J/ApJ/814/118 L/T transition dwarfs search with PS1 & WISE. II. (Best+, 2015)
A search for L/T transition dwarfs with Pan-STARRS1 and WISE.
II. L/T transition atmospheres and young discoveries.
Best W.M.J., Liu M.C., Magnier E.A., Deacon N.R., Aller K.M., Redstone J.,
Burgett W.S., Chambers K.C., Draper P., Flewelling H., Hodapp K.W.,
Kaiser N., Metcalfe N., Tonry J.L., Wainscoat R.J., Waters C.
<Astrophys. J., 814, 118 (2015)>
=2015ApJ...814..118B 2015ApJ...814..118B (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, infrared ; Spectral types ; Stars, late-type ;
Proper motions ; Stars, distances ; Surveys
Keywords: binaries: general; brown dwarfs; stars: atmospheres;
stars: kinematics and dynamics; stars: late-type
Abstract:
The evolution of brown dwarfs from L to T spectral types is one of the
least understood aspects of the ultracool population, partly for lack
of a large, well-defined, and well-characterized sample in the L/T
transition. To improve the existing census, we have searched
∼28000deg2 using the Pan-STARRS1 and Wide-field Infrared Survey
Explorer surveys for L/T transition dwarfs within 25pc. We present 130
ultracool dwarf discoveries with estimated distances ∼9-130pc,
including 21 that were independently discovered by other authors and 3
that were previously identified as photometric candidates.
Seventy-nine of our objects have near-IR spectral types of L6-T4.5,
the most L/T transition dwarfs from any search to date, and we have
increased the census of L9-T1.5 objects within 25pc by over 50%. The
color distribution of our discoveries provides further evidence for
the "L/T gap", a deficit of objects with (J-K)MKO∼0.0-0.5mag in the
L/T transition, and thus reinforces the idea that the transition from
cloudy to clear photospheres occurs rapidly. Among our discoveries are
31 candidate binaries based on their low-resolution spectral features.
Two of these candidates are common proper motion companions to nearby
main sequence stars; if confirmed as binaries, these would be rare
benchmark systems with the potential to stringently test ultracool
evolutionary models. Our search also serendipitously identified 23
late-M and L dwarfs with spectroscopic signs of low gravity implying
youth, including 10 with vl-g or int-g gravity classifications and
another 13 with indications of low gravity whose spectral types or
modest spectral signal-to-noise ratio do not allow us to assign formal
classifications. Finally, we identify 10 candidate members of nearby
young moving groups (YMG) with spectral types L7-T4.5, including three
showing spectroscopic signs of low gravity. If confirmed, any of these
would be among the coolest known YMG members and would help to
determine the effective temperature at which young brown dwarfs cross
the L/T transition.
Description:
We used the new Pan-STARRS1 Survey (PS1; Kaiser et al.
2010SPIE.7733E..0EK) detections through 2012 January cross-matched
with the Wide-field Infrared Survey Explorer (WISE; Wright et al.
2010AJ....140.1868W 2010AJ....140.1868W) All-sky Release using a 3" matching radius. In
Best et al. (2013ApJ...777...84B 2013ApJ...777...84B; Paper I), we presented seven initial
discoveries from our search, all bright L/T transition dwarfs within
15pc. In this paper, we present the complete results of our search,
including 79 total L/T transition dwarfs and 23 young or potentially
young late-M and L dwarfs.
The PS1 3π survey (K. C. Chambers et al. 2016AAS...22732407C) has
obtained an average of ∼12 epochs of imaging in five optical bands
(gP1, rP1, iP1, zP1, yP1) with a 1.8-m wide-field telescope
on Haleakala, Maui, covering the entire sky north of -30°
declination. Imaging began in 2010 May and concluded in 2014 March.
The WISE All-sky Source Catalog (Cutri et al. 2012, II/311) comprises
data taken between 2010 January and August in four mid-infrared bands:
W1 (3.6um), W2 (4.5um), W3 (12um), and W4 (22um).
We searched the UKIDSS Data Release 9 (DR9; Lawrence et al. 2013,
II/319) and VISTA Hemisphere Survey (Cross et al. 2012A&A...548A.119C 2012A&A...548A.119C)
catalogs for JHK photometry of our candidates on the Mauna Kea
Observatories (MKO) filter system. For objects not found in either
survey, we obtained follow-up images using WFCAM on the 3.8m United
Kingdom InfraRed Telescope (UKIRT) as part of the UKIRT Service
Program. Observations took place on multiple nights spanning 2010
September to 2013 December.
We obtained low-resolution near-IR spectra for our 142 candidates
between 2012 July and 2014 January using the NASA IRTF/SpeX
spectrograph (details of our observations are listed in table 3).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 98 142 Pan-STARRS1 and WISE all-sky photometry
table2.dat 97 142 Near-infrared photometry
table3.dat 55 140 IRTF/SpeX observations
table4.dat 69 122 Visual spectral types and kinematics
table8.dat 93 54 *Index-based spectral types from
Allers & Liu (2013ApJ...772...79A 2013ApJ...772...79A)
for M7-L8 objects
table9.dat 100 114 Index-based spectral types from
Burgasser et al. (2006, J/ApJ/637/1067)
for L0-T7 objects
table14.dat 116 10 Candidate members of young moving groups
--------------------------------------------------------------------------------
Note on table8.dat: None of these indices are valid for spectral types later
than L8, so objects with those spectral types are not listed here.
--------------------------------------------------------------------------------
See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
I/298 : LSPM-North Catalog (Lepine+ 2005)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
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/ApJ/798/73 : BANYAN All-Sky Survey (BASS). V. Nearby YMGs (Gagne+, 2015)
J/ApJ/783/121 : BANYAN II. Nearby young assoc. cand. members (Gagne+, 2014)
J/PASP/125/809 : New nearby M, L, and T dwarfs (Thompson+, 2013)
J/ApJS/205/6 : T dwarf population revealed by WISE (Mace+, 2013)
J/ApJ/762/88 : Young stellar kinematic group candidate members (Malo+, 2013)
J/ApJ/758/56 : Young M dwarfs within 25pc. II. Kinematics (Shkolnik+, 2012)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/ApJ/753/156 : T/Y brown dwarfs with WISE photometry (Kirkpatrick+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011)
J/ApJS/190/100 : NIR proper motion survey using 2MASS (Kirkpatrick+, 2010)
J/MNRAS/404/1817 : 2MASS/SDSS data for 806 ultracool dwarfs (Zhang+, 2010)
J/AJ/139/1808 : Colors and kinematics of SDSS L dwarfs (Schmidt+, 2010)
J/ApJ/710/1142 : SpeX spectroscopy of low mass binaries. I. (Burgasser+, 2010)
J/A+A/497/619 : New ultra-cool dwarfs from SDSS and 2MASS (Zhang+, 2009)
J/AJ/137/1 : PMs & astrometry of late-type dwarfs (Faherty+, 2009)
J/AJ/136/1290 : Ultracool dwarfs from the 2MASS (Reid+, 2008)
J/A+A/468/163 : Sample of low mass stars with mu>0.1"/yr (Deacon+, 2007)
J/AJ/133/889 : Faint companions of Hipparcos stars (Lepine+, 2007)
J/AJ/132/891 : Binaries among nearby L dwarfs (Reid+, 2006)
J/AJ/132/663 : Differential Velocities of very low mass SBs (Basri+, 2006)
J/AJ/131/2722 : New L and T dwarfs from the SDSS (Chiu+, 2006)
J/ApJ/637/1067 : Near-IR spectral classification of T dwarfs (Burgasser+, 2006)
J/AJ/130/1680 : LSPM-North proper-motion catalog nearby stars (Lepine+, 2005)
J/other/ARA+A/42.685 : Young stars near the Sun (Zuckerman+, 2004)
J/AJ/127/3553 : JHK phot. and spectroscopy for L and T dwarfs (Knapp+, 2004)
J/AJ/127/2856 : Brown dwarfs in the 2MASS Survey (Burgasser+, 2004)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/ApJ/582/1011 : Revised NLTT Catalog (Salim+, 2003)
J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [PSO]
5- 21 A17 --- PSO Pan-STARRS1 name (Jddd.dddd+dd.dddd)
23- 27 F5.2 mag zP1mag [17.3/21.5]? PS1 zP1-band magnitude (1)
29- 32 F4.2 mag e_zP1mag [0/0.3]? zP1mag uncertainty
34- 38 F5.2 mag yP1mag [16.4/20.1] PS1 yP1-band magnitude (1)
40- 43 F4.2 mag e_yP1mag [0.01/0.2] yP1mag uncertainty
45- 63 A19 --- WISE WISE name (JHHMMSS.ss+DDMMSS.s; II/311)
65- 69 F5.2 mag W1mag [11.9/16.8] WISE W1 (3.6um) band magnitude
71- 74 F4.2 mag e_W1mag [0.02/0.2] W1mag uncertainty
76- 80 F5.2 mag W2mag [11.4/15.4] WISE W2 (4.5um) band magnitude
82- 85 F4.2 mag e_W2mag [0.02/0.2] W2mag uncertainty
87 A1 --- l_W3mag Limit flag on W3mag
89- 93 F5.2 mag W3mag [9.9/14.1] WISE W3 (12um) band magnitude
95- 98 F4.2 mag e_W3mag [0.06/0.6]? W3mag uncertainty
--------------------------------------------------------------------------------
Note (1): Pan-STARRS1 photometry is quoted as of 2015 March. The photometric
selections described in this paper were done using Pan-STARRS1
photometry from 2012 January.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [PSO]
5- 13 A9 --- AName Abbreviated PSO name (Jddd.d+dd)
15 A1 --- f_AName [b] Flag on AName (2)
17 A1 --- l_Jmag Limit flag on Jmag
19- 23 F5.2 mag Jmag [14.2/17.8]? 2MASS J-band magnitude (3)
25- 28 F4.2 mag e_Jmag [0.03/0.4]? Jmag uncertainty
30 A1 --- l_Hmag Limit flag on Hmag
32- 36 F5.2 mag Hmag [13.4/16.9]? 2MASS H-band magnitude (3)
38- 41 F4.2 mag e_Hmag [0.03/0.3]? Hmag uncertainty
43 A1 --- l_Kmag Limit flag on Kmag
45- 49 F5.2 mag Kmag [12.9/17.3]? 2MASS K-band magnitude (3)
51- 54 F4.2 mag e_Kmag [0.03/0.3]? Kmag uncertainty
56- 60 F5.2 mag Jmag2 [14/18.9]? MKO J-band magnitude
62- 65 F4.2 mag e_Jmag2 [0/0.3]? Jmag2 uncertainty
67 A1 --- f_Jmag2 [d] Flag on Jmag2 (2)
69- 73 F5.2 mag Hmag2 [13.48/17.98]? MKO H-band magnitude
75- 78 F4.2 mag e_Hmag2 [0/0.3]? Hmag2 uncertainty
80 A1 --- f_Hmag2 [de] Flag on Hmag2 (2)
82- 86 F5.2 mag Kmag2 [12.94/17.33]? MKO K-band magnitude
88- 91 F4.2 mag e_Kmag2 [0/0.39]? Kmag2 uncertainty
93- 95 A3 --- f_Kmag2 [cd,e ] Flag(s) on Kmag2 (2)
97 I1 --- Ref [1/3]? Reference (4)
--------------------------------------------------------------------------------
Note (2): Flag as follows:
b = 2MASS photometry from 2MASS Point Source Reject Table
(Skrutskie et al. 2006, VII/233).
c = Calibrated using the 2MASS H magnitude because the 2MASS K magnitude is
an upper limit.
d = MKO magnitudes were synthesized using the 2MASS magnitudes for the
corresponding filters and our low-resolution spectra.
e = For MKO photometry, H- and K-band magnitudes were synthesized using
observed J-band magnitudes and our low-resolution spectra.
Note (3): All 2MASS photometry is from the 2MASS Point Source Catalog
(Cutri et al. 2003, II/246) except flagged "b" in Note (1).
Note (4): Reference as follows:
1 = this work (UKIRT/WFCAM),
2 = UKIDSS DR9 (Lawrence et al. 2013, II/319),
3 = VISTA Hemisphere Survey (Cross et al. 2012A&A...548A.119C 2012A&A...548A.119C).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [PSO]
5- 13 A9 --- AName Abbreviated PSO name (Jddd.d+dd)
15 A1 --- f_AName [a] a: Observations were originally presented
in Best et al. (Paper I, 2013ApJ...777...84B 2013ApJ...777...84B)
17- 27 A11 "Y/M/D" Date UT date of the observation
29- 31 F3.1 arcsec Slit [0.5/0.8] Slit (1)
33- 36 I4 s Tint [70/3720] Integration time
38- 55 A18 --- Std A0V standard star
--------------------------------------------------------------------------------
Note (1): All observations performed in prism mode with the 0.8x15arcsec (R∼75)
or 0.5x15arcsec (R∼120) slit.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [PSO]
5- 13 A9 --- AName Abbreviated PSO name (Jddd.d+dd)
15- 24 A10 --- SpT Visual spectral type (G1)
26- 30 F5.1 pc Dist [9.4/135] Photometric distance (1)
32- 35 F4.1 pc e_Dist [0.8/23] Dist uncertainty
37- 40 I4 mas/yr pmRA [-545/732] Proper motion along RA
(µ_αcosδ) (2)
42- 44 I3 mas/yr e_pmRA [2/121] pmRA uncertainty
46- 49 I4 mas/yr pmDE [-852/515] Proper motion along DEC
(µ_δ) (2)
51- 53 I3 mas/yr e_pmDE [4/134] pmDE uncertainty
55- 57 I3 km/s Vtan [2/110] Tangential velocity
59- 60 I2 km/s e_Vtan [0/29] Vtan uncertainty
62- 67 A6 --- Ref Discovery reference(s) (3)
69 A1 --- f_Ref [c] c: Photometric candidate
--------------------------------------------------------------------------------
Note (1): Photometric distances calculated using W2 magnitudes and the
polynomial from Dupuy & Liu (2012, J/ApJS/201/19).
Note (2): Proper motions calculated using PS1 astrometry, as well as 2MASS
astrometry when available.
Note (3): Discovery references as follows:
1 = Baron et al. (2015ApJ...802...37B 2015ApJ...802...37B)
2 = this paper
3 = Thompson et al. (2013, J/PASP/125/809)
4 = Best et al. (2013ApJ...777...84B 2013ApJ...777...84B) (Paper I)
5 = Hogan et al. (2008MNRAS.388..495H 2008MNRAS.388..495H)
6 = Lodieu et al. (2014MNRAS.445.3908L 2014MNRAS.445.3908L)
7 = Mace et al. (2013, J/ApJS/205/6)
8 = Zhang et al. (2009, J/A+A/497/619)
9 = Bardalez Gagliuffi et al. (2014ApJ...794..143B 2014ApJ...794..143B)
10 = Marocco et al. (2015, J/MNRAS/449/3651)
11 = Aberasturi et al. (2011A&A...534L...7A 2011A&A...534L...7A)
12 = Zhang et al. (2010, J/MNRAS/404/1817)
13 = Kirkpatrick et al. (2011, J/ApJS/197/19)
14 = Bihain et al. (2013A&A...557A..43B 2013A&A...557A..43B)
Objects first published by other authors (and independently
discovered by us) are detailed in Table 5.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Set "M" dwarfs or "L" dwarfs
3- 5 A3 --- --- [PSO]
7- 15 A9 --- AName Abbreviated PSO name (Jddd.d+dd)
17 A1 --- f_AName [c] Flag on AName (1)
19- 22 A4 --- H2OS H2O index-derived spectral type
24- 26 F3.1 --- e_H2OS [0.6/2.3]? Subtype negative uncertainty
28- 30 F3.1 --- E_H2OS [0.5/2.2]? Subtype positive uncertainty
32- 35 A4 --- H2ODS H2OD index-derived spectral type
37- 39 F3.1 --- e_H2ODS [0.8/1.8]? Subtype negative uncertainty
41- 43 F3.1 --- E_H2ODS [0.8/1.7]? Subtype positive uncertainty
45- 48 A4 --- H201S H2O-1 index-derived spectral type
50- 52 F3.1 --- e_H201S [1.1/1.6]? Subtype negative uncertainty
54- 56 F3.1 --- E_H201S [1.1/1.6]? Subtype positive uncertainty
58- 61 A4 --- H202S H2O-2 index-derived spectral type
63- 65 F3.1 --- e_H202S [0.6/1.9]? Subtype negative uncertainty
67- 69 F3.1 --- E_H202S [0.6/1.9]? Subtype positive uncertainty
71- 74 A4 --- <SpT> Average spectral type (2)
76- 78 F3.1 --- e_<SpT> [0.4/1.7]? Subtype negative uncertainty
80- 82 F3.1 --- E_<SpT> [0.4/1.6]? Subtype positive uncertainty
84- 93 A10 --- SpT Adopted visual spectral type (G1)
--------------------------------------------------------------------------------
Note (1): No indices yielded spectral types within the valid range of any index
for this object, so no average spectral type was derived.
Note (2): Calculated as the weighted average of the spectral types from
Monte Carlo simulations for all indices, excluding those that fell
outside the valid range for each index.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Set "L" dwarfs or "T" dwarfs
3- 5 A3 --- --- [PSO]
7- 15 A9 --- AName Abbreviated PSO name (Jddd.d+dd)
17- 21 F5.3 --- H20J [0.1/1] H2O-J index value
23 A1 --- l_H2OJS Limit flag on H2OJS
25- 28 A4 --- H2OJS Derived spectral type from H2OJ
30- 34 F5.3 --- CH4J [0.2/1.1] CH4-J index value
36 A1 --- l_CH4JS Limit flag on CH4JS
38- 41 A4 --- CH4JS Derived spectral type from CH4J
43- 47 F5.3 --- H2OH [0.2/1] H2O-H index value
49 A1 --- l_H2OHS Limit flag on H2OHS
51- 55 A5 --- H2OHS Derived spectral type from H2OHS
57- 61 F5.3 --- CH4H [0.2/1.3] CH4-H index value
63 A1 --- l_CH4HS Limit flag on CH4HS
65- 68 A4 --- CH4HS Derived spectral type from CH4H
70- 74 F5.3 --- CH4K [0.1/1.2] CH4-K index value
76- 77 A2 --- l_CH4KS [<≥ ] Limit flag on CH4KS
79- 82 A4 --- CH4KS Derived spectral type from CH4K
84- 87 A4 --- <SpT> Average spectral type (1)
89- 91 F3.1 --- e_<SpT> [0.1/4.1] Subtype uncertainty
93-100 A8 --- SpT Adopted visual spectral type (G1)
--------------------------------------------------------------------------------
Note (1): Spectral types were calculated using the polynomials defined in
Burgasser (2007ApJ...659..655B 2007ApJ...659..655B).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table14.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [PSO]
5- 21 A17 --- PSO PSO name (Jddd.dddd+dd.dddd)
23 A1 --- f_PSO [d] Flag on PSO J100.5233+41.0320 (1)
25- 32 A8 --- SpT Visual spectral type
34- 37 F4.1 pc Dist [11.2/31.5] Photometric distance (2)
39- 41 F3.1 pc e_Dist [1.3/4.4] Dist uncertainty
43- 45 I3 mas/yr pmRA [-46/526] Proper motion along RA
(µαcosδ)
47- 48 I2 mas/yr e_pmRA [2/19] pmRA uncertainty
50- 53 I4 mas/yr pmDE [-400/16] Proper motion along DEC
(µδ)
55- 56 I2 mas/yr e_pmDE [4/19] pmDE uncertainty
58- 68 A11 --- Youth Signs of youth (3)
70- 82 A13 --- YMG BANYAN II Young Moving Group (YMG) name
84- 87 F4.1 % Prob [71.4/99] Membership probability
89- 93 F5.2 [Lsun] logLbol [-4.8/-4.3] Log of bolometric luminosity
95- 98 F4.2 [Lsun] E_logLbol [0.09/0.2] Positive uncertainty on logLbol
100-103 F4.2 [Lsun] e_logLbol [0.09/0.2] Negative uncertainty on logLbol
105-108 F4.1 Mjup Mass [5.9/15] Mass (4)
110-112 F3.1 Mjup E_Mass [0.7/4] Positive uncertainty on Mass
114-116 F3.1 Mjup e_Mass [0.6/3] Negative uncertainty on Mass
--------------------------------------------------------------------------------
Note (1):
d = Previously identified by Gagne et al. (2014, J/ApJ/783/121;
2015, J/ApJ/798/73) as a candidate member of the AB Doradus Moving Group.
First discovered as WISE 0642+4101 (Mace et al. 2013, J/ApJS/205/6).
Note (2): Photometric distances calculated using KMKO magnitudes and the
polynomial from Dupuy & Liu (2012, J/ApJS/201/19).
Note (3): Signs of youth as follows:
Red = Redder-than-normal near-IR colors for the spectral type.
H band = Triangular H-band profile.
Note (4): Mass estimates derived assuming the objects are members of the given
YMGs. We used Lbol and the "hybrid" evolutionary models of
Saumon & Marley (2008ApJ...689.1327S 2008ApJ...689.1327S), following the method described
in Section 6.2.1.
--------------------------------------------------------------------------------
Global note:
Note (G1): Spectral types determined by visual comparison with spectral
standards, which we adopt as the final spectral types for our
discoveries. Uncertainties for these visual spectral types are
±0.5 subtypes, except for those listed with ":" (±1.0 subtype)
or "::" (≥±1.5 subtypes).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Best et al. Paper I. 2013ApJ...777...84B 2013ApJ...777...84B
(End) Emmanuelle Perret [CDS] 01-Mar-2016