no subscribed topics in image_pipeline stack

edit

Hello, I am trying to use the image_pipeline nodelets, but when I run any one of them, there are no subscribed topics at all!

This is a really simple example: I launch the nodelet and I can see the published topics, but not the subscribed one. I feel like I'm missing something really simple...

I'm using ROS Hydro, Ubuntu 12.04

Here is my launchfile:

<launch>
  <node pkg="nodelet" type="nodelet" name="nodelet_manager"  args="manager"/>
  <node pkg="nodelet" type="nodelet" name="depth_processing" args="load depth_image_proc/convert_metric nodelet_manager"/>
</launch>

and the rqt_graph:

Thanks for your help!