FIRST INTERFEROMETRIC IMAGES OF THE 36 GHz METHANOL MASERS IN THE DR21 COMPLEX

Abstract

Class I methanol masers are believed to be produced in the shock-excited environment around star-forming regions. Many authors have argued that the appearance of various subsets of class I masers may be indicative of specific evolutionary stages of star formation or excitation conditions. Until recently, however, no major interferometer was capable of imaging the important 36 GHz transition. We report on Expanded Very Large Array observations of the 36 GHz methanol masers and Submillimeter Array observations of the 229 GHz methanol masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the outflow of DR21(OH) is similar to that of the other class I methanol transitions, with numerous multitransition spatial overlaps. At the site of the main continuum source in DR21(OH), class I masers at 36 and 229 GHz are found in virtual overlap with class II 6.7 GHz masers. To the south of the outflow, the 36 GHz masers are scattered over a large region but usually do not appear coincident with 44 GHz masers. In DR21W, we detect an "S-curve" signature in Stokes V that implies a large value of the magnetic field strength if interpreted as due to Zeeman splitting, suggesting either that class I masers may exist at higher densities than previously believed or that the direct Zeeman interpretation of S-curve Stokes V profiles in class I masers may be incorrect. We find a diverse variety of different maser phenomena in these sources, suggestive of differing physical conditions among them.

Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

“…Multiple methanol masers have been observed in the DR21 complex (Plambeck & Menten 1990;Araya et al 2009;Fish et al 2011). Similarly, we also observed non-LTE methanol emission at 229.76GHz (8 7  + ), as the total flux of these two methanol lines considerably exceeds the LTE emission at 93K.…”

Subarcsecond Imaging of the NGC 6334 I(n) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate

“…In NGC 6334 I(N), we observe strong features in both the 229 GHz transition and the Class I 218.44005 GHz (10 −5,5 -11 −4,8 ) E transition at the position of the brightest 44 GHz maser (spot 55 of Brogan et al 2009), which also coincides in velocity and position with the −3 km s −1 24.9 GHz CH 3 OH maser (Beuther et al 2005;Menten & Batrla 1989). Although interferometric observations of the 229 GHz line have been reported previously (e.g., Fish et al 2011;Cyganowski et al 2011Cyganowski et al , 2012, our observations are the first with sufficient angular resolution to test unequivocally whether the brightness temperature (T B ) exceeds the upper energy level of the transition (E upper ). The peak values of T B in the 229 GHz and 218 GHz lines (3100 K and 270 K, respectively) are both significantly higher than the E upper of these transitions (89 K and 45 K, respectively), indicative of maser emission.…”

DEUTERATED METHANOL (CH3OD) IN THE HOT CORE OF THE MASSIVE STAR-FORMING REGION DR21 (OH)

“…이 천체를 포 함하고 있는 거대한 분자운은 지름이 100 pc를 넘으며 무게는 4 x 10 6 M⊙에 이르고, 우리 은하계에서 가장 무 거운 OB 성협인 Cyg OB2와 연관되어 있다. 이 DR21(OH)는 별 탄생의 표식으로 여겨지는 OH, H2O, 그 리고 CH3OH 등의 활동적 메이저 방출선들이 관측되고 있다 (Norris et al, 1982;Argon et al, 2000;Genzel & Downes, 1977;Batrla & Menten, 1988;Plambeck & Menten, 1990;Kogan & Slysh, 1998;Kurtz et al, 2004;Araya et al, 2009;Fish et al, 2011). 이 천체에서 관측 되는 여러 고밀도 가스 덩어리들은 서로 약 30″ -50″ 떨어져 존재하고 있으며 이들의 질량은 ~ 10 3 M⊙ 정도, 분자 밀도(n(H2))는 ~ 10 6 cm -3 에 이른다 (Mangum et al, 1991).…”