ESA Herschel: Painting a new story of galaxy evolution

A galaxy accretes mass from rapid, narrow streams of cold gas.

These filaments provide the galaxy with continuous flows of raw material to feed its star-forming at a rather leisurely pace.

This theoretical scenario for galaxy formation is based on the numerical simulations presented by Dekel et al., 2009 (Nature, 457, 451D).

However, the actual process of stream accretion onto a galaxy has never been directly observed and it remains speculative.

ESA's Herschel infrared space observatory has discovered that galaxies do not need to collide with each other to drive vigorous star birth. The finding overturns this long-held assumption and paints a more stately picture of how galaxies evolve.

The conclusion is based on Herschel's observations of two patches of sky, each about a third of the size of the full Moon.

It's like looking through a keyhole across the Universe – Herschel has seen more than a thousand galaxies at a variety of distances from the Earth, spanning 80% of the age of the cosmos.

These observations are unique because Herschel can study a wide range of infrared light and reveal a more complete picture of star birth than ever seen before.

It has been known for some years that the rate of star formation peaked in the early Universe, about 10 billion years ago. Back then, some galaxies were forming stars ten or even a hundred times more vigorously than is happening in our Galaxy today. 

GOODS-North is a patch of sky in the northern hemisphere that covers an area of about a third the size of the Full Moon.

This images was taken by Herschel at the following infrared wavelengths: 100μm (blue), 160μm (green) and 250μm (red). North is up and East is left.

Credits: ESA/GOODS-Herschel consortium/David Elbaz

 

GOODS-South is a patch of sky in the southern hemisphere that covers an area of about a third the size of the Full Moon. 

This image was taken by Herschel and NASA's Spitzer space telescope at the following infrared wavelengths:24 μm (blue), 100 μm (green) and 160 μm (red). North is up and East is left.

Credits: ESA/GOODS-Herschel consortium/NASA/JPL-Caltech/David Elbazere

Read more here at the ESA Herschel portal