Article
Astronomy & Astrophysics
Marta Reina-Campos, Benjamin W. Keller, J. M. Diederik Kruijssen, Jindra Gensior, Sebastian Trujillo-Gomez, Sarah M. R. Jeffreson, Joel L. Pfeffer, Alison Sills
Summary: The formation and evolution of stellar clusters are closely related to their host galaxies. This study presents the EMP-Pathfinder suite of simulations, which allows for the study of stellar cluster formation and evolution alongside their host galaxies. The simulations include a subgrid description for the interstellar medium (ISM) and consider the impact of a cold, dense ISM on star cluster properties. The results show that the presence of a cold ISM leads to the formation of older stellar cluster populations that are consistent with observations. Additionally, the formation of stellar clusters is highly dependent on the baryonic physics governing the properties of the cold, dense gas reservoir in the galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
I. Millan-Irigoyen, M. Molla, M. Cervino, Y. Ascasibar, M. L. Garcia-Vargas, P. R. T. Coelho
Summary: The HR-pyPopStar model presents high-resolution spectral energy distributions of Single Stellar Populations, considering various ages and metallicities, with a focus on the importance of wavelength resolution for interpreting observational data from advanced astronomical instruments.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ivan Cabrera-Ziri, Charlie Conroy
Summary: This study presents a simple approach to tackle the uncertainty in age determination of old integrated stellar populations. The results show that the age and HB properties can be accurately modeled using this technique, as supported by the comparison with resolved colour-magnitude diagrams.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
R. Zhang, S. Lucatello, A. Bragaglia, J. Alonso-Santiago, G. Andreuzzi, G. Casali, R. Carrera, E. Carretta, V. D'Orazi, A. Frasca, X. Fu, L. Magrini, I Minchev, L. Origlia, L. Spina, A. Vallenari
Summary: This study investigates giant stars in 18 OCs using high-resolution spectra and provides comprehensive chemical characterization for 16 OCs for the first time. Results show the behavior of lithium, sodium, and aluminum in stellar evolution and variations in abundance ratios in terms of radial, vertical, and age trends. Additionally, a comparison with models reveals the characteristics of O and Mg abundance ratios at different ages.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Mark Gieles, Oleg Y. Gnedin
Summary: Stellar-mass black holes can be retained in globular clusters until the present time. The mass-loss rate in globular cluster evolution is higher when black holes are present, especially near dissolution. We use a parametrized mass-loss rate based on N-body simulations to evolve an initial globular cluster mass function to an age of 12 billion years. The density profile of the mass lost from massive globular clusters resembles that of nitrogen-rich stars in the halo, confirming their origin from globular clusters. Including the effect of black holes reduces the need for additional disruption mechanisms in shaping the globular cluster mass function.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
G. Valle, M. Dell'Omodarme, E. Tognelli
Summary: This study explores the analysis methods for multiple stellar populations in globular clusters, using NGC 2808 as a case study. By employing established statistical clustering methods and addressing the issue of measurement errors, the results obtained differ from those reported in previous literature. The findings suggest that the existence of multiple populations is reliable in high-resolution spectroscopy data, but questionable in low-resolution spectroscopy data. Additionally, it is revealed that the commonly used histogram analysis is prone to generating false-positive findings. Therefore, the use of statistically grounded methods is crucial for conducting more robust and reproducible research.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
H. Baumgardt, J. Faller, N. Meinhold, C. McGovern-Greco, M. Hilker
Summary: We have studied stellar mass segregation in over 50 globular clusters and ultrafaint dwarf galaxy candidates and found that the amount of segregation is strongly correlated with relaxation time. Globular clusters with relaxation times equal to or longer than their ages show little to no mass segregation, indicating that they formed without primordial mass segregation. Ultrafaint dwarf galaxy candidates can be divided into segregated star clusters and unsegregated dark-matter dominated dwarf galaxies, with the segregation being influenced by initial conditions and the ability to withstand external tidal forces.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Valery Kravtsov, Sami Dib, Francisco A. Calderon, Jose Antonio Belinchon
Summary: Two generations of stars, G1 and G2, in Galactic globular clusters may have a close relationship, with G2 stars possibly formed through collisions/merging of G1 stars. Empirical dependencies between GC characteristics suggest a connection to this formation mechanism.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Marta Reina-Campos, Sebastian Trujillo-Gomez, Alis J. Deason, J. M. Diederik Kruijssen, Joel L. Pfeffer, Robert A. Crain, Nate Bastian, Meghan E. Hughes
Summary: This study explores whether the projected number density radial profiles of globular clusters (GCs) can be used to infer the structural properties of their host dark matter (DM) haloes. The results show that more massive galaxies host GC populations with shallower density profiles and greater radial extent. In addition, metal-poor GC subpopulations have shallower and more extended profiles compared to metal-rich subsamples. The study also finds strong correlations between the power-law slopes and effective radii of the GC populations and the structural properties of the DM haloes. Accounting for the dependence on galaxy stellar mass reduces the scatter of the relations. When applied to extragalactic GC systems, the study successfully recovers the scale radii and extent of the DM haloes with small uncertainties. Extragalactic GC systems provide a new avenue to explore the structure of DM haloes beyond the Local Group.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Eugenio Carretta
Summary: NGC 4833 is a metal-poor Galactic globular cluster with extreme chemical composition, including a broad Na-O anti-correlation and significant excesses of Ca and Sc. The study confirms that self-enrichment from first generation polluters occurred at high temperatures, producing species such as K and possibly Ca. The abundance of potassium in GCs appears to be related to other elements, indicating a complex chemical pattern in multiple stellar populations.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
M. Tailo, E. Corsaro, A. Miglio, J. Montalban, K. Brogaard, A. P. Milone, A. Stokholm, G. Casali, A. Bragaglia
Summary: In this study, a new asteroseismic analysis based on K2 mission data was conducted on stars in the globular cluster M4, leading to the detection of solar-like oscillations in a large sample of 37 stars. By combining asteroseismology and multi-band photometry, estimates of mass and radius were obtained, in agreement with independent sources, reaffirming the reliability of asteroseismology in low metallicity regimes. The study also revealed important information about the mass differences between stellar populations in M4 and the presence of a mass-temperature gradient in red horizontal branch stars, providing valuable insights into the cluster's evolution.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Kenji Bekki
Summary: We discuss a scenario for the formation of globular clusters (GC), in which the gas ejected by the first generation (1G) of stars and intermediate-mass close binaries (IMCBs) gives rise to the formation of the second generation (2G) of stars. We find that the mass fraction of 2G stars can be high, not strongly dependent on the fraction of binary stars, and the differences in elemental abundances between 1G and 2G stars can be significant. The formation history of 2G stars shows at least two peaks, and the observed correlation between the mass fraction of 2G stars and the initial mass of the GC can be explained by the stellar initial mass function.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
T. M. Lawlor
Summary: Late thermal pulse (LTP) stellar evolution models show rapid looping evolution in the Hertzsprung-Russell (HR) diagram between the asymptotic giant branch (AGB) and planetary nebula (PN) phase. LTP objects have a shorter duration than very late thermal pulses (VLTPs), but exhibit significant changes in temperature, luminosity, and size. We present stellar evolution calculations for LTP models with various metallicities and masses, focusing on a dense series (1.2 M-circle dot, Z = 0.015). We discuss different types of LTP eruptions based on temperature and present time-scales for heating, peak helium-burning luminosity, rapid decline, and cooling and brightening.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Eugenio Carretta, Angela Bragaglia
Summary: We present the abundance analysis of 185 giants in the bulge globular cluster NGC 6388, showing that a single class of polluters can explain the anti-correlations among light elements. The abundance pattern of other elements in NGC 6388 is similar to bulge field stars, ruling out an accreted origin. The neutron-capture elements show overall uniformity, with a scatter in the [Zr/Fe] ratio correlated to Na and Al abundances.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
M. McKenzie, D. Yong, A. F. Marino, S. Monty, E. Wang, A. Karakas, A. P. Milone, M. Legnardi, I. U. Roederer, S. Martell, D. Horta
Summary: High-quality VLT/UVES spectra of six red giant branch stars in M22 reveal variations in abundance of elements such as Fe, Na, and Si. The study suggests that M22 hosts two stellar populations with abundance differences, possibly indications of a nuclear star cluster, merged clusters, or an original building block of the Milky Way.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)