J/ApJS/281/49 Brown dwarfs from JWST NIRSpec observations (Tu+, 2025)
A large sample of JWST/NIRSpec brown dwarfs: new distant discoveries.
Tu Z., Wang S., Chen X., Liu J.
<Astrophys. J. Suppl. Ser., 281, 49 (2025)>
=2025ApJS..281...49T 2025ApJS..281...49T
ADC_Keywords: Stars, brown dwarf; Spectra, infrared; Spectral types; Abundances;
Extinction; Stars, ages; Stars, masses; Stars, diameters;
Stars, distances; Models, evolutionary
Keywords: Brown dwarfs ; L dwarfs ; T dwarfs ; Stellar atmospheres ;
Milky Way stellar halo
Abstract:
Brown dwarfs are essential probes of stellar and planetary formation,
yet their low luminosities pose challenges for detection at large
Galactic distances. The James Webb Space Telescope (JWST), with its
unprecedented near-infrared sensitivity, enables the discovery and
characterization of distant substellar objects, including those in the
Milky Way's thick disk and halo. We conducted a systematic search
using over 40,000 publicly available JWST/NIRSpec PRISM/CLEAR spectra
and identified 68 brown dwarfs through spectral template matching and
visual inspection. Among them, 12 are newly identified candidates,
including eight T dwarfs and four M/L dwarfs, most at distances
exceeding 1 kpc. Remarkably, two sources-JWST J001418.22-302223.2 and
JWST J033240.07-274907.8-are found at distances greater than 5kpc,
making them the most distant brown dwarfs within the Milky Way.
Spectral fits were performed using a nested sampling Monte Carlo
algorithm with three model grids: Sonora Elf Owl, LOWZ, and SAND. The
analysis reveals that cloud-free models are unable to reproduce L/T
transition spectra, whereas the SAND model provides a more accurate
representation of cloud effects in metal-poor environments. With the
newly identified distant brown dwarfs, we also investigated the
vertical metallicity gradient of brown dwarfs. Overall, the
metallicities do not show an evident trend with Galactic height |Z|,
due to the limited sample size and the uncertainties in metallicity
measurements.
Description:
We focus our analysis on the JWST/NIRSpec PRISM/CLEAR mode. The
PRISM/CLEAR setting offers low-resolution spectroscopy (R∼100) over
the entire near-infrared wavelength range from 0.6 to 5.3um.
To construct our sample, we retrieved all publicly available stage 3
NIRSpec PRISM/CLEAR spectra from the Mikulski Archive for Space
Telescopes (MAST), as of early 2025 April.
The spectra of the 68 brown dwarfs can be accessed from MAST via
doi:10.17909/hryb-x508.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 274 122 Brown dwarf sample derived parameters
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See also:
V/159 : JADES NIRCam & NIRSpec cat. (DR1-DR3) (Rieke+, 2023)
J/ApJ/637/1067 : NIR spectral classification of T dwarfs (Burgasser+, 2006)
J/ApJS/190/100 : NIR proper motion survey using 2MASS (Kirkpatrick+, 2010)
J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
J/ApJ/753/156 : T/Y brown dwarfs with WISE photometry (Kirkpatrick+, 2012)
J/MNRAS/433/457 : 76 T dwarfs from the UKIDSS LAS (Burningham+, 2013)
J/ApJS/205/6 : T dwarf population revealed by WISE (Mace+, 2013)
J/PASP/125/809 : New nearby M, L, and T dwarfs (Thompson+, 2013)
J/ApJ/782/8 : Spectroscopy of 104 objects in the ONC (Ingraham+, 2014)
J/ApJ/814/118 : L/T dwarfs search with PS1 & WISE. II. (Best+, 2015)
J/ApJS/225/10 : Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)
J/ApJ/889/74 : Spitzer follow-up of Y brown dwarfs (Meisner+, 2020)
J/ApJ/946/43 : Sp. RSG stars in the MCs from APOGEE & Gaia (Wang+, 2023)
J/AJ/168/230 : Phot. of substellar cand. in ONC with JWST (Luhman, 2024)
J/ApJ/975/162 : Sp. of brown dwarf cand. in ONC from JWST (Luhman+, 2024)
J/AJ/167/5 : WISE J085510.83-071442.5 sp. with JWST (Luhman+, 2024)
J/AJ/167/168 : NIRSpec sp. of TWA 28, TWA 27A & TWA 27B (Manjavacas+, 2024)
J/A+A/691/A240 : ASTRODEEP-JWST photometry and redshifts (Merlin+, 2024)
J/ApJS/270/7 : UNCOVER phot. cat. of A2744 with HST+JWST (Weaver+, 2024)
J/MNRAS/542/L126 : Spectra of brown dwarf candidates in the ONC (Luhman, 2025)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 26 A26 --- Name Star name
28- 34 A7 --- SpT Spectral type (1)
36- 37 I2 --- r_SpT [0/26]? Spectral type Reference
(0=This work) (2)
39- 44 A6 --- Model Evolutionary model
46- 46 A1 --- f_Model Flag on Model (3)
48- 51 I4 K Teff [297/3004] Effective temperature
53- 55 I3 K E_Teff [12/345] Upper uncertainty in Teff
57- 59 I3 K e_Teff [12/285] Lower uncertainty in Teff
61- 64 F4.2 [cm/s2] log(g) [2.89/6.0] Log of surface gravity
66- 69 F4.2 [cm/s2] E_log(g) [0.13/1.75] Upper uncertainty in log(g)
71- 74 F4.2 [cm/s2] e_log(g) [0.13/0.88] Lower uncertainty in log(g)
76- 77 A2 --- f_log(g) Flag on log(g) (4)
79- 83 F5.2 [-] [M/H] [-2.04/0.98] Metallicity
85- 88 F4.2 [-] E_[M/H] [0.1/0.38] Upper uncertainty in [M/H]
90- 93 F4.2 [-] e_[M/H] [0.1/0.4] Lower uncertainty in [M/H]
95- 98 F4.2 --- C/O [0.22/0.85]? Carbon-to-oxygen ratio
100-103 F4.2 --- E_C/O [0.11/0.25]? Upper uncertainty in C/O
105-108 F4.2 --- e_C/O [0.11/0.24]? Lower uncertainty in C/O
110-113 F4.2 [cm2/s] log(K) [1.98/9.92]? Eddy diffusion parameter
115-118 F4.2 [cm2/s] E_log(K) [0.52/6.12]? Upper uncertainty in log(K)
120-123 F4.2 [cm2/s] e_log(K) [0.52/4.2]? Lower uncertainty in log(K)
125-129 F5.2 --- a/Fe [-0.03/0.4]? Value of α enhancement
131-134 F4.2 --- E_a/Fe [0.03/0.3]? Upper uncertainty in a/Fe
136-139 F4.2 --- e_a/Fe [0.03/0.11]? Lower uncertainty in a/Fe
141-144 F4.2 mag Av [1.93/7.83]? Extinction
146-149 F4.2 mag E_Av [0.02/1.38]? Upper uncertainty in Av
151-154 F4.2 mag e_Av [0.03/0.54]? Lower uncertainty in Av
156-161 F6.2 [-] log(R2/D2) [-24.93/-18.46] Log of scale factor
163-166 F4.2 [-] E_log(R2/D2) [0.05/0.2] Upper uncertainty in log(R2/D2)
168-171 F4.2 [-] e_log(R2/D2) [0.05/0.2] Lower uncertainty in log(R2/D2)
173-178 F6.2 [-] log(f) [-18.49/-11.51] Log of jitter term
180-183 F4.2 [-] E_log(f) [0.01/0.72] Upper uncertainty in log(f)
185-188 F4.2 [-] e_log(f) [0.01/1.79] Lower uncertainty in log(f)
190-197 F8.1 --- chi2 [1.1/117339.1] Reduced χ-squared
199-204 F6.3 Gyr Age [0.001/10] Stellar age (5)
206-210 F5.3 Gyr E_Age [0.001/6.7] Upper uncertainty in Age
212-216 F5.3 Gyr e_Age [0.001/8.4] Lower uncertainty in Age
218-220 A3 --- f_Age Flag on Age (6)
222-225 F4.1 Mjup Mass [1.0/78.6] Mass (5)
227-230 F4.1 Mjup E_Mass [0.1/57.6] Upper uncertainty in Mass
232-235 F4.1 Mjup e_Mass [0.1/26.9] Lower uncertainty in Mass
237-239 A3 --- f_Mass Flag on Mass (6)
241-244 F4.2 Rjup Rad [0.76/7.92] Radius (5)
246-249 F4.2 Rjup E_Rad [0.01/4.52] Upper uncertainty in Rad
251-254 F4.2 Rjup e_Rad [0.01/2.12] Lower uncertainty in Rad
256-258 A3 --- f_Rad Flag on Rad (6)
260-264 I5 pc Dist [4/15874] Distance (7)
266-269 I4 pc E_Dist [1/6706] Upper uncertainty in Dist
271-274 I4 pc e_Dist [1/6367] Lower uncertainty in Dist
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Note (1): If not otherwise specified, the uncertainty in spectral type from
this work is assumed to be ±1. See Section 5.2 for details.
Note (2): Spectral type Reference:
0 = This work (12 occurrences; see Table 1)
1 = Luhman et al. 2024, J/ApJ/975/162
2 = Tu et al. 2025ApJ...980..230T 2025ApJ...980..230T
3 = Hainline et al. 2024ApJ...975...31H 2024ApJ...975...31H
4 = Gizis et al. 2015ApJ...799..203G 2015ApJ...799..203G
5 = Mace et al. 2013, J/ApJS/205/6
6 = Kirkpatrick et al. 2011, J/ApJS/197/19
7 = Burgasser et al. 2006, J/ApJ/637/1067
8 = Allers & Liu 2013ApJ...772...79A 2013ApJ...772...79A
9 = Kirkpatrick et al. 2012, J/ApJ/753/156
10 = Lucas et al. 2006MNRAS.373L..60L 2006MNRAS.373L..60L
11 = Slesnick et al. 2004ApJ...610.1045S 2004ApJ...610.1045S
12 = Ingraham et al. 2014, J/ApJ/782/8
13 = Riddick et al. 2007MNRAS.381.1077R 2007MNRAS.381.1077R
14 = Best et al. 2015, J/ApJ/814/118
15 = Loutrel et al. 2011ApJ...739...81L 2011ApJ...739...81L
16 = Schneider et al. 2015ApJ...804...92S 2015ApJ...804...92S
17 = Leggett et al. 2015ApJ...799...37L 2015ApJ...799...37L
18 = Thompson et al. 2013, J/PASP/125/809
19 = Meisner et al. 2020, J/ApJ/889/74
20 = Burningham et al. 2011MNRAS.414.3590B 2011MNRAS.414.3590B
21 = Burgasser et al. 2000ApJ...531L..57B 2000ApJ...531L..57B
22 = Tinney et al. 2018ApJS..236...28T 2018ApJS..236...28T
23 = Faherty et al. 2016, J/ApJS/225/10
24 = Cushing et al. 2011ApJ...743...50C 2011ApJ...743...50C
25 = Cushing et al. 2014AJ....147..113C 2014AJ....147..113C
26 = Schneider et al. 2015ApJ...804...92S 2015ApJ...804...92S
Note (3): Flag as follows:
* = The corresponding reduced χ-squared is about an order of magnitude
(i.e., ∼10 times) larger than the minimum reduced χ-squared
obtained among all models for that source. For sources with only a
single model fit, we also mark with an asterisk if the fit appears
unsatisfactory upon visual inspection. The derived parameters from such
models should therefore be interpreted with caution.
Note (4): Flag as follows:
** = Values of the log(g) are considered anomalous/unphysical fits and
should be treated with caution.
Note (5): Derived from Monte Carlo sampling of the evolutionary models using
the fitted Teff and log(g) values.
Note (6): Flag as follows:
*** = More than half of the Monte Carlo samples extend beyond the model
grid boundaries. In such cases, the reported values, as well as the
corresponding distances, should be treated with caution.
Note (7): Obtained by jointly sampling log(R2/D2) and the radii, with the
median (50th percentile) adopted as the final value, and the 16th and
84th percentiles taken as the lower and upper bounds, respectively.
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Jun-2026