J/ApJ/758/56 Young M dwarfs within 25pc. II. Kinematics (Shkolnik+, 2012)
Identifying the young low-mass stars within 25 pc.
II. Distances, kinematics, and group membership.
Shkolnik E.L., Anglada-Escude G., Liu M.C., Bowler B.P., Weinberger A.J.,
Boss A.P., Reid I.N., Tamura M.
<Astrophys. J., 758, 56 (2012)>
=2012ApJ...758...56S 2012ApJ...758...56S
ADC_Keywords: Stars, late-type ; Stars, distances ; Radial velocities ;
Stars, ages ; Parallaxes, trigonometric
Keywords: brown dwarfs; stars: formation; stars: kinematics and dynamics;
stars: late-type; stars: low-mass;
stars: luminosity function, mass function
Abstract:
We have conducted a kinematic study of 165 young M dwarfs with ages of
≲300Myr. Our sample is composed of stars and brown dwarfs with
spectral types ranging from K7 to L0, detected by ROSAT and with
photometric distances of ≲25pc assuming that the stars are single and
on the main sequence. In order to find stars kinematically linked to
known young moving groups (YMGs), we measured radial velocities for
the complete sample with Keck and CFHT optical spectroscopy and
trigonometric parallaxes for 75 of the M dwarfs with the CAPSCam
instrument on the du Pont 2.5m Telescope. Due to their youthful
overluminosity and unresolved binarity, the original photometric
distances for our sample underestimated the distances by 70% on
average, excluding two extremely young (≲3Myr) objects found to have
distances beyond a few hundred parsecs. We searched for kinematic
matches to 14 reported YMGs and identified 10 new members of the
AB Dor YMG and 2 of the Ursa Majoris group. Additional possible
candidates include six Castor, four Ursa Majoris, two AB Dor members,
and one member each of the Her-Lyr and β Pic groups. Our sample
also contains 27 young low-mass stars and 4 brown dwarfs with ages
≲150Myr that are not associated with any known YMG. We identified an
additional 15 stars that are kinematic matches to one of the YMGs, but
the ages from spectroscopic diagnostics and/or the positions on the
sky do not match. These warn against grouping stars together based
only on kinematics and that a confluence of evidence is required to
claim that a group of stars originated from the same star-forming
event.
Description:
Our original sample of nearby low-mass stars was drawn from the NStars
census (Reid et al. 2003, Cat. J/AJ/126/3007; 2004, Cat. J/AJ/128/463)
and the Moving-M sample (Reid et al. 2007ApJ...665..767R 2007ApJ...665..767R), which
contained ∼1100 M dwarfs. This sample was cross-matched with the ROSAT
All-Sky Survey Bright Source Catalog and Faint Source Catalog (Voges
et al. 1999, Cat. IX/10; 2000, Cat. IX/29). A more detailed
description of the sample selection process can be found in SLR09
(Paper I, Cat. J/ApJ/699/649), where we used high-resolution optical
spectra to determine spectral types (SpTs) and eliminate spectroscopic
binaries (SBs; Shkolnik et al. 2010ApJ...716.1522S 2010ApJ...716.1522S).
We acquired high-resolution echelle spectra of 155 (of the 165) young
M dwarfs in the SLR09 sample (Paper I, Cat. J/ApJ/699/649) with the
High Resolution Echelle Spectrometer (HIRES) on the Keck I 10m
telescope and with the Echelle SpectroPolarimetric Device for the
Observation of Stars (ESPaDOnS) on the Canada-France-Hawaii 3.6m
telescope, both located on the summit of Mauna Kea.
We measured parallaxes for the 75 targets (45% of our sample)
observable with the CAPSCam instrument mounted on the 2.5m du Pont
Telescope at Las Campanas Observatory.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 151 167 Observed M dwarfs
table3.dat 94 75 Summary of astrometric observations
table5.dat 161 14 Young moving groups (YMGs) searched for new members
table6.dat 130 167 Kinematics and young moving group memberships
--------------------------------------------------------------------------------
See also:
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
III/254 : 2nd Cat. of RVs with Astrometric Data (Kharchenko+, 2007)
I/298 : LSPM-North Catalog (Lepine+ 2005)
I/297 : NOMAD Catalog (Zacharias+ 2005)
I/289 : UCAC2 Catalogue (Zacharias+ 2004)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
III/198 : Palomar/MSU nearby star spectroscopic survey (Hawley+ 1997)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/238 : Yale Trigonometric Parallaxes, Fourth Edition (van Altena+ 1995)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/AJ/143/80 : Low-mass stars of beta Pic & AB Dor groups (Schlieder+, 2012)
J/A+A/531/A92 : Deep all-sky census of the Hyades (Roeser+, 2011)
J/MNRAS/415/563 : Elemental abundances in Hyades supercluster (De Silva+, 2011)
J/A+A/524/A10 : Radial Velocity standard stars (Crifo+, 2010)
J/A+A/514/A97 : Late-type stars high-resolution spectra (Lopez-Santiago+ 2010)
J/A+A/512/A45 : Radial velocities of BD+20 1790 (Hernan-Obispo+, 2010)
J/AJ/140/119 : βPic and AB Dor moving groups members (Schlieder+, 2010)
J/ApJ/699/649 : Young M dwarfs within 25pc. Paper I. (Shkolnik+, 2009)
J/A+A/499/129 : Old MS stars in young moving groups (Lopez-Santiago+, 2009)
J/MNRAS/384/1399 : Proper motions of field L and T dwarfs (Jameson+, 2008)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 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/133/2825 : Star beyond the NLTT catalog (Reid+, 2007)
J/AJ/133/2524 : Spectra of young nearby stars (White+, 2007)
J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)
J/A+A/460/695 : Search for Associations Containing Young stars (Torres+, 2006)
J/A+A/430/165 : Radial velocities for 6691 K and M giants (Famaey+, 2005)
J/other/ARA+A/42.685 : Young stars near the Sun (Zuckerman+, 2004)
J/AJ/128/463 : Preliminary 20pc census from the NLTT catalogue (Reid+, 2004)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/ApJ/582/1011 : Revised NLTT Catalog (Salim+, 2003)
J/AJ/126/3007 : Spectroscopy of faint red NLTT dwarfs (Reid+, 2003)
J/AJ/123/3356 : Palomar/MSU nearby star spec. survey. III. (Gizis+, 2002)
J/AJ/123/2806 : Nearby stars in the NLTT catalogue (Reid+, 2002)
J/A+A/384/925 : Compiled catalog of stellar data of Miras (Kharchenko+, 2002)
J/A+A/379/976 : Moving groups late-type stars EWs + fluxes (Montes+ 2001)
J/MNRAS/328/45 : Late-type stars members of young groups (Montes+, 2001)
J/A+A/337/403 : Low-mass stars evolutionary models (Baraffe+ 1998)
J/ApJ/448/683 : Hyades RASS observations (Stern+ 1995)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- Name Star name (1)
33 A1 --- f_Name [efkn] Note about binarity (2)
35- 36 I2 h RAh Hour of right ascension (J2000)
38- 39 I2 min RAm Minute of right ascension (J2000)
41- 46 F6.3 s RAs Second of right ascension (J2000)
48 A1 --- DE- Sign of declination (J2000)
49- 50 I2 deg DEd Degree of declination (J2000)
52- 53 I2 arcmin DEm Arcminute of declination (J2000)
55- 58 F4.1 arcsec DEs Arcsecond of declination (J2000)
60- 67 A8 --- SpT ? M-class sub-type(s) (3)
69 A1 --- n_SpT [hioq] Note and origin of spectral type (4)
71- 74 F4.1 mag Imag [7.8/16.8]? USNO-B1 I-band magnitude
76- 78 F3.1 mag I-Ks [1.2/4.8]? I-Ks color index
80- 86 F7.2 mas/yr pmRA [-799/714]? Proper motion along RA
88- 92 F5.2 mas/yr e_pmRA [0.9/20]? pmRA uncertainty
94-100 F7.2 mas/yr pmDE [-792/433.2]? Proper motion along DEC
102-106 F5.2 mas/yr e_pmDE [0.7/22]? pmDE uncertainty
108-112 A5 --- r_pm Reference for proper motion (5)
114-119 F6.2 km/s RV [-81/128.5]? Radial velocity
121-124 F4.2 km/s e_RV [0.1/5.3]? RV uncertainty
126 A1 --- n_RV [jmp] Origin of the velocity (6)
128-132 F5.1 pc Dist [3/325]? Photometric distance (7)
134-137 F4.1 pc e_Dist [2.2/65]? Dist uncertainty
139-143 F5.1 pc Dtrig [4.9/526]? Trigonometric distance
145-149 F5.1 pc e_Dtrig [0.1/277]? Dtrig uncertainty
151 A1 --- n_Dtrig [gl] Origin of parallax (8)
--------------------------------------------------------------------------------
Note (1): Those target names with notations in parentheses were resolved
as visual binaries (VBs) and, when possible, both components were
observed. Targets resolved as VBs using adaptive optics imaging are
designated by "(AB)" or "(ab)". The tabulated spectroscopy and
astrometry are composites of both components. Those that are RV
variable are labeled as potential single-line spectroscopic binaries
(SB1). Here we report the mean RV of our Literature values.
See Table 8 for individual velocities.
"2MASS J1442809-0424078" is a misprint for "2MASS J14442809-0424078";
corrected in tables 1 and 6 by CDS.
Note (2): Flag as follows:
e = GJ 3036: 0.426" VB (Daemgen et al. 2007ApJ...654..558D 2007ApJ...654..558D);
1RXS J0413: 0.79" VB (McCarthy et al. 2001AJ....121.3259M 2001AJ....121.3259M);
GJ 3305: 0.27" VB (Kasper et al. 2007A&A...472..321K 2007A&A...472..321K; Delorme et al.
2012A&A...539A..72D 2012A&A...539A..72D);
GJ 3786: 0.544" VB (Daemgen et al. 2007ApJ...654..558D 2007ApJ...654..558D);
GJ 3928: 1.571" VB (Daemgen et al. 2007ApJ...654..558D 2007ApJ...654..558D);
LP 331-57: 1.13" VB (Daemgen et al. 2007ApJ...654..558D 2007ApJ...654..558D);
NLTT 56566: 0.099" VB (Daemgen et al. 2007ApJ...654..558D 2007ApJ...654..558D);
1RXS J2351: 2.4" VB (Bowler et al. 2012ApJ...753..142B 2012ApJ...753..142B).
f = Common proper motion companion found in parallax program.
k = CD-35 2722 was found to have a young brown dwarf companion (Wahhaj et al.
2011ApJ...729..139W 2011ApJ...729..139W) and BD+20 1790 may host a massive close-in planet
(Hernan-Obispo et al. 2010, Cat. J/A+A/512/A45).
n = Background high proper motion star.
Note (3): The spectral types are from SLR09 (Paper I, Cat. J/ApJ/699/649),
with uncertainties of ±0.5 subclasses.
Note (4): Flag as follows:
h = Reported to be a spectroscopic binary by Shkolnik et al.
(2010ApJ...716.1522S 2010ApJ...716.1522S).
i = SpT estimated from flux ratio in the CAPSCam image (Table 7).
o = From Daemgen et al. (2007ApJ...654..558D 2007ApJ...654..558D).
q = From Reid et al. (2008, Cat. J/AJ/136/1290).
Note (5): References for the proper motions are as follows:
1 = this work;
2 = Lepine & Shara 2005, Cat. I/298;
3 = Monet et al. 2003, Cat. I/284;
4 = Perryman & ESA 1997, Cat. I/239;
5 = Zacharias et al. 2004, Cat. I/289;
6 = Salim & Gould 2003, Cat. J/ApJ/582/1011;
7 = Hog et al. 2000, Cat. I/259;
8 = van Altena et al. 1995, Cat. I/238;
9 = Jameson et al. 2008, Cat. J/MNRAS/384/1399;
10 = Kharchenko et al. 2002, Cat. J/A+A/384/925;
11 = Reid et al. 2007, Cat. J/AJ/133/2825;
12 = Zacharias et al. 2005, Cat. I/297;
13 = Zacharias et al. 2012, Cat. I/322
Note (6): Flag as follows:
j = Montes et al. (2001, Cat. J/MNRAS/328/45) report an RV of 22.1±0.1km/s.
m = RV from White et al. (2007, Cat. J/AJ/133/2524).
p = Probably due to the binary nature of this target, its measured RV is
slightly different from its companion, GJ 490 A.
Note (7): Photometric distances are calculated using the Baraffe et al. 1988
(J/A+A/337/403) models and the SLR09 (Paper I, J/ApJ/699/649) age range
(Column 11 of Table 6). We also account for known binarity.
Note (8): Flag as follows:
g = Distance adopted from Hipparcos distance of common proper motion
companions: 51 Eri for GJ 3305 and EX Cet for G271-110.
l = Distance from Hipparcos (Perryman & ESA 1997, Cat. I/239).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- Name Star name
33- 40 I8 "YYYYMMDD" Epoch1 ? First epoch (UT)
42- 49 I8 "YYYYMMDD" Epoch2 ? Last epoch (UT)
51 I1 --- Nep [3/7]? Number of epochs
53- 57 F5.1 mas Plx [1.4/105]? Relative parallax
58 A1 --- f_Plx [a] Binary PSF (1)
60- 64 F5.1 mas PlxA [1.9/105.5]? Absolute parallax
65 A1 --- f_PlxA [a] Large error (1)
67- 69 F3.1 mas e_PlxA [0.7/5]? PlxA uncertainty
70 A1 --- n_PlxA [a] e_PlxA fixed to 5mas (1)
72- 94 A23 --- Comm Comments
--------------------------------------------------------------------------------
Note (1):
a = Binary PSF produced a larger than normal error in parallax. We set a
conservative uncertainty on these of 5mas. See the text for more details.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 28 A28 --- Group Group name
30- 34 F5.1 km/s Ugr [-39.7/14.9] Group U component velocity
36- 40 F5.1 km/s Vgr [-27/1] Group V component velocity
42- 46 F5.1 km/s Wgr [-14/12] Group W component velocity
48- 53 A6 Myr Age Group age range
55- 63 A9 pc Dist Group distance range
65-152 A88 --- Ref Reference(s)
154-161 A8 --- YMG YMG abbreviated name as in table 6
(column added by CDS)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- Name Star name
33- 40 A8 --- SpT M-class sub-type(s)
42- 45 A4 --- Dc Choice of the distance measurement method:
pi=trigonometric or phot=photometric
47- 52 F6.1 km/s U [-123.9/33]? U space velocity component
54- 57 F4.1 km/s e_U [0.2/15.3]? U uncertainty
59- 63 F5.1 km/s V [-91.4/38.2]? V space velocity component
65- 68 F4.1 km/s e_V [0.1/16.9]? V uncertainty
70- 74 F5.1 km/s W [-42.2/66.5]? W space velocity component
76- 79 F4.1 km/s e_W [0.1/16.3]? W uncertainty
81- 83 F3.1 km/s dV [0.8/7.7]? Velocity modulus to YMG Δv (9)
85- 88 F4.1 --- chi2 [0/12.5]? χ2 fit
90- 91 I2 % Pm [0/98]? Probability of kinematic match
93-100 A8 --- YMG Kinematic young moving group (YMG) match (10)
102 A1 --- n_YMG [ghjk] Note on group membership (11)
104-106 I3 Myr lAge [8/625]? Lower age (or age if uAge is empty)
108-110 I3 Myr uAge [10/150]? Upper age
112-113 A2 --- l_lAges [≳ ] Limit flag on Ages
115-117 I3 Myr lAges [1/300]? Lower age (or age if uAge is empty)
from SLR09 (12)
119-122 I4 Myr uAges [40/4500]? Upper age from SLR09 (12)
124 A1 --- n_uAges [dki] Note on age estimation (11)
126-128 A3 --- Qm [A B] 3-criteria membership match quality (13)
130 A1 --- f_Qm [f] Flag on Qual (11)
--------------------------------------------------------------------------------
Note (9): To avoid making wrong matches for stars with large UVW
uncertainties, we only accept matches when the velocity modulus
Δv ((Δv)2=(U-UMG)2+(V-VMG)2+(W-WMG)2),
a measure of the difference between the UVW of a star and the UVW
of a moving group, is less than 8km/s. See section 5.1 for details.
Note (10): YMG to which the target is kinematically linked. In several cases,
stars have UVW velocities matching several YMGs and thus we further
filter based on sky position and/or age limits. See Section 5.2.
Note (11): Flag as follows:
f = It has been recently shown empirically, for at least the 12Myr old
β Pic moving group, that lower age limits of individual stars based
on the lack of lithium absorption systematically overestimates the stars'
age as compared to model isochrones (Yee & Jensen 2010ApJ...711..303Y 2010ApJ...711..303Y).
This would imply that the lower age limits may be even lower, perhaps
even as low as ∼10Myr.
g = Roser et al. (2011, Cat. J/A+A/531/A92) identified these stars as Hyades
members. LP-247-13, however, is much younger than the cluster based on
its observed low gravity. 1RXS J032230.7+285852 and II Tau have rough
upper limits of 300Myr based on the X-ray. However, SLR09 (Paper I,
Cat. J/ApJ/699/649) do show that many of the mid- and late-M Hyades
members also exhibit strong fractional X-ray luminosities. Also, using a
mean RV for the RV variable II Tau makes it a poor kinematic match to the
Hyades cluster.
h = Previously identified as YMG members. Zuckerman et al. (2004,
Cat. J/other/ARA+A/42.685) identified the AB Dor members, except for
CD-35 2722 identified by Wahhaj et al. (2011ApJ...729..139W 2011ApJ...729..139W), BD+20 1970
by Lopez-Santiago et al. (2006ApJ...643.1160L 2006ApJ...643.1160L), and NLTT15049A by Malo
et al. (2013ApJ...762...88M 2013ApJ...762...88M). β Pic members were identified by
Torres et al. (2006, Cat. J/A+A/460/695).
i = The very small parallax of this target implies that it is a brown dwarf
with an age of less than 2Myr based on evolutionary models.
j = We calculated Dtrig consistent with Hipparcos' parallax and UVWs equal
to those presented in Montes et al. (2001, Cat. J/MNRAS/328/45), who
assign this star membership of a Castor group. However, the vel. mod. and
χ2 of this star for the Castor group are 8.2km/s and 15,
respectively, excluding the star as member by our selection criteria.
k = Schlieder et al. (2012, Cat. J/AJ/143/80) reports that this star is a
member of the BPMG using the RV from Lopez-Santiago et al.
(2010, Cat. J/A+A/514/A97) which differs from ours. The spectrum does not
have any Li absorption giving a likely lower age limit of 15Myr.
Schlieder et al. (2012, Cat. J/AJ/143/80) also report variable, yet low,
Hα emission. We did not detect any emission in our spectrum.
Note (12): Age limits based on spectroscopic data such as Hα emission,
lithium absorption, and gravity indices with a 300Myr upper limit set
by X-ray emission. (See SLR09 - Paper I, Cat. J/ApJ/699/649 - for
details. In Figure 3 of SLR09, there is plenty of scatter in the X-ray
levels of proposed Hyades members, so it is possible for stars with
SpTs later than ∼M3.5, the upper age limit could be closer to the age
of the 650Myr Hyades Cluster).
Note (13): This quality flag scores three characteristics with an "A" or "B."
(a star flagged with "AAA" is an excellent YMG candidate member):
* (1) The quality of the kinematic match ("A" for having a trigonometric
distance, velocity modulus <8km/s, and match probability >50%, or "B"
for photometric distance and low match probability).
* (2) Three-dimensional positional coincidence in the sky of the star
(common R.A., decl., and distance as the proposed YMG).
* (3) Age agreement with the spectroscopically determined ages.
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History:
From electronic version of the journal
References:
Shkolnik et al. Paper I. Spectro 2009ApJ...699..649S 2009ApJ...699..649S Cat. J/ApJ/699/649
(End) Emmanuelle Perret [CDS] 03-Jul-2014