Astrônomos using Telescópio Espacial James Webb (JWST) identified a stellar bar in the massive galaxy GN20. Observada just 1.5 billion years after Big Bang, this discovery challenges expectations established by the standard model of galaxy formation. The study, led by Leindert A. Boogaard, of Universidade of Leiden, was submitted to the preprint server arXiv on May 14, highlighting a phenomenon previously considered unlikely in such young galaxies.
Stellar Barras are elongated structures of stars that cross the center of a galaxy, functioning as cosmic funnels. Elas funnel gas into the galactic core, which intensifies star formation, fuels central black holes and contributes to the construction of dense cores. In the nearby universe, these bars are common, including in Via Láctea, but their formation is considered a slow process, which takes billions of years to develop.
Descoberta and Observação of GN20
The galaxy GN20 is a massive, gas-rich system located at a redshift of 4, making it distant and faint. Apesar from being shrouded in dust, JWST’s mid-infrared instrument (MIRI) and near-infrared camera (NIRCam) allowed penetration of this layer. Essas tools have revealed the galaxy’s internal structure in unprecedented detail.
Isophoto analysis, which measures how the galaxy’s light brightness stretches and rotates from the center outward, showed a sharp bar structure. Esta bar extends seven kiloparsecs from end to end. An independent mathematical analysis of the light pattern autonomously confirmed the detection. High-resolution submillimeter Observações images from Northern Extended Millimeter Array (NOEMA) corroborated the presence of a bar-shaped feature in the mapped dust, demonstrating a strong alignment between the stellar bar and the dust bar.
Barra Estelar Desafia Modelos Teóricos
The detection of a stellar bar in GN20 is notable because, according to existing theories, its existence should be unlikely for at least three fundamental reasons. The researchers indicate that the primitive galaxy, rich in gas, would have unfavorable conditions for the formation of such structures.
- Colapso Estrutural:Barras stars that form normally are considered resilient, but the initial conditions of the universe suggested that they would collapse under their own weight.
- Tempo from Crescimento:Growing a bar to seven kiloparsecs would take billions of years, a period incompatible with the observed age of GN20 (1.5 billion years after Big Bang).
- Supressão by Gás:The abundant amount of gas in early galaxies should have suppressed or delayed the formation of bars, according to standard models.
The team, however, points out that all these obstacles can be overcome by the presence of highly turbulent gas throughout the inner disk with a high gas fraction.
Turbulência from Gás and Formação from Barra
Research by Boogaard et al. suggests that the key to the formation of the stellar bar in GN20 lies in the condition of its gas. Turbulence and the high fraction of gas in the galaxy’s inner disk would have allowed the bar to stabilize and grow. Esta is a crucial explanation that integrates observations with theory, sharpening our understanding of the early evolution of galaxies.
Embora researchers mention uncertainties such as estimating the stellar mass of the bar and core regions due to the extreme amount of dust, the main conclusion remains. Eles claim that GN20 is a gas-rich system and the star bar is real. JWST’s MIRI instrument was instrumental in making the dust transparent and revealing these complex internal structures.
Implicações to Evolução Galáctica
Detailed observations of GN20 also indicate where star formation is concentrated. At the point where the bar meets the southern outer disk, gas accumulates and triggers a hot spot of intense star formation. At the center, the bar draws material inward, fueling a nuclear stellar explosion and possibly a supermassive black hole. Este factor is likely crucial to GN20’s extraordinary star formation rate, which exceeds 1,000 solar masses per year.
Essa’s high rate of star formation may be driven by the bar that funnels gas and dust to the center, where it triggers an intense nuclear stellar explosion in the gas-rich disk and fuels the potential active galactic nucleus. The discovery suggests that galaxies like GN20 may not simply be a phase in galactic evolution. Bar-driven star formation could explain the enigma of how the massive, dead elliptical galaxies observed in the current universe reached this state, and why some of them appear to have become extinct so early. Este finding represents a significant missing link in understanding the evolution of galaxies.