What does IFN mean in UNCLASSIFIED

An Integrated Flux Nebula (IFN) is a type of emission nebula characterized by faint, diffuse light that appears to be integrated with the background starlight. Unlike discrete emission nebulae, such as planetary nebulae, IFNs lack sharp boundaries and blend seamlessly with the surrounding interstellar medium.

IFNs are formed by the ionization of interstellar gas by low-energy photons emitted from nearby stars. These photons have insufficient energy to create H II regions (the ionized zones surrounding massive stars), and instead produce a more diffuse, widespread ionization.

IFNs typically have faint surface brightness and a diffuse, irregular morphology. They emit light primarily in the Hα and [N II] lines, indicating the presence of ionized hydrogen and nitrogen gas. IFNs often contain embedded star-forming regions and are associated with molecular clouds.

IFNs provide insights into the physical properties of interstellar gas and the star formation process. They are used to study the properties of molecular clouds, the distribution of ionized gas, and the interaction between starlight and interstellar gas.

IFNs are identified through their faint Hα and [N II] emission. They are often observed using narrowband filters that isolate these specific wavelengths. IFNs can also be detected using radio observations, which reveal the presence of molecular clouds associated with them.

Yes, IFNs are found in a variety of galaxies, including our own Milky Way. They are typically associated with regions of active star formation and are most commonly observed in spiral and irregular galaxies.