How to add a prefab containing Animation to a GameObject?

I have a gameobject in my scene. And I have a prefab with a particle system animation in it. When I drag&drop the prefab on my gameobject it is added as its child and the animation appears on the object. I need to do the same but from script. I searched a lot and here is my code based on what I found so far.

 GameObject objCandle = GameObject.Find("candle");
 UnityEngine.GameObject obj = (GameObject)Resources.Load("Candle_Fire");
 Debug.Log(obj.name + " " + obj.GetType().ToString());
 GameObject ps_candle = (GameObject)GameObject.Instantiate(obj,
     objCandle.transform.position, objCandle.transform.rotation);
 obj.transform.parent = objCandle.transform;
 ParticleSystem ps = objCandle.GetComponentInChildren<ParticleSystem>();
 ps.Play();

but it is not working. There are no exceptions, I debugged the code. But nothing is working. The animation is not starting. I even tried to make the particle system animation to "Play on Awake" but nothing happened too.

What's wrong?