The Gaia–ESO Survey: Carbon Abundance in the Galactic Thin and Thick Disks^*

Abstract

This paper focuses on carbon that is one of the most abundant elements in the Universe and is of high importance in the field of nucleosynthesis and galactic and stellar evolution. Even nowadays, the origin of carbon and the relative importance of massive and low-to intermediate-mass stars in producing it is still a matter of debate. In this paper we aim at better understanding the origin of carbon by studying the trends of [C/H], [C/Fe],and [C/Mg] versus [Fe/H], and [Mg/H] for 2133 FGK dwarf stars from the fifth Gaia-ESO Survey internal data release (GES iDR5). The availability of accurate parallaxes and proper motions from Gaia DR2 and radial velocities from GES iDR5 allows us to compute Galactic velocities, orbits and absolute magnitudes and, for 1751 stars, ages via a Bayesian approach. Three different selection methodologies have been adopted to discriminate between thin and thick disk stars. In all the cases, the two stellar groups show different abundance ratios, [C/H], [C/Fe], and [C/Mg], and span different age intervals, with the thick disk stars being, on average, older than those in the thin disk. The behaviours of [C/H], [C/Fe], and [C/Mg] versus [Fe/H], [Mg/H], and age all suggest that C is primarily produced in massive stars like Mg. The increase of [C/Mg] for young thin disk Corresponding author: Mariagrazia Franchini Mariagrazia.franchini@inaf.it * Based on observations collected with the FLAMES instrument at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia-ESO Large Public Spectroscopic Survey (188.B-3002, 193.B-0936). Franchini et al.stars indicates a contribution from low-mass stars or the increased C production from massive stars at high metallicities due to the enhanced mass loss. The analysis of the orbital parameters R med and |Z max | support an "inside-out" and "upside-down" formation scenario for the disks of Milky Way.

Light Elements in the Universe

“…Despite the numerous works dedicated to these elements, their origin is still debated and not fully clarified (see also Kobayashi et al, 2020). Large spectroscopic surveys, combined with state-of-the-art chemical evolution models and stellar yields, allow us to take a step forward in understanding the origin of these elements (see, e.g., Magrini et al, 2018;Hayes et al, 2018;Romano et al, 2019;Griffith et al, 2019;Franchini et al, 2020).…”

“…Recent constraints of the origin of C from chemical evolution are presented Franchini et al (2020), who, thanks to a sample of F-G-K stars from the GES DR5, complemented with Gaia DR2 astrometry investigated the behaviors of [C/H], [C/Fe], and [C/ Mg] vs. [Fe/H], [Mg/H], and age. The detected trends pose important constraints to the origin of C, suggesting that it is primarily produced in massive stars.…”

A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

“…We find that the [X/Fe] ratios of most elements are close to solar as expected for a star with this metallicity, whereas [O/Fe] and [C/Fe] are slightly subsolar, since these ratios tend to slightly decrease above solar metallicity (e.g. Bertran de Lis et al 2015;Franchini et al 2020). Moreover, we used the chemical abundances of some elements to derive ages through the so-called chemical clocks (i.e.…”

“…It is remarkable to note just how sun-like HD 110113 is, with a radius, T eff and log g all within 1σ uncertainties of solar values, with the exception of its slightly higher metallicity ([Fe/H] = 0.14 ± 0.02), and correspondingly lower C & O (see Table 2; e.g. Bertran de Lis et al 2015;Franchini et al 2020). We speculate that the higher metallicity may explain why HD 110113 was able to form close-in mini-Neptunes (Mulders et al 2016;Bitsch & Battistini 2020), which do not exist in our Solar system.…”

The homogeneous characterisation of Ariel host stars

“…In the wavelength range covered by our spectra, there are two C I lines at 5052.144 Åand 6587.610 Åin the Gaia-ESO line-list [ 58 ] classified with high-quality flags, and one line at 5380.325 Å, with a lower quality flag, which can be used for C abundance determination. All three lines are discussed in [ 8 ] and the effects of 3D model atmosphere and of NLTE are negligible, as also discussed in [ 52 ]. We used them to derive carbon abundance in about 120 spectra of our sample with FAMA, fixing the stellar parameters to the SWEET-Cat ones, as done for the other elements.…”