J/AJ/161/42 Volume-limited sample of cool dwarfs. I. L0-T8 dwarfs (Best+, 2021)
A volume-limited sample of ultracool dwarfs.
I. Construction, space density, and a gap in the L/T transition.
Best W.M.J., Liu M.C., Magnier E.A., Dupuy T.J.
<Astron. J., 161, 42 (2021)>
=2021AJ....161...42B 2021AJ....161...42B
ADC_Keywords: Stars, brown dwarf; Stars, L-type; Stars, T-type; Spectral types;
Photometry, infrared; Parallaxes, trigonometric
Keywords: Brown dwarfs ; L dwarfs ; T dwarfs ; Stellar atmospheres ;
Stellar evolution ; Stellar evolutionary models ; Close binary stars ;
Wide binary stars ; Stellar colors ; Infrared photometry
Abstract:
We present a new volume-limited sample of L0-T8 dwarfs out to 25pc
defined entirely by parallaxes, using our recent measurements from
UKIRT/WFCAM along with Gaia DR2 and literature parallaxes. With 369
members, our sample is the largest parallax-defined volume-limited
sample of L and T dwarfs to date, yielding the most precise space
densities for such objects. We find the local L0-T8 dwarf population
includes 5.5%±1.2% young objects (≲200Myr) and 2.6%±1.6%
subdwarfs, as expected from recent studies favoring representative
ages ≲4Gyr for the ultracool field population. This is also the first
volume-limited sample to comprehensively map the transition from L to
T dwarfs (spectral types ∼L8-T4). After removing binaries, we identify
a previously unrecognized, statistically significant (>4.4σ) gap
∼0.5mag wide in (J-K)MKO colors in the L/T transition, i.e., a lack
of such objects in our volume-limited sample, implying a rapid phase
of atmospheric evolution. In contrast, the most successful models of
the L/T transition to date-the "hybrid" models of Saumon &
Marley-predict a pileup of objects at the same colors where we find a
deficit, demonstrating the challenge of modeling the atmospheres of
cooling brown dwarfs. Our sample illustrates the insights to come from
even larger parallax-selected samples from the upcoming Legacy Survey
of Space and Time by the Vera Rubin Obsevatory.
Description:
Best et al. (2020, J/AJ/159/257, Best20) used United Kingdom Infra-Red
Telescope / Wild Field Camera (UKIRT/WFCAM) to obtain parallaxes for
348 L0-T8 dwarfs. Additionally, we searched the literature for all
spectroscopically confirmed objects in Best20's spectral type and
decl. ranges that had parallax measurements with errors <20%,
including parallaxes from Gaia DR2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 188 369 Our volume-limited 25pc sample of L0-T8 dwarfs
refs.dat 88 195 References used
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
II/359 : The VISTA Hemisphere Survey (VHS) catalog DR4.1 (McMahon+, 2013)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/364 : VIRAC. The VVV Infrared Astrometric Catalogue (Smith+, 2019)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/414/279 : Faintest stars (Tinney, 1993)
J/ApJS/94/749 : RI photometry of cool dwarfs (Kirkpatrick+ 1994)
J/PASP/109/849 : Probing the LHS Catalog (Gizis+ 1997)
J/A+A/338/1066 : Optical Spectra of DENIS Brown Dwarf Candidate (Tinney+,1998)
J/A+A/353/958 : New proper motions in 0<RA<7h, -63<DE←32° (Scholz+,2000)
J/A+A/380/590 : 30 DENIS late-M dwarfs between 15 and 30pc (Phan-bao+, 2001)
J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002)
J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
J/AJ/126/1526 : IR photometry of ultracool dwarfs (Bouy+, 2003)
J/AJ/126/2487 : T dwarfs in the southern hemisphere (Burgasser+, 2003)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/AJ/125/3302 : HST binary very low mass stars and brown dwarfs (Gizis+,2003)
J/AJ/127/2856 : Brown dwarfs in the 2MASS Survey (Burgasser+, 2004)
J/AJ/127/3553 : JHK photometry & spectroscopy for L & T dwarfs (Knapp+, 2004)
J/AJ/128/463 : A preliminary 20pc census from NLTT catalogue (Reid+, 2004)
J/A+A/421/643 : New nearby stars in the LEHPMS (Reyle+, 2004)
J/A+A/441/653 : 32 DENIS nearby red dwarfs (Crifo+, 2005)
J/A+A/435/363 : Southern Infrared Proper Motion Survey (Deacon+, 2005)
J/other/ARA+A/43.195 : L and T dwarf stars (Kirkpatrick, 2005)
J/A+A/440/1061 : Southern red high proper motion objects (Lodieu+, 2005)
J/PASP/117/676 : LHS faint proper-motion stars (Reid+, 2005)
J/ApJ/637/1067 : Near-IR spectral classification of T dwarfs (Burgasser+,2006)
J/AJ/131/2722 : New L and T dwarfs from the SDSS (Chiu+, 2006)
J/MNRAS/373/781 : JHK photometry of faint standard stars (Leggett+, 2006)
J/PASP/118/659 : RI photometry of 2MASS late M and L dwarfs (Liebert+, 2006)
J/ApJ/645/676 : Spatial distribution of brown dwarfs in Taurus (Luhman+,2006)
J/AJ/132/891 : Binaries among nearby L dwarfs (Reid+, 2006)
J/MNRAS/373/705 : Optical spectro. of high proper motion stars (Reyle+, 2006)
J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)
J/A+A/468/163 : Sample of low mass stars with mu>0.1"/yr (Deacon+, 2007)
J/AJ/134/1162 : 11 new T dwarfs in 2MASS (Looper+, 2007)
J/AJ/133/2258 : Activity and kinematics of ultracool dwarfs (Schmidt+, 2007)
J/ApJ/689/1295 : Li test implications for brown dwarfs (Kirkpatrick+, 2008)
J/ApJ/676/1281 : L and T dwarfs in 2MASS/SDSS (Metchev+, 2008)
J/MNRAS/383/831 : New DENIS nearby L and late-M dwarfs (Phan-Bao+, 2008)
J/AJ/136/1290 : Ultracool dwarfs from the 2MASS (Reid+, 2008)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/AJ/137/1 : Proper motions & astrometry late-type dwarfs (Faherty+, 2009)
J/A+A/493/L27 : Parallaxes of 10 ultracool subdwarfs (Schilbach+, 2009)
J/ApJ/699/649 : Young M dwarfs within 25pc. I. (Shkolnik+, 2009)
J/A+A/497/619 : New ultra-cool dwarfs from SDSS and 2MASS (Zhang+, 2009)
J/ApJ/710/1142 : SpeX spectroscopy of low mass binaries. I. (Burgasser+, 2010)
J/A+A/510/A99 : Epsilon Indi Ba and Bb IR spectra (King+, 2010)
J/ApJS/190/100 : NIR proper motion survey using 2MASS (Kirkpatrick+, 2010)
J/ApJ/710/1627 : Mid-IR photometry of cold brown dwarfs (Leggett+, 2010)
J/A+A/522/A112 : i'z' photometry of L5 & later dwarf candidates (Reyle+, 2010)
J/AJ/139/1808 : Colors and kinematics of SDSS L dwarfs (Schmidt+, 2010)
J/A+A/512/A37 : Velocities of 43 nearby L dwarfs (Seifahrt+, 2010)
J/AJ/142/77 : New T dwarfs identified in Pan-STARRS 1 (Deacon+, 2011)
J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
J/AJ/144/62 : Tertiary companions to close spectro. binaries (Allen+, 2012)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/ApJ/752/56 : BDKP. III. Parallaxes for 70 ultracool dwarfs (Faherty+,2012)
J/MNRAS/427/3280 : Ultra-cool dwarfs low Galactic latitudes (Folkes+, 2012)
J/ApJ/753/156 : T/Y brown dwarfs with WISE photometry (Kirkpatrick+, 2012)
J/A+A/545/A85 : LHS1070 photometry and spectroscopy (Rajpurohit+, 2012)
J/MNRAS/433/457 : 76 T dwarfs from the UKIDSS LAS (Burningham+, 2013)
J/MNRAS/430/1171 : Sub-stellar birth rate from UKIDSS (Day-Jones+, 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/794/143 : New SpeX Observations of M7-L6 Dwarfs (Bardalez+, 2014)
J/ApJ/794/159 : Statistical analysis of exoplanet surveys (Brandt+, 2014)
J/ApJ/792/119 : Companions to nearby stars from Pan-STARRS 1 (Deacon+, 2014)
J/ApJ/783/122 : AllWISE motion survey (Kirkpatrick+, 2014)
J/ApJ/787/126 : WISE reduced proper motions and spectral types (Luhman+,2014)
J/AJ/147/34 : SpeX library of L-type dwarfs (Schneider+, 2014)
J/MNRAS/454/593 : Young moving groups in solar neighbourhood (Bell+, 2015)
J/ApJ/814/118 : L/T transition dwarfs search PS1 & WISE. II. (Best+, 2015)
J/ApJS/216/7 : Planets Around Low-Mass Stars (PALMS). IV. (Bowler+, 2015)
J/ApJ/810/158 : M,L,T dwarfs fundamental parameters & SEDs (Filippazzo+,2015)
J/ApJS/219/33 : BANYAN. VII. Candidate YMG members from BASS (Gagne+, 2015)
J/MNRAS/449/3651 : L and T dwarfs from UKIDSS LAS (Marocco+, 2015)
J/AJ/149/158 : The BUD sample. I. L dwarf activity sample (Schmidt+, 2015)
J/ApJS/225/10 : Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)
J/ApJ/833/96 : Hawaii IR parallax program. II. Ultracool dwarfs (Liu+, 2016)
J/MNRAS/455/357 : 2MASS J18212815+1414010 field stars (Sahlmann+, 2016)
J/ApJ/817/112 : NEOWISE/AllWISE high proper motion objects (Schneider+, 2016)
J/AJ/154/147 : Astrometry&photometry late-type dwarfs&subdwarfs (Dahn+,2017)
J/MNRAS/468/3499 : Partially resolved binaries in PS1 data (Deacon+, 2017)
J/ApJS/231/15 : Astro. monitoring of ultracool dwarf binaries (Dupuy+, 2017)
J/AJ/154/112 : NIR spectroscopy of new L & T dwarf candidates (Kellogg+,2017)
J/MNRAS/465/4723 : Log of SALT-RSS observations (Koen+, 2017)
J/ApJS/234/1 : Catalog of M, L, & T dwarfs from PS1 3π Survey (Best+,2018)
J/AJ/155/34 : Analysis of the NIR spectra neighboring L dwarfs (Cruz+, 2018)
J/ApJ/862/138 : BANYAN. XIII. Nearby young assoc. with Gaia DR2 (Gagne+, 2018)
J/ApJ/867/109 : Spitzer observations of Y and T dwarfs (Martin+, 2018)
J/AJ/158/187 : Confirmed members of nearby young moving groups (Baron+, 2019)
J/AJ/158/182 : Discoveries from NEOWISE proper motion survey (Greco+, 2019)
J/ApJS/240/19 : Parallaxes of late-T and Y dwarfs (Kirkpatrick+, 2019)
J/AJ/158/13 : The first 300 stars observed by the GPIES (Nielsen+, 2019)
J/AJ/159/257 : Hawaii IR parallax program. IV. L0-T8 BDs UKIRT (Best+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 27 A27 --- Object Object designation
29- 34 F6.3 pc Dist [5.34/24.9] Distance
36- 40 F5.3 pc e_Dist [0.002/4.1] Uncertainty in Distance
42- 47 F6.2 mas plx [40.1/187.3] Parallax
49- 52 F4.2 mas e_plx [0.03/7.6] Uncertainty in Parallax
54- 63 A10 --- SpT-opt Optical spectral type (1)
65- 74 A10 --- SpT-nir NIR spectral type (1)
76- 77 A2 --- Flag Flag (2)
79- 79 I1 --- f_Ymag [0/1]? Flag on Ymag (3)
81- 86 F6.3 mag Ymag [12.71/20.14]? MKO Y band magnitude
88- 92 F5.3 mag e_Ymag [0.002/0.5]? Uncertainty in Ymag
94- 94 I1 --- f_Jmag [0/2]? Flag on Jmag (3)
96-101 F6.3 mag Jmag [11.64/19.64]? MKO J band magnitude
103-107 F5.3 mag e_Jmag [0.001/0.5]? Uncertainty in Jmag
109-109 I1 --- f_Hmag [0/2]? Flag on Hmag (3)
111-116 F6.3 mag Hmag [11.01/19.7]? MKO H band magnitude
118-122 F5.3 mag e_Hmag [0.001/0.3]? Uncertainty in Hmag
124-124 I1 --- f_Kmag [0/2]? Flag on Kmag (3)
126-131 F6.3 mag Kmag [10.43/19.89]? MKO K band magnitude
133-137 F5.3 mag e_Kmag [0.001/0.4]? Uncertainty in Kmag
139-145 A7 --- r_Object Reference(s) for Discovery
147-153 A7 --- r_plx Reference(s) for Parallax
155-161 A7 --- r_SpT Reference(s) for Spectral type(s)
163-176 A14 --- r_Flag Reference(s) for Flag
178-188 A11 --- r_Phot Reference(s) for photometry
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Note (1): β, γ, and δ indicate classes of increasingly low
gravity based on optical (Kirkpatrick+, 2005, J/other/ARA+A/43.195;
Cruz+, 2009AJ....137.3345C 2009AJ....137.3345C) or near-infrared (Gagne+, 2015, J/ApJS/219/33;
Cruz+, 2018, J/AJ/155/34) spectra. fld-g indicates near-infrared
spectral signatures of field-age gravity, int-g indicates intermediate
gravity, and vl-g indicates very low gravity
(Allers & Liu, 2013ApJ...772...79A 2013ApJ...772...79A).
Note (2): Flags as follows:
B = binary (presented here as a single unresolved source); 44 occurrences
C = companion (resolved) to another star or brown dwarf; 27 occurrences
Y = young (≲200 Myr); 22 occurrences
S = subdwarf; 3 occurrences
Note (3): Flags as follows:
0 = Y(MKO), J(MKO), H(MKO), and K(MKO) photometry observed with UKIRT/WFCAM
or other instruments
1 = synthetic photometry (Section 2.5)
2 = photometry converted from 2MASS into the MKO system using M(Ks,2MASS)
and the polynomials of Dupuy+, 2017, J/ApJS/231/15.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Ref [1/195] Reference number
5- 29 A25 --- Autor Reference first autor
31- 49 A19 --- BIB Reference BIBcode
51- 66 A16 --- Cat Reference catalog
68- 88 A21 --- Note Comment
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 03-Mar-2021