J/A+A/706/A149 JHKs photometry of RCW 36 stars (do Brito do Vale+, 2026)
Substellar population of the young massive cluster RCW 36 in Vela.
do Brito do Vale A. R. G., Muzic K., Bouy H., Almendros-Abad V., Bayo A.,
Capela D., Scholz A., Bik A., Suarez G., Cieza L., Pena Ramirez K.,
Bertin E., Schoedel R.
<Astron. Astrophys. 706, A149 (2026)>
=2026A&A...706A.149D 2026A&A...706A.149D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Photometry, infrared
Keywords: brown dwarfs - stars: formation - stars: imaging - stars: low-mass -
stars: luminosity function, mass function - stars: pre-main sequence
Abstract:
The shape of the initial mass function (IMF) remains a fundamental yet
contentious topic in the study of stellar formation and evolution. It
is imperative to understand the potential variability of the IMF
across different young regions. This study examines the IMF within the
young massive cluster RCW 36 situated in the Vela Molecular Ridge,
comparable with the Orion Nebula Cluster in terms of stellar surface
density.
The primary objective of this research is to construct the most
comprehensive census of the stellar population in RCW 36 to date and
determine the first ever IMF and star to brown dwarf (BD) ratio for
the cluster.
We used state-of-the art observational techniques, drawing on new GLAO
observations conducted with HAWK-I/VLT in addition to archival data
from 2MASS, SOFI/NTT, and new kinematics from Gaia DR3. To enhance
photometric accuracy and source extraction, we employed DeNeb, an
advanced deep learning algorithm capable of removing the complex
filamentary nebula in our images. Statistical comparisons of
color-magnitude diagrams were performed between RCW 36 and a control
field, also obtained using HAWK-I under the same mode, to assign
membership weights for the sources in our field. Mass estimates to
individual sources were also derived through comparison with model
isochrones in order to determine the IMF using the membership weights.
We found a new distance of 954±40pc. We determined the IMF for RCW
,36 down to ∼0.03M☉, characterized by a broken power law
(dN/dM∝M-alpha with alpha=1.62±0.03
(0.20M☉-20M☉) and alpha=0.46±0.14
(0.03M☉-0.20M☉). We also determined the star-BD ratio to
be 2-5, in agreement with other Galactic clusters. Lastly, through a
study of the differences in the IMF within and outside 0.2pc and the
cumulative mass distributions for low-mass and intermediate to high-
mass sources, we also detected signs of possible mass segregation
within RCW 36, which should be primordial.
RCW 36 shares many characteristics with other young massive clusters,
such as a shallower than Salpeter high-mass slope and the possibility
of mass segregation. The flatter lower-mass regime of the IMF is
similar to most Galactic clusters. The star-BD ratio is also in line
with the observed values in other clusters, independent of their
inherent properties.
Description:
In this table, we list calibrated JHKs and HKs photometry from the
sources in our HAWK-I field.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 169 1735 Calibrated JHKs and HKs photometry from the
sources in our HAWK-I field
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID [1/1735] Source Identifier
6- 23 F18.14 deg RAdeg Right ascension (J2000)
25- 43 F19.15 deg DEdeg Declination (J2000)
45- 62 F18.15 mag Jmag ?=- J-band magnitude
64- 83 F20.18 mag e_Jmag ?=- Uncertainty on J-band magnitude
85-102 F18.15 mag Hmag H-band magnitude
104-123 F20.18 mag e_Hmag Uncertainty on H-band magnitude
125-142 F18.15 mag Ksmag Ks-band magnitude
144-163 F20.18 mag e_Ksmag Uncertainty on Ks-band magnitude
165-169 A5 --- Ref Reference for the photometry
(hawk, sofi or 2mass)
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Acknowledgements:
A. do Brito do Vale, fc47932(at)alunos.ciencias.ulisboa.pt
(End) Patricia Vannier [CDS] 12-Jan-2026