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J/AJ/133/439   Luminosity function of M7-L8 ultracool dwarfs      (Cruz+, 2007)

Meeting the cool neighbors. IX. The luminosity function of M7-L8 ultracool dwarfs in the field. Cruz K.L., Reid I.N., Kirkpatrick J.D., Burgasser A.J., Liebert J., Solomon A.R., Schmidt S.J., Allen P.R., Hawley S.L., Covey K.R. <Astron. J., 133, 439-467 (2007)> =2007AJ....133..439C
ADC_Keywords: Stars, dwarfs ; Stars, late-type ; Photometry, infrared Keywords: Galaxy: stellar content - solar neighborhood - stars: late-type - stars: low-mass, brown dwarfs - stars: luminosity function, mass function Abstract: We present a 20pc, volume-limited sample of M7-L8 dwarfs created through spectroscopic follow-up of sources selected from the Two Micron All Sky Survey Second Incremental Release Point Source Catalog. In this paper we present optical spectroscopy of 198 candidate nearby ultracool dwarfs, including 12 late-M and L dwarfs likely to be within 20pc of the Sun and 94 more distant late-type dwarfs. We have also identified five ultracool dwarfs with spectral signatures of low gravity. Combining these data with previous results, we define a sample of 99 ultracool dwarfs in 91 systems within 20pc. These are used to estimate the J- and K-band luminosity functions for dwarfs with optical spectral types between M7 and L8 (10.5<MJ<15, 9.5<MKs<13). We find a space density of 4.9x10-3/pc3 for late-M dwarfs (M7-M9.5) and a lower limit of 3.8x10-3/pc3 for L dwarfs. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 142 17 M6-L8 Dwarfs Discovered Within 20pc table3.dat 142 103 M7-L8 Dwarfs Discovered Outside 20pc table4.dat 142 34 Early-to-Mid Type M Dwarfs Discovered Outside 20pc table5.dat 65 33 Spectroscopically confirmed giants table6.dat 65 17 Spectroscopically confirmed carbon stars table9.dat 149 99 The 20pc 2MU2 sample used to estimate the luminosity function table10.dat 149 33 Objects with distance estimates within 1σ of 20 parsecs refs.dat 83 109 References
See also: II/241 : 2MASS Catalog Intermediate Data Release (IPAC/UMass, 2000) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/AJ/123/2806 : Nearby stars in the NLTT catalogue (Reid+, 2002) J/AJ/123/2822 : Photometry of southern NLTT stars (Reid+, 2002) J/AJ/123/2828 : Spectroscopy of northern NLTT stars (Cruz+, 2002) J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003) J/AJ/126/2449 : Nearby ultracool dwarfs in galactic plane (Reid+, 2003) J/AJ/126/3007 : Spectroscopy of faint red NLTT dwarfs (Reid+, 2003) J/AJ/128/463 : A preliminary 20pc census from the NLTT catalogue (Reid+, 2004) J/AJ/133/2825 : Activity and kinematics of ultracool dwarfs (Schmidt+, 2007) Byte-by-byte Description of file: table[234].dat
Bytes Format Units Label Explanations
1- 14 A14 --- 2MASSI The 2MASSI designation (G1) 15 A1 --- m_2MASSI [ABC] Multiplicity index on 2MASSI 17- 21 I5 --- 2MUCD ? The 2MUCD number 23- 50 A28 --- OName Other name(s) 52 A1 --- n_OName [b] Common proper motion star (2) 54- 59 F6.3 mag Jmag ? 2MASS J band magnitude 61- 65 F5.3 mag J-H ? 2MASS (J-H) color 67- 71 F5.3 mag J-K ? 2MASS (J-KS) color 73- 82 A10 "YYYY/MM/DD" Obs.Date ? UT date of observation 84- 91 A8 --- Tel Telescope used in the observation 93-100 A8 --- SpType Optical spectral type 102 A1 --- f_SpType [abcde] Individual note on the spectrum (3) 104-108 F5.2 mag JMAG Absolute J band magnitude 110-113 F4.2 mag e_JMAG Uncertainty in JMAG 115-119 F5.1 pc Dist Distance 121-125 F5.1 pc e_Dist Uncertainty in Dist 127 A1 --- f_Dist [l] l: Dist and e_Dist represent the range in the distance 129-142 A14 --- Refs Other references, in refs.dat file
Note (2): b = Ultracool common proper motion companion to a star as discussed in Section 5.5. Note (3): Notes as follows: a = This object has been resolved into two components (Reid et al., 2006ApJ...639.1114R) and the spectral type listed here is for the unresolved system. The distance and JMAG for the system is based on a trigonometric parallax (Thorstensen & Kirkpatrick, 2003PASP..115.1207T). b = A spectrum of this object is shown by Bessell (1991AJ....101..662B) but not mentioned in the text nor assigned a spectral type. It appears to have been overlooked in the subsequent literature on late-type M dwarfs. To our knowledge, it was first formally assigned a spectral type by Reid et al. (2003AJ....125..354R, Paper VII) using the same data presented here. c = Spectrum shows lithium absorption line as shown in Figure 2 and discussed in Section 5.1. d = Probable L/T binary (Cruz et al., 2004ApJ...604L..61C; Burgasser et al., 2006ApJS..166..585B). Combined-light optical spectral type from Kirkpatrick et al., in prep. e = Variable and/or flaring object that will be discussed in detail in Schmidt et al., in prep.
Byte-by-byte Description of file: table5.dat table6.dat
Bytes Format Units Label Explanations
1- 14 A14 --- 2MASSI 2MASSi designation (G1) 16- 21 F6.3 mag Jmag J magnitude 23- 27 F5.3 mag J-H J-H colour index 29- 33 F5.3 mag J-Ks J-Ks colour index 35- 44 A10 "YYYY/MM/DD" Obs.Date UT date of observation 46- 52 A7 --- Tel Telescope used 54- 63 A10 --- SpType Optical spectral type 65 A1 --- n_SpType [b] b: Spectrum displays Hα in emission
Byte-by-byte Description of file: table9.dat table10.dat
Bytes Format Units Label Explanations
1- 14 A14 --- 2MASSI The 2MASSI designation (G1) 15 A1 --- m_2MASSI [ABC] Multiplicity index on 2MASSI 17 A1 --- f_2MASSI [eghl] Individual note on 2MASSI (2) 19- 23 I5 --- 2MUCD ? The 2MUCD number 25- 51 A27 --- OName Other name(s) 52 A1 --- n_OName [de] Individual note on OName (3) 54- 59 F6.3 mag Jmag ? 2MASS J band magnitude 61- 65 F5.3 mag J-H ? 2MASS (J-H) color index 67- 71 F5.3 mag J-K ? 2MASS (J-KS) color index 73- 77 A5 --- SpType Optical spectral type (4) 78 A1 --- f_SpType [efhijkl] Individual note on spectrum (2) 80- 84 F5.2 mag JMAG Absolute J band magnitude 86- 89 F4.2 mag e_JMAG Uncertainty in JMAG 91 A1 --- f_JMAG [g] Individual note on JMAG (2) 93- 97 F5.2 mag KsMAG ? Absolute Ks band magnitude 99-102 F4.2 mag e_KsMAG ? Uncertainty in KsMAG 104-108 F5.2 pc Dist Distance 110-113 F4.2 pc e_Dist Uncertainty in Dist 115-122 A8 --- n_Dist Method of distance determination (7) 124-140 A17 --- DRefs Discovery reference(s) (table9) or reference(s) (table10), in refs.dat file 142-149 A8 --- PRefs Parallax reference(s) (table9), in refs.dat file
Note (2): Notes as follows: e = Bouy et al. (2005AJ....129..511B) report a T dwarf as a possible third component to the system. The T dwarf is not included in the luminosity function estimate. f = Variable and/or flaring object that will be discussed in detail in Schmidt et al., in prep. g = The absolute magnitude for this object, based on a trigonometric parallax, is brighter than our brightest JMAG bin and is not included in our space density per magnitude analysis. However, it is included in our estimates of the total space densities of ultracool dwarfs. It is also a suspected unresolved binary as discussed in Section 5.6. h = This object has been resolved into an L/T binary by Burgasser et al. (2005ApJ...634L.177B). The T dwarf is not included in the luminosity function estimate. i = This object displays features of low gravity and a spectral type of M9: was used to estimate JMAG. j = Change in spectral type from Paper V (Cruz et al., Cat. J/AJ/126/2421). k = Suspected low-metallicity dwarf as discussed in Section 5.4. l = Suspected unresolved binary as discussed in Section 5.6. Note (3): Notes as follows: d = Henry et al. (1999ApJ...512..864H) reported the possible existence of a fourth component, LHS 1070D, at a separation of 50mas; further observations have shown the original apparent detection to be spurious (T. Henry 2006, priv. comm.). e = Bouy et al. (2005AJ....129..511B) report a T dwarf as a possible third component to the system. The T dwarf is not included in the luminosity function estimate. Note (4): A single or double colon indicates an uncertainty on the spectral type of ±1 or ±2 types respectively due to a low signal-to-noise spectrum. A single colon is also used to indicate uncertainty on the spectral type of individual objects in multiple systems where resolved spectroscopy has not been obtained. Note (7): Distance flag as follows: ST = Distance are spectrophotometric Parallax = Distance are from trigonometric parallax
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Ref Reference code 5- 23 A19 --- BibCode BibCode 25- 49 A25 --- Aut Author's name 51- 83 A33 --- Com Comments
Global notes: Note (G1): The 2MASS designation is 2MASSI Jhhmmss[.]s-ddmmss.
History: From electronic version of the journal References: Reid et al., Paper I 2002AJ....123.2806R, Cat. J/AJ/123/2806 Reid et al., Paper II 2002AJ....123.2822R, Cat. J/AJ/123/2822 Cruz et al., Paper III 2002AJ....123.2828C, Cat. J/AJ/123/2828 Reid et al., Paper IV 2003AJ....125..354R Cruz et al., Paper V 2003AJ....126.2421C, Cat. J/AJ/126/2421 Reid Paper VI 2003AJ....126.2449R, Cat. J/AJ/126/2449 Reid et al., Paper VII 2003AJ....126.3007R, Cat. J/AJ/126/3007 Reid et al., Paper VIII 2004AJ....128..463R, Cat. J/AJ/128/463 Reid et al., Paper XI 2007AJ....133.2825R, Cat. J/AJ/133/2825
(End) Patricia Vannier [CDS] 17-Aug-2007
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