Here's why:

* Real Existence: Galaxies are vast collections of stars, gas, dust, and dark matter that exist in the real universe. They can be observed, studied, and even imaged by telescopes.

* Observable Properties: Galaxies have measurable properties like size, shape, mass, and composition, which can be determined through scientific observation and analysis.

* Physical Processes: The processes occurring within galaxies, such as star formation, supernovae, and galactic mergers, are governed by physical laws like gravity and electromagnetism.

Mathematical models are representations of physical objects and processes. They can be used to understand and predict the behavior of galaxies, but they are not the galaxies themselves.

For example, astronomers use mathematical models to simulate the formation and evolution of galaxies. These models incorporate known physical laws and parameters, but they are simplified representations of the complex reality.

So, while we use mathematical models to study and understand galaxies, the galaxies themselves are physical objects that exist independently of our models.