Wide-Field Infrared Explorer
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Wide-Field Infrared Explorer |
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THE WIRE SURVEY The WIRE survey will cover over 100 deg2 of sky and detect sources 200-500 times fainter than the IRAS Faint Source Catalog at 25µm and 500-2000 times fainter at 12µm. The resulting catalog, expected to contain at least 30,000 starburst galaxies, will reveal their evolutionary history out to redshifts of 0.5 - 1 and the evolutionary history of extremely luminous galaxies beyond redshifts of 5. WIRE will be the first significant galaxy survey to probe these redshifts at far-infrared wavelengths where extinction effects are small and where most of the luminosity of starburst galaxies, and possibly of the universe, can be measured.
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Mission Information The Science The WIRE mission consists of a four-month survey in 12 and 25 µm infrared color bands at sensitivity levels bounded by the telescope’s 25 µm confusion limit. The confusion limit is set by the density of the many faint, unresolved sources in the field of view and the resolving power of the telescope. The WIRE survey will detect primarily galaxies with unusually high rates of star formation or "starburst" galaxies which emit most of their energy in the far-infrared. The number of these faint sources at a given flux level depends on their as yet unknown evolutionary rate. One of the most important goals of modern astronomy is to understand the formation and evolution of galaxies. Starburst galaxies are an important population because they represent 30% of the energy budget of the local universe and because almost all of their luminosity is due to star-forming regions. They represent more than 30% of the star formation occurring today. If starburst galaxies have evolved, then they may represent the main source of stars in the universe. WIRE will help reveal the role of starbursts in the evolution of all galaxies. Models of protogalaxies also predict ultraluminous starbursts at early epochs, implying that WIRE may determine when galaxies formed. The objective of the WIRE mission is to answer three questions:
The scientific impact of the WIRE data will be immediate. The number of sources as a function of flux density will indicate the rate of evolution of the starburst galaxy population, that is, the variation of the number and luminosity of these galaxies with cosmic epoch. The infrared color distribution of sources detected as a function of flux density will reveal the nature of the evolution of starburst galaxies and point to protogalaxy candidates. Follow-up observations at other wavelengths will test our assumptions and lead serendipitously to new discoveries. The WIRE survey reaches so deeply into unexplored territory that it presents a significant opportunity for scientific investigation and discovery in many areas. Examples of additional investigations include exploring the proposed link between quasars and ultraluminous galaxies, searching for brown dwarfs, searching for circumstellar disks around main sequence stars and exploring the large-scale distribution of galaxies at high redshifts. There is great potential for discovery of entirely new phenomena at these faint flux levels.
Resolution (FWHM): 15 arcsecond at 12µm, 22 arcsecond at 24µm Exposure Time: ~1 minute/exposure, ~103-104 seconds/field Observing Efficiency: 70%
Author: Jim Watzin
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jim.watzin@gsfc.nasa.gov) |
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This color image is a simulation of the faint mid-infrared
sky as it may appear to WIRE. The image was constructed from
simulations of 25 µm and 12 µm WIRE images of a field located
near the North Galactic Pole. The field is approximately 0.5°
on each side, and over 200 objects are visible. Stars are the
blue objects, and galaxies, most of which are undergoing a
burst of star formation, range from green to red. (The colors
of the brightest objects are distorted because we cannot
fully represent the dynamic range of the WIRE data in this
rendering). The red galaxies tend to be the most luminous and
distant ones. The redshift distribution of galaxies in the
image peaks near z=0.5, and our model assumes that the galaxy
population is weakly evolving with lookback time. The
brightest galaxy near the lower right corner has a 25 µm flux
density of 87 mJy. The faintest discrete sources visible have
25 µm flux densities less than 0.5 mJy. The lumpy red
background is the confusion noise caused by multitudes of
still fainter overlapping galaxies. Simulated by David Shupe
(IPAC/JPL) and A. Kris Huber (Utah State University).
