Astronomers using the International Gemini Observatory’s Gemini North Telescope have imaged NGC 4449, a prime example of starburst activity caused by an ongoing merger with a nearby dwarf galaxy.
NGC 4449 is located in the constellation Canes Venatici and is about 12.5 million light-years away from Earth.
Also known as Caldwell 21, LEDA 40973, and UGC 7592, the galaxy has a diameter of about 20,000 light-years.
NGC 4449 was discovered on April 27, 1788, by German-born British astronomer William Herschel.
It is part of the M94 galaxy group, located near the Local Group, which contains our own Milky Way galaxy.
“The galaxy’s rolling red clouds and glowing blue veil light up the sky with the color of newly forming stars,” the astronomers said.
“The galaxy is classified as an Irregular Magellanic Galaxy, reflecting its loose spiral structure and similarity to the Large Magellanic Cloud, the prototype of the Magellanic Cloud.”
Stars have been forming actively within NGC 4449 for billions of years, but new stars are currently being produced at a much higher rate than in the past.
This unusually explosive and intense star formation activity qualifies this galaxy to be called a starburst galaxy.
“While starbursts typically occur in the centers of galaxies, star formation in NGC 4449 is more widespread, as evidenced by the fact that the youngest stars are found both in the galaxy’s central core and in the outflow that surrounds the galaxy,” the researchers said.
“This global starburst activity resembles the earliest star-forming galaxies in the universe, which grew by merging and agglomerating with smaller stellar systems.”
“And like its galactic progenitors, NGC 4449’s rapid star formation is likely driven by interactions with nearby galaxies.”
A member of the M94 galaxy group, NGC 4449 sits very close to several smaller galaxies around it.
Astronomers have found evidence of interactions between NGC 4449 and at least two other satellite galaxies.
One is a very faint dwarf galaxy that is actively absorbing, as evidenced by the diffuse streaming of stars on one side of NGC 4449.
“This stealthy merger is nearly undetectable by visual inspection due to its diffuse nature and low stellar mass,” the scientists said.
“But this galaxy harbors a huge amount of dark matter, and we can detect its presence through its large gravitational influence on NGC 4449.”
“Another object that offers a clue to past mergers is a massive globular cluster embedded within the outer halo of NGC 4449.”
Astronomers believe the cluster is the surviving core of a former gas-rich satellite galaxy that is now being absorbed into NGC 4449.
“As NGC 4449 interacts with and absorbs other, smaller galaxies, the gas is compressed and shocked by tidal interactions between the galaxies,” the astronomers said.
“Red glowing regions scattered throughout the image indicate this process, showing an abundance of ionized hydrogen, a clear sign of ongoing star formation.”
“Dark filaments of cosmic dust that thread their way throughout the Galaxy are causing countless hot, young, blue star clusters to emerge from the galactic oven.”
“At the current rate, NGC 4449’s supply of gas to support star formation will last only another billion years or so.”
Source: www.sci.news
