We present the results of our spectral line surveys in the 1.3 and 2 mm windows toward the carbon-rich envelope of IRC +10216. There were 377 lines are detected in total, of which 360 lines are assigned to 57 known molecules (including 29 rare isotopomers and two cyclic isomers). Only 17 weak lines remain unidentified. Rotational lines of isotopomers 13 CCH and HN 13 C are detected for the first time in IRC +10216 . The detection of the formaldehyde lines in this star is also confirmed. Possible abundance differences among the three 13 C-substituted isotopic isomers of HC 3 N is reported. Isotopic ratios of C and O are confirmed to be nonsolar while those of S and Si to be nearly solar. Column densities have been estimated for 15 molecular species. Modified spectroscopic parameters have been calculated for NaCN, Na 13 CN, KCN, and SiC 2 . Transition frequencies from the present observations were used to improve the spectroscopic parameters of Si 13 CC, 29 SiC 2 , and 30 SiC 2 .

The Multi-Scale Continuum and Line Exploration of W49 (MUSCLE W49) is a comprehensive gas and dust survey of the giant molecular cloud (GMC) of W49A, the most luminous star-formation region in the Milky Way. The project covers, for the first time, the entire GMC at different scales and angular resolutions. In this paper we present: 1) an all-configuration SMA mosaic in the 230-GHz (1.3-mm) band covering the central ∼ 3 × 3 (∼ 10 pc, known as W49N), where most of the embedded massive stars reside; and 2) PMO 14m telescope observations in the 90-GHz band, covering the entire GMC with maps of up to ∼ 35 × 35 in size, or ∼ 113 pc. We also make use of archival data from the VLA, JCMT-SCUBA, IRAM 30m, and the CSO BOLOCAM Galactic Plane Survey. We derive the basic physical parameters of the GMC at all scales. Our main findings are as follows: 1) The W49 GMC is one of the most massive in the Galaxy, with a total mass M gas ∼ 1.1 × 10 6 M within a radius of 60 pc. Within a radius of 6 pc, the total gas mass is M gas ∼ 2 × 10 5 M . At these scales only ∼ 1% of the material is photoionized. The mass reservoir is sufficient to form several young massive clusters (YMCs) as massive as a globular cluster. 2) The mass of the GMC is distributed in a hierarchical network of filaments. At scales < 10 pc, a triple, centrally condensed structure peaks toward the ring of HC HII regions in W49N. This structure extends to scales from ∼ 10 to 100 pc through filaments that radially converge toward W49N and its less prominent neighbor W49S. The W49A starburst most likely formed from global gravitational contraction with localized collapse in a "hub-filament" geometry. 3) Currently, feedback from the central YMCs (with a present mass M cl 5 × 10 4 M ) is still not enough to entirely disrupt the GMC, but further stellar mass growth could be enough to allow radiation pressure to clear the cloud and halt star formation. 4) The resulting stellar content will probably remain as a gravitationally bound massive star cluster, or a small system of bound clusters.

Context. Orion-KL is a remarkable, nearby star-forming region where a recent explosive event has generated shocks that could have released complex molecules from the grain mantles. Aims. A comparison of the distribution of the different complex molecules will help in understanding their formation and constraining the chemical models.Methods. We used several data sets from the Plateau de Bure Interferometer to map the dimethyl ether emission with different arcsec spatial resolutions and different energy levels (from E up = 18 to 330 K) to compare with our previous methyl formate maps. Results. Our data show remarkable similarity between the dimethyl ether (CH 3 OCH 3 ) and the methyl formate (HCOOCH 3 ) distributions even on a small scale (1.8 × 0.8 or ∼500 AU). This long suspected similarity, seen from both observational and theoretical arguments, is demonstrated with unprecedented confidence, with a correlation coefficient of maps ∼0.8. Conclusions. A common precursor is the simplest explanation of our correlation. Comparisons with previous laboratory work and chemical models suggest the major role of grain surface chemistry and a recent release, probably with little processing, of mantle molecules by shocks. In this case the CH 3 O radical produced from methanol ice would be the common precursor (whereas ethanol, C 2 H 5 OH, is produced from the radical CH 2 OH). The alternative gas phase scheme, where protonated methanol CH 3 OH + 2 is the common precursor to produce methyl formate and dimethyl ether through reactions with HCOOH and CH 3 OH, is also compatible with our data. Our observations cannot yet definitely allow a choice between the different chemical processes, but the tight correlation between the distributions of HCOOCH 3 and CH 3 OCH 3 strongly contrasts with the different behavior we observe for the distributions of ethanol and formic acid. This provides a very significant constraint on models.

Aims. Deuterated molecules have been detected and studied toward Orion BN/KL in the past decades, mostly with single-dish telescopes. However, high angular resolution data are critical not only for interpreting the spatial distribution of the deuteration ratio but also for understanding this complex region in terms of cloud evolution involving star-forming activities and stellar feedbacks. Therefore, it is important to investigate the deuterated ratio of methanol, one of the most abundant grain-surface species, on a scale of a few arcseconds to better understand the physical conditions related to deuteration in Orion BN/KL. Methods. Orion BN/KL was extensively observed with the IRAM Plateau de Bure Interferometer from 1999 to 2007 in the 1 to 3 mm range. The angular resolution varies from 1. 8 × 0. 8 to 3. 6 × 2. 3 and the spectral resolution varies from 0.4 to 1.9 km s −1 . Deuterated methanol CH 2 DOH and CH 3 OD and CH 3 OH lines were searched for within our 3 mm and 1.3 mm data sets.Results. We present here the first high angular resolution (1. 8 × 0. 8) images of deuterated methanol CH 2 DOH in Orion BN/KL. Six CH 2 DOH lines were detected around 105.8, 223.5, and 225.9 GHz. In addition, three E-type methanol lines around 101-102 GHz were detected and were used to derive the corresponding CH 3 OH rotational temperatures and column densities toward different regions across Orion BN/KL. The strongest CH 2 DOH and CH 3 OH emissions come from the Hot Core southwest region with a velocity that is typical of the Compact Ridge (V LSR ≈ 8 km s −1 ). We derive [CH 2 DOH]/[CH 3 OH] abundance ratios of 0.8-1.3 × 10 −3 toward three CH 2 DOH emission peaks. A new transition of CH 3 OD was detected at 226.2 GHz for the first time in the interstellar medium. Its distribution is similar to that of CH 2 DOH. Besides, we find that the [CH 2 DOH]/[CH 3 OD] abundance ratios are lower than unity in the central part of BN/KL. Furthermore, the HDO 3 1,2 −2 2,1 line at 225.9 GHz was detected and its emission distribution shows a shift of a few arcseconds with respect to the deuterated methanol emission that likely results from different excitation effects. The deuteration ratios derived along Orion BN/KL are not markedly different from one clump to another. However, various processes such as slow heating due to ongoing star formation, heating by luminous infrared sources, or heating by shocks could be competing to explain some local differences observed for these ratios.