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<p>The assembly of stellar-dominated cores in elliptical galaxies is key to understanding how cosmic structures evolved. Gravitational lensing offers unique insights into the nature of their stars. Here we report the discovery of an extremely compact quadruply lensed quasar (radius ~0.2″), whose lensing galaxy at a redshift of 1.055 (5.5 billion years after the Big Bang) features a lensing mass of only ~2 × 10<sup>10</sup> <i>M</i><sub>⊙</sub>. Bayesian analysis, based on the exceptional properties of the system and standard scaling relations, makes it possible to sample the central galactic initial mass function with great accuracy and in a previously uncharted regime in terms of mass and redshift. We find it to be consistent with the initial mass function of the Milky Way while excluding bottom-heavy functions. This indicates that the core either grew slowly or underwent early disruptive events altering its stellar build-up, potentially challenging the classical view in which bulges form rapidly and remain unchanged by later interactions.</p>

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Milky-Way-like stars in a galaxy core 8 billion years ago revealed by gravitational lensing

  • 期刊论文

  • 发表日期：

    2026年4月2日

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  • Quirino D’Amato,
  • Filippo Mannucci,
  • Alessandro Sonnenfeld,
  • Martina Scialpi,
  • James W. Nightingale,
  • Cristiana Spingola,
  • Stefano Zibetti,
  • Alessandro Marconi,
  • Piero Rosati,
  • Cosimo Marconcini,
  • Guido Agapito,
  • Anna Gallazzi,
  • Enrico Di Teodoro,
  • Gloria Andreuzzi,
  • Francesco Belfiore,
  • Elena Bertola,
  • Caterina Bracci,
  • Stefano Carniani,
  • Elisa Cataldi,
  • Avinanda Chakraborty,
  • Matteo Ceci,
  • Claudia Cicone,
  • Anna Ciurlo,
  • Giovanni Cresci,
  • Alessandra De Rosa,
  • Elisa Di Carlo,
  • Anna Feltre,
  • Michele Ginolfi,
  • Isabella Lamperti,
  • Bianca Moreschini,
  • Emanuele Nardini,
  • Michele Perna,
  • Elisa Portaluri,
  • Khatun Rubinur,
  • Paolo Saracco,
  • Paola Severgnini,
  • Vincenzo Testa,
  • Giulia Tozzi,
  • Giacomo Venturi,
  • Lorenzo Ulivi,
  • Cristian Vignali,
  • Maria Vittoria Zanchettin,
  • Antonio Pepe

摘要

The assembly of stellar-dominated cores in elliptical galaxies is key to understanding how cosmic structures evolved. Gravitational lensing offers unique insights into the nature of their stars. Here we report the discovery of an extremely compact quadruply lensed quasar (radius ~0.2″), whose lensing galaxy at a redshift of 1.055 (5.5 billion years after the Big Bang) features a lensing mass of only ~2 × 1010 M⊙. Bayesian analysis, based on the exceptional properties of the system and standard scaling relations, makes it possible to sample the central galactic initial mass function with great accuracy and in a previously uncharted regime in terms of mass and redshift. We find it to be consistent with the initial mass function of the Milky Way while excluding bottom-heavy functions. This indicates that the core either grew slowly or underwent early disruptive events altering its stellar build-up, potentially challenging the classical view in which bulges form rapidly and remain unchanged by later interactions.