Ultra-deep radio telescope catches what Hubble can’t

As great as Hubble is, it can only see a narrow range of light, which means it can only see a sliver of the Universe. Want more?

“We conducted the first fully blind, three-dimensional search for cool gas in the early universe. Through this, we discovered a population of galaxies that is not clearly evident in any other deep surveys of the sky.” –Chris Carilli

For the past 25 years, Hubble has captured our deepest views of the Universe, unveiling galaxies never before seen.

https://players.brightcove.net/2097119709001/4kXWOFbfYx_default/index.html?videoId=5140669017001

By viewing an otherwise blank patch of the sky for hours, days or even weeks, it’s revealed the faint, distant Universe like never before.

*The infrared portion of the Hubble Ultra-Deep Field, taken by the NICMOS instrument. Image credit: NASA and the European Space Agency.*

Hubble can only expose visible and near-infrared light; it can only see stars. But there’s much more to the Universe.

*A Hubble/Spitzer composite image of galaxy cluster SpARCS1049+56 shows how a gas-rich merger (center) can trigger the formation of new stars. Image credit: NASA/STScI/ESA/JPL-Caltech/McGill.*

Most of the normal matter in the Universe is present in the forms of plasma and neutral gas, not stars.

Emission from carbon monoxide as seen in red, in the dwarf galaxy NGC 5253, reveals a bright cloud associated with a forming super star cluster. Individual (visible light) stars are shown in blue. Image credit: J. Turner.

Although Hubble cannot see this gas, it emits light nonetheless, just at longer (radio) wavelengths.

A gas-rich galaxy (orange) as seen prominently against the galaxies in the Hubble Ultra Deep Field (violet). Note its faintness in the HUDF image. Image credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble.

For the first time, an ultra-deep radio telescope has caught it, showing us these cold, raw materials needed for star formation.

*The Atacama Large Millimetre/submillimetre Array, as photographed with the Magellanic clouds overhead. Image credit: ESO/C. Malin.*

Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) surveyed the same dark patch of sky as Hubble, most sensitive to the radio signal of molecular carbon monoxide (CO).

As expected, younger, more distant galaxies have more gas to go along with fewer stars.

A trove of galaxies, rich in dust and cold gas (indicating star-forming potential) was imaged by ALMA (orange) in the Hubble Ultra Deep Field. Image credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble.

The biggest takeaway? The galaxies found closest to the Big Bang are the most gas-rich.

Looking back through cosmic time in the Hubble Ultra Deep Field, ALMA traced the presence of carbon monoxide gas. This enabled astronomers to create a 3-D image of the star-forming potential of the cosmos. Image credit: R. Decarli (MPIA); ALMA (ESO/NAOJ/NRAO).

Star formation peaks after just three billion years, as the gas gets depleted.

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