The Brown Dwarf Kinematics Project (BDKP). V. Radial and Rotational Velocities of T Dwarfs from Keck/NIRSPEC High-resolution Spectroscopy

Hsu, Chih-Chun; Burgasser, Adam J.; Theissen, Christopher A.; Gelino, Christopher R.; Birky, Jessica; Diamant, Sharon J. M.; Gagliuffi, Daniella Bardalez; Aganze, Christian; Blake, Cullen H.; Faherty, Jacqueline K.

doi:10.3847/1538-4365/ac1c7d

Cited by 38 publications

(32 citation statements)

References 251 publications

(307 reference statements)

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“…In this case, there is evidence that the local population of L dwarfs is significantly contaminated by older, thick disk sources, and Hsu et al ( 2021) report a smaller thin disk L dwarf dispersion, σ W = 15.3 ± 0.3 km s −1 which is still higher than our estimate of σ W = 11.8 +2.0 −1.2 km s −1 for our overall L dwarf sample. We find agreement between our median estimate of σ W = 12.7 +4.6 −2.2 km s −1 for T dwarfs and the local measurement of σ W = 13.3 ± 0.4 km s −1 by Hsu et al (2021), albeit with substantial uncertainties in our value due to small number statistics.…”

Section: Velocity Dispersionssupporting

confidence: 81%

“…For L0-L4 dwarfs, our estimate of 2.0 +0.6 −0.4 Gyr is substantially lower than the (likely contaminated) 6.5±0.4 Gyr kinematic age inferred by Burgasser et al (2015), and our age estimate for all L dwarfs, 2.1 +0.9 −0.5 Gyr, is also significantly lower than the kinematic age of thin disk L dwarfs of 4.2 ± 0.3 Gyr from Hsu et al (2021). Our estimate of 2.4 +2.4 −0.8 Gyr for T dwarfs is lower than but formally in agreement with the kinematic age of 3.5 ± 0.3 Gyr from Hsu et al (2021), albeit again with significant uncertainties.…”

Section: Agescontrasting

confidence: 75%

“…The lack of proper motion information for the vast majority of the sample also prevents us from assessing the thick disk contribution through kinematics (Bensby et al 2003). Hsu et al (2021) finds that the fraction of intermediate thin-disk/thick disk objects for UCDs ranges from 3-8% based on the 3D-kinematics of the nearby (d<20 pc) UCD sample. However, these data are limited to the local volume and we expect to see a larger fraction of thick disk stars at larger distances and high galactic latitudes.…”

Section: Contamination From the Thick Disk Populationmentioning

confidence: 99%

“…The challenge in using ultracool dwarfs for Galactic Archaeology is their intrinsic faintness. UCD population studies based on wide-field imaging surveys have been largely limited to the nearby Solar Neighborhood (d 100 pc), and have focused on measuring the local luminosity function and velocity dispersions (Cruz et al 2007b;Metchev et al 2008;Reyle et al 2010;Bardalez Gagliuffi et al 2019;Kirkpatrick et al 2019Kirkpatrick et al , 2021Burgasser et al 2015;Hsu et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Because UCDs are a mixture of long-lived, stable stars and cooling brown dwarfs, their ages, dispersions, and scaleheights are all predicted to show complex trends with temperature depending on formation and evolutionary history (Burgasser 2004;Ryan et al 2017). While kinematic trends can be discerned from the local sample (Zapatero Osorio et al 2007;Blake et al 2010;Burgasser et al 2015;Hsu et al 2021), variations in scaleheights requires a well-characterized, large sample of UCDs out to kpc distances, including low temperature L, T, and Y dwarfs.…”

Section: Introductionmentioning

confidence: 99%

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Beyond the Local Volume II: Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields

Aganze,

Burgasser,

Malkan

et al. 2022

Preprint

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Ultracool dwarfs represent a significant proportion of stars in the Milky Way, and deep samples of these sources have the potential to constrain the formation history and evolution of low-mass objects in the Galaxy. Until recently, spectral samples have been limited to the local volume (d<100pc). Here, we analyze a sample of 164 spectroscopically-characterized ultracool dwarfs identified by Aganze et al. in the Hubble Space Telescope WFC3 Infrared Spectroscopic Parallel (WISP) Survey and 3D-HST. We model the observed luminosity function using population simulations to place constraints on scaleheights, vertical velocity dispersions and population ages as a function of spectral type. Our star counts are consistent with a power-law mass function and constant star formation history for ultracool dwarfs, with vertical scaleheights 249 +48 −61 pc for late M dwarfs, 153 +56 −30 pc for L dwarfs, and 175 +149 −56 pc for T dwarfs. Using spatial and velocity dispersion relations, these scaleheights correspond to disk population ages of 3.6 +0.8 −1.0 Gyr for late M dwarfs, 2.1 +0.9 −0.5 Gyr for L dwarfs, and 2.4 +2.4 −0.8 Gyr for T dwarfs, which are consistent with prior simulations that predict that L-type dwarfs are on average a younger and less dispersed population. There is an additional 1-2 Gyr systematic uncertainty on these ages due to variances in age-velocity relations. We use our population simulations to predict the UCD yield in the JWST PASSAGES survey, a similar and deeper survey to WISPS and 3D-HST, and find that it will produce a comparably-sized UCD sample, albeit dominated by thick disk and halo sources.

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Section: Velocity Dispersionssupporting

confidence: 81%

Section: Agescontrasting

confidence: 75%

Section: Contamination From the Thick Disk Populationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Beyond the Local Volume II: Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields

Aganze,

Burgasser,

Malkan

et al. 2022

Preprint

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Physical properties and trigonometric distance of the peculiar dwarf WISE J181005.5−101002.3

Lodieu

Osorio

Martín

et al. 2022

A&A

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Aims. Our goal is to characterise the physical properties of the metal-poor brown dwarf population. In particular, we focus on the recently discovered peculiar dwarf WISE1810055−1010023. Methods. We collected optical iz and near-infrared J-band imaging on multiple occasions over 1.5 years to derive accurate trigonometric parallax and proper motion of the metal-depleted ultra-cool dwarf candidate WISE J1810055−1010023. We also acquired low-resolution optical spectroscopy (0.6−1.0 µm) and new infrared (0.9−1.3 µm) spectra of WISE J1810055−1010023 that were combined with our photometry, other existing data from the literature and our trigonometric distance to determine the object's luminosity from the integration of the observed spectral energy distribution covering from 0.6 through 16 µm. We compared the full optical and infrared spectrum with state-of-the-art atmosphere models to further constrain its effective temperature, surface gravity and metallicity. Results. WISE J1810055−1010023 is detected in the iz bands with AB magnitudes of i = 23.871±0.104 and z = 20.147±0.083 mag in the Panoramic Survey Telescope and Rapid Response System (PanSTARRS) system. It does not show any obvious photometric variability beyond 0.1−0.2 mag in any of the z-and J-band filters. The very red z − J ≈ 2.9 mag colour is compatible with an ultra-cool dwarf nature. Fitting for parallax and proper motion, we measure a trigonometric parallax of 112.5 +8.1 −8.0 mas for WISE J1810055−1010023, placing the object at only 8.9 +0.7 −0.6 pc, about three times closer than previously thought. We employed Monte Carlo methods to estimate the error on the parallax and proper motion. The object's luminosity was determined at log L/L = −5.78 ± 0.11 dex. From the comparison to atmospheric models, we infer a likely metallicity of [Fe/H] ≈ −1.5 and an effective temperature cooler than 1000 K. The estimated luminosity and temperature of this object are below the known substellar limit. Despite its apparent low metallicity, we derive space motions that are more typical of the old disc than the halo of the Milky Way. We confirm that WISE J1810055−1010023 has an ultra-cool temperature and belongs to a new class of objects with no known spectral counterparts among field L-and T-type dwarfs. Conclusions. WISE J1810055−1010023 is a very special substellar object and represents a new addition to the 10 pc sample. The optical to near-infrared spectra show strong features due to water vapour and H 2 collision induced absorption. Our trigonometric distance has strong implications on the density of metal-poor brown dwarfs in the solar vicinity, which may be higher than that of metal-poor stars.

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Reconnaissance ultracool spectra in theEuclidDeep Fields

Zhang,

Lodieu,

Martín

2024

A&A

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The Euclid spacecraft has been launched and will carry out a deep survey benefiting the discovery and characterisation of ultracool dwarfs (UCDs), especially in the Euclid Deep Fields (EDFs), which the telescope will scan repeatedly throughout its mission. The photometric and spectroscopic standards in the EDFs are important benchmarks, crucial for the classification and characterisation of new UCD discoveries and for the calibration of the mission itself. We aim to provide a list of photometric UCD candidates and collect near-infrared reconnaissance spectra for M, L, and T-type UCDs in the EDFs as future $Euclid$ UCD references. In EDF North, we cross-matched public optical and infrared surveys with certain photometric criteria to select UCDs. In EDF Fornax and EDF South, we used photometrically classified samples from the literature. We also include UCDs identified by Gaia DR2. We selected seven UCD targets with different spectral types from the lists and obtained low-resolution 0.9--2.5 mu m spectra of them using GTC/EMIR and the VLT/X-shooter. We also selected a young, bright L dwarf near EDF Fornax to test the coherence of these two facilities. We included one extra T dwarf in EDF North with its published $J$-band spectrum. We retrieved a list of 92 (49, 231) M, 33 (29, 115) L, and one (0, 2) T dwarf candidates in EDF North, Fornax, and South, respectively. They are provided to guide future UCD discoveries and characterisations by $Euclid$. In total, we collected near-infrared spectra for nine UCDs, including two M types, three L types, and four T types in or close to the three EDFs. The Euclidised spectra show consistency in their spectral classification, which demonstrates that slitless Euclid spectroscopy will recover the spectral types with high fidelity for UCDs, both in the EDFs and in the wide survey. We also demonstrate that Euclid will be able to distinguish different age groups of UCDs.

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The Brown Dwarf Kinematics Project (BDKP). V. Radial and Rotational Velocities of T Dwarfs from Keck/NIRSPEC High-resolution Spectroscopy

Cited by 38 publications

References 251 publications

Beyond the Local Volume II: Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields

Beyond the Local Volume II: Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields

Physical properties and trigonometric distance of the peculiar dwarf WISE J181005.5−101002.3

Reconnaissance ultracool spectra in theEuclidDeep Fields

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