Searching for solar siblings in APOGEE and Gaia DR2 with N-body simulations. (2020)
Keywords :
Sun general - Galaxy: general - Galaxy: kinematics and dynamics - solar neighbourhood - galaxies: star clusters: general - galaxies: structure
Abstract:We make use of APOGEE and Gaia data to identify stars that are consistent with being born in the same association or star cluster as the Sun. We limit our analysis to stars that match solar abundances within their uncertainties, as they could have formed from the same giant molecular cloud (GMC) as the Sun. We constrain the range of orbital actions that solar siblings can have with a suite of simulations of solar birth clusters evolved in static and time-dependent tidal fields. The static components of each galaxy model are the bulge, disc, and halo, while the various time-dependent components include a bar, spiral arms, and GMCs. In galaxy models without GMCs, simulated solar siblings all have J_R_<122kpc.km/s,
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In order to firmly constrain whether or not a given star is a
potential sibling of the Sun or not, we require knowledge of the
star's metallicity, key elemental abundances, and the star's 6D
spatial and kinematic properties. Cross-matching the APOGEE (Majewski
et al. 2017AJ....154...94M, Cat. III/284) and Gaia DR2 (Gaia
Collaboration 2018A&A...616A...1G, Cat. I/345) catalogues provides a
data set of stars with the necessary information. Comparing the
measured actions to those of the Sun and simulations of star clusters
on Sun-like orbits will help further constrain whether stars with
similar abundances to the Sun could potentially have formed in the
same birth cluster. Ideally one would also require a star's age to be
4.65Gyr within uncertainty in order to be considered a solar sibling.
Unfortunately the mean uncertainty of APOGEE star ages is ~2Gyr
(Mackereth et al. 2019MNRAS.489..176M, Cat. J/MNRAS/489/176), which is
too high to strongly argue that a given star was born at the same time
as the Sun or not.
Taking into consideration the entire suite of simulations, we find
that solar siblings are most likely to have J_R_<122kpc.km/s,
353<L_z_<2110kpc.km/s, and J_z_<0.8kpc.km/s.
In total we find 296 stars in APOGEE with solar-like abundances that
also have actions that overlap with our suite of simulations. The list
of candidates can be broken up into primary and secondary lists based
on whether or not the model stars that the candidates have similar
actions to were evolved in a time-dependent field with no GMCs or a
time-dependent field with GMCs. Based on these criteria, we find our
list of solar sibling candidates consists of 104 primary candidates
and 192 secondary candidates.
- III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
- I/345 : Gaia DR2 (Gaia Collaboration, 2018)
- II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
