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

B. Vila-Vilaro, J. Cepa, Ann I Zabludoff

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Using the ARO KP 12 m telescope, we have carried out a CO(1-0) and <sup>13</sup>CO(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 <sup>13</sup>CO(1-0), respectively. For three of the targets in our sample (i.e., NGC 0891, NGC 2903, and NGC 3521), we also carry out <sup>13</sup>CO(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)/<sup>13</sup>CO(1-0) (hereafter R<inf>13</inf><sup>12</sup>)) indicates that for "normal" spiral galaxies the scatter in R<inf>13</inf><sup>12</sup> 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 R<inf>13</inf><sup>12</sup> 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 R<inf>13</inf><sup>12</sup> and morphological type along the Hubble sequence. The observed scatter in R<inf>13</inf><sup>12</sup> can be explained by intrinsic variations among the CO conversion factors. The observations presented in this work, which include the most extensive <sup>13</sup>CO(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.

Original languageEnglish (US)
Article number28
JournalAstrophysical Journal, Supplement Series
Issue number2
Publication statusPublished - Jun 22 2015



  • galaxies: ISM
  • galaxies: spiral
  • galaxies: statistics

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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