Periodic Reporting for period 1 - WINGS (Winds in galaxies)
Reporting period: 2022-09-01 to 2025-02-28
Almost every galaxy in the Universe harbors a supermassive black hole accreting matter (i.e. gas and dust) from its surroundings. As the gas falls toward the supermassive black hole, it forms an accretion disk, which releases enormous amounts of energy in the form of light. The resulting radiation exerts a force that accelerates the interstellar medium gas at very high speeds (up to 1000 km/s, equivalent to about 4 million km/h). This outflowing gas is generally dubbed galactic winds.
In recent years, various theoretical models and cosmological simulations have shown that these flows of matter play a fundamental role in the evolutive process of both the host galaxy and the supermassive black hole that generated them. Nonetheless, from the experimental/observational point of view, the importance of these phenomena is still widely debated and very little is known about galactic winds in the earliest stages of galaxy evolution within the first two billion years of the Universe (i.e. the epoch of fastest growth of supermassive black holes and galaxies and when galactic winds are expected to be more powerful).
To study the properties of distant galaxies and detect galactic winds, spectroscopic observations in the near-infrared wavelength range are essential. However, these observations cannot be performed using ground-based facilities and require space telescopes. In this regard, the launch of the James Webb Space Telescope (JWST) on December 25, 2021, marked a significant advancement in our quest to understand the formation and evolution of first galaxy populations.
The WINGS project exploits JWST data to identify and characterize outflowing gas in the most distant galaxies, building the first census of galactic winds across early cosmic epochs. In parallel, the project focuses on investigating the impact of outflowing gas on the host galaxy in order to quantify the role played by galactic winds in the galaxy formation and evolution processes. Finally, the properties of galactic winds are compared with those expected by state-of-art cosmological simulations to verify the predictions of theoretical models.
In recent years, various theoretical models and cosmological simulations have shown that these flows of matter play a fundamental role in the evolutive process of both the host galaxy and the supermassive black hole that generated them. Nonetheless, from the experimental/observational point of view, the importance of these phenomena is still widely debated and very little is known about galactic winds in the earliest stages of galaxy evolution within the first two billion years of the Universe (i.e. the epoch of fastest growth of supermassive black holes and galaxies and when galactic winds are expected to be more powerful).
To study the properties of distant galaxies and detect galactic winds, spectroscopic observations in the near-infrared wavelength range are essential. However, these observations cannot be performed using ground-based facilities and require space telescopes. In this regard, the launch of the James Webb Space Telescope (JWST) on December 25, 2021, marked a significant advancement in our quest to understand the formation and evolution of first galaxy populations.
The WINGS project exploits JWST data to identify and characterize outflowing gas in the most distant galaxies, building the first census of galactic winds across early cosmic epochs. In parallel, the project focuses on investigating the impact of outflowing gas on the host galaxy in order to quantify the role played by galactic winds in the galaxy formation and evolution processes. Finally, the properties of galactic winds are compared with those expected by state-of-art cosmological simulations to verify the predictions of theoretical models.
The WINGS team focused on the elaboration and analysis of JWST data obtained from the JWST Advanced Deep Extragalactic Survey (JADES) program. In particular, the first six months of the first period were devoted to developing and optimising data processing algorithms and software to calibrate the raw data obtained by NIRSpec, the spectrograph onboard JWST, and produce scientific outputs (i.e. 1D and 2D astrophysical electromagnetic spectra). In detail, the data processing code was used to calibrate more than 5,000 near-infrared spectra of distant galaxies, which were shared with the astronomical community at the end of the period of analysis. The most relevant outcome of the data analysis was the identification of the most distant galaxies and supermassive black holes known to date, which formed when the universe was only 300-400 million years old.
The WINGS team also analysed the scientific products to investigate the incidence of galactic winds and found that they are more frequent in more massive and starbursting galaxies. The analysis of the data also revealed that the most powerful outflows are driven by the radiation emitted from the accretion disk of massive black holes located at the centre of galaxies. Such outflows clean the galaxy from the gas and the formation of new stars in the galaxy is rapidly suppressed in short time scales. This indicates that galaxy evolution is very rapid in the first billion years of the Universe and galaxies might move from a star-forming phase to a dormant or quenched phase faster than what we expected before JWST launch
Finally, the team analysed a set of cosmological zoom-in simulations to compare the observables inferred from the experimental programs with theoretical predictions. The analysis has revealed that the outflows driven by accreting supermassive black holes can trigger the star-formation activity in galaxies located a few kpc scales from the ones hosting a supermassive black hole. By comparing these predictions with experimental data, the team has concluded that supermassive black holes mainly lie in the most massive dark matter haloes, as predicted by the majority of theoretical studies.
The WINGS team also analysed the scientific products to investigate the incidence of galactic winds and found that they are more frequent in more massive and starbursting galaxies. The analysis of the data also revealed that the most powerful outflows are driven by the radiation emitted from the accretion disk of massive black holes located at the centre of galaxies. Such outflows clean the galaxy from the gas and the formation of new stars in the galaxy is rapidly suppressed in short time scales. This indicates that galaxy evolution is very rapid in the first billion years of the Universe and galaxies might move from a star-forming phase to a dormant or quenched phase faster than what we expected before JWST launch
Finally, the team analysed a set of cosmological zoom-in simulations to compare the observables inferred from the experimental programs with theoretical predictions. The analysis has revealed that the outflows driven by accreting supermassive black holes can trigger the star-formation activity in galaxies located a few kpc scales from the ones hosting a supermassive black hole. By comparing these predictions with experimental data, the team has concluded that supermassive black holes mainly lie in the most massive dark matter haloes, as predicted by the majority of theoretical studies.
The discovery of massive galaxies and supermassive black holes formed only a few hundred million years after the Big Bang was an unexpected outcome of the JWST mission, as theoretical models and cosmological simulations had predicted a much slower mass assembly during the early phases of galaxy formation. Actually the number of luminous galaxies identified in the distant universe is about an order of magnitude higher than predicted by these models and this finding has profound implications for our understanding of galaxy and black hole formation, prompting theoretical groups to revise their models.
Another significant achievement is the discovery of quiescent galaxies in the distant universe. This result indicates that some mechanisms, such as galactic outflows, may intervene, halting star-formation activity and accretion of matter onto supermassive black holes. This hypothesis is further supported by the first comprehensive census of outflows in distant galaxies, revealing the considerable impact of ejective feedback mechanisms in the early universe. The rate at which gas is expelled from these galaxies via outflows is approximately one hundred times higher than what is observed in local galaxies. At such a high expulsion rate, the gas reservoirs of galaxies are rapidly depleted, reducing the fuel available for star formation. This accelerated gas depletion explains the presence of non-star-forming galaxies within the first billion years of the universe.
Another significant achievement is the discovery of quiescent galaxies in the distant universe. This result indicates that some mechanisms, such as galactic outflows, may intervene, halting star-formation activity and accretion of matter onto supermassive black holes. This hypothesis is further supported by the first comprehensive census of outflows in distant galaxies, revealing the considerable impact of ejective feedback mechanisms in the early universe. The rate at which gas is expelled from these galaxies via outflows is approximately one hundred times higher than what is observed in local galaxies. At such a high expulsion rate, the gas reservoirs of galaxies are rapidly depleted, reducing the fuel available for star formation. This accelerated gas depletion explains the presence of non-star-forming galaxies within the first billion years of the universe.