Investigation of Molecular Cloud Structure around Infrared Bubbles: CARMA Observations of N14, N22, and N74

TL;DR

This study uses CARMA observations to analyze molecular cloud structures around infrared bubbles N14, N22, and N74, revealing star-forming cores and suggesting triggered star formation at bubble rims, with implications for cloud fragmentation.

Contribution

First detailed CARMA-based investigation of molecular cloud structures around specific infrared bubbles, identifying star-forming cores and analyzing fragmentation patterns.

Findings

28 compact continuum sources discovered

Approximately half are star-forming cores

Evidence suggests triggered star formation at bubble rims

Abstract

We present CARMA observations in 3.3 mm continuum and several molecular lines of the surroundings of N14, N22, and N74, three infrared bubbles from the GLIMPSE catalog. We have discovered 28 compact continuum sources and confirmed their associations with the bubbles using velocity information from HCO+ and HCN. We have also mapped small-scale structures of N2H+ emission in the vicinity of the bubbles. By combining our data with survey data from GLIMPSE, MIPSGAL, BGPS, and MAGPIS, we establish about half of our continuum sources as star-forming cores. We also use survey data with the velocity information from our molecular line observations to describe the morphology of the bubbles and the nature of the fragmentation. We conclude from the properties of the continuum sources that N74 likely is at the near kinematic distance, which was previously unconfirmed. We also present tentative evidence of molecular clouds being more fragmented on bubble rims compared to dark clouds, suggesting that triggered star formation may occur, though our findings do not conform to a classic collect-and-collapse model.