J/A+A/704/A170 USC free-floating planetary mass objects (Rodrigues+, 2025)
Disk fraction among free-floating planetary-mass objects in Upper Scorpius.
Rodrigues T., Bouy H., Raymond S.N., Martin E.L., Bertin E.M.,
Olivares J., Barrado D., Huelamo N., Tamura M., Miret Roig N.,
Galli P.A.B., Cuillandre J.-C.
<Astron. Astrophys. 704, A170 (2025)>
=2025A&A...704A.170R 2025A&A...704A.170R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; YSOs ; Photometry, infrared
Keywords: brown dwarfs - circumstellar matter - stars: formation -
stars: late-type - stars: low-mass - stars: statistics
Abstract:
Free-floating planetary-mass objects (FFPs) have been detected through
direct imaging within several young, nearby star-forming regions. The
properties of circumstellar disks around these objects may provide a
valuable probe into their origin, but is currently limited by the
small sizes of the sample explored. We aim to perform a statistical
study of the occurrence of circumstellar disks down to the
planetary-mass regime. We performed a systematic survey of disks among
the population identified in the 5-10Myr-old Upper Scorpius
association (USC), restricted to members outside the younger, embedded
Ophiuchus region and with estimated masses below 105MJup. We took
advantage of unWISE photometry to search for mid-infrared excesses in
the WISE (W1-W2) color. We implemented a Bayesian outlier detection
method that models the photospheric sequence and computes excess
probabilities for each object, enabling statistically sound estimation
of disk fractions. We explore disk fractions across an unprecedentedly
fine mass grid, reaching down to objects as low as ∼6MJup assuming
5Myr or ∼8MJup assuming 10Myr, thus extending the previous lower
boundary of disk fraction studies. Depending on the age, our sample
includes between 17 and 40 FFPs. We confirm that the disk fraction
steadily rises with decreasing mass and exceeds 30% near the
substellar-to-planetary mass boundary at ∼13MJup. We find hints of a
possible flattening in this trend around 25-45MJup, potentially
signaling a transition in the dominant formation processes. This
change of trend should be considered with caution and needs to be
confirmed with more sensitive observations. Our results are consistent
with the gradual dispersal of disks over time, as disk fractions in
Upper Scorpius appear systematically lower than those in younger
regions.
Description:
We performed a survey of disks among members in the Upper Scorpius
association. We took advantage of unWISE photometry to search for
disk-related mid-infrared excesses in the unWISE (W1-W2) color. We
implemented a Bayesian outlier detection method that models the
photospheric sequence and computes excess probabilities for each
object.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 133 503 Excess probabilities and unWISE W1/W2 photometry
of USC members
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See also:
J/A+A/667/A163 : Upper Scorpius and Ophiuchus members (Miret-Roig+, 2022)
Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID [1/3455] Member identification number from
Miret Roig et al. (2022A&A...667A.163M 2022A&A...667A.163M,
Cat. J/A+A/667/A163)
6- 15 F10.6 deg RAdeg Right ascension (ICRS) at Ep=2016.0
17- 26 F10.6 deg DEdeg Declination (ICRS) at Ep=2016.0
28- 34 F7.3 pc d Distance from Gaia DR3
36- 41 F6.3 pc e_d Uncertainty on distance
43- 51 F9.5 Mjup Mass5Myr Mass estimate assuming 5Myr from
Miret Roig et al. (2022, Cat. J/A+A/667/A163)
53- 61 F9.5 Mjup Mass10Myr Mass estimate assuming 10Myr from
Miret Roig et al. (2022, Cat. J/A+A/667/A163)
63- 71 F9.6 mag W1mag unWISE/W1 magnitude
73- 81 F9.6 mag e_W1mag Uncertainty on unWISE/W1 magnitude
83- 91 F9.6 mag W2mag unWISE/W2 magnitude
93-101 F9.6 mag e_W2mag Uncertainty on unWISE/W2 magnitude
103 I1 --- fWISE [0/1] Flag: possible contamination in unWISE
images (1 = flagged, 0 = clean)
105-111 F7.4 --- pexc5Myr ?=- Excess probability
(5Myr, keeping flagged sources)
113-118 F6.4 --- pexc10Myr ?=- Excess probability
(10Myr, keeping flagged sources)
120-126 F7.4 --- pexc5Myrw ?=- Excess probability
(5Myr, excluding flagged sources)
128-133 F6.4 --- pexc10Myrw ?=- Excess probability
(10Myr, excluding flagged sources)
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Acknowledgements:
Tommy Rodrigues, tommy.rodrigues(at)u-bordeaux.fr
(End) Patricia Vannier [CDS] 09-Oct-2025