The ALMA-ATOMS survey: Vibrationally excited HC3N lines in hot cores

Interstellar molecules are excellent tools for studying the physical and chemical environments of massive star-forming regions. In particular, vibrationally excited HC3N (HC3N*) lines are the key tracers for probing hot cores environments. We present the Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm observations of HC3N* lines in 60 hot cores, aiming to investigate how physical conditions affect the excitation of HC3N* transitions. We have used the XCLASS for line identification. Under the assumption of local thermodynamic equilibrium (LTE), we derived the rotation temperature, column density, and line width of HC3N* transitions in hot cores. Additionally, we calculated the H2 column density and number density, along with the abundance of HC3N* relative to H2, to enable a comparison of the physical properties of hot cores with different numbers of HC3N* states. We have detected HC3N* lines in 52 hot cores, in which 29 cores showing more than one vibrationally excited state. Hot cores with higher gas temperatures have more detections of these vibrationally excited lines. The line width of each HC3N* line tends to decrease with increasing vibrational energy level. The excitation of HC3N* requires dense environments, with its spatial distribution and abundance influenced by the presence of UC Hii regions. The observed rotation temperature and column density of HC3N* both contribute to the number of HC3N* states in hot core environments. After analyzing the various factors influencing HC3N* excitation in hot cores, we conclude that the excitation of HC3N* is mainly driven by mid-IR pumping, while collisional excitation is ineffective.