Solar twins in Gaia DR3 GSP-Spec I. Building a large catalog of Solar twins with ages

TL;DR

This study builds a large catalog of Solar twins from Gaia DR3 GSP-Spec, deriving model-driven stellar parameters and isochrone ages with a rigorously characterized selection function. By selecting stars within ±$200\, K$ in $T_{\mathrm{eff}}$, ±$0.2$ dex in $\log g$, and ±$0.1$ dex in $[M/H]$ around solar values, and applying strict quality and photometric constraints, the authors assemble 6,594 Solar twins with ages inferred via Bayesian isochrone projection on PARSEC models. Mock catalogs reproduce the observed sample’s main properties, validating the age determinations (especially those based on $M_G$ and $M_{Ks}$) and enabling robust age–chemical-abundance analyses. The resulting age–[X/Fe] relations largely agree with previous high-precision studies, demonstrating the catalog’s power for Galactic archaeology while highlighting systematic limitations in $\log g$-based ages and Gaia DR3 GSP-Spec abundances for very young or weak lines.

Abstract

[Abbreviated] Context. Solar twins, stars whose stellar parameters (Teff, log g, and [M/H]) are very close to the Solar ones, offer a unique opportunity to investigate Galactic archaeology with very high accuracy and precision. However, most previous catalogs of Solar twins contain only a small number of objects (typically a few tens), and their selection functions are poorly characterized. Aims. We aim at building a large catalog of Solar twins from Gaia DR3 GSP-Spec, providing model-driven, rather than data-driven, stellar parameters including ages, together with a well-characterized selection function. Methods. Using stellar parameters from the Gaia DR3 GSP-Spec catalog, we selected Solar-twin candidates whose parameters lie within +- 200 K in Teff, +- 0.2 in log g, and +- 0.1 dex in [M/H] of the Solar values. Candidates unlikely to be genuine Solar twins were removed using Gaia flags and photometric constraints. We determined accurate ages for individual twins with a Bayesian isochrone-projection method, considering three combinations of parameters: Teff, [M/H], and either log g, M_G, or M_Ks. We also constructed a mock catalog to characterize the selection function. Results. Our final GSP-Spec Solar-twin catalog contains 6,594 stars. The mock catalog consisting of 75,588 artificial twins well reproduces the main characteristics of the observed catalog, especially for ages determined with M_G or M_Ks. To demonstrate the usefulness of our catalog, we compared chemical abundances [X/Fe] with age. We statistically confirmed the age--[X/Fe] relations for several species (e.g., Al, Si, Ca, and Y), demonstrating that trends previously identified in small but very high-precision samples persist in a much larger, independent sample. Conclusions. Our study bridges small high-precision Solar-twin samples and large data-driven ones, enabling demographic studies of Solar twins.

Figures (22)

• Figure 1: Some parameters of theoretical isochrones (top) and observed Solar-twin candidates (bottom). The horizontal axes in all the panels represent $T_{\mathrm{eff}}$, while the vertical axes represent some other parameters ($\log g$, $M_{G}$, $M_{K_{\mathrm{s}}}$, and $(J-K_{\mathrm{s}})_{0}$). Cyan dots in the upper panels show the isochrone grid points satisfying $-0.1<\mathrm{[M/H]}_{\mathrm{curr}}<+0.1\,\mathrm{dex}$. Blue dots in the upper panels show a subset of them having $T_{\mathrm{eff}}$ and $\log g$ between $\pm 200\,\mathrm{K}$ and $\pm 0.2$ around the Solar values, which is the selection criterion of our Solar-twin candidates in Sect. \ref{['ssec:gaiadata']} and is represented as a black dashed rectangle in the left panels. Black dashed trapezoids in the rest of the panels show the selection criteria for good Solar twins in Sect. \ref{['ssec:flag']}. Dots in the lower panels show the parameters of the $7{,}775$ observed Solar-twin candidates with good distances and 2MASS data. Orange dots in the lower panels show a subset of them that do not satisfy the selection criteria (i.e., outside the black trapezoids). Red crosses show the reference Solar values provided in Sect. \ref{['ssec:SolarAge']} and $(J-K_{\mathrm{s}})_{0}=0.40$Willmer2018. We note that several outliers of observed Solar-twin candidates fall outside the plotted range and are not shown in the figures.
• Figure 2: Recovered parameters in the resulting observed Solar-twin catalog. Each panel shows a scatter plot between the determined age $\tau$ and initial mass $M_{\mathrm{ini}}$, color-coded by the relative age error. Left, middle, and right panels show the results obtained when using $\log g$, $M_{G}$, and $M_{K_{\mathrm{s}}}$, respectively. as the third input parameter in addition to $\mathrm{[M/H]}_{\mathrm{curr}}$ and $T_{\mathrm{eff}}$.
• Figure 3: Recovered parameters in the mock catalog of Solar twins. We show only random $6{,}594$ mock stars, i.e., the same number of stars as in the observed Solar-twin catalog. All the panels are defined in the same way as in Fig. \ref{['fig:AgeMini']}.
• Figure 4: Comparison between the observed (blue) and mock (orange) Solar-twin catalogs in different age bins. Top, middle, and bottom panels show results for twins with the determined ages between $1\text{--}2$, $4\text{--}5$, and $7\text{--}8\,\mathrm{Gyr}$, respectively. Left, middle, and right panels correspond to ages determined using $\log g$, $M_{G}$, and $M_{K_{\mathrm{s}}}$, respectively, as the third input parameter, together with $\mathrm{[M/H]}_{\mathrm{curr}}$ and $T_{\mathrm{eff}}$. In each panel, the histograms show the probability density of the initial mass $M_{\mathrm{ini}}$ (i.e., the normalized number of twins per $M_{\mathrm{ini}}$ bin), while line plots show the median relative age errors in each $M_{\mathrm{ini}}$ bins.
• Figure 5: Comparison between the Solar-twin ages determined with $\log g$, $M_{G}$, and $M_{K_{\mathrm{s}}}$, color-coded with $T_{\mathrm{eff}}$.