J/ApJ/858/41 PS1 proper-motion survey for brown dwarfs. I. Taurus (Zhang+, 2018)
The Pan-STARRS1 proper-motion survey for young brown dwarfs in nearby
star-forming regions.
I. Taurus discoveries and a reddening-free classification method for ultracool
dwarfs.
Zhang Z., Liu M.C., Best W.M.J., Magnier E.A., Aller K.M., Chambers K.C.,
Draper P.W., Flewelling H., Hodapp K.W., Kaiser N., Kudritzki R.-P.,
Metcalfe N., Wainscoat R.J., Waters C.
<Astrophys. J., 858, 41 (2018)>
=2018ApJ...858...41Z 2018ApJ...858...41Z
ADC_Keywords: Stars, brown dwarf; Proper motions; Surveys; Molecular clouds;
Photometry, ugriz; Photometry, infrared; Spectral types;
Stars, ages; Extinction
Keywords: brown dwarfs;
open clusters and associations: individual (Taurus-Auriga);
stars: formation; stars: late-type; stars: low-mass
Abstract:
We are conducting a proper-motion survey for young brown dwarfs in the
Taurus-Auriga molecular cloud based on the Pan-STARRS1 3π Survey.
Our search uses multi-band photometry and astrometry to select
candidates, and is wider (370deg2) and deeper (down to ∼3MJup)
than previous searches. We present here our search methods and
spectroscopic follow-up of our high-priority candidates. Since
extinction complicates spectral classification, we have developed a
new approach using low-resolution (R∼100) near-infrared spectra to
quantify reddening-free spectral types, extinctions, and gravity
classifications for mid-M to late-L ultracool dwarfs (≤100-3MJup in
Taurus). We have discovered 25 low-gravity (VL-G) and the first 11
intermediate-gravity (INT-G) substellar (M6-L1) members of Taurus,
constituting the largest single increase of Taurus brown dwarfs to
date. We have also discovered 1 new Pleiades member and 13 new members
of the Perseus OB2 association, including a candidate very wide
separation (58kau) binary. We homogeneously reclassify the spectral
types and extinctions of all previously known Taurus brown dwarfs.
Altogether our discoveries have thus far increased the substellar
census in Taurus by ∼40% and added three more L-type members
(≲5-10MJup). Most notably, our discoveries reveal an older (>10Myr)
low-mass population in Taurus, in accord with recent studies of the
higher-mass stellar members. The mass function appears to differ
between the younger and older Taurus populations, possibly due to
incompleteness of the older stellar members or different star
formation processes.
Description:
Our candidate selection is based on previously known Taurus members
from Luhman+ (2017, J/AJ/153/46 ; their Table 1) and
Best+ (2017ApJ...837...95B 2017ApJ...837...95B). Our list of Taurus members contains 415
objects in total, spanning B9-L2 in spectral type.
We start our search by mining the PS1 Processing Version 3 database
(2016 August, the final version of PS1 reprocessing prior to public
release).
We then cross-match the extracted PS1 objects with ancillary catalogs
including AllWISE, 2MASS, and UGCS with matching radii of 5", 2", and
2", respectively.
See section 2 for further details.
During 2016 Oct-Nov, we used the NASA Infrared Telescope Facility
(IRTF)/SpeX to obtain near-infrared spectra for 83 candidates, among
which 19 objects are located in the overlapping region between Taurus
and Per OB2.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 101 123 IRTF/SpeX observations
table5.dat 150 216 PS1 & AllWISE photometry of our discoveries and
previously known objects
table6.dat 124 213 UGCS photometry of our discoveries and
previously known objects
table7.dat 128 216 2MASS photometry of our discoveries and
previously known objects
table8.dat 144 206 Classification results of our discoveries and
previously known objects
table9.dat 122 213 Proper motions, effective temperatures and
bolometric luminosities of our discoveries
previously known objects
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See also:
I/343 : Gaia-PS1-SDSS (GPS1) proper motion catalog (Tian+, 2017)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/328 : AllWISE Data Release (Cutri+ 2013)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/A+AS/125/229 : A standard stellar library (Lejeune+ 1997)
J/A+AS/130/65 : A standard stellar library. II. (Lejeune+ 1998)
J/AJ/117/354 : OB associations from Hipparcos (de Zeeuw+, 1999)
J/ApJ/541/977 : HST observations of low-mass stars in IC 348 (Najita+, 2000)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/ApJ/593/1093 : IC 348 membership (Luhman+, 2003)
J/MNRAS/342/1241 : Low-mass stars in M45 and M44 (Pinfield+, 2003)
J/AJ/127/2856 : Brown dwarfs in the 2MASS Survey (Burgasser+, 2004)
J/AJ/127/3553 : JHK phot. and spectroscopy for L and T dwarfs (Knapp+, 2004)
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/A+A/446/485 : New very low-mass members in Taurus (Guieu+, 2006)
J/ApJ/645/676 : Spatial distribution of brown dwarfs in Taurus (Luhman+, 2006)
J/A+A/453/635 : Modelling the Gal. Interstellar Extinction (Marshall+, 2006)
J/AJ/131/3016 : Low-mass objects in Upper Scorpius (Slesnick+, 2006)
J/A+A/460/695 : Search for Associations Containing Young stars (Torres+, 2006)
J/AJ/134/2340 : Praesepe & Coma Berenices cluster memberships (Kraus+, 2007)
J/AJ/134/411 : Properties of IC 348 members (Muench+, 2007)
J/ApJ/675/1375 : IRAC/MIPS photometry in Cha I (Luhman+, 2008)
J/ApJ/676/1281 : L and T dwarfs in 2MASS/SDSS (Metchev+, 2008)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/ApJ/704/531 : The coevality of young binary systems (Kraus+, 2009)
J/AJ/139/2566 : SLoWPoKES catalog (Dhital+, 2010)
J/ApJS/190/100 : NIR proper motion survey using 2MASS (Kirkpatrick+, 2010)
J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)
J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 2010)
J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011)
J/ApJS/196/4 : New young star candidates in Taurus-Auriga (Rebull+, 2011)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/MNRAS/422/1495 : UKIDSS Gal. Clusters Survey Pleiades members (Lodieu+ 2012)
J/ApJ/758/31 : IR photometry for members of Upper Sco (Luhman+, 2012)
J/AJ/144/102 : Cat. of wide companions to Hipparcos stars (Tokovinin+, 2012)
J/MNRAS/434/806 : Pre-main-sequence isochrones. II. SFR (Bell+, 2013)
J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)
J/ApJ/792/119 : Companions to nearby stars from Pan-STARRS 1 (Deacon+, 2014)
J/ApJ/784/126 : IR photometry of all known members in Taurus (Esplin+, 2014)
J/ApJ/786/97 : Photospheric properties of T Tauri stars (Herczeg+, 2014)
J/AJ/150/95 : Masses and ages of YSOs in Per OB2 (Azimlu+, 2015)
J/ApJ/814/118 : L/T transition dwarfs search with PS1 & WISE. II (Best+, 2015)
J/ApJ/799/155 : Sub-stellar companions in Taurus (Daemgen+, 2015)
J/ApJ/810/158 : M,L,T dwarfs fundamental param. and SEDs (Filippazzo+, 2015)
J/ApJS/219/33 : BANYAN. VII. Candidate YMG members from BASS (Gagne+, 2015)
J/ApJS/219/20 : Outflows and bubbles in Taurus (Li+, 2015)
J/MNRAS/448/2737 : New PMS K/M Stars in Upper Scorpius (Rizzuto+, 2015)
J/ApJ/833/96 : Hawaii infrared plx program. II. Ultracool dwarfs (Liu+, 2016)
J/ApJS/231/15 : Astrometric monitoring of ultracool dwarf bin. (Dupuy+, 2017)
J/AJ/154/134 : Planetary-mass brown dwarfs in the Taurus SFR (Esplin+, 2017)
J/ApJ/838/150 : The Taurus-Auriga ecosystem. I. (Kraus+, 2017)
J/AJ/153/46 : Spectroscopy of candidate members in Taurus (Luhman+, 2017)
J/ApJS/234/1 : Cat. of M, L, & T dwarfs from PS1 3π Survey (Best+, 2018)
J/AJ/155/34 : Analysis of NIR spectra of neighboring L dwarfs (Cruz+, 2018)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- Type Object type (1)
35- 57 A23 --- ID Object identifier
58 A1 --- f_ID Flag on ID (G1)
60- 69 A10 "Y/M/D" Date Observation date
71- 73 F3.1 arcsec Slit [0.8] Slit width
75- 76 I2 --- R [75] Resolution; λ/Δλ
78- 81 I4 s Exp [58/3108] Exposure time
83- 85 I3 --- S/N [12/326] Median J-band Signal-to-Noise per pixel
87- 94 A8 --- Std A0V standard
96-101 F6.3 --- DelAir [-0.4/0.5] Average airmass difference (2)
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Note (1): The <M4 stars found by us are probably field dwarfs that are not
associated with Taurus (Section 5.3).
Note (2): Between the A0V standard star and the science target during
exposures (i.e., standard - target).
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- Type Object type (1)
35- 57 A23 --- ID Object identifier
59 A1 --- f_ID [ad] Flag on ID (G1)
61- 65 F5.2 mag gmag [15/29] PS1 g band AB magnitude
67- 70 F4.2 mag e_gmag [0/0.6] Uncertainty in gmag
72 I1 --- q_gmag [0/1] Quality flag for gmag (1=good) (G2)
74- 78 F5.2 mag rmag [13.1/25.1] PS1 r band AB magnitude
80- 83 F4.2 mag e_rmag [0/0.6] Uncertainty in rmag
85 I1 --- q_rmag [0/1] Quality flag for rmag (1=good) (G2)
87- 91 F5.2 mag imag [12.1/22.4] PS1 i band AB magnitude
93- 96 F4.2 mag e_imag [0/0.6] Uncertainty in imag
98 I1 --- q_imag [0/1] Quality flag for imag (1=good) (G2)
100-104 F5.2 mag zmag [11.3/21] PS1 z band AB magnitude
106-109 F4.2 mag e_zmag [0/0.6] Uncertainty in zmag
111 I1 --- q_zmag [0/1] Quality flag for zmag (1=good) (G2)
113-117 F5.2 mag ymag [10.9/19.8] PS1 y band AB magnitude
119-122 F4.2 mag e_ymag [0/0.6] Uncertainty in ymag
124 I1 --- q_ymag [0/1] Quality flag for ymag (1=good) (G2)
126-130 F5.2 mag W1mag [8.1/15.9]? WISE 3.4um (W1) band magnitude
132-135 F4.2 mag e_W1mag [0.02/0.09]? Uncertainty in W1mag
137 I1 --- q_W1mag [0/1]? Quality flag for W1mag (1=good) (G2)
139-143 F5.2 mag W2mag [7.5/15.6]? WISE 4.6um (W2) band magnitude
145-148 F4.2 mag e_W2mag [0.02/0.2]? Uncertainty in W2mag
150 I1 --- q_W2mag [0/1]? Quality flag for W2mag (1=good) (G2)
--------------------------------------------------------------------------------
Note (1): The <M4 stars found by us are probably field dwarfs that are not
associated with Taurus (Section 5.3).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- Type Object type (1)
35- 57 A23 --- ID Object identifier
59 A1 --- f_ID Flag on ID (G1)
61- 79 A19 --- UGCS UGCS Identifier (JHHMMSS.ss+DDMMSS.s)
81- 86 F6.3 mag Jmag [10.7/16.9]? MKO J band magnitude
88- 92 F5.3 mag e_Jmag [0.001/0.02]? Uncertainty in Jmag
94 I1 --- q_Jmag [0/1]? Quality flag for Jmag (1=good) (G2)
96-101 F6.3 mag Hmag [10.8/16.2]? MKO H band magnitude
103-107 F5.3 mag e_Hmag [0.001/0.02]? Uncertainty in Hmag
109 I1 --- q_Hmag [0/1]? Quality flag for Hmag (1=good) (G2)
111-116 F6.3 mag Kmag [9.5/16]? MKO K band magnitude
118-122 F5.3 mag e_Kmag [0.001/0.03]? Uncertainty in Kmag
124 I1 --- q_Kmag [0/1]? Quality flag for Kmag (1=good) (G2)
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Note (1): Reddened field dwarfs studied by Allers & Liu 2013ApJ...772...79A 2013ApJ...772...79A,
i.e., 2M 0422+1530, 2M 0435-1414, 2M 0619-2903, do not have UGCS
detections so are not included in the table.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- Type Object type
35- 57 A23 --- ID Object identifier
59 A1 --- f_ID Flag on ID (G1)
61- 83 A23 --- OID 2MASS or Literature identifier (2)
85- 90 F6.3 mag Jmag2 [9.4/17.4]? 2MASS J band magnitude
92- 96 F5.3 mag e_Jmag2 [0.02/0.2]? Uncertainty in Jmag2
98 I1 --- q_Jmag2 [0/1] Quality flag for Jmag2 (1=good) (G2)
100-105 F6.3 mag Hmag2 [8.6/16.5]? 2MASS H band magnitude
107-111 F5.3 mag e_Hmag2 [0.01/0.3]? Uncertainty in Hmag2
113 I1 --- q_Hmag2 [0/1] Quality flag for Hmag2 (1=good) (G2)
115-120 F6.3 mag Ksmag2 [8.4/15.9]? 2MASS Ks band magnitude
122-126 F5.3 mag e_Ksmag2 [0.01/0.3]? Uncertainty in Ksmag2
128 I1 --- q_Ksmag2 [0/1] Quality flag for Ksmag2 (1=good) (G2)
--------------------------------------------------------------------------------
Note (2): We show 2MASS designations for our discoveries and literature names
for previously known objects.
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Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- Type Object type
35- 57 A23 --- ID Object identifier
59- 64 A6 --- n_ID Note on 2MASS J06195260-2903592 (3)
66 A1 --- f_ID Flag on ID (G1)
68- 71 A4 --- SpT1 Reddening-free spectral type as computed
in our work and adopted
73- 75 F3.1 --- e_SpT1 [0.6/1.7] Uncertainty in SpT1
77- 80 A4 --- SpT2 Allers & Liu 2013ApJ...772...79A 2013ApJ...772...79A spectral type
based on the observed spectra
82- 84 F3.1 --- e_SpT2 [0.2/1.5] Uncertainty in SpT2
86- 89 A4 --- SpT3 Allers & Liu 2013ApJ...772...79A 2013ApJ...772...79A spectral type
based on the dereddened spectra
91- 93 F3.1 --- e_SpT3 [0.4/2.1] Uncertainty in SpT3
95- 98 A4 --- SpT4 Literature spectral type for known objects
100-103 F4.1 mag Av1 [-4.3/18.4] V band extinction based on
H2O-band color-color diagrams
105-107 F3.1 mag e_Av1 [4] Uncertainty in Av1
109-113 F5.2 mag Av2 [-4/13.5]? V-band extinction based on
Optical/NIR colors
115-118 F4.2 mag e_Av2 [0.8/1.2]? Uncertainty in Av2
120-123 F4.1 mag Av3 [0/18.1]? Literature V-band extinction value
for known objects
125-127 F3.1 mag e_Av3 [0.5]? Uncertainty in Av3
129-133 F5.2 mag Av [-3.9/18.4] Adopted V band extinction
135-138 F4.2 mag e_Av [0.8/4] Uncertainty in Av
140-144 A5 --- GClass Gravity classification
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Note (3): Two classification results are shown for 2M 0619-2903 based on its
near-infrared spectrum obtained in 2008 November and 2015 December.
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- Type Object type
35- 57 A23 --- ID Object identifier
59 A1 --- f_ID Flag on ID (G1)
61- 66 F6.2 mas/yr pmRA [-33/123.5] Proper motion in RA * cos(DE)
68- 72 F5.2 mas/yr e_pmRA [0/48.4] Uncertainty in pmRA
74- 79 F6.2 mas/yr pmDE [-82/89.6] Proper motion in DE
81- 85 F5.2 mas/yr e_pmDE [0/57] Uncertainty in pmDE
87- 90 F4.1 --- chi2 [0.4/80.6]? Reduced χ2 of
proper motion model
92- 95 I4 K Teff [1939/3084]? Effective temperature
97- 99 I3 K e_Teff [139/237]? Uncertainty in Teff
101-105 F5.2 [Lsun] logL [-3.3/0]? Log bolometric luminosity
107-110 F4.2 [Lsun] e_logL [0.1/0.4]? Uncertainty in logL
112 A1 --- l_Age Limit flag on Age
113-115 I3 Myr Age ? Model derived age limit value
117-118 I2 Myr Agelo ? Model derived lower age
120-122 I3 Myr Ageup ? Model derived upper age
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Global notes:
Note (G1): Flag as follows:
d = One of eight new Taurus members that need reobservations (Section 5.1).
a = The bolometric luminosity could be unreliable since it has bad
quality J-band photometry.
Note (G2): Code as below:
1 = good quality, as defined in Section 2.3;
0 = not good quality.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 15-Mar-2019