Beth Reid on the Success of the SDSS Collaboration
Fast Breaking Papers Commentary, April 2011
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Article: Cosmological constraints from the clustering of the Sloan Digital Sky Survey DR7 luminous red galaxies
Authors: Reid, BA, et al. |
Beth Reid talks with ScienceWatch.com and answers a few questions about this month's Fast Breaking Paper paper in the field of Space Science.
Why do you think your paper is highly
cited?
The Sloan Digital Sky Survey (SDSS) was an enormously successful project that imaged a quarter of the sky and obtained more than 1 million redshifts. This paper presents an analysis of galaxy clustering on large scales from the final data release of the survey.
It is highly cited because our measurement can be used to constrain both the geometry of the universe through the redshift-distance relation between us and our galaxy sample as well as the statistics of the matter fluctuations in our universe. Any new cosmological model has to be able to reproduce our measurement.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Galaxy clustering is one of several observational pillars of modern cosmology. The major advance of this work over earlier analyses, apart from having a larger sample, is the careful assessment of the impact of "galaxy physics"—the nitty-gritty details of how the galaxies trace the underlying matter fluctuations.
"An essential part of the success of SDSS is that its data is completely public, so that everyone has the opportunity to do science with this amazing dataset—and many people outside of the SDSS collaboration have!"
We approached the problem from both sides: first, we developed a method to find the centers of dark matter potential wells called "halos" from the galaxy density field we measure; second, we generated a large set of mock catalogs which match on other observable quantities from our galaxy sample in order to calibrate our model. All of this hard work allowed us to confidently use a factor of 8 more of the information available from the survey in our analysis.
Would you summarize the significance of your paper
in layman's terms?
Our analysis confirms the basic "concordance" cosmological model—the fluctuations that give rise to the cosmic microwave background (CMB) are statistically consistent with the types of fluctuations we measure in the galaxy distribution; that is, the tiny fluctuations (1 in 100,000) we can see in the CMB grew through gravitational instability and eventually formed galaxies in regions where there is more matter than average.
Using our measurements, we were able to place stringent constraints both on the number of relativistic species in the early universe (which affect the early cosmic expansion history), the sum of the mass of neutrinos (which suppresses matter fluctuations on small scales), and the geometry of the universe (through a measurement of the distance to our galaxy sample). The first two relate to exploring physics beyond the standard particle physics model, while the latter provides evidence for dark energy.
How did you become involved in this research, and
how would you describe the particular challenges, setbacks, and
successes that you've encountered along the way?
I worked on modeling the primary large-scale structure galaxy sample ("luminous red galaxies") of the SDSS during my Ph.D. thesis in order to understand some mysteries in previous measurements. As I finished up, I was given the remarkable opportunity to apply my work to the final analysis of the SDSS sample.
Where do you see your research leading in the
future?
Galaxy clustering is essential in observational cosmology for (at least) two reasons. Since the fluctuations in the galaxy distribution and the CMB are the same, we are able to use them as a "standard ruler" to measure the cosmic expansion history and thereby map out the effects of dark energy. Second, there are distortions in the measured galaxy density field due to galaxy velocities on top of the Hubble flow; these provide a unique snapshot of the rate at which cosmic perturbations are growing today, and provide a distinct probe of dark energy.
I am currently working on a component of SDSS-III called Baryon Oscillation Spectroscopic Survey (BOSS), which builds on the legacy of SDSS and extends the sample out to higher redshift. BOSS will measure both of these effects to unprecedented precision.
Do you foresee any social or political
implications for your research?
An essential part of the success of SDSS is that its data is completely
public, so that everyone has the opportunity to do science with this
amazing dataset—and many people outside of the SDSS collaboration
have!
Beth Reid
Hubble Fellow
Lawrence Berkeley National Lab
Berkeley, CA, USA
Related information:
Read the many features within ScienceWatch.com regarding the Sloan Digital Sky Survey.
KEYWORDS: COSMOLOGY, OBSERVATIONS, LARGE-SCALE STRUCTURE OF UNIVERSE, GALAXIES, HALOES, STATISTICS, HALO OCCUPATION DISTRIBUTION, SPECTROSCOPIC TARGET SELECTION, POWER SPECTRUM ANALYSIS, PROBE WMAP OBSERVATIONS, HUBBLE SPACE TELESCOPE, BARYON ACOUSTIC PEAK SURVEY IMAGING DATA, REDSHIFT SPACE, DATA RELEASE.