ESO: A young dwarf galaxy emerges from the debris of a cosmic collision

The latest report from the ESO (European Southern Observatory):

VLT Revisits a Curious Cosmic Collision

The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in new images from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris is a rare and mysterious young dwarf galaxy. This galaxy is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.

The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy, which appears as a bright clump towards the right of the image. This object is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.
The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy, which appears as a bright clump towards the right of the image. This object is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.

NGC 5291, the hazy, golden oval dominating the centre of this image, is an elliptical galaxy located nearly 200 million light-years away in the constellation of Centaurus (The Centaur). Over 360 million years ago, NGC 5291 was involved in a dramatic and violent collision as another galaxy travelling at immense speeds barrelled into its core. The cosmic crash ejected huge streams of gas into nearby space, which later coalesced into a ring formation around NGC 5291 [1].

The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy known as NGC 5291N. It is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.
The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy known as NGC 5291N. It is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.

Over time, material in this ring gathered and collapsed into dozens of star-forming regions and several dwarf galaxies, revealed as pale blue and white regions scattered around NGC 5291 in this new image from the FORS instrument, mounted on the VLT. The most massive and luminous clump of material, to the right of NGC 5291, is one of these dwarf galaxies and is known as NGC 5291N.

This chart shows the location of the interacting galaxy system NGC 5291 in the bright southern constellation of Centaurus. Most of the stars visible with the naked eye on a dark clear moonless night are shown and the location of the galaxy is marked with a red circle. NGC 5291 can be seen as a faint fuzzy spot through larger amateur telescopes.
This chart shows the location of the interacting galaxy system NGC 5291 in the bright southern constellation of Centaurus. Most of the stars visible with the naked eye on a dark clear moonless night are shown and the location of the galaxy is marked with a red circle. NGC 5291 can be seen as a faint fuzzy spot through larger amateur telescopes. Credit ESO, IAU, Sky & Telescope

The Milky Way, like all large galaxies, is believed to have formed through the build-up of smaller dwarf galaxies in the early years of the Universe. These small galaxies, if they have survived on their own up to the present day, now normally contain many extremely old stars.

Yet NGC 5291N appears to contain no old stars. Detailed observations with the MUSE spectrograph [2] also found that the outer parts of the galaxy had properties typically associated with the formation of new stars, but what was observed is not predicted by current theoretical models. Astronomers suspect that these unusual aspects may be the result of massive collisions of gas in the region.

This video takes us from a broad view of the southern Milky Way deep into the large constellation of Centaurus. The sequence ends with a close-up view from ESO’s Very Large Telescope of an interacting galaxy called NGC 5291, about 200 million light-years from Earth. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org)

NGC 5291N doesn’t look like a typical dwarf galaxy, but instead it shares a striking number of similarities with the clumpy structures present within many of the star-forming galaxies in the distant Universe. This makes it a unique system in our local Universe and an important laboratory for the study of early gas-rich galaxies, which are normally much too distant to be observed in detail by current telescopes.

This close-up pan video shows the spectacular aftermath of a 360 million year old cosmic collision, as revealed in great detail in an image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 is a rare and mysterious young dwarf galaxy. It is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org)

This unusual system has previously been observed by a wide range of ground-based facilities, including ESO’s 3.6-metre telescope at the La Silla Observatory [3]. However, the capabilities of MUSE, FORS and the Very Large Telescope have only now allowed some of the history and properties of NGC 5291N to be determined.

This wide-field view shows the sky around the galaxy NGC 5291. This system has interacted with other galaxies and is surrounded with debris from earlier encounters. Some of this material is now forming dwarf galaxies rich in young stars. This picture was created from images forming part of the Digitized Sky Survey 2. Many other galaxies are also visible.
This wide-field view shows the sky around the galaxy NGC 5291. This system has interacted with other galaxies and is surrounded with debris from earlier encounters. Some of this material is now forming dwarf galaxies rich in young stars. This picture was created from images forming part of the Digitized Sky Survey 2. Many other galaxies are also visible. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

Future observations, including those by ESO’s European Extremely Large Telescope (E-ELT), may allow astronomers to further unravel this dwarf galaxy’s remaining mysteries.

Notes

[1] NGC 5291 is currently also interacting more gently with MCG-05-33-005 — or the Seashell Galaxy — the unusual comma-shaped galaxy appearing to leech off NGC 5291’s luminous core.

[2] NGC 5291N was observed using integral field spectrography during MUSE’s first Science Verification run. Integral field spectrography collects a spectrum at every point on the sky, providing a powerful three-dimensional view of the target. The MUSE observations revealed unexpected oxygen and hydrogen emission lines in the outskirts of NGC 5291N.

[3] NGC 5291 was studied by astronomers using ESO’s 3.6-metre telescope at the La Silla Observatory back in 1978. These observations revealed large amounts of material in the intergalactic space around the galaxy, which we now know to be the star-forming regions and several dwarf galaxies created from the collapse of the galaxy’s gaseous ring.