how to start a map

edit

i want to add a map node to my robot but I don't where to put it, this is my launch file

<?xml version="1.0"?>
<launch>
<include file="$(find gazebo_ros)/launch/willowgarage_world.launch">
  </include>
  <param name="robot_description" command="cat '$(find robot)/urdf/robot.xacro'"/>

  <arg name="x" default="0"/>
  <arg name="y" default="0"/>
  <arg name="z" default="0.5"/>

  <node name="robot_spawn" pkg="gazebo_ros" type="spawn_model" output="screen"
      args="-urdf -param robot_description -model robot -x $(arg x) -y $(arg y) -z $(arg z)" />

<!-- send fake joint values -->
<node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher">
  <param name="use_gui" value="False"/>
</node>

<!-- Combine joint values -->
<node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"/>
<!-- Show in Rviz   -->
<node name="rviz" pkg="rviz" type="rviz" />

</launch>

when I start a rviz and add map I get the message "No map received" what should I do now?

and when use

rostopic list

I am getting these topics

/clicked_point
/clock
/cmd_vel
/gazebo/link_states
/gazebo/model_states
/gazebo/parameter_descriptions
/gazebo/parameter_updates
/gazebo/set_link_state
/gazebo/set_model_state
/initialpose
/joint_states
/move_base_simple/goal
/odom
/robot/laser/scan
/rosout
/rosout_agg
/tf
/tf_static