The tidal remnant of an unusually metal-poor globular cluster

Wan, Zhen; Lewis, Geraint F.; Li, Ting S.; Simpson, Jeffrey D.; Martell, Sarah L.; Zucker, D. B.; Mould, Jeremy; Erkal, Denis; Pace, Andrew B.; Mackey, A. D.; Ji, Alexander P.; Koposov, S. E.; Kuêhn, K.; Shipp, Nora; Balbinot, E.; Bland‐Hawthorn, J.; Casey, Andrew R.; Costa, G. S. Da; Kafle, Prajwal R.; Sharma, Sanjib; Silva, Gayandhi M. De

doi:10.1038/s41586-020-2483-6

Cited by 65 publications

(48 citation statements)

References 57 publications

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“…These conditions are related to the minimum metallicity of observed globular clusters (GCs: Forbes et al 2018). Forbes et al (2018) showed the metallicity floor of GCs in the Milky Way with 𝑍 ∼ 10 −2.5 𝑍 (but see , Wan et al 2020). Recently Larsen et al (2020) observed the lower metallicity GC of 𝑍 ∼ 10 −2.9 𝑍 in Andromeda galaxy.…”

Section: Summary and Discussionmentioning

confidence: 93%

Radiation hydrodynamics simulations of massive star cluster formation in giant molecular clouds

Fukushima,

Yajima

2021

Preprint

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By performing three-dimensional radiation hydrodynamics simulations, we study the formation of young massive star clusters (YMCs, 𝑀 * > 10 4 𝑀 ) in clouds with the surface density ranging from Σ cl = 80 to 3200 𝑀 pc −2 . We find that photoionization feedback suppresses star formation significantly in clouds with low surface density. Once the initial surface density exceeds ∼ 100 𝑀 pc −2 for clouds with 𝑀 cl = 10 6 𝑀 and 𝑍 = 𝑍 , most of the gas is converted into stars because the photoionization feedback is inefficient in deep gravitational potential. In this case, the star clusters are massive and gravitationally bounded as YMCs. The transition surface density increases as metallicity decreases, and it is ∼ 350 𝑀 pc −2 for 𝑍 = 10 −2 𝑍 . We show that more than 10 percent of star-formation efficiency (SFE) is needed to keep a star cluster gravitationally bounded even after the disruption of a cloud. Also, we develop a semi-analytical model reproducing the SFEs obtained in our simulations. We find that the SFEs are fit with a power-law function with the dependency ∝ Σ 1/2 cl for low-surface density and rapidly increases at the transition surface densities. The conditions of the surface density and the metallicity match recent observations of giant molecular clouds forming YMCs in nearby galaxies.

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Section: Summary and Discussionmentioning

confidence: 93%

Radiation hydrodynamics simulations of massive star cluster formation in giant molecular clouds

Fukushima,

Yajima

2021

Preprint

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“…Harris 1996Harris , 2010. However, dissolved, less massive GCs may have lower metallicities: the Phoenix stream likely consists of a single stellar population originating in a dissolved globular cluster of Z = 10 −2.7 Z (Wan et al 2020). Another example, the Sylgr stream, might be the remnant of another disrupted GC with stars of an even lower metallicity, Z = 10 −2.9 Z (Roederer & Gnedin 2019).…”

Section: Observational Signaturementioning

confidence: 99%

Globular Clusters and Streaming Velocities: Testing the new formation channel in high-resolution cosmological simulations

Schauer,

Bromm,

Boylan-Kolchin

et al. 2021

Preprint

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The formation of globular clusters and their relation to the distribution of dark matter have long puzzled astronomers. One of the most recently-proposed globular cluster formation channels ties ancient star clusters to the large-scale streaming velocity of baryons relative to dark matter in the early Universe. These streaming velocities affect the global infall of baryons into dark matter halos, the high-redshift halo mass function, and the earliest generations of stars. In some cases, streaming velocities may result in dense regions of dark-matter-free gas that becomes Jeans unstable, potentially leading to the formation of compact star clusters. We investigate this hypothesis using cosmological hydrodynamical simulations that include a full chemical network and the formation and destruction of H 2 , a process crucial for the formation of the first stars. We find that high-density gas in regions with significant streaming velocities -which constitute approximately 1% of the Universe -is indeed somewhat offset from the centers of dark matter halos, but this offset is typically significantly smaller than the virial radius. Gas outside of dark matter halos never reaches Jeans-unstable densities in our simulations. We postulate that low-level (Z ≈ 10 −3 Z ) metal enrichment by Population III supernovae may enable cooling in the extra-virial regions, allowing gas outside of dark matter halos to cool to the CMB temperature and become Jeans-unstable. Follow-up simulations that include both streaming velocities and metal enrichment by Population III supernovae are needed to understand if streaming velocities provide one path for the formation of globular clusters in the early Universe.

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“…Ravi, Sylgr and Phoenix are thin streams with orbits similar to Indus. With little metallicity variation within either Sylgr or Phoenix (Ibata et al 2019;Wan et al 2020), these streams likely originate from globular clusters hosted by the progenitor of Indus and Jhelum.…”

Section: Association With Disrupted Galaxiesmentioning

confidence: 99%

Orbital Clustering Identifies the Origins of Galactic Stellar Streams

Bonaca,

Naidu,

Conroy

et al. 2020

Preprint

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The origins of most stellar streams in the Milky Way are unknown. With improved proper motions provided by Gaia EDR3, we show that the orbits of 23 Galactic stellar streams are highly clustered in orbital phase space. Based on their energies and angular momenta, most streams in our sample can plausibly be associated with a specific (disrupted) dwarf galaxy host that brought them into the Milky Way. For eight streams we also identify likely globular cluster progenitors (four of these associations are reported here for the first time). Some of these stream progenitors are surprisingly far apart, displaced from their tidal debris by a few to tens of degrees. We identify stellar streams that appear spatially distinct, but whose similar orbits indicate they likely originate from the same progenitor. If confirmed as physical discontinuities, they will provide strong constraints on the mass-loss from the progenitor. The nearly universal ex-situ origin of existing stellar streams makes them valuable tracers of galaxy mergers and dynamical friction within the Galactic halo. Their phase-space clustering can be leveraged to construct a precise global map of dark matter in the Milky Way, while their internal structure may hold clues to the small-scale structure of dark matter in their original host galaxies.

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The tidal remnant of an unusually metal-poor globular cluster

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Cited by 65 publications

References 57 publications

Radiation hydrodynamics simulations of massive star cluster formation in giant molecular clouds

Radiation hydrodynamics simulations of massive star cluster formation in giant molecular clouds

Globular Clusters and Streaming Velocities: Testing the new formation channel in high-resolution cosmological simulations

Orbital Clustering Identifies the Origins of Galactic Stellar Streams

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