分类： 天文学 >> 天文学 提交时间： 2023-02-19
G. Contursi
P. de Laverny
A. Recio-Blanco
E. Spitoni
P. A. Palicio
E. Poggio
V. Grisoni
G. Cescutti
F. Matteucci
L. Spina
M. A. Alvarez
G. Kordopatis
C. Ordenovic
I. Oreshina-Slezak
H. Zhao
摘要： The recent Gaia Third Data Release contains a homogeneous analysis of millions of high-quality Radial Velocity Spectrometer (RVS) stellar spectra by the GSP-Spec module. This led to the estimation of millions of individual chemical abundances and allows us to chemically map the Milky Way. Among the published GSP-Spec abundances, three heavy-elements produced by neutron-captures in stellar interiors can be found: Ce, Zr and Nd. We use a sample of about 30,000 LTE Ce abundances, selected after applying different combinations of GSP-Spec flags. Thanks to the Gaia DR3 astrometric data and radial velocities, we explore the cerium content in the Milky Way and, in particular, in its halo and disc components. The high quality of the Ce GSP-Spec abundances is quantified thanks to literature comparisons. We found a rather flat [Ce/Fe] versus [M/H] trend. We also found a flat radial gradient in the disc derived from field stars and, independently, from about 50 open clusters, in agreement with previous studies. The [Ce/Fe] vertical gradient has also been estimated. We also report an increasing [Ce/Ca] vs [Ca/H] in the disc, illustrating the late contribution of AGB with respect to SN II. Our cerium abundances in the disc, including the young massive population, are well reproduced by a new three-infall chemical evolution model. Among the halo population, the M 4 globular cluster is found to be enriched in cerium. Moreover, eleven stars with cerium abundances belonging to the Thamnos, Helmi Stream and Gaia-Sausage-Enceladus accreted systems were identified from chemo-dynamical diagnostics. We found that the Helmi Stream could be slightly underabundant in cerium, compared to the two other systems. This work illustrates the high quality of the GSP-Spec chemical abundances, that significantly contributes to unveil the heavy elements evolution history of the Milky Way.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
H. Zhao
M. Schultheis
T. Zwitter
C. A. L. Bailer-Jones
P. Panuzzo
P. Sartoretti
G. M. Seabroke
A. Recio-Blanco
P. de Laverny
G. Kordopatis
O. L. Creevey
T. E. Dharmawardena
Y. Frémat
R. Sordo
R. Drimmel
D. J. Marshall
P. A. Palicio
G. Contursi
M. A. Álvarez
S. Baker
摘要： Studies of the correlation between different diffuse interstellar bands (DIBs) are important for exploring their origins. However, the Gaia-RVS spectral window between 846 and 870 nm contains few DIBs, the strong DIB at 862 nm being the only convincingly confirmed one. Here we attempt to confirm the existence of a broad DIB around 864.8 nm and estimate its characteristics using the stacked Gaia-RVS spectra of a large number of stars. We study the correlations between the two DIBs at 862 nm and 864.8 nm, as well as the interstellar extinction. We obtained spectra of the interstellar medium absorption by subtracting the stellar components using templates constructed from real spectra at high Galactic latitudes with low extinctions. We then stacked the ISM spectra in Galactic coordinates, pixelized by the HEALPix scheme, to measure the DIBs. The stacked spectrum is modeled by the profiles of the two DIBs, Gaussian for $\lambda$862 and Lorentzian for $\lambda$864.8, and a linear continuum. We obtain 8458 stacked spectra in total, of which 1103 (13%) have reliable fitting results after applying numerous conservative filters. This work is the first of its kind to fit and measure $\lambda$862 and $\lambda$864.8 simultaneously in cool-star spectra. We find that the EWs and CDs of the two DIBs are well correlated with each other. The full width at half maximum (FWHM) of $\lambda$864.8 is estimated as $1.62 \pm 0.33$ nm which compares to $0.55 \pm 0.06$ nm for $\lambda$862. We also measure the vacuum rest-frame wavelength of $\lambda$864.8 to be $\lambda_0 = 864.53 \pm 0.14$ nm, smaller than previous estimates. We find a solid confirmation of the existence of the DIB around 864.8 nm based on an exploration of its correlation with $\lambda$862 and estimation of its FWHM. $\lambda$862 correlates better with E(BP-RP) than $\lambda$864.8.
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