The CARMA 3mm survey of the inner 0.7° × 0.4° of the Central Molecular Zone

The Central Molecular Zone (CMZ) of the Galactic Centre has to date only been fully mapped at mm wavelengths with single-dish telescopes, with resolution about 30 arcsec (1.2 pc). Using Combined Array for Research in Millimeter-wave Astronomy (CARMA), we mapped the innermost 0.25 deg² of the CMZ over the region between -0.2° ≤ l ≤ 0.5° and -0.2° ≤ b ≤ 0.2° (90 × 50 pc) with spatial and spectral resolution of ~10 arcsec (0.4 pc) and ~2.5 kms^-1, respectively. We provide a catalogue of 3mm continuum sources and spectral line images of SiO(J=2-1), HCO⁺(J=1-0), HCN(J=1-0), N₂H⁺(J=1-0) and CS(J=2-1), with velocity coverage VLSR = -200 to 200 km s^-1. To recover the large-scale structure resolved out by the interferometer, the continuum-subtracted spectral line images were combined with data from theMopra 22-m telescope survey, thus providing maps containing all spatial frequencies down to the resolution limit. We find that integrated intensity ratio of I(HCN)/I(HCO⁺) is anticorrelated with the intensity of the 6.4 keV FeKα, which is excited either by highenergy photons or low-energy cosmic rays, and the gas velocity dispersion as traced by HCO⁺ is correlated with FeKα intensity. The intensity ratio and velocity dispersion patterns are consistent with variation expected from the interaction of low-energy cosmic rays with molecular gas.