SIMBAD references

We report the detection of radio recombination line (RRL) H_40α towards 75 sources, with data obtained from ACA (Atacama Compact 7 m Array) observations in the ATOMS (ALMA Three-millimeter Observations of Massive Star-forming regions) survey of 146 active Galactic star-forming regions. We calculated ionized gas mass and star formation rate (SFR) with H_40α line emission. The mass of ionized gas is significantly smaller than molecular gas mass, indicating that ionized gas is negligible in the star-forming clumps of the ATOMS sample. The SFR estimated with RRL H_40α agrees well with that calculated with the total bolometric luminosity (L_bol) when SFR >= 5 M_☉ Myr^–1, suggesting that millimetre RRLs could well sample the upper part of the initial mass function and thus be good tracers of SFR. We also study the relationships between L_bol and the molecular line luminosities (L^′_mol) of CS J = 2-1 and HC₃N J = 11-10 for all the 146 ATOMS sources. The L_ bol_ - L^′_mol correlations of both the CS J = 2-1 and HC₃N J = 11-10 lines appear approximately linear and these transitions have success in predicting L_bol similar to that of more commonly used transitions. The L_bol-to-L^′_mol ratios or SFR-to-mass ratios (star formation efficiency) do not change with galactocentric distances (R_GC). Sources with H_40α emission (or H II regions) show higher L_bol-to-L^′_mol ratios than those without H_40α emission, which may be an evolutionary effect.