The MAGIC project – III. Radial and azimuthal Galactic abundance gradients using classical Cepheids

Kovtyukh, V. V.; Lemasle, B.; Bono, G.; Усенко, И. А.; Silva, R. da; Kniazev, A. Y.; Grebel, Eva K.; Андронов, И. Л.; Shakun, L.; Chinarova, L. L.

doi:10.1093/mnras/stab3530

Cited by 17 publications

(16 citation statements)

References 72 publications

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“…5.1 in mind, the metallicity excursion barely exceeds 0.4 dex within a given spiral arm, and there are some hints of a metallicity trend with the Galactocentric azimuth (but the range of Galactocentric azimuths covered is relatively small), possibly increasing toward the outer disk. Such results are in line with the conclusions drawn by Kovtyukh et al (2022). Excel-lent precision and accuracy are required since model predictions indicate that the expected effects are modest.…”

Section: The Azimuthal Gradient Of Ironsupporting

confidence: 87%

Tracing the Milky Way warp and spiral arms with classical Cepheids

Lemasle

Lala

Kovtyukh

et al. 2022

A&A

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Context. Mapping the Galactic spiral structure is a difficult task since the Sun is located in the Galactic plane and because of dust extinction. For these reasons, molecular masers in radio wavelengths have been used with great success to trace the Milky Way spiral arms. Recently, Gaia parallaxes have helped in investigating the spiral structure in the Solar extended neighborhood. Aims. In this paper, we propose to determine the location of the spiral arms using Cepheids since they are bright, young supergiants with accurate distances (they are the first ladder of the extragalactic distance scale). They can be observed at very large distances; therefore, we need to take the Galactic warp into account. Methods. Thanks to updated mid-infrared photometry and to the most complete catalog of Galactic Cepheids, we derived the parameters of the warp using a robust regression method. Using a clustering algorithm, we identified groups of Cepheids after having corrected their Galactocentric distances from the (small) effects of the warp. Results. We derived new parameters for the Galactic warp, and we show that the warp cannot be responsible for the increased dispersion of abundance gradients in the outer disk reported in previous studies. We show that Cepheids can be used to trace spiral arms, even at large distances from the Sun. The groups we identify are consistent with previous studies explicitly deriving the position of spiral arms using young tracers (masers, OB(A) stars) or mapping overdensities of upper main-sequence stars in the Solar neighborhood thanks to Gaia data.

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Section: The Azimuthal Gradient Of Ironsupporting

confidence: 87%

Tracing the Milky Way warp and spiral arms with classical Cepheids

Lemasle

Lala

Kovtyukh

et al. 2022

A&A

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“…The different metric of azimuthal dependence as well as the different radial range observed could lead to the discrepancy. Our results also indicate much smaller azimuthal scatter than that observed in the MW by Kovtyukh et al (2022). Measuring cepheids at R = 7 − 9 kpc Kovtyukh et al (2022) find [Fe/H] varies by up to 0.2 kpc, much larger than our measured 0.05 dex scatter.…”

Section: Discussioncontrasting

confidence: 46%

3D elemental abundances of stars at formation across the histories of Milky Way-mass galaxies in the FIRE simulations

Bellardini,

Wetzel,

Loebman

et al. 2022

Preprint

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We characterize the 3-D spatial variations of [Fe/H], [Mg/H], and [Mg/Fe] in stars at the time of their formation, across 11 simulated Milky Way (MW)-and M31-mass galaxies in the FIRE-2 simulations, to inform initial conditions for chemical tagging. The overall scatter in [Fe/H] within a galaxy decreased with time until ≈ 7 Gyr ago, after which it increased to today: this arises from a competition between a reduction of azimuthal scatter and a steepening of the radial gradient in abundance over time. The radial gradient is generally negative, and it steepened over time from an initially flat gradient 12 Gyr ago. The strength of the present-day abundance gradient does not correlate with when the disk 'settled'; instead, it best correlates with the radial velocity dispersion within the galaxy. The strength of azimuthal variation is nearly independent of radius, and the 360 degree scatter decreased over time, from 0.17 dex at t lb = 11.6 Gyr to ∼ 0.04 dex at present day. Consequently, stars at t lb 8 Gyr formed in a disk with primarily azimuthal scatter in abundances. All stars formed in a vertically homogeneous disk, ∆[Fe/H]≤ 0.02 dex within 1 kpc of the galactic midplane, with the exception of the young stars in the inner ≈ 4 kpc at z ∼ 0. These results generally agree with our previous analysis of gas-phase elemental abundances, which reinforces the importance of cosmological disk evolution and azimuthal scatter in the context of stellar chemical tagging. We provide analytic fits to our results for use in chemical-tagging analyses.

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“…Balser et al (2011) analysed the oxygen distribution of HII regions in the Galactic disc, divided their sample into three Galactic azimuth bins, and found that the corresponding radial gradients were significantly different. Chemical inhomogeneities in iron and oxygen were also found in Cepheids (Pedicelli et al 2009;Genovali et al 2014;Kovtyukh et al 2022). Large metallicity variations were also found in the interstellar medium (De Cia et al 2021).…”

Section: Introductionmentioning

confidence: 91%

The chemical signature of the Galactic spiral arms revealed by Gaia DR3

Poggio

Recio–Blanco

Palicio

et al. 2022

A&A

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Taking advantage of the recent Gaia Data Release 3 (DR3), we mapped chemical inhomogeneities in the Milky Way's disc out to a distance of ∼ 4 kpc from the Sun, using different samples of bright giant stars. The samples were selected using effective temperatures and surface gravities from the GSP-Spec module, and they are expected to trace stellar populations of a different typical age. The cool (old) giants exhibit a relatively smooth radial metallicity gradient with an azimuthal dependence. Binning in Galactic azimuth ϕ, the slope gradually varies from d[M/H]/dR ∼ −0.054 dex kpc −1 at ϕ ∼ −20 • to ∼ −0.036 dex kpc −1 at ϕ ∼ 20 • . On the other hand, the relatively hotter (and younger) stars present remarkable inhomogeneities, which are apparent as three (possibly four) metal-rich elongated features in correspondence with the spiral arms' locations in the Galactic disc. When projected onto the Galactic radius, those features manifest themselves as statistically significant bumps on top of the observed radial metallicity gradients with amplitudes up to ∼ 0.05−0.1 dex, making the assumption of a linear radial decrease not applicable for this sample. The strong correlation between the spiral structure of the Galaxy and the observed chemical pattern in the young sample indicates that the spiral arms might be at the origin of the detected chemical inhomogeneities. In this scenario, the spiral arms would leave a strong signature in the younger stars which progressively disappears when cooler (and older) giants are considered.

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The MAGIC project – III. Radial and azimuthal Galactic abundance gradients using classical Cepheids

Cited by 17 publications

References 72 publications

Tracing the Milky Way warp and spiral arms with classical Cepheids

Tracing the Milky Way warp and spiral arms with classical Cepheids

3D elemental abundances of stars at formation across the histories of Milky Way-mass galaxies in the FIRE simulations

The chemical signature of the Galactic spiral arms revealed by Gaia DR3

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