Abstract

By using images taken with Wide Field Camera (WFCAM) on United Kingdom Infrared Telescope (UKIRT) and Son of ISAAC (SofI) on the New Technology Telescope (NTT) and combining them with Two Micron All Sky Survey (2MASS) we have measured proper motions for 126 L and T dwarfs in the dwarf archive. Two of these L dwarfs appear to have M dwarf common proper motion companions, and two also appear to be high-velocity dwarfs, indicating possible membership of the thick disc. We have also compared the motion of these 126 objects to that of numerous moving groups, and have identified new members of the Hyades, Ursa Major and Pleiades moving groups. These new objects, as well as those identified in Jameson et al. have allowed us to refine the L dwarf sequence for Ursa Major that was defined by Jameson et al.

1 INTRODUCTION

Brown dwarfs may be thought of as failed stars. These low-mass (≤70MJup; Burrows et al. 2001), cool objects are the lowest mass objects that the star formation process can produce. The majority of the brown dwarfs that have been discovered to date are field objects found using surveys such as the Two Micron All Sky Survey (2MASS; Skrutskie et al. 2006, see Leggett et al. 2002 for examples), the Deep Near-Infrared Sky survey (DENIS; DENIS Consortium 2005, see Delfosse et al. 1999 for examples), the Sloan Digital Sky Survey (SDSS; York et al. 2000, see Hawley et al. 2002 for examples) and the UKIRT (United Kingdom Infrared Telescope) Deep Infrared Sky Survey (UKIDSS; Lawrence et al. 2007, see Kendall et al. 2007; Lodieu et al. 2007b for examples). However, to study brown dwarfs in depth, a knowledge of their age is essential, which means we must study brown dwarfs in open star clusters or moving groups.

Once a brown dwarf has been proved to belong to an open star cluster, or a moving group, then its age is known, allowing meaningful comparisons to evolutionary models to be made. The most recent example of this is the study done by Bannister & Jameson (2007) who used existing proper motions and parallax measurements to show that a selection of field dwarfs in fact belong to the Ursa Major and Hyades moving groups. The importance of this study is that these are the first brown dwarfs to be associated with an older cluster or group (age >200 Myr). Older clusters such as the Hyades are expected to contain very few or no brown dwarfs or low-mass members, due to the dynamical evolution of the cluster over time (Adams et al. 2002). However, these escaped low-mass objects may remain members of the much larger moving group that surrounds the cluster.

Jameson et al. (2008a) followed this work by using the Wide Field Camera (WFCAM; Casali et al. 2007) on the UKIRT to image 143 known field L dwarfs. These images provided a second epoch for proper motion measurements, when combined with existing 2MASS images, typically taken 7 yr before. Using the proper motions and a distance calculated using the spectral type of the L dwarf given by Cruz et al. (2003), the moving group method was applied, and all 143 objects were scrutinized to check if their direction and magnitude of motion made them candidates of the many moving groups known. Members of the Hyades, Ursa Major and Pleiades moving groups were found. Radial velocity measurements such as those of Zapatero Osorio et al. (2007) are required, however, before it can be determined if these moving group members are cluster members that have ‘escaped’ as the cluster has dynamically evolved (Adams et al. 2002). It should also be noted that galactic resonances can produce effects similar to moving groups, and so all members may not be coeval (Dehnen 1998).

To continue the study started by Bannister & Jameson (2007) and Jameson et al. (2008a), we have measured proper motions for the majority of the remaining known field L dwarfs listed in the online L and T dwarf archive (http://spider.ipac.caltech.edu/staff/davy/ARCHIVE/). This has again been accomplished using the WFCAM on UKIRT and for the more southern objects, Son of ISAAC (SofI) on the 3.58-m ESO New Technology Telescope (NTT). Using these wide field images and existing catalogue data, we have measured proper motions for an additional 126 L and T dwarfs listed in the dwarf archive.

These proper motion data may be put to a number of uses. Using reduced proper motion diagrams they can be used as an approximate measure of distance. The proper motion measurements can also be used to help identify objects as members of a star cluster or members of a moving group via the moving cluster method. Taken with measured radial velocities and distances, it can yield all three components of velocity (U, V, W). As brown dwarfs tend to be faint, measuring their radial velocities is very difficult. As a result, very few L or T dwarfs have measurements, none of which is in this sample. This means we cannot determine whether these moving group members are escaped cluster members or otherwise.

Our proper motion data are discussed and listed in Section 2 of this paper.

2 PROPER MOTION MEASUREMENTS

2.1 Data acquisition and reduction

In order to measure proper motions for known L and T dwarfs we observed a sample of the known L and T dwarfs from the online dwarf archive (detailed in Tables 1 and 2, see http://spider.ipac.caltech.edu/staff/davy/ARCHIVE/ for discovery references) with J-band magnitudes of less than 16.5. 143 of these objects were presented in Jameson et al. (2008a). To complete the sample, 126 additional objects have been observed, 88 with declination (Dec.) between −30° and +60°, and 38 with Dec. of less than −30°. This first group were imaged using WFCAM on UKIRT over the period of 2006 June to 2008 March. WFCAM is a near-infrared imager consisting of four Rockwell Hawaii-II (HgCdTe 2048 × 2048) arrays arranged such that four separately pointed observations can be tiled together to cover a filled square of sky covering 0.75 deg2 with 0.4 arcsec pixel (Casali et al. 2007). However, as we only required the image of the brown dwarf in question, we only used array 3 which is regarded as the least noisy array. WFCAM is ideal for this work, as the large field of view per chip means there are many other stars in the image, which can be used as astrometric reference stars. The images were taken in the J band in non-photometric conditions using exposure times of ≈5–10 min and a nine-point dither pattern. These exposure times gave signal-to-noise ratio (S/N) ≈ 100 even in the poor conditions.

Table 1

2MASS name, RA, Dec., μα cos δ, μδ and 2MASS magnitudes for all the L and T dwarfs for which we measured proper motions using SofI.

Name 2MASS RA Dec. μα cos δ μδ J H KS 
(J2000) (mas yr−1
J00145575−4844171 00 14 55.76 −48 44 17.15 851.29 ± 12.38 279.42 ± 8.02 14.050 ± 0.033 13.107 ± 0.035 12.723 ± 0.028 
J00165953−4056541 00 16 59.53 −40 56 54.15 162.51 ± 14.44 16.06 ± 5.38 15.316 ± 0.060 14.206 ± 0.047 13.432 ± 0.037 
J00325584−4405058 00 32 55.84 −44 05 05.87 116.76 ± 7.85 −88.96 ± 5.45 14.776 ± 0.032 13.857 ± 0.032 13.269 ± 0.035 
J00531899−3631102 00 53 18.99 −36 31 10.29 36.82 ± 22.71 −72.41 ± 8.57 14.445 ± 0.023 13.480 ± 0.030 12.937 ± 0.027 
J01174748−3403258 01 17 47.48 −34 03 25.82 103.14 ± 13.98 −39.70 ± 7.00 15.178 ± 0.034 14.209 ± 0.038 13.489 ± 0.036 
J01253689−3435049 01 25 36.90 −34 35 04.91 120.42 ± 42.95 −12.97 ± 21.05 15.522 ± 0.054 14.474 ± 0.051 13.898 ± 0.054 
J01415823−4633574 01 41 58.23 −46 33 57.43 92.90 ± 10.43 −5.54 ± 8.27 14.832 ± 0.041 13.875 ± 0.024 13.097 ± 0.030 
J02182913−3133230 02 18 29.13 −31 33 23.08 −131.09 ± 9.87 −97.18 ± 16.69 14.728 ± 0.038 13.808 ± 0.036 13.154 ± 0.033 
J02550357−4700509 02 55 03.58 −47 00 50.99 1052.88 ± 11.17 −546.54 ± 6.17 13.246 ± 0.024 12.204 ± 0.022 11.558 ± 0.023 
J03185403−3421292 03 18 54.04 −34 21 29.22 401.63 ± 9.93 43.28 ± 4.10 15.569 ± 0.053 14.346 ± 0.043 13.507 ± 0.038 
J03572695−4417305 03 57 26.96 −44 17 30.55 63.15 ± 12.71 2.35 ± 7.54 14.367 ± 0.029 13.531 ± 0.025 12.907 ± 0.026 
J04430581−3202090 04 43 05.81 −32 02 09.01 −0.46 ± 13.70 205.19 ± 7.54 15.273 ± 0.050 14.350 ± 0.055 13.877 ± 0.062 
J04455387−3048204 04 45 53.88 −30 48 20.46 158.07 ± 9.33 −402.39 ± 5.36 13.393 ± 0.023 12.580 ± 0.022 11.975 ± 0.019 
J04510093−3402150 04 51 00.93 −34 02 15.04 76.34 ± -8.05 166.66 ± -8.01 13.541 ± 0.020 12.826 ± 0.022 12.294 ± 0.024 
J06244595−4521548 06 24 45.95 −45 21 54.88 −49.71 ± 37.67 392.74 ± 13.81 14.480 ± 0.026 13.335 ± 0.027 12.595 ± 0.024 
J06411840−4322329 06 41 18.40 −43 22 32.93 216.60 ± 15.76 642.33 ± 9.93 13.751 ± 0.023 12.941 ± 0.032 12.451 ± 0.027 
J07193188−5051410 07 19 31.88 −50 51 41.06 199.11 ± 20.49 −46.44 ± 13.78 14.094 ± 0.029 13.282 ± 0.033 12.773 ± 0.026 
J09221952−8010399 09 22 19.52 −80 10 39.93 3.39 ± 43.54 −66.69 ± 9.36 15.276 ± 0.053 14.285 ± 0.033 13.681 ± 0.046 
J10043929−3335189 10 04 39.29 −33 35 18.91 365.99 ± 25.14 −350.34 ± 14.46 14.480 ± 0.032 13.490 ± 0.035 12.924 ± 0.023 
J10365305−3441380 10 36 53.06 −34 41 38.09 −32.54 ± 26.06 −445.75 ± 18.42 15.622 ± 0.046 14.446 ± 0.034 13.798 ± 0.042 
J11223624−3916054 11 22 36.24 −39 16 05.49 55.74 ± 15.95 −171.34 ± 15.39 15.705 ± 0.059 14.682 ± 0.046 13.875 ± 0.052 
J11544223−3400390 11 54 42.23 −34 00 39.06 −158.55 ± 13.23 28.35 ± 13.07 14.195 ± 0.031 13.331 ± 0.027 12.851 ± 0.032 
J12073804−3909050 12 07 38.04 −39 09 05.09 −134.78 ± 24.57 51.10 ± 12.76 14.689 ± 0.038 13.817 ± 0.026 13.244 ± 0.037 
J13411160−3052505 13 41 11.60 −30 52 50.53 35.45 ± 30.00 −126.20 ± 18.70 14.607 ± 0.031 13.725 ± 0.032 13.081 ± 0.024 
J13595510−4034582 13 59 55.10 −40 34 58.27 44.60 ± 17.69 −491.51 ± 14.21 13.645 ± 0.023 13.034 ± 0.027 12.566 ± 0.027 
J14252798−3650229 14 25 27.98 −36 50 23.00 −253.11 ± 23.59 −448.55 ± 28.18 13.747 ± 0.026 12.575 ± 0.020 11.805 ± 0.025 
J17534518−6559559 17 53 45.18 −65 59 55.91 −50.42 ± 78.51 −329.02 ± 35.82 14.095 ± 0.025 13.108 ± 0.026 12.424 ± 0.027 
J19285196−4356256 19 28 51.97 −43 56 25.64 81.24 ± 17.23 −265.82 ± 25.87 15.199 ± 0.042 14.127 ± 0.043 13.457 ± 0.036 
J19360187−5502322 19 36 01.88 −55 02 32.22 210.17 ± 32.98 −273.20 ± 21.09 14.486 ± 0.037 13.628 ± 0.034 13.046 ± 0.031 
J20414283−3506442 20 41 42.83 −35 06 44.27 56.16 ± 15.79 −118.14 ± 13.02 14.887 ± 0.031 13.987 ± 0.020 13.401 ± 0.036 
J21075409−4544064 21 07 54.09 −45 44 06.47 114.58 ± 40.06 −7.85 ± 30.98 14.915 ± 0.029 13.953 ± 0.037 13.380 ± 0.033 
J21420580−3101162 21 42 05.80 −31 01 16.29 45.95 ± 6.20 −97.31 ± 5.09 15.844 ± 0.066 14.767 ± 0.053 13.965 ± 0.050 
J21501592−7520367 21 50 15.93 −75 20 36.73 869.96 ± 22.08 −277.81 ± 6.55 14.056 ± 0.026 13.176 ± 0.031 12.673 ± 0.029 
J21574904−5534420 21 57 49.04 −55 34 42.05 38.93 ± 24.51 −4.58 ± 12.31 14.263 ± 0.029 13.440 ± 0.028 13.002 ± 0.029 
J22064498−4217208 22 06 44.98 −42 17 20.89 140.24 ± 10.35 −174.18 ± 4.41 15.555 ± 0.065 14.447 ± 0.061 13.609 ± 0.055 
J23312378−4718274 23 31 23.79 −47 18 27.44 72.07 ± 40.02 0.33 ± 28.02 15.659 ± 0.067 15.510 ± 0.149 15.389 ± 0.196 
Name 2MASS RA Dec. μα cos δ μδ J H KS 
(J2000) (mas yr−1
J00145575−4844171 00 14 55.76 −48 44 17.15 851.29 ± 12.38 279.42 ± 8.02 14.050 ± 0.033 13.107 ± 0.035 12.723 ± 0.028 
J00165953−4056541 00 16 59.53 −40 56 54.15 162.51 ± 14.44 16.06 ± 5.38 15.316 ± 0.060 14.206 ± 0.047 13.432 ± 0.037 
J00325584−4405058 00 32 55.84 −44 05 05.87 116.76 ± 7.85 −88.96 ± 5.45 14.776 ± 0.032 13.857 ± 0.032 13.269 ± 0.035 
J00531899−3631102 00 53 18.99 −36 31 10.29 36.82 ± 22.71 −72.41 ± 8.57 14.445 ± 0.023 13.480 ± 0.030 12.937 ± 0.027 
J01174748−3403258 01 17 47.48 −34 03 25.82 103.14 ± 13.98 −39.70 ± 7.00 15.178 ± 0.034 14.209 ± 0.038 13.489 ± 0.036 
J01253689−3435049 01 25 36.90 −34 35 04.91 120.42 ± 42.95 −12.97 ± 21.05 15.522 ± 0.054 14.474 ± 0.051 13.898 ± 0.054 
J01415823−4633574 01 41 58.23 −46 33 57.43 92.90 ± 10.43 −5.54 ± 8.27 14.832 ± 0.041 13.875 ± 0.024 13.097 ± 0.030 
J02182913−3133230 02 18 29.13 −31 33 23.08 −131.09 ± 9.87 −97.18 ± 16.69 14.728 ± 0.038 13.808 ± 0.036 13.154 ± 0.033 
J02550357−4700509 02 55 03.58 −47 00 50.99 1052.88 ± 11.17 −546.54 ± 6.17 13.246 ± 0.024 12.204 ± 0.022 11.558 ± 0.023 
J03185403−3421292 03 18 54.04 −34 21 29.22 401.63 ± 9.93 43.28 ± 4.10 15.569 ± 0.053 14.346 ± 0.043 13.507 ± 0.038 
J03572695−4417305 03 57 26.96 −44 17 30.55 63.15 ± 12.71 2.35 ± 7.54 14.367 ± 0.029 13.531 ± 0.025 12.907 ± 0.026 
J04430581−3202090 04 43 05.81 −32 02 09.01 −0.46 ± 13.70 205.19 ± 7.54 15.273 ± 0.050 14.350 ± 0.055 13.877 ± 0.062 
J04455387−3048204 04 45 53.88 −30 48 20.46 158.07 ± 9.33 −402.39 ± 5.36 13.393 ± 0.023 12.580 ± 0.022 11.975 ± 0.019 
J04510093−3402150 04 51 00.93 −34 02 15.04 76.34 ± -8.05 166.66 ± -8.01 13.541 ± 0.020 12.826 ± 0.022 12.294 ± 0.024 
J06244595−4521548 06 24 45.95 −45 21 54.88 −49.71 ± 37.67 392.74 ± 13.81 14.480 ± 0.026 13.335 ± 0.027 12.595 ± 0.024 
J06411840−4322329 06 41 18.40 −43 22 32.93 216.60 ± 15.76 642.33 ± 9.93 13.751 ± 0.023 12.941 ± 0.032 12.451 ± 0.027 
J07193188−5051410 07 19 31.88 −50 51 41.06 199.11 ± 20.49 −46.44 ± 13.78 14.094 ± 0.029 13.282 ± 0.033 12.773 ± 0.026 
J09221952−8010399 09 22 19.52 −80 10 39.93 3.39 ± 43.54 −66.69 ± 9.36 15.276 ± 0.053 14.285 ± 0.033 13.681 ± 0.046 
J10043929−3335189 10 04 39.29 −33 35 18.91 365.99 ± 25.14 −350.34 ± 14.46 14.480 ± 0.032 13.490 ± 0.035 12.924 ± 0.023 
J10365305−3441380 10 36 53.06 −34 41 38.09 −32.54 ± 26.06 −445.75 ± 18.42 15.622 ± 0.046 14.446 ± 0.034 13.798 ± 0.042 
J11223624−3916054 11 22 36.24 −39 16 05.49 55.74 ± 15.95 −171.34 ± 15.39 15.705 ± 0.059 14.682 ± 0.046 13.875 ± 0.052 
J11544223−3400390 11 54 42.23 −34 00 39.06 −158.55 ± 13.23 28.35 ± 13.07 14.195 ± 0.031 13.331 ± 0.027 12.851 ± 0.032 
J12073804−3909050 12 07 38.04 −39 09 05.09 −134.78 ± 24.57 51.10 ± 12.76 14.689 ± 0.038 13.817 ± 0.026 13.244 ± 0.037 
J13411160−3052505 13 41 11.60 −30 52 50.53 35.45 ± 30.00 −126.20 ± 18.70 14.607 ± 0.031 13.725 ± 0.032 13.081 ± 0.024 
J13595510−4034582 13 59 55.10 −40 34 58.27 44.60 ± 17.69 −491.51 ± 14.21 13.645 ± 0.023 13.034 ± 0.027 12.566 ± 0.027 
J14252798−3650229 14 25 27.98 −36 50 23.00 −253.11 ± 23.59 −448.55 ± 28.18 13.747 ± 0.026 12.575 ± 0.020 11.805 ± 0.025 
J17534518−6559559 17 53 45.18 −65 59 55.91 −50.42 ± 78.51 −329.02 ± 35.82 14.095 ± 0.025 13.108 ± 0.026 12.424 ± 0.027 
J19285196−4356256 19 28 51.97 −43 56 25.64 81.24 ± 17.23 −265.82 ± 25.87 15.199 ± 0.042 14.127 ± 0.043 13.457 ± 0.036 
J19360187−5502322 19 36 01.88 −55 02 32.22 210.17 ± 32.98 −273.20 ± 21.09 14.486 ± 0.037 13.628 ± 0.034 13.046 ± 0.031 
J20414283−3506442 20 41 42.83 −35 06 44.27 56.16 ± 15.79 −118.14 ± 13.02 14.887 ± 0.031 13.987 ± 0.020 13.401 ± 0.036 
J21075409−4544064 21 07 54.09 −45 44 06.47 114.58 ± 40.06 −7.85 ± 30.98 14.915 ± 0.029 13.953 ± 0.037 13.380 ± 0.033 
J21420580−3101162 21 42 05.80 −31 01 16.29 45.95 ± 6.20 −97.31 ± 5.09 15.844 ± 0.066 14.767 ± 0.053 13.965 ± 0.050 
J21501592−7520367 21 50 15.93 −75 20 36.73 869.96 ± 22.08 −277.81 ± 6.55 14.056 ± 0.026 13.176 ± 0.031 12.673 ± 0.029 
J21574904−5534420 21 57 49.04 −55 34 42.05 38.93 ± 24.51 −4.58 ± 12.31 14.263 ± 0.029 13.440 ± 0.028 13.002 ± 0.029 
J22064498−4217208 22 06 44.98 −42 17 20.89 140.24 ± 10.35 −174.18 ± 4.41 15.555 ± 0.065 14.447 ± 0.061 13.609 ± 0.055 
J23312378−4718274 23 31 23.79 −47 18 27.44 72.07 ± 40.02 0.33 ± 28.02 15.659 ± 0.067 15.510 ± 0.149 15.389 ± 0.196 
Table 2

2MASS name, RA, Dec., μα cos δ, μδ and 2MASS magnitudes for all the L and T dwarfs for which we measured proper motions using WFCAM.

Name 2MASS RA Dec. μα cos δ μδ J H KS 
(J2000) (mas yr−1
J00135779−2235200 00 13 57.80 −22 35 20.09 57.74 ± 23.76 −60.74 ± 21.38 15.775 ± 0.064 14.595 ± 0.062 14.036 ± 0.050 
J00332386−1521309 00 33 23.86 −15 21 30.94 330.31 ± 16.25 46.33 ± 22.26 15.286 ± 0.055 14.208 ± 0.051 13.410 ± 0.038 
J00345684−0706013 00 34 56.84 −07 06 01.32 215.35 ± 21.32 −138.55 ± 15.29 15.531 ± 0.059 14.566 ± 0.041 13.942 ± 0.065 
J00511078−1544169 00 51 10.79 −15 44 16.91 76.37 ± 24.08 −4.25 ± 19.61 15.277 ± 0.049 14.164 ± 0.047 13.466 ± 0.038 
J00584253−0651239 00 58 42.53 −06 51 23.94 158.29 ± 20.18 −105.96 ± 15.76 14.311 ± 0.023 13.444 ± 0.028 12.904 ± 0.032 
J01311838+3801554 01 31 18.39 38 01 55.48 393.88 ± 15.45 −21.70 ± 13.25 14.679 ± 0.032 13.696 ± 0.033 13.054 ± 0.033 
J01353586+1205216 01 35 35.86 12 05 21.67 −45.23 ± 14.82 −441.77 ± 14.08 14.412 ± 0.030 13.527 ± 0.031 12.918 ± 0.028 
J01410321+1804502 01 41 03.22 18 04 50.20 425.05 ± 17.35 −32.16 ± 16.50 13.875 ± 0.022 13.034 ± 0.024 12.492 ± 0.026 
J01443536−0716142 01 44 35.36 −07 16 14.23 408.28 ± 17.56 −187.65 ± 17.99 14.191 ± 0.023 13.008 ± 0.027 12.268 ± 0.021 
J01473344+3453112 01 47 33.45 34 53 11.24 47.24 ± 18.30 −47.19 ± 14.84 14.946 ± 0.037 14.162 ± 0.040 13.574 ± 0.037 
J02050344+1251422 02 05 03.44 12 51 42.23 388.84 ± 12.17 −8.71 ± 12.15 15.679 ± 0.055 14.449 ± 0.046 13.671 ± 0.035 
J02073557+1355564 02 07 35.57 13 55 56.45 259.66 ± 12.71 −159.71 ± 13.59 15.462 ± 0.048 14.474 ± 0.043 13.808 ± 0.045 
J02085499+2500488 02 08 55.00 25 00 48.82 0.71 ± 15.49 25.63 ± 11.047 16.206 ± 0.092 14.974 ± 0.080 14.405 ± 0.069 
J02081833+2542533 02 08 18.33 25 42 53.31 386.59 ± 14.268 −25.14 ± 16.73 13.989 ± 0.023 13.107 ± 0.029 12.588 ± 0.025 
J02082363+2737400 02 08 23.64 27 37 40.09 231.06 ± 11.62 −95.82 ± 16.35 15.714 ± 0.059 14.560 ± 0.059 13.872 ± 0.051 
J02112827+1410039 02 11 28.28 14 10 03.95 −66.39 ± 13.83 −27.22 ± 13.39 16.128 ± 0.077 15.423 ± 0.089 15.009 ± 0.123 
J02132880+4444453 02 13 28.80 44 44 45.36 −42.20 ± 13.86 −132.39 ± 13.23 13.494 ± 0.021 12.757 ± 0.023 12.213 ± 0.021 
J02271036−1624479 02 27 10.36 −16 24 47.95 438.00 ± 18.91 −286.59 ± 18.81 13.573 ± 0.020 12.630 ± 0.022 12.143 ± 0.029 
J02301551+2704061 02 30 15.51 27 04 06.18 198.10 ± 15.38 −13.50 ± 13.63 14.294 ± 0.024 13.478 ± 0.028 12.986 ± 0.021 
J02354756−0849198 02 35 47.57 −08 49 19.80 −12.28 ± 16.75 21.33 ± 16.51 15.571 ± 0.054 14.812 ± 0.055 14.191 ± 0.066 
J02361794+0048548 02 36 17.94 00 48 54.82 161.33 ± 10.10 −176.33 ± 19.16 16.098 ± 0.076 15.265 ± 0.066 14.666 ± 0.090 
J02394245−1735471 02 39 42.46 −17 35 47.20 61.09 ± 13.80 −79.12 ± 18.79 14.291 ± 0.029 13.525 ± 0.034 13.039 ± 0.030 
J02411151−0326587 02 41 11.52 −03 26 58.78 93.43 ± 17.00 −19.87 ± 13.40 15.799 ± 0.064 14.811 ± 0.053 14.035 ± 0.049 
J02424355+1607392 02 42 43.55 16 07 39.27 163.62 ± 14.16 −198.32 ± 12.77 15.776 ± 0.052 14.998 ± 0.053 14.349 ± 0.057 
J02560189+0110467 02 56 01.89 01 10 46.71 66.48 ± 22.28 −62.38 ± 22.06 16.212 ± 0.102 15.696 ± 0.184 15.216 ± 0.175 
J03090888−1949387 03 09 08.89 −19 49 38.76 218.00 ± 11.57 −13.33 ± 11.90 15.752 ± 0.055 14.656 ± 0.062 14.057 ± 0.065 
J03101401−2756452 03 10 14.01 −27 56 45.27 −118.89 ± 17.61 −46.70 ± 16.21 15.795 ± 0.070 14.662 ± 0.049 13.959 ± 0.060 
J03105986+1648155 03 11 00.02 16 48 15.68 262.83 ± 19.28 9.38 ± 17.90 16.025 ± 0.083 14.932 ± 0.070 14.312 ± 0.067 
J03140344+1603056 03 14 03.45 16 03 05.63 −244.73 ± 13.31 −49.07 ± 13.91 12.526 ± 0.021 11.823 ± 0.035 11.238 ± 0.019 
J03164512−2848521 03 16 45.13 −28 48 52.17 105.25 ± 22.15 −80.97 ± 2 12.88 14.578 ± 0.039 13.772 ± 0.035 13.114 ± 0.035 
J03202839−0446358 03 20 28.24 −04 46 40.59 −249.91 ± 17.00 −501.77 ± 12.26 13.259 ± 0.021 12.535 ± 0.022 12.134 ± 0.024 
J03264225−2102057 03 26 42.26 −21 02 05.77 103.12 ± 16.14 −129.87 ± 18.72 16.134 ± 0.093 14.793 ± 0.075 13.922 ± 0.065 
J03281738+0032572 03 28 17.49 00 32 57.57 201.84 ± 22.19 35.50 ± 17.21 15.988 ± 0.091 14.975 ± 0.074 14.161 ± 0.077 
J03301774+0000477 03 30 17.74 00 00 47.44 −8.29 ± 11.88 −33.00 ± 11.08 16.520 ± 0.111 15.881 ± 0.130 15.525 ± 0.182 
J03504861−0518126 03 50 48.61 −05 18 12.70 19.91 ± 11.31 −8.04 ± 15.59 16.327 ± 0.092 15.525 ± 0.094 15.125 ± 0.134 
J03552337+1133437 03 55 23.37 11 33 43.71 223.16 ± 22.90 −607.16 ± 22.07 14.050 ± 0.020 12.530 ± 0.029 11.526 ± 0.019 
J03554191+2257016 03 55 41.91 22 57 01.68 171.90 ± 13.14 −21.38 ± 10.33 16.111 ± 0.077 15.052 ± 0.068 14.284 ± 0.060 
J03572110−0641260 03 57 21.10 −06 41 26.04 133.59 ± 22.58 27.12 ± 5 25.51 15.953 ± 0.081 15.060 ± 0.085 14.599 ± 0.089 
J04070885+1514565 04 07 08.85 15 14 56.60 97.97 ± 16.28 −74.65 ± 17.40 16.055 ± 0.091 16.017 ± 0.208 15.922 ± 0.261 
J04082905−1450334 04 08 29.18 −14 50 34.33 193.43 ± 11.35 −99.07 ± 17.75 14.222 ± 0.028 13.337 ± 0.029 12.817 ± 0.021 
J04090950+2104393 04 09 09.51 21 04 39.38 101.13 ± 15.14 −148.46 ± 12.25 15.508 ± 0.053 14.497 ± 0.045 13.850 ± 0.046 
J04132039−0114248 04 13 20.39 −01 14 24.86 61.22 ± 15.29 0.08 ± 18.67 15.303 ± 0.047 14.657 ± 0.033 14.135 ± 0.059 
J04285096−2253227 04 28 51.05 −22 53 21.0 123.44 ± 16.02 183.48 ± 15.70 13.507 ± 0.020 12.668 ± 0.026 12.118 ± 0.024 
J04390101−2353083 04 39 00.93 −23 53 09.51 −119.29 ± 22.66 −127.25 ± 15.05 14.408 ± 0.026 13.409 ± 0.027 12.816 ± 0.021 
J04532647−1751543 04 53 26.51 −17 51 54.35 50.80 ± 14.38 −4.14 ± 14.30 15.142 ± 0.033 14.060 ± 0.034 13.466 ± 0.034 
J05012406−0010452 05 01 24.19 00 10 46.58 192.82 ± 11.98 −139.86 ± 12.29 14.982 ± 0.036 13.713 ± 0.033 12.963 ± 0.034 
J05021345+1442367 05 02 13.45 14 42 36.78 71.55 ± 13.68 −1.04 ± 18.53 14.271 ± 0.022 13.392 ± 0.019 12.955 ± 0.028 
J05120636−2949540 05 12 06.36 −29 49 53.12 −6.40 ± 13.41 96.87 ± 12.28 15.463 ± 0.055 14.156 ± 0.047 13.285 ± 0.041 
J05184616−2756457 05 18 46.19 −27 56 45.69 37.27 ± 17.01 10.72 ± 19.72 15.262 ± 0.041 14.295 ± 0.045 13.615 ± 0.039 
J05233822−1403022 05 23 38.22 −14 03 02.29 109.87 ± 17.14 178.88 ± 21.12 13.084 ± 0.021 12.220 ± 0.020 11.638 ± 0.025 
J06050196−2342270 06 05 01.96 −23 42 27.01 −66.48 ± 15.90 117.68 ± 18.21 14.512 ± 0.032 13.727 ± 0.035 13.145 ± 0.030 
J06262121+0029341 06 26 21.21 00 29 34.14 47.15 ± 12.94 1.03 ± 12.78 15.925 ± 0.093 15.209 ± 0.120 14.860 ± 0.123 
J06523073+4710348 06 52 30.74 47 10 34.83 −129.78 ± 14.67 149.52 ± 7 12.78 13.511 ± 0.020 12.384 ± 0.023 11.694 ± 0.018 
J07171626+5705430 07 17 16.27 57 05 43.05 −17.99 ± 17.87 67.17 ± 15.13 14.636 ± 0.029 13.593 ± 0.028 12.945 ± 0.025 
J07231462+5727081 07 23 14.62 57 27 08.17 61.39 ± 22.71 −219.85 ± 12.31 13.970 ± 0.024 13.156 ± 0.028 12.613 ± 0.029 
J07400966+3212032 07 40 09.67 32 12 03.24 −31.98 ± 11.79 −80.79 ± 13.45 16.191 ± 0.090 14.862 ± 0.059 14.222 ± 0.059 
J07414920+2351275 07 41 49.21 23 51 27.51 −250.22 ± 12.18 −116.21 ± 13.32 16.158 ± 0.100 15.838 ± 0.185 15.847 ± 99.99 
J07420130+2055198 07 42 01.30 20 55 19.88 −318.67 ± 12.08 −229.57 ± 13.15 16.193 ± 0.090 15.911 ± 0.181 15.225 ± 99.99 
J07475631+3947329 07 47 56.31 39 47 32.92 55.04 ± 14.43 −41.72 ± 13.26 15.076 ± 0.039 14.163 ± 0.038 13.724 ± 0.044 
J07525942+4136344 07 52 59.43 41 36 34.49 0.00 ± 13.39 43.98 ± 10.46 16.356 ± 0.130 15.601 ± 0.160 15.191 ± 99.99 
J07533217+2917119 07 53 32.17 29 17 11.93 −88.43 ± 11.08 −85.34 ± 13.12 15.516 ± 0.046 14.527 ± 0.039 13.849 ± 0.042 
J07554795+2212169 07 55 47.95 22 12 16.94 −9.87 ± 14.88 −226.48 ± 17.78 15.728 ± 0.063 15.669 ± 0.144 15.753 ± 0.207 
J07584037+3247245 07 58 40.37 32 47 24.55 −204.23 ± 18.01 −316.21 ± 12.42 14.947 ± 0.043 14.111 ± 0.041 13.879 ± 0.056 
J08014056+4628498 08 01 40.56 46 28 49.84 −194.73 ± 23.54 −331.056 ± 19.10 16.275 ± 0.133 15.452 ± 0.142 14.536 ± 0.100 
J08053189+4812330 08 05 31.89 48 12 33.10 −455.48 ± 14.62 61.35 ± 16.32 14.734 ± 0.034 13.917 ± 0.040 13.444 ± 0.040 
J08155674+4524119 08 15 56.75 45 24 11.93 −31.49 ± 15.56 −42.96 ± 13.18 16.057 ± 0.078 15.233 ± 0.093 14.812 ± 0.097 
J08202996+4500315 08 20 29.96 45 00 31.52 −104.16 ± 25.82 −299.16 ± 14.76 16.279 ± 0.107 15.000 ± 0.086 14.218 ± 0.065 
J08234818+2428577 08 23 48.18 24 28 57.71 −160.30 ± 19.81 73.19 ± 19.17 14.986 ± 0.042 14.060 ± 0.044 13.377 ± 0.029 
J08290664+1456225 08 29 06.64 14 56 22.56 −49.41 ± 16.67 −227.11 ± 18.47 14.750 ± 0.028 13.801 ± 0.035 13.166 ± 0.031 
J08304878+0128311 08 30 48.78 01 28 31.15 222.11 ± 15.89 −310.54 ± 15.36 16.289 ± 0.111 16.140 ± 0.213 16.358 ± 99.99 
J08320451−0128360 08 32 04.52 −01 28 36.05 63.83 ± 13.19 26.73 ± 15.10 14.128 ± 0.028 13.318 ± 0.022 12.712 ± 0.026 
J08355829+0548308 08 35 58.30 05 48 30.85 −109.70 ± 12.79 −15.00 ± 15.54 14.533 ± 0.034 13.683 ± 0.036 13.168 ± 0.033 
J08472872−1532372 08 47 28.73 −15 32 37.21 149.07 ± 16.12 −177.78 ± 15.82 13.513 ± 0.023 12.629 ± 0.026 12.061 ± 0.021 
J08523490+4720359 08 52 34.91 47 20 35.91 −28.69 ± 18.13 −386.53 ± 13.88 16.182 ± 0.108 15.419 ± 0.146 14.718 ± 0.116 
J08564793+2235182 08 56 47.94 22 35 18.21 −184.24 ± 19.74 3.01 ± 20.71 15.679 ± 0.064 14.580 ± 0.052 13.951 ± 0.046 
J08575849+5708514 08 57 58.49 57 08 51.42 −413.61 ± 20.52 −353.43 ± 16.85 15.038 ± 0.038 13.790 ± 0.041 12.962 ± 0.028 
J08592547−1949268 08 59 25.48 −19 49 26.89 −310.77 ± 13.51 −78.59 ± 15.95 15.527 ± 0.052 14.436 ± 0.041 13.751 ± 0.057 
J09095749−0658186 09 09 57.49 −06 58 18.64 −174.53 ± 14.89 39.70 ± 16.48 13.890 ± 0.021 13.090 ± 0.020 12.539 ± 0.024 
J09153413+0422045 09 15 34.14 04 22 04.59 −88.46 ± 18.02 40.27 ± 20.60 14.548 ± 0.028 13.531 ± 0.031 13.011 ± 0.041 
J09183815+2134058 09 18 38.16 21 34 05.82 353.41 ± 14.50 −454.02 ± 15.66 15.662 ± 0.060 14.580 ± 99.99 13.903 ± 0.042 
J09201223+3517429 09 20 12.23 35 17 42.97 −172.34 ± 13.35 −185.26 ± 12.72 15.625 ± 0.062 14.673 ± 0.056 13.979 ± 0.061 
J09211410−2104446 09 21 14.11 −21 04 44.60 260.71 ± 15.59 −900.91 ± 13.20 12.779 ± 0.021 12.152 ± 0.020 11.690 ± 0.021 
J09283972−1603128 09 28 39.72 −16 03 12.86 −132.85 ± 15.59 36.00 ± 13.20 15.322 ± 0.041 14.292 ± 0.036 13.615 ± 0.050 
J09352803−2934596 09 35 28.04 −29 34 59.62 8.84 ± 18.10 86.92 ± 14.61 14.036 ± 0.026 13.312 ± 0.027 12.822 ± 0.026 
J10185879−2909535 10 18 58.79 −29 09 53.56 −323.01 ± 21.04 −82.84 ± 15.20 14.213 ± 0.028 13.418 ± 0.022 12.796 ± 0.021 
J10432508+0001482 10 43 25.00 00 01 46.92 −159.31 ± 15.56 −143.85 ± 21.27 15.935 ± 0.080 15.208 ± 0.072 14.472 ± 0.100 
J12285538+0050440 12 28 55.37 00 50 43.94 -32.33 ± 3.54 −12.41 ± 2.06 15.613 ± 0.060 14.825 ± 0.059 14.162 ± 0.077 
J16360078−0034525 16 36 00.59 00 34 54.36 −344.71 ± 14.13 −200.89 ± 14.86 14.590 ± 0.043 13.904 ± 0.042 13.415 ± 0.035 
J17434148+2127069 17 43 41.59 21 27 09.16 165.91 ± 14.890 248.68 ± 14.47 15.830 ± 0.088 14.785 ± 0.064 14.321 ± 0.097 
Name 2MASS RA Dec. μα cos δ μδ J H KS 
(J2000) (mas yr−1
J00135779−2235200 00 13 57.80 −22 35 20.09 57.74 ± 23.76 −60.74 ± 21.38 15.775 ± 0.064 14.595 ± 0.062 14.036 ± 0.050 
J00332386−1521309 00 33 23.86 −15 21 30.94 330.31 ± 16.25 46.33 ± 22.26 15.286 ± 0.055 14.208 ± 0.051 13.410 ± 0.038 
J00345684−0706013 00 34 56.84 −07 06 01.32 215.35 ± 21.32 −138.55 ± 15.29 15.531 ± 0.059 14.566 ± 0.041 13.942 ± 0.065 
J00511078−1544169 00 51 10.79 −15 44 16.91 76.37 ± 24.08 −4.25 ± 19.61 15.277 ± 0.049 14.164 ± 0.047 13.466 ± 0.038 
J00584253−0651239 00 58 42.53 −06 51 23.94 158.29 ± 20.18 −105.96 ± 15.76 14.311 ± 0.023 13.444 ± 0.028 12.904 ± 0.032 
J01311838+3801554 01 31 18.39 38 01 55.48 393.88 ± 15.45 −21.70 ± 13.25 14.679 ± 0.032 13.696 ± 0.033 13.054 ± 0.033 
J01353586+1205216 01 35 35.86 12 05 21.67 −45.23 ± 14.82 −441.77 ± 14.08 14.412 ± 0.030 13.527 ± 0.031 12.918 ± 0.028 
J01410321+1804502 01 41 03.22 18 04 50.20 425.05 ± 17.35 −32.16 ± 16.50 13.875 ± 0.022 13.034 ± 0.024 12.492 ± 0.026 
J01443536−0716142 01 44 35.36 −07 16 14.23 408.28 ± 17.56 −187.65 ± 17.99 14.191 ± 0.023 13.008 ± 0.027 12.268 ± 0.021 
J01473344+3453112 01 47 33.45 34 53 11.24 47.24 ± 18.30 −47.19 ± 14.84 14.946 ± 0.037 14.162 ± 0.040 13.574 ± 0.037 
J02050344+1251422 02 05 03.44 12 51 42.23 388.84 ± 12.17 −8.71 ± 12.15 15.679 ± 0.055 14.449 ± 0.046 13.671 ± 0.035 
J02073557+1355564 02 07 35.57 13 55 56.45 259.66 ± 12.71 −159.71 ± 13.59 15.462 ± 0.048 14.474 ± 0.043 13.808 ± 0.045 
J02085499+2500488 02 08 55.00 25 00 48.82 0.71 ± 15.49 25.63 ± 11.047 16.206 ± 0.092 14.974 ± 0.080 14.405 ± 0.069 
J02081833+2542533 02 08 18.33 25 42 53.31 386.59 ± 14.268 −25.14 ± 16.73 13.989 ± 0.023 13.107 ± 0.029 12.588 ± 0.025 
J02082363+2737400 02 08 23.64 27 37 40.09 231.06 ± 11.62 −95.82 ± 16.35 15.714 ± 0.059 14.560 ± 0.059 13.872 ± 0.051 
J02112827+1410039 02 11 28.28 14 10 03.95 −66.39 ± 13.83 −27.22 ± 13.39 16.128 ± 0.077 15.423 ± 0.089 15.009 ± 0.123 
J02132880+4444453 02 13 28.80 44 44 45.36 −42.20 ± 13.86 −132.39 ± 13.23 13.494 ± 0.021 12.757 ± 0.023 12.213 ± 0.021 
J02271036−1624479 02 27 10.36 −16 24 47.95 438.00 ± 18.91 −286.59 ± 18.81 13.573 ± 0.020 12.630 ± 0.022 12.143 ± 0.029 
J02301551+2704061 02 30 15.51 27 04 06.18 198.10 ± 15.38 −13.50 ± 13.63 14.294 ± 0.024 13.478 ± 0.028 12.986 ± 0.021 
J02354756−0849198 02 35 47.57 −08 49 19.80 −12.28 ± 16.75 21.33 ± 16.51 15.571 ± 0.054 14.812 ± 0.055 14.191 ± 0.066 
J02361794+0048548 02 36 17.94 00 48 54.82 161.33 ± 10.10 −176.33 ± 19.16 16.098 ± 0.076 15.265 ± 0.066 14.666 ± 0.090 
J02394245−1735471 02 39 42.46 −17 35 47.20 61.09 ± 13.80 −79.12 ± 18.79 14.291 ± 0.029 13.525 ± 0.034 13.039 ± 0.030 
J02411151−0326587 02 41 11.52 −03 26 58.78 93.43 ± 17.00 −19.87 ± 13.40 15.799 ± 0.064 14.811 ± 0.053 14.035 ± 0.049 
J02424355+1607392 02 42 43.55 16 07 39.27 163.62 ± 14.16 −198.32 ± 12.77 15.776 ± 0.052 14.998 ± 0.053 14.349 ± 0.057 
J02560189+0110467 02 56 01.89 01 10 46.71 66.48 ± 22.28 −62.38 ± 22.06 16.212 ± 0.102 15.696 ± 0.184 15.216 ± 0.175 
J03090888−1949387 03 09 08.89 −19 49 38.76 218.00 ± 11.57 −13.33 ± 11.90 15.752 ± 0.055 14.656 ± 0.062 14.057 ± 0.065 
J03101401−2756452 03 10 14.01 −27 56 45.27 −118.89 ± 17.61 −46.70 ± 16.21 15.795 ± 0.070 14.662 ± 0.049 13.959 ± 0.060 
J03105986+1648155 03 11 00.02 16 48 15.68 262.83 ± 19.28 9.38 ± 17.90 16.025 ± 0.083 14.932 ± 0.070 14.312 ± 0.067 
J03140344+1603056 03 14 03.45 16 03 05.63 −244.73 ± 13.31 −49.07 ± 13.91 12.526 ± 0.021 11.823 ± 0.035 11.238 ± 0.019 
J03164512−2848521 03 16 45.13 −28 48 52.17 105.25 ± 22.15 −80.97 ± 2 12.88 14.578 ± 0.039 13.772 ± 0.035 13.114 ± 0.035 
J03202839−0446358 03 20 28.24 −04 46 40.59 −249.91 ± 17.00 −501.77 ± 12.26 13.259 ± 0.021 12.535 ± 0.022 12.134 ± 0.024 
J03264225−2102057 03 26 42.26 −21 02 05.77 103.12 ± 16.14 −129.87 ± 18.72 16.134 ± 0.093 14.793 ± 0.075 13.922 ± 0.065 
J03281738+0032572 03 28 17.49 00 32 57.57 201.84 ± 22.19 35.50 ± 17.21 15.988 ± 0.091 14.975 ± 0.074 14.161 ± 0.077 
J03301774+0000477 03 30 17.74 00 00 47.44 −8.29 ± 11.88 −33.00 ± 11.08 16.520 ± 0.111 15.881 ± 0.130 15.525 ± 0.182 
J03504861−0518126 03 50 48.61 −05 18 12.70 19.91 ± 11.31 −8.04 ± 15.59 16.327 ± 0.092 15.525 ± 0.094 15.125 ± 0.134 
J03552337+1133437 03 55 23.37 11 33 43.71 223.16 ± 22.90 −607.16 ± 22.07 14.050 ± 0.020 12.530 ± 0.029 11.526 ± 0.019 
J03554191+2257016 03 55 41.91 22 57 01.68 171.90 ± 13.14 −21.38 ± 10.33 16.111 ± 0.077 15.052 ± 0.068 14.284 ± 0.060 
J03572110−0641260 03 57 21.10 −06 41 26.04 133.59 ± 22.58 27.12 ± 5 25.51 15.953 ± 0.081 15.060 ± 0.085 14.599 ± 0.089 
J04070885+1514565 04 07 08.85 15 14 56.60 97.97 ± 16.28 −74.65 ± 17.40 16.055 ± 0.091 16.017 ± 0.208 15.922 ± 0.261 
J04082905−1450334 04 08 29.18 −14 50 34.33 193.43 ± 11.35 −99.07 ± 17.75 14.222 ± 0.028 13.337 ± 0.029 12.817 ± 0.021 
J04090950+2104393 04 09 09.51 21 04 39.38 101.13 ± 15.14 −148.46 ± 12.25 15.508 ± 0.053 14.497 ± 0.045 13.850 ± 0.046 
J04132039−0114248 04 13 20.39 −01 14 24.86 61.22 ± 15.29 0.08 ± 18.67 15.303 ± 0.047 14.657 ± 0.033 14.135 ± 0.059 
J04285096−2253227 04 28 51.05 −22 53 21.0 123.44 ± 16.02 183.48 ± 15.70 13.507 ± 0.020 12.668 ± 0.026 12.118 ± 0.024 
J04390101−2353083 04 39 00.93 −23 53 09.51 −119.29 ± 22.66 −127.25 ± 15.05 14.408 ± 0.026 13.409 ± 0.027 12.816 ± 0.021 
J04532647−1751543 04 53 26.51 −17 51 54.35 50.80 ± 14.38 −4.14 ± 14.30 15.142 ± 0.033 14.060 ± 0.034 13.466 ± 0.034 
J05012406−0010452 05 01 24.19 00 10 46.58 192.82 ± 11.98 −139.86 ± 12.29 14.982 ± 0.036 13.713 ± 0.033 12.963 ± 0.034 
J05021345+1442367 05 02 13.45 14 42 36.78 71.55 ± 13.68 −1.04 ± 18.53 14.271 ± 0.022 13.392 ± 0.019 12.955 ± 0.028 
J05120636−2949540 05 12 06.36 −29 49 53.12 −6.40 ± 13.41 96.87 ± 12.28 15.463 ± 0.055 14.156 ± 0.047 13.285 ± 0.041 
J05184616−2756457 05 18 46.19 −27 56 45.69 37.27 ± 17.01 10.72 ± 19.72 15.262 ± 0.041 14.295 ± 0.045 13.615 ± 0.039 
J05233822−1403022 05 23 38.22 −14 03 02.29 109.87 ± 17.14 178.88 ± 21.12 13.084 ± 0.021 12.220 ± 0.020 11.638 ± 0.025 
J06050196−2342270 06 05 01.96 −23 42 27.01 −66.48 ± 15.90 117.68 ± 18.21 14.512 ± 0.032 13.727 ± 0.035 13.145 ± 0.030 
J06262121+0029341 06 26 21.21 00 29 34.14 47.15 ± 12.94 1.03 ± 12.78 15.925 ± 0.093 15.209 ± 0.120 14.860 ± 0.123 
J06523073+4710348 06 52 30.74 47 10 34.83 −129.78 ± 14.67 149.52 ± 7 12.78 13.511 ± 0.020 12.384 ± 0.023 11.694 ± 0.018 
J07171626+5705430 07 17 16.27 57 05 43.05 −17.99 ± 17.87 67.17 ± 15.13 14.636 ± 0.029 13.593 ± 0.028 12.945 ± 0.025 
J07231462+5727081 07 23 14.62 57 27 08.17 61.39 ± 22.71 −219.85 ± 12.31 13.970 ± 0.024 13.156 ± 0.028 12.613 ± 0.029 
J07400966+3212032 07 40 09.67 32 12 03.24 −31.98 ± 11.79 −80.79 ± 13.45 16.191 ± 0.090 14.862 ± 0.059 14.222 ± 0.059 
J07414920+2351275 07 41 49.21 23 51 27.51 −250.22 ± 12.18 −116.21 ± 13.32 16.158 ± 0.100 15.838 ± 0.185 15.847 ± 99.99 
J07420130+2055198 07 42 01.30 20 55 19.88 −318.67 ± 12.08 −229.57 ± 13.15 16.193 ± 0.090 15.911 ± 0.181 15.225 ± 99.99 
J07475631+3947329 07 47 56.31 39 47 32.92 55.04 ± 14.43 −41.72 ± 13.26 15.076 ± 0.039 14.163 ± 0.038 13.724 ± 0.044 
J07525942+4136344 07 52 59.43 41 36 34.49 0.00 ± 13.39 43.98 ± 10.46 16.356 ± 0.130 15.601 ± 0.160 15.191 ± 99.99 
J07533217+2917119 07 53 32.17 29 17 11.93 −88.43 ± 11.08 −85.34 ± 13.12 15.516 ± 0.046 14.527 ± 0.039 13.849 ± 0.042 
J07554795+2212169 07 55 47.95 22 12 16.94 −9.87 ± 14.88 −226.48 ± 17.78 15.728 ± 0.063 15.669 ± 0.144 15.753 ± 0.207 
J07584037+3247245 07 58 40.37 32 47 24.55 −204.23 ± 18.01 −316.21 ± 12.42 14.947 ± 0.043 14.111 ± 0.041 13.879 ± 0.056 
J08014056+4628498 08 01 40.56 46 28 49.84 −194.73 ± 23.54 −331.056 ± 19.10 16.275 ± 0.133 15.452 ± 0.142 14.536 ± 0.100 
J08053189+4812330 08 05 31.89 48 12 33.10 −455.48 ± 14.62 61.35 ± 16.32 14.734 ± 0.034 13.917 ± 0.040 13.444 ± 0.040 
J08155674+4524119 08 15 56.75 45 24 11.93 −31.49 ± 15.56 −42.96 ± 13.18 16.057 ± 0.078 15.233 ± 0.093 14.812 ± 0.097 
J08202996+4500315 08 20 29.96 45 00 31.52 −104.16 ± 25.82 −299.16 ± 14.76 16.279 ± 0.107 15.000 ± 0.086 14.218 ± 0.065 
J08234818+2428577 08 23 48.18 24 28 57.71 −160.30 ± 19.81 73.19 ± 19.17 14.986 ± 0.042 14.060 ± 0.044 13.377 ± 0.029 
J08290664+1456225 08 29 06.64 14 56 22.56 −49.41 ± 16.67 −227.11 ± 18.47 14.750 ± 0.028 13.801 ± 0.035 13.166 ± 0.031 
J08304878+0128311 08 30 48.78 01 28 31.15 222.11 ± 15.89 −310.54 ± 15.36 16.289 ± 0.111 16.140 ± 0.213 16.358 ± 99.99 
J08320451−0128360 08 32 04.52 −01 28 36.05 63.83 ± 13.19 26.73 ± 15.10 14.128 ± 0.028 13.318 ± 0.022 12.712 ± 0.026 
J08355829+0548308 08 35 58.30 05 48 30.85 −109.70 ± 12.79 −15.00 ± 15.54 14.533 ± 0.034 13.683 ± 0.036 13.168 ± 0.033 
J08472872−1532372 08 47 28.73 −15 32 37.21 149.07 ± 16.12 −177.78 ± 15.82 13.513 ± 0.023 12.629 ± 0.026 12.061 ± 0.021 
J08523490+4720359 08 52 34.91 47 20 35.91 −28.69 ± 18.13 −386.53 ± 13.88 16.182 ± 0.108 15.419 ± 0.146 14.718 ± 0.116 
J08564793+2235182 08 56 47.94 22 35 18.21 −184.24 ± 19.74 3.01 ± 20.71 15.679 ± 0.064 14.580 ± 0.052 13.951 ± 0.046 
J08575849+5708514 08 57 58.49 57 08 51.42 −413.61 ± 20.52 −353.43 ± 16.85 15.038 ± 0.038 13.790 ± 0.041 12.962 ± 0.028 
J08592547−1949268 08 59 25.48 −19 49 26.89 −310.77 ± 13.51 −78.59 ± 15.95 15.527 ± 0.052 14.436 ± 0.041 13.751 ± 0.057 
J09095749−0658186 09 09 57.49 −06 58 18.64 −174.53 ± 14.89 39.70 ± 16.48 13.890 ± 0.021 13.090 ± 0.020 12.539 ± 0.024 
J09153413+0422045 09 15 34.14 04 22 04.59 −88.46 ± 18.02 40.27 ± 20.60 14.548 ± 0.028 13.531 ± 0.031 13.011 ± 0.041 
J09183815+2134058 09 18 38.16 21 34 05.82 353.41 ± 14.50 −454.02 ± 15.66 15.662 ± 0.060 14.580 ± 99.99 13.903 ± 0.042 
J09201223+3517429 09 20 12.23 35 17 42.97 −172.34 ± 13.35 −185.26 ± 12.72 15.625 ± 0.062 14.673 ± 0.056 13.979 ± 0.061 
J09211410−2104446 09 21 14.11 −21 04 44.60 260.71 ± 15.59 −900.91 ± 13.20 12.779 ± 0.021 12.152 ± 0.020 11.690 ± 0.021 
J09283972−1603128 09 28 39.72 −16 03 12.86 −132.85 ± 15.59 36.00 ± 13.20 15.322 ± 0.041 14.292 ± 0.036 13.615 ± 0.050 
J09352803−2934596 09 35 28.04 −29 34 59.62 8.84 ± 18.10 86.92 ± 14.61 14.036 ± 0.026 13.312 ± 0.027 12.822 ± 0.026 
J10185879−2909535 10 18 58.79 −29 09 53.56 −323.01 ± 21.04 −82.84 ± 15.20 14.213 ± 0.028 13.418 ± 0.022 12.796 ± 0.021 
J10432508+0001482 10 43 25.00 00 01 46.92 −159.31 ± 15.56 −143.85 ± 21.27 15.935 ± 0.080 15.208 ± 0.072 14.472 ± 0.100 
J12285538+0050440 12 28 55.37 00 50 43.94 -32.33 ± 3.54 −12.41 ± 2.06 15.613 ± 0.060 14.825 ± 0.059 14.162 ± 0.077 
J16360078−0034525 16 36 00.59 00 34 54.36 −344.71 ± 14.13 −200.89 ± 14.86 14.590 ± 0.043 13.904 ± 0.042 13.415 ± 0.035 
J17434148+2127069 17 43 41.59 21 27 09.16 165.91 ± 14.890 248.68 ± 14.47 15.830 ± 0.088 14.785 ± 0.064 14.321 ± 0.097 

The images were reduced at the Cambridge Astronomical Survey Unit (CASU) using procedures which have been custom written for the treatment of WFCAM data (Dye et al. 2006; Irwin et al., in preparation). In brief, each frame was debiased, dark corrected and then flat-fielded. The individual dithered images were stacked before having an object detection routine run on them. The frames were astrometrically calibrated using point sources in the 2MASS catalogue. The accuracy is typically ≈0.1 arcsec (Dye et al. 2006). The photometric calibration employed by the Cambridge Astronomical Survey Unit (CASU) pipeline also relies on 2MASS data (there are typically hundreds of 2MASS calibrators per detector) and is found to be accurate to ≈2 per cent in good conditions (Warren et al. 2007). However, as we wished to measure proper motions, the astrometric calibration was more important than the photometric calibration for these data.

The objects with Dec. less than −30° were observed using SofI on the NTT. SofI is a wide field infrared imager consisting of a Hawaii HgCdTe 1024 × 1024 array. This has a plate scale of 0.292 arcsec pixel−1 and a field of view of ∼5 arcmin (Moorwood, Cuby & Lidman 1998). The images were taken between 2007 April 2 and 2007 August 31 in the J band. The conditions were non-photometric, exposure times were between 5 and 10 min and a nine-point dither pattern was used. As for the WFCAM images, S/N ≈ 100 was achieved in the conditions.

These data were reduced using the orac-dr pipeline (Allan et al. 2002). This pipeline is maintained and developed by the Joint Astronomy Centre (JAC) in Hawaii, and has been adapted to reduce SofI data (Currie 2003). The pipeline bias corrected, flat-fielded, sky subtracted and created mosaics out of the nine images per object. These mosaics were then astrometrically calibrated using point sources in 2MASS, and the starlink autoastrom package. The accuracy of this calibration is typically greater than 0.1 arcsec, as measured by the rms of the fit to the 2MASS point sources. This is worse than the WFCAM astrometry as one might expect, as there are much fewer reference stars in the smaller SofI images. Object detection was completed using SExtractor using the image parameters (gain etc.) and a suitably sized background mesh, tailored to the seeing and pixel scale of the image.

2.2 Calculating proper motions

The astrometry for 2MASS is good to 80 mas over the whole survey, and to 50 mas over a small area (Skrutskie et al. 2006). Because the WFCAM and SofI astrometry is also calibrated to the 2MASS catalogue, accurate relative proper motion measurements could be calculated simply by taking the difference in 2MASS and WFCAM positions and dividing by the epoch difference. We calculated the epoch difference by taking the difference in the Julian date as given in the fits header for each image, which is between 6.5 and 8.7 yr with the average epoch difference being 7.8 yr for SofI and between 5.8 and 9.5 yr with an average of 8.5 yr for WFCAM. The proper motion measurements for each object in every WFCAM array 3 and SofI image were calculated by this method. This same method was used for our previous 143 objects (Jameson et al. 2008a) and produced results consistent with the existing data.

This motion was then converted into mas yr−1. The proper motion has been calculated directly from the right ascension (RA) and Dec. of the object in question, not from pixel motion on images, hence μα= (Δα/ΔT) cos δ arcsec yr−1 if Δα is converted to arcseconds. These proper motions are relative proper motions, in the sense that they are relative to the bulk of the background stars in the field, which are generally moving slowly enough to be assumed to have zero motion.

However, for the WFCAM fields we checked the reference star motion so that the proper motion of the brown dwarf could be altered if there was a standard offset in the field.

The proper motions were separated in μα cos δ and μδ from −500 to 500 mas yr−1 in each direction, in bins of size 20 mas yr−1, and the number of objects falling into each bin were totalled. We then fitted a two-dimensional Gaussian to the data for each field to determine the spread of the reference stars, as well as the true centre of the motion. The process was then repeated after the initial fit, rejecting any objects that lay outside 3σ of the fitted Gaussian, before fitting another Gaussian to this data. This fitting was important in some cases as the reference stars had quite a large spread, and in other cases the proper motion of our brown dwarf was of the same order of magnitude as the references. These centroiding changes, or the centres of the fit, were then subtracted from the calculated proper motion measurements.

We used the σ value of the Gaussian to determine the error on our measurements. In general the errors were of the order of ≈15 mas yr−1. The quoted errors are the σ value of the Gaussian fitted to the proper motion points for each image. Strictly this should be the σ plus the position error of the object added in quadrature. However, the centroiding errors for WFCAM are less than 2 mas yr−1, and so are small compared to the σ value.

This method could not be used for some of the SofI fields, as there were less than 30 reference stars present, and in some cases, as few as six. For these fields, the Gaussian fitting did not converge. As an alternative method of gauging the offset in motion and the proper motion errors, the mean of both μα cos δ and μδ was calculated for all of the objects in the field, once the brown dwarf had been removed. The standard deviation was also calculated, and again an iterative process used to remove any objects that lay further from the mean than 3 standard deviations. The process was then repeated and the means were then used as the offset in motion and the standard error of the mean values was then used as the error of the proper motion. The measured proper motions are given in Table 1 for the brown dwarfs imaged by SofI and in Table 2 for the brown dwarfs imaged by WFCAM.

Some of the L dwarfs have had their proper motions measured by other people namely Caballero (2007) and Schmidt et al. (2007). The proper motions given by Caballero (2007) are taken from the SuperCOSMOS Sky Survey. The errors on the proper motions are typically 10 mas yr−1, although in some cases this is larger, such as in the case of J0847−15 and J0909−07. This is because the SuperCOSMOS Sky Survey which consists of scanned sky atlas photographic plates, imaged in at least two epochs (Hambly et al. 2001a,b), has necessarily measured the proper motions over an unfavourable (i.e. short) epoch difference (using the minimum of two plates required to calculate the motions). Both of these objects have Schmidt et al. (2007) proper motions that do agree with our values, and so the Caballero (2007) measurements are taken to be inaccurate. Tables 3 and 4 show the proper motion comparisons as given by Caballero (2007) and Schmidt et al. (2007).

Table 3

Name, μ from Schmidt et al. (2007), θ from Schmidt et al. (2007), μ, θ for all the L and T dwarfs common with Schmidt et al. (2007).

Name 2MASS μ (Schmidt) (arcsec yr−1θ (Schmidt) (°) μ (arcsec yr−1θ (°) 
J0213+44 0.17 ± 0.06 195 ± 21 0.138 ± 0.01 197 ± 6 
J0255−47 1.23 ± 0.11 120 ± 5 1.18 ± 0.01 117 ± 1 
J0314+16 0.25 ± 0.07 254 ± 13 0.25 ± 0.01 256 ± 3 
J0355+11 0.70 ± 0.05 159 ± 3 0.64 ± 0.02 160 ± 2 
J0439−23 0.20 ± 0.17 220 ± 37 0.17 ± 0.02 223 ± 6 
J0445−30 0.38 ± 0.11 161 ± 23 0.43 ± 0.01 160 ± 1 
J0523−14 0.08 ± 0.16 21 ± 105 0.2 ± 0.02 32 ± 5 
J0624−45 0.28 ± 0.19 19 ± 52 0.39 ± 0.01 352 ± 5 
J0651+47 0.14 ± 0.05 336 ± 13 0.19 ± 0.013 319 ± 4 
J0847−15 0.27 ± 0.05 146 ± 10 0.23 ± 0.015 140 ± 4 
J0915+04 0.14 ± 0.15 284 ± 84 0.097 ± 0.018 294 ± 11 
J0921−21 0.98 ± 0.15 163 ± 10 0.93 ± 0.113 164 ± 1 
J1425−36 0.53 ± 0.10 204 ± 7 0.52 ± 0.03 209 ± 3 
J1753−65 0.36 ± 0.09 178 ± 24 0.33 ± 0.04 189 ± 13 
Name 2MASS μ (Schmidt) (arcsec yr−1θ (Schmidt) (°) μ (arcsec yr−1θ (°) 
J0213+44 0.17 ± 0.06 195 ± 21 0.138 ± 0.01 197 ± 6 
J0255−47 1.23 ± 0.11 120 ± 5 1.18 ± 0.01 117 ± 1 
J0314+16 0.25 ± 0.07 254 ± 13 0.25 ± 0.01 256 ± 3 
J0355+11 0.70 ± 0.05 159 ± 3 0.64 ± 0.02 160 ± 2 
J0439−23 0.20 ± 0.17 220 ± 37 0.17 ± 0.02 223 ± 6 
J0445−30 0.38 ± 0.11 161 ± 23 0.43 ± 0.01 160 ± 1 
J0523−14 0.08 ± 0.16 21 ± 105 0.2 ± 0.02 32 ± 5 
J0624−45 0.28 ± 0.19 19 ± 52 0.39 ± 0.01 352 ± 5 
J0651+47 0.14 ± 0.05 336 ± 13 0.19 ± 0.013 319 ± 4 
J0847−15 0.27 ± 0.05 146 ± 10 0.23 ± 0.015 140 ± 4 
J0915+04 0.14 ± 0.15 284 ± 84 0.097 ± 0.018 294 ± 11 
J0921−21 0.98 ± 0.15 163 ± 10 0.93 ± 0.113 164 ± 1 
J1425−36 0.53 ± 0.10 204 ± 7 0.52 ± 0.03 209 ± 3 
J1753−65 0.36 ± 0.09 178 ± 24 0.33 ± 0.04 189 ± 13 
Table 4

Name, μ from Caballero (2007), θ from Caballero (2007), μ, θ for all the L and T dwarfs common with Caballero (2007).

Name 2MASS μα cos δ (Caballero)  μδ(Caballero)  μα cos δ μδ 
(mas yr−1
J0255−47 1060 ± 50 −630 ± 50 1052.88 ± 11.17 −546.54 ± 6.17 
J0445−30 167 ± 12 −424 ± 12 158.07 ± 9.33 −402.39 ± 5.36 
J0451−34 94 ± 17 114 ± 16 76.34 ±−8.05 166.66 ±−8.01 
J0719−50 140 ± 30 −10 ± 30 199.11 ± 20.49 −46.44 ± 13.78 
J0847−15 −130 ± 160 −20 ± 180 149.07 ± 16.12 −177.78 ± 15.82 
J0909−07 −280 ± 190 110 ± 180 −174.53 ± 14.89 39.70 ± 16.48 
J0921−21 100 ± 60 −900 ± 60 260.71 ± 15.59 −900.91 ± 13.20 
Name 2MASS μα cos δ (Caballero)  μδ(Caballero)  μα cos δ μδ 
(mas yr−1
J0255−47 1060 ± 50 −630 ± 50 1052.88 ± 11.17 −546.54 ± 6.17 
J0445−30 167 ± 12 −424 ± 12 158.07 ± 9.33 −402.39 ± 5.36 
J0451−34 94 ± 17 114 ± 16 76.34 ±−8.05 166.66 ±−8.01 
J0719−50 140 ± 30 −10 ± 30 199.11 ± 20.49 −46.44 ± 13.78 
J0847−15 −130 ± 160 −20 ± 180 149.07 ± 16.12 −177.78 ± 15.82 
J0909−07 −280 ± 190 110 ± 180 −174.53 ± 14.89 39.70 ± 16.48 
J0921−21 100 ± 60 −900 ± 60 260.71 ± 15.59 −900.91 ± 13.20 

It should be pointed out that 0915+04 is described as a binary by Reid et al. (2006) with a separation of 0.73 arcsec at −155°. Our image also shows two resolved objects which may be why there is such a difference between the Schmidt et al. (2007) measurements and these data.

Further two objects have additional proper motion measurements. J0255−47 has a proper motion measurement of 1.14 ± 0.0022 arcsec yr−1 and a θ measurement of forumla (Costa et al. 2006). Our measurements are μ= 1.18 ± 0.01 arcsec yr−1 and forumla. This object also has an additional parallax measurement of ∼5 pc (Costa et al. 2006), placing it well within the local neighbourhood.

J0320−04 is suspected to be an unresolved M8.5+T5 binary (Burgasser et al. 2008) and has a proper motion of 0.562 ± 0.005, and a θ of 205.9, which compares favourably with our measurements of 0.65 ± 0.01 arcsec and forumla.

3 POSSIBLE BINARIES

This study also provides an opportunity to search for wide common proper motion companions to the known brown dwarfs. Any objects within the field that have a proper motion within 15 mas yr−1 of the dwarf's motion were considered as possible companions. Obviously any brown dwarf with a proper motion close to zero, or the majority of background sources, will have a large number of ‘companions’ within our selection. These objects have been excluded.

Two brown dwarfs J100−33 and J0147+34 appear to have common proper motion companions.

J1004−33 has a possible M dwarf companion which SIMBAD names as LHS 5166, a high proper motion star with proper motion of μα cos δ= 400 mas yr−1 and μδ=−420 mas yr−1. Our measurement of its proper motion is 370.66 ± 25.14, −342.62 ± 14.46 mas yr−1.

J0147 + 34 has a companion which is an M dwarf as identified by Wei et al. (1999). This M dwarf is an X-ray source (2E 0144.7+ 3438 as given by SIMBAD), suggesting that it may be young. It is 43 arcsec away from the known brown dwarf and has a proper motion of 46.2 ± 18.3, −46.4 ± 14.8 mas yr−1.

Further proper motion and radial velocity measurements are required before these can be confirmed as true companions however.

4 FAST MOVING OBJECTS

In Paper I (Jameson et al. 2008a), we discovered eight high-velocity L dwarfs which we suggested may belong to the thick disk or halo population. Applying the same criteria to these data (that the proper motion must be greater than 0.85 arcsec yr−1), we found three candidates from the SofI images. The distance estimate derived from their spectral type as defined in Cruz et al. (2003) is 22.35 pc for J0014−48 (L2), 5.0 pc for J0255−47 (L8) and 25.8 pc for J2150−75 (L1). J0255−47, also has a parallax measurement from Costa et al. (2006), which is 4.96 pc, in agreement with the spectral type distance. This object is relatively nearby, which gives it a true velocity of only 28 km s−1. The other two objects have velocities of 95 and 112 km s−1, respectively. Both J0014−48 and J2150−75 have relatively blue JKS and HKS colours for their spectral types, as with other high-velocity dwarfs (Schmidt et al. 2007; Jameson et al. 2008a), indicating that they too may be members of an older (∼10 Gyr) thick disc population.

From the WFCAM data, just one object met the required selection criteria, J0921−21, an L2 dwarf, with a spectral type distance of 12.4 pc, and a velocity of 55 km s−1. This velocity is not high enough for this object to be considered a true high-velocity dwarf.

5 MOVING GROUPS

We have attempted to determine if any of these brown dwarfs are members of known moving groups. Being a moving group member means that an age can be estimated for the dwarf. This does not necessarily mean that the moving group member is an ‘escaped’ cluster member however, as galactic resonances can produce a similar effect (Dehnen 1998). To determine if any of these field dwarfs are moving group members, we used the moving cluster method as described in Bannister & Jameson (2007) and Jameson et al. (2008a). Again, we used the proper motion measurements and direction of that motion as well as a distance derived from the spectral type as described in Cruz et al. (2003). If the difference in angles between the measured and predicted motion towards the convergent point is less than 14° plus the error on the measurement, and the ratio between the moving cluster distance and the Cruz spectral type distance was greater than 0.72 and less than 1.28 as in Bannister & Jameson (2007) and Jameson et al. (2008a), then the selected objects were plotted on a colour–magnitude diagram, and compared to the DUSTY and NextGen models (Baraffe et al. 1998; Chabrier et al. 2000) and to empirical isochrones defined by known cluster members (Casewell et al. 2007 for the Pleiades and Hogan et al. 2008 for the Hyades).

5.1 Hyades

The Hyades cluster has a distance of 46 pc and covers ≈20° of the sky. The Hyades has, until recently, been thought to contain almost no low-mass members. Extensive searches such as those of Gizis, Reid & Monet (1999) and Dobbie et al. (2002) turned up no brown dwarf members. It was hypothesized that being an older open star cluster (625 Myr; Perryman et al. 1998) any low-mass members would have evaporated from the cluster through dynamical evolutionary processes. For a cluster of this age ∼70 per cent of stars and ∼85 per cent of brown dwarfs are expected to have escaped the cluster (Adams et al. 2002).

Recently however, studies using deep, wide field surveys such as the UKIDSS (Hogan et al. 2008) have unearthed 12 L dwarf candidate members. Bouvier et al. (2008) have also claimed two T dwarf members from a 16 deg2 survey of the cluster's centre.

Chereul, Creze & Bienayme (1998) first identified escaped Hyads, and more recently Bannister & Jameson (2007) have identified seven L and T field dwarfs that belong to the Hyades moving group. Zapatero Osorio et al. (2007) have confirmed that one of these objects (2MASS J1217110−031113) has a radial velocity consistent with being an escaped member of the Hyades cluster, while two (2MASS J0205293−115930 and 2MASS J16241436+ 0029158) have radial velocities that are only consistent with being moving group members.

In Paper I (Jameson et al. 2008a), we reported the discovery of 15 new moving group candidate members. The Hyades moving group has its convergent point situated at forumla, and the members have a space velocity of 46 km s−1 (Madsen, Dravins & Lindgren 2002).

After using the moving group method, the Cruz et al. (2003) distance and the convergent point from Madsen et al. (2002), we have found seven new candidate members of the Hyades moving group (Table 5). These objects are plotted in Fig. 1 as well as the Bannister & Jameson (2007), Hogan et al. (2008) and Jameson et al. (2008a) dwarfs.

Table 5

Name, spectral type, J, H, K magnitudes, Δθ, dmg/dsp and dsp for the potential Hyades moving group members discussed. Where two spectral types have been given, they are in the order of optical spectral type, infrared spectral type.

Name Spt J H K Δθ (°) dsp (pc) dmg/dsp (pc) 
J0131+38 L4 14.68 ± 0.03 13.70 ± 0.03 13.05 ± 0.03 12.18 ± 1.93 93.15 1.19 
J0141+18 L1/L4 13.88 ± 0.03 13.03 ± 0.02 12.49 ± 0.03 12.65 ± 2.21 94.33 0.96 
J0205+12 L5 15.68 ± 0.06 14.45 ± 0.05 13.67 ± 0.04 9.19 ± 1.79 91.28 0.93 
J02081+25 L1 13.99 ± 0.03 13.11 ± 0.03 12.59 ± 0.03 12.19 ± 2.47 93.72 1.01 
J0357−06 L0 15.95 ± 0.08 15.06 ± 0.09 14.60 ± 0.09 5.01 ± 10.67 78.52 1.02 
J0624−45 L5 14.48 ± 0.03 13.34 ± 0.03 12.60 ± 0.02 8.69 ± 5.41 15.41 1.27 
J1928−43 L5 15.20 ± 0.04 14.13 ± 0.04 13.46 ± 0.04 6.70 ± 3.74 21.46 1.04 
Name Spt J H K Δθ (°) dsp (pc) dmg/dsp (pc) 
J0131+38 L4 14.68 ± 0.03 13.70 ± 0.03 13.05 ± 0.03 12.18 ± 1.93 93.15 1.19 
J0141+18 L1/L4 13.88 ± 0.03 13.03 ± 0.02 12.49 ± 0.03 12.65 ± 2.21 94.33 0.96 
J0205+12 L5 15.68 ± 0.06 14.45 ± 0.05 13.67 ± 0.04 9.19 ± 1.79 91.28 0.93 
J02081+25 L1 13.99 ± 0.03 13.11 ± 0.03 12.59 ± 0.03 12.19 ± 2.47 93.72 1.01 
J0357−06 L0 15.95 ± 0.08 15.06 ± 0.09 14.60 ± 0.09 5.01 ± 10.67 78.52 1.02 
J0624−45 L5 14.48 ± 0.03 13.34 ± 0.03 12.60 ± 0.02 8.69 ± 5.41 15.41 1.27 
J1928−43 L5 15.20 ± 0.04 14.13 ± 0.04 13.46 ± 0.04 6.70 ± 3.74 21.46 1.04 
Figure 1

MK, JK colour–magnitude diagram for the Hyades moving group. The cluster members identified by Hogan et al. (2008) are plotted as filled squares. All of the objects that were previously selected as moving group members are marked as filled diamonds (Bannister & Jameson 2007; Jameson et al. 2008a). The selected members are marked by a box for objects from the SofI data and by circles for the WFCAM objects. The errors are Poissonion and from the photometry only. The solid and dashed lines represent the single star (solid line) and binary (dotted line) cluster sequences as shown in Hogan et al. (2008).

Figure 1

MK, JK colour–magnitude diagram for the Hyades moving group. The cluster members identified by Hogan et al. (2008) are plotted as filled squares. All of the objects that were previously selected as moving group members are marked as filled diamonds (Bannister & Jameson 2007; Jameson et al. 2008a). The selected members are marked by a box for objects from the SofI data and by circles for the WFCAM objects. The errors are Poissonion and from the photometry only. The solid and dashed lines represent the single star (solid line) and binary (dotted line) cluster sequences as shown in Hogan et al. (2008).

5.2 Ursa Major

The Ursa Major moving group has been estimated to have an age of between 300 Myr (Soderblom & Mayor 1993) and 500 ± 100 Myr (King et al. 2003). Castellani et al. (2002) found an age of the group to be 400 Myr. The age of 400 ± 100 Myr is adopted in this work. The convergent point of the Ursa Major moving group is located at forumla (J2000; Madsen et al. 2002). The selected objects are shown in Fig. 2 and their data in Table 6.

Figure 2

MK, JK colour–magnitude diagram for the Ursa Major moving group. The cluster members identified by Bannister & Jameson (2007) and Jameson et al. (2008a) are marked by filled diamonds. The selected members are marked by a box for objects from the SofI data and by filled circles for the WFCAM objects. The errors are Poissonion and from the photometry only. The solid line indicates a possible single star sequence from Bannister & Jameson (2007). The straight line fit to the new L dwarf sequence is shown by a dotted line, and the dashed line represents what we believe to be the turnaround of the sequence.

Figure 2

MK, JK colour–magnitude diagram for the Ursa Major moving group. The cluster members identified by Bannister & Jameson (2007) and Jameson et al. (2008a) are marked by filled diamonds. The selected members are marked by a box for objects from the SofI data and by filled circles for the WFCAM objects. The errors are Poissonion and from the photometry only. The solid line indicates a possible single star sequence from Bannister & Jameson (2007). The straight line fit to the new L dwarf sequence is shown by a dotted line, and the dashed line represents what we believe to be the turnaround of the sequence.

Table 6

Name, spectral type, J, H, K magnitudes, Δθ, dmg/dsp and dsp for the potential Ursa Major moving group members discussed. Where two spectral types have been given, they are in the order of optical spectral type, infrared spectral type. J0920+35 is a binary (Reid et al. 2001), discovered using Hubble Space Telescope (HST). Is suspected to be an equal mass binary.

Name Spt J H K Δθ (°) dsp (pc) dmg/dsp (pc) 
J0218−31 L3 14.73 ± 0.04 13.81 ± 0.04 13.15 ± 0.03 6.29 ± 5.14 25.85 0.86 
J0310−27 L5 15.80 ± 0.07 14.66 ± 0.05 13.96 ± 0.06 1.48 ± 7.36 28.24 0.80 
J0815+45 L1 16.06 ± 0.08 15.23 ± 0.09 14.81 ± 0.10 12.04 ± 15.89 64.88 1.09 
J0920+35 L6.5/T0 15.63 ± 0.06 14.67 ± 0.06 13.98 ± 0.06 5.30 ± 2.96 19.06 0.79 
Name Spt J H K Δθ (°) dsp (pc) dmg/dsp (pc) 
J0218−31 L3 14.73 ± 0.04 13.81 ± 0.04 13.15 ± 0.03 6.29 ± 5.14 25.85 0.86 
J0310−27 L5 15.80 ± 0.07 14.66 ± 0.05 13.96 ± 0.06 1.48 ± 7.36 28.24 0.80 
J0815+45 L1 16.06 ± 0.08 15.23 ± 0.09 14.81 ± 0.10 12.04 ± 15.89 64.88 1.09 
J0920+35 L6.5/T0 15.63 ± 0.06 14.67 ± 0.06 13.98 ± 0.06 5.30 ± 2.96 19.06 0.79 

In Jameson et al. (2008b) we defined a relationship between MK and JK for the L dwarf sequence in the Hyades and Ursa Major moving groups and the Pleiades, Upper Scorpius and Alpha Persei open star clusters. This allowed a photometric relationship for estimating the age of any field dwarf to be derived.

Using the new objects presented here and in Paper I (Jameson et al. 2008a) we are able to refine the relationship derived in Jameson et al. (2008b) for the Ursa Major moving group. Previously, this relationship [which takes the form JK=mMK+c, in the Mauna Kea Observatory (MKO) system] had a gradient (m) = 2.88 and c= 11.22. This was only based on the two brown dwarfs in the L dwarf sequence from Bannister & Jameson (2007), and was obviously incorrect. The sequence shown in fig. 2 of Jameson et al. (2008b) crossed that for the Hyades, and the gradient of 2.88, did not fit, with the gradients of the other clusters, which had approximately parallel sequences, all with gradients of ∼1.98, the value that was suggested by the authors as being more appropriate. Using our new L dwarfs, and those found by Jameson et al. (2008a), we used the colour conversions of Stephens & Leggett (2004) to recalculate the relationship on the MKO system. Our new values are m= 2.0746 ± 0.281, c= 7.92052 ± 0.4481, which is more in keeping with the values for the other clusters. The relationship in the 2MASS colour system is plotted in Fig. 2, as well as the sequence as defined by the Bannister & Jameson (2007) dwarfs.

5.3 Pleiades

The Pleiades cluster is 125-Myr old and is situated at a distance of 130 pc (Stauffer, Schultz & Kirkpatrick 1998). As a cluster it has been studied in depth and has been found to contain many brown dwarfs (Moraux et al. 2003; Bihain et al. 2006; Casewell et al. 2007; Lodieu et al. 2007a). The Pleiades moving group has a convergent point of forumla (Madsen et al. 2002). This convergent point is very close to that of many other moving groups such as Alpha Persei forumla; Madsen et al. 2002, 50 Myr; Lyngå 1987), Tucana/Horologium (30 Myr; Zuckerman & Song 2004) and the AB Dor moving group (50 Myr; Zuckerman & Song 2004; see Zuckerman & Song 2004, for a review), and it has been theorized that many of these moving groups have a common origin (Ortega et al. 2007). 13 new candidate members were found using the moving group method. Six objects with Dec. < −30° and seven objects with Dec. > −30° (Fig. 3, Table 7). As with the Hyades and Ursa Major clusters, the Pleiades is old enough to expect that some mass segregation has occurred, and thus it is not unreasonable to search the whole sky for members of the moving group. This is not the case, however, for many of the younger, southern moving groups.

Figure 3

MK, JK colour–magnitude diagram for the Pleiades moving group. The cluster members identified by Moraux et al. (2003), Bihain et al. (2006), Casewell et al. (2007) and Lodieu et al. (2007a) are plotted as filled squares. All of the objects that were selected as moving group members are marked as filled diamonds (Jameson et al. 2008a). The selected members are marked by a box for objects from the SofI data and by filled circles for the WFCAM objects. The errors are Poissonion and from the photometry only.

Figure 3

MK, JK colour–magnitude diagram for the Pleiades moving group. The cluster members identified by Moraux et al. (2003), Bihain et al. (2006), Casewell et al. (2007) and Lodieu et al. (2007a) are plotted as filled squares. All of the objects that were selected as moving group members are marked as filled diamonds (Jameson et al. 2008a). The selected members are marked by a box for objects from the SofI data and by filled circles for the WFCAM objects. The errors are Poissonion and from the photometry only.

Table 7

Name, spectral type, J, H, K magnitudes, Δθ, dmg/dsp and dsp for the potential Pleiades moving group members discussed. Where two spectral types have been given, they are in the order of optical spectral type, infrared spectral type.

Name Spt J H K Δθ (°) dsp (pc) dmg/dsp (pc) 
J0032−44 L0 14.78 ± 0.03 13.86 ± 0.03 13.27 ± 0.04 13.71 ± 2.51 40.70 0.86 
J0058−06 L0 14.31 ± 0.03 13.44 ± 0.03 12.90 ± 0.03 4.83 ± 5.19 32.85 0.99 
J0117−34 L2 15.18 ± 0.03 14.20 ± 0.04 13.49 ± 0.04 4.84 ± 4.28 37.58 1.18 
J0125−34 L2 15.52 ± 0.05 14.47 ± 0.05 13.90 ± 0.05 18.82 ± 10.14 44.03 0.90 
J0144−07 L5 14.20 ± 0.03 13.01 ± 0.03 12.27 ± 0.02 13.87 ± 2.28 13.49 1.02 
J0208+27 L5 15.71 ± 0.06 14.56 ± 0.06 13.87 ± 0.05 15.56 ± 3.60 27.21 0.903 
J0236+00 L6/L6.5 16.10 ± 0.08 15.27 ± 0.07 14.67 ± 0.09 8.13 ± 3.58 26.22 1.00 
J0316−28 L0 14.57 ± 0.04 13.77 ± 0.03 13.11 ± 0.03 4.55 ± 7.30 37.02 1.17 
J0357−44 L0 14.37 ± 0.03 13.53 ± 0.03 12.91 ± 0.03 4.12 ± 6.85 33.71 0.99 
J0409+21 L3 15.51 ± 0.05 14.50 ± 0.05 13.85 ± 0.05 16.18 ± 4.55 37.03 0.94 
J1425−36 L5 13.74 ± 0.03 12.57 ± 0.02 11.81 ± 0.03 6.23 ± 2.76 11.00 1.11 
J1928−43 L5 15.20 ± 0.04 14.13 ± 0.04 13.46 ± 0.04 3.80 ± 3.74 21.46 1.05 
J1936−55 L5 14.49 ± 0.04 13.63 ± 0.03 13.05 ± 0.03 15.30 ± 4.84 15.46 1.17 
Name Spt J H K Δθ (°) dsp (pc) dmg/dsp (pc) 
J0032−44 L0 14.78 ± 0.03 13.86 ± 0.03 13.27 ± 0.04 13.71 ± 2.51 40.70 0.86 
J0058−06 L0 14.31 ± 0.03 13.44 ± 0.03 12.90 ± 0.03 4.83 ± 5.19 32.85 0.99 
J0117−34 L2 15.18 ± 0.03 14.20 ± 0.04 13.49 ± 0.04 4.84 ± 4.28 37.58 1.18 
J0125−34 L2 15.52 ± 0.05 14.47 ± 0.05 13.90 ± 0.05 18.82 ± 10.14 44.03 0.90 
J0144−07 L5 14.20 ± 0.03 13.01 ± 0.03 12.27 ± 0.02 13.87 ± 2.28 13.49 1.02 
J0208+27 L5 15.71 ± 0.06 14.56 ± 0.06 13.87 ± 0.05 15.56 ± 3.60 27.21 0.903 
J0236+00 L6/L6.5 16.10 ± 0.08 15.27 ± 0.07 14.67 ± 0.09 8.13 ± 3.58 26.22 1.00 
J0316−28 L0 14.57 ± 0.04 13.77 ± 0.03 13.11 ± 0.03 4.55 ± 7.30 37.02 1.17 
J0357−44 L0 14.37 ± 0.03 13.53 ± 0.03 12.91 ± 0.03 4.12 ± 6.85 33.71 0.99 
J0409+21 L3 15.51 ± 0.05 14.50 ± 0.05 13.85 ± 0.05 16.18 ± 4.55 37.03 0.94 
J1425−36 L5 13.74 ± 0.03 12.57 ± 0.02 11.81 ± 0.03 6.23 ± 2.76 11.00 1.11 
J1928−43 L5 15.20 ± 0.04 14.13 ± 0.04 13.46 ± 0.04 3.80 ± 3.74 21.46 1.05 
J1936−55 L5 14.49 ± 0.04 13.63 ± 0.03 13.05 ± 0.03 15.30 ± 4.84 15.46 1.17 

The new moving group members are detailed in Table 7.

5.4 Other moving groups

Many of the southern moving groups have similar convergent points and velocities. To determine if any of our southern dwarfs are members of these moving groups, we have used the moving group method as for the Hyades, Ursa Major and Pleiades moving groups, but have then used the isochrone for Upper Scorpius as developed by Jameson et al. (2008b). This can be then used as an age indicator for the younger clusters. If the selected dwarfs fall on or near the isochrone, then they are young (age <10 Myr) and are considered candidate members. Radial velocity measurements are needed to confirm the membership of these objects however.

Simply by using the moving group method, we have found <10 candidate members of the TW Hydra, Tucana/Horlogium, Beta Pictoris, AB Doradus and η Chamaeleon moving groups. Because these clusters all have similar convergent points and velocities (Zuckerman & Song 2004) some of the candidate members are found in more than one cluster.

When plotted on the MK, JK colour–magnitude diagram, using Stephens & Leggett (2004) to convert the colours into the MKO system, with the Upper Scorpius and Alpha Perseus cluster isochrones from Jameson et al. (2008b), all of the candidate members sit lower then Alpha Per, indicating that these dwarfs cannot be moving group members at the calculated distances.

6 CONCLUSIONS

This paper continues the work presented in Jameson et al. (2008a), which presented proper motions of 143 L and T dwarfs. This paper presents a further 126 proper motions. Thus the large majority of field L and T dwarfs discovered by 2MASS, DENIS and the SDSS now have known proper motions. From these data we find a further two wide binary L dwarfs, both with M dwarf companions. A further three high-velocity L dwarfs have been discovered, which we assume are old thick disc L dwarfs. Finally, we find seven more potential members of the Hyades moving group, four members of the Ursa Major moving group and 13 potential members of the Pleiades moving group. We have found no members of the young southern moving groups, TW Hydra, Tucana/Horologium, Beta Pictoris, AB Doradus or η Chamaeleon. We have also used these new members of the Ursa Major moving group to refine the L dwarf sequence for the group that was defined by Jameson et al. (2008b).

SLC was supported by STFC for the duration of this work. MRB is supported by a STFC Advanced Fellowship. Observations were made at the UKIRT, which is operated by the Joint Astronomy Centre on behalf of the UK Particle Physics and Astronomy Research Council. Observations were also made at the NTT which is operated by ESO. This publication makes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Research has benefited from the M, L and T dwarf compendium housed at DwarfArchives.org and maintained by Chris Gelino, Davy Kirkpatrick and Adam Burgasser. This research has made use of NASA's Astrophysics Data System Bibliographic Services.

REFERENCES

Adams
T.
Davies
M. B.
Jameson
R. F.
Scally
A.
,
2002
,
MNRAS
 ,
333
,
547
Allan
A.
Jenness
T.
Economou
F.
Currie
M. J.
Bly
M. J.
,
2002
, in
Bohlender
D. A.
Durand
D.
Handley
T. H.
, eds, ASP Conf. Ser. Vol. 281,
Astronomical Data Analysis Software and Systems XI
 .
Astron. Soc. Pac.
, San Francisco, p.
311
Bannister
N. P.
Jameson
R. F.
,
2007
,
MNRAS
 ,
378
,
L24
Baraffe
I.
Chabrier
G.
Allard
F.
Hauschildt
P. H.
,
1998
,
A&A
 ,
332
,
403
Bihain
G.
Rebolo
R.
Béjar
V. J. S.
Caballero
J. A.
Bailer-Jones
C. A. L.
Mundt
R.
Acosta-Pulido
J. A.
Manchado Torres
A.
,
2006
,
A&A
 ,
458
,
805
Bouvier
J.
et al
,
2008
,
A&A
 ,
481
,
661
Burgasser
A. J.
Liu
M. C.
Ireland
M. J.
Cruz
K. L.
Dupuy
T. J.
,
2008
,
ApJ
 ,
681
,
579
Burrows
A.
Hubbard
W. B.
Lunine
J. I.
Liebert
J.
,
2001
,
Rev. Mod. Phys.
 ,
73
,
719
Caballero
J. A.
,
2007
,
ApJ
 ,
667
,
520
Casali
M.
et al
,
2007
,
A&A
 ,
467
,
777
Casewell
S. L.
Dobbie
P. D.
Hodgkin
S. T.
Moraux
E.
Jameson
R. F.
Hambly
N. C.
Irwin
J.
Lodieu
N.
,
2007
,
MNRAS
 ,
378
,
1131
Castellani
V.
Degl'Innocenti
S.
Prada Moroni
P. G.
Tordiglione
V.
,
2002
,
MNRAS
 ,
334
,
193
Chabrier
G.
Baraffe
I.
Allard
F.
Hauschildt
P. H.
,
2000
,
ApJ
 ,
542
,
464
Chereul
E.
Creze
M.
Bienayme
O.
,
1998
,
A&A
 ,
340
,
384
Costa
E.
Mendez
R. A.
Jao
W.-C.
Henry
T. J.
Subasavage
J. P.
Ianna
P. A.
,
2006
,
AJ
 ,
132
,
1234
Cruz
K. L.
Reid
I. N.
Liebert
J.
Kirkpatrick
J. D.
Lowrance
P. J.
,
2003
,
AJ
 ,
126
,
2421
Currie
M. J.
,
2003
, in
Ochsenbein
F.
Allen
M.
Egret
D.
, eds, ASP Conf. Ser. Vol. 314,
Astronomical Data Analysis Software and Systems XIII
 .
Astron. Soc. Pac.
, San Francisco, p.
460
Dehnen
W.
,
1998
,
AJ
 ,
115
,
2384
Delfosse
X.
Tinney
C. G.
Forveille
T.
Epchtein
N.
Borsenberger
J.
Fouqué
P.
Kimeswenger
S.
Tiphène
D.
,
1999
,
A&AS
 ,
135
,
41
DENIS Consortium
,
2005
,
The DENIS Database
 . VizieR Online Data Catalog
Dobbie
P. D.
Kenyon
F.
Jameson
R. F.
Hodgkin
S. T.
Hambly
N. C.
Hawkins
M. R. S.
,
2002
,
MNRAS
 ,
329
,
543
Dye
S.
et al
,
2006
,
MNRAS
 ,
372
,
1227
Gizis
J. E.
Reid
I. N.
Monet
D. G.
,
1999
,
AJ
 ,
118
,
997
Hambly
N. C.
et al
,
2001a
,
MNRAS
 ,
326
,
1279
Hambly
N. C.
Davenhall
A. C.
Irwin
M. J.
MacGillivray
H. T.
,
2001b
,
MNRAS
 ,
326
,
1315
Hawley
S. L.
et al
,
2002
,
AJ
 ,
123
,
3049
Hogan
E.
Jameson
R. F.
Casewell
S. L.
Osbourne
S. L.
Hambly
N. C.
,
2008
,
MNRAS
 ,
388
,
495
Jameson
R. F.
Casewell
S. L.
Bannister
N. P.
Lodieu
N.
Keresztes
K.
Dobbie
P. D.
Hodgkin
S. T.
,
2008a
,
MNRAS
 ,
384
,
1399
Jameson
R. F.
Lodieu
N.
Casewell
S. L.
Bannister
N. P.
Dobbie
P. D.
,
2008b
,
MNRAS
 ,
385
,
1771
Kendall
T. R.
et al
,
2007
,
A&A
 ,
466
,
1059
King
J. R.
Villarreal
A. R.
Soderblom
D. R.
Culliver
A. F.
Adelman
S. J.
,
2003
,
AJ
 ,
125
,
1980
Lawrence
A.
et al
,
2007
,
MNRAS
 ,
379
,
1599
Leggett
S. K.
et al
,
2002
,
ApJ
 ,
564
,
452
Lodieu
N.
Hambly
N. C.
Jameson
R. F.
Hodgkin
S. T.
Carraro
G.
Kendall
T. R.
,
2007a
,
MNRAS
 ,
374
,
372
Lodieu
N.
et al
,
2007b
,
MNRAS
 ,
379
,
1423
Lyngå
G.
,
1987
,
Catalogue of Open Cluster Data
 . VizierR Online Data Catalog
Madsen
S.
Dravins
D.
Lindgren
L.
,
2002
,
A&A
 ,
381
,
446
Moorwood
A.
Cuby
J. G.
Lidman
C.
,
1998
,
The Messenger
 ,
91
,
9
Moraux
E.
Bouvier
J.
Stauffer
J. R.
Cullindre
J.-C.
,
2003
,
A&A
 ,
400
,
891
Ortega
V. G.
Jilinski
E.
De La Reza
R.
Bazzanella
B.
,
2007
,
MNRAS
 ,
377
,
441
Perryman
M. A. C.
et al
,
1998
,
A&A
 ,
331
,
81
Reid
I. N.
Gizis
J. E.
Kirkpatrick
J. D.
Koerner
D. W.
,
2001
,
AJ
 ,
121
,
489
Reid
I. N.
Lewitus
E.
Burgasser
A. J.
Cruz
K. L.
,
2006
,
ApJ
 ,
639
,
1114
Schmidt
S. J.
Cruz
K. L.
Bongiorno
B. J.
Liebert
J.
Reid
I. N.
,
2007
,
AJ
 ,
133
,
2258
Skrutskie
M. F.
et al
,
2006
,
AJ
 ,
131
,
1163
Soderblom
D. R.
Mayor
M.
,
1993
,
AJ
 ,
105
,
226
Stauffer
J. R.
Schultz
G.
Kirkpatrick
J. D.
,
1998
,
ApJ
 ,
499
,
L199
Stephens
D. C.
Leggett
S. K.
,
2004
,
PASP
 ,
116
,
9
Warren
S. J.
et al
,
2007
,
MNRAS
 ,
375
,
213
Wei
J. Y.
Xu
D. W.
Dong
X. Y.
Hu
J. Y.
,
1999
,
A&AS
 ,
139
,
575
York
D. G.
et al
,
2000
,
AJ
 ,
120
,
1579
Zapatero Osorio
M. R.
Martín
E. L.
Béjar
V. J. S.
Bouy
H.
Seshpande
R.
Wainscoat
R. J.
,
2007
,
ApJ
 ,
666
,
1205
Zuckerman
B.
Song
I.
,
2004
,
ARA&A
 ,
42
,
685