dwarf candidates, and 947 newly identified ultracool dwarfs. This work more than doubles the number of ultracool dwarfs with spectroscopy, from 3449 to 7402. We provide SPHEREx templates for each spectral subtype and a set of tools to assign automated spectral types. The QR2 data release generates spectrophotometry with an average signal-to-noise per spectral channel above 10 for most objects with WISE W2 magnitudes of 14.0 mag and brighter. The compiled data set is made available publicly at https://mocadb.ca, where new spectral compilations from future data releases will also be made available as they are published. These new data provide a significant increase in the number of substellar objects for which the 2.4-5.0 m window is now accessible, making it possible to probe important molecular chemistry of key CNOS-bearing species for the coolest brown dwarfs. We flag 2668 ultracool dwarfs as candidate young brown dwarfs, 250 as candidate subdwarfs, and 865 as possibly otherwise peculiar for future investigation. The SPIFF library presented here opens the doors to efficient confirmation of candidate substellar objects and follow-up studies of population-level atmospheric properties of cold brown dwarfs.
Cite
@article{arxiv.2604.22012,
title = {A SPHEREx Pipeline and Spectral Library for Ultracool Dwarfs},
author = {Jonathan Gagné and Jacqueline K. Faherty and Azul Ruiz Diaz and Louis-Philippe Coulombe and Thomas P. Bickle and Adam C. Schneider and J. Davy Kirkpatrick and Marc J. Kuchner and Aaron M. Meisner and Dan Caselden and Adam J. Burgasser and Sarah Casewell and Easton J. Honaker and Frank Kiwy and Federico Marocco and Daniella C. Bardalez Gagliuffi and Nikolaj Stevnbak Andersen and Lizzeth Ruiz Arroyo and Bruce Baller and Paul Beaulieu and John Bell and Martin Bilsing and Troy K. Bohling and Guillaume Colin and Giovanni Colombo and Sam Deen and Alexandru Dereveanco and Kevin Dixon and Hugo A. Durantini Luca and Deiby Flores and Christoph Franck and Christopher Fulvi and Michael Gallmann and Jean Marc Gantier and Konstantin Glebov and Léopold Gramaize and Leslie K. Hamlet and Ken Hinckley and Kevin Jablonski and Peter A. Jałowiczor and Martin Kabatnik and Peter Kasprowitz and K Ly and David W. Martin and Naoufel Marzak and Alexander McColgan and Neil J. McEwan and Marianne N. Michaels and William Pendrill and Stéphane Perlin and Ben Pumphrey and James Rabe and Henry Raway and Walter Ruben Robledo and David Roser and Animesh Roy and Arttu Sainio and Vincent Schindler and Manfred Schonau and Jö rg Schümann and Karl Selg-Mann and Andrea Serio and Patrick Smith and Andres Stenner and Christopher Tanner and Melina Thévenot and Vinod Thakur and Mayahuel Torres Guerrero and Maurizio Ventura and Nikita V. Voloshin and Jim Walla and Zbigniew Wȩdracki and Bailey Weyandt and Breck Wilhite and Spartacus Zitouni},
journal= {arXiv preprint arXiv:2604.22012},
year = {2026}
}
Comments
Accepted for publication in the Astrophysical Journal. 32 pages, 14 figures, 4 tables, 3 complete long tables in online material