Chempy: A flexible chemical evolution model for abundance fitting

Rybizki, Jan; Just, A.; Rix, Hans─Walter

doi:10.1051/0004-6361/201730522

Cited by 68 publications

(101 citation statements)

References 101 publications

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“…All three CCSN yield models underpredict Mg production relative to O and Si, as found previously by S16 and Rybizki et al (2017). If the predicted Mg yields were boosted by a factor of ∼ 1.5 − 2, then the Chempy CCSN yield models would bracket or be close to our empirical inferences for most elements, and the S16 yields would be in reasonable agreement for most elements.…”

Section: Discussionsupporting

confidence: 84%

“…Our results in the lower panel of Figure 17 can be compared qualitatively to those in Figure 14 of Rybizki et al (2017) and Figure 24 of S16. The former compares the predictions of the full Chempy chemical evolution models, including SNIa and AGB contributions, to proto-solar abundances.…”

Section: Comparison To Theoretical Yieldssupporting

confidence: 54%

“…This contrasts with the theoretical yield models, which predict that CCSN production of Na is much higher than either SNIa or AGB production (e.g., AWSJ17; Rybizki et al 2017).…”

Section: Light-z Elementsmentioning

confidence: 61%

“…Comparisons are given for both Chempy yield sets as well as the W18 yields from S16. For values above/below 1, the model over/under predicts our empirically inferred CCSN yield, relative to that of Mg. Figure 17 presents a summary comparison between our inferences from the 2-process model fits at solar abundances ([Mg/H] = [Fe/Mg] = 0) and the yield predictions of the default and alternative Chempy models (Rybizki et al 2017) and S16 CCSN models. For most elements the inferred core collapse fraction (f cc ) is bracketed by or reasonably close to the Chempy model predictions.…”

Section: Discussionmentioning

confidence: 99%

“…GALAH measures K from the K I 7699Å line, which is susceptible to interstellar absorption (B19). Many theoretical yield models underpredict observed K abundances by a large factor (e.g., AWSJ17; Rybizki et al 2017; but see Sukhbold et al 2016). Figure 4 shows that improvements in K abundance measurements are needed before we can draw robust conclusions about its nucleosynthetic origin.…”

Section: Comparison To Apogeementioning

confidence: 99%

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Abundance Ratios in GALAH DR2 and Their Implications for Nucleosynthesis

Griffith

Johnson

Weinberg

2019

ApJ

107

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Using a sample of 70 924 stars from the second data release of the GALAH optical spectroscopic survey, we construct median sequences of [X/Mg] vs. [Mg/H] for 21 elements, separating the highα/"low-Ia" and low-α/"high-Ia" stellar populations through cuts in [Mg/Fe]. Previous work with the near-IR APOGEE survey has shown that such sequences are nearly independent of location in the Galactic disk, implying that they are determined by stellar nucleosynthesis yields with little sensitivity to other chemical evolution aspects. The separation between the two [X/Mg] sequences indicates the relative importance of prompt and delayed enrichment mechanisms, while the sequences' slopes indicate metallicity dependence of the yields. GALAH and APOGEE measurements agree for some of their common elements, but differ in sequence separation or metallicity trends for others. GALAH offers access to nine new elements. We infer that about 75% of solar C comes from core collapse supernovae and 25% from delayed mechanisms. We find core collapse fractions of 60−80% for the Fe-peak elements Sc, Ti, Cu, and Zn, with strong metallicity dependence of the core collapse Cu yield. For the neutron capture elements Y, Ba, and La, we infer large delayed contributions with non-monotonic metallicity dependence. The separation of the [Eu/Mg] sequences implies that at least ∼ 30% of Eu enrichment is delayed with respect to star formation. We compare our results to predictions of several supernova and AGB yield models; C, Na, K, Mn, and Ca all show discrepancies with models that could make them useful diagnostics of nucleosynthesis physics.

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Section: Discussionsupporting

confidence: 84%

Section: Comparison To Theoretical Yieldssupporting

confidence: 54%

“…This contrasts with the theoretical yield models, which predict that CCSN production of Na is much higher than either SNIa or AGB production (e.g., AWSJ17; Rybizki et al 2017).…”

Section: Light-z Elementsmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Comparison To Apogeementioning

confidence: 99%

See 3 more Smart Citations

Abundance Ratios in GALAH DR2 and Their Implications for Nucleosynthesis

Griffith

Johnson

Weinberg

2019

ApJ

107

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Local disc model in view of Gaia DR1 and RAVE data

Sysoliatina

Just

Koutsouridou

et al. 2018

A&A

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Aims. We test the performance of the semi-analytic self-consistent Just-Jahreiß disc model (JJ model) with the astrometric data from the Tycho-Gaia Astrometric Solution (TGAS) sub-catalogue of the first Gaia data release (Gaia DR1), as well as the radial velocities from the fifth data release of the Radial Velocity Experiment survey (RAVE DR5). Methods. We used a sample of 19,746 thin-disc stars from the TGAS×RAVE cross-match selected in a local solar cylinder of 300 pc radius and 1 kpc height below the Galactic plane. Based on the JJ model, we simulated this sample via the forward modelling technique. First, we converted the predicted vertical density laws of the thin-disc populations into a mock sample. For this we used of the Modules and Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST), a star formation rate (SFR) that decreased after a peak at 10 Gyr ago, and a three-slope broken power-law initial mass function (IMF). Then the obtained mock populations were reddened with a 3D dust map and were subjected to the selection criteria corresponding to the RAVE and TGAS observational limitations as well as to additional cuts applied to the data sample. We calculated the quantities of interest separately at different heights above the Galactic plane, taking into account the distance error effects in horizontal and vertical directions into account separately.Results. The simulated vertical number density profile agrees well with the data. An underestimation of the stellar numbers begins at ∼800 pc from the Galactic plane, which is expected as the possible influence of populations from |z| > 1 kpc is ignored during the modelling. The lower main sequence (LMS) is found to be thinner and under-populated by 3.6% relative to the observations. The corresponding deficits for the upper main sequence (UMS) and red giant branch (RGB) are 6% and 34.7%, respectively. However, the intrinsic uncertainty related to the choice of stellar isochrones is ∼10% in the total stellar number. The vertical velocity distribution function f(|W |) simulated for the whole cylinder agrees to within 1σ with the data. This marginal agreement arises because the dynamically cold populations at heights < 200 pc from the Galactic plane are underestimated. We find that the model gives a fully realistic representation of the vertical gradient in stellar populations when studying the Hess diagrams for different horizontal slices. We also checked and confirm the consistency of our results with the newly available second Gaia data release (DR2). Conclusions. Based on these results and considering the uncertainties in the data selection as well as the sensitivity of the simulations to the sample selection function, we conclude that the fiducial JJ model confidently reproduces the vertical trends in the thin-disc stellar population properties. Thus, it can serve as a starting point for the future extension of the JJ model to other Galactocentric distances.

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The bimodal [Mg/Fe] versus [Fe/H] bulge sequence as revealed by APOGEE DR14

Rojas-Arriagada

Zoccali

Schultheis

et al. 2019

A&A

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Context. The Galactic bulge has a bimodal metallicity distribution function: different kinematic, spatial, and, potentially, age distributions characterize the metal-poor and metal-rich components. Despite this observed dichotomy, which argues for different formation channels for those stars, the distribution of bulge stars in the α-abundance versus metallicity plane has been found so far to be a rather smooth single sequence. Aims. We use data from the fourteenth data release of the APOGEE spectroscopic survey (DR14) to investigate the distribution in the Mg abundance (as tracer of the α-elements)-versus-metallicity plane of a sample of stars selected to be in the inner region of the bulge. Methods. A clean sample has been selected from the DR14 using a set of data-and pipeline-flags to ensure the quality of their fundamental parameters and elemental abundances. An additional selection made use of computed spectro-photometric distances to select a sample of likely bulge stars as those with R GC ≤ 3.5kpc. We adopt magnesium abundance as an α-abundance proxy for our clean sample as it has been proven to be the most accurate α-element as determined by ASPCAP, the pipeline for data products from APOGEE spectra. Results. From the distribution of our bulge sample in the [Mg/Fe]-versus-[Fe/H] plane, we found that the sequence is bimodal. This bimodality is given by the presence of a low-Mg sequence of stars parallel to the main high-Mg sequence over a range of ∼ 0.5 dex around solar metallicity. The two sequences merge above [Fe/H] ∼ 0.15 dex into a single sequence whose dispersion in [Mg/Fe] is larger than either of the two sequences visible at lower metallicity. This result is confirmed when we consider stars in our sample that are inside the bulge region according to trustworthy Gaia DR2 distances.

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Chempy: A flexible chemical evolution model for abundance fitting

Cited by 68 publications

References 101 publications

Abundance Ratios in GALAH DR2 and Their Implications for Nucleosynthesis

Abundance Ratios in GALAH DR2 and Their Implications for Nucleosynthesis

Local disc model in view of Gaia DR1 and RAVE data

The bimodal [Mg/Fe] versus [Fe/H] bulge sequence as revealed by APOGEE DR14

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