NGC 4753’s prominent and complex network of dust lanes that twist around its galactic nucleus define its ‘peculiar’ classification and are the likely result of a galactic merger with a nearby dwarf galaxy about 1.3 billion years ago.
This image from the Gemini South telescope, one half of the International Gemini Observatory operated by NSF’s NOIRLab, shows NGC 4753, a lenticular galaxy some 60 million light-years away in the constellation Virgo. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / J. Miller, International Gemini Observatory & NSF’s NOIRLab / M. Rodriguez, International Gemini Observatory & NSF’s NOIRLab / M. Zamani, NSF’s NOIRLab.
NGC 4753 is a lenticular galaxy located about 60 million light-years away in the constellation Virgo.
Otherwise known as LEDA 43671, UGC 8009 or IRAS 12498-0055, the galaxy was discovered by the German-born British astronomer William Herschel on February 22, 1784.
NGC 4753 is a member of the NGC 4753 group of galaxies within the Virgo II Cloud, a series of at least 100 galaxy clusters and individual galaxies stretching off the southern edge of the Virgo Supercluster.
“An astounding number of galaxies populate the observable Universe, with recent estimates placing that number anywhere from 100 billion to 2 trillion,” the Gemini astronomers said in a statement.
“And, akin to snowflakes, no two are exactly alike. But depending on their visual appearance and physical features they can be divided into four broad classes: elliptical, lenticular, irregular and spiral, with many subclasses in between.”
“However, galaxies are dynamic objects that evolve over time as they interact with their surrounding environment, meaning that an individual galaxy may fall under multiple classifications throughout its lifetime.”
In 1992, Indiana University astronomer Tom Steiman-Cameron and his colleagues published a detailed study of NGC 4753 in which they found that its complicated shape is likely the result of a merger with a small companion galaxy.
“Galaxies that gobble up another galaxy often look like train wrecks, and this is a train-wreck galaxy,” Dr. Steiman-Cameron said.
Galaxy mergers occur when two or more galaxies collide, causing their material to mix and significantly altering the shape and behavior of each galaxy involved
In the case of NGC 4753, it is thought that the once standard lenticular galaxy merged with a nearby gas-rich dwarf galaxy about 1.3 billion years ago.
The gas of the dwarf galaxy, coupled with bursts of star formation triggered by this galactic collision, injected the system with vast amounts of dust.
The galaxy’s inward spiral due to gravity then caused the accumulated dust to smear out into a disk shape. And this is where the story gets interesting.
The astronomers found that a phenomenon known as differential precession is responsible for NGC 4753’s entangled dust lanes.
Precession occurs when a rotating object’s axis of rotation changes orientation, like a spinning top that wobbles as it loses momentum. And differential means that the rate of precession varies depending on the radius.
In the case of a dusty accretion disk orbiting a galactic nucleus, the rate of precession is faster toward the center and slower near the edges.
This varying, wobble-like motion results from the angle at which NGC 4753 and its former dwarf companion collided and is the cause of the strongly twisted dust lanes we see wrapped around the galaxy’s luminous nucleus today.
“For a long time nobody knew what to make of this peculiar galaxy,” Dr. Steiman-Cameron said.
“But by starting with the idea of accreted material smeared out into a disk, and then analyzing the three-dimensional geometry, the mystery was solved.”
“It’s now incredibly exciting to see this highly-detailed image by the Gemini South telescope 30 years later.”
Source : Breaking Science News