Expanded VLA Detection of 36.2 GHz Class I Methanol Masers in Sagittarius A

Abstract

We report on the interferometric detection of 36.2 GHz Class I methanol emission with the new 27-40 GHz Ka band receivers available on the Expanded Very Large Array (EVLA). The brightness temperatures of the interferometric 36 GHz detections unambiguously indicate for the first time that the emission is maser emission. The 36 GHz methanol masers are not co-spatial with 1720 MHz OH masers, indicating that the two species trace different shocks. The 36 GHz and 44 GHz methanol masers, which both are collisionally pumped, do not necessarily co-exist and may trace different methanol gas. The methanol masers seem correlated with NH_3(3,3) density peaks. We favor an explanation in which the 36 GHz Class I methanol masers outline regions of cloud-cloud collisions, perhaps just before the onset of the formation of individual massive stars. The transition of the Very Large Array (VLA) to the EVLA is well under way, and these detections demonstrate the bright future of this completely renewed instrument.

accepted to ApJ Letters

References in corpus (7)

• HCN and HCO+ Observations of the Galactic Circumnuclear Disk
• Accurate rest frequencies of methanol maser and dark cloud lines
• Gas infall towards Sgr A* from the clumpy circumnuclear disk
• Massive Star Formation in the Molecular Ring Orbiting the Black Hole at the Galactic Center
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Cited by in corpus (31)

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• Abundant Methanol Masers but no New Evidence for Star Formation in GCM0.253+0.016
• ISM Processing in the Inner 20 pc in Galactic center
• Detection of Class I Methanol (CH3OH) Maser Candidates in Supernova Remnants
• Mapping photodissociation and shocks in the vicinity of Sgr A*
• First Interferometric Images of the 36 GHz Methanol Masers in the DR21 Complex
• The Circumnuclear Disk Revealed by ALMA. I. Dense Clouds and Tides in the Galactic Center
• Expanded Very Large Array Detection of 44.1 GHz Class I Methanol Masers in Sagittarius A
• Approaching hell's kitchen: Molecular daredevil clouds in the vicinity of Sgr A*
• Origins of Scatter in the Relationship Between HCN 1-0 and Dense Gas Mass in the Galactic Center
• MALT-45: A 7 mm survey of the southern Galaxy - I. Techniques and spectral line data
• Class I Methanol (CH${}_3$OH) Maser Conditions near Supernova Remnants
• High-velocity feature of the class I methanol maser in G309.38-0.13
• A Large--Scale Spectroscopic Survey of Methanol and OH Line Emission from the Galactic Center: Observations and Data
• NH${}_3$(3,3) and CH${}_3$OH near Supernova Remnants: GBT and VLA Observations
• The Unusual Galactic Center Radio Source N3
• 44 GHz Class I Methanol (CH${}_3$OH) Maser Survey in the Galactic Center
• New class I methanol masers
• Comparison of Two Epochs of the Zeeman Effect in the 44 GHz Class I methanol (CH3OH) maser line in OMC-2
• Very Large Array monitoring of 1720 MHz OH masers toward the Galactic Center
• 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
• A Radio Survey of Galactic Center Clouds
• Masers in star forming regions
• Very Large Array Detection of the 36 GHz Zeeman Effect in DR21W Revisited
• A 95 GHz Methanol Emission Survey Toward Eight Small Supernova Remnants
• Molecular gas in the immediate vicinity of Sgr A* seen with ALMA