In the Tully-Fisher relation, the scatter is minimized at which wavelength?
* Red
* Blue
* Infrared
* UV
To determine at which wavelength the scatter is minimized in the Tully-Fisher relation, we need to understand what the Tully-Fisher relation is and how it is related to different wavelengths.
The Tully-Fisher relation is an empirical relationship between the luminosity (or absolute magnitude) of a spiral galaxy and its rotational velocity. It states that the brighter a spiral galaxy is, the faster its stars rotate. This relation can be used to estimate the intrinsic brightness or mass of a spiral galaxy.
The scatter in the Tully-Fisher relation refers to the spread of data points around the best-fit line representing the relationship between luminosity and rotational velocity. A smaller scatter indicates a stronger correlation between these variables.
The scatter in the Tully-Fisher relation is minimized at the wavelength where the luminosity of a galaxy is best traced. Different wavelengths of light can trace different components of a galaxy, such as its stars or gas. The choice of wavelength depends on which component one wants to measure and which provides the most accurate estimation of the galaxy's intrinsic brightness.
In the case of the Tully-Fisher relation, the scatter is typically minimized in the infrared wavelengths. This is because infrared light has several advantages for studying the overall luminosity of a galaxy:
1. Obscuration: Infrared light can penetrate the dust and gas that often obscures visible light, allowing a clearer view of the entire galaxy.
2. Aging: Infrared light is less affected by the age of stellar populations, which can introduce uncertainties in visible light measurements. Older stellar populations emit more light in the infrared, making it a more reliable indicator of a galaxy's total luminosity.
3. Mass tracing: Infrared radiation is often emitted by cool stars, which tend to trace the bulk of a galaxy's mass more accurately than hot stars that emit mostly in the ultraviolet or optical range.
Therefore, the scatter in the Tully-Fisher relation is minimized at infrared wavelengths.