Detecting Embedded Intermediate-Mass Stars Using Mid-Infrared and H [CSC]i[/CSC] 21 Centimeter Emission

Abstract

A technique is presented to detect distant, young embedded B stars (and possible clusters) from their imprint on the surrounding interstellar medium. H I 21 cm and 12CO (J = 1–0) line data from the Canadian Galactic Plane Survey are combined with mid-infrared images from the Midcourse Space Experiment (MSX) Galactic plane survey to detect the photodissociation regions (PDRs) and molecular gas associated with the embedded intermediate-mass stars. The technique has been applied to a section of the Galaxy covered by the 12CO Five College Radio Astronomy Observatory outer Galaxy survey (1025 < l < 1415, -30 < b < +54) and has led to the detection of 15 embedded intermediate-mass stars. The basic physical properties of the PDRs are presented and compared with PDR models. The PDR models, combined with previous observations of early-type Herbig Ae/Be stars and the nondetection of many of the sources in OH, H2O, and CH3OH surveys, imply that the objects are ~106 yr old. The IRAS colors of the objects form a well-defined group and have been combined with 12CO and MSX observations to identify approximately 100 additional IRAS sources within the survey area as possible embedded intermediate-mass stars.