Astronomers and space enthusiasts have been gazing at galaxies for decades, admiring their beauty and learning their secrets. However, only recently is the grand picture of galaxy formation and evolution beginning to come together. ESA's new space observatory, Herschel, is adding its powerful detection capabilities in the far-infrared to the effort.
ANALYSIS: Baby Star Blows a Bubble, Force-Feeding a Stellar 'Goliath'
Shown above is a Herschel image of the GOODS-North field. GOODS stands for Great Observatories Origins Deep Survey. Each of two fields of view measures approximately 10 to 16 arcminutes on a side and probes a region of the sky where there are few foreground stars, allowing astronomers to study galaxies from different epochs of time. (If you hold out your index finger at arm's length, the thickness of your fingernails measures about one arcminute on the sky.)
These fields have been extensively observed by space and ground-based observatories in the radio, infrared, optical, and x-ray to give a complete picture of the lives of galaxies. The far-infrared radiation detected by Herschel ranges from 250 to 500 microns in wavelength. This probes the star light that has been absorbed by dust in star-forming regions and re-emitted at these wavelengths.
Herschel is primed to study the Cosmic Infrared Background, or CIB, which peaks between 100 and 200 microns. Discovered by COBE in 1998, this has nothing to do with the famous Cosmic Microwave Background. Instead, it is most likely the faint background glow of many unresolved star-forming galaxies throughout cosmic history.
Herschel has the capability of resolving these galaxies, and has identified sources responsible for about half of this light. Most of these galaxies are located at redshifts less than one (which means within 8 billion light years, a little over halfway to the edge of the observable universe.)
Data from Herschel are also being used to look for evolution over time of the far-infrared/radio correlation (FIRRC). This is an empirical relation that shows that the amount of light given off by a galaxy in the radio (measured at 1.4 GHz) is proportional to the amount of light given off in the far-infrared.
This relation works very well for most galaxies, but the origin of this correlation is not know. Surely, something different about each galaxy should make it deviate slightly? After all, the radio and IR light don't necessarily come from the same processes, although they are both tied to star formation. A team of astronomers, led by Rob Ivison, find hints that the FIRRC is evolving with time.
Galaxies are complex and fascinating systems. Understanding their formation and evolution will tell us a heck of a lot about the universe as a whole and where our star and planet come from. Observatories such as Herschel and tools such as the CIB and FIRRC are helping us get there a little bit more every day.
Image: SPIRE composite image of the GOODS-North field. ESA/SPIRE Consortium/HerMES Key Programme Consortium.
Tags: Astronomy, ESA, Galaxies, Space Telescopes
comments ( )