Massive star clusters in galaxies

Harris, William E.

doi:10.1098/rsta.2009.0256

Cited by 43 publications

(57 citation statements)

References 92 publications

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“…Z = 0.0005 and Z = 0.001), and "high metallicity" (Z = 0.005) GCs. This is chosen to simplify the comparison between our models and the observations of GCs, which show a strong bi-modality in metallicity [48]. We also assume that the fraction of low-metallicity GCs is 0.76, since that is the fraction of MWGCs for which [Fe/H] ≤ −0.8.…”

Section: Modelsmentioning

confidence: 99%

Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO

et al. 2015

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The predicted rate of binary black hole mergers from galactic fields can vary over several orders of magnitude and is extremely sensitive to the assumptions of stellar evolution. But in dense stellar environments such as globular clusters, binary black holes form by well-understood gravitational interactions. In this letter, we study the formation of black hole binaries in an extensive collection of realistic globular cluster models. By comparing these models to observed Milky Way and extragalactic globular clusters, we find that the mergers of dynamically-formed binaries could be detected at a rate of ∼ 100 per year, potentially dominating the binary black hole merger rate. We also find that a majority of cluster-formed binaries are more massive than their field-formed counterparts, suggesting that Advanced LIGO could identify certain binaries as originating from dense stellar environments.

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Section: Modelsmentioning

confidence: 99%

Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO

et al. 2015

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“…As was done in Rodriguez et al (2016), we assume that the GC population of the local universe is comprised of ∼ 44% high-metallicity GCs (0.25Z ), and ∼ 56% low-metallicity GCs (0.05Z and 0.01Z ). We further assign to each GC a tidal radius based on its galactocentric distance, which we assume to be correlated to its stellar metallicity based on observations of the Milky Way and other galaxies (Harris 2010). We finally assume a log-normal GC mass function, based on recent observations of the GC luminosity function in brightest-cluster galaxies (Harris et al 2014) and a mass-to-light ratio of 2 for old stellar systems (e.g., Bell et al 2003).…”

Section: Galactic Field and Globular Cluster Modelsmentioning

confidence: 99%

Distinguishing Between Formation Channels for Binary Black Holes With Lisa

Breivik

Rodriguez

Larson

et al. 2016

ApJL

169

150

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The recent detections of GW150914 and GW151226 imply an abundance of stellar-mass binary-blackhole mergers in the local universe. While ground-based gravitational-wave detectors are limited to observing the final moments before a binary merges, space-based detectors, such as the Laser Interferometer Space Antenna (LISA), can observe binaries at lower orbital frequencies where such systems may still encode information about their formation histories. In particular, the orbital eccentricity and mass of binary black holes in the LISA frequency band can be used together to discriminate between binaries formed in isolation in galactic fields and those formed in dense stellar environments such as globular clusters. In this letter, we explore the orbital eccentricity and mass of binary-black-hole populations as they evolve through the LISA frequency band. Overall we find that there are two distinct populations discernible by LISA. We show that up to ∼ 90% of binaries formed either dynamically or in isolation have eccentricities measurable by LISA. Finally, we note how measured eccentricities of low-mass binary black holes evolved in isolation could provide detailed constraints on the physics of black-hole natal kicks and common-envelope evolution.

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“…They are often used to constrain galaxy formation models (e.g. Harris 1991; Ashman & Zepf 1992;Forbes et al 1997;Kissler-Patig 2000;Brodie & Strader 2006;Harris 2010;Muratov & Gnedin 2010;Tonini 2013;Brodie et al 2014, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

Tudorica

Georgiev

Chies-Santos

2015

A&A

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Context. Age, metallicity, and spatial distribution of globular clusters (GCs) provide a powerful tool for reconstructing major starformation episodes in galaxies. IKN is a faint dwarf spheroidal (dSph) in the M 81 group of galaxies. It contains five old GCs, which makes it the galaxy with the highest known specific frequency (S N = 126). Aims. We estimate the photometric age, metallicity, and spatial distribution of the poorly studied IKN GCs. We search SDSS for GC candidates beyond the HST/ACS field of view, which covers half of IKN. Methods. To break the age-metallicity degeneracy in the V −I colour, we used WHT/LIRIS K S -band photometry and derived photometric ages and metallicities by comparison with SSP models in the V, I, K s colour space. Results. IKN GCs' V IK s colours are consistent with old ages (≥8 Gyr) and a metallicity distribution with a higher mean than is typical for such a dSph ([Fe/H] −1.4 +0.6 −0.2 dex). Their photometric mass range (0.5 < M GC < 4 × 10 5 M ) implies an unusually high mass ratio between GCs and field stars, of 10.6%. Mixture model analysis of the RGB field stars' metallicity suggests that 72% of the stars may have formed together with the GCs. Using the most massive GC−SFR relation, we calculated a star formation rate (SFR) of ∼10 M /yr during its formation epoch. We note that the more massive GCs are closer to the galaxy photometric centre. IKN GCs also appear spatially aligned along a line close to the major axis of the IKN and nearly orthogonal to the plane of spatial distribution of galaxies in the M 81 group. We identify one new IKN GC candidate based on colour and the PSF analysis of the SDSS data. Conclusions. The evidence of i) broad and high metallicity distribution of the field IKN RGB stars and its GCs, ii) high fraction, and iii) spatial alignment of IKN GCs supports a scenario for tidally triggered, complex IKN's star formation history in the context of interactions with galaxies in the M 81 group.

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Massive star clusters in galaxies

Cited by 43 publications

References 92 publications

Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO

Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO

Distinguishing Between Formation Channels for Binary Black Holes With Lisa

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

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