Population properties of brown dwarf analogs to exoplanets. (2016)
Keywords :
astrometry; brown dwarfs; stars low-mass
Abstract:We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 new radial velocities, and 19 new proper motions. We also add low- or moderate-resolution near-infrared spectra for 43 sources confirming their low surface gravity features. Among the full sample, we find 39 objects to be high-likelihood or new bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. Using this age-calibrated sample, we investigate trends in gravity classification, photometric color, absolute magnitude, color-magnitude, luminosity, and effective temperature.
...(more)
The sample of 152 M7-L8 ultra-cool dwarfs comprising our sample (see
table 1) were placed on follow-up programs --either imaging (parallax,
proper motion), spectroscopy (radial velocity), or both-- to determine
kinematic membership in a nearby moving group.
For Northern Hemisphere astrometry targets, we obtained I-band images
with the MDM Observatory 2.4m Hiltner telescope on Kitt Peak, Arizona.
We also observed 16 of the most southern targets with the Carnegie
Astrometric Planet Search Camera (CAPSCam) on the 100 inch du Pont
telescope and 5 with the FourStar imaging camera on the Magellan Baade
Telescope.
Table 2 gives the pertinent astrometric information; Table 3 lists our
measured parallaxes and proper motions. New proper-motion measurements
are listed in Table 5. See also section 3.1.
We used the 6.5m Baade Magellan telescope and the FIRE spectrograph to
obtain near-infrared spectra of 36 sources. Observations were made
over seven runs between 2013 July and 2014 September. All observations
(resolution R~6000) cover the full 0.8-2.5um band with a spatial
resolution of 0.18"/pixel.
We used the 3m NASA IRTF to obtain low-resolution near-infrared
spectroscopy for 10 targets. All of the observations were aligned to
the parallactic angle to obtain R~120 spectral data over the
wavelength range of 0.7-2.5um.
We used the Triple Spectrograph (TSpec) at the 5m Hale Telescope at
Palomar Observatory to obtain near-infrared spectra of two targets.
TSpec covers simultaneously the range from 1.0 to 2.45um and achieves
a resolution of ~2500.
Exposure times for each source and the number of images acquired are
listed in Table 6; see also section 3.2.
Multiple observations of 17 sources were taken in high-resolution mode
on Keck II on 2008 September 14-16, using the NIRSPEC-5 filter to
obtain H-band spectra in Order 49 (1.545-1.570um ).
Observations of 18 sources were taken during semesters 2007B and 2009B
using the H6420 filter of the Phoenix instrument (previously on Gemini
South) to select H-band spectra in Order 36 (1.551-1.558um).
Red-side spectra were taken with MIKE on the Magellan II (Clay)
telescope on 2006 July 4, 2006 November 1 and 2 for 17 targets.
Observational data for each source are listed in Table 7; see also
section 3.3.
- J/PASP/110/863 : A Stellar Spectral Flux Library
- J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002)
- J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
- J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
- J/AJ/127/3553 : JHK photometry & spectroscopy for L & T dwarfs (Knapp+, 2004)
- J/other/ARA+A/42.685 : Young stars near the Sun (Zuckerman+, 2004)
- J/A+A/441/653 : 32 DENIS nearby red dwarfs (Crifo+, 2005)
- J/other/ARA+A/43.195 : L and T dwarf stars (Kirkpatrick, 2005)
- J/ApJ/651/502 : Spitzer IRAC photometry of M, L, and T dwarfs (Patten+, 2006)
- 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/133/2258 : Activity and kinematics of ultracool dwarfs (Schmidt+, 2007)
- J/ApJ/689/1295 : Lithium test implications for BDs (Kirkpatrick+, 2008)
- J/MNRAS/383/831 : New DENIS nearby L and late-M dwarfs (Phan-Bao+, 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/137/1 : PMs and astrometry of late-type dwarfs (Faherty+, 2009)
- J/ApJ/705/1416 : Volume-limited sample of M7-M9.5 dwarfs <20pc (Reiners+, 2009)
- J/ApJ/723/684 : NIRSPEC ultracool dwarf radial velocity survey (Blake+, 2010)
- J/ApJ/710/1142 : SpeX spectroscopy of low mass binaries. I. (Burgasser+, 2010)
- J/AJ/139/1808 : Colors and kinematics of SDSS L dwarfs (Schmidt+, 2010)
- J/A+A/512/A37 : Velocities of 43 nearby L dwarfs (Seifahrt+, 2010)
- J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
- J/ApJ/752/56 : BDKP. III. Parallaxes for 70 ultracool dwarfs (Faherty+, 2012)
- J/A+A/540/A85 : Spectroscopy of very low mass objects (Patience+, 2012)
- J/ApJ/758/56 : Young M dwarfs within 25pc. II. Kinematics (Shkolnik+, 2012)
- J/ApJ/762/88 : Young stellar kinematic group candidate members (Malo+, 2013)
- J/PASP/125/809 : New nearby M, L, and T dwarfs (Thompson+, 2013)
- J/AJ/147/94 : Solar neighborhood. XXXII. L and M dwarfs (Dieterich+, 2014)
- J/ApJ/784/156 : Parallaxes for nearby mid-to-late M dwarfs (Dittmann+, 2014)
- J/ApJ/783/121 : BANYAN II. Nearby young assoc. cand. members (Gagne+, 2014)
- J/AJ/147/34 : SpeX library of L-type dwarfs (Schneider+, 2014)
- J/ApJ/814/118 : L/T transition dwarfs with PS1 & WISE. II. (Best+, 2015)
- J/ApJS/220/18 : BDKP IV. RVs of late-M & L dwarfs with MagE (Burgasser+, 2015)
- J/ApJS/219/33 : BANYAN. VII. Candidate YMG members from BASS (Gagne+, 2015)
