Nanten survey of molecular clouds toward the galactic center; Association of compact astronomical objects

Abstract

In order to better understand molecular clouds and their properties toward the Galactic center region, we have analyzed the NANTEN database of 12CO ( J = 1-0) and 13CO ( J = 1-0) to search for associations with candidates for young high-mass star-forming regions, such as IRAS point sources, radio continuum sources, recombination line sources, maser line sources, and other molecular line sources. We have also compared the data with TeV γ-ray sources. The analyzed region covers -12° ≤ l ≤ 12° and -1.°5 ≤ b ≤ l.°5 for 12CO, and -6° ≤ l ≤ 8° and -1° ≤ b ≤ 1° for 13CO. As a result, we identified 167 IRAS point sources, 73 recombination line sources, 58 maser sources, 107 radio continuum sources, and 77 molecular line sources associated with 169 positions with the CO emission. The associations among the objects with known velocity are fairly certain (68%), while those with only positional coincidence are less reliable (32%). We present a catalog of these CO clouds in a form useful for future follow-up studies. As specific examples of usage of the catalog, we highlight three outstanding regions of active star formation: W 28, W 30, and W 31. In particular, we have discovered that the W 30 region shows a striking correlation between the extended TeV γ-ray source and the molecular gas. This is a second case of such a good correlation identified from the NANTEN dataset subsequent to W 28 (Aharonian et al. 2008, A&A, 481, 401). We suggest that the pulsar PSR J1803-2137 near the molecular features may play a role in γ-ray production. The W 31 region exhibits another active star formation, while no γ-ray source is yet known. © 2010. Astronomical Society of Japan.