The massive multiphase outflows known as galactic winds are a distinguishing feature of galaxies during star formation. These galactic winds have significant impacts on their host galaxies, altering the metal composition of the disk and enriching the surrounding circumgalactic medium (CGM) and intergalactic medium (IGM) (IGM).

A new research utilizing the Chandra X-ray Observatory at NASA reveals the impact of tremendous winds emitted from the core of the neighboring galaxy NGC 253. NGC 253 is a close, edge-on starburst located around 11,400,000 light-years from Earth. Throughout the electromagnetic spectrum, its multiphase outflow has been extensively explored.

Chandra found out how galaxies move around.

The wind of the galaxy consists of gas with temperatures of millions of degrees that emits X-rays. A quantity of hot gas equal to about two million Earth masses is expelled annually from the core of the galaxy.

NGC 253’s rate of star production is two to three times that of the Milky Way. Some of these young, massive stars produce wind by violently exhaling gas from their surfaces. Later in their lives, when these stars explode as supernovae, they release winds that are much more violent.

NGC 253 provides astronomers with a peek into this important phase of a star’s life cycle. Materials produced within the newborn stars enhance the matter they emit hundreds of light-years into interstellar space. These elements, many of which are fundamental to life on Earth as we know it, are absorbed into the forthcoming stars and planets.

Chandra data (pink and white) are incorporated in the new composite picture of NGC 253 in the inset, illustrating how these winds sweep away from the core of the galaxy in two opposite directions, to the upper right and lower left.

Infrared data from NASA’s Spitzer Space Telescope, visible light data from a 0.9-meter telescope at Kitt Peak Observatory, and hydrogen emission data are also visible in this picture (red). The larger picture in the graphic, which depicts an optical view from the La Silla Observatory of the European Southern Observatory in Chile, demonstrates how NGC 253 looks nearly edge-on from Earth’s vantage point.

Chandra found the motion of galaxies.

A group lead by Sebastian Lopez of The Ohio State University in Columbus, Ohio, examined the characteristics of wind using Chandra data. Scientists discovered that the densities and temperatures of the gas in the wind are greatest at places fewer than 800 light-years from the center of the galaxy, and drop with increasing distance.

These findings contradict an early notion that proposed so-called starburst galaxies, such as NGC 253, had spherical winds. Current theoretical analyses show that a ring of “super star clusters” near the core of NGC 253 ought to generate a more concentrated wind. In star clusters, several large, young stars can be discovered.

The concentrated character of the wind supports the hypothesis that the star clusters observed by the scientists represent a substantial wind source. Yet, the lack of agreement between theory and facts raises the likelihood that the theory is lacking in certain fundamental ideas.

Scientists stated, “The discovery that the wind cools rapidly as it goes out from the center of the galaxy provides a clue as to what is lacking. This indicates that the wind is transporting colder gas, causing it to cool and slow down. Such a ‘wind plow’ effect might be the additional physics necessary for a better fit between theory and data.”

Also, the researchers examined the composition of the wind. Particularly, they examined the distribution of oxygen, neon, magnesium, silicon, sulfur, and iron throughout the structure. They discovered that these elements become significantly more diluted as distance from the galactic center increases. Scientists did not see such a dramatic fall in the quantities of these elements in the wind of M82, a well-studied galaxy undergoing a burst of star creation.

Further investigations of additional galaxies with winds will be necessary for astronomers to determine if this difference is connected to the general features of galaxies, such as the overall mass of stars they contain.

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