A Large--Scale Spectroscopic Survey of Methanol and OH Line Emission from the Galactic Center: Observations and Data

Abstract

Class I methanol masers are collisionally pumped and are generally correlated with outflows in star forming sites in the Galaxy. Using the VLA in its A-array configuration, we present a spectral line survey to identify methanol $J=4_{-1}\to 3_{0}E$ emission at 36.169~GHz. Over 900 pointings were used to cover a region 66'x13'along the inner Galactic plane. A shallow survey of OH at 1612, 1665, 1667 and 1720 MHz was also carried out over the area covered by our methanol survey. We provide a catalog of 2240 methanol masers with narrow line-widths of $\sim 1$ km s${}^{-1}$, spatial resolution of ~0.14"x0.05" and RMS noise $\sim 20$ mJy beam${}^{-1}$ per channel. Lower limits on the brightness temperature range from 27,000 K to 10,000,000 K showing the emission is of non-thermal origin. We also provide a list of 23 OH (1612), 14 OH (1665), 5 OH (1667) and 5 OH(1720 MHz) masers. The origin of such a large number of methanol masers is not clear. Many methanol masers appear to be associated with infrared dark clouds, though it appears unlikely that the entire population of masers trace early phase of star formation in the Galactic center.

24 pages, 9 figures, ApJS, in press: APJS, 2016, VOLUME 227

References in corpus (5)

• Desorption From Interstellar Ices
• Class I methanol masers in the outflow of IRAS 16547-4247
• Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
• A Survey of Hydroxyl Toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission
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Cited by in corpus (16)

• Online Database of Class I Methanol Masers
• Star Formation Rates of Massive Molecular Clouds in the Central Molecular Zone
• A Census of Early Phase High-Mass Star Formation in the Central Molecular Zone
• Methanol masers in NGC 253 with ALCHEMI
• The CARMA 3mm Survey of the Inner $0.7^{\circ }\times 0.4^{\circ }$ of the Central Molecular Zone
• A 6.7 GHz methanol maser survey of the central molecular zone
• The physical parameters of clumps associated with class I methanol masers
• 36 GHz methanol lines from nearby galaxies: maser or quasi-thermal emission?
• The initial conditions for young massive cluster formation in the Galactic Centre: convergence of large-scale gas flows
• Evidence for an interaction between the Galactic Center clouds M0.10-0.08 and M0.11-0.11
• Modelling cosmic masers in C-type shock waves -- the coexistence of Class I CH3OH and 1720 MHz OH masers
• Hot Molecular Core Candidates in the Galactic Center 50 km/s Molecular Cloud
• Discovery of non-metastable ammonia masers in Sagittarius B2
• ALMA observations of massive clouds in the central molecular zone: slim filaments tracing parsec-scale shocks
• Parsec-scale SiO emission in the Galactic Center
• The 107 GHz methanol transition is a dasar in G0.253+0.016