The Milky Way Project: Bridging Intermediate- and High-mass Star Formation with the MIRION Catalog of Yellowballs

We describe the construction and use of the Mid-InfraRed Interstellar Objects and Nebulae (MIRION) catalog, which was compiled from 6176 objects identified as “yellowballs” (YBs) by participants in the Milky Way Project. The majority of YBs are compact photodissociation regions generated by intermediate- and high-mass young stellar objects that are embedded in star-forming clumps ranging in mass from 10 to 10 6 M ⊙ and luminosity from 10 to 10 4 L ⊙ . The MIRION catalog increases the number of candidate intermediate-mass star-forming regions (SFRs) by nearly 2 orders of magnitude, providing an extensive database with which to explore the transition from isolated low-mass to clustered high-mass star formation. The catalog comprises five tables that include mid- and far-infrared photometry, velocities of source-associated molecular clouds, distances to these molecular clouds, physical properties of source-associated star-forming clumps, and source crossmatches with other catalogs. The structure of the catalog enables users to easily sort objects for further study based on distance or environmental properties. Our preliminary analysis extends our earlier findings that indicate a relationship between infrared (IR) colors and the physical properties and evolutionary stages of SFRs. Photometry will be periodically updated online to incorporate measurements from volunteers participating in a classroom activity known as the People Enabling Research: a Yellowball Survey of the Colors Of Protostellar Environments (or PERYSCOPE) project. These updates will continue to refine the IR flux measurements and reduce photometric errors. A follow-up paper will present a detailed analysis of how IR colors can be used to predict the properties of star-forming environments.