J/MNRAS/444/1793 25 Ori group low-mass stars (Downes+, 2014)
The low-mass star and sub-stellar populations of the 25 Orionis group.
Downes J.J., Briceno C., Mateu C., Hernandez J., Vivas A.K., Calvet N.,
Hartmann L., Petr-Gotzens M.G., Allen L.
<Mon. Not. R. Astron. Soc., 444, 1793-1811 (2014)>
=2014MNRAS.444.1793D 2014MNRAS.444.1793D
ADC_Keywords: Clusters, open ; Stars, M-type ; Photometry, infrared
Keywords: brown dwarfs - stars: low-mass -
open clusters and associations: individual: 25 Orionis
Abstract:
We present the results of a survey of the low-mass star and brown
dwarf population of the 25 Orionis group. Using optical photometry
from the CIDA (Centro de Investigaciones de Astronomia Francisco J.
Duarte, Merida, Venezuela) Deep Survey of Orion, near-IR photometry
from the Visible and Infrared Survey Telescope for Astronomy and
low-resolution spectroscopy obtained with Hectospec at the MMT
telescope, we selected 1246 photometric candidates to low-mass stars
and brown dwarfs with estimated masses within 0.02≲M/M☉≲0.8
and spectroscopically confirmed a sample of 77 low-mass stars as new
members of the cluster with a mean age of ∼7Myr. We have obtained a
system initial mass function of the group that can be well described
by either a Kroupa power-law function with indices
α3=-1.73±0.31 and α2=0.68±0.41 in the mass ranges
0.03≤M/M☉≤0.08 and 0.08≤M/M☉≤0.5,
respectively, or a Scalo lognormal function with coefficients
mc=0.21+0.02-0.02 and σ=0.36±0.03 in the mass range
0.03≤M/M☉≤0.8. From the analysis of the spatial distribution
of this numerous candidate sample, we have confirmed the east-west
elongation of the 25 Orionis group observed in previous works, and
rule out a possible southern extension of the group. We find that the
spatial distributions of low-mass stars and brown dwarfs in 25 Orionis
are statistically indistinguishable. Finally, we found that the
fraction of brown dwarfs showing IR excesses is higher than for
low-mass stars, supporting the scenario in which the evolution of
circumstellar discs around the least massive objects could be more
prolonged.
Description:
Multi-epoch optical V-, R-, I-band and Hα observations across
the entire Orion OB1 association (spanning ∼180deg2) were obtained
as part of the CVSO (Briceno et al., 2005AJ....129..907B 2005AJ....129..907B, Cat.
J/AJ/129/907), being conducted since 1998 with the Jurgen Stock
1.0/1.5 Schmidt-type telescope and the 8000x8000-pixel QUEST-I CCD
Mosaic camera, at the National Astronomical Observatory of Venezuela.
During 2009 a new dedicated 4m survey telescope, the Visible and
Infrared Survey Telescope for Astronomy (VISTA), located at ESO's
Paranal Observatory, was commissioned by the VISTA consortium. For the
Galactic Science Verification of VISTA, an ∼30deg2 area of the
Orion OB1 association, which included the Orion Belt region, part of
the Orion A cloud, the 25 Orionis and σ Ori clusters, was imaged
in the Z, Y, J, H and Ks filters, during 2009 October 16 to
November 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 120 75 Photometric catalogue of the new spectroscopically
confirmed LMS of the 25 Orionis group
table5.dat 43 77 Spectroscopic catalogue of the new confirmed
members of the 25 Orionis group
sp/* . 76 Individual spectrum figure
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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 I4 --- ID [1232/1400] ID number
6- 15 F10.7 deg RAdeg Right ascension (J2000)
17- 25 F9.7 deg DEdeg Declination (J2000)
27- 31 F5.2 mag Vcmag ? Cousins V magnitude
33- 37 F5.2 mag Rcmag ? Cousins R magnitude
39- 43 F5.2 mag Icmag Cousins I magnitude
45- 49 F5.2 mag Jmag ? VISTA J magnitude
51- 55 F5.2 mag Zmag VISTA Z magnitude
57- 61 F5.2 mag Ymag ? VISTA Y magnitude
63- 67 F5.2 mag Hmag VISTA H magnitude
69- 73 F5.2 mag Ksmag VISTA Ks magnitude
75- 79 F5.2 mag [3.6] ? Spitzer/IRAC 3.6µm magnitude
81- 85 F5.2 mag [4.5] ? Spitzer/IRAC 4.5µm magnitude
87- 91 F5.2 mag [5.8] ? Spitzer/IRAC 5.8µm magnitude
93- 97 F5.2 mag [8.0] ? Spitzer/IRAC 8.0µm magnitude
99-103 F5.2 mag [3.4] ? WISE 3.4um magnitude
105-109 F5.2 mag [4.6] ? WISE 4.6um magnitude
111-115 F5.2 mag [12] ? WISE 12um magnitude
117-120 F4.2 mag [22] ? WISE 22um magnitude
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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- 4 I4 --- ID ID number
6- 10 A5 --- SpT MK Spectral type
12- 16 F5.1 0.1nm EWHa [-93/-1] Hα equivalent width
18- 19 I2 --- LiI [-1/1] Li detection flag: -1 = non-detection,
0=uncertain detection, 1=certain detection
21- 24 F4.2 mag AV [0/1.35] Absorption in V band
26- 43 A18 --- FileName Name of the image with spectrum in
subdirectory sp
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 27-Apr-2015