Galactic mergers and the Standard Big Bang Cosmological Model

The Model Universe

  • Among the most conspicuous features found in our survey are coherent structures that resemble an open umbrella extending tens of kiloparsecs into the host spiral's halo. These spectacular formations are often located on both sides of the principal galaxy and display long narrow shafts that terminate in a giant partial shell of debris. The most remarkable example so far detected is NGC 4651 Photo credit: R. Jay GaBany, Cosmotography.com


Home | « Previous | Pages:
  1. Overview
  2. |
  3. Description
  4. |
  5. Team
  6. |
  7. Targets
  8. |
  9. Science
| Next »


The



About 14 billion years ago the Universe began expanding in all directions from an infinitesimally small, infinitely dense point or singularity. This event is known as the Big Bang.
  • Located just 100 kilometers off the western coast of northern Africa, the Canary Islands form an archipelago that includes Tenerife and La Palma.
Within the first few seconds following the onset of the rapid inflation, and lasting for the next hundred thousand years, the fundamental particles that would later comprise matter came into being but matter as we know it did not yet exist. During this period, the Universe was opaque, filled with intensely hot plasma and various forms of powerful radiation.

However, as the expansion of the Universe continued, its temperature and density gradually decreased. Plasma and radiation was eventually replaced by hydrogen and helium, the simplest, lightest and most abundant elements in the Universe, even today. Gravity required several hundred million additional years to coalesce these free-floating atoms into the primordial gas out of which the first stars and galaxies emerged.

This explanation about the beginning of time was derived from the standard model of big bang cosmology, also known as the Lambda Cold Dark Matter cosmological model of the Universe or simply the Lambda CDM. A cosmological model is a mathematical description of the Universe that attempts to explain its current behavior and evolution over time. Cosmological models are based on direct observations. They are capable of making predictions that can be validated by subsequent investigations and are based on general relativity because that theory produces the best agreement with large-scale behaviors that have been observed. Cosmological models are also rooted in two basic assumptions:

  • The Earth is not located at the center of the Universe nor does it occupy a special place therefore the Cosmos looks the same in all directions and from every location on a grand scale and
  • the same laws of physics which operate on Earth also function throughout the Universe regardless of time.

Therefore, what we observe today can be used to explain past, present or help predict future events in nature no matter how remote the phenomenon is located.

Incredibly, the farther we peer out into the heavens, the farther we gaze back into the past. This allows us to conduct a general survey of galaxies when they were much younger so we can better understand how they evolved to those that are closer, and therefore much older. Of course, we cannot see the same galaxies at different stages in their development. But we can have a good idea by grouping galaxies into categories based on what we observe.

Since the first galaxies are believed to have formed from gas clouds shortly following the beginning of the Universe, the standard big bang model expects we will find the earliest galaxies filled with young, hot stars that will give these early galaxies a blue hue. The model also predicts the first galaxies were more numerous and much smaller than those of the present day and that star systems grew to their current size hierarchically as the small galaxies merged and formed larger island universes over time.
  • Located just 100 kilometers off the western coast of northern Africa, the Canary Islands form an archipelago that includes Tenerife and La Palma.


Interesting, many of these predictions have been validated. For example, as early as 1995 when the Hubble Space Telescope first looked deep toward the beginning of time, it found the young Universe was filled with faint blue galaxies that were thirty to fifty times smaller than our Milky Way.

The standard big bang model also predicts these mergers are still continuing therefore we should find evidence of this activity in relatively close by galaxies, too. Unfortunately until recently, there has been little evidence of merger activity among galaxies near the Milky Way. This has been a problem with the standard big bang model because it suggested our understanding of the Universe might be incomplete or flawed.

So, for the past few years an international team of professional researchers, led by Dr. David Martinez-Delgado (Max Planck Institute for Astronomy), has conducted a preliminary survey of selected nearby galaxies seeking evidence of galactic mergers by producing extremely long, deep photographic exposures using modest sized telescopic instruments located under dark, clear, steady night skies. For example, extrapolating photometric information from images produced with the Sloan Digital Sky Survey (SDSS) these small aperture images reached 10 times deeper than the SDSS, capturing features fainter than magnitude 28 (for comparison, the SDSS images reach magnitude 25 and the deepest Hubble images reach magnitude 31.5).

The results of this survey produced several discoveries that provided evidence of ancient galactic mergers which match the standard model's predictions.

For example, the initial results revealed fossil satellite relics in the form of vast rings surrounding host galaxies as seen in deep images of NGC4013 and NGC5907. These enormous loops represent streams of stars shorn from long gone companion galaxies that were gravitationally disrupted and absorbed into the larger spiral they orbited.
  • Rings are not the only structures left behind to evidence an ancient satellite disruption and accretion.


But, rings are not the only structures predicted by the standard model when a satellite merges with its parent.

For example, NGC4651 is located about 35 million light-years from Earth. Surrounding this galaxy is a shell of debris that indicates a satellite merger took place long ago in the past. Also evident is a narrow, jet-like trail that is superimposed over the face of the galaxy. Both ends of this structure are sheared and represents further evidence of the titanic gravatational forces that ripped the satellite into shreads as it was flug around. This image, produced by combining an hour of exposure through the Isaac Newton Telescope located on the spanish island of La Palma with over 13 hours through the half meter telescope at the Blackbird Observatory in New Mexico (USA).     More »


Download the full PDF documentation.








Home | « Previous | Pages:
  1. Overview
  2. |
  3. Description
  4. |
  5. Team
  6. |
  7. Targets
  8. |
  9. Science
| Next »