The Arizona radio observatory survey of molecular gas in nearby normal spiral galaxies I: The data

Using the ARO KP 12 m telescope, we have carried out a CO(1-0) and ¹³CO(1-0) survey of the central regions of 113 "normal" spiral galaxies (i.e., unperturbed and with little or no nuclear activity). Our sample spans the whole range of morphological types (T = 1-7), with distances up to 75 Mpc. The detection rates for the observed objects are 99.1% for CO(1-0) and 75.2% for ¹³CO(1-0), respectively. For three of the targets in our sample (i.e., NGC 0891, NGC 2903, and NGC 3521), we also carry out ¹³CO(1-0) mapping along their major axes, which, combined with data from the literature, reveal differences in their molecular gas properties. Analysis of the beam-matched line intensity ratios of CO(1-0)/¹³CO(1-0) (hereafter R₁₃¹²)) indicates that for "normal" spiral galaxies the scatter in R₁₃¹² is of ≈x3, and has an average value (including upper limits) of 10.4 ± 0.4 (in contrast with the values of 3-5 in typical giant molecular clouds and 13 ± 6 in Starburst Galaxies). No significant correlations (at the ≥2σ level) are found between R₁₃¹² and the total far-infrared (FIR) luminosity, the FIR colors, and the fraction of area sampled in the disk of each galaxy. There is a tentative (1.4σ significance) correlation between R₁₃¹² and morphological type along the Hubble sequence. The observed scatter in R₁₃¹² can be explained by intrinsic variations among the CO conversion factors. The observations presented in this work, which include the most extensive ¹³CO(1-0) extragalactic survey published so far on "normal" spiral galaxies are ideally suited for use in recovering the "missing" flux of interferometers with elements of similar dish sizes.