J/A+A/706/A370 Nearby young moving groups IMF (Bertolotto-Stefanelli+, 2026)
The stellar initial mass function of nearby young moving groups.
Bertolotto-Stefanelli R., Downes J.J., Suarez G., Mateu C., Gagne J.,
Zuniga C.R.
<Astron. Astrophys. 706, A370 (2026)>
=2026A&A...706A.370B 2026A&A...706A.370B (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, nearby ; Associations, stellar ;
Radial velocities ; Stars, masses ; Optical
Keywords: open clusters and associations: general - solar neighborhood -
Galaxy: structure
Abstract:
The solar neighbourhood is populated by nearby (<200pc), young
(<100Myr) moving groups (NYMGs) of stars, whose origins are still
debated. A possible explanation is that they are remnants of
individual stellar clusters and associations, currently dispersing in
the Galactic disc.
We aim to derive the initial mass function (IMF) of a large sample of
NYMGs.
We developed and applied an algorithm that uses photometric and
astrometric data from Gaia DR3 to detect NYMGs as over-densities in a
kinematic space, whose members distribute along young isochrones. We
inferred individual masses from the photometry of both the detected
and the previously known candidates. We estimated the IMFs for 33
groups, 30 of them for the first time, in an average mass range
0.1<m/M☉<5, with some groups going as low as 0.02M☉ and as
high as 10M☉. We parameterized these IMFs using a log-normal
distribution for m<1M☉ and a power-law for m>1M☉.
We detected 4166 source candidate members of 44 known groups,
including 2545 new candidates. We recovered 44-54 percent of the
literature candidates and estimated a contamination rate from old
field stars of 16-24 percent. The candidates of the detected groups
distribute along young isochrones, suggesting that they are potential
members of NYMGs. Parameterizations of both the average of the 33 IMFs
based on our detections (mc=0.25±0.17M☉, sigmac=0.45±0.17,
and alpha=-2.26±0.09) and the one based on the known candidates from
the literature (mc=0.22±0.14M☉, sigmac=0.45±0.17, and
alpha=-2.45±0.06) are in agreement with the IMF parameterization of
the solar neighbourhood and young stellar associations.
Our parameterization of the average IMF, together with the
distribution of the detected group members along young isochrones,
provides strong evidence suggesting that the NYMGs are remnants of
individual stellar associations and clusters, and that there are no
systematic biases in our detection and in the literature in the mass
range 0.1<m/M☉<10.
Description:
The first table contains the astrometry, photometry and masses of
candidate members of young moving stellar groups of the solar
neighborhood computed and inferred based on Gaia DR3 astrometry and
photometry.The second table contains the general information and
statistics of the groups, including inferred parameters of their
IMFs. The construction of both tables is described in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
members.dat 276 7530 Candidate members of nearby young moving groups
table1.dat 323 44 General statistics of nearby young moving groups
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: members.dat
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Bytes Format Units Label Explanations
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1- 7 E7.6 --- rc Ratio of probability functions
(see section 3.4) (rc)
9- 13 F5.1 Myr Age [10/100] Age of the group according to the
MOCA database (age)
15- 24 F10.6 deg RAdeg Gaia DR3 right ascension (ICRS) at Ep=2016.0
(ra)
26- 35 F10.6 deg DEdeg Gaia DR3 declination (ICRS) at Ep=2016.0 (dec)
37- 43 F7.4 mas plx Gaia DR3 parallax (parallax)
45- 50 F6.4 mas e_plx Gaia DR3 parallax error (e_parallax)
52- 61 F10.6 mag GMAG Gaia DR3 G band magnitude corrected by
distance modulus using inverse of parallax
(MG)
63- 70 F8.6 mag e_GMAG propagated GMAG error (e_MG)
72- 80 F9.6 mag BP-RP Gaia DR3 BP-RP color (BR)
82- 89 F8.6 mag e_BP-RP Gaia DR3 BP-RP color propagated error (e_BR)
91-101 F11.6 pc X Galactic cartesian x-coordinate (pointing
towards galactic center) (X)
103-113 F11.6 pc Y Galactic cartesian y-coordinate (pointing
towards disc rotation) (Y)
115-125 F11.6 pc Z Galactic cartesian z-coordinate (Z)
127-136 F10.6 km/s VRLSRa Right ascension tangential velocity relative
to the Local Standard of Rest (vraLSR)
138-147 F10.6 km/s VRLSRd Declination tangential velocity relative to
the Local Standard of Rest (vdecLSR)
149-157 F9.6 pc e_X X propagated error (e_X)
159-166 F8.6 pc e_Y Y propagated error (e_Y)
168-175 F8.6 pc e_Z Z propagated error (e_Z)
177-184 F8.6 km/s e_VRLSRa VRLSRa propagated error (e_vraLSR)
186-193 F8.6 km/s e_VRLSRd VRLSRd propagated error (e_vdecLSR)
195-202 F8.6 Msun Mass Inferred mass assuming age of host group
(mass) (1)
204-212 F9.6 Msun e_Mass ? Error on the inferred mass. For stars with
rc > 0.1, mass_error = 0 (e_mass)
214-223 A10 --- MOCAaId Original group name within the MOCA database
(moca_aid)
225-243 I19 --- GaiaDR3 Gaia DR3 source ID (source_id)
245-276 A32 --- GroupId Name of the detected group in this work
(group_id)
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Note (1): Masses were only inferred for stars with rc>0.1, otherwise mass is
set to 0.
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- MOCAaId Original group name within the MOCA
database (moca_aid)
12- 43 A32 --- GroupId Name of the detected group in this work
(group_id)
45- 48 F4.1 Myr Age [3/93] Age of the group according to the
MOCA database (age_myr)
50- 51 I2 Myr AgeIso Age of the isochrone used to select stars
(ageisoselection_myr)
53- 57 F5.1 --- obsN [10/290] Number of candidate members from
MOCA database (observedN)
59- 63 F5.1 --- obsRVN [1/151] Number of candidate members from
MOCA database with RVs in Gaia (observedRVN)
65- 82 F18.14 pc Dmean Average heliocentric distance of the
candidate members of the group (meand)
84-102 F19.16 pc e_Dmean Standard deviation of distances of the
candidate members of the group (dstd)
104-106 I3 --- Ndet [41/800] Number of candidates detected in
this work (Ndetected)
108-110 I3 --- Ndet01 [24/442] Number of candidates detected in
this work with rc>0.1 (Ndetected01)
112-130 F19.17 --- Recov Recovery fraction relative to members from
literature (recovery)
132-150 F19.17 --- Recov01 Recovery fraction relative to members from
literature with rc>0.1 (recovery01)
152-169 F18.16 --- SimPurity Purity fraction relative to members from
literature (simulationPurity)
171-189 F19.17 --- SlitPurity Fraction relative to members from literature
with rc>0.1 (slitPurity)
191-209 F19.17 Msun Massmean Characteristic mass of log-normal
parametrization of IMF for m<1M☉
(meanMass)
211-229 F19.17 Msun e_Massmean Error on inferred Characteristic mass
(e_meanMass)
231-249 F19.17 --- stdImf Characteristic width of log-normal
parametrization of IMF for m<1M☉
(stdImf)
251-269 F19.17 --- e_stdImf Error on inferred Characteristic width
(e_stdImf)
271-289 F19.16 --- Slope Index of fitted power-law for IMF for
m>1M☉ (slope)
291-309 F19.17 --- e_Slope Error on index of fitted power-law for IMF
for m>1M☉ (e_slope)
311-316 F6.2 Msun Mass Total inferred mass of the detected group
(mass)
318-323 F6.2 Msun MassMOCA Total inferred mass of original group from
MOCA database (mocaMass)
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Acknowledgements:
Rafael Bertolotto-Stefanelli, rbertolotto(at)arizona.edu
(End) Patricia Vannier [CDS] 04-Jan-2026