J/AJ/155/34 Analysis of the NIR spectra of neighboring L dwarfs (Cruz+, 2018)
Meeting the cool neighbors.
XII. An optically anchored analysis of the near-infrared spectra of L dwarfs.
Cruz K.L., Nunez A., Burgasser A.J., Abrahams E., Rice E.L., Reid I.N.,
Looper D.
<Astron. J., 155, 34 (2018)>
=2018AJ....155...34C 2018AJ....155...34C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; Stars, brown dwarf ; Stars, L-type ;
Spectral types ; Photometry, infrared
Keywords: brown dwarfs - infrared: stars - standards - stars: late-type -
stars: low-mass - techniques: spectroscopic
Abstract:
Discrepancies between competing optical and near-infrared (NIR)
spectral typing systems for L dwarfs have motivated us to search for a
classification scheme that ties the optical and NIR schemes together,
and addresses complexities in the spectral morphology. We use new and
extant optical and NIR spectra to compile a sample of 171 L dwarfs,
including 27 low-gravity β and γ objects, with spectral
coverage from 0.6-2.4 µm. We present 155 new low-resolution NIR
spectra and 19 new optical spectra. We utilize a method for analyzing
NIR spectra that partially removes the broad-band spectral slope and
reveals similarities in the absorption features between objects of the
same optical spectral type. Using the optical spectra as an anchor, we
generate near-infrared spectral average templates for L0-L8,
L0-L4γ, and L0-L1β type dwarfs. These templates reveal that
NIR spectral morphologies are correlated with the optical types. They
also show the range of spectral morphologies spanned by each spectral
type. We compare low-gravity and field-gravity templates to provide
recommendations on the minimum required observations for credibly
classifying low-gravity spectra using low-resolution NIR data. We use
the templates to evaluate the existing NIR spectral standards and
propose new ones where appropriate. Finally, we build on the work of
Kirkpatrick et al. to provide a spectral typing method that is tied to
the optical and can be used when only H or K band data are available.
The methods we present here provide resolutions to several long-standing
issues with classifying L dwarf spectra and could also be the foundation
for a spectral classification scheme for cloudy exoplanets.
Description:
Our campaign to obtain spectroscopy of L dwarfs was initiated as part
of our effort to complete the 20 pc census of nearby ultracool dwarfs
using 2MASS. Photometric selection criteria were used to identify
candidate nearby ultracool dwarfs in the 2MASS catalog (Cat. II/246).
The selection criteria and sample creation are described extensively
in Papers V (Cruz et al. 2003, J/AJ/126/2421), IX (Cruz et al., 2007,
J/AJ/133/439), and X (Reid et al. 2008, J/AJ/136/1290). Candidate objects
were targeted for far-red optical and/or near-infrared spectroscopic
follow-up to obtain spectral types and photometric distances. During
these observing runs, we also targeted confirmed nearby M and L dwarfs
from the literature that lacked optical and/or NIR spectra.
The far-red optical observations were obtained with several different
instruments but we restrict the analysis in this paper to objects with
NIR data obtained with the SpeX spectrograph (Rayner et al.
2003PASP..115..362R 2003PASP..115..362R) on the 3 m NASA Infrared Telescope Facility using
the low-resolution prism mode. We have combined new SpeX prism data,
new optical data, and extant spectra from the literature to create a
sample of 171 L dwarfs with both far-red optical (6000-9000 Å) and
low-resolution SpeX prism spectra (0.85-2.4 µm), which we refer to
collectively as the "optical-NIR sample".
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 135 19 New Far-Red Optical Observations
table2.dat 35 155 New Near-Infrared IRTF SpeX Prism Observations
table3.dat 286 101 L Dwarfs Included in the Field Gravity Template
Sample
table4.dat 286 41 Normal L Dwarfs Excluded from the Field Gravity
Template Sample
table5.dat 286 26 Low-gravity L Dwarfs Included in the Low-gravity
Template Sample
table10.dat 34 17 Near-Infrared IRTF SpeX Prism Spectra of
Galaxies
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/123/2806 : Nearby stars in the NLTT catalogue (Reid+, 2002)
J/AJ/123/2822 : Photometry of southern NLTT stars (Reid+, 2002)
J/AJ/123/2828 : Spectroscopy of northern NLTT stars (Cruz+, 2002)
J/AJ/126/1526 : IR photometry of ultracool dwarfs (Bouy+, 2003)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/AJ/126/2449 : Nearby ultracool dwarfs in galactic plane (Reid+, 2003)
J/AJ/126/3007 : Spectroscopy of faint red NLTT dwarfs (Reid+, 2003)
J/AJ/127/3553 : JHK photometry and spectroscopy for L and T dwarfs
(Knapp+, 2004)
J/AJ/128/463 : A preliminary 20pc census from the NLTT catalogue
(Reid+, 2004)
J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)
J/AJ/133/2825 : Star beyond the NLTT catalog (Reid+, 2007)
J/AJ/136/1290 : Ultracool dwarfs from the 2MASS (Reid+, 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/139/1808 : Colors and kinematics of SDSS L dwarfs (Schmidt+, 2010)
J/MNRAS/404/1817 : 2MASS/SDSS data for 806 ultracool dwarfs (Zhang+, 2010)
J/AJ/147/94 : Solar neighborhood. XXXII. L and M dwarfs (Dieterich+, 2014)
J/ApJ/794/143 : New SpeX Observations of M7-L6 Dwarfs (Bardalez+, 2014)
J/ApJ/810/158 : M,L,T dwarfs fundamental parameters and SEDs
(Filippazzo+, 2015)
J/AJ/154/112 : NIR spectroscopy of new L and T dwarf candidates
(Kellogg+, 2017)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 F4.2 --- FS [1.1/1.9] Figure Set 1 element number
6- 21 A16 --- 2MASS 2MASS identifier of optical L dwarf
(HHMMSSss+DDMMSSs)
22- 23 A2 --- Comp [AB ] Component designation
25- 30 A6 --- Tel Telescope (Keck I, Clay)
32- 37 A6 --- Inst Instrument (LRIS, LDSS-3)
39- 49 A11 "date" Date UT date of observation
51- 61 A11 --- SpType Derived optical spectral type
63- 81 A19 --- r_SpType Reference bibcode for SpType
83- 86 A4 --- SpType1 Previous spectral type, no 1
88-106 A19 --- r_SpType1 Reference bibcode for SpType1
108-115 A8 --- SpType2 Previous spectral type, no 2
117-135 A19 --- r_SpType2 Reference bibcode for SpType2
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name Target name (2MASS identifier or other name)
26- 35 A10 "date" Date UT date of observation
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[345].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Target name (2MASS identifier or other name)
(1)
27- 51 A25 --- OName Other name (not in Table 4)
53- 58 F6.3 mag Jmag [11.759/16.789] 2MASS J band magnitude
60- 64 F5.3 mag e_Jmag [0.019/0.15] Uncertainty in Jmag
66- 70 F5.3 mag J-Ks [0.912/2.483] 2MASS J-Ks color index
72- 76 F5.3 mag e_J-Ks [0.029/0.18] Uncertainty in J-Ks
78- 88 A11 --- SpType Optical spectral type
90 A1 --- n_SpType [bcd] Note on SpType (not in Table 5) (2)
92-123 A32 --- r_SpType Reference for SpType
125-143 A19 --- Bibcode1 Bibcode of the reference for SpType
145-176 A32 --- RefSpeX SpeX Prism reference
178-196 A19 --- Bibcode2 Bibcode of the reference for SpeX Prism
198-245 A48 --- Ref Other reference(s) (3)
247-286 A40 --- Bibcode3 Bibcode of the other reference(s)
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Note (1): Templates generated using spectra of objects in Table 3 are shown in
Figure 6. Objects in Table 4 were excluded from the templates and are shown
in Figure 7. Templates generated using spectra of objects in Table 5 are shown
in Figures 8 and 9.
These data are available as data behind the figures and from the BDNYC
Database.
Note (2): Note as follows:
b = Originally typed as L3 in Cruz et al. (2007, J/AJ/133/439) but reanalysis
of same data resulted in a revised type of L4;
c = Originally typed as L6: in Reid et al. (2008, J/AJ/136/1290) but
reanalysis of the same slightly noisy spectrum resulted in a revised type
of L7:;
d = Spectral type based on analysis of spectrum from Scholz et al.
(2009A&A...494..949S 2009A&A...494..949S).
Note (3): References listed are not exhaustive and pertain to discovery and
spectral data not listed in previous columns.
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Byte-by-byte Description of file: table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- FS Figure Set A1 element number (A1.1 to A1.17)
7- 22 A16 --- 2MASS 2MASS identifier of likely galaxy (HHMMSSss+DDMMSSs)
24- 34 A11 "date" Date UT date of observation
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Reid & Cruz, Paper I 2002AJ....123.2806R 2002AJ....123.2806R, Cat. J/AJ/123/2806
Reid et al., Paper II 2002AJ....123.2822R 2002AJ....123.2822R, Cat. J/AJ/123/2822
Cruz & Reid, Paper III 2002AJ....123.2828C 2002AJ....123.2828C, Cat. J/AJ/123/2828
Reid et al., Paper IV 2003AJ....125..354R 2003AJ....125..354R
Cruz et al., Paper V 2003AJ....126.2421C 2003AJ....126.2421C, Cat. J/AJ/126/2421
Reid, Paper VI 2003AJ....126.2449R 2003AJ....126.2449R, Cat. J/AJ/126/2449
Reid et al., Paper VII 2003AJ....126.3007R 2003AJ....126.3007R, Cat. J/AJ/126/3007
Reid et al., Paper VIII 2004AJ....128..463R 2004AJ....128..463R, Cat. J/AJ/128/463
Cruz et al., Paper IX 2007AJ....133..439C 2007AJ....133..439C, Cat. J/AJ/133/439
Reid et al., Paper X 2008AJ....136.1290R 2008AJ....136.1290R, Cat. J/AJ/136/1290
Reid et al., Paper XI 2007AJ....133.2825R 2007AJ....133.2825R, Cat. J/AJ/133/2825
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 14-Sep-2018