Variability in extragalactic class I methanol masers: New maser components toward NGC4945 and NGC253

Abstract

We have used the Australia Telescope Compact Array (ATCA) to make new observations of the 36.2-GHz ($4_{-1}\to 3_0$E) methanol transition toward NGC 4945 and NGC 253. These observations have revealed the presence of new maser components toward these galaxies, and have provided the first clear evidence for variability in extragalactic class~I methanol masers. Alongside the new observations of NGC 4945 and NGC 253, we present the results of recent 36.2-GHz methanol maser searches toward 12 galaxies, placing upper limits on the emission from the 36.2-GHz class~I transition and the 37.7-GHz ($7_2\to 8_1$E) class~II maser line toward these sources. Flux density values for the 7-mm continuum emission toward these sources are also reported where applicable. A re-analysis of the published 36.2-GHz methanol observations of Arp 220 undertaken as part of the search revealed some issues with previous imaging procedures. The re-analysis, combined with non-detections in independent follow-up observations suggest that there is no 36.2-GHz methanol emission toward Arp 220 stronger than 3.5 mJy in a 10 km s${}^{-1}$ channel (5$\sigma$ upper limit).

arXiv commentAccepted into MNRAS 2019 November 1. 15 pages, 6 figures and 8 tables (7 in main text, 1 in appendix)

References in corpus (41)

• Astropy: A Community Python Package for Astronomy
• Cosmicflows-2: The Data
• The ACS Nearby Galaxy Survey Treasury
• Cosmicflows-3
• The Australia Telescope Compact Array Broadband Backend (CABB)
• Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• 12.2-GHz methanol masers associated with 1.2-mm dust clumps: Quantifying high-mass star formation evolutionary schemes
• From Spitzer Galaxy Photometry to Tully-Fisher Distances
• Confirmation of the exclusive association between 6.7-GHz methanol masers and high-mass star formation regions
• Duchamp: a 3D source finder for spectral-line data
• Southern class I methanol masers at 36 and 44 GHz
• Class I methanol masers in the outflow of IRAS 16547-4247
• The Megamaser Cosmology Project VIII. A Geometric Distance to NGC 5765b
• Quasi-Periodic Formaldehyde Maser Flares in the Massive Protostellar Object IRAS18566+0408
• Interstellar H${}_2$O Masers from J Shocks
• Star-forming Cloud Complexes in the Central Molecular Zone of NGC 253
• Physical characteristics of bright Class I methanol masers
• Water maser variability over 20 years in a large sample of star-forming regions: the complete database
• Statistical properties of 12.2 GHz methanol masers associated with a complete sample of 6.7 GHz methanol masers
• On the methanol masers in G9.62+0.20E and G188.95+0.89
• Widespread Methanol Emission from the Galactic Center
• Multibeam Maser Survey of methanol and excited OH in the Magellanic Clouds: new detections and maser abundance estimates
• Masers associated with high-mass star formation regions in the Large Magellanic Cloud
• The Circumnuclear Molecular Gas in the Seyfert Galaxy NGC4945
• Observational Evidence for Massive Black Holes in the Centers of Active Galaxies
• Survey of Water and Ammonia in Nearby galaxies (SWAN): Resolved Ammonia Thermometry, Water and Methanol Masers in the Nuclear Starburst of NGC 253
• Free-free and H42alpha emission from the dusty starburst within NGC 4945 as observed by ALMA
• Discovery of the first methanol (CH3OH) maser in the Andromeda galaxy (M31)
• Molecular line emission in NGC 4945, imaged with ALMA
• The Protocluster G18.67+0.03: A Test Case for Class I Methanol Masers as Evolutionary Indicators for Massive Star Formation
• Detection of 36 GHz class I methanol maser emission towards NGCS253
• Detection of a methanol megamaser in a major-merger galaxy
• Class I methanol masers in NGC253: Alcohol at the end of the bar
• Class I Methanol (CH${}_3$OH) Maser Conditions near Supernova Remnants
• Water-Vapor Maser Disk at the Nucleus of the Seyfert 2 Galaxy IC 2560 and its Distance
• Survey of Water and Ammonia in Nearby galaxies (SWAN): Resolved Ammonia Thermometry, and Water and Methanol Masers in IC 342, NGC 6946 and NGC 2146
• 6.7 GHz variability characteristics of new periodic methanol maser sources
• Detection of 36 GHz Class I Methanol Maser Emission Towards NGC 4945
• Investigations of the Class I methanol masers in NGC 4945
• Detection of 84-GHz class I methanol maser emission towards NGC 253

Cited by in corpus (3)

• Methanol masers in NGC 253 with ALCHEMI
• CH${}_3$OH as a User-Friendly Density Probe: Calibration and Beyond
• First detection of the $J_{-1}\to (J-$ 1)${}_0-E$ methanol maser transitions at $J=7$ and $10$