Given $\int_{-\infty }^{\infty } e^{-x^{2}} dx = \sqrt{\pi }.$
If $a$ and $b$ are positive integers, the value of $\int_{-\infty }^{\infty } e^{-a\left ( x+b \right )^{2}} dx$ is _______________.
- $\sqrt{\pi a}$
- $\sqrt{\frac{\pi }{a}}$
- $b\sqrt{\pi a}$
- $b\sqrt{\frac{\pi }{a}}$