J/MNRAS/480/5447 New L subdwarfs, population properties (Zhang+, 2018)
Primeval very low-mass stars and brown dwarfs.
IV. New L subdwarfs, Gaia astrometry, population properties, and a blue brown
dwarf binary.
Zhang Z.H., Galvez-Ortiz M.C., Pinfield D.J., Burgasser A.J., Lodieu N.,
Jones H.R.A., Martin E.L., Burningham B., Homeier D., Allard F.,
Zapatero Osorio M.R., Smith L.C., Smart R.L., Lopez Marti B., Marocco F.,
Rebolo R.
<Mon. Not. R. Astron. Soc., 480, 5447-5474 (2018)>
=2018MNRAS.480.5447Z 2018MNRAS.480.5447Z (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, spectroscopic ; Stars, brown dwarf ; Stars, peculiar ;
Stars, population II ; Stars, subdwarf
Keywords: binaries: spectroscopic - brown dwarfs - stars: chemically peculiar -
stars: Population II - stars: subdwarfs
Abstract:
We present 27 new L subdwarfs and classify five of them as esdL and 22
as sdL. Our L subdwarf candidates were selected with the UKIRT
Infrared Deep Sky Survey and Sloan Digital Sky Survey. Spectroscopic
follow-up was carried out primarily with the OSIRIS spectrograph on
the Gran Telescopio Canarias. Some of these new objects were followed
up with the X-shooter instrument on the Very Large Telescope. We
studied the photometric properties of the population of known L
subdwarfs using colour-spectral type diagrams and colour-colour
diagrams, by comparison with L dwarfs and main sequence stars, and
identified new colour spaces for L subdwarf selection/study in current
and future surveys. We further discussed the brown dwarf
transition-zone and the observational stellar/substellar boundary. We
found that about one-third of 66 known L subdwarfs are substellar
objects, with two-thirds being very low-mass stars. We also present
the Hertzsprung-Russell diagrams, spectral type-absolute magnitude
corrections, and tangential velocities of 20 known L subdwarfs
observed by the Gaia astrometry satellite. One of our L subdwarf
candidates, ULAS J233227.03+123452.0, is a mildly metal-poor
spectroscopic binary brown dwarf: a ∼L6p dwarf and a ∼T4p dwarf. This
binary is likely a thick disc member according to its kinematics.
Description:
The L subdwarf candidates in our programme were generally selected
from the UKIDSS Large Area Survey (LAS) and the SDSS, following the
selection criteria/procedure described in Paper I (Zhang et al.
2017MNRAS.464.3040Z 2017MNRAS.464.3040Z). In addition two extra candidates without SDSS
detections were selected from a ULAS proper motion catalogue (Smith et
al. 2014MNRAS.437.3603S 2014MNRAS.437.3603S, Cat. J/MNRAS/437/3603). Our programmatic
candidate sample consisted of 64 objects of which five had been
confirmed as L subdwarfs by other studies. We have spectroscopically
followed up the remaining 59 candidates, which has in total resulted
in the confirmation/study of 34 L subdwarfs. Eight of these were
published in Papers I (Zhang et al. 2017MNRAS.464.3040Z 2017MNRAS.464.3040Z) and III
(Zhang et al. 2018MNRAS.479.1383Z 2018MNRAS.479.1383Z), and the remaining 27 are reported
here. Table 1 presents optical and NIR photometry for all known L
subdwarfs, which includes the 34 studied by our programme plus 31 from
elsewhere in the literature. Candidates have been followed up with
optical spectroscopy using the Optical System for Imaging and
low-Resolution Integrated Spectroscopy (OSIRIS; Cepa et al.
2000SPIE.4008..623C 2000SPIE.4008..623C) instrument on the Gran Telescopio Canarias (GTC)
since 2012. Table 2 shows a summary of our GTC spectroscopic
observations.
We have also obtained optical-NIR spectroscopy of five of our
candidates, a known sdL8 subdwarf and three radial velocity standard L
dwarfs using the X-shooter spectrograph (Vernet et al.
2011A&A...536A.105V 2011A&A...536A.105V) on the Very Large Telescope (VLT) since 2014.
Table 3 shows a summary of our VLT spectroscopic observations.
Finally, twenty of 66 known L subdwarfs in Table 1 were observed by
Gaia. Table 9 shows the Gaia astrometry and photometry of these 20 L
subdwarfs. As our UKIDSS-SDSS survey is relatively deep, only two of
our L subdwarfs are in Gaia DR2; UL0753+20 is from this work and ULAS
J134749.79+333601.7 was presented in Paper I.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 109 66 Optical and NIR photometry of L subdwarfs
table2.dat 94 56 Summary of the characteristics of the
spectroscopic observations made with the OSIRIS
on the GTC
table3.dat 91 9 Summary of the characteristics of the
spectroscopic observations made with X-shooter
table4.dat 70 27 Proper motions, distances, and tangential
velocities of our 27 new L subdwarfs
table5.dat 249 1 Properties of a spectral binary UL2332+12
table6.dat 96 22 Photometric properties of new M-L
dwarfs/subdwarfs identified in this work
table7.dat 105 65 PS1 and WISE photometry of L subdwarfs
table9.dat 103 20 Gaia DR2 astrometry and photometry of 20 L
subdwarfs
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Subdwarf name
27 A1 --- n_Name Note on the object's photometry (1)
29- 35 A7 --- SpType Spectral type
36 A1 --- n_SpType [*] Note on SpType (2)
37- 41 F5.2 mag imag ? SDSS i magnitude (SDSSi)
43- 46 F4.2 mag e_imag ? Error on imag
48- 52 F5.2 mag zmag ? SDSS z magnitude (SDSSz)
54- 57 F4.2 mag e_zmag ? Error on zmag
59- 63 F5.2 mag Ymag ? MKO Y-band magnitude
65- 68 F4.2 mag e_Ymag ? Error on Ymag
70- 74 F5.2 mag Jmag MKO J-band magnitude
76- 79 F4.2 mag e_Jmag Error on Jmag
81- 85 F5.2 mag Hmag MKO H-band magnitude
87- 90 F4.2 mag e_Hmag Error on Hmag
92 A1 --- l_Kmag ? Lower limit on Kmag
94- 98 F5.2 mag Kmag MKO K-band magnitude
100-103 F4.2 mag e_Kmag ? Error on Kmag
105-109 A5 --- Ref References (3)
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Note (1): Notes as follows:
b = ATLAS i, z and VHS YJHK photometry
c = ATLAS i, z and VIKING YJH photometry
d = VHS YJK photometry
e = ATLAS i, z photometry
f = VHS JK photometry
The other NIR photometry of objects with Y-band detection are from UKIDSS.
J, H, and K photometry of the other objects without UKIDSS Y-band detection
are converted from 2MASS.
Note (2): * : VVV J12564163-6202039 is an sdL3 subdwarf according to a new
optical-NIR spectrum we obtained with the X-shooter
Note (3): References as follows:
1 = Burgasser et al. (2003ApJ...592.1186B 2003ApJ...592.1186B)
2 = Burgasser et al. (2004AJ....127.2856B 2004AJ....127.2856B, Cat. J/AJ/127/2856)
3 = Burgasser (2004ApJ...614L..73B 2004ApJ...614L..73B)
4 = Burgasser & Kirkpatrick (2006ApJ...645.1485B 2006ApJ...645.1485B)
5 = Burgasser et al. (2007ApJ...657..494B 2007ApJ...657..494B)
6 = Burgasser et al. (2009ApJ...697..148B 2009ApJ...697..148B)
7 = Bowler et al. (2010ApJ...710...45B 2010ApJ...710...45B);
Burningham et al. (2010MNRAS.404.1952B 2010MNRAS.404.1952B);
Schmidt et al. (2010AJ....139.1045S 2010AJ....139.1045S)
8 = Cushing et al. (2009ApJ...696..986C 2009ApJ...696..986C)
9 = Gizis & Harvin (2006AJ....132.2372G 2006AJ....132.2372G)
10 = Kirkpatrick et al. (2010ApJS..190..100K 2010ApJS..190..100K, Cat. J/ApJS/190/100)
11 = Kirkpatrick et al. (2014ApJ...783..122K 2014ApJ...783..122K, Cat. J/ApJ/783/122)
12 = Kirkpatrick et al. (2016ApJS..224...36K 2016ApJS..224...36K, Cat. J/ApJS/224/36)
13 = Lepine et al. (2002ApJ...581L..47L 2002ApJ...581L..47L)
14 = Luhman & Sheppard (2014ApJ...787..126L 2014ApJ...787..126L, Cat. J/ApJ/787/126)
15 = Lodieu et al. (2010ApJ...708L.107L 2010ApJ...708L.107L)
16 = Lodieu et al. (2012A&A...542A.105L 2012A&A...542A.105L)
17 = Lodieu et al. (2017A&A...598A..92L 2017A&A...598A..92L)
18 = Scholz et al. (2004A&A...428L..25S 2004A&A...428L..25S)
19 = Scholz et al. (2004A&A...425..519S 2004A&A...425..519S)
20 = Schneider et al. (2016ApJ...817..112S 2016ApJ...817..112S, Cat. J/ApJ/817/112)
21 = Sivarani et al. (2009ApJ...694L.140S 2009ApJ...694L.140S)
22 = Smith et al. (2018MNRAS.474.1826S 2018MNRAS.474.1826S)
23 = Paper I, Zhang et al. (2017MNRAS.464.3040Z 2017MNRAS.464.3040Z)
24 = Paper II, Zhang et al. (2017MNRAS.468..261Z 2017MNRAS.468..261Z)
25 = Paper III, Zhang et al. (2018MNRAS.479.1383Z 2018MNRAS.479.1383Z)
26 = This work
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name ULAS star name (ULAS JHHMMSS.ss+DDMMSS.s)
26- 34 A9 --- ID Proposal ID
36- 45 A10 "Y:M:D" Date UT observation date
47- 50 F4.2 arcsec Seeing Photometric seeing
52- 55 F4.2 --- Airmass Airmass
57- 61 A5 --- Grism Grism (R500R and R300R grisms cover a
wavelength range of 480-1020nm)
63- 68 A6 --- Tint Integration time (in seconds) (1)
70- 76 A7 --- SpType ? Spectral type
78- 85 A8 --- Std ? Standard star used for spectral flux
calibration
87- 92 A6 --- StdSpType ? Spectral type of the standard star
94 I1 --- r_Std ? Reference of the standard star (2)
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Note (1): A 0.8 arcsec slit used for all observations
Note (2): References as follows:
1 = Bohlin et al. (1995AJ....110.1316B 1995AJ....110.1316B)
2 = Hamuy et al. (1994PASP..106..566H 1994PASP..106..566H, Cat. II/179)
3 = Oke (1974ApJS...27...21O 1974ApJS...27...21O)
4 = Oke (1990AJ.....99.1621O 1990AJ.....99.1621O)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name Star name (1)
26- 32 A7 --- SpType Spectral type
34- 43 A10 "Y:M:D" Date UT observation date
45- 48 F4.2 arcsec Seeing Photometric seeing
50- 53 F4.2 --- Airmass Airmass
55- 61 A7 --- TintVIS Integration time for VIS arm (2)
63- 69 A7 --- TintNIR Integration time for NIR arm (2)
71- 80 A10 --- Tellstd Telluric standard stars (3)
82- 86 A5 --- TellSpType Spectral type on the telluric standard star
88- 91 F4.2 --- AirmTell Airmass for the observation of the telluric
standard star
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Note (1): DENIS-P J025503.3-470049, 2MASS J08354256-0819237, and
DENIS-P J144137.3-4094559 were observed as RV standards.
Note (2): Wavelength ranges for the VIS and NIR arms are 530-1020nm and
990-2480nm. 1.2 arcsec slits are used for both VIS and NIR arms.
Note (3): Telluric corrections were achieved for both VIS and NIR arms using
telluric standards that were observed right after or before our
targets at a very close airmass.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- SName Star ULAS short name (ULHHMM+DD)
11- 14 I4 mas/yr pmRA Proper motion in right ascension
16- 17 I2 mas/yr e_pmRA Error on pmRA
19- 22 I4 mas/yr pmDE Proper motion in declination
24- 25 I2 mas/yr e_pmDE Error on pmDE
27- 29 I3 pc Dist Distance (1)
31- 32 I2 pc E_Dist Upper error on Dist
34- 35 I2 pc e_Dist Lower error on Dist
37- 39 I3 km/s Vtan Tangential velocity
41- 42 I2 km/s E_Vtan Upper error on Vtan
44- 45 I2 km/s e_Vtan Lower error on Vtan
47- 70 A24 --- Name ULAS NAME (ULAS JHHMMSS.ss+DDMMSS.s)
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Note (1): We estimated spectroscopic distances for these 27 new L subdwarfs
based on the relationship between spectral type and H-band absolute
magnitude, which is less sensitive to metallicity/subclass for L
subdwarfs
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name ULAS name (ULAS JHHMMSS.ss+DDMMSS.s)
26- 27 I2 h RAh Right ascension (J2000)
29- 30 I2 min RAm Right ascension (J2000)
32- 36 F5.2 s RAs Right ascension (J2000)
38 A1 --- DE- Declination sign (J2000)
39- 40 I2 deg DEd Declination (J2000)
42- 43 I2 arcmin DEm Declination (J2000)
45- 48 F4.1 arcsec DEs Declination (J2000)
50- 59 A10 "Y:M:D" Date Epoch
61- 65 F5.2 mag imag SDDS i magnitude
67- 70 F4.2 mag e_imag Error on imag
72- 76 F5.2 mag zmag SDDS z magnitude
78- 81 F4.2 mag e_zmag Error on zmag
83- 87 F5.2 mag iP1mag Pan-STARRS i magnitude
89- 92 F4.2 mag e_iP1mag Error on iP1mag
94- 98 F5.2 mag zP1mag Pan-STARRS z magnitude
100-103 F4.2 mag e_zP1mag Error on zP1mag
105-109 F5.2 mag yP1mag Pan-STARRS y magnitude
111-114 F4.2 mag e_yP1mag Error on yP1mag
116-120 F5.2 mag Ymag UKIDSS Y magnitude
122-125 F4.2 mag e_Ymag Error on Ymag
127-131 F5.2 mag Jmag UKIDSS J magnitude
133-136 F4.2 mag e_Jmag Error on Jmag
138-142 F5.2 mag Hmag UKIDSS H magnitude
144-147 F4.2 mag e_Hmag Error on Hmag
149-153 F5.2 mag Kmag UKIDSS K magnitude
155-158 F4.2 mag e_Kmag Error on Kmag
160-164 F5.2 mag W1mag WISE W1 (3.4um) band magnitude
166-169 F4.2 mag e_W1mag Error on W1mag
171-175 F5.2 mag W2mag WISE W2 (4.6um) band magnitude
177-180 F4.2 mag e_W2mag Error on W2mag
182-188 A7 --- SpType Spectral type (from synthesized fit)
190-191 I2 pc Dist Distance (1)
193-194 I2 pc E_Dist Upper error on Dist
196-197 I2 pc e_Dist Lower error on Dist
199-201 I3 mas/yr pmRA Proper motion in right ascension (2)
203-204 I2 mas/yr e_pmRA Error on pmRA (2)
206-209 I4 mas/yr pmDE Proper motion in declination (2)
211-212 I2 mas/yr e_pmDE Error on pmDE (2)
214-216 I3 km/s Vtan Tangential velocity
218-219 I2 km/s E_Vtan Upper error on Vtan
221-222 I2 km/s e_Vtan Lower error on Vtan
224-226 I3 km/s RV Radial velocity (3)
228 I1 km/s e_RV Error on RV
230-232 I3 km/s U U component of space velocity
234-235 I2 km/s e_U Error on U
237-239 I3 km/s V V component of space velocity
241-242 I2 km/s e_V Error on V
244-246 I3 km/s W W component of space velocity
248-249 I2 km/s e_W Error on W
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Note (1): The combined H-band absolute magnitude of an L6+T4 binary is thus
around 12.59mag, suggesting a distance of 58+12-10pc for
UL2332+12 as a binary
Note (2): Proper motions of UL2332+12 are measured from its UKIDSS and PS1
epochs with a baseline of 2.74yr
Note (3): The RV of UL2332+12 was measured from its X-shooter spectrum and an
L9 type RV standard (DENIS-P J025503.3-470049)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name ULAS star name (ULAS JHHMMSS.ss+DDMMSS.s)
26- 30 A5 --- SpType Spectral type
32- 36 F5.2 mag imag SDSS i magnitude
38- 41 F4.2 mag e_imag Error on imag
43- 47 F5.2 mag zmag SDSS z magnitude
49- 52 F4.2 mag e_zmag Error on zmag
54- 58 F5.2 mag Ymag UKIDSS Y magnitude
60- 63 F4.2 mag e_Ymag Error on Ymag
65- 69 F5.2 mag Jmag UKIDSS J magnitude
71- 74 F4.2 mag e_Jmag Error on Jmag
76- 80 F5.2 mag Hmag UKIDSS H magnitude
82- 85 F4.2 mag e_Hmag Error on Hmag
87- 91 F5.2 mag Kmag UKIDSS K magnitude
93- 96 F4.2 mag e_Kmag Error on Kmag
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star Name
27- 48 A22 --- OName PS1 name
50- 54 F5.2 mag iP1mag ? Pan-STARRS i magnitude
56- 59 F4.2 mag e_iP1mag ? Error on iP1mag
61- 65 F5.2 mag zP1mag ? Pan-STARRS z magnitude
67- 70 F4.2 mag e_zP1mag ? Error on zP1mag
72- 76 F5.2 mag yP1mag ? Pan-STARRS y magnitude
78- 81 F4.2 mag e_yP1mag ? Error on yP1mag
83- 87 F5.2 mag W1mag ? WISE W1 (3.4um) band magnitude
89- 92 F4.2 mag e_W1mag ? Error on W1mag
94 A1 --- l_W2mag ? Lower limit on W2mag
96-100 F5.2 mag W2mag ? WISE W2 (4.6um) band magnitude
102-105 F4.2 mag e_W2mag ? Error on W2mag
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star name
27- 45 I19 --- GaiaDR2 Gaia DR2 source identifier
47- 52 F6.2 mas plx Parallax
54- 57 F4.2 mas e_plx Error on plx
59- 66 F8.2 mas/yr pmRA Proper motion in right ascension
68- 71 F4.2 mas/yr e_pmRA Error on pmRA
73- 80 F8.2 mas/yr pmDE Proper motion in declination
82- 85 F4.2 mas/yr e_pmDE Error on pmDE
87- 91 F5.2 mag Gmag Gaia DR2 G-band magnitude
93- 97 F5.2 mag BPmag ? Gaia DR2 BP magnitude
99-103 F5.2 mag RPmag ? Gaia DR2 RP magnitude
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History:
From electronic version of the journal
References:
Zhang et al., Paper I 2017MNRAS.464.3040Z 2017MNRAS.464.3040Z
Zhang et al., Paper II 2017MNRAS.468..261Z 2017MNRAS.468..261Z
Zhang et al., Paper III 2018MNRAS.479.1383Z 2018MNRAS.479.1383Z
(End) Ana Fiallos [CDS] 01-Jun-2022