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.

arXiv comment24 pages, 9 figures, ApJS, in press: APJS, 2016, VOLUME 227

References in corpus (16)

• Hot and Diffuse Clouds near the Galactic Center Probed by Metastable H3+
• Spectral imaging of the Central Molecular Zone in multiple 3-mm molecular lines
• Desorption From Interstellar Ices
• Evidence for a Weak Galactic Center Magnetic Field from Diffuse Low Frequency Nonthermal Radio Emission
• Shock Excited Maser Emission from the Supernova Remnant W28
• Class I methanol masers in the outflow of IRAS 16547-4247
• Enhanced OH in C-type shock waves in molecular clouds
• Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
• High-resolution Observations of OH(1720 MHz) Masers Toward the Galactic Center
• A Survey of Hydroxyl Toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission
• Widespread Methanol Emission from the Galactic Center
• Abundant Methanol Masers but no New Evidence for Star Formation in GCM0.253+0.016
• Expanded VLA Detection of 36.2 GHz Class I Methanol Masers in Sagittarius A
• Parkes full polarization spectra of OH masers - I. Galactic longitudes 350 through the Galactic Centre to 41
• 74 MHz Nonthermal Emission from Molecular Clouds: Evidence for a Cosmic Ray Dominated Region at the Galactic Center
• An OH(1720 MHz) Maser and a Nonthermal Radio Source in Sgr B2(M): A SNR--Molecular Cloud Interaction Site?

Cited by in corpus (17)

• Star Formation Rates of Massive Molecular Clouds in the Central Molecular Zone
• Online Database of Class I Methanol Masers
• 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
• X-raying molecular clouds with a short flare: probing statistics of gas density and velocity fields
• 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