Astronomy: abundance, concentration, density

[Puchinita5]

Homework Statement

Hi. I feel like this is probably very basic. Basically, I'm trying to understand how

surface density * concentration = abundance


I'm reading about gas surface density in the galaxy and its relationship to star formation, gas ejection etc. And we are given an equation that states

d(gas surface density)/ dt = rate of gas ejection - rate of star formation

then it goes on to say that the "abundance of a nuclide in the Interstellar Medium is the concentration times the density"

and now they do a proof where d(surface density * concentration)/dt is supposed to be the rate of change of the element's abundance.


I'm not understanding how multiplying a concentration by surface density would give an abundance. Can someone help explain this?

Homework Equations

The Attempt at a Solution

 

[Nino MMP]

Abundance is defined as the relative amount of a given element or compound in a particular environment. In the context of interstellar medium, it refers to the relative amount of nuclide present in the gas clouds. Surface density is the amount of mass per unit area. It is a measure of the thickness of a material on a surface. Concentration can be thought of as the amount of a certain element or compound within a given volume. When you multiply the surface density by the concentration, you get the amount of the element or compound per unit area. This is the same as the abundance of the nuclide in the interstellar medium.