"We are directly viewing the region where the cold gas is responding to the black hole's gravitational pull," said Barth.
To calculate the mass of a black hole in a galaxy's centre, astronomers must be able to measure the speed of something orbiting around it, he said.
"For a precise measurement, we need to zoom in to the very centre of a galaxy where the black hole's gravitational pull is the dominant force. ALMA is a fantastic new tool for carrying out these observations," said Barth.
Dense, cold clouds of interstellar gas and dust do not emit visible light, but glow brightly at wavelengths that ALMA can observe.
Researchers trained ALMA's observational powers on NGC 1332, a giant elliptical galaxy in the southern sky 73 million light-years from Earth. Elliptical galaxies are known to contain massive central black holes.
About one in 10 elliptical galaxies contain disks of cold molecular gas and dust that orbit their centres, scientists said.
ALMA can observe radio-wavelength light emitted by molecules in these structures.
The emission is shifted to shorter or longer wavelengths by the Doppler Effect depending on whether the disk's gas is rotating towards or away from observers, which enables astronomers to map the motion of the gas, scientists said.
In this case, researchers focused on radio-wave emissions from carbon monoxide (CO) molecules, since the CO signal is bright and readily detected with ALMA.
"This observation demonstrates a technique that can be applied to many other galaxies to measure the masses of supermassive black holes to remarkable precision," said Benjamin Boizelle from UCI.
The findings were published in the Astrophysical Journal Letters.
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