With the help of the Hubble Space Telescope, a team of scientists have determined that the El Gordo galactic cluster is even more massive than previously thought.
The El Gordo cluster is considered as the largest galactic cluster ever discovered. However, the latest data from Hubble indicates that the cluster is definitely living up to its name. El Gordo means "the fat one in Spanish" and scientists have found that the cluster contains hundreds of galaxies. El Gordo has also been catalogued as ACT-CL-J0102-4915.
The scientists were able to estimate the galactic cluster's mass by measuring the gravitational lensing caused by El Gordo. Due to the mass of the cluster, the images of background galaxies found in more distant locations can warp around El Gordo. By measuring the effects of the lensing, scientists were able to determine that the cluster is around 3 million billion times more massive than the Sun.
"It's given us an even stronger probability that this is really an amazing system very early in the universe," said University of California physicist James Jee. Jee is also the leader of the team that made the calculations.
While galaxies are considered as some of the most massive objects in the universe, the mass of the galaxies in the cluster only make up a smaller percentage of the cluster's total mass. Some of the cluster's mass can be found in dark matter while most of the cluster's mass can be attributed to the hot gas filling most of the space in El Gordo.
The scientists who studied El Gordo also said that the sheer massiveness of El Gordo may mean that the current cluster is the result of a collision of two smaller clusters sometime in the past.
"We wondered what happens when you catch a cluster in the midst of a major merger and how the merger process influences both the X-ray gas and the motion of the galaxies," said Rutgers University's John Hughes. "So the bottom line is that because of the complicated merger state, it left some questions about the reliability of the mass estimates we were making." Hughes is part of the university's Department of Physics and Astronomy.
Estimating the mass of a cluster is a difficult task. In the case of El Gordo however, the problem is further complicated by the fact that the cluster is the result of a merger between two previously separate clusters.
"That's where the Hubble data came in," said University of Illinois astronomer Felipe Menanteau. "We were in dire need for an independent and more robust mass estimate given how extreme this cluster is and how rare its existence is in the current cosmological model. There was all this kinematic energy that could be unaccounted for and could potentially suggest that we were actually underestimating the mass."
While the latest images from Hubble has helped the team make more accurate calculations about the probable mass of El Gordo, the scientists plan on creating a larger mosaic composed of a set of smaller Hubble Images. Due to the sheer size of the massive galactic cluster, a single image won't cut it since Hubble's entire field of view is too narrow to contain the entire cluster.
"We can tell it's a pretty big El Gordo, but we don't know what kind of legs he has, so we need to have a larger field of view to get the complete picture of the giant," added Menanteau.
