J/MNRAS/430/1171 Sub-stellar birth rate from UKIDSS (Day-Jones+, 2013)
The sub-stellar birth rate from UKIDSS.
Day-Jones A.C., Marocco F., Pinfield D.J., Zhang Z.H., Burningham B.,
Deacon N., Ruiz M.T., Gallardo J., Jones H.R.A., Lucas P.W.L.,
Jenkins J.S., Gomes J., Folkes S.L., Clarke J.R.A.
<Mon. Not. R. Astron. Soc., 430, 1171-1187 (2013)>
=2013MNRAS.430.1171D 2013MNRAS.430.1171D
ADC_Keywords: Stars, late-type ; YSOs ; Photometry ; Spectroscopy
Keywords: brown dwarfs - stars: low-mass -
stars: luminosity function, mass function
Abstract:
We present a new sample of mid-L to mid-T dwarfs with effective
temperatures of 1100-1700K selected from the UKIDSS Large Area Survey
(LAS) and confirmed with infrared spectra from X-shooter/Very Large
Telescope. This effective temperature range is especially sensitive to
the formation history of Galactic brown dwarfs and allows us to
constrain the form of the sub-stellar birth rate, with sensitivity to
differentiate between a flat (stellar like) birth rate and an
exponentially declining form. We present the discovery of 63 new L and
T dwarfs from the UKIDSS LAS DR7, including the identification of 12
likely unresolved binaries, which form the first complete sub-set from
our programme, covering 495 square degrees of sky, complete to J=18.1.
We compare our results for this sub-sample with simulations of
differing birth rates for objects of masses 0.10-0.03M☉ and ages
1-10Gyr. We find that the more extreme birth rates (e.g. a halo type
form) can likely be excluded as the true form of the birth rate. In
addition, we find that although there is substantial scatter we find a
preference for a mass function, with a power-law index α in the
range -1<α<0 that is consistent (within the errors) with the
studies of late T dwarfs.
Description:
We select our sample from DR7 of the ULAS, selecting objects with
declination ≤20°, J<18.1 and Y-J>0.8. This list of candidates was
then cross-matched against SDSS DR7 to identify objects with optical
counterparts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 76 Photometry of a sub-sample of brown dwarfs
table4.dat 60 68 Spectral details of observed targets
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See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Name of brown dwarf
17 A1 --- r_Name Discovery reference (1)
19- 22 A4 --- --- [BRLT]
23- 25 I3 --- BRLT [1/344]? BRLT number
27- 28 I2 h RAh Right ascension (J2000)
30- 31 I2 min RAm Right ascension (J2000)
33- 34 I2 s RAs Right ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 44 I2 arcsec DEs Declination (J2000)
46- 50 F5.2 mag Jmag UKIDSS J magnitude (2)
52- 55 F4.2 mag Y-J UKIDSS Y-J colour index (2)
57- 61 F5.2 mag J-H UKIDSS J-H colour index (2)
63- 67 F5.2 mag J-K ?=- UKIDSS J-K colour index (2)
69- 72 F4.2 mag z-J ?=- UKIDSS-SDSS z-J colour index (2)
74- 78 F5.2 mag i-z ?=- UKIDSS-SDSS i-z colour index (2)
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Note (1): Original discovery paper as follows:
a = Geballe et al. (2002ApJ...564..466G 2002ApJ...564..466G)
b = Hawley et al. (2002, Cat. J/AJ/123/3409 )
c = Burningham et al. (2010MNRAS.406.1885B 2010MNRAS.406.1885B)
d = Knapp et al. (2004, Cat. J/AJ/127/3553))
e = Lodieu et al. (2007, Cat. J/MNRAS/374/372)
f = Chiu et al. (2006, Cat. J/AJ/131/2722)
g = Scholz (2010A&A...510A...8F 2010A&A...510A...8F)
h = Burningham et al. (in preparation)
Note (2): Photometry from UKIDSS (Hewett et al. 2006MNRAS.367..454H 2006MNRAS.367..454H,
See Cat. II/316, II/319), and SDSS (Fukugita et al. 1996AJ....111.1748F 1996AJ....111.1748F,
See Cat. V/139).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [BRLT]
5- 7 I3 --- BRLT [1/344] BRTL number
9- 12 A4 --- SpT MK spectral type
14- 16 F3.1 --- e_SpT rms uncertainty on SpType
18- 21 F4.2 --- H2O-J H2O-J binary index (1)
23- 26 F4.2 --- H2O-H H2O-H binary index (1)
28- 31 F4.2 --- H2O-K H2O-K binary index (1)
33- 36 F4.2 --- CH4-J CH4-J binary index (1)
38- 41 F4.2 --- CH4-H CH4-H binary index (1)
43- 47 F5.2 --- CH4-K CH4-K binary index (1)
49- 52 F4.2 --- K/J K/J binary index (1)
54- 57 F4.2 --- H-dip H-dip binary index (1)
59- 60 A2 --- Note [SC WC] Notes (2)
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Note (1): Binary indices as defined by Burgasser et al. (2006, Cat.
J/ApJ/637/1067), except for H-dip, which is defined by Burgasser et al.
(2010, Cat. J/ApJ/710/1142).
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Index Numerator range Denominator range Feature
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H2O-J 1.14-1.165 1.26-1.285 1.15um H2O
H2O-H 1.48-1.52 1.56-1.60 1.4um H2O
H2O-K 1.975-1.995 2.08-2.10 1.9um H2O
CH4-J 1.315-1.34 1.26-1.285 1.32um CH4
CH4-H 1.635-1.675 1.56-1.60 1.65um CH4
CH4-K 2.215-2.255 2.08-2.12 2.2um CH4
K/J 2.060-2.10 1.25-1.29 J-K colour
H-dip 1.61-1.64 1.56-1.59+1.66-1.69 1.65um CH4
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Note (2): Notes as follows:
SC = Strong binary candidate
WC = Weak binary candidate
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 07-Apr-2014