We study the topological susceptibility in 2+1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings corresponding to temporal extent of the lattice , N _ { \tau } = 6 , 8 , 10 and 12 .
We observe very distinct temperature dependences of the topological susceptibility in the ranges above and below 250 MeV .
While for temperatures above 250 MeV , the dependence is found to be consistent with dilute instanton gas approximation , at lower temperatures the fall-off of topological susceptibility is milder .
We discuss the consequence of our results for cosmology wherein we estimate the bounds on the axion decay constant and the oscillation temperature if indeed the QCD axion is a possible dark matter candidate .