Merging Galaxies Make for Explosive Star Formation

A festive array of bright pinks and blues makes for a remarkable sight in this image captured with the Gemini North telescope, one half of the International Gemini Observatory. Resembling a cloud of cosmic confetti, this image is being released in celebration of Gemini North’s 25th anniversary. NGC 4449 is a prime example of starburst activity caused by the interacting and mingling of galaxies as it slowly absorbs its smaller galactic neighbors.

The Gemini Observatory has unveiled a striking new image that shows star formation within the irregular galaxy NGC 4449. This galaxy is categorised as a “Magellanic-type” galaxy due to its similarities  with the Magellanic Clouds, although it is smaller in size. Surrounding NGC 4449 is a halo of smaller dwarf galaxies, two of which are currently merging with it. This merger is causing clouds of gas to collide, fuelling the surge in star formation observed in NGC 4449.

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Webb Sees a Galaxy Awash in Star Formation

Starburst galaxy M82 was observed by the Hubble Space Telescope in 2006, which showed the galaxy’s edge-on spiral disk, shredded clouds, and hot hydrogen gas. The James Webb Space Telescope has observed M82’s core, capturing in unprecedented detail the structure of the galactic wind and characterizing individual stars and star clusters. Credit: NASA/ESA/CSA/STScI/Alberto Bolatto (UMD)

Since it began operations in July 2022, the James Webb Space Telescope (JWST) has fulfilled many scientific objectives. In addition to probing the depths of the Universe in search of galaxies that formed shortly after the Big Bang, it has also provided the clearest and most detailed images of nearby galaxies. In the process, Webb has provided new insight into the processes through which galaxies form and evolve over billions of years. This includes galaxies like Messier 82 (M82), a “starburst galaxy” located about 12 million light-years away in the constellation Ursa Major.

Also known as the “Cigar Galaxy” because of its distinctive shape, M82 is a rather compact galaxy with a very high star formation rate. Roughly five times that of the Milky Way, this is why the core region of M82 is over 100 times as bright as the Milky Way’s. Combined with the gas and dust that naturally obscures visible light, this makes examining M82’s core region difficult. Using the extreme sensitivity of Webb‘s Near-Infrared Camera (NIRCam), a team led by the University of Maryland observed the central region of this starburst galaxy to examine the physical conditions that give rise to new stars.

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The Universe in Formation. Hubble Sees 6 Examples of Merging Galaxies

Newly released collage of six galaxy mergers used in the HiPEEC survey. Top Row Left to Right: NGC 3256, 1614, 4195 Bottom Row Left To Right: NGC 3690, 6052, 34 - Credit ESA/Hubble/NASA

Audio narration by the author is available above

10 billion years ago, galaxies of the Universe were ablaze with the light of newly forming stars. This epic phase of history is known as  “Cosmic Noon” – the height of all star creation. Galaxies like our Milky Way aren’t creating stars at nearly the rates they were in the ancient past. However, there is a time when galaxies in the present can explode with star formation – when they collide with each other. This recently published collage of merging galaxies by the Hubble HiPEEC survey (Hubble imaging Probe of Extreme Environments and Clusters) highlights six of these collisions which help us understand star formation in the early Universe.

Newly released collage of six galaxy mergers used in the HiPEEC survey.
Top Row Left to Right: NGC 3256, 1614, 4195 Bottom Row Left To Right: NGC 3690, 6052, 34
– Credit ESA/Hubble/NASA
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Entire Galaxies Feel The Heat Of Newborn Stars

This illustration shows a messy, chaotic galaxy undergoing bursts of star formation. This star formation is intense; it was known that it affects its host galaxy, but this new research shows it has an even greater effect than first thought. The winds created by these star formation processes stream out of the galaxy, ionising gas at distances of up to 650 000 light-years from the galactic centre. Credit: ESA, NASA, L. Calçada

If you think that star-formation only has an impact within the confines of a host galaxy, then think again. Thanks to the magic of the NASA/ESA Hubble Space Telescope, astronomers are now realizing starburst activity can change the properties of galactic gases at distances almost twenty times larger than a galaxy’s visible boundaries. Not only does this affect galactic evolution, but it has ramifications on how matter and energy ripple across the cosmos.

What’s going on here? Once upon a time in the early Universe, galaxies would form new stars in huge blasts of activity known as starbursts. While it happened frequently long ago, it’s much less common now. During these starburst episodes, hundreds of millions of stars spring to light and their combined energy sets off massive stellar winds that push outward into space. While these winds were known to have effects on the parent galaxy, new research shows they have an even greater effect than anyone knew.

Recently a team of international astronomers took on twenty galaxies which are known to be hosting starburst activity. What they found was the starburst stellar winds were able to ionize gas at huge distances – up to 650,000 light years from the galaxy’s nucleus – and around twenty times beyond the galaxy’s visible perimeter. For the first time, researchers were able to verify that starburst activity could impact the gas around the parent galaxy. This new observational evidence shows just how important each phase a galaxy goes through can impact the way it form stars and how it evolves.

“The extended material around galaxies is hard to study, as it’s so faint,” says team member Vivienne Wild of the University of St. Andrews. “But it’s important — these envelopes of cool gas hold vital clues about how galaxies grow, process mass and energy, and finally die. We’re exploring a new frontier in galaxy evolution!”

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This animation shows the method used to probe the gas around distant galaxies. Astronomers can use tools such as Hubble’s Cosmic Origins Spectrograph (COS) to probe faint galactic envelopes by exploiting even more distant objects — quasars, the intensely luminous centres of distant galaxies powered by huge black holes. As the light from the distant quasar passes through the galaxy’s halo, the gas absorbs certain frequencies – making it possible to study the region around the galaxy in detail. This new research utilised Hubble’s COS to peer through the very thin outskirts of galactic halos, much further out than shown in this representation, to explore galactic gas at distances of up to twenty times greater than the visible size of the galaxy itself. Credit: ESA, NASA, L. Calçada

So how did they do it? According to the news release, the researchers employed the Cosmic Origins Spectrograph (COS) instrument located on the NASA/ESA Hubble Space telescope. By examining the spectral signature of a variety of starbirth and control galaxies, the team was able to carefully examine the regions of gas surrounding the galaxies. However, they had a little boost, too… quasars. By adding the light of the intensely luminous galactic cores to the mix, they were able to further refine their observations by watching the quasar’s light as it passed through foreground galaxies. This method allowed them to even more closely examine their targets.

“Hubble is the only observatory that can carry out the observations necessary for a study like this,” says lead author Sanchayeeta Borthakur, of Johns Hopkins University. “We needed a space-based telescope to probe the hot gas, and the only instrument capable of measuring the extended envelopes of galaxies is COS.”

The eureka moment came when the astronomers found the starburst galaxies in their samples showed abnormal amounts of highly ionized gases in their halos. By comparison, the control galaxies – those known to have no starburst activity – did not. Now they knew… the ionization had to be the product of the energetic winds which accompanied the birth of new stars. Armed with this information, researchers can now confidently say that galaxies which host starburst activity has taken on new parameters. Since galaxies enlarge by feeding on gas from the space around them and convert this into new stars, we realize that the ionization process will regulate future star formation.

“Starbursts are important phenomena — they not only dictate the future evolution of a single galaxy, but also influence the cycle of matter and energy in the Universe as a whole,” says team member Timothy Heckman, of Johns Hopkins University. “The envelopes of galaxies are the interface between galaxies and the rest of the Universe — and we’re just beginning to fully explore the processes at work within them.”

Burn, baby, burn…

Original Story Source: NASA/ESA Hubble Space Telescope News Release. Further reading: The Impact of Starbursts on the Circumgalactic Medium.

Watch Live Webcast: Witnessing Starbursts in the Early Universe

This schematic image represents how light from a distant galaxy is distorted by the gravitational effects of a nearer foreground galaxy, which acts like a lens and makes the distant source appear distorted, but brighter, forming characteristic rings of light, known as Einstein rings. An analysis of the distortion has revealed that some of the distant star-forming galaxies are as bright as 40 trillion Suns, and have been magnified by the gravitational lens by up to 22 times. Credit: ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al.

Recently, a multinational team of astronomers found that massive, “dusty” galaxies were churning out stars much earlier than previously believed – as early as one billion years after the Big Bang (read our article about the discovery here).

Today, March 29, 2013 at 19:00 UTC (12:00 p.m. PDT, 3:00 pm EDT) the Kavli Foundation is hosting a live Google+ Hangout: “Witnessing Starbursts in the Early Universe.” You’ll have the chance to ask your questions about starburst galaxies, the early Universe and the incredible research being conducted by the South Pole Telescope and the Atacama Large Millimeter/submillimeter Array(ALMA) in Chile. Watch live in the window below, or see the replay later if you miss it live.

Science writer Bruce Lieberman will moderate, and three members of the research team will participate:

John E. Carlstrom – Leader of the 10-meter South Pole Telescope project and Deputy Director of the University of Chicago’s Kavli Institute for Cosmological Physics.
Dan P. Marrone – Assistant Professor in the Department of Astronomy at the University of Arizona.
Joaquin D. Vieira – Leader of the multinational team studying the galaxies discovered by the South Pole Telescope, Postdoctoral Scholar at the California Institute of Technology and member of Caltech’s Observational Cosmology Group.

Submit your questions before or during the webcast via Twitter (hashtag #KavliAstro) or by email to [email protected]

The webcast will also be available at: