A distant but average galaxy observed by astronomers using the world’s largest ground-based single-aperture millimeter telescope has surprised scientists with a star formation rate four times higher than seen during previous observations.
Researchers led by Alexandra Pope of the University of Massachusetts at Amherst coupled their telescopic observations with gravitational lensing to obtain a better view of the dusty galaxy, known as MACS071_Az9.
Gravitational lensing is a technique that uses a foreground object, such as a star, galaxy, or cluster of galaxies, as a lens for viewing light from a much more distant object, making it possible for scientists to observe objects too faint to be seen through telescopes alone.
The galaxy’s high dust content had masked star formation during previous observations even in images captured by the Hubble Space Telescope.
This was the first time the galaxy was observed by scientists using the 50-meter Large Millimeter Telescope (LMT), which sits on an extinct volcano in central Mexico and is operated by UMass Amherst and Mexico’s Instituto Nacional de Astrofisica, Optica y Electronica (INAOE).
Whereas Hubble data showed the galaxy producing the equivalent of four solar masses of new stars every year, the combination of LMT and gravitational lensing revealed star formation is actually occurring at a rate of about 19 solar masses per year.
“We had been missing about three-quarters of the star formation going on,” Pope emphasized.
Studying galaxies during their early eras helps inform scientists about how the universe became enriched with metals heavier than hydrogen and helium, Pope said.
“We know at the basic level that metals are formed in stars, but the rate of buildup over cosmic time we don’t know. We know what we see today, but we don’t know how it came about, and we want to fill in that picture.”
A low mass galaxy, MACS071_Az9 has a low level of metallicity and a high dust content.
The next step in obtaining more accurate data on star formation in the galaxy will involve installing a new state of the art imaging system on LMT capable of mapping 100 times faster than the telescope’s current instruments.
Pope believes the new instrument will for the first time provide scientists with an accurate census of star formation in dusty galaxies.
“One of the big goals for us is to push observations at longer wavelengths and to trace these very dusty galaxies at early epochs. We are pushing observations in this direction, and the fact that Hubble found only one-quarter of the star formation in this distant, normal galaxy is a huge motivation for doing a lot more studies like this,” she said.
An article discussing the study’s findings has been accepted for publication in The Astrophysical Journal.
Distant galaxy surprises scientists with high star formation rate – The Space Reporter