NRAO: National Radio Astronomy Observatory

About this Image

A false color representation of the velocity field for the Scd galaxy Messier 33, also known as the "Triangulum Galaxy". The velocities are inferred from observations of the atomic hydrogen gas in the disk of this galaxy. This gas emits light at a very well defined rest frequency, but this frequency becomes "Doppler shifted", depending on whether the gas is moving towards or away from us. In this image, gas which is moving towards us is shown in blue, and gas that is moving away from us is shown in red, with other colors depicting gas at intermediate velocities. The brightness of each pixel reflects how much gas is at each location. The motion of the gas indicates that it is in a thin disk rotating around the center of the galaxy. Astronomers can analyze the rotation of a galaxy to measure its total mass.

Investigator(s):  David Thilker, Robert Braun, and Rene Walterbos

Alternate Resolutions

Help

This image is available in the following downloadable versions:

• 299 x 414 color JPEG
• 742 x 1024 color JPEG

If you would like to obtain a higher resolution version of this image, please contact Pat Smiley.

For More Information

• Read the Press Release
• Read the NRAO Newsletter article
• Up one level for more info on Spiral galaxies
• For unfamiliar terms, visit the NRAO Radio Astronomy Glossary

Technical Data

Telescope	VLA
Date of Observation	1998-08-15
Type of Observation	Spectral Line Observations
Wavelength	21 cm
Frequency	1420.4 MHz
Species	HI
Center of Image	RA: 01:33:51.02, Dec: 30:39:36.70 (J2000)
Field of View	1.0000 x 1.2500 degrees
Technical Caption	The data were obtained from VLA observations taken both in its B-array and CS-array configurations, with a spatial resolution of 10\" and velocity resolution of 1.3 km/s. The VLA data have been supplemented by total power observations obtained at the Westerbork Synthesis Radio Telescope.



Astronomical database entries for M33
• Query NED for images of M33
• Query SIMBAD for more M33 data

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