J/A+A/701/A147 Substellar population in Corona Australis (Muzic+, 2025)
The substellar population in Corona Australis.
Muzic K., Almendros-Abad V., Baptista A., Scholz A., Capela D., Pearson S.,
Damian, B., doBrito-doVale A., Rom T., Jayawardhana R.
<Astron. Astrophys. 701, A147 (2025)>
=2025A&A...701A.147M 2025A&A...701A.147M (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region ; Populations, stellar ; Positional data ;
Optical
Keywords: brown dwarfs - stars: low-mass -
stars: luminosity function, mass function -
open clusters and associations: individual: Corona Asutralis
Abstract:
Measurements of internal dynamics of young clusters and star-forming
regions are crucial to fully understand the process of their
formation. A basic prerequisite for this is a well-established and
robust list of probable members.
The substellar initial mass function (IMF) and the formation
mechanisms of brown dwarfs (BDs) remain key open questions in star
formation theory. Detailed census and characterization of the IMF in a
large number of star-forming regions are essential for constraining
these processes.
We identify and spectroscopically confirm very low-mass members of the
Corona Australis (CrA) star-forming region to refine its substellar
census, determine its low-mass IMF, and compare it to other clusters.
Using deep I-band photometry from SuprimeCam/Subaru and data from
the VISTA Hemisphere Survey (VHS), we identified low-mass BD
candidates in CrA. We subsequently conducted near-infrared
spectroscopic follow-up of 172 of these candidates with KMOS/VLT, and
also obtained optical spectra for eight kinematic candidate members
identified via $Gaia$ data using FLOYDS/LCO.
The kinematic candidates observed with optical spectroscopy are
confirmed as low-mass stellar members with spectral types M1 to M5. In
contrast, all 173 BD candidates observed with KMOS are identified as
contaminants. Although the follow-up yielded no new substellar
members, it places strong constraints on the number of undetected
substellar objects in the region. Combined with literature data, this
enables us to derive the substellar IMF, which is consistent with a
single power-law slope of alpha=0.95±0.06 in the range
0.01-1M☉ or alpha=0.33±0.19 in the range 0.01-0.1M☉. The
star-to-BD ratio in CrA is ∼2. We also provide updated IMFs and
star-to-BD ratios for Lupus 3 and Cha I from the SONYC survey,
reflecting revised distances from Gaia. Finally, we estimate surface
densities and median FUV fluxes for six star-forming regions and
clusters to characterize their environments and compare their
substellar populations as a function of environmental properties.
The IMF and star-to-BD ratio show no clear dependence on stellar density or
ionizing flux from the massive stars. A combined effect - where one factor
enhances and the other suppresses BD formation - also appears unlikely.
Description:
In this table, we list the positions of all objects observed in the
spectroscopic follow-up with KMOS. For the first eight objects, which
exhibit M-dwarf spectral features, we also provide their IDs, spectral
types, and extinction values. For the remaining objects, whose spectra
are not consistent with late-type classification, only the positions
are given.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 35 173 Positions of all objects observed in the
spectroscopic follow-up with KMOS
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Identifier (only for the 8 first sources)
5- 6 I2 h RAh Right Ascension (J2000)
8- 9 I2 min RAm Right Ascension (J2000)
11- 15 F5.2 s RAs Right Ascension (J2000)
17 A1 --- DE- Declination sign (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 27 F4.1 arcsec DEs Declination (J2000)
29- 30 A2 --- SpType NIR spectral type (only for the 8 first sources)
32- 35 F4.1 --- Av ? Extinction (only for the 8 first sources)
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Acknowledgements:
Koraljka Muzic, koralja(at)gmail.com
(End) Patricia Vannier [CDS] 29-Jul-2025