Dr. Alexander Kashlinsky, Senior Staff Scientist, SSAI, Goddard Space Flight Center, Greenbelt, MD
- Monday, 30 March 2009
Kashlinsky: This project and the group of us working on it — it’s myself, Dave Fixsen, and John Mather here at Goddard Space Flight Center — what it is designed to measure is the structure of the cosmic infrared background radiation at far infrared bands.
Why COBE FIRAS? FIRAS is the Far Infrared Absolute Spectrophotometer that was launched onboard the COBE satellite, the satellite that discovered cosmic microwave background structure. That instrument measured the spectrum of the cosmic microwave background radiation and it determined that it is a basic black body spectrum, basically down to almost one part in 1,000,000. But it also gave us very useful maps to work with for other parts of science. It measured all sky maps at the various far infrared wavelengths. Because we know the spectrum of the cosmic microwave background radiation, we can remove it from these maps very well. Then, if we’re lucky — and by lucky I mean if we can remove other foreground, such as our own galaxy, sufficiently well — we can then determine how much is produced by distant galaxies at far infrared wavelengths. That will give us very important cosmological information as to how these galaxies lived when they produced these emissions, how much of these emissions they produced, and so on and so forth. This project is just beginning, so I don’t know what our results will be, but the hope is to isolate the fluctuations in the cosmic infrared background radiation after subtracting the cosmic microwave background radiation from the FIRAS maps.
NTB: You mentioned that one of your co-investigators on this project is Dr. John Mather, the 2006 Nobel Laureate in physics. Do you ever find yourself dreaming of one day possibly winning a Nobel Prize, or is that something scientists don’t really think about until it happens?
Kashlinsky: Oh, I think it’s the latter. It just doesn’t cross the mind, I would say, of most scientists because you are so busy trying to understand whether the results you are measuring are real; what the systematics are; what the statistical significance is; whether you have been fooled by the various other processes that you have not accounted for; that it doesn’t give you much time to stress or share thoughts. So no, I don’t spend time thinking about it. And once you produce results, you really are worried that these are real results; that they can be maintained by future measurements; and you should always seek confirmation of these results, so no, there’s not much time to think about that.
NTB: What are some of the other significant projects you’re either working on, or anticipate working on, in the future?
Kashlinsky: It’s a very fortunate era now in the field of cosmology. I remember when I was starting my PhD, there was very little data to go by and there were many ideas, but also the theoretical part of the field was not particularly developed as I look back at it now. Slowly but surely, theoretical understanding developed and then, what’s even more important, in the last, I would say, ten or fifteen years there has been an explosion in the data – high quality data – that has been obtained in this field. This data comes from various space observatories or satellites such as the COBE satellite. It was a very important point in cosmology, and it was reached also thanks to the new generations of ground telescopes that can see very far with very high resolution and very low noise.
So, today you have a lot of data that can really constrain your understanding of the theoretical issues of the universe, and these data come at various wavelengths. For instance, in terms of cosmic microwave background measurements, there was COBE, then there was WMAP (Wilkinson Microwave Anisotropy Probe), which is still operating. It’s a superb instrument. And the Europeans are going to launch, this spring, the successor to WMAP, called the Planck satellite, which should bring a lot of new cosmic microwave background radiation data over a very wide range of frequencies with very low noise and with fairly good angular resolution. That is one of the projects we’re thinking to do with the dark flow studies; we want to try it with the Planck data.
At other wavelengths there is the Spitzer satellite, which is still operating. It is now about to begin its so-called warm mission because it’s run out of cryogens, so it has been extended for warm mission and it should still bring some very important data for understanding distant populations and the cosmic infrared background radiation emitted by them.
You can also go to a completely unexpected range of wavelengths or energies. At very high energies there is now operating… The GLAST (now renamed Fermi) satellite, which is the successor to the Compton Gamma Ray Observatory, and it is going to map the universe very well at gamma ray wavelengths and find a lot of distant gamma ray sources, gamma ray bursts, and so on. This would also be important in terms of studying early stellar populations because – this is one of the projects I hope to do with the data – you should see a very distinct cutoff in the spectrum of gamma-ray sources (bursts and blazars) at very large distances. This is produced by the cosmic infrared background from very early sources, such as Population 3, or the first black holes, and it is produced because the energy that these sources emit, which reach us in the infrared band, would also contain a lot of photons, and the very high-energy photons produced by these gamma ray bursts then would flow in the sea of IR photons – the cosmic infrared photons produced by the first stars – and they would get absorbed at sufficiently high energies by the so-called photon-photon absorption process. So, you should see a certain spectral feature that would tell you, yes, this is the epoch where these first stars lived. Maybe they lived for the first hundred-million years, maybe they lived for the first two-hundred-million years, and so on. You should be able to see the feature, if they produced enough energy.
And, of course, there are preparations for science that can be done with the James Webb Space Telescope, the JWST, which is going to be launched four or five years from now. That would be a successor to Hubble, but it also measures the universe in infrared bands, so it would see very far. It would see at completely different wavelengths, and it would bring a lot of data and probably revolutionize our understanding of the evolution of the universe.
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