J/A+A/446/485 New very low-mass members in Taurus (Guieu+, 2006)
Seventeen new very low-mass members in Taurus.
The brown dwarf deficit revisited.
Guieu S., Dougados C , Monin J-L , Magnier E., Martin E.L
<Astron. Astrophys. 446, 485 (2006)>
=2006A&A...446..485G 2006A&A...446..485G
ADC_Keywords: Stars, M-type ; Stars, dwarfs ; Photometry, infrared
Keywords: stars: low-mass, brown dwarfs - stars: late-type -
stars: luminosity function, mass function - stars: pre-main sequence
Abstract:
We have performed a large scale optical survey of the Taurus cloud,
covering a total area of 28deg2, and encompassing the densest parts
of the cloud as well as their surroundings, down to a mass detection
limit of 15 Jupiter masses. We present the optical spectroscopic
follow-up observations of 97 photometrically selected potential new
low-mass Taurus members, of which 27 are strong late-M spectral type
SpType<M4V candidates. We derive spectral types, visual absorption and
luminosity class estimates and discuss our criteria to assess Taurus
membership. These observations reveal 5 new VLM Taurus members and 12
new brown dwarfs. Combining our observations with previously published
results, we derive an updated substellar to stellar ratio in Taurus of
Rss=0.23±0.05. This ratio now appears consistent with the value
previously derived in the Trapezium cluster under similar assumptions
of 0.26±0.04. We find indications that the relative numbers of
brown dwarfs with respect to stars is decreased by a factor 2 in the
central regions of the aggregates with respect to the more distributed
population. Our findings are best explained in the context of the
embryo-ejection model where brown dwarfs originate from dynamical
interactions in small N unstable multiple systems.
Description:
Derived parameters and spectral properties of sources identified as
field stars or with uncertain membership (table 3) and for confirmed
Taurus members (table 4).
Table 5 present photometry and derived parameters for previous known
(top) and new (bottom) Taurus Brown Dwarfs and very low mass stars
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 90 74 Derived parameters and spectral properties of
sources identified as field stars or with
uncertain membership
table4.dat 90 23 Same as table 3 for confirmed Taurus members
table5.dat 62 23 Photometry and derived parameters for previously
known and new Taurus BD and VLM members
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See also:
J/AJ/127/2856 : Brown dwarfs in the 2MASS Survey (Burgasser+, 2004)
Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
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1- 17 A17 ---- 2MASS 2MASS Name
18 A1 ---- n_2MASS [*] *: candidates not selected with the
primary selection method (see Sect. 2.1)
20- 31 A12 ---- Name Target Name (only in table4.dat)
33 I1 ---- Run Run identification number
35- 36 I2 h RAh Right ascension (J2000)
38- 39 I2 min RAm Right ascension (J2000)
41- 46 F6.3 s RAs Right ascension (J2000)
48 A1 --- DE- Declination sign (J2000)
49- 50 I2 deg DEd Declination (J2000)
52- 53 I2 arcmin DEm Declination (J2000)
55- 60 F6.3 arcsec DEs Declination (J2000)
62- 66 F5.2 mag AV Extinction in V band
68- 72 F5.2 0.1nm EWNa Equivalent width of Na line
74- 80 F7.2 0.1nm EWHa Equivalent width of Halpha line
82- 86 A5 --- SpType MK spectral type (Mn.nn)
88- 90 A3 --- LClass Luminosity class derived from spectral fitting
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 12 A12 ---- Name Target Name
14- 18 A5 ---- SpType MK spectral type
20- 22 F3.1 mag AV Extinction in V band
24- 30 F7.4 [solLum] log10(L) logarithm of luminosity
32- 35 I4 K Teff Effective Temperature
37- 41 F5.2 mag Imag I magnitude
43- 46 F4.2 mag I-z ?=- I-z color index
48- 51 F4.2 mag J-H J-H color index
53- 56 F4.2 mag H-Ks H-K color index
58- 62 F5.2 mag Ksmag Ks magnitude
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Acknowledgements: Sylvain Guieu, sylvain.guieu(at)obs.ujf-grenoble.fr
(End) Sylvain Guieu [LAG], Patricia Vannier [CDS] 04-Oct-2005