By using the
"lens" gravitational in space, astronomers at the University of Utah
found that the center of the largest galaxies grow into more dense -
giving evidence of the collision and merging repeatedly between giant
galaxies.
"We found that over the last 6 billion years, the material that forms a
giant elliptical galaxy more concentrated towards the center of the
galaxy.
This is evidence that large galaxies crashing into other large galaxy to
make the larger galaxy, "said astronomer Adam Bolton, lead author of
the new study.
"The most recent studies have previously shown that massive galaxies
grow by way of preying galaxies smaller in quantity," he added. "We show that the collision between big galaxies is as important as a lot of snacks."
This new study - published in The Astrophysical Journal Bolton-done by a team from the Sloan Digital Sky Survey-III using the telescope optical width of 2.5 meters at Apache Point, NM, and the Hubble Space Telescope orbiting Earth.
Telescopes has been used to observe and analyze the 79 "gravitational
lens", which is between the earth and the galaxy galaxies at a greater
distance.
Gravitational lens galaxies are useful in deflecting light from the
more distant galaxy, creating a ring or partial ring of light around the
lens galaxy.
Ring size was used to determine the mass of each galaxy in the lens,
and the speed of the stars used to calculate the concentration of mass
in each galaxy lenses.
Bolton worked on this study along with the three other astronomers from
the University of Utah - postdoctoral researcher Joel Brownstein,
graduate students and undergraduate Yiping Shu-Ryan Arneson also with
members of the Sloan Digital Sky Survey: Christopher Kochanek of Ohio
State University; David Schlegel of Lawrence Berkeley National
Laboratory; Daniel Eisenstein of the Harvard-Smithsonian Center for
Astrophysics; David Wake of the University of Yale; Natalia Connolly
from Hamilton College, Clinton, NY; Claudia Maraston from the University
of Portsmouth, England, and Benjamin Weaver of the University of New
York.
Great food and snacks for the giant elliptical galaxy
The new study is dealing with the kind of elliptical galaxies are the
largest ever known, each containing about 100 billion stars. By calculating the " dark matter "that is not visible, the galaxies containing a mass of about 1 billion stars like our sun.
"They are the end product of all collisions and merging galaxies
previous generations, maybe hundreds of collisions," said Bolton.
Although recent evidence from other studies suggests that the giant
elliptical galaxies grow by preying galaxies are much smaller, but
Bolton earlier computer simulations show that collisions between
galaxies are the only major galaxy mergers that lead to increased
density in the center of the giant elliptical galaxy.
When a small galaxies merge with larger ones, the pattern was different. Smaller galaxies torn apart by the gravity of massive galaxies. The stars of the small galaxies stay close to the outskirts of the galaxy, not its center.
"But if you have two galaxies are roughly comparable, and both are on a
collision course, then each of the more penetrating to the center of
each other, so there is more mass that ends up in the center," said
Bolton.
Other recent research suggests that the stars spread further into the
galaxy from time to time, supporting the idea that large galaxies prey
galaxies are much smaller.
"We found that these galaxies are more concentrated on the mass of them
from time to time though less concentrated on the light they give off,"
says Bolton.
Bolton believes that collisions between large galaxies to explain the
growth of the mass concentration, whereas galaxies swallowing smaller
galaxies explain distant starlight from the galaxy center.
"Both of these processes is important to explain the whole picture," said Bolton.
"The way the light of the development can not be explained by the
massive collision, so we really need both types of collisions, ie
collisions of large and small - Its great in small amounts and in large
quantities."
The study
also shows that collisions between galaxies are "dry collision" - that
is, galaxies colliding gas shortages in large numbers because most of
the gas is frozen to form a star - and that these galaxies are colliding
not hit each other in the position angles to each other, or who termed
Bolton as a "blow grazed".
Meet Sloan Hubble: How to Study Guide
University of Utah joined the third stage of the Sloan Digital Sky Survey, which is known as SDSS-III, in 2008.
By involving some 20 research institutions around the world, a project
that continued until 2014 is an international effort to map the space as
a way to search for giant planets in other solar systems, study the
origin of galaxies and the expansion of the universe, as well as
investigating dark matter and mysterious dark energy that make up most
of the universe.
Bolton said that the new study is "almost soupy" to include an SDSS-III
project called BOSS (Baryon Oscillation spectrographic Survey). BOSS seeks to measure the expansion history of the universe with a precision that has never happened before. It allows scientists to study dark energy accelerating the expansion of the universe.
The universe is believed to consist of only 4 percent ordinary matter,
24 percent of "dark matter" invisible and 72 percent dark energy
as-yet-unexplained.
During the study BOSS galaxies, the computer analyzes the spectrum of
light emitted gravitational lens galaxies reveal dozens, were found as
natural signs of two different galaxies are in one line.
Image from the Hubble Space Telescope is the same as the previous image, but not through the same processing.
As a result, Einstein ring of distant galaxies become less sharp, but
the galaxies 'gravitational lens' it becomes visible in the center of
the image. (Credit: Joel Brownstein, University of Utah, for the NASA / ESA and the Sloan Digital Sky Survey)
The study involved 79 Bolton observed gravitational lenses from two surveys:
- Sloan Survey and the Hubble Space Telescope that collects images and color spectrum of light emitted old galaxies are relatively close - accounts for 57 gravitational lenses - 1 billion to 3 billion years in the past.
- Another survey identified 22 lenses among young galaxies within more distant, from 4 billion to 6 billion years in the past.
The ring of light around the gravitational lens galaxies called the
"Einstein ring" as Albert Einstein once predicted effect, even though he
was not the first to do so.
"The galaxies are further transmit the scattered light rays, but the
rays passing near the galaxy closer to unity can be bent light rays
appear to us as the light ring around the galaxy close," said Bolton.
The greater the amount of material in a lens galaxy, the greater the ring.
It seems counter intuitive, but the larger mass has a gravitational pull
enough to make the trajectory of such a cornering light of distant
stars that can be seen by the observer, creating a larger ring.
If there is more material concentrated near the center of the galaxy,
the stars will appear to move faster toward or away from the galactic
center, said Bolton.
Alternative Theories
Bolton and his colleagues acknowledge that their observations could be
explained by other theories besides the idea that the galaxies condense
head from time to time:
- The gas collapsing to form stars may increase the concentration of mass in a galaxy. Bolton found the stars in these galaxies are too old to corroborate this explanation.
- Gravity of the biggest galaxies stripped galaxies "Satellite" at the edges, leaving more mass is concentrated at the center of the satellite galaxy. Bolton found the process may not result in the concentration of mass that has been observed in the new study and explain how the level of the center of mass developed from time to time.
- The researchers only detect galaxies at each boundary between the inner region and the star-dominated outer region, which is dominated by invisible dark matter. Under this hypothesis, the display of mass concentration of galaxies evolve from time to time it is because of a fluke in the method of measurement of the researchers - they measure young galaxies in areas further away from the center and old galaxies measured on a more close to its center, presenting the illusion of mass concentration in the center of galaxies grow over time. Bolton argued that the difference measure is too small to explain the observed pattern in the density of matter in the galaxy-galaxy lenses.
