A (12)CO survey of the LMC with NANTEN: Sensitive observations

Abstract

Fully sampled (12)CO (J = 1-0) observations of the whole extent of the LMC (Large Magellanic Cloud) have been made, using NANTEN radio telescope with a linear resolution of approximately 40 pc (parsecs) at a detection limit for N(H(2)) of 3 x 10(exp 21) per sq cm. In addition, to reveal the distribution of weakly emitting molecular gas, several selected regions including 30 Doradus, the southern large CO complex, N11, N44 and the Bar, have been mapped with higher sensitivity corresponding to a detection limit of 1 x 10(exp 21) per sq cm in the same line at the same angular resolution. Based on these results, the total molecular mass of the LMC was estimated approximately as 7 x 10(exp 7) solar masses, if the sensitive observations were made over the whole galaxy. The conversion factor from CO line intensity to H2 column density is discussed in individual regions. The detailed comparisons of the GMCs (Giant Molecular Clouds) to H II regions and the young stellar clusters are also presented.

N(H2)の検出限界3×10(exp 21)/平方センチメートルで約40pc(パーセク)の線形分解能を持つ電波望遠鏡「なんてん」を用いて、LMC(大マゼラン星雲)全領域に関する(12)CO(J=1-0)観測を行った。さらに、弱く放射する分子ガスの分布を明らかにするために、かじき座30番星、南方の大きなCO複合体、N11、N44、およびバー構造を含む幾つかの領域を選択し、同じライン同じ角度分解能でより高い感度検出限界である10(exp 21)/平方センチメートルで作図した。この結果をもとにすると、もし高感度の観測が銀河全体で行われれば、大マゼラン星雲の分子質量は約7×10(exp 7)太陽質量と見積った。一酸化炭素輝線強度から水素分子の柱密度への変換因子を、個々の領域について論じた。さらに、GMC(巨大分子雲)領域とHII(電離水素)領域および若い星団との詳細な比較についても説明した。