J/MNRAS/499/2292 Brown dwarf population in NGC 2264 (Pearson+, 2020)
The brown dwarf population in the star-forming region NGC 2264.
Pearson S., Scholz A., Teixeira P.S., Muzic K., Eisloffel J.
<Mon. Not. R. Astron. Soc., 499, 2292-2302 (2020)>
=2020MNRAS.499.2292P 2020MNRAS.499.2292P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, brown dwarf ; Optical ; Infrared
Keywords: catalogues - surveys - brown dwarfs - stars: low-mass
Abstract:
The brown dwarf population in the canonical star-forming region
NGC 2264 is so far poorly explored. We present a deep,
multiwavelength, multiepoch survey of the star-forming cluster
NGC 2264, aimed to identify young brown dwarf candidates in this
region. Using criteria including optical/near-infrared (IR) colours,
variability, Spitzer mid-IR colour excess, extinction, and Gaia
parallax and proper motion (in order of relevance), we select 902
faint red sources with indicators of youth. Within this sample, we
identify 429 brown dwarf candidates based on their IR colours. The
brown dwarf candidates are estimated to span a mass range from 0.01 to
0.08M☉. We find rotation periods for 44 sources, 15 of which are
brown dwarf candidates, ranging from 3.6h to 6.5d. A subset of 38
brown dwarf candidates show high-level irregular variability
indicative of ongoing disc accretion, similar to the behaviour of
young stars.
Description:
The basis of this investigation are observations obtained with the
Victor Blanco 4-m telescope at the Cerro Tololo Interamerica
Observatory (CTIO) in Chile. We observed over six nights from 2010
January 18 to 23, as part of NOAO proposal 2009B-0090, using the
64-megapixel MOSAIC II camera. The field was selected to cover the
majority of NGC 2264. We observed in the Mosaic I-band filter (c6028),
which has a central wavelength of 805nm and a full width at
half-maximum (FWHM) of 150nm. A summary of the observations is given
in Table 1 of the article.
The I-band source catalogue was then cross referenced with a catalogue
of deep NIR J (1.25µm), H (1.65µm), and K (2.2µm) photometry
from the FLAMINGOS giant molecular cloud survey (Elston
1998SPIE.3354..404E 1998SPIE.3354..404E; Levine et al. 2006ApJ...646.1215L 2006ApJ...646.1215L, Cat.
J/ApJ/646/1215). The FLAMINGOS catalogue was chosen as it provided the
deepest available NIR photometry for the cluster. Bright sources will
typically become saturated in the MOSAIC-II I-band data well before
The FLAMINGOS JHK data. The spatial coverage of the FLAMINGOS data is
very similar to the MOSAIC-II data, with >95 per cent overlap.
We have used optical, NIR, and mid-IR photometry, time series data,
extinction maps, and, to some extent, Gaia kinematics to construct a
catalogue of 902 faint red sources with indicators of youth for NGC 2264.
Within this catalogue, we select 429 brown dwarf candidates
based on their IR colours.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 62 902 Catalogue summary table
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/646/1215 : Low-mass stars and brown dwarfs in NGC 2024 (Levine+, 2006)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000)
12- 19 F8.6 deg DEdeg Declination (J2000)
21- 25 F5.2 mag Imag I-band magnitude
27- 31 F5.2 mag Jmag J-band magnitude
33- 37 F5.2 mag Hmag ?=88.89 H-band magnitude
39- 44 F6.2 mag Kmag ?=100 K-band magnitude
46 A1 --- BDC Indicates if the source is a brown dwarf
candidate
48 A1 --- JHKSel Indicates if the source is in the JHK_Sel
sample (1)
50 A1 --- IKJHSel Indicates if the source is in the IKJH_Sel
sample (2)
52 A1 --- IJSel Indicates if the source is in the IJ_Sel
sample (3)
54 A1 --- VAR Indicates if the source is in the VAR
sample (4)
56 A1 --- HIGHVAR Indicates if the source is in the HIGHVAR
sample (5)
58 A1 --- DISCS Indicates if the source is in the DISCS
sample (6)
60 A1 --- KINEMATIC Indicates if the source is in the KINEMATIC
sample (7)
62 A1 --- HIGHEX Indicates if the source is in the HIGHEX
sample (8)
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Note (1): The JHK_Sel sample is composed of 273 faint red sources lying below
the reddening vector in the JH/HK diagram (see Figure 9 of the
article). These sources have colours consistent with substellar
objects and were selected as brown dwarf candidates.
Note (2): The IKJH_Sel sample is composed of 190 faint red sources lying above
the reddening vector in the IK/JH diagram (see Figure 9 of the
article). These sources have colours consistent with substellar
objects and were selected as brown dwarf candidates.
Note (3): The IJ_Sel sample is composed of 289 faint red sources that fell in
the expected region for substellar objects in the de-reddened I/I-J
colour-magnitude diagram (see Figure 10 of the article). These sources
were then selected as brown dwarf candidates.
Note (4): The VAR sample is composed of 467 variable sources (see Section 4.2
of the article for more details).
Note (5): Visual examination shows that a subsample of the VAR sample is highly
variable with amplitudes of 0.2-2mag. This sample of 83 sources
constitutes the HIGHVAR sample.
Note (6): The slope of the IR spectral energy distribution (SED) was used to
identify sources with an excess indicative of a disc and to
differentiate between the sources with thick discs and anaemic discs
(see Figure 7 of the article). In total, 199 sources show IR excess.
These sources constitute the DISCS sample.
Note (7): We attempted to use Gaia DR2 to determine low-mass candidates based
on their kinematics using the following selection criteria: parallax
between 1.3 and 1.5mas (719±50pc); proper motion consistent with
the locus of NGC 2264 (see Figure 6 of the article); and parallax
error less than 30 per cent. In total, 24 sources were found to
satisfy these criteria. These sources constitute the KINEMATIC sample.
Note (8): The HIGHEX sample is composed of 340 high extinction sources (having
AV>10). See section 4.5 for more details.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 18-Aug-2023