AGN wind scaling relations and the co-evolution of black holes and galaxies (1702.04507v1)

Abstract: Feedback from accreting SMBHs is often identified as the main mechanism responsible for regulating star-formation in AGN host galaxies. However, the relationships between AGN activity, radiation, winds, and star-formation are complex and still far from being understood. We study scaling relations between AGN properties, host galaxy properties and AGN winds. We then evaluate the wind mean impact on the global star-formation history, taking into account the short AGN duty cycle with respect to that of star-formation. We first collect AGN wind observations for 94 AGN with detected massive winds at sub-pc to kpc spatial scales. We then fold AGN wind scaling relations with AGN luminosity functions, to evaluate the average AGN wind mass-loading factor as a function of cosmic time. We find strong correlations between the AGN molecular and ionised wind mass outflow rates and the AGN bolometric luminosity. The power law scaling is steeper for ionised winds (slope 1.29+/-0.38) than for molecular winds (0.76+/-0.06), meaning that the two rates converge at high bolometric luminosities. The molecular gas depletion timescale and the molecular gas fraction of galaxies hosting powerful AGN winds are 3-10 times shorter and smaller than those of main-sequence galaxies with similar SFR, stellar mass and redshift. These findings suggest that, at high AGN bolometric luminosity, the reduced molecular gas fraction may be due to the destruction of molecules by the wind, leading to a larger fraction of gas in the atomic ionised phase. The AGN wind mass-loading factor $\eta=\dot M_{OF}/SFR$ is systematically higher than that of starburst driven winds. Our analysis shows that AGN winds are, on average, powerful enough to clean galaxies from their molecular gas only in massive systems at z<=2, i.e. a strong form of co-evolution between SMBHs and galaxies appears to break down for the least massive galaxies.

• The paper establishes that AGN wind mass outflow rates strongly correlate with bolometric luminosity, with molecular and ionized winds following distinct power-law slopes.
• The analysis shows that galaxies with strong AGN winds experience molecular gas depletion times 3–10 times shorter, significantly influencing their star formation rates.
• The study suggests that AGN winds drive gas phase transitions and regulate molecular reservoirs, playing a crucial role in galaxy evolution at redshifts below 2.

AGN Wind Scaling Relations and the Co-evolution of Black Holes and Galaxies

The paper of Active Galactic Nuclei (AGN) winds has evolved significantly, offering insights into the complex relationship between supermassive black holes (SMBHs) and their host galaxies. This paper explores the scaling relations between AGN properties, host galaxy characteristics, and AGN-driven winds, aiming to elucidate the influence of these winds on the star formation history of galaxies.

The paper is anchored on a comprehensive dataset encompassing 94 AGNs with detected massive winds on scales ranging from sub-parsec to kiloparsec. The authors meticulously analyze these scaling relations to assess the impact of AGN winds on the star-formation histories of galaxies. Their analysis reveals some salient correlations and implications for our understanding of galaxy evolution.

Key Findings and Numerical Results

1. Wind-AGN Bolometric Luminosity Relations:
   • There is a strong correlation between the mass outflow rates of both molecular and ionized winds and AGN bolometric luminosity. Molecular wind mass outflow rates follow a power-law relation with a slope of 0.76 ± 0.06, while ionized winds have a steeper slope of 1.29 ± 0.38. This suggests different efficiencies or phases for these winds at different luminosities.
2. Wind Kinetic Power and Gas Phase Transitions:
   • Ionized wind kinetic power shows a slope of 1.50 ± 0.34 with AGN luminosity. The ionized winds converge with molecular winds at high luminosities, suggesting transitions from molecular to ionized phases as winds become more powerful.
3. Depletion Timescales:
   • Galaxies hosting AGNs with strong winds exhibit molecular gas depletion timescales 3-10 times shorter than those without such winds, indicating a significant reduction in available star-forming material.
4. Mass-Loading Factor:
   • The paper indicates that the mass-loading factor, defined as the wind mass outflow rate divided by the star formation rate (SFR), is systematically higher in AGN-driven winds than in starburst-driven winds. This suggests AGN winds play a dominant role in regulating the molecular gas reservoir.
5. Cosmological Implications:
   • The paper finds that AGN winds are potent enough to significantly reduce molecular gas in massive galaxies (M_* > 10^11 M_⊙) at redshifts z < 2, insinuating a pronounced influence on the co-evolution of galaxies and their central SMBHs in such systems.

Implications and Future Directions

The implications of this research extend to both theoretical models and observational strategies. From a theoretical perspective, the results necessitate revising galaxy evolution models to incorporate AGN wind feedback mechanisms more effectively, particularly in varying feedback strengths and forms at different luminosities and redshifts.

Practically, this paper signals a need for more comprehensive surveys focusing on molecular and ionized winds across diverse AGN populations and environments. Future telescopic advancements, especially in infrared and millimeter wavelengths (e.g., ALMA), will be crucial in resolving these wind components and unraveling their roles over cosmic time.

Speculation on Future Developments

Given the insights from this paper, future developments in AI and machine learning could play a transformative role in this field. Large datasets from surveys could be leveraged to train sophisticated models, capable of teasing out subtle patterns between AGN winds and star formation. Further, AI-driven simulations could more accurately track the multi-phase nature of these winds and their interactions with the interstellar medium (ISM).

In conclusion, this paper significantly advances our understanding of AGN winds, highlighting their intricate roles in regulating galaxy evolution. As observational capabilities expand, the interplay between AGNs and their host galaxies will undoubtedly become clearer, offering more refined insights into our cosmological history.