POPULATION PROPERTIES OF BROWN DWARF ANALOGS TO EXOPLANETS^*

At masses ≲75 M_Jup, that is, the H-burning mass limit, the interior of a source changes significantly. Below this mass limit, electron degeneracy pressure sufficiently slows contraction that the core of a given object is prevented from ever reaching the temperatures required for nuclear fusion (Hayashi & Nakano 1963; Kumar 1963). As a consequence, the evolution of substellar-mass objects produces a temperature, age, and mass degeneracy that leads to an important, and at times completely indistinguishable, overlap in the physical properties of the lowest-mass stars, brown dwarfs, and planets.

Objects with masses ≲75 M_Jup cool through their lives with spectral energy distributions evolving as their atmospheric chemistry changes with decreasing temperatures. The spectral classification for sources in the range (3000 K > T_eff > 250 K) corresponds to late-type M, L, T, and Y with each class defined by the effects of changing molecular species available in the photosphere (Kirkpatrick 2005; Burgasser et al. 2002a; Cushing et al. 2011). At the warmest temperatures, the atmosphere is too hot for the condensation of solids (Allard & Hauschildt 1995; Lodders 1999). However, as T_eff falls below 2500 K, both liquid (e.g., Fe) and solid (e.g., CaTiO₃, VO) mineral and metal condensates settle into discrete cloud layers (Tsuji et al. 1996a, 1996b; Ackerman & Marley 2001; Allard et al. 2001; Woitke & Helling 2004).

As temperatures cool further, cloud layers form at such deep levels in the photosphere that they have little or no impact on the emergent spectrum. This transition between "cloudy" to "cloudless" objects occurs rapidly over a narrow temperature range (1200–1400 K, corresponding to the transition between L-type and T-type spectra) and drives extreme photometric, spectroscopic, and luminosity changes (Burgasser et al. 2002b; Tinney et al. 2003; Artigau et al. 2009; Dupuy & Liu 2012; Faherty et al. 2012, 2014a; Radigan et al. 2012). Violent storms (like those seen on Jupiter), along with magnetic-activity-inducing aurorae, have been noted as environmental conditions likely to be present at the L-T transition (Radigan et al. 2012; Apai et al. 2013; Gillon et al. 2013; Buenzli et al. 2014, 2015; Burgasser et al. 2014; Faherty et al. 2014a; Hallinan et al. 2015; Metchev et al. 2015).

Confounding our understanding of cloud formation in low-temperature atmospheres is the mounting evidence for a correlation between cloud properties and youth. Low surface gravity brown dwarfs, which are thought to be young, have unusually red near- to mid-infrared colors and a fainter absolute magnitude through ∼2.5 μm when compared to their older spectral counterparts with field surface gravities (Faherty et al. 2012, 2013; Liu et al. 2013; Gagné et al. 2015b; Filippazzo et al. 2015). Metchev & Hillenbrand (2006) made the first connection between age and cloudiness in their study of the young companion HD 203030B, whose transition to the cloud-free T spectral class appears to be delayed by the presence of thick clouds. In a detailed study of the prototypical isolated, young brown dwarf 2M0355 + 1133, Faherty et al. (2013) found that the deviant colors and fainter absolute magnitudes were best explained by enhanced dust or thick photospheric clouds, shifting the flux to longer wavelengths. At the coldest temperatures where clouds should all but have dispersed below the photosphere in field brown dwarfs, Burgasser et al. (2010b) studied the T8 dwarf Ross 458C and found that clouds must be considered as an important opacity source for young T dwarfs.

Exoplanet studies have independently found similar trends with age and cloud properties. The young planetary-mass companions 2M1207b (<10 M_Jup) and HR8799 b (<10 M_Jup) are exceedingly red in the near-infrared and up to 2 mag fainter than field brown dwarfs of similar T_eff (Mohanty et al. 2007; Marois et al. 2008, 2010). To reproduce their anomalous observables, theorists have developed "enhanced" cloudy atmospheric models with non-equilibrium chemistry (Barman et al. 2011a, 2011b; Madhusudhan et al. 2011; Marley et al. 2012) in which lower surface gravity alters the vertical mixing which then leads to high altitude clouds with differing physical composition (e.g., thicker or thinner aggregations).

In general, M, L, T, and Y classifications identify brown dwarfs. If the source is older (>2–3 Gyr), then late-type M and early L dwarfs are stars. However, if the source is young (<1 Gyr), then even those warmer classifications will describe an object that is <75 M_Jup. To date, all directly imaged giant exoplanets have observable properties which lead to their classification squarely in this well-studied regime. Planetary-mass companions such as 2M1207b, 51 Eri b, β Pictoris b, ROXs 42B b, and the giant planets orbiting HR8799 have observables that are similar to L or T brown dwarfs (Chauvin et al. 2004; Marois et al. 2008, 2010; Lagrange et al. 2010; Currie et al. 2014; Kraus et al. 2014; Macintosh et al. 2015). Furthermore, there exists a population of "classical" brown dwarfs that overlap in effective temperature, age (many in the same moving group), and mass with directly observed planetary-mass companions (e.g., PSO318, SDSS1110, 0047+6803; Gizis et al. 2012, 2015; Liu et al. 2013; Gagné et al. 2015c). Studies of these two populations in concert may resolve questions of the formation of companions versus isolated equivalents and help to untangle atmosphere, temperature, age, and metallicity effects on the observables.

In this work, we examine this new population of suspected young, low surface gravity sources that are excellent exoplanet analogs. In Section 2, we explain the sample examined in this work and in Section 3 we describe the imaging and spectral data acquired. In Section 4, we review new near-infrared spectral types designated in this work and in Section 5 we discuss how we measured new radial velocities. In Section 6, we assess the likelihood of membership in nearby moving groups such as β Pictoris, AB Doradus, Argus, Columba, TW Hydrae, and Tucana Horologium. In Section 7, we review the diversity of the whole sample in spectral features, infrared colors, absolute magnitudes, bolometric luminosities, and effective temperatures. In Section 8, we place the young brown dwarf sample in context with directly imaged planetary-mass companions. Conclusions are presented in Section 9.

Given the age-mass degeneracy of substellar-mass objects and an age range of ∼5–130 Myr for groups such as TW Hydrae (5–15 Myr; Weinberger et al. 2013), β Pictoris (20–26 Myr; Binks & Jeffries 2014; Malo et al. 2014), and AB Doradus (110–130 Myr; Zuckerman et al. 2004; Barenfeld et al. 2013), the target temperature for our sample was T_eff < 3000 K, or, equivalently, sources with spectral types of M7 or later. This cut-off restricted us to <0.07 M_☉, or the classic brown dwarf boundary (Hayashi & Nakano 1963; Kumar 1963).

The suspicion of membership in a nearby moving group should be accompanied by observed signatures of youth as kinematics alone leave doubt about chance contamination from the field sample. As such, for this work, we focused on > M7 objects with confirmed spectral signatures of low-gravity in either the optical or the infrared. We note that while there are isolated T dwarfs which are thought to be young (e.g., SDSS1110, Gagné et al. 2015a; CFBDSIR 2149, Delorme et al. 2012), their spectral peculiarities appear to be subtle making them more difficult to identify and investigate (see also Best et al. 2015).

For isolated late-type M and L dwarfs suspected to be young, there are strong spectral differences in the strength of the alkali lines and metal oxide absorption bands as well as the shape of the near-infrared H band (∼1.65 μm ) compared to older field age counterparts (e.g., Lucas et al. 2001; Gorlova et al. 2003; Luhman et al. 2004; McGovern et al. 2004; Allers et al. 2007; Rice et al. 2010, 2011; Patience et al. 2012; Faherty et al. 2013). Physically this can be explained by a change in the balance between ionized and neutral atomic and molecular species, as a result of lower surface gravity and, consequently, lower gas densities in the photospheric layers (Kirkpatrick et al. 2006). Furthermore, a lower surface gravity is linked to a decrease in collision induced H₂ absorption (see, e.g., Tokunaga & Kobayashi 1999; Canty et al. 2013). Changes in the amount of this absorption result in the K band (∼2.2 μm ) being suppressed (or enhanced) and the shape of the H band being modeified to cause the "peaky" H band relative to water opacity seen in young sources (see Rice et al. 2011).

The collection of brown dwarfs with spectral signatures of a low surface gravity is increasing.¹³ Gagné et al. (2014c, 2015b, 2015c) presented a bayesian analysis of the brown dwarf population looking for potential new moving group members and uncovered numerous low-gravity sources. Allers & Liu (2013) presented a near-infrared spectroscopic study of a large number of known sources. Aside from those extensive studies, objects have been reported singly in paper (e.g., Kirkpatrick et al. 2006; Rice et al. 2010; Gizis et al. 2012; Faherty et al. 2013; Liu et al. 2013; Gagné et al. 2014a, 2014b, 2015a; Gauza et al. 2015) or included as a subset to a larger compilation of field objects (e.g., Cruz et al. 2007; Reid et al. 2007; Kirkpatrick et al. 2010; Thompson et al. 2013). The objects within this paper were drawn from the literature as well as our ongoing search for new low surface gravity objects.

The 152 low surface gravity¹⁴ objects examined in this work are listed in Table 1 with their coordinates, spectral types, gravity classifications (optical and infrared as applicable), as well as 2MASS and WISE photometry. There are 48 sources in this sample that are lacking an optical spectral type and 8 sources lacking an infrared spectral type. Of the 96 objects with both optical and near-infrared data, there are 67 sources (70%) that have a different optical spectral type than the infrared although the majority are within 1 subtype of each other.

For assigning a gravity designation, there are two classification systems based on spectral features. The Cruz et al. (2009) system uses optical spectra and assigns a low surface gravity (γ), intermediate gravity (β), or field gravity ("–" in Table 1 and throughout) based on the strength of metal oxide absorption bands and alkali lines. In certain cases a classification of δ is also used for objects that look more extreme than γ (see Gagné et al. 2015b). In this work we label objects as δ in tables but plot them and discuss them along with γ sources. On the Cruz et al. (2009) scheme, γ and β objects are thought to be younger than the Pleiades (age ≲ 120 Myr, Stauffer et al. 1998). The Allers & Liu (2013) system uses near-infrared spectra and evaluates spectral indices to assign a very low-gravity (vl-g), intermediate gravity (int-g), or field gravity (fld-g) to a given source. As discussed in Allers & Liu (2013), the optical and near-infrared gravity systems are broadly consistent. However, to anchor either requires an age-calibrated sample to ground the gravity designations as age-indicators.

Figure 1 shows a histogram distribution of the spectral subtypes in the optical and the infrared highlighting the gravity classification. There are 51 objects classified optically as γ and 80 with the equivalent infrared classification. There are 27 objects classified optically as β and 57 with the equivalent infrared classification. Of the objects which have both optical and infrared gravity designations, 16 sources (17%) have different gravity classifications from the two methods and 23 objects (24%) have a low-gravity infrared classification but are not noted as peculiar in the optical. For simplification of the text (and in large part because the two systems are generally consistent), we have adopted the convention that any object classified as vl-g or int-g in the infrared is referred to as γ or β, respectively, in the text, tables, and figures.

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The sample of 152 M7-L8 ultra-cool dwarfs comprising our sample 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. Below, we describe the data collected for the suspected young brown dwarf sample.

3.1. Parallax and Proper-motion Imaging

3.2. Low- and Medium-resolution Spectroscopy

3.2.1. Folded-port InfraRed Echellette (FIRE)

We used the 6.5 m Baade Magellan telescope and the FIRE (Simcoe et al. 2013) spectrograph to obtain near-infrared spectra of 36 sources. Observations were made over seven runs between 2013 July and 2014 September. For all of the observations, we used the echellette mode and the 06 slit (resolution λ/Δλ ∼ 6000) covering the full 0.8–2.5 μm band with a spatial resolution of 018/pixel. Exposure times for each source and the number of images acquired are listed in Table 6. Immediately after each science image, we obtained an A star for telluric correction and obtained a ThAr lamp spectra. At the start of the night, we obtained dome flats and Xe flash lamps to construct a pixel-to-pixel response calibration. Data were reduced using the FIREHOSE package, which is based on the MASE and SpeX reduction tools (Vacca et al. 2003; Cushing et al. 2004; Bochanski et al. 2009).

Table 6.  Near-infrared Spectral Data

2MASS	Date-Observed	Instrument	Mode	Slit	Int time	Images
(1)	(2)	(3)	(4)	(5)	(6)	(7)
00040288–6410358	11 Sep 2014	FIRE	Echelle	0.6	900	2
00274197+0503417	08 Aug 2014	FIRE	Echelle	0.6	900	2
00452143+1634446	08 Aug 2014	FIRE	Echelle	0.6	900	2
00550564+0134365	04 Sep 2003	SpeX	Prism	0.8	180	2
01174748–3403258	12 Sep 2014	FIRE	Echelle	0.6	900	2
01174748–3403258(2)	11 Sep 2014	FIRE	Echelle	0.6	600	2
01244599–5745379	11 Sep 2014	FIRE	Echelle	0.6	900	2
02103857–3015313	11 Sep 2014	FIRE	Echelle	0.6	750	2
02103857–3015313(2)	29 Dec 2009	TripleSpec	–	11 × 43''	300	6
02251947–5837295	28 Jul 2013	FIRE	Echelle	0.6	600	2
02340093–6442068	28 Jul 2013	FIRE	Echelle	0.6	750	2
03231002–4631237	13 Nov 2007	SpeX	Prism	0.5	180	5
03264225–2102057	13 Nov 2007	SpeX	Prism	0.5	180	6
04210718–6306022	11 Sep 2014	FIRE	Echelle	0.6	900	2
04351455–1414468	13 Nov 2007	SpeX	SXD	0.5	200	4
05012406–0010452	12 Oct 2007	SpeX	Prism	0.5	90	6
05120636–2949540	15 Nov 2013	FIRE	Echelle	0.6	500	2
05120636–2949540(2)	08 Dec 2011	SpeX	Prism	0.5	180	8
05361998–1920396	13 Dec 2013	FIRE	Echelle	0.6	650	2
07123786–6155528	15 Nov 2013	FIRE	Echelle	0.6	650	2
09532126–1014205	02 Mar 2009	TripleSpec	–	11 × 43''	300	6
09593276+4523309	30 Dec 2009	SpeX	Prism	0.5	180	3
11020983–3430355	12 May 2014	FIRE	Echelle	0.6	600	2
11544223–3400390	12 May 2014	FIRE	Echelle	0.6	750	2
12563961–2718455	12 May 2014	FIRE	Echelle	0.6	900	2
14112131–2119503	12 May 2014	FIRE	Echelle	0.6	500	2
14482563+1031590	13 May 2014	FIRE	Echelle	0.6	900	2
15382417–1953116	28 Jul 2013	FIRE	Echelle	0.6	900	2
15382417–1953116(2)	04 Sep 2003	SpeX	Prism	0.8	180	6
15515237+0941148	15 Aug 2013	FIRE	Echelle	0.6	900	2
15575011–2952431	28 Jul 2013	FIRE	Echelle	0.6	900	2
17111353+2326333	12 May 2014	FIRE	Echelle	0.6	800	2
17260007+1538190	12 May 2014	FIRE	Echelle	0.6	800	2
17410280–4642218	11 Sep 2014	FIRE	Echelle	0.6	1500	2
18212815+1414010	12 May 2014	FIRE	Echelle	0.6	650	2
19355595–2846343	08 Aug 2014	FIRE	Echelle	0.6	600	2
19564700–7542270	28 Jul 2013	FIRE	Echelle	0.6	900	4
20004841–7523070	28 Jul 2013	FIRE	Echelle	0.6	300	3
20025073–0521524	28 Jul 2013	FIRE	Echelle	0.6	600	2
20135152–2806020	12 May 2014	FIRE	Echelle	0.6	600	2
20135152–2806020(2)	08 Aug 2014	FIRE	Echelle	0.6	600	2
PSO318	13 Dec 2013	FIRE	Echelle	0.6	900	4
21265040–8140293	15 Aug 2013	FIRE	Echelle	0.6	900	2
21265040–8140293(2)	12 May 2014	FIRE	Echelle	0.6	800	2
21543454–1055308	08 Aug 2014	FIRE	Echelle	0.6	1200	2
22064498–4217208	12 May 2014	FIRE	Echelle	0.6	700	2
22064498–4217208(2)	08 Aug 2014	FIRE	Echelle	0.6	750	2
22064498–4217208(3)	21 Aug 2006	SpeX	Prism	0.5	180	5
22443167+2043433	11 Sep 2014	FIRE	Echelle	0.6	900	2
22495345+0044046	08 Aug 2014	FIRE	Echelle	0.6	1200	2
23153135+0617146	08 Aug 2014	FIRE	Echelle	0.6	750	2
23153135+0617146(2)	14 Nov 2007	SpeX	Prism	0.5	180	6

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3.2.2. Infrared Telescope Facility (IRTF)

We used the 3 m NASA IRTF to obtain low-resolution near-infrared spectroscopy for 10 targets. We used either the 05 slit or the 08 slit depending on conditions. All of the observations were aligned to the parallactic angle to obtain R ≡ λ/Δλ ≈120 spectral data over the wavelength range of 0.7–2.5 μm. Exposure times for each source and the number of images acquired are listed in Table 6. Immediately after each science observation, we observed an A0 star at a similar airmass for telluric corrections and flux calibration, as well as an exposure of an internal flat-field and Ar arc lamp. All of the data were reduced using the SpeXtool package version 3.4 using standard settings (Vacca et al. 2003; Cushing et al. 2004).

3.2.3. TSpec

We used the Triple Spectrograph (TSpec) at the 5 m Hale Telescope at Palomar Observatory to obtain near-infrared spectra of two targets. TSpec uses a 1024 × 2048 HAWAII-2 array to cover simultaneously the range from 1.0 to 2.45 μm (Herter et al. 2008). With a 1.1 × 43'' slit, it achieves a resolution of ∼2500. Observations were acquired in an ABBA nod sequence with an exposure time per nod position of 300 s (see Table 6) so as to mitigate problems with changing OH background levels. Observations of A0 stars were taken near in time and in airmass to the target objects and were used for telluric correction and flux calibration. Dome flats were taken to calibrate the pixel-to-pixel response. Data were reduced using a modified version of Spextool (see Kirkpatrick et al. 2011).

3.3. High-resolution Spectroscopy

We obtained spectra with FIRE, SpeX, and TSpec for 43 targets to investigate the near-infrared signatures of youth. Each object had either demonstrated optical low surface gravity features but were missing (or had poor) near-infrared data, or had low signal-to noise near-infrared spectra. Determining the spectral type and gravity classification for peculiar sources has its difficulties; primarily, because one wants to ground the peculiar object type by comparing to an equivalent field source. However, as will be seen in Section 7, the low-gravity sequence does not easily follow from the field sequence. In the infrared, Allers & Liu (2013) have presented a method for determining gravity classification using indices. Alternatively, the population of low-gravity sources (especially earlier L types) has grown in number such that templates of peculiar sources can be made for comparison (e.g., Gagné et al. 2015b, Cruz et al. submitted). For this work, we have defaulted to a visual match to templates or known sources—grounded by their optical data—as our primary spectral typing method. However, we also check each source against indices to ensure consistency.

In the case of each new spectrum, we visually compared to the library of spectra in the SpeX prism library¹⁷ as well as the low-gravity templates discussed in Gagné et al. (2015b). For the FIRE and TSpec echelle spectra, we first binned them to prism resolution (∼120). This visual check to known objects gave the match we found most reliable for this work in both type and gravity classification and it is listed in the "SpT adopted" column in Table 9. Figures 3–4 show two example spectra (prism and binned down FIRE data) compared visually to both field and very low-gravity sources, as representations of our spectral typing method.

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As a secondary check, we report the indices analysis of each object. A near-infrared spectral subtype is a required input for evaluating the gravity classification with the Allers & Liu (2013) system so we first applied the subtype indices (as described in Allers & Liu 2013) and list the results in the "SpT Allers13" column in Table 9. Once we had determined the closest near-infrared type, we evaluated the medium resolution (for FIRE and TSpec data) and/or the low-resolution gravity indices (for Prism data). We list the results of each in Table 9. In general we found that matching visually to low-gravity templates or known objects versus using indices were consistent within 1 subtype.

Radial velocities from NIRSPEC, Phoenix, and MIKE were calculated using a custom python routine which uses cross-correlation with standard brown dwarfs to achieve 1 km s⁻¹ radial velocity precision. Useable spectra have a resolving power of R = 20,000 or higher, and generally a signal to noise of at least 20. All of the data were corrected to heliocentric radial velocity by shifting the wavelength grid. Brown dwarf standards (sourced primarily from Blake et al. 2010) were observed and corrected with the same settings as the targets, and paired with objects of matching spectral type. Given that our radial velocity sample is bimodal with peaks at L0 and L4, our spectra are fit against relatively few standards.

The python code calculates radial velocities on the fly, and operates on optical and infrared data without modification. The radial velocity inputs were the wavelength, flux, and uncertainty data as three one-dimensional arrays, for both the target and the standard. The target and standard spectra were first cropped to only the portion where they overlap, and then interpolated onto a log-normal wavelength grid.

From there, 5000 trials were conducted with different randomized Gaussian noise added to the wavelength grids of the target and standard, according to the per-element uncertainties. This was done to account for the uncertainties on the fluxes and to provide a method of quantifying the uncertainty on the output radial velocity. For each of the 5000 trials, the two spectra were cross-correlated to produce a wavelength shift between them. A small 400-element region around the peak of the cross-correlation function was fit with a Gaussian and a linear term, to locate the exact peak of the cross-correlation on a sub-element basis. The widths (and therefore per-measurement errors) of the cross-correlation peak were discarded and assumed to be accounted for in the actual spread of the resulting set of peaks.

The results of the 5000 trials formed (in well-determined cases) a Gaussian histogram centered on the radial velocity shift between the two systems. The width of that Gaussian was taken to represent the uncertainty in the measured radial velocity. This pixel shift was converted into km s⁻¹ radial velocity, and corrected for the known velocity of the standard. Semi-independent verification of the radial velocities was accomplished by measuring the velocity relative to two different standards or, where available, using multiple orders from the same spectrum.

The process was sensitive to virtually all unwanted processes that produce features in the brown dwarf spectra. Chief among these were cosmic rays and detector hot pixels, which were pixel-scale events removed from the spectra prior to interpolation onto the grid and provide very little signal in the RV correlation. The most important effect was telluric lines, which appeared like normal spectral features but did not track the radial velocity of the star. These were dealt with by identifying orders whose contamination was severe enough to produce discordant radial velocities and avoiding them in the analysis.

Table 7 lists the final radial velocity values for each source. Table 8 shows a comparison of sources for which there was a literature value.

5.1. Instrument-specific Differences

Among the 152 brown dwarfs investigated for kinematic membership in this work, we report 37 new radial velocities, 8 new parallaxes, and 33 new proper motions (13 of which are reported as new from 2MASS to WISE proper-motion measurements). In total, 27 targets have full kinematics (a parallax, proper motion, and radial velocity), and the remaining 123 have only partial kinematics—16 have a parallax and proper motion but no radial velocity, 26 have radial velocity and proper motion but no parallax, and 81 have proper motions but no parallax or radial velocity measurement. All of the astrometric information for this sample is listed in Table 10.

Table 10.  Kinematic Data on Low Surface Gravity Dwarfs

2MASS Designation	SpT	SpT	${\mu }_{{\rm{R}}.{\rm{A}}.\mathrm{cosdecl}.}$	μdecl.	πa	RV	(References)
	(OpT)	(IR)	('' yr−1)	('' yr−1)	(mas)	(km s−1)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
00011217+1535355	– –	L4β	0.1352 ± 0.0107	−0.1696 ± 0.0137	–	–	10
00040288–6410358	L1γ	L1γa	0.064 ± 0.012	−0.047 ± 0.012	(17 ± 1)	(6.07 ± 2.89)	1
00182834–6703130	– –	L0γ	0.066 ± 0.004	−0.0523 ± 0.0126	–	–	1,10
00191296–6226005	– –	L1γ	0.0541 ± 0.0047	−0.0345 ± 0.0121	(21 ± 6)	(6.7 ± 2.5)	1,10
00192626+4614078	M8–	M8β	0.14000 ± 0.06	−0.1 ± 0.05	(31 ± 3)	−19.5 ± 2	2,4
00274197+0503417	M9.5β	L0β	0.0105 ± 0.0004	−0.0008 ± 0.0003	13.8 ± 1.6	–	3
00303013–1450333	L7–	L4-L6β	0.2497 ± 0.0141	−0.0053 ± 0.015	37.42 ± 4.50	–	10, 11
00325584–4405058	L0γ	L0β	0.12830 ± 0.0034	−0.0934 ± 0.003	21.6 ± 7.2	12.95 ± 1.92	1, 5
003323.86–1521309	L4β	L1	0.30950 ± 0.0104	0.0289 ± 0.0183	24.8 ± 2.5	−6.37 ± 0.40	1, 6
00344300–4102266	– –	L1β	0.0939 ± 0.0079	−0.0412 ± 0.0108	–	–	10
00374306–5846229	L0γ	– –	0.05700 ± 0.01	0.017 ± 0.005	–	6.62 ± 0.07	1
00381489–6403529	– –	M9.5β	0.0871 ± 0.0038	−0.0353 ± 0.0105	(23 ± 5)	(7.27 ± 2.81)	1, 10
00425923+1142104	– –	M9β	0.0929 ± 0.017	−0.0758 ± 0.0152	–	–	10
00452143+1634446	L2β	L2γ	0.35500 ± 0.01	−0.04 ± 0.01	62.5 ± 3.7	3.16 ± 0.83	1
00464841+0715177	M9β	L0δ	0.09800 ± 0.022	−0.051 ± 0.01	–	−2.75 ± 0.27	1, 2
00470038+6803543	L7(γ?)	L6-L8γ	0.38700 ± 0.004	−0.197 ± 0.004	82 ± 3	−20 ± 1.4	7
00550564+0134365	L2γ	L2γ	0.04400 ± 0.024	−0.082 ± 0.024	–	−1.21 ± 0.38	1, 2
00584253–0651239	L0–	L1β	0.1367 ± 0.002	−0.1226 ± 0.0018	33.8 ± 4.0	–	5
01033203+1935361	L6β	L6β	0.29300 ± 0.0046	0.0277 ± 0.0047	46.9 ± 7.6	–	8
01174748–3403258	L1β	L1βa	0.084 ± 0.015	−0.045 ± 0.008	(20 ± 3)	(3.96 ± 2.09)	1
01205114–5200349	– –	L1γ	0.0921 ± 0.0058	−0.0404 ± 0.0102	(24 ± 4)	(7.22 ± 2.5)	1, 10
01231125–6921379	M7.5γ	– –	0.08278 ± 0.00174	−0.02646 ± 0.00139	21.6 ± 3.3	10.9 ± 3	4, 9
01244599–5745379	L0γ	L0γ	−0.00300 ± 0.01	0.018 ± 0.019	–	–	2
01262109+1428057	L4γ	L2γ	0.07000 ± 0.012	−0.008 ± 0.012	–	–	1
01294256–0823580	M5–	M7β	0.1007 ± 0.0084	−0.0564 ± 0.009	–	–	10
01415823–4633574	L0γ	L0γ	0.105 ± 0.01	−0.049 ± 0.01	(25 ± 3)	6.409 ± 1.56	1
01531463–6744181	L2–	L3β	0.071 ± 0.0037	−0.0166 ± 0.0127	(21 ± 7)	(10.41 ± 2.71)	1, 10
02103857–3015313	L0γ	L0γa	0.145 ± 0.036	−0.04 ± 0.007	(32 ± 8)	7.82 ± 0.274	1
02212859–6831400	M8β	– –	0.05390 ± 0.0044	0.0137 ± 0.0045	25.4 ± 3.6	–	8
02215494–5412054	M9β	– –	0.136 ± 0.01	−0.01 ± 0.017	(31 ± 5)	10.18 ± 0.097	1, 2
02235464–5815067	L0γ	– –	0.09860 ± 0.0008	−0.0182 ± 0.0009	27.4 ± 2.6	10.36 ± 0.23	1
02251947–5837295	M9β	M9γ	0.08500 ± 0.01	−0.03 ± 0.018	–	–	2
02265658–5327032	– –	L0δ	0.0936 ± 0.0053	−0.0028 ± 0.0107	–	–	1, 10
02292794–0053282	– –	L0γ	−0.00900 ± 0.098	−0.054 ± 0.202	–	–	1
02340093–6442068	L0γ	L0βγ	0.088 ± 0.012	−0.015 ± 0.012	(21 ± 5)	11.762 ± 0.721	1
02410564–5511466	– –	L1γ	0.0965 ± 0.0052	−0.0123 ± 0.0106	(24 ± 4)	(11.73 ± 2.44)	1, 10
02411151–0326587	L0γ	L1γ	0.07370 ± 0.001	−0.0242 ± 0.0019	21.4 ± 2.6	6.34 ± 7.98	1
02501167–0151295	– –	M7β	0.0627 ± 0.0087	−0.0306 ± 0.009	30.2 ± 4.5	–	25, 10
02530084+1652532	– –	M7β	1.5124 ± 0.0406	0.4305 ± 0.0447	260.63 ± 2.69	–	24
02535980+3206373	M7β	M6β	0.08700 ± 0.01	−0.096 ± 0.01	17.7 ± 2.5	–	1
02583123–1520536	– –	L3β	0.0625 ± 0.0098	−0.0581 ± 0.0097	–	–	1, 10
03032042–7312300	L2γ	– –	0.04300 ± 0.012	0.003 ± 0.012	–	–	1
03164512–2848521	L0–	L1β	0.0952 ± 0.0082	−0.081 ± 0.0094	–	–	10
03231002–4631237	L0γ	L0γa	0.066 ± 0.008	0.001 ± 0.016	(17 ± 3)	13.001 ± 0.045	1
03264225–2102057	L5β	L5βγa	0.108 ± 0.014	−0.146 ± 0.015	(41 ± 1)	(22.91 ± 2.07)	1, 2
03350208+2342356	M8.5–	M7.5β	0.05400 ± 0.01	−0.056 ± 0.01	23.6 ± 1.3	15.5 ± 1.7	12
03393521–3525440	M9β	L0β	0.30580 ± 0.0004	0.270548 ± 0.0004	155.89 ± 1.03	6.92 ± 1.05	1, 13
03420931–2904317	– –	L0β	0.0671 ± 0.01	−0.0207 ± 0.0122	–	–	1, 10
03421621–6817321	L4γ	– –	0.0653 ± 0.0028	0.0185 ± 0.0091	(21 ± 9)	(13.87 ± 2.62)	1
03550477–1032415	M8.5–	M8.5β	0.0464 ± 0.0072	−0.0265 ± 0.0065	–	–	10
03552337+1133437	L5γ	L3-L6γ	0.22500 ± 0.0132	−0.63 ± 0.015	110.8 ± 4.3	11.92 ± 0.22	6, 14
03572695–4417305b	L0β	L0β	0.06400 ± 0.013	−0.02 ± 0.019	–	10.73 ± 4.60	1, 2
04062677–3812102	L0γ	L1γ	0.00900 ± 0.012	0.029 ± 0.012	–	–	1
04185879–4507413	– –	L3γ	0.0533 ± 0.0084	−0.0082 ± 0.0126	–	–	10
04210718–6306022	L5β	L5γ	0.14600 ± 0.008	0.191 ± 0.018	–	14.70 ± 0.33	1, 2
04351455–1414468	M8γ	M7γ	0.00900 ± 0.014	0.016 ± 0.014	–	16.16 ± 1.76	1, 2
04362788–4114465	M8β	M9γ	0.073 ± 0.012	0.013 ± 0.016	(23 ± 6)	14.972 ± 1.446	1, 2
04400972–5126544	– –	L0γ	0.0458 ± 0.0062	0.0078 ± 0.0105	–	–	10
04433761+0002051b	M9γ	M9γ	0.02800 ± 0.014	−0.099 ± 0.014	–	16.97 ± 0.76	1, 2
04493288+1607226	– –	M9γ	0.0196 ± 0.0094	−0.038 ± 0.0092	–	–	10
05012406–0010452	L4γ	L3γ	0.19030 ± 0.0095	−0.1428 ± 0.0125	51 ± 3.7	21.77 ± 0.66	1, 6
05104958–1843548	– –	L2β	0.0882 ± 0.0095	−0.0399 ± 0.0106	–	–	10
05120636–2949540	L5γ	L5β	−0.01000 ± 0.013	0.08 ± 0.015	–	–	1
05181131–3101529	M6.5–	M7β	0.0416 ± 0.0068	0.0008 ± 0.0081	–	–	10
05184616–2756457	L1γ	L1γ	0.02860 ± 0.0042	−0.016 ± 0.004	21.4 ± 6.9	24.35 ± 0.19	1, 8
05264316–1824315	– –	M7β	0.0247 ± 0.0093	−0.0227 ± 0.0095	–	–	10
05341594–0631397	M8γ	M8γ	0.00200 ± 0.012	−0.007 ± 0.012	–	–	1
05361998–1920396	L2γ	L2γ	0.02460 ± 0.0053	−0.0306 ± 0.005	25.6 ± 9.4	22.065 ± 0.695	1, 8
05402325–0906326	– –	M9β	0.0376 ± 0.0098	−0.0292 ± 0.0097	–	–	10
05575096–1359503	M7–	M7γ	0.00000 ± 0.005	0 ± 0.005	1.9 ± 1	30.3 ± 2.8	12
06023045+3910592	L1–	L1β	0.15700 ± 0.01	−0.504 ± 0.01	88.5 ± 1.6	–	1
06085283–2753583	M8.5γ	L0γ	0.00890 ± 0.0035	0.0107 ± 0.0035	32 ± 3.6	26.35 ± 0.07	1, 8
06272161–5308428	– –	L0βγ	0.0104 ± 0.0066	0.0651 ± 0.0123	–	–	10
06322402–5010349	L3β	L4γ	−0.10020 ± 0.0052	−0.0046 ± 0.0088–	–	–	1, 10
06524851–5741376	M8β	– –	0.00100 ± 0.0034	0.0292 ± 0.0033	31.3 ± 3.2	–	8
07123786–6155528	L1β	L1γ	−0.03570 ± 0.0049	0.0791 ± 0.0048	22.9 ± 9.1	–	8
07140394+3702459	M8–	M7.5β	−0.0984 ± 0.0069	−0.171 ± 0.0089	80.10 ± 4.8	–	26
08095903+4434216	– –	L6p	−0.1833 ± 0.0081	−0.2019 ± 0.013	–	–	10
08561384–1342242	– –	M8γ	−0.0576 ± 0.0078	−0.0194 ± 0.0081	–	–	10
08575849+5708514	L8–	L8–	−0.4181 ± 0.0044	−0.3706 ± 0.0113	–	–	10
09451445–7753150	– –	M9β	−0.0345 ± 0.0016	0.0436 ± 0.0119	–	–	10
09532126–1014205	M9γ	M9β	−0.07000 ± 0.007	−0.06 ± 0.009	–	–	1
09593276+4523309	– –	L3γ	−0.08700 ± 0.009	−0.126 ± 0.012	–	2.7 ± 0.7	1
G196-3B	L3β	L3γ	−0.13230 ± 0.0107	−0.2021 ± 0.0137	41 ± 4.1	–	6
10212570–2830427	– –	L4βγ	−0.0526 ± 0.0131	−0.0375 ± 0.0163	–	–	10
10220489+0200477	M9β	M9β	−0.15620 ± 0.0066	−0.429 ± 0.0068	26.4 ± 11.5	−7.9 ± 4.8	8
10224821+5825453	L1β	L1β	−0.80700 ± 0.01	−0.73 ± 0.01	54.3 ± 2.5	19.29 ± 0.11	1
TWA28	M8.5γ	M9γ	−0.06720 ± 0.0006	−0.014 ± 0.0006	18.1 ± 0.5	(13.3 ± 1.8)	18
11064461–3715115	– –	M9γ	−0.0408 ± 0.0076	−0.0066 ± 0.0102	–	–	10
11083081+6830169	L1γ	L1γ	−0.2389 ± 0.0026	−0.1922 ± 0.0092	–	–	10
11193254–1137466	– –	L7γ	-.1451 ± 0.0149	−0.0724 ± 0.016	(35 ± 5)	8.5 ± 3.3	27
11271382–3735076	– –	L0δ	−0.0613 ± 0.0138	0.0132 ± 0.0208	–	–	10
TWA26	M9γ	M9γ	−0.08120 ± 0.0039	−0.0277 ± 0.0021	23.82 ± 2.58	11.6 ± 2	15,16
114724.10–204021.3	– –	L7γ	−0.1221 ± 0.012	−0.0745 ± 0.0113	(32 ± 4)	(9.61 ± )	28
11480096–2836488	– –	L1β	−0.0743 ± 0.0135	−0.0194 ± 0.0161	–	–	10
11544223–3400390	L0β	L1β	−0.16100 ± 0.008	0.012 ± 0.007	–	–	1
TWA27A	M8γ	M8γ	−0.06300 ± 0.002	−0.023 ± 0.003	19.1 ± 0.4	11.2 ± 2	16,19
12074836–3900043	L0γ	L1γ	−0.0572 ± 0.0079	−0.0248 ± 0.0105	(15 ± 3)	(9.48 ± 1.91)	17
12271545–0636458	M9–	M8.5β	−0.1141 ± 0.0111	−0.0646 ± 0.0109	–	–	10
TWA29	M9.5γ	L0γ	−0.04030 ± 0.0117	−0.0203 ± 0.017	12.66 ± 2.07	(7.74 ± 2.04)	15
12474428–3816464	– –	M9γ	−0.03320 ± 0.0071	−0.0166 ± 0.0095	–	–	17
12535039–4211215	– –	M9.5γ	−0.0388 ± 0.009	−0.0121 ± 0.0132	–	–	10
12563961–2718455	– –	L4β	−0.0674 ± 0.0102	−0.0565 ± 0.0127	–	–	10
14112131–2119503	M9β	M8β	−0.07800 ± 0.009	−0.073 ± 0.011	–	−0.9 ± 2.5	1
14252798–3650229	L3–	L4γ	−0.28489 ± 0.0014	−0.46308 ± 0.001	86.45 ± 0.83	5.37 ± 0.25	13,14
15104786–2818174	M9–	M9β	−0.1092 ± 0.0081	−0.0399 ± 0.0098	–	–	10
15291017+6312539	– –	M8β	−0.1132 ± 0.0033	0.0447 ± 0.0091	–	–	10
15382417–1953116	L4γ	L4γ	0.02600 ± 0.007	−0.045 ± 0.007	–	–	1
15470557–1626303A	– –	M9β	−0.0539 ± 0.0087	−0.1253 ± 0.009	–	–	10
15474719–2423493	M9γ	L0β	−0.13500 ± 0.009	−0.127 ± 0.008	–	−6.52 ± 0.35	1
15515237+0941148	L4γ	>L5γ	−0.07000 ± 0.022	−0.05 ± 0.022	–	–	2
15525906+2948485	L0β	L0β	−0.16200 ± 0.01	−0.06 ± 0.01	48.8 ± 2.7	−18.43 ± 0.11	1, 14
15575011–2952431	M9δ	L1γ	−0.01000 ± 0.012	−0.028 ± 0.012	–	–	1
16154255+4953211	L4γ	L3-L6γ	−0.08000 ± 0.012	0.018 ± 0.012	–	−25.59 ± 3.18	1
17111353+2326333	L0γ	L1β	−0.06300 ± 0.015	−0.035 ± 0.012	–	−20.69 ± 0.75	1
17260007+1538190	L3.5γ	L3γ	−0.04310 ± 0.0071	−0.0557 ± 0.0052	28.6 ± 2.9	−20.54 ± 0.84	1, 6
17410280–4642218	– –	L6-L8γ	−0.02040 ± 0.0092	−0.343 ± 0.0137	–	−5.7 ± 5.1	20
18212815+1414010	L4.5–	L4pec	0.23027 ± 0.00016	−0.24149 ± 0.00012	106.65 ± 0.23	9.08 ± 0.17	1, 22
19350976–6200473	– –	L1γ	−0.0043 ± 0.0063	−0.0533 ± 0.0162	–	–	10
19355595–2846343	M9γ	M9γ	0.03400 ± 0.012	−0.058 ± 0.012	–	–	1
19564700–7542270	L0γ	L2γ	0.00900 ± 0.012	−0.059 ± 0.012	–	–	1
20004841–7523070	M9γ	M9γa	0.069 ± 0.012	−0.11 ± 0.004	(31 ± 1)	4.397 ± 2.842	1
20025073–0521524	L5β	L5-L7γ	−0.09800 ± 0.005	−0.11 ± 0.008	–	–	1
20113196–5048112	– –	L3γ	0.0213 ± 0.0081	−0.0713 ± 0.0145	–	–	10
20135152–2806020	M9γ	L0γ	0.04300 ± 0.012	−0.068 ± 0.012	–	−6.53 ± 0.24	1
20282203–5637024	– –	M8.5γ	0.0233 ± 0.0053	−0.0604 ± 0.0106	–	–	10
20334473–5635338	– –	L0γ	0.016 ± 0.0061	−0.0731 ± 0.0125	–	–	10
20391314–1126531	M8–	M7β	0.0485 ± 0.009	−0.0898 ± 0.009	–	–	10
20575409–0252302	L1.5–	L2β	0.00160 ± 0.0038	−0.0863 ± 0.0039	70.1 ± 3.7	−24.68 ± 0.61	8
PSO318	– –	L6-L8γ	0.13730 ± 0.0013	−0.1387 ± 0.0014	40.7 ± 2.4	−6.0${}_{-1.1}^{+0.8}$	21, 23
21265040–8140293	L3γ	L3γ	0.05560 ± 0.0014	−0.1018 ± 0.003	31.3 ± 2.6	10.03 ± 0.49	1
21324036+1029494	– –	L4β	0.1078 ± 0.0164	0.0297 ± 0.0181	–	–	10
21543454–1055308	L4β	L5γ	0.17500 ± 0.012	0.009 ± 0.012	–	–	1
21544859–7459134	– –	M9.5β	0.0407 ± 0.0022	−0.0796 ± 0.0122	(21 ± 7)	(6.21 ± 3.1)	1, 10
21572060+8340575	L0–	M9γ	0.1248 ± 0.0008	0.0441 ± 0.0154	–	–	10
22025794–5605087	– –	M9γ	0.0496 ± 0.0052	−0.0696 ± 0.0103	–	–	10
22064498–4217208	L4γ	L4γa	0.128 ± 0.013	−0.181 ± 0.008	(35 ± 2)	(7.6 ± 2.0)	1
22081363+2921215	L3γ	L3γ	0.09070 ± 0.003	−0.0162 ± 0.0037	21.2 ± 0.7	−15.59 ± 1.93	1, 6
22134491–2136079	L0γ	L0γ	0.06000 ± 0.011	−0.063 ± 0.017	–	−4.92 ± 4.18	1, 2
22351658–3844154	– –	L1.5γ	0.0505 ± 0.0078	−0.0757 ± 0.0109	(22 ± 2)	(−4.9 ± 3.1)	10
22353560–5906306	– –	M8.5β	0.0556 ± 0.0051	−0.081 ± 0.0108	(23 ± 5)	(1.71 ± 3.14)	1, 10
22443167+2043433	L6.5p–	L6-L8γa	0.252 ± 0.014	−0.214 ± 0.011	(54 ± 4)	(−15.5 ± 1.7)	1, 2
22495345+0044046	L4γ	L3β	0.07500 ± 0.018	0.026 ± 0.018	–	−3.26 ± 0.90	1, 2
23153135+0617146	L0γ	L0γ	0.05600 ± 0.012	−0.039 ± 0.012	–	−14.69 ± 0.52	1
23224684–3133231	L0β	L2β	−0.19480 ± 0.0074	−0.5273 ± 0.0075	58.6 ± 5.6	33.86 ± 1.11	1, 8
23225299–6151275	L2γ	L3γa	0.062 ± 0.01	−0.085 ± 0.009	(22 ± 1)	6.747 ± 0.75	1
23231347–0244360	M8.5–	M8β	0.0859 ± 0.0097	−0.0435 ± 0.0106	–	–	10
23255604–0259508	L3–	L1γ	0.0783 ± 0.0127	−0.0958 ± 0.011	–	–	10
23360735–3541489	– –	M9β	0.0696 ± 0.0082	−0.0807 ± 0.0099	–	–	10
23433470–3646021	– –	L3-L6γ	0.087 ± 0.0083	−0.0987 ± 0.0125	–	–	10
23453903+0055137	M9–	M9β	0.0841 ± 0.0134	−0.0461 ± 0.0117	–	–	10
23520507–1100435	M7–	M8β	0.0881 ± 0.009	−0.1145 ± 0.0085	–	–	10

Notes.

A spectral type with a ? indicates questionable or extremely uncertain gravity features.

^aThese sources have new infrared spectra presented in this paper. In the majority of cases, we use the infrared spectral type and gravity classification diagnosed in this work. If an object had SpeX data, then we default to the resultant type and classification with that data.Parallaxes in parentheses "( )" are kinematic distances. ^bThese sources were listed in Filippazzo et al. (2015) as members of associations but, as has been noted in Table 12, we have downgraded them to ambiguos young objects.

References. 1. This Paper, 2. Faherty et al. (2009), 3. Dahn et al. (2002), 4. Reiners & Basri (2009), 5. Marocco et al. (2013), 6. Zapatero Osorio et al. (2014), 7. Gizis et al. (2015), 8. Faherty et al. (2012), 9. Riedel (2015), 10. Gagné et al. (2015b), 11. Vrba et al. (2004), 12. Shkolnik et al. (2012), 13. Dieterich et al. (2014), 14. Blake et al. (2010), 15. Weinberger et al. (2013), 16. Mohanty et al. (2003), 17. Gagné et al. (2014a), 18. Teixeira et al. (2008), 19. Ducourant et al. (2014), 20. Schneider et al. (2014), 21. Liu et al. (2013), 22. Sahlmann et al. (2016), 23. Allers et al. (2016), 24. Henry et al. (2006), 25. Tinney et al. (1995), 26. Dittmann et al. (2014), 27. Kellogg et al. (2016), 28. Schneider et al. (2016).

Download table as:  ASCIITypeset images: 1 2 3

As discussed in Section 2, there are 51 objects classified optically as γ and 80 with the equivalent infrared classification. There are also 27 objects classified optically as β and 57 with the equivalent infrared classification. Given the gravity indications, we regard each object as a potentially young source and investigate membership in a group within 100 pc of the Sun. To assess the likelihood of membership, we employed four different tools to examine the available kinematic data:

• 1.  
  BANYAN I Bayesian statistical calculator (Malo et al. 2013) and its successor,
• 2.  
  BANYAN II (Gagné et al. 2014c),
• 3.  
  LACEwING (Riedel 2015), and
• 4.  
  Convergent point method of Rodriguez et al. (2013).

The plurality of measurements in combination with a visual inspection of an objects kinematics against bona fide members (BMs) listed in (Malo et al. 2013) along with the individual kinematic boxes of Zuckerman & Song (2004) drove our decision on group membership.

The four different methods test for membership in different sets of groups—LACEwING considers 14 distinct groups, BANYAN I and II consider 7 groups (or 8 including the "Old" object classification), and the convergence method tests for membership in 6 groups. Each method has its benefits and flaws. For instance Banyan I is a fast bayesian formalism that uses flat priors but assumes (probably unrealistically) that radial velocity, and proper motion in a given direction are Gaussian. Banyan II deals better with transforming measurements to probabilities based on the distribution of known members (does not assume a Gaussian distribution) however it likely has incomplete/imperfect lists of bona fide members. LACEwING is similar to Banyan I in its assumption that radial velocity, and proper motion in a given direction are Gaussian but it requires fitting a model to a (arguably much cleaner list of) bona fide members of multiple groups not covered by the other methods. The convergent point method is a simple yet different approach that estimates the probability of membership in a known group by measuring the proper motions in directions parallel and perpendicular to the ___location of a given groups convergent point. Unfortunately, this method does not take into account measured radial velocities or distances. Given the benefits and flaws of each method, we chose to take the output of each into consideration as we decided on membership for each target. For an adequate comparison, we only considered membership in six groups: TW Hydrae, β Pictoris, Tucana Horologium, Columba, Argus (which is not tested by the Convergence code), and AB Doradus. All other groups could not be consistently checked. Therefore they may be mentioned (e.g., Chamaeleon near, Octans, Hyades) but are only considered tentative until further kinematic investigation.

Furthermore, the output of each code should be viewed slightly differently. In Malo et al. (2013), the authors adopt a membership probability threshold of 90% to recover BMs. Banyan II supplements with a contamination probability and finds this number should be less than a few percent with a high membership probability (we impose >90% based on Banyan I) in order to recover BMs (Gagné et al. 2014c). LACEwING (as described in Riedel 2015) finds <20%–60% is low probability and >60% is high probability for group membership. Convergent point reports distinct probabilities for each group between 0%–100% (hence objects can have >90% probability of membership in more than one group). As with Banyan I, we impose >90% as a high probability threshold for membership on convergent point as well.

In assessing the membership probability, we found four different categories for describing an object:

• 1.  
  Non-member (NM): an object that is kinematically eliminated from falling into a nearby group regardless of future astrometric measurements;
• 2.  
  Ambiguous member (AM): an object that requires updated astrometric precision because it could either belong to more than one group or it cannot be differentiated from the field;
• 3.  
  High-likelihood member (HLM): an object that does not have full kinematics but is regarded as high confidence (>90% in Banayan I, >90% in Banyan II with <5% contamination, >90% in convergent point, >60% in LACEwING) in three of the four codes; and
• 4.  
  BM: an object regarded as a high-likelihood member with full kinematics (parallax, proper motion, radial velocity) demonstrating that it is in line with known higher-mass BMs of nearby groups.

6.1. Full Kinematic Sample