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The role of ionization feedback on high-mass (>8 Msun) star formation (HMSF)is still highly debated. Questions remain concerning the presence of nearby HIIregions changes the properties of early HMSF and whether HII regions promote orinhibit the formation of high-mass stars. To characterize the role of HIIregions on the HMSF, we study the properties of a sample of candidateshigh-mass starless clumps (HMSCs), of which about 90% have masses larger than100 Msun. These high-mass objects probably represent the earliest stages ofHMSF; we search if (and how) their properties are modified by the presence ofan HII region. We took advantage of the recently published catalog of HMSCcandidates. By cross matching the HMSCs and HII regions, we classified HMSCsinto three categories: 1) The HMSCs associated with HII regions both in theposition in the projected plane of the sky and in velocity; 2) HMSCs associatedin the plane of the sky, but not in velocity; and 3) HMSCs far away from anyHII regions in the projected sky plane. We carried out comparisons betweenassociated and nonassociated HMSCs based on statistical analyses ofmultiwavelength data from infrared to radio. Statistical analyses suggest thatHMSCs associated with HII regions are warmer, more luminous, morecentrally-peaked and turbulent. We also clearly show, for the first time, thatthe ratio of bolometric luminosity to envelope mass of HMSCs (L/M) could not bea reliable evolutionary probe for early HMSF due to the external heatingeffects of the HII regions. More centrally peaked and turbulent properties ofHMSCs associated with HII regions may promote the formation of high-mass starsby limiting fragmentation. High resolution interferometric surveys toward HMSCsare crucial to reveal how HII regions impact the star formation process insideHMSCs.

HII regions and high-mass starless clump candidates I: Catalogs and properties