Astronomers detect methanol maser emission towards nearby galaxy

August 22, 2017 by Tomasz Nowakowski, report
36.2 GHz emission methanol emission and the 7 mm continuum emission with background 2MASS 3 colour image. Credit: McCarthy et al., 2017.

(—Using the Australia Telescope Compact Array (ATCA), a team of astronomers has detected methanol emission toward a nearby galaxy known as NGC 4945. The finding, reported Aug. 18 in a paper published on, could be helpful in improving our understanding of star formation processes.

Maser lines of methanol are commonly detected toward regions of high-mass star formation. They are very widespread in our Milky Way galaxy, as they have been detected in more than 1200 sources in the galaxy to date. Due to their rich spectrum of masing transitions, they could be used as a powerful tool for probing .

Scientists divide methanol masers into two groups: class I and class II. Class I masers are associated with the interaction of shocked gas with molecular clouds, driven by outflows or expanding H II regions, while class II masers are closely associated with young stellar objects.

Now, a team of researchers led by Tiege McCarthy of the University of Tasmania in Hobart, Australia, reports the finding of a new class I methanol maser beyond the Milky Way, toward NGC 4945. Located nearly 12 million light years away from the Earth, NGC 4945 is a barred spiral galaxy in the constellation Centaurus, and one of the brightest galaxies of the Centaurus A/M83 Group (large, nearby group of galaxies).

"Here, we report a search for the class I 36.2 GHz and class II 37.7 GHz transition towards the central region of NGC 4945. (…) We detected emission from the 36.2 GHz methanol transition as well as 7 mm continuum emission towards NGC4945," the astronomers wrote in the paper.

The observations leading to the discovery were conducted in August 2015, using ATCA's EW352 array, with minimum and maximum baselines of 31 and 352 meters resulting in a synthesised beam at 36.2 GHz.

The researchers detected a region of 36.2 GHz methanol emission offset southeast from the galactic nucleus by 567 light years. The newly found emission is narrow, with a linewidth below 10 km s−1, and the scientists assume that it may be associated with molecular inflow, which is observed in HF absorption.

The study reveals that this emission's luminosity is five orders of magnitude higher than galactic class I masers from the same transition and 90 times more luminous than the widespread emission detected from our galaxy's central molecular zone. The authors emphasized that their discovery marks the third time when the 36.2 GHz methanol transition has been observed in an extragalactic source. Moreover, it is also the fourth detection of extragalactic class I so far.

The scientists hope that more subsequent observations of such phenomena like methanol masers will help create a better database that could be very useful for studies on processes. "As our sample size increases, it will become easier to identify factors that make appropriate hosts for class I , and allow higher success rates in targeted searches," the team concluded.

Explore further: Shocked gas in galaxy collisions

More information: Detection of 36 GHz Class I Methanol Maser Emission Towards NGC 4945, arXiv:1708.05507 [astro-ph.GA]

We have searched for emission from the 36.2 GHz (4−1→30E) methanol transition towards NGC 4945, using the Australia Telescope Compact Array. 36.2 GHz methanol emission was detected offset south-east from the Galactic nucleus. The methanol emission is narrow, with a linewidth <10 kms−1, and a luminosity five orders of magnitude higher than Galactic class I masers from the same transition. These characteristics combined the with physical separation from the strong central thermal emission suggests that the methanol emission is a maser. This emission is a factor of ∼90 more luminous than the widespread emission detected from the Milky Way central molecular zone (CMZ). This is the fourth detection of extragalactic class I emission, and the third detection of extragalactic 36.2 GHz maser emission. These extragalactic class I methanol masers do not appear to be simply highly luminous variants of Galactic class I emission, and instead appear to trace large-scale regions of low-velocity shocks in molecular gas, which may precede, or be associated with, the early stages of large-scale star formation.

Related Stories

Shocked gas in galaxy collisions

May 1, 2017

Collisions between galaxies, especially ones rich in molecular gas, can trigger bursts of star formation that heat the dust and result in their shining brightly in the infrared. Astronomers think that there is also significant ...

The outer galaxy

July 31, 2017

The sun is located inside one of the spiral arms of the Milky Way galaxy, roughly two-thirds of the way from the galactic center to the outer regions. Because we are inside the galaxy, obscuration by dust and the confusion ...

Extraplanar diffuse ionized gas detected in a nearby galaxy

July 31, 2017

A research group led by Erin Boettcher of the University of Wisconsin-Madison has detected and characterized an extraplanar diffuse ionized gas in the nearby galaxy Messier 83. The study, published July 25 on, provides ...

Masers in stellar nurseries

December 24, 2012

(—Astronomers have come to realize that the process of star formation, once thought to consist essentially of just the simple coalescence of material by gravity, occurs in a complex series of stages. As the gas ...

Image: Hubble peers at the heart of NGC 5793

March 24, 2014

( —This new Hubble image is centered on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an ...

Discovery of an extragalactic hot molecular core

September 29, 2016

Astronomers have discovered a 'hot molecular core', a cocoon of molecules surrounding a newborn massive star, for the first time outside our Galaxy. The discovery, which marks the first important step for observational studies ...

Recommended for you


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.