Computing Images

Expo/Science & Industry/Whispers From the Cosmos

Insight Through Images

BIMA Consortium

Integrated intensity maps of Orion-S.

Essential to radioastronomy, computers transform the raw data gathered by radiotelescopes into pictoral representations whose scientific significance is grasped quickly by the trained eye. Unlike most optical telescopes that directly the focus the incoming lightwaves into images, radiotelescope arrays rely on computers to record the signals from each of the receiving dishes, combine these signals and generate images from the integrated data. In this manner, the array acts as if it were one large telescope.

Jack Welch, Univ. of California at Berkeley, on-camera

QuickTime Movie (2.0 MB); Sound File (1.1 MB); Text

After an observing run is completed, several computational procedures are used to process the collected data. The resulting sets of data are then visualized with the aid of special software, yielding radiomaps. Astronomers intentionally make these radiomaps look like photographs that can be understood with ease.

Dick Crutcher, NCSA/University of Illinois, on-camera

QuickTime Movie (1.1 MB); Sound File (687K); Text

Radiomaps

The following images provide examples of the diverse ways to represent radioimaging data. All but the last depict the galaxy M82, as observed in the carbon monoxide (CO) spectral line.

Spectral Line Graphs

These spectral line graphs plot intensity verses velocity at three distinct positions across the galaxy. The graphs show how fast CO gas is moving at the three locations. Taken together, the graphs indicate where the gas moving in M82.

Channel Maps

Channel maps show the distribution of gas moving at one particular velocity. The brighter regions indicate where greater amounts of CO gas are concentrated within M82.

Channel Map Movie

Other representations of image data can be viewed as a combination of channel maps. This movie presents a series of channel maps in rapid succession. The animation helps astronomers discern the different velocities at which the distinct parts of the object are moving.

Velocity-Space Diagrams

This velocity-space diagram shows the velocity of CO gas that is distributed along a line, as if crossing from left to right across M82. Towards the center of M82, a ring of material is becomes discernible. This ring is disguised in both spectral line graphs and channel maps.

Average Image

Average images are produced by averaging all the channel maps together. These representations show the general distribution of a gas within an object. Here the extent of CO gas within M82 is revealed.

Data Cubes

Data cubes are compiled from a collection of two-dimensional channel maps arranged one behind the other, according to their velocity. Astronomers can view the resulting data cubes at various angles by rotating them in an animation. In doing so, researchers can better grasp of the distribution of material as well as its motions in different directions.