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

Abstract

Globular clusters 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 Msun have recently been suggested as potential polluters. We investigate the spectral properties of proto-GCs that would host a supermassive star. 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. We computed non-LTE 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 JWST. At an effective temperature of 10000 K, the spectrum of SMSs shows a Balmer break in emission. This feature is due to strong non-LTE 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 m_AB~28-30 between 0.7 and 8 um 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.

20 pages, 22 figures. Accepted in Astronomy & Astrophysics

References in corpus (44)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• On the self-enrichment scenario of galactic globular clusters: Constraints on the IMF
• Gemini and Hubble Space Telescope Evidence for an Intermediate Mass Black Hole in omega Centauri
• Paving the way for the JWST: witnessing globular cluster formation at z>3
• The Evolution of Supermassive Population III Stars
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• Constraining the high redshift formation of black hole seeds in nuclear star clusters with gas inflows
• The E-MOSAICS project: tracing galaxy formation and assembly with the age-metallicity distribution of globular clusters
• The influence of residual gas expulsion on the evolution of the Galactic globular cluster system and the origin of the Population II halo
• A General Abundance Problem for All Self-Enrichment Scenarios for the Origin of Multiple Populations in Globular Clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIX. A Chemical Tagging of the Multiple Stellar Populations Over the Chromosome Maps
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• On the evolution and fate of supermassive stars
• The Final Fates of Accreting Supermassive Stars
• The sizes of $z\sim 6-8$ lensed galaxies from the Hubble Frontier Fields Abell 2744 data
• The MUSE Hubble Ultra Deep Field Survey VI: The Faint-End of the Lya Luminosity Function at 2.91 < z < 6.64 and Implications for Reionisation
• Globular Cluster Systems in Brightest Cluster Galaxies: A Near-Universal Luminosity Function?
• APOGEE Chemical Abundances of Globular Cluster Giants in the Inner Galaxy
• A homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The Northern clusters
• Formation of primordial supermassive stars by burst accretion
• The formation of low metallicity globular clusters in dwarf galaxy mergers
• Formation histories of stars, clusters and globular clusters in the E-MOSAICS simulations
• The spectral evolution of the first Galaxies. III. Simulated James Webb Space Telescope spectra of reionization-epoch galaxies with Lyman continuum leakage
• On the Rotation of Supermassive Stars
• Revisiting nucleosynthesis in globular clusters: the case of NGC 2808 and the role of He and K
• Mass models of NGC 6624 without an intermediate-mass black hole
• Multiple stellar populations and their evolution in globular clusters: A nucleosynthesis perspective
• Radial dependence of line profile variability in seven O9--B0.5 stars
• The Science Case for Multi-Object Spectroscopy on the European ELT
• Gravitational Instability in Radiation Pressure Dominated Backgrounds
• Dynamical Constraints on the Origin of Multiple Stellar Populations in Globular Clusters
• On the Detection of Supermassive Primordial Stars
• On the Detection of Supermassive Primordial Stars. II. Blue Supergiants
• Search Instructions for Globular Clusters in Formation at High Redshifts
• The evolution of the UV luminosity function of globular clusters in the E-MOSAICS simulations
• Magnetic braking of supermassive stars through winds
• Star formation within globular clusters:discrete multiple bursts and top-light mass functions
• Maximally Rotating Supermassive Stars at the Onset of Collapse: Effects of Gas Pressure

Cited by in corpus (14)

• Star clusters near and far; tracing star formation across cosmic time
• The Physics of Star Cluster Formation and Evolution
• JWST UNCOVER: Extremely red and compact object at$z_{\mathrm{phot}}\simeq 7.6$ triply imaged by Abell 2744
• N-enhancement in GN-z11: First evidence for supermassive stars nucleosynthesis in proto-globular clusters-like conditions at high redshift ?
• A first look at the SMACS0723 JWST ERO: spectroscopic redshifts, stellar masses and star-formation histories
• Extreme N-emitters at high-redshift: signatures of supermassive stars and globular cluster or black hole formation in action?
• A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$
• Formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions
• Observable and ionizing properties of star-forming galaxies with very massive stars and different IMFs
• Ionizing photon production of Population III stars: effects of rotation, convection, and initial mass function
• Pulsations of primordial supermassive stars induced by a general relativistic instability; visible to JWST at z$>$12
• JADES reveals a large population of low mass black holes at high redshift
• Could kilomasers pinpoint supermassive stars?
• Search strategies for supermassive stars in young clusters and application to nearby galaxies