Globular clusters and their contribution to the formation of the Galactic halo

AbstractThis is a “biased” review because I will show recent evidence on the contribution of globular clusters (GCs) to the halo of our Galaxy seen through the lens of the new paradigm of multiple populations in GCs. I will show a few examples where the chemistry of multiple populations helps to answer hot questions including whether and how much GCs did contribute to the halo population, if we have evidence of the GCs-halo link, what are the strengths and weak points concerning this contribution.

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Planetary Nebulae, Globular Clusters and the Galactic Halo

International Astronomical Union Colloquium ◽

10.1017/s0252921100033285 ◽

1973 ◽

Vol 21 ◽

pp. 26-28

Author(s):

Sidney Van Den Bergh

Keyword(s):

Globular Clusters ◽

Galactic Halo ◽

Planetary Nebulae ◽

Halo Population

AbstractPlanetary nebulae are used as a tracer for halo Population II stars. A comparison of the number of planetary nebulae in the galactic pole caps (|b| ≥ 45°) with the number of planetaries in globular clusters suggests that (to within a factor of 2 or 3) the galactic halo has a luminosity LB ⋍ 2 × 108L⊙. From the work of Oort it is estimated that the galactic halo has a mass of at least so that for the galactic halo.

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Meet the family − the catalog of known hot subdwarf stars

Open Astronomy ◽

10.1515/astro-2017-0031 ◽

2017 ◽

Vol 26 (1) ◽

Author(s):

Stephan Geier ◽

Roy H. Østensen ◽

Peter Nemeth ◽

Ulrich Heber ◽

Nicola P. Gentile Fusillo ◽

...

Keyword(s):

Globular Clusters ◽

Galactic Halo ◽

Far Infrared ◽

Sloan Digital Sky Survey ◽

Proper Motions ◽

Sky Survey ◽

The Family ◽

Quantitative Spectral Analysis ◽

Hot Subdwarfs ◽

Halo Population

AbstractIn preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities and light curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection criteria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOB stars from the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters ω Cen and NGC 2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters.

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Meet the family − the catalog of known hot subdwarf stars

Open Astronomy ◽

10.1515/astro-2017-0432 ◽

2017 ◽

Vol 26 (1) ◽

Cited By ~ 11

Author(s):

Stephan Geier ◽

Roy H. Østensen ◽

Peter Nemeth ◽

Ulrich Heber ◽

Nicola P. Gentile Fusillo ◽

...

Keyword(s):

Globular Clusters ◽

Galactic Halo ◽

Far Infrared ◽

Sloan Digital Sky Survey ◽

Proper Motions ◽

Sky Survey ◽

The Family ◽

Quantitative Spectral Analysis ◽

Hot Subdwarfs ◽

Halo Population

AbstractIn preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities and light curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection criteria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOB stars from the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters ! Cen and NGC 2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters.

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II. The Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900177277 ◽

1959 ◽

Vol 7 ◽

pp. 22-27 ◽

Cited By ~ 1

Author(s):

G. Larsson-Leander

Keyword(s):

Globular Clusters ◽

Galactic Halo ◽

Red Giants ◽

Polar Regions ◽

Rr Lyrae ◽

The Galaxy ◽

Halo Population

The objects from which the structure of the galactic halo may be derived by optical means are the extreme population II objects such as RR Lyrae variables with periods longer than 0-4 days, the sub-dwarfs, globular clusters, stars similar to those found in globular clusters such as the bright red giants, and the blue stars found in the galactic polar regions. The longperiod variables with periods shorter than 200 days and the ordinary highvelocity stars are now regarded as belonging to an intermediate population II, somewhat younger than the halo population II proper.

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Creation/destruction of ultra-wide binaries in tidal streams

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3700 ◽

2020 ◽

Author(s):

Jorge Peñarrubia

Keyword(s):

Globular Clusters ◽

Galactic Halo ◽

Local Density ◽

Formation Rate ◽

Semimajor Axis ◽

Major Axis ◽

Binding Energies ◽

Semi Major Axis ◽

The Mean ◽

Tidal Streams

Abstract This paper uses statistical and N-body methods to explore a new mechanism to form binary stars with extremely large separations (≳ 0.1 pc), whose origin is poorly understood. Here, ultra-wide binaries arise via chance entrapment of unrelated stars in tidal streams of disrupting clusters. It is shown that (i) the formation of ultra-wide binaries is not limited to the lifetime of a cluster, but continues after the progenitor is fully disrupted, (ii) the formation rate is proportional to the local phase-space density of the tidal tails, (iii) the semimajor axis distribution scales as p(a)da ∼ a1/2da at a ≪ D, where D is the mean interstellar distance, and (vi) the eccentricity distribution is close to thermal, p(e)de = 2ede. Owing to their low binding energies, ultra-wide binaries can be disrupted by both the smooth tidal field and passing substructures. The time-scale on which tidal fluctuations dominate over the mean field is inversely proportional to the local density of compact substructures. Monte-Carlo experiments show that binaries subject to tidal evaporation follow p(a)da ∼ a−1da at a ≳ apeak, known as Öpik’s law, with a peak semi-major axis that contracts with time as apeak ∼ t−3/4. In contrast, a smooth Galactic potential introduces a sharp truncation at the tidal radius, p(a) ∼ 0 at a ≳ rt. The scaling relations of young clusters suggest that most ultra-wide binaries arise from the disruption of low-mass systems. Streams of globular clusters may be the birthplace of hundreds of ultra-wide binaries, making them ideal laboratories to probe clumpiness in the Galactic halo.

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Formation of massive globular clusters with dark matter and its implication on dark matter annihilation

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa089 ◽

2020 ◽

Vol 496 (1) ◽

pp. L70-L74

Author(s):

Henriette Wirth ◽

Kenji Bekki ◽

Kohei Hayashi

Keyword(s):

Dark Matter ◽

Observational Studies ◽

Globular Clusters ◽

Galactic Halo ◽

Dwarf Galaxies ◽

Large Range ◽

Dark Matter Annihilation ◽

Central Regions ◽

Γ Ray ◽

The Masses

ABSTRACT Recent observational studies of γ-ray emission from massive globular clusters (GCs) have revealed possible evidence of dark matter (DM) annihilation within GCs. It is, however, still controversial whether the emission comes from DM or from millisecond pulsars. We here present the new results of numerical simulations, which demonstrate that GCs with DM can originate from nucleated dwarfs orbiting the ancient Milky Way. The simulated stripped nuclei (i.e. GCs) have the central DM densities ranging from 0.1 to several M⊙ pc−3, depending on the orbits and the masses of the host dwarf galaxies. However, GCs born outside the central regions of their hosts can have no/little DM after their hosts are destroyed and the GCs become the Galactic halo GCs. These results suggest that only GCs originating from stellar nuclei of dwarfs can possibly have DM. We further calculate the expected γ-ray emission from these simulated GCs and compare them to observations of ω Cen. Given the large range of DM densities in the simulated GCs, we suggest that the recent possible detection of DM annihilation from GCs should be more carefully interpreted.

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