Aganze, C.

Bardalez Gagliuffi, D.

Birky, J.

Blake, C.

Burgasser, A.

Diamant, S.

Faherty, J.

Gelino, C.

Hsu, C.-C.

Theissen, C.

Leiden University Scholary Publications

Kinematics, rotation, and multiplicity of ultracool dwarfs with high-resolution near-infrared spectroscopyHsu, C.-C.; Burgasser, A.; Theissen, C.; Gelino, C.; Birky, J.; Diamant, S.; ... ; Faherty, J.CitationHsu, C. -C., Burgasser, A., Theissen, C., Gelino, C., Birky, J., Diamant, S., … Faherty, J. (2022).Kinematics, rotation, and multiplicity of ultracool dwarfs with high-resolution near-infraredspectroscopy. Bulletin Of The American Astronomical Society, (6). Retrieved fromhttps://hdl.handle.net/1887/3562738 Version: Publisher's VersionLicense: Creative Commons CC BY 4.0 licenseDownloaded from: https://hdl.handle.net/1887/3562738 Note: To cite this publication please use the final published version (if applicable).Bulletin of the AAS • Vol. 54, Issue 6Kinematics, Rotation, andMultiplicity of UltracoolDwarfs with High-Resolution Near-InfraredSpectroscopyChih-Chun Hsu1 Adam Burgasser2 Christopher Theissen3Christopher Gelino4 Jessica Birky5 Sharon Diamant6Daniella Bardalez Gagliu 7 Christian Aganze1 Cullen Blake8Jacqueline Faherty71UC San Diego, 2University of California, San Diego, 3University of California San Diego,4California Institute of Technology, 5University of Washington, Seattle, 6Leiden Observatory,7American Museum of Natural History, 8University of PennsylvaniaPublished on: Jun 29, 2022URL: https://baas.aas.org/pub/2022n6i208p03License: Creative Commons Attribution 4.0 International License (CC-BY 4.0)Bulletin of the AAS • Vol. 54, Issue 6 Kinematics, Rotation, and Multiplicity of Ultracool Dwarfs with High-Resolution Near-Infrared Spectroscopy2Ultracool dwarfs (UCDs) are the lowest-mass stars and brown dwarfs, with effective temperatures ≤ 3,000 K. Over the past two decades, thousands of UCDs have been discovered through all-sky surveys such as 2MASS and WISE, making it possible to statistically study them as a population. As part of my doctoral thesis, I have analyzed the largest sample of high-resolution near-infrared spectra of ultracool dwarfs to date with Keck/NIRSPEC (archival and observed) and SDSS/APOGEE DR17. I employed a Markov Chain Monte Carlo forward-modeling method to measure precise radial and projected rotational velocities (vsini), quantities which can be used to identify members of nearby young moving groups, confirm low-mass short-period binaries, and study population kinematics and angular momentum evolution. In this talk, I present an analysis of 172 nearby UCDs within 20 pc with 3D kinematics. I confirm that local L dwarfs are more dispersed and have an older kinematic age than late-M and T dwarfs, consistent with previous studies and contrary to theoretical predictions. However, I find that this discrepancy can be resolved by the higher fraction of thick disk members in the local L dwarf population. I further demonstrate that L dwarfs have declining velocity dispersions toward later subtypes, reflecting a higher brown dwarf-to-star ratio through the later sequence; and identify a kinematic break between L4–L6 subtypes which can be attributed to the terminus of stellar main sequence. My rotational analysis indicates that average vsini increases from late-M to T dwarfs, reflecting less angular momentum loss toward later spectral types. I also report the identification of the first two T-type spectroscopic binaries. Combining this sample with recent observations of late-M and L dwarfs with Keck/NIRSPEC, I show how comparison of the kinematic sample to population simulations constrain the local UCD star formation rate, mass function, and hint at potential modifications of evolutionary models. Finally, I summarize the future development for high-resolution spectroscopic surveys and forward-modeling for UCDs in the local sample and beyond.

Kinematics, rotation, and multiplicity of ultracool dwarfs with high-resolution near-infrared spectroscopy

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Kinematics, rotation, and multiplicity of ultracool dwarfs with high-resolution near-infrared spectroscopy

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