Resolved Massive Star Clusters in the Milky Way and Its Satellites: Brightness Profiles and a Catalog of Fundamental Parameters

ABSTRACT In our HST photometric survey, we have been searching for multiple stellar populations (MPs) in Magellanic Clouds (MCs) massive star clusters which span a significant range of ages (∼1.5–11 Gyr). In the previous papers of the series, we have shown that the age of the cluster represents one of the key factors in shaping the origin of the chemical anomalies. Here, we present the analysis of four additional clusters in the MCs, namely Lindsay 38, Lindsay 113, NGC 2121, and NGC 2155, for which we recently obtained new UV HST observations. These clusters are more massive than ∼104 M⊙ and have ages between ∼2.5 and ∼6 Gyr, i.e. located in a previously unexplored region of the cluster age/mass diagram. We found chemical anomalies, in the form of N spreads, in three out of four clusters in the sample, namely in NGC 2121, NGC 2155, and Lindsay 113. By combining data from our survey and HST photometry for three additional clusters in the Milky Way (namely 47 Tuc, M15, and NGC 2419), we show that the extent of the MPs in the form of N spread is a strong function of age, with older clusters having larger N spreads with respect to the younger ones. Hence, we confirm that cluster age plays a significant role in the onset of MPs.

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Maser Astrometry: from Galactic Structure to Local Group Cosmology

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312007314 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 359-367 ◽

Cited By ~ 2

Author(s):

Mark J. Reid

Keyword(s):

Large Scale ◽

Massive Star ◽

Milky Way ◽

Local Group ◽

Galactic Structure ◽

Proper Motions ◽

Star Forming ◽

Fundamental Parameters ◽

3 Dimensional ◽

Star Forming Regions

AbstractThis review summarizes current advances in astrometry of masers as they pertain to large-scale Galactic structure and dynamics and Local Group cosmology. Parallaxes and proper motions have now been measured for more than 60 massive star forming regions using the Japanese VERA array, the EVN and the VLBA. These results provide “gold standard” distances and 3-dimensional velocities for sources across the Milky Way, revealing its spiral structure. Modeling these data tightly constrains the fundamental parameters of the Milky Way: R0 and Θ0. Proper motions of Local Group galaxies have been measured, improving our understanding of the history and fate of the Group.

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Contribution of globular clusters to halos

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315009138 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 287-293

Author(s):

Angela Bragaglia

Keyword(s):

Star Formation ◽

Formation Mechanism ◽

Globular Clusters ◽

Massive Star ◽

Milky Way ◽

Star Clusters ◽

Early Evolution ◽

Light Elements ◽

Halo Stars ◽

Chemical Signatures

AbstractThe contribution of massive star clusters to their hosting halo dramatically depends on their formation mechanism and their early evolution. Massive globular clusters in the Milky Way (and in other galaxies) have been shown to display peculiar chemical patterns (light-elements correlations and anti-correlations) indicative of a complex star formation, confirmed by photometric evidence (spread or split sequences). I use these chemical signatures to try to understand what is the fraction of halo stars originally born in globular clusters.

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Massive infrared clusters in the Milky Way

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317002988 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 263-270

Author(s):

André-Nicolas Chené ◽

Sebastian Ramírez Alegría ◽

Jordanka Borissova ◽

Anthony Hervé ◽

Fabrice Martins ◽

...

Keyword(s):

Near Infrared ◽

Milky Way ◽

Galactic Center ◽

Massive Stars ◽

Star Clusters ◽

Infrared Observations ◽

Fundamental Parameters ◽

Dust Extinction ◽

Young Clusters ◽

Massive Clusters

AbstractOur position in the Milky Way (MW) is both a blessing and a curse. We are nearby to many star clusters, but the dust that is a product of their very existence obscures them. Also, many massive young clusters are expected to be located near, or across the Galactic Center, where the dust extinction is extreme (AV > 15 mag) and can be better penetrated by infrared photons. This paper reviews the discoveries and the study of new MW massive stars and massive clusters made possible by near infrared observations that are part of the VISTA Variables in the Vía Láctea (VVV) survey. It discusses what the studies of their fundamental parameters have taught us.

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The connection between stellar and nuclear clusters: Can an IMBH be sitting at the heart of the Milky Way?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007324 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 51-55

Author(s):

Manuel Arca Sedda

Keyword(s):

Massive Star ◽

Milky Way ◽

Star Clusters ◽

Galactic Nuclei ◽

Intermediate Mass ◽

Tidal Disruption ◽

Vast Number ◽

Supermassive Black Hole ◽

Nuclear Clusters ◽

Nuclear Cluster

AbstractA vast number of observed galactic nuclei are known to harbour a central supermassive black hole (SMBH). In their early lifetime, these systems might have witnessed the strong interaction between the SMBH and massive star clusters formed in the inner galactic regions. Due to the strong tidal field exerted from the SMBH, clusters are likely to undergo tidal disruption, releasing their stars all around the SMBH, and possibly driving the formation of a nuclear cluster (NC). This mechanism can contribute to populate galactic nuclei with intermediate-mass black holes (IMBH). Interactions with the central SMBH can lead to the formation of tight massive BH binaries (MBBH) that undergo coalescence via gravitational waves (GW) emission. We discuss this mechanism in the context of the Milky Way centre, exploring the possibility that SgrA*, the Galactic SMBH, has an IMBH companion.

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The accreted nuclear clusters of the Milky Way

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3407 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2514-2524

Author(s):

Joel Pfeffer ◽

Carmela Lardo ◽

Nate Bastian ◽

Sara Saracino ◽

Sebastian Kamann

Keyword(s):

Globular Clusters ◽

Milky Way ◽

Dwarf Galaxy ◽

Star Clusters ◽

Host Galaxy ◽

The Galaxy ◽

Nuclear Clusters ◽

The Common ◽

Massive Clusters ◽

Peculiar Case

ABSTRACT A number of the massive clusters in the halo, bulge, and disc of the Galaxy are not genuine globular clusters (GCs) but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs and can be readily traced back to their host galaxy (e.g. M54 and the Sagittarius Dwarf galaxy), others have proven more elusive. Here, we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, ω Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken, and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate-mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster–cluster merger.

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The effects of surface fossil magnetic fields on massive star evolution: III. The case of τ Sco

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab893 ◽

2021 ◽

Author(s):

Z Keszthelyi ◽

G Meynet ◽

F Martins ◽

A de Koter ◽

A David-Uraz

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Massive Star ◽

Slow Rotation ◽

Single Star ◽

Surface Magnetic Field ◽

Fundamental Parameters ◽

Chemical Enrichment ◽

Star Models ◽

Nitrogen Excess

Abstract τ Sco, a well-studied magnetic B-type star in the Uτer Sco association, has a number of surprising characteristics. It rotates very slowly and shows nitrogen excess. Its surface magnetic field is much more complex than a purely dipolar configuration which is unusual for a magnetic massive star. We employ the cmfgen radiative transfer code to determine the fundamental parameters and surface CNO and helium abundances. Then, we employ mesa and genec stellar evolution models accounting for the effects of surface magnetic fields. To reconcile τ Sco’s properties with single-star models, an increase is necessary in the efficiency of rotational mixing by a factor of 3 to 10 and in the efficiency of magnetic braking by a factor of 10. The spin down could be explained by assuming a magnetic field decay scenario. However, the simultaneous chemical enrichment challenges the single-star scenario. Previous works indeed suggested a stellar merger origin for τ Sco. However, the merger scenario also faces similar challenges as our magnetic single-star models to explain τ Sco’s simultaneous slow rotation and nitrogen excess. In conclusion, the single-star channel seems less likely and versatile to explain these discrepancies, while the merger scenario and other potential binary-evolution channels still require further assessment as to whether they may self-consistently explain the observables of τ Sco.

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From young massive star clusters to old globulars: long-term survival chances

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307001962 ◽

2006 ◽

Vol 2 (S237) ◽

pp. 408-408

Author(s):

Richard de Grijs

Keyword(s):

Galaxy Formation ◽

Massive Star ◽

Cluster Formation ◽

Star Clusters ◽

Term Survival ◽

Star Forming ◽

Distant Galaxies ◽

Wide Range ◽

Galaxy Collisions

Young, massive star clusters (YMCs) are the most notable and significant end products of violent star-forming episodes triggered by galaxy collisions and close encounters. The question remains, however, whether or not at least a fraction of the compact YMCs seen in abundance in extragalactic starbursts, are potentially the progenitors of (≳10 Gyr) old globular cluster (GC)-type objects. If we could settle this issue convincingly, one way or the other, the implications of such a result would have far-reaching implications for a wide range of astrophysical questions, including our understanding of the process of galaxy formation and assembly, and the process and conditions required for star (cluster) formation. Because of the lack of a statistically significant sample of YMCs in the Local Group, however, we need to resort to either statistical arguments or to the painstaking approach of case-by-case studies of individual objects in more distant galaxies.

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