AWISESurvey of New Star Clusters in the Central Plane Region of the Milky Way

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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Reanalysis of nearby open clusters using Gaia DR1/TGAS and HSOY

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731905 ◽

2018 ◽

Vol 615 ◽

pp. A12 ◽

Cited By ~ 12

Author(s):

Steffi X. Yen ◽

Sabine Reffert ◽

Elena Schilbach ◽

Siegfried Röser ◽

Nina V. Kharchenko ◽

...

Keyword(s):

Milky Way ◽

Open Cluster ◽

Star Clusters ◽

Open Clusters ◽

Parameter Estimates ◽

Cluster Membership ◽

Fitting Procedure ◽

Cluster Data ◽

The Galaxy ◽

Automatic Tool

Context. Open clusters have long been used to gain insights into the structure, composition, and evolution of the Galaxy. With the large amount of stellar data available for many clusters in the Gaia era, new techniques must be developed for analyzing open clusters, as visual inspection of cluster color-magnitude diagrams is no longer feasible. An automatic tool will be required to analyze large samples of open clusters. Aims. We seek to develop an automatic isochrone-fitting procedure to consistently determine cluster membership and the fundamental cluster parameters. Methods. Our cluster characterization pipeline first determined cluster membership with precise astrometry, primarily from TGAS and HSOY. With initial cluster members established, isochrones were fitted, using a χ2 minimization, to the cluster photometry in order to determine cluster mean distances, ages, and reddening. Cluster membership was also refined based on the stellar photometry. We used multiband photometry, which includes ASCC-2.5 BV, 2MASS JHKs, and Gaia G band. Results. We present parameter estimates for all 24 clusters closer than 333 pc as determined by the Catalogue of Open Cluster Data and the Milky Way Star Clusters catalog. We find that our parameters are consistent to those in the Milky Way Star Clusters catalog. Conclusions. We demonstrate that it is feasible to develop an automated pipeline that determines cluster parameters and membership reliably. After additional modifications, our pipeline will be able to use Gaia DR2 as input, leading to better cluster memberships and more accurate cluster parameters for a much larger number of clusters.

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The Milky Way: Home to Star Clusters

Star Clusters and How to Observe Them - Astronomer’s Observing Guides ◽

10.1007/1-84628-198-9_2 ◽

2006 ◽

pp. 9-12

Keyword(s):

Milky Way ◽

Star Clusters

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The search for multiple populations in Magellanic Clouds clusters – V. Correlation between cluster age and abundance spreads

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1596 ◽

2019 ◽

Vol 487 (4) ◽

pp. 5324-5334 ◽

Cited By ~ 21

Author(s):

S Martocchia ◽

E Dalessandro ◽

C Lardo ◽

I Cabrera-Ziri ◽

N Bastian ◽

...

Keyword(s):

Significant Role ◽

Massive Star ◽

Milky Way ◽

Star Clusters ◽

Magellanic Clouds ◽

Key Factors ◽

Strong Function ◽

Combining Data ◽

Chemical Anomalies ◽

Cluster Age

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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Globular clusters and their link with stellar populations in the Milky Way

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007361 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 19-23

Author(s):

David Yong

Keyword(s):

Chemical Evolution ◽

Globular Clusters ◽

Milky Way ◽

Star Clusters ◽

Stellar Populations ◽

Chemical Compositions ◽

Chemical Abundance ◽

Chemical Enrichment ◽

Similarities And Differences ◽

Insight Into

AbstractObservations of stellar chemical compositions enable us to identify connections between globular clusters and stellar populations in the Milky Way. In particular, chemical abundance ratios provide detailed insight into the chemical enrichment histories of star clusters and the field populations. For some elements, there are striking differences between field and cluster stars which reflect different nucleosynthetic processes and/or chemical evolution. The goal of this talk was to provide an overview of similarities and differences in chemical compositions between globular clusters and the Milky Way as well as highlighting a few areas for further examination.

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A deep view into the nucleus of the Sagittarius dwarf spheroidal galaxy: M54

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007907 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 47-50

Author(s):

M. Alfaro-Cuello ◽

N. Kacharov ◽

N. Neumayer ◽

A. Mastrobuono-Battisti ◽

N. Lützgendorf ◽

...

Keyword(s):

Metal Complex ◽

Detailed Analysis ◽

Globular Clusters ◽

Milky Way ◽

Dwarf Galaxies ◽

Dwarf Galaxy ◽

Star Clusters ◽

High Mass ◽

Data Set

AbstractNuclear star clusters hosted by dwarf galaxies exhibit similar characteristics to high-mass, metal complex globular clusters. This type of globular clusters could, therefore, be former nuclei from accreted galaxies. M54 resides in the photometric center of the Sagittarius dwarf galaxy, at a distance where resolving stars is possible. M54 offers the opportunity to study a nucleus before the stripping of their host by the tidal field effects of the Milky Way. We use a MUSE data set to perform a detailed analysis of over 6600 stars. We characterize the stars by metallicity, age, and kinematics, identifying the presence of three stellar populations: a young metal-rich (YMR), an intermediate-age metal-rich (IMR), and an old metal-poor (OMP). The evidence suggests that the OMP population is the result of accretion of globular clusters in the center of the host, while the YMR population was born in-situ in the center of the OMP population.

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The Galactic System of Open Star Clusters: A Personal Perspective

Symposium - International Astronomical Union ◽

10.1017/s0074180900223334 ◽

2002 ◽

Vol 207 ◽

pp. 24-37

Author(s):

Randy L. Phelps

Keyword(s):

Milky Way ◽

Star Clusters ◽

Open Clusters ◽

Personal Perspective ◽

Open Star Clusters ◽

Nearby Star ◽

Open Star ◽

Galactic System ◽

The Status ◽

Open Star Cluster

Technology is now allowing for the investigation of star clusters outside of the Milky Way. As attention turns to the extragalactic star clusters, a perception that the system of star clusters in the Milky Way is well understood may grow, resulting in the neglect of these important objects. In this review, the status of our understanding of the Milky Way's open star cluster population will be discussed. Specifically, I will attempt to illustrate not only the important information that can and must be learned from these nearby star clusters, but also the degree to which our understanding of the Galactic open clusters remains incomplete.

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Distribution of CO in the Southern Milky Way and large-scale structure in the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900242435 ◽

1985 ◽

Vol 106 ◽

pp. 203-204

Author(s):

W.H. Mccutcheon ◽

B. J. Robinson ◽

R. N. Manchester ◽

J. B. Whiteoak

Keyword(s):

Large Scale ◽

Milky Way ◽

Galactic Plane ◽

Large Scale Structure ◽

Sampling Interval ◽

Scale Structure ◽

Plane Region ◽

The Galaxy ◽

Csiro Division

The southern galactic-plane region, in the ranges 294° ≤ 1 ≤ 358°, −0°.075 ≤ b ≤ 0°.075, has been surveyed in the J = 1–0 line of 12CO with a sampling interval of 3′ arc. Observations were made with the 4-metre telescope at the CSIRO Division of Radiophysics in 1980 and 1981. Details of equipment and observing procedure are given in Robinson et al. (1982, 1983); see also McCutcheon et al. (1983).

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