J/A+A/527/A24 Spectra of low-mass stars in Upper Sco (Lodieu+, 2011)
Multi-fibre optical spectroscopy of low-mass stars and brown dwarfs
in Upper Scorpius.
Lodieu N., Dobbie P.D., Hambly N.C.
<Astron. Astrophys. 527, A24 (2011)>
=2011A&A...527A..24L 2011A&A...527A..24L
ADC_Keywords: Clusters, open ; Stars, late-type ; Spectroscopy
Keywords: technique: spectroscopic -
galaxy: open clusters and associations: individual: Upper Scorpius -
brown dwarfs - stars: luminosity function, mass function
Abstract:
We have obtained multi-fibre intermediate-resolution optical
spectroscopy of 94 photometric and proper motion selected low-mass
star and brown dwarf candidates in Upper Sco with the AAOmega
spectrograph on the Anglo-Australian Telescope. We have estimated the
spectral types and measured the equivalent widths of youth and gravity
diagnostic features to confirm the spectroscopic membership of about
95% of the photometric and proper motion candidates extracted from
6.5 square degrees surveyed in Upper Sco by the UKIRT Infrared Deep
Sky Survey (UKIDSS) Galactic Clusters Survey (GCS). We have estimated
the effective temperatures and masses for each new spectroscopic
member using the latest evolutionary models available for low-mass
stars and brown dwarfs. Combining the current optical spectroscopy
presented here with near-infrared spectroscopy obtained for the
faintest photometric candidates, we confirm the shape and slope of our
earlier photometric mass function. The luminosity function drawn from
the spectroscopic sample of 113 USco members peaks at around M6 and is
flat at later spectral type. The mass function may peak at 0.2M☉
and is quite flat in the substellar regime. We observe a possible
excess of cool low-mass brown dwarfs compared to IC 348 and the
extrapolation of the field mass functions, supporting the original
hypothesis that Upper Sco may possess an excess of brown dwarfs
compared.
Description:
Coordinates (J2000), ZYJHK photometry from the UKIDSS Galactic
Clusters Survey, and proper motions derived from the UKIDSS/2MASS
cross-match (in arcsec/yr) of stars in the AAOmega field-of-view
ordered by increasing Z magnitude. The last column provides a
tentative estimate of the spectral type. Data obtained with the
AAOmega spectrograph on the Anglo-Australian telescope in May 2007.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 106 624 Coordinates, photometry and astrometry of
field stars in the AAOmega field-of-view
tablea5.dat 140 109 Confirmed spectroscopic members of the USco
AAT/AAOmega (A) and Gemini/GNIRS (G)
candid.dat 66 114 List of USco member candidates, with spectra
sp/* . 809 Fits files of spectra
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000.0)
4- 5 I2 min RAm Right ascension (J2000.0)
7- 11 F5.2 s RAs Right ascension (J2000.0)
13 A1 --- DE- Declination sign (J2000.0)
14- 15 I2 deg DEd Declination (J2000.0)
17- 18 I2 arcmin DEm Declination (J2000.0)
20- 23 F4.1 arcsec DEs Declination (J2000.0)
25- 30 F6.3 mag Zmag Z-band magnitude from the UKIDSS GCS
32- 37 F6.3 mag Ymag Y-band magnitude from the UKIDSS GCS
39- 44 F6.3 mag Jmag J-band magnitude from the UKIDSS GCS
46- 51 F6.3 mag Hmag H-band magnitude from the UKIDSS GCS
53- 58 F6.3 mag Kmag K-band magnitude from the UKIDSS GCS
60- 66 F7.2 mas/yr pmRA Proper motion in right ascension
68- 74 F7.2 mas/yr pmDE Proper motion in declination
76- 95 A20 --- SpType Spectral type of the object
97-106 A10 --- Name Object name given when assigning fibres,
fieldNNNNN (1)
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Note (1): spectra files are named sp/specfieldNNNNnorm.fits
(in "sp" subdirectory)
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Byte-by-byte Description of file: tablea5.dat
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Bytes Format Units Label Explanations
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1 A1 --- F [AG] A for AAT/AAOmega, G for Gemini/GNIRS
3- 4 I2 h RAh Right ascension (J2000.0)
6- 7 I2 min RAm Right ascension (J2000.0)
9- 13 F5.2 s RAs Right ascension (J2000.0)
14 A1 --- DE- Declination sign (J2000.0)
15- 16 I2 deg DEd Declination (J2000.0)
18- 19 I2 arcmin DEm Declination (J2000.0)
21- 24 F4.1 arcsec DEs Declination (J2000.0)
26- 31 F6.3 mag Jmag UKIDSS/J-band magnitude
33- 39 F7.1 0.1nm WHa1 ?=- Hα equivalent width
41- 46 F6.1 0.1nm WHa2 ?=- Hα equivalent width
48- 53 F6.1 0.1nm WHa3 ?=- Hα equivalent width
55- 59 F5.1 0.1nm WHa4 ?=- Hα equivalent width
61- 63 F3.1 0.1nm WNaI1 ?=- NaI equivalent width
65- 67 F3.1 0.1nm WNaI2 ?=- NaI equivalent width
69- 71 F3.1 0.1nm WNaI3 ?=- NaI equivalent width
73- 75 F3.1 0.1nm WNaI4 ?=- NaI equivalent width
77- 79 F3.1 0.1nm WKI1 ?=- KI equivalent width
81- 83 F3.1 0.1nm WKI2 ?=- KI equivalent width
85- 87 F3.1 0.1nm WKI3 ?=- KI equivalent width
89- 91 F3.1 0.1nm WKI4 ?=- KI equivalent width
93- 96 F4.2 --- TiO7140 ?=- TiO7140 spectral index
98-101 F4.2 --- TiO8465 ?=- TiO8465 spectral index
103-106 F4.2 --- Na8189 ?=- Na8189 spectral index
108-111 F4.2 --- PC3 ?=- PC3 spectral index (1)
113-115 F3.1 --- Sp3 ?=- M subclass of spectral type,
derived from PC3 spectral index
117-121 F5.2 --- SpT M subclass of spectral type,
estimated from spectral template
123-126 I4 K Teff Effective temperature
128-133 F6.3 Lsun Lbol Bolometric luminosity
135-140 F6.4 Msun Mass Derived mass
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Note (1): defined in Martin et al., 1996ApJ...469..706M 1996ApJ...469..706M. Ratio of
pseudo-continuums [in nm]: (823.5-286.5)/(754-758).
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Byte-by-byte Description of file: candid.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg Right ascension in decimal degrees (J2000)
13- 23 F11.7 deg DEdeg Declination in decimal degrees (J2000)
25- 26 I2 h RAh Right ascension (J2000.0)
28- 29 I2 min RAm Right ascension (J2000.0)
31- 35 F5.2 s RAs Right ascension (J2000.0)
37 A1 --- DE- Declination sign (J2000.0)
38- 39 I2 deg DEd Declination (J2000.0)
41- 42 I2 arcmin DEm Declination (J2000.0)
44- 47 F4.1 arcsec DEs Declination (J2000.0)
49- 60 A12 --- Name Candidate name, USco_candNNN
62 A1 --- Red [R] red spectrum in "sp" subdirectory (1)
66 A1 --- Blue [B] blue spectrum in "sp" subdirectory (1)
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Note (1): spectra in "sp" subdirectory,
* red (570-880nm) spectra files named specUScocandNNN_norm.fits
* blue (370-570nm) spectra files named specUScocandNNNBLUEcomb.fits.
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Acknowledgements:
Nicolas Lodieu, nlodieu (at)iac.es
(End) Nicolas Lodieu [IAC Tenerife, Spain], Patricia Vannier [CDS] 17-Dec-2010