MORGOTH: incorporating horizontal branch modelling into star formation history determinations

Savino, A.; Boer, T. J. L. de; Salaris, Maurizio; Tolstoy, Eline

doi:10.1093/mnras/sty1954

Cited by 17 publications

(19 citation statements)

References 68 publications

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“…Finally, we note that the absolute age scale of the SFH in Sculptor is uncertain, and is currently being debated. Weisz et al (2014) and Bettinelli et al (2019) derived a much shorter SFH in Sculptor (∼3 Gyr), than was reported by Savino et al (2018), and than we adopted here ( Fig. 1; de Boer et al 2012a).…”

Section: Chemical Clocks In Different Environmentssupporting

confidence: 58%

Neutron-capture elements in dwarf galaxies

Skúladóttir

Hansen

Salvadori

et al. 2019

A&A

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The heavy elements (Z > 30) are created in neutron (n)-capture processes that are predicted to happen at vastly different nucleosynthetic sites. To study these processes in an environment different from the Milky Way, we targeted the n-capture elements in red giant branch stars in the Sculptor dwarf spheroidal galaxy. Using ESO VLT/FLAMES spectra, we measured the chemical abundances of Y, Ba, La, Nd, and Eu in 98 stars covering the metalliticy range −2.4 < [Fe/H] < −0.9. This is the first paper in a series about the n-capture elements in dwarf galaxies, and here we focus on the relative and absolute timescales of the slow (s)- and rapid (r)-processes in Sculptor. From the abundances of the s-process element Ba and the r-process element Eu, it is clear that the r-process enrichment occurred throughout the entire chemical evolution history of Sculptor. Furthermore, there is no evidence for the r-process to be significantly delayed in time relative to core-collapse supernovae. Neutron star mergers are therefore unlikely the dominant (or only) nucleosynthetic site of the r-process. However, the products of the s-process only become apparent at [Fe/H] ≈ −2 in Sculptor, and the s-process becomes the dominant source of Ba at [Fe/H] ≳ −2. We tested the use of [Y/Mg] and [Ba/Mg] as chemical clocks in Sculptor. Similarly to what is observed in the Milky Way, [Y/Mg] and [Ba/Mg] increase towards younger ages. However, there is an offset in the trends, where the abundance ratios of [Y/Mg] in Sculptor are significantly lower than those of the Milky Way at any given age. This is most likely caused by metallicity dependence of yields from the s-process, as well as by a different relative contribution of the s-process to core-collapse supernovae in these galaxies. Comparisons of our results with data of the Milky Way and the Fornax dwarf spheroidal galaxy furthermore show that these chemical clocks depend on both metallicity and environment.

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Section: Chemical Clocks In Different Environmentssupporting

confidence: 58%

Neutron-capture elements in dwarf galaxies

Skúladóttir

Hansen

Salvadori

et al. 2019

A&A

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“…In particular, the gas-to-dust ratio used results in a very conservative, low value, of the RGB mass loss. The mass loss relation in the Sculptor dSph has been obtained by Salaris et al (2013) and Savino et al (2018) using an analogous approach to this work. The two measurements also show some differences.…”

Section: The Rgb Mass Lossmentioning

confidence: 99%

“…We model the CMD using MORGOTH (Savino et al 2018). MORGOTH is a SFH recovery method that uses synthetic CMDs to model all the evolutionary phases up to the beginning of the thermally pulsating asymptotic giant branch.…”

Section: The Set-upmentioning

confidence: 99%

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The HST/ACS star formation history of the Tucana dwarf spheroidal galaxy: clues from the horizontal branch

Savino

Tolstoy

Salaris

et al. 2019

A&A

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We report a new star formation history for the Tucana dwarf spheroidal galaxy, obtained from a new look at a deep HST/ACS colourmagnitude diagram. We combined information from the main sequence turn-off and the horizontal branch to resolve the ancient star formation rates on a finer temporal scale than previously possible. We show that Tucana experienced three major phases of star formation, two very close together at ancient times and the last one ending between 6 and 8 Gyr ago. We show that the three discrete clumps of stars on the horizontal branch are linked to the distinct episodes of star formation in Tucana. The spatial distribution of the clumps reveals that each generation of stars presents a higher concentration than the previous one. The simultaneous modelling of the horizontal branch and the main sequence turn-off also allows us to measure the amount of mass lost by red giant branch stars in Tucana with unprecedented precision, confirming dwarf spheroidals to be excellent laboratories to study the advanced evolution of low-mass stars.

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“…HB stars offer a uniquely luminous insight into the most ancient stellar populations in a galaxy, and it has recently been shown that they can offer a more accurate look at how star formation rates and metallicity varied at the earliest times (Salaris et al 2013;Savino et al 2015Savino et al , 2018. It is clear that the HBs in nearby galaxies all look different (see Figure 4), revealing a variety of early SFHs even in the smallest dwarf galaxies, even more so than had previously been envisaged (Savino et al, in prep).…”

Section: Ancient Main Sequence Turnoffsmentioning

confidence: 99%

Resolved stellar populations: the outlook for JWST and ELT

Tolstoy

2018

Proc. IAU

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The study of the resolved stellar populations in nearby galaxies and star clusters through the analysis of colour-magnitude diagrams provides the most detailed and quantitative determination of the star formation histories of these systems. The properties of different age populations provide an insight into distinct physical processes taking place during the entire history of the stellar system. The detection of the oldest main sequence turn-offs is currently restricted to stellar systems within the Local Group due to the limitations in spatial resolution and flux sensitivity of available telescopes. Individual stars need to be detected and accurately distinguished from their neighbours. To improve this situation we need to build new telescopes with larger primary mirrors that can deliver a very stable image quality at the diffraction limit. Over the next decade we can look forward to new larger telescope in space: the James Webb Space Telescope, currently scheduled to be launched in 2021; and several large telescope projects, the largest of which is the 39m ESO extremely large telescope on Cerro Armazones in Chile, currently scheduled to start operations in 2024.

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MORGOTH: incorporating horizontal branch modelling into star formation history determinations

Cited by 17 publications

References 68 publications

Neutron-capture elements in dwarf galaxies

Neutron-capture elements in dwarf galaxies

The HST/ACS star formation history of the Tucana dwarf spheroidal galaxy: clues from the horizontal branch

Resolved stellar populations: the outlook for JWST and ELT

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