A new catalog of infrared dark clouds
Infrared dark clouds (IRDCs) are dark patches of cold dust and gas seen in the sky against the bright diffuse infrared glow of warm dust in our galaxy. These IRDCs, massive and rich in molecules, are natural sites for star birth—one of the main reasons why astronomers are actively studying them. IRDCs were first detected by two early space infrared missions, the Infrared Space Observatory and the Midcourse Space Experiment, but the IRAC camera on Spitzer revolutionized the field with its dramatically enhanced sensitivity and spatial resolution. IRAC had completed several surveys of the Milky Way before being shut off last February, and astronomers have been using the infrared images to identify and analyze the characteristics of IRDCs. The Submillimeter Array and ALMA facilities, operating with high sensitivity and resolution at submillimeter wavelengths where the cold molecular gas can be characterized, have enabled astronomers to follow up on these newly...