Dust ridge clouds in absorption against the infrared background (GLIMPSE RGB image: blue = 3.6 μm, green = 4.5 μm, red = 8.0 μm). The contour shows dust emission at 20% of the peak, with 1% corresponding to 2σ. A strong correlation exists between the distribution of the dust emission and the shape of the infrared dark clouds. Green crosses and upper case letters mark the positions of the radio sources detected. Strong infrared emission is seen at the positions of the radio sources A, D, and E.