Infrared excess emission

Definition

Infrared excess emission refers to the phenomenon where astronomical objects, such as active galactic nuclei (AGN), emit more infrared radiation than what is expected based on their optical or ultraviolet light. This excess emission is often attributed to the presence of warm dust surrounding the central supermassive black hole, which absorbs high-energy radiation and re-emits it in the infrared spectrum. Understanding this emission helps astronomers analyze the characteristics and environments of AGN.

5 Must Know Facts For Your Next Test

1. Infrared excess emission can indicate the presence of heated dust that surrounds the supermassive black hole in an AGN, which can reach temperatures of hundreds to thousands of degrees Kelvin.
2. This excess can be used to study the structure and composition of the torus, helping to reveal information about how matter interacts with the black hole.
3. Infrared observations allow astronomers to detect AGN that might be hidden in optical wavelengths due to dust obscuration.
4. The amount and shape of infrared excess emission can vary significantly among different types of AGN, providing insight into their physical properties and evolutionary stages.
5. Understanding infrared excess emission is essential for modeling the overall energy output and understanding the role of AGN in galaxy formation and evolution.

Review Questions

• How does infrared excess emission provide insight into the physical conditions around active galactic nuclei?
  • Infrared excess emission reveals the presence of warm dust surrounding supermassive black holes in active galactic nuclei. By analyzing this emission, astronomers can infer the temperature and density of the dust, which indicates how matter interacts with the black hole. This understanding also helps in identifying processes like accretion and outflow, ultimately painting a clearer picture of the environment surrounding AGN.
• Discuss the significance of dust tori in relation to infrared excess emission and their role in shaping our understanding of AGN.
  • Dust tori are crucial for understanding infrared excess emission since they absorb high-energy radiation from the central supermassive black hole and re-emit it in the infrared spectrum. The properties of these tori influence the observed spectral energy distributions of AGN, allowing researchers to classify different types based on their infrared characteristics. This relationship enhances our comprehension of how material is distributed around black holes and impacts their growth and activity.
• Evaluate how studying infrared excess emission can influence our understanding of galaxy evolution and the role AGN play within it.
  • Studying infrared excess emission offers insights into the interplay between supermassive black holes and their host galaxies. This research can reveal how AGN contribute to star formation suppression or enhancement through feedback mechanisms related to outflows. By linking these phenomena to the overall energy output observed in various wavelengths, astronomers can better understand the evolutionary paths that galaxies take over cosmic time and how AGN drive significant changes within those galaxies.

Related terms

Active Galactic Nuclei (AGN): The extremely bright and energetic centers of some galaxies, powered by accretion of material onto supermassive black holes.

Dust Torus: A dense region of dust surrounding the central black hole in many AGN, which plays a crucial role in obscuring certain wavelengths of light and contributes to infrared excess emission.

Spectral Energy Distribution (SED): A representation of an object's energy output across different wavelengths, used to analyze and understand its emission characteristics, including infrared excess.