Multiple Populations in Star Clusters

Milone, A. P.; Marino, A. F.

doi:10.3390/universe8070359

Cited by 52 publications

(19 citation statements)

References 271 publications

(503 reference statements)

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“…Hence, it is optimal for deriving photometry in crowded regions (see Sabbi et al 2016;Bellini et al 2017;Milone et al 2022, for details). We calibrate the HST photometry to the VEGA mag system as in Milone et al (2022) and by using the photometric zero points provided in the Space Telescope Science Institute web page for WFC/ACS, UVIS/WFC3, and NIR/WFC3 1 . The stellar positions are corrected for geometric distortion by using the solution by Anderson & King (2006) and Bellini et al (2011), andAnderson (2022) for WFC/ACS, UVIS/WFC3, and NIR/WFC3, respectively.…”

Section: Hst Datamentioning

confidence: 99%

“…Photometry has been calibrated to the VEGA mag system by using the most-updated zero points provided by the STScI webpage 2 and the procedure by Milone et al (2022). Moreover, we corrected the stellar positions in the F115W images by using the distortion solution derived in the Appendex A for the NIRCam SW detectors.…”

Section: Nircam Datamentioning

confidence: 99%

“…Moreover, we corrected the stellar positions in the F115W images by using the distortion solution derived in the Appendex A for the NIRCam SW detectors. Stars with high-precision photometry and astrometry as selected as in Section 2.1 (see Milone et al 2022, for details)…”

Section: Nircam Datamentioning

confidence: 99%

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Multiple Stellar Populations in Globular Clusters with JWST: a NIRCam view of 47 Tucanae

Milone¹,

Marino²,

Dotter³

et al. 2023

Preprint

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We use images collected with the near-infrared camera (NIRCam) on board the James Webb Space Telescope and with the Hubble Space Telescope (HST) to investigate multiple populations at the bottom of the main sequence (MS) of 47 Tucanae. The m F115W vs. m F115W −m F322W2 CMD from NIRCam shows that, below the knee, the MS stars span a wide color range, where the majority of M-dwarfs exhibit blue colors, and a tail of stars are distributed toward the red. A similar pattern is observed from the m F160W vs. m F110W − m F160W color-magnitude diagram (CMD) from HST, and multiple populations of M-dwarfs are also visible in the optical m F606W vs. m F606W − m F814W CMD. The NIRCam CMD shows a poorly-populated sequence of faint MS stars that we tentatively associate with a population of very low-mass stars. We introduce a chromosome map of M-dwarfs that reveals an extended first population and three main groups of second-population stars. By combining isochrones and synthetic spectra with appropriate chemical composition, we simulate colors and magnitudes of different stellar populations in the NIRCam filters (at metallicities [Fe/H]=-1.5 and [Fe/H]=-0.75) and identify the photometric bands that provide the most efficient diagrams to investigate the multiple populations in globular clusters. Models are compared with the observed CMDs of 47 Tucanae to constrain M-dwarfs' chemical composition. Our analysis suggests that the oxygen range needed to reproduce the colors of first-and second-population M-dwarfs is similar to that inferred from spectroscopy of red giants, challenging the proposal that the chemical variations are due to mass transfer phenomena in proto-clusters.

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Section: Hst Datamentioning

confidence: 99%

Section: Nircam Datamentioning

confidence: 99%

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Multiple Stellar Populations in Globular Clusters with JWST: a NIRCam view of 47 Tucanae

Milone¹,

Marino²,

Dotter³

et al. 2023

Preprint

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“…The puzzle of the origin of the multiple stellar populations (mPOPs) in Galactic globular clusters (GCs) has been controversial since their discovery. The large amount of spectroscopic and photometric data collected so far has provided almost all observational information we know about mPOPs in GCs, but no definitive consensus has been reached yet about the formation and evolution of mPOPs (Gratton et al 2012(Gratton et al , 2019Renzini et al 2015;Bastian & Lardo 2018;Cassisi & Salaris 2020;Milone & Marino 2022). The interplay between theoretical and observational efforts has pushed the community to find new ways to constrain the origin of mPOPs in GCs.…”

Section: Introductionmentioning

confidence: 99%

The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIV. Differences in Internal Kinematics of Multiple Stellar Populations

Libralato

Vesperini

Bellini

et al. 2023

ApJ

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Our understanding of the kinematic properties of multiple stellar populations (mPOPs) in Galactic globular clusters (GCs) is still limited compared to what we know about their chemical and photometric characteristics. Such limitation arises from the lack of a comprehensive observational investigation of this topic. Here we present the first homogeneous kinematic analysis of mPOPs in 56 GCs based on high-precision proper motions computed with Hubble Space Telescope data. We focused on red-giant-branch stars, for which the mPOP tagging is clearer, and measured the velocity dispersion of stars belonging to first (1G) and second generations (2G). We find that 1G stars are generally kinematically isotropic even at the half-light radius, whereas 2G stars are isotropic at the center and become radially anisotropic before the half-light radius. The radial anisotropy is induced by a lower tangential velocity dispersion of 2G stars with respect to the 1G population, while the radial component of the motion is comparable. We also show possible evidence that the kinematic properties of mPOPs are affected by the Galactic tidal field, corroborating previous observational and theoretical results suggesting a relation between the strength of the external tidal field and some properties of mPOPs. Although limited to the GCs’ central regions, our analysis leads to new insights into the mPOP phenomenon, and provides the motivation for future observational studies of the internal kinematics of mPOPs.

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“…Cluster mass has been suggested to be a universal parameter that determines the complexity of MPs, e.g., more massive clusters have larger variations in abundance and fractions of enriched populations (Bastian & Lardo 2018;Milone et al 2020); more massive Type II GCs show larger iron spread (Milone & Marino 2022). Exploring the critical cluster mass for the formation of MPs will certainly expand upon the current MP scenarios.…”

Section: Introductionmentioning

confidence: 99%

Multiple Populations in Low-mass Globular Clusters: Eridanus

Wang

Tang

et al. 2023

ApJ

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Multiple populations (MPs), characterized by variations in light elemental abundances, have been found in stellar clusters in the Milky Way, Magellanic Clouds, as well as several other dwarf galaxies. Based on a large number of observations, mass has been suggested to be a key parameter affecting the presence and appearance of MPs in stellar clusters. To further investigate the existence of MPs in low-mass clusters and explore the mass threshold for the formation of MPs, we carried out a project studying the composition of the stellar population in several low-mass Galactic globular clusters. Here we present our study on the cluster Eridanus. With blue-UV low-resolution spectra obtained with the OSIRIS/Multi-object spectrograph on the Gran Telescopio Canarias, we computed the spectral indices of CH and CN for a sample of giant stars and derived their carbon and nitrogen abundances using model spectra. A significant dispersion in the initial surface abundance of nitrogen was found in the sample, indicating the existence of MPs in Eridanus. Inspecting the age–initial mass distribution of in situ clusters with MPs, we find a slight trend that initial mass increases with increasing age, and the lowest initial masses of log M initial ∼ 4.98 and 5.26 are found at the young and old end, respectively, which might provide a rough reference for the mass threshold for clusters to form MPs. However, more observations of clusters with low initial masses are still necessary before any firm conclusion can be drawn.

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Multiple Populations in Star Clusters

Cited by 52 publications

References 271 publications

Multiple Stellar Populations in Globular Clusters with JWST: a NIRCam view of 47 Tucanae

Multiple Stellar Populations in Globular Clusters with JWST: a NIRCam view of 47 Tucanae

The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIV. Differences in Internal Kinematics of Multiple Stellar Populations

Multiple Populations in Low-mass Globular Clusters: Eridanus

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