J/A+A/687/A168 Solution CMD ofr nearby stars (Gallart+, 2024)
Chronology of our Galaxy from Gaia Colour-Magnitude Diagram-fitting (ChronoGal).
I. The formation and evolution of the thin disk from the Gaia Catalogue of
Nearby Stars.
Gallart C., Surot F., Cassisi S., Fernandez-Alvar E., Mirabal D.,
Rivero A., Ruiz-Lara T., Santos-Torres J., Aznar-Menargues G.,
Battaglia G., Queiroz A. B. A, Monelli M., Vasiliev E., Chiappini C.,
Helmi A., Hill V., Massari D., Thomas G. F.
<Astron. Astrophys. 687, A168 (2024)>
=2024A&A...687A.168G 2024A&A...687A.168G (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Photometry ; Optical ; Stars, ages ; Abundances, [Fe/H]
Keywords: Hertzsprung-Russell and C-M diagrams - Galaxy: disk -
Galaxy: evolution - solar neighborhood - Galaxy: stellar content
Abstract:
The study of the Milky Way is living a golden era thanks to the
enormous high-quality datasets delivered by Gaia, and space
asteroseismic and ground-based spectroscopic surveys. However, the
current major challenge to reconstructing the chronology of the Milky
Way is the difficulty to derive precise stellar ages for large samples
of stars. The colour-magnitude diagram (CMD) fitting technique
offers an alternative to individual age determinations to derive the
star formation history (SFH) of complex stellar populations.
Our aim is to obtain a detailed dynamically evolved SFH (deSFH) of the
solar neighbourhood, and the age and metallicity distributions that
result from it. We define deSFH as the amount of mass transformed into
stars, as a function of time and metallicity, in order to account for
the population of stars contained in a particular volume.
We present a new package to derive SFHs from CMD fitting tailored to
work with Gaia data, called CMDft.Gaia, and we use it to analyse the
CMD of the Gaia Catalogue of Nearby Stars (GCNS), which contains a
complete census of the (mostly thin disc) stars currently within
100pc of the Sun.
We present an unprecedentedly detailed view of the evolution of the
Milky Way disc at the solar radius. The bulk of star formation started
11-10.5Gyr ago at metallicity around solar, and continued with a
slightly decreasing metallicity trend until 6Gyr ago. Between 6 and
4Gyr ago, a notable break in the age-metallicity distribution is
observed, with three stellar populations with distinct metallicities
(sub-solar, solar, and super-solar), possibly indicating some dramatic
event in the life of our Galaxy. Star formation then resumed 4Gyr ago
with a somewhat bursty behaviour, metallicity near solar and average
star formation rate higher than in the period before 6Gyr ago. The
derived metallicity distribution closely matches precise spectroscopic
data, which also show stellar populations deviating from solar
metallicity. Interestingly, our results reveal the presence of
intermediate-age populations exhibiting both a metallicity typical of
the thick disc, approximately [M/H]≃-0.5, and super-solar
metallicity.
The many tests performed indicate that, with high-precision
photometric and distance data such as that provided by Gaia,
CMDft.Gaia is able to achieve a precision of ∼10% and an accuracy
better than 6% in the dating of stellar populations, even at old ages.
A comparison with independent spectroscopic metallicity information
shows that metallicity distributions are also determined with high
precision, without imposing any a priori metallicity information in
the fitting process. This opens the door to obtaining detailed and
robust information on the evolution of the stellar populations of the
Milky Way over cosmic time. As an example, we provide in this paper an
unprecedentedly detailed view of the age and metallicity distributions
of the stars within 100 pc of the Sun.
Description:
We deliver one file with the solution CMD obtained from the deSFH
derived from the synthetic mother CMD named q01b03_120M_MG5. The
file contains the (GBP-GRP) color, M_G magnitude, age and
metallicity of each synthetic star in the solution. The number of
stars in this solution CMD matches closely the number of stars in the
observed CMD inside the bundle. See the paper entitled above for
details.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 38 21254 Solution model CMD
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 7 F7.4 mag BP-RP Model BP-RP Gaia color
9- 15 F7.4 mag Gmag Model G Gaia magnitude
17- 23 F7.4 Gyr Age Model age value
25- 30 F6.4 --- Z Model metall mass fraction
32- 38 F7.4 --- [Fe/H] Model [Fe/H]
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Acknowledgements:
Carme Gallart, carme.gallart-at-iac.es
(End) C. Gallart [Inst. Astrofisica de Canarias], P. Vannier [CDS] 15-Mar-2024