Finding forming globular clusters at high redshifts

Renzini, A.

doi:10.1093/mnrasl/slx057

Cited by 90 publications

(91 citation statements)

References 37 publications

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“…The general conclusion is that UCD progenitors are detectable using JWST photometry with a ≈ 3h exposure time with promising values of S /N, as already suggested for GCs progenitors by Renzini (2017).…”

Section: Predictions For Jwstsupporting

confidence: 70%

The formation of ultra compact dwarf galaxies and massive globular clusters

Jeřabková

Kroupa

Dabringhausen

et al. 2017

A&A

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The stellar initial mass function (IMF) has been described as being invariant, bottom-heavy, or top-heavy in extremely dense starburst conditions. To provide usable observable diagnostics, we calculate redshift dependent spectral energy distributions of stellar populations in extreme star-burst clusters, which are likely to have been the precursors of present day massive globular clusters (GCs) and of ultra compact dwarf galaxies (UCDs). The retention fraction of stellar remnants is taken into account to assess the mass to light ratios of the ageing star-burst. Their redshift dependent photometric properties are calculated as predictions for James Webb Space Telescope (JWST) observations. While the present day GCs and UCDs are largely degenerate concerning bottom-heavy or top-heavy IMFs, a metallicity-and density-dependent top-heavy IMF implies the most massive UCDs, at ages <100 Myr, to appear as objects with quasar-like luminosities with a 0.1-10% variability on a monthly timescale due to core collapse supernovae.

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Section: Predictions For Jwstsupporting

confidence: 70%

The formation of ultra compact dwarf galaxies and massive globular clusters

Jeřabková

Kroupa

Dabringhausen

et al. 2017

A&A

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“…This method has been proposed by Renzini (2017) and Pozzetti et al (2019) to search for GCs in formation at high red-shift. One of the caveats of this approach is that it does not take the possibly peculiar nature of proto-GCs in their initial or young phase into account, that is, multiple stellar populations and processes or sources that are responsible for these peculiarities.…”

Section: Strategies For and Feasibility Of Direct Observationsmentioning

confidence: 99%

“…Furthermore, clear criteria for identifying proto-GCs and distinguishing them from other "normal" young clusters are required. Renzini (2017) and Pozzetti et al (2019) have investigated the detectability of proto-GCs in the early Universe using evolutionary synthesis models. Pozzetti et al (2019) accounted for " normal" stars in their models, assumed a stellar mass of 2 × 10 6 M for a typical GC at formation, a metallicity of [Z/H]= −1.35 close to the mean of the GCs of the Milky Way, and predicted the detailed photometric properties of these objects.…”

Section: Introductionmentioning

confidence: 99%

Spectral properties and detectability of supermassive stars in protoglobular clusters at high redshift

Martins

Haemmerlé

Charbonnel

2019

A&A

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Context. Globular clusters (GCs) contain multiple stellar populations with peculiar chemical compositions. Pollution of the intracluster gas by an early population of fast-evolving stars is the most common scenario for explaining the observations. Stars with masses in excess of 1000 M have recently been suggested as potential polluters. Aims. We investigate the spectral properties of proto-GCs that would host a supermassive star (SMS). Our main goal is to quantify how such a star would affect the integrated light of the cluster, and to study the detectability of such objects. Methods. We computed nonlocal thermal equilibirum atmosphere models for SMS with various combinations of stellar parameters (luminosity, effective temperature, and mass) and metallicities appropriate for GCs, and we predict their emergent spectra. Using these spectra, we calculated the total emission of young proto-GCs with SMS as predicted in a previously reported scenario, and we computed synthetic photometry in UV, optical, and near-IR bands, in particular for the James Webb Space Telescope (JWST).Results. At an effective temperature of 10000 K, the spectrum of SMSs shows a Balmer break in emission. This feature is due to strong nonlocal thermal equilibrium effects (implied by the high luminosity) and is not observed in "normal" stars. The hydrogen lines also show a peculiar behavior, with Balmer lines in emission while higher series lines are in absorption. At 7000 K, the Balmer break shows a strong absorption. At high effective temperatures, the Lyman break is found in emission. Cool and luminous SMSs are found to dominate the integrated spectrum of the cluster, except for the UV range. The predicted magnitudes of these proto-GCs are mag AB ∼28-30 between 0.7 and 8 µm and for redshifts z ∼ 4 − 10, which is detectable with the JWST. The peculiar observational features of cool SMSs imply that they might in principle be detected in color-color diagrams that probe the spectral energy distribution below and above the Balmer break. Conclusions.Our results show that SMSs should be detectable in proto-GCs if they are luminous and relatively cool. They may be found through deep imaging with the JWST.

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“…The observational investigation of star-formation at high redshift (z 6) at very small physical scales (at the level of star-forming complexes of 200 pc including super star clusters) is a new challenge in observational cosmology (e.g., Rigby et al 2017;Johnson et al 2017;Livermore et al 2015;Vanzella et al 2017b,c;Dessauges-Zavadsky et al 2017;Dessauges-Zavadsky & Adamo 2018;Cava et al 2018). Thanks to strong gravitational lensing, the possibility to E-mail: eros.vanzella@oabo.inaf.it catch and study globular clusters precursors (GCP) is becoming a real fact, both with statistical studies (e.g., Renzini 2017;Boylan-Kolchin 2018;Vanzella et al 2017b;Elmegreen et al 2012) and by inferring the physical properties of individual objects (e.g., Vanzella et al 2017b,c). The luminosity function of forming GCs has also been addressed for the first time (Bouwens et al 2018;Boylan-Kolchin 2018) and their possible contribution to the ionising background is now under debate (e.g., Ricotti 2002;Schaerer & Charbonnel 2011;Katz & Ricotti 2013;Boylan-Kolchin 2018).…”

Section: Introductionmentioning

confidence: 99%

Massive star cluster formation under the microscope atz = 6

Vanzella¹,

Calura²,

Meneghetti³

et al. 2018

Monthly Notices of the Royal Astronomical Society

122

138

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We report on a superdense star-forming region with an effective radius (R e ) smaller than 13 pc identified at z=6.143 and showing a star-formation rate density Σ SF R ∼ 1000 M yr −1 kpc −2 (or conservatively > 300 M yr −1 kpc −2 ). Such a dense region is detected with S/N 40 hosted by a dwarf extending over 440 pc, dubbed D1. D1 is magnified by a factor 17.4(±5.0) behind the Hubble Frontier Field galaxy cluster MACS J0416 and elongated tangentially by a factor 13.2±4.0 (including the systematic errors). The lens model accurately reproduces the positions of the confirmed multiple images with a r.m.s. of 0.35 . D1 is part of an interacting star-forming complex extending over 800 pc. The SED−fitting, the very blue ultraviolet slope (β −2.5, F λ ∼ λ β ) and the prominent Lyα emission of the stellar complex imply that very young (< 10 − 100Myr), moderately dust-attenuated (E(B-V)<0.15) stellar populations are present and organised in dense subcomponents. We argue that D1 (with a stellar mass of 2 × 10 7 M ) might contain a young massive star cluster of M 10 6 M and M U V −15.6 (or m U V = 31.1), confined within a region of 13 pc, and not dissimilar from some local super star clusters (SSCs). The ultraviolet appearance of D1 is also consistent with a simulated local dwarf hosting a SSC placed at z=6 and lensed back to the observer. This compact system fits into some popular globular cluster formation scenarios. We show that future high spatial resolution imaging (e.g., E−ELT/MAORY-MICADO and VLT/MAVIS) will allow us to spatially resolve light profiles of 2-8 pc.

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Finding forming globular clusters at high redshifts

Cited by 90 publications

References 37 publications

The formation of ultra compact dwarf galaxies and massive globular clusters

The formation of ultra compact dwarf galaxies and massive globular clusters

Spectral properties and detectability of supermassive stars in protoglobular clusters at high redshift

Massive star cluster formation under the microscope atz = 6

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