The Hubble Space Telescope UV legacy survey of galactic globular clusters – XVI. The helium abundance of multiple populations

Milone, A. P.; Marino, A. F.; Renzini, A.; D’Antona, Francesca; Anderson, Jay; Barbuy, B.; Bedin, L. R.; Bellini, Andrea; Brown, Thomas M.; Cassisi, S.; Cordoni, G.; Lagioia, E. P.; Nardiello, D.; Ortolani, S.; Piotto, G.; Sarajedini, Ata; Tailo, M.; Marel, Roeland P. van der; Vesperini, Enrico

doi:10.1093/mnras/sty2573

Cited by 204 publications

(356 citation statements)

References 113 publications

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“…In figure 11 of Milone et al (2015) and in figure 4 of Milone et al (2018), the comparison of spectra of MS stars with different He abundance shows a significant flux difference, throughout the whole visible interval, that it is not present in our results (see the bottom panel of Fig. 2).…”

Section: Spectroscopic Indicescontrasting

confidence: 81%

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Synthetic spectroscopic indices for identifying multiple stellar populations in globular clusters

Bertone

Chávez

Mendoza

2020

Monthly Notices of the Royal Astronomical Society

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We present an investigation of synthetic spectroscopic indices that can plausibly help in identifying the presence of multiple stellar populations in globular clusters. The study is based on a new grid of stellar model atmospheres and high-resolution (R=500,000) synthetic spectra, that consider chemical partitions that have been singled out in Galactic globular clusters. The database is composed of 3472 model atmospheres and theoretical spectra calculated with the collection of Fortran codes DFSYNTHE, AT-LAS9 and SYNTHE, developed by Robert L. Kurucz. They cover a range of effective temperature from 4300 to 7000 K, surface gravity from 2.0 to 5.0 dex and four different chemical compositions. A set of 19 spectroscopic indices were calculated from a degraded version (R=2500) of the theoretical spectra dataset. The set includes five indices previously used in the context of globular clusters analyses and 14 indices that we have newly defined by maximizing the capability of differentiating the chemical compositions. We explored the effects of atmospheric parameters on the index values and identified the optimal spectral diagnostics that allow to trace the signatures of objects of different stellar populations, located in the main sequence, the red giant branch and the horizontal branch. We found a suitable set of indices, that mostly involve molecular bands (in particular NH, but also CH and CN), that are very promising for spectroscopically identifying multiple stellar populations in globular clusters.

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Section: Spectroscopic Indicescontrasting

confidence: 81%

“…2). In this case, one has to note that Milone et al (2015) and Milone et al (2018) compare stars with the same luminosity located on different isochrones and, therefore, with different T eff , that modifies the overall slope of the spectral energy distribution, while our match considers a constant T eff .…”

Section: Spectroscopic Indicesmentioning

confidence: 99%

Synthetic spectroscopic indices for identifying multiple stellar populations in globular clusters

Bertone

Chávez

Mendoza

2020

Monthly Notices of the Royal Astronomical Society

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“…This issue can be successfully overcome by invoking a maximum He enrichment of up to 0.020 ± 0.005 within NGC 2121, for a total RGB mass-loss of ∼0.13 M . The value of ∆Y ini suggested for NGC 2121 (M = 0.9×10 5 M , McLaughlin & van der Marel 2005) would follow the relation observed for MW GCs and MCs clusters between ∆Y ini and the mass of the cluster itself (Milone et al 2018b;Baumgardt & Hilker 2018).…”

Section: Helium Enrichment In Ngc 2121supporting

confidence: 62%

Chromosome maps of young LMC clusters: an additional case of coeval multiple populations

Saracino

Martocchia

Bastian

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Recent studies have revealed that the Multiple Populations (MPs) phenomenon does not occur only in ancient and massive Galactic globular clusters (GCs), but it is also observed in external galaxies, where GCs sample a wide age range with respect to the Milky Way. However, for a long time, it was unclear whether we were looking at the same phenomenon in different environments or not. The first evidence that the MPs phenomenon is the same regardless of cluster age and host galaxy came out recently, when an intermediate-age cluster from the Small Magellanic Cloud, Lindsay 1, and a Galactic GC have been directly compared. By complementing those data with new images from the Hubble Space Telescope (HST), we extend the comparison to two clusters of different ages: NGC 2121 (∼2.5Gyr) and NGC 1783 (∼1.5Gyr), from the Large Magellanic Cloud. We find a clear correlation between the RGB width in the pseudo-colour C F275W,F343N,F438W and the age of the cluster itself, with the older cluster having larger σ(C F275W,F343N,F438W ) RGB and vice-versa. Unfortunately, the σ values cannot be directly linked to the N-abundance variations within the clusters before properly taking account the effect of the first dredge-up. Such HST data also allow us to explore whether multiple star-formation episodes occurred within NGC 2121. The two populations are indistinguishable, with an age difference of only 6±12 Myr and an initial Helium spread of 0.02 or lower. This confirms our previous results, putting serious constraints on any model proposed to explain the origin of the chemical anomalies in GCs.

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“…This is in contrast with massive GCs, where 1G and 2G stars host sub-populations with large differences in helium and light-element abundance (e.g. Milone et al 2017Milone et al , 2018Marino et al 2019).…”

Section: Introductionmentioning

confidence: 85%

“…The dataset used in this paper consists of images collected through the Wide Field Channel of the Advanced Camera for Survey (WFC/ACS) and the Ultraviolet and Visual Channel of the Wide Field Camera 3 (UVIS/WFC3) on board HST. The main properties of the images are summarized in Piotto et al (2015) and Milone et al (2018).…”

Section: Data and Data Analysismentioning

confidence: 99%

The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – XXI. Binaries among multiple stellar populations

Milone

Vesperini

Marino

et al. 2019

Monthly Notices of the Royal Astronomical Society

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A number of scenarios for the formation of multiple populations in globular clusters (GCs) predict that second generation (2G) stars form in a compact and dense subsystem embedded in a more extended first-generation (1G) system. If these scenarios are accurate, a consequence of the denser 2G formation environment is that 2G binaries should be more significantly affected by stellar interactions and disrupted at a larger rate than 1G binaries. The fractions and properties of binary stars can thus provide a dynamical fingerprint of the formation epoch of multiple-population GCs and their subsequent dynamical evolution. We investigate the connection between binaries and multiple populations in five GCs, NGC 288, NGC 6121 (M 4), NGC 6352, NGC 6362, and NGC 6838 (M 71). To do this, we introduce a new method based on the comparison of Hubble Space Telescope observations of binaries in the F275W, F336W, F438W, F606W and F814W filters with a large number of simulated binaries. In the inner regions probed by our data we do not find large differences between the local 1G and the 2G binary incidences in four of the studied clusters, the only exception being M 4 where the 1G binary incidence is about three times larger than the 2G incidence. The results found are in general agreement with the results of simulations predicting significant differences in the global 1G and 2G incidences and in the local values in the clusters' outer regions but similar incidences in the inner regions. The significant difference found in M 4 is consistent with simulations with a larger fraction of wider binaries. Our analysis also provides the first evidence of mixed (1G-2G) binaries, a population predicted by numerical simulations to form in a cluster's inner regions as a result of stellar encounters during which one component of a binary is replaced by a star of a different population.

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The Hubble Space Telescope UV legacy survey of galactic globular clusters – XVI. The helium abundance of multiple populations

Cited by 204 publications

References 113 publications

Synthetic spectroscopic indices for identifying multiple stellar populations in globular clusters

Synthetic spectroscopic indices for identifying multiple stellar populations in globular clusters

Chromosome maps of young LMC clusters: an additional case of coeval multiple populations

The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – XXI. Binaries among multiple stellar populations

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