J/MNRAS/486/1718 System IMF of 25 Ori (Suarez+, 2019)
System initial mass function of the 25 Ori Group from planetary-mass objects
to intermediate/high-mass stars.
Suarez G., Downes J.J., Roman-Zuniga C., Cervino M., Briceno C.,
Petr-Gotzens M.G., Viva K.
<Mon. Not. R. Astron. Soc. 486, 1718-1740 (2019)>
=2019MNRAS.486.1718S 2019MNRAS.486.1718S (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, pre-main sequence ;
Photometry, infrared
Keywords: brown dwarf - stars: formation - stars: low-mass -
stars: luminosity function, mass function - stars: pre-main sequence -
open clusters and associations: individual: 25 Orionis
Abstract:
The stellar initial mass function (IMF) is an essential input for many
astrophysical studies but only in a few cases has it been determined
over the whole cluster mass range, limiting the conclusions about its
nature. The 25 Orionis group (25 Ori) is an excellent laboratory for
investigating the IMF across the entire mass range of the population,
from planetary-mass objects to intermediate/high-mass stars. We
combine new deep optical photometry with optical and near-infrared
data from the literature to select 1687 member candidates covering a
1.1° radius area in 25 Ori. With this sample we derived the 25 Ori
system IMF from 0.012 to 13.1M☉. This system IMF is well
described by a two-segment power law with {GAMMA}=-0.74±0.04 for
m<0.4M☉ and {GAMMA}=1.50±0.11 for m≥0.4M☉. It is also
well described over the whole mass range by a tapered power-law
function with {GAMMA}=1.10±0.09, mp=0.31±0.03 and
β=2.11±0.09. The best lognormal representation of the system
IMF has mc=0.31±0.04 and σ=0.46±0.05 for m<1M☉. This
system IMF does not present significant variations with the radii. We
compared the resultant system IMF as well as the brown dwarf/star
ratio of 0.16±0.03 that we estimated for 25 Ori with that of other
stellar regions with diverse conditions and found no significant
discrepancies. These results support the idea that general
star-formation mechanisms are probably not strongly dependent on
environmental conditions. We found that the substellar and stellar
objects in 25 Ori do not have any preferential spatial distributions
and confirmed that 25 Ori is a gravitationally unbound stellar
association.
Description:
The list of photometric member candidates used in this study is based
on several optical and NIR catalogues covering an area of 1.1 deg
radius in 25 Ori. The list contains 1687 candidates and is complete
from 0.012 to 13.1M☉ (Ic=5.1-23.3mag).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 129 1687 Photometric member candidates
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See also:
J/ApJ/661/1119 : Spectroscopy in the 25 Ori group (Briceno+, 2007)
J/MNRAS/444/1793 : 25 Ori group low-mass stars (Downes+, 2014)
J/MNRAS/450/3490 : 15 new brown dwarfs in Orion OB1a/25 Ori group
(Downes+, 2015)
J/AJ/154/14 : Low-mass stars in 25 Ori group and Orion OB1a (Suarez+ 2017)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- ID Internal ID of the member candidates
(25Ori_NNNN)
13- 21 F9.6 deg RAdeg Right Ascension (J2000)
25- 32 F8.6 deg DEdeg Declination (J2000)
35- 40 F6.3 mag Icmag Cousins I magnitude
45- 49 F5.3 mag e_Icmag Uncertainty of the I magnitude
52- 57 F6.3 mag Jmag Johnson J magnitude
62- 66 F5.3 mag e_Jmag ? Uncertainty of the J magnitude
69- 74 F6.3 mag Hmag Johnson H-band magnitude
77- 83 F7.3 mag e_Hmag ? Uncertainty of the H magnitude
86- 91 F6.3 mag Kmag Johnson K-band magnitude
96-100 F5.3 mag e_Kmag ? Uncertainty of the K magnitude
104-112 A9 --- r_Icmag Source of optical photometry
116-120 A5 --- r_JHK Source of NIR photometry
129 A1 --- Ref Reference to previous studies (1)
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Note (1): Reference to previous studies as follows:
a = Briceno et al. (2005AJ....129..907B 2005AJ....129..907B); spectroscopically confirmed members
b = Hernandez et al. (2005AJ....129..856H 2005AJ....129..856H); member candidates using kinematic
and photometric data
c = Kharchenko et al. (2005A&A...440..403K 2005A&A...440..403K); highly probable candidates
d = Kharchenko et al. (2005A&A...440..403K 2005A&A...440..403K); low-probability candidates
e = Briceno et al. (2007ApJ...661.1119B 2007ApJ...661.1119B); spectroscopically confirmed members
f = Hernandez et al. (2007ApJ...671.1784H 2007ApJ...671.1784H); member candidates using infrared
and optical photometric data
g = Downes et al. (2014MNRAS.444.1793D 2014MNRAS.444.1793D); spectroscopically confirmed members
h = Downes et al. (2014MNRAS.444.1793D 2014MNRAS.444.1793D); photometric member candidates using
optical and NIR data
i = Downes et al. (2015MNRAS.450.3490D 2015MNRAS.450.3490D); spectroscopically confirmed members
j = Downes et al. (2015MNRAS.450.3490D 2015MNRAS.450.3490D); sources rejected as members
k = Suarez et al. (2017AJ....154...14S 2017AJ....154...14S); spectroscopically confirmed members
l = Suarez et al. (2017AJ....154...14S 2017AJ....154...14S); sources rejected as members
m = Kounkel et al. (2018AJ....156...84K 2018AJ....156...84K); highly probable members using
kinematic data
n = Kounkel et al. (2018AJ....156...84K 2018AJ....156...84K); candidates from Cottle et al.
(2018ApJS..236...27C 2018ApJS..236...27C) rejected as members
o = Briceno et al. (2019AJ....157...85B 2019AJ....157...85B); spectroscopically confirmed members
p = This work
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Acknowledgements:
Genaro Suarez, gsuarez(at)astro.unam.mx
(End) Genaro Suarez [Inst. Astron., UNAM], Patricia Vannier [CDS] 23-May-2019