How early starburst regions and black holes regulated further star formation
During the early cosmic dawn, the first stars and primordial black holes were not just passive inhabitants of the Universe. They performed active role, introducing abundant energy and radiation quantity. These processes, collectively called feedback, have had a significant impact on the star formation cycle, either suppressing or promoting further gas collapse in different regions. In this article, we examine how radiation, winds and outflows mapped the evolution of galaxies from regions of early star "explosion" and emerging black holes.
1. Initial background: first light sources
1.1 From the Dark Ages to the Enlightenment
After the Dark Ages of the Universe (the era after recombination, when there were no bright sources of light), Population III stars originated in mini-halos containing dark matter and primordial gas. Often these stars were very massive and extremely hot, emitting intense ultraviolet light. At about the same time, or shortly thereafter, supermassive black holes (SMBH) The nuclei may have begun to form—perhaps through direct collapse, or perhaps from the remnants of massive Population III stars.
1.2 Why is feedback important?
In an expanding Universe, star formation occurs when gas is able to cool and gravitationally collapse. However, if local energy sources — stars or black holes — interrupts the integrity of gas clouds or increases their temperature, future star formation may be suppressed or delayed. On the other hand, under certain conditions, shock waves and outflows may to compress regions of gas, promoting new star formation. These positive and negative feedback loops Understanding this is crucial to creating a realistic picture of early galaxy formation.
2. Radiation feedback
2.1 Ionizing photons from massive stars
Massive, metal-free Population III stars generated strong Lyman continuum photons that could ionize neutral hydrogen. In this way, they created a H II area — ionized bubbles:
- Heating and pressure: Ionized gas reaches ~104 K, characterized by high thermodynamic pressure.
- Photoevaporation: Surrounding neutral gas clouds can be "vaporized" when ionizing photons strip electrons from hydrogen atoms, heating and scattering them.
- Inhibition or stimulation: On a small scale, photoionization can suppress fragmentation by increasing the local Jeans mass, but on larger scales ionization fronts can to encourage the compression of neighboring neutral clouds, thus initiating star formation.
2.2 Lyman–Werner radiation
In the early Universe Lyman–Werner (LW) photons, with energies of 11.2–13.6 eV, were important for the breakdown of molecular hydrogen (H2), which was the main cooler in the metal-poor environment. If the early stellar region or the nascent black hole emitted LW photons:
- H2 destruction: If H2 disassembled, it becomes difficult for the gas to cool.
- Star formation postponement: Without H2, the collapse of gas in the surrounding mini-halos may be suppressed, delaying new star formation.
- "Inter-halic" effect: LW photons can travel long distances, so a single bright source can affect star formation in nearby haloes.
2.3 Regionalization and large-scale heating
At around z ≈ 6–10, the total radiation from early stars and quasars reionized the intergalactic medium (IGM). During this process:
- IGM heating: Once ionized, hydrogen reaches ~104 K, increasing the minimum halo mass threshold required for gravitational retention of gas.
- Slowing down the growth of galaxies: Low-mass halos may no longer hold enough gas to form stars, so star formation shifts to more massive structures.
So regionalization acts as a large-scale feedback, transforming the Universe from a neutral, cool cosmos to an ionized, hotter medium and changing the conditions for future star formation.
3. Stellar winds and supernovae
3.1 Winds of massive stars
Even before stars explode as supernovae, they can emit powerful stellar windsMassive metal-free (Population III) stars may have had slightly different wind properties than modern metal-rich stars, but even with low metallization, strong winds are possible, especially for very massive or rotating stars. These winds can:
- Expel gas from a mini-halo: If the halo's gravitational potential is shallower, winds can blow away a significant portion of the gas.
- Create "bubbles": Stellar wind "bubbles" carve out cavities in the interstellar medium, changing the course of star formation rates.
3.2 Supernova explosions
As massive stars reach the end of their lives, they experience core collapse or pair instability. supernovae unleashes a giant kinetic energy quantity (~1051 erg for simple nuclear collapse, maybe even more in the case of pair instability). So:
- Shock waves: They fly outward, heating and possibly stopping further gas collapse.
- Chemical enrichment: Newly synthesized heavier elements are ejected, dramatically changing the chemistry of the ISM. Metals improve cooling, thus promoting lower mass future star formation.
- Galactic outflows: In larger halos or in emerging galaxies, repeated supernovae can create wider outflows, ejecting material far into intergalactic space.
3.3 Positive vs. negative feedback
Although supernova shock waves can disperse gas (negative feedback), they can also to compress surrounding clouds, promoting gravitational collapse (positive feedback). The specific result depends on local conditions — gas density, halo mass, shock wave geometry, etc.
4. Early black hole feedback
4.1 Accretion light and winds
Without stellar feedback, accreting black holes (especially evolving into quasars or AGN) leads to strong feedback effects through radiation pressure and wind:
- Radiation pressure: The rapid fall of mass into a black hole effectively converts the mass into energy, emitting intense X-rays and UV waves. This can ionize or heat the surrounding gas.
- AGN outflows: Quasar winds and jets can "sweep" gas across scales of up to several kiloparsecs, controlling star formation in the host galaxy.
4.2 The origins of quasars and proto-AGN
In the early stages, black hole seeds (e.g., remnants of Population III stars or direct-collapse black holes) may not have been bright enough to dominate the feedback effects beyond the mini-halo. However, as they grow by accretion or mergers, some may become bright enough to significantly affect the IGM. Early quasar-like sources:
- Promotes reionization: The harder radiation from accreting black holes can ionize helium and hydrogen more strongly at greater distances.
- Stifles or encourages star formation: Powerful outflows or jets can inflate or compress gas in surrounding star-forming clouds.
5. The broad impact of early feedback
5.1 Regulation of galaxy growth
The overall feedback between stellar populations and black holes defines the galaxy's "baryon cycle" — i.e. how much gas remains, how long it takes to cool down and when it is blown out:
- Gas inflow suppression: If outflows or radiative heating prevent gas from being retained, star formation remains scarce.
- The way to bigger halls: Over time, more massive halos form with deeper gravitational potential, capable of retaining gas even with feedback.
5.2 Enrichment of the space network
Winds driven by supernovae and AGN can carry metals to space network, spreading them out over the scale of filaments and voids. This ensures that galaxies that form later will already find some enriched gas.
5.3 Determining the pace and structure of regionalization
Observations show that reionization probably happened in a patchwork way, with ionized "bubbles" expanding around the haloes of early stars and the foci of AGN. Feedback—especially from bright sources—significantly affects how quickly and evenly the IGM becomes ionized.
6. Evidence and data from observations
6.1 Metal-poor galaxies and dwarfs
Modern astronomers study local analogs—such as metal-poor dwarf galaxies—to understand how feedback affects low-mass systems. The intense stellar "explosions" observed in many places blow up a large portion of the interstellar material. This is similar to a possible scenario in early mini-halos, after the onset of supernovae.
6.2 Observations of quasars and gamma-ray bursts (GRBs)
Gamma ray bursts, arising from the collapse of massive stars at high redshift, can help study the gas content and ionization level of the environment. Meanwhile quasar absorption lines at different redshifts show the amount of metals and temperature in the IGM, allowing us to estimate how much stellar outflows have affected the surrounding space.
6.3 Emission line markings
Spectral features (e.g. Lyman–alpha emission, metal lines like [O III], C IV) help reveal winds whether superbubbles presence in galaxies appearing at high redshift. James Webb Space Telescope (JWST) capable of detecting these features much more clearly even in faint early galaxies.
7. Simulations: from mini-halls to cosmic scales
7.1 Hydrodynamics + radiative transfer
New generation cosmological simulations (e.g., FIRE, IllustrisTNG, CROC) connects hydrodynamics, stargazing and radiation transferto be able to model feedback consistently.This allows scientists to:
- To determine how ionizing radiation from massive stars and AGN interacts with gas at various scales.
- To record the occurrence of leaks, their propagation and impact on subsequent gas accretion.
7.2 Sensitivity to model assumptions
Results vary greatly depending on:
- Stellar Initial Mass Functions (IMFs): The mass distribution (slope, boundaries) determines how many massive stars will form, how much energy will be emitted, or how many supernovae will occur.
- AGN feedback recipes: Different methods of interaction of accretion energy with gas determine different intensities of outflows.
- Mixing metals: How quickly metals are distributed determines the local cooling time, which has a significant impact on subsequent star formation.
8. Why feedback drives early cosmic evolution
8.1 Directionality of the formation of the first galaxy
Feedback is not just a side effect; it is main a factor that explains how small haloes coalesce and grow into recognizable galaxies. Outflows from a single massive star cluster or a nascent black hole can lead to large local changes in star formation efficiency.
8.2 Zone speed control
Because the feedback controls the number of stars in small haloes (and therefore the amount of ionizing photons), it is closely related to the density of the Universe. reionization Under strong feedback, low-mass galaxies may form fewer stars, slowing down reionization; under weaker feedback, many small systems may contribute to faster reionization.
8.3 Setting the conditions for planetary and biological evolution
On an even larger cosmic scale, feedbacks determine the distribution of metals, and metals are essential for planet formation and, perhaps, life. Thus, early feedback episodes helped the Universe not only energetically but also chemically, thus setting the stage for the development of increasingly complex astrophysical structures.
9. Future perspective
9.1 Next-generation observatories
- JWST: By studying the era of reionization, JWST's infrared instruments will reveal dust-covered regions, reveal winds from stellar explosions, and reveal AGN feedback during the first billion years.
- Extremely Large Telescopes (ELT): High-resolution spectroscopy will allow for even more detailed analysis of wind and outflow signatures (metal lines) at high redshift.
- SKA (Square Kilometre Array): 21 cm tomography may be able to capture how ionized regions expanded under the influence of stellar and AGN feedback.
9.2 More advanced simulations and theory
Higher resolution simulations with more advanced physics (e.g., better treatment of dust, turbulence, magnetic fields) will allow us to look deeper into the complexity of feedback. The coherence of theory and observations promises to find answers to pressing questions — for example, what magnitude of winds could have been generated by black holes in early dwarf galaxies or how short-lived stellar "explosions" changed the cosmic web.
10. Conclusion
Early times feedback — through radiation, wind and supernova/AGN outflows — acted like cosmic "gatekeepers," setting the rhythm of star formation and the development of large structures. Photoionization, which suppresses the collapse of neighboring halos, and powerful outflows, by blowing or compressing the gas, created a confusing positive and negative a mosaic of feedback loops. While these phenomena are important on local scales, they are also reflected in the evolving cosmic web, affecting reionization, chemical enrichment, and hierarchical growth of galaxies.
By combining theoretical models, high-resolution simulations, and discoveries from advanced telescopes, astronomers are increasingly gaining insight into how these early reversible processes led the Universe into the era of bright galaxies, creating the conditions for even more complex astrophysical formations, including the chemistry necessary for planets and perhaps life.
References and further reading
- Ciardi, B., & Ferrara, A. (2005). "The First Cosmic Structures and Their Effects." Space Science Reviews, 116, 625–705.
- Bromm, V., & Yoshida, N. (2011). “The First Galaxies.” Annual Review of Astronomy and Astrophysics, 49, 373–407.
- Muratov, A. L., et al. (2015). "Gusty, gaseous flows in the FIRE simulations: galactic winds driven by stellar feedback." Monthly Notices of the Royal Astronomical Society, 454, 2691–2713.
- Dayal, P., & Ferrara, A. (2018). "Early galaxy formation and its large-scale effects." Physics Reports, 780–782, 1–64.
- Hopkins, P. F., et al. (2018). "FIRE-2 Simulations: Physics, Numerics, and Methods." Monthly Notices of the Royal Astronomical Society, 480, 800–863.