J/MNRAS/449/3651 L and T dwarfs from UKIDSS LAS (Marocco+, 2015)
A large spectroscopic sample of L and T dwarfs from UKIDSS LAS:
peculiar objects, binaries, and space density.
Marocco F., Jones H.R.A., Day-Jones A.C., Pinfield D.J., Lucas P.W.,
Burningham B., Zhang Z.H., Smart R.L., Gomes J.I., Smith L.
<Mon. Not. R. Astron. Soc., 449, 3651-3692 (2015)>
=2015MNRAS.449.3651M 2015MNRAS.449.3651M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Stars, dwarfs ; Photometry, infrared ;
Equivalent widths
Keywords: binaries: spectroscopic - brown dwarfs - stars: low-mass -
stars: luminosity function, mass function
Abstract:
We present the spectroscopic analysis of a large sample of late-M, L,
and T dwarfs from the United Kingdom Deep Infrared Sky Survey. Using
the YJHK photometry from the Large Area Survey and the red-optical
photometry from the Sloan Digital Sky Survey we selected a sample of
262 brown dwarf candidates and we have followed-up 196 of them using
the echelle spectrograph X-shooter on the Very Large Telescope. The
large wavelength coverage (0.30-2.48um) and moderate resolution
(R∼5000-9000) of X-shooter allowed us to identify peculiar
objects including 22 blue L dwarfs, 2 blue T dwarfs, and 2 low-gravity
M dwarfs. Using a spectral indices-based technique, we identified 27
unresolved binary candidates, for which we have determined the
spectral type of the potential components via spectral deconvolution.
The spectra allowed us to measure the equivalent width of the
prominent absorption features and to compare them to atmospheric
models. Cross-correlating the spectra with a radial velocity standard,
we measured the radial velocity of our targets, and we determined the
distribution of the sample, which is centred at -1.7±1.2km/s with a
dispersion of 31.5km/s. Using our results, we estimated the space
density of field brown dwarfs and compared it with the results of
numerical simulations. Depending on the binary fraction, we found that
there are (0.85±0.55)x10-3 to (1.00±0.64)x10-3 objects per
cubic parsec in the L4-L6.5 range, (0.73±0.47)x10-3 to
(0.85±0.55)x10-3 objects per cubic parsec in the L7-T0.5 range,
and (0.74±0.48)x10-3 to (0.88±0.56)x10-3 objects per cubic
parsec in the T1-T4.5 range. We notice that there seems to be an
excess of objects in the L-T transition with respect to the late-T
dwarfs, a discrepancy that could be explained assuming a higher binary
fraction than expected for the L-T transition, or that objects in the
high-mass end and low-mass end of this regime form in different
environments, i.e. following different initial mass functions.
Description:
The objects presented here have been selected from the UKIDSS LAS 7th
Data Release. The details of the selection criteria can be found in
Day-Jones et al. (2013, Cat. J/MNRAS/430/1171, hereafter ADJ13).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 122 195 The objects observed
table5.dat 56 114 Spectral indices for the objects in the sample
table6.dat 51 195 The equivalent width obtained from the spectra
tablea1.dat 46 198 The log of the observations
tableb1.dat 89 195 Additional photometry for our targets, obtained
from SDSS DR10 and WISE All-Sky Data Release
--------------------------------------------------------------------------------
See also:
J/MNRAS/430/1171 : Sub-stellar birth rate from UKIDSS (Day-Jones+, 2013)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [ULAS]
6- 24 A19 --- ULAS ULAS name (JHHMMSS.ss+DDMMSS.s)
26- 29 A4 --- --- [BRLT]
30- 32 I3 --- BRLT BRLT sequential number
34- 39 F6.3 mag Ymag UKIDSS LAS DR7 Y magnitude
41- 45 F5.3 mag e_Ymag rms uncertainty on Ymag
47- 52 F6.3 mag Jmag UKIDSS LAS DR7 J magnitude
54- 58 F5.3 mag e_Jmag rms uncertainty on Jmag
60- 65 F6.3 mag Hmag UKIDSS LAS DR7 H magnitude
67- 71 F5.3 mag e_Hmag rms uncertainty on Hmag
73- 78 F6.3 mag Kmag ?=- UKIDSS LAS DR7 K magnitude
80- 84 F5.3 mag e_Kmag ? rms uncertainty on Ymag
86- 91 F6.3 mag imag ?=- SDSS DR7 i magnitude
93- 97 F5.3 mag e_imag ? rms uncertainty on imag
99-104 F6.3 mag zmag ?=- SDSS DR7 z magnitude
106-110 F5.3 mag e_zmag ? rms uncertainty on zmag
112-115 A4 --- SpType MK spectral type derived in Section 3.1
117-119 F3.1 --- e_SpType rms uncertainty on SpType
121-122 A2 --- Ref Discovery reference (1)
--------------------------------------------------------------------------------
Note (1): Discovery reference:
1 = Day-Jones et al. (2013, Cat. J/MNRAS/430/1171)
2 = Geballe et al. (2002ApJ...564..466G 2002ApJ...564..466G)
3 = Hawley et al. (2002, Cat. J/AJ/123/3409)
4 = Knapp et al. (2004, Cat. J/AJ/127/3553)
5 = Burningham et al. (2013, Cat. J/MNRAS/433/457)
6 = Burningham et al. (2010MNRAS.406.1885B 2010MNRAS.406.1885B)
7 = Leggett et al. (2000ApJ...536L..35L 2000ApJ...536L..35L)
8 = Chiu et al. (2006, Cat. J/AJ/131/2722)
9 = Pinfield et al. (2008MNRAS.390..304P 2008MNRAS.390..304P)
10 = Fan et al. (2000AJ....119..928F 2000AJ....119..928F)
11 = Marocco et al. (2014MNRAS.439..372M 2014MNRAS.439..372M)
- = object was previously unpublished
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [BRLT]
5- 7 I3 --- BRLT BRLT sequential number
9- 12 A4 --- SpType MK spectral type
14- 16 F3.1 --- e_SpType rms uncertainty on SpType
18- 21 F4.2 --- H2O-J H2O-J spectral index (1)
23- 26 F4.2 --- H2O-H H2O-H spectral index (1)
28- 31 F4.2 --- H2O-K H2O-K spectral index (1)
33- 36 F4.2 --- CH4-J CH4-J spectral index (1)
38- 41 F4.2 --- CH4-H CH4-H spectral index (1)
43- 46 F4.2 --- CH4-K CH4-K spectral index (1)
48- 51 F4.2 --- K/J K/J spectral index (1)
53- 56 F4.2 --- H-dip H-dip spectral index (1)
--------------------------------------------------------------------------------
Note (1): Spectral indices definitions:
-----------------------------------------------------------
Index Numerator Denominator Feature
range range
-----------------------------------------------------------
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
-----------------------------------------------------------
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [BRLT]
5- 7 I3 --- BRLT BRLT sequential number
9- 12 A4 --- SpType MK spectral type
14- 16 F3.1 --- e_SpType rms uncertainty on SpType
18- 22 F5.2 0.1nm EWNaI ?=- NaI (1.139um) equivalent width (1)
23 A1 --- u_EWNaI [i] i: measurements with relative errors
larger than 0.33
25- 29 F5.2 0.1nm EWKI1 ?=- KI (1.169um) equivalent width (1)
30 A1 --- u_EWKI1 [i] i: measurements with relative errors
larger than 0.33
32- 36 F5.2 0.1nm EWKI2 ?=- KI (1.177um) equivalent width (1)
37 A1 --- u_EWKI2 [i] i: measurements with relative errors
larger than 0.33
39- 43 F5.2 0.1nm EWKI3 ?=- KI (1.244um) equivalent width (1)
44 A1 --- u_EWKI3 [i] i: measurements with relative errors
larger than 0.33
46- 50 F5.2 0.1nm EWKI4 ?=- KI (1.253um) equivalent width (1)
51 A1 --- u_EWKI4 [i] i: measurements with relative errors
larger than 0.33
--------------------------------------------------------------------------------
Note (1): Missing entries indicate the non-detection of the line, due either to
the line being too weak or the spectrum being too noisy.
For the details on how these values were calculated, see Section 4.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [BRLT]
5- 7 I3 --- BRLT BRLT sequential number
9- 18 A10 "date" Obs.date Observation date
20- 29 A10 --- Std Telluric standard star name
32- 36 A5 --- SpType MK spectral type of telluric standard star
39- 46 A8 --- SpStd Spectrophotometric standard used
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [BRLT]
5- 7 I3 --- BRLT BRLT sequential number
9- 14 F6.3 mag umag ?=- SDSS u magnitude
16- 20 F5.3 mag e_umag ? rms uncertainty on umag
22- 27 F6.3 mag gmag ?=- SDSS g magnitude
29- 33 F5.3 mag e_gmag ? rms uncertainty on gmag
35- 40 F6.3 mag rmag ?=- SDSS r magnitude
42- 46 F5.3 mag e_rmag ? rms uncertainty on rmag
48- 53 F6.3 mag W1 ?=- WISE W1 magnitude
55- 59 F5.3 mag e_W1 ? rms uncertainty on W1
61 A1 --- l_W2 Limit flag on W2
62- 67 F6.3 mag W2 ?=- WISE W2 magnitude
69- 73 F5.3 mag e_W2 ? rms uncertainty on W2
75 A1 --- l_W3 Limit flag on W3
76- 81 F6.3 mag W3 ?=- WISE W3 magnitude
83- 87 F5.3 mag e_W3 ? rms uncertainty on W3
89 A1 --- Note [ab] Note (1)
--------------------------------------------------------------------------------
Note (1): Notes as follows:
a = WISE magnitudes likely affected by blending with nearby source or
background galaxy
b = WISE magnitudes likely affected by diffraction spikes of nearby source
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 14-Dec-2015