Figure 1:
SWIRE View of Distant Galaxies
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Figure 2 | Figure 3 |
Figure 4 |
These spectacular images, taken by the Spitzer Wide-area Infrared
Extragalactic (SWIRE) Legacy project, encapsulate one of the primary
objectives of the Spitzer mission: to connect the evolution of galaxies
from the distant, or early, universe to the nearby, or present day, universe.
The Tadpole galaxy (main image) is the result of a recent galactic
interaction in the local universe. Although these galactic mergers are
rare in the universe's recent history, astronomers believe that they were
much more common in the early universe. Thus, SWIRE team members will use
this detailed image of the Tadpole galaxy to help understand the nature of
the "faint red-orange specks" of the early universe.
The larger picture (figure 2) depicts one-sixteenth of the SWIRE survey
field called ELAIS-N1. In this image, the bright blue sources are hot
stars in our own Milky Way, which range anywhere from 3 to 60 times the
mass of our Sun. The fainter green spots are cooler stars and galaxies
beyond the Milky Way whose light is dominated by older stellar
populations. The red dots are dusty galaxies that are undergoing intense
star formation. The faintest specks of red-orange are galaxies billions of
light-years away in the distant universe.
Figure 3 features an unusual ring-like galaxy called CGCG 275-022. The
red spiral arms indicate that this galaxy is very dusty and perhaps
undergoing intense star formation. The star-forming activity could have
been initiated by a near head-on collision with another galaxy.
The most distant galaxies that SWIRE is able to detect are revealed in a
zoom of deep space (figure 4). The colors in this feature represent the
same objects as those in the larger field image of ELAIS-N1.
The observed SWIRE fields were chosen on the basis of being "empty" or as
free as possible from the obscuring dust, gas, and stars of our own Milky
Way. Because Earth is located within the Milky Way galaxy, there is always
a screen of Milky Way objects blocking our view of the rest of the
universe. In some places, our view of the larger universe is less obscured
than others and for the most part is considered "empty." These are prime
observing spots for astronomers interested in studying objects beyond the
Milky Way. ELAIS-N1 is only one of six SWIRE survey fields. The full
survey covers 49 square degrees of the sky, equivalent to the area covered
by about 250 full moons.
The SWIRE images are 3-channel false-color composites, where blue
represents visible green light (light that would appear to be blue/green
to the human eye), green captures infrared light of 3.6 microns, and red
represents infrared emissions of 8 microns. The infrared data are from
Spitzer's infrared array camera and the visible-light data are from the
Isaac Newton Telescope, Spain.