Education and Public Outreach

On this page, you'll find:

Introduction to the DLS

The Deep Lens Survey is an ultra-deep multiband optical survey of five fields, each 2 degrees by 2 degrees on the sky. Using the Mosaic CCD imagers at the Blanco and Mayall telescopes, a team of some twenty researchers worldwide took five years to complete the Deep Lens Survey in four bands: B,V,R,z' to 29/29/29/28 magnitudes per square arcsecond surface brightness. The combined, deep data and catalogs for sub-fields are released to the community as they are completed. In addition, optical transient events and supernova candidates are released in real time. Moving object lists (asteroids, Kuiper Belt Objects, comets, etc.) are listed separately as they are found. Finally, the individual flat-fielded exposures are publicly available for those who wish to analyze the images themselves.

The main goal of the survey is to produce unbiased maps of the large-scale structure of the mass distribution beyond the local universe, via very deep multicolor imaging of fields and color-redshifts. The shear of distant galaxies induced by the mass of foreground structures will be measured. These weak-lensing observations are sensitive to all forms of clumped mass and will yield unbiased mass maps with resolution of one arcmin in the plane of the sky (about 120 kpc/h at z = 0.2), in multiple redshift ranges. These maps will measure for the first time the change in large scale structure from z=1 to the present epoch, and test current theories of structure formation, which predict that mass in the low-redshift universe has a particular filamentary, sheetlike structure. These observations will directly constrain the clustering properties of matter, most notably Omega_matter and Omega_Lambda, and, when compared with the results from microwave background anisotropy missions, will test the basic theory of structure formation via gravitational instability.

While this is the main goal of the survey, a wide-field imaging survey has a myriad of other uses. In addition, the group acquired the data in a way which makes it possible to detect variable objects on scales of hours to months, by spreading observations of individual subfields over 4 runs over two years. These transient events are released on the web-site in real-time.

The goal behind releasing transient events so fast is to allow for spectroscopic followup by the community while the events are still bright enough to be captured. This coming March and April dark runs at CTIO will produce transient event listings in the 10h and 14h equatorial fields, and next semester, KPNO dark runs in November and December will target the two northern fields. Transients shorter than a day or so may be very interesting: this is our first glimpse of transient phenomena at the faint 20-25 mag attainable with this 4-meter survey.

Click here for a Deep color images.

Original Press Release:

Astronomers to chart growth of massive structures in universe, Four-year tomographic mass survey begins

Using the largest telescopes of the National Optical Astronomy Observatory, in Arizona and Chile, a team of twenty astronomers has undertaken a survey of mass structures in the distant universe. Looking in many different directions deep into our universe with sensitive new-technology cameras, the Deep Lens Survey, which will take about four years to complete, will probe tell-tale systematic distortions in the images of ten million faint galaxies. Images of these distant galaxies are stretched by the space-time warps generated by foreground clumps of mass. By measuring the small shape distortions, the Survey will chart the distribution and evolution of mass structures.

An unknown form of matter, called dark matter, fills our universe. Cosmic structures, from galaxies to the universe itself, are held together by this invisible matter whose presence is known only through its gravitational effects. In addition to this huge mass, our universe may also contain a mysterious energy, called dark energy. Over cosmic time, dark matter and dark energy drive the formation of structure -- from a featureless hot cosmic soup some 14 billion years ago to the rich variety of stars and galaxies today.

Light from distant galaxies travels to us through many intervening clumps of dark matter, encoding in the distortion pattern information on the spectrum of mass concentrations. Weak lensing, as this effect is called, provides the first and currently the only way of directly "weighing" the mass distribution. Images covering a wide wavelength range enable a new kind of tomography: By obtaining weak lensing maps for ten million distant galaxies in many different areas on the sky, we can make three-dimensional mass maps of the universe back to half its current age -- charting the development of mass structures over cosmic time.

For the first time we will be able to directly survey mass -- independent of the luminosity -- of developing dark matter overdensities seven billion light-years away. Where is most of the dark matter? Does dark energy determine the fate of our universe? Comparing the resulting mass maps with data from upcoming satellite cosmic microwave background anisotropy missions will lead to a precision test of the nature of cosmic mass-energy, probing the basic theory of structure formation in our universe.

An important byproduct of this survey will be a unique monitoring of the deep universe for flashes of light -- a new window on high-energy events in distant objects. Other large telescopes around the world will investigate any such events, obtaining spectra and thus measuring the distance to the events. As with past technological advances that opened new windows of discovery, this exploration of the faint and transient universe will undoubtedly serve up surprises.

The National Optical Astronomy Observatory is operated by the Association of Universities for Research in Astronomy, through a cooperative agreement with the National Science Foundation.

For the ultimate probe of dark matter in the universe, see the Large Synoptic Survey Telescope website.

Public Participation

You and your students can look for asteroids, supernovae, and other phenomena by comparing images of the sky taken at different times. We will provide our images in almost real time to Hands-on Universe, which can provide you with software and manageable amounts of data. "Almost real time" means that if you discover something, it's not too late to follow with other telescopes.

Finally, anyone with access to telescopes is welcome to follow up the objects we discover and list on our transients page, or mine the transient pages for statistical studies of asteroids or anything else.