NRAO: National Radio Astronomy Observatory

About this Image

Since 2002 hundreds of HI (neutral hydrogen) clouds have been discovered with the help of the new unique NRAO instrument -- 100 m Green Bank Telescope (GBT). These clouds are a completely new class of objects presenting a previously unknown phenomenon of the interstellar matter physics. Several brightest of them have been observed with another NRAO instrument, Very Large Array (VLA) which provides better angular resolution. This collage shows one of such clouds (G19.4+6.3) as seen at its peak by the GBT in the larger Galactic halo context and its VLA HI column density map with two VLA sample spectra taken at the cloud's cores. The GBT image shows that the cloud is a part of a larger cloud-filament structure, while the VLA image reveals that the cloud has a "dense core - diffuse envelope" structure. The assymetry of the envelope might also suggest a sideway motion. It can be estimated that this cloud is about 8 kpc away from us and 900 pc above the Galactic plane. Its size is approximately 30 pc with core size of about 10 pc. This cloud contains 800 solar masses of hydrogen and the desity of its cores exceeds 20 atoms per cubic cm. The images are false-color with blue corresponding to the least and red -- to the most hydrogen density.

Investigator(s):  Liszt, H., Lockman, J., Rupen, M. (NRAO), Pidopryhora Y. (NRAO & Ohio U)

Alternate Resolutions

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This image is available in the following downloadable versions:

• 750 x 373 color JPEG
• 1200 x 597 color JPEG
• 3000 x 1492 color TIFF

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

For More Information

• Up one level for more info on Galactic_Halo
• For unfamiliar terms, visit the NRAO Radio Astronomy Glossary

Technical Data

Telescope	VLA
Date of Observation	2004-07-03
Type of Observation	Spectral Line Observations
Center of Image	RA: 18:04:0.00, Dec: -8:58:0.00 (J2000)
Field of View	2.0000 x 6.0000 degrees
Technical Caption	The resolutions: GBT image -- 9 arcmin, VLA (taken in D-array) -- 1 arcmin. GBT exposure 5 sec per 3 by 3 arcmin pixel, VLA -- a few hours. Cloud's peak column density is 4x10^+20 cm^-2 and the line's FWHM is 4.4 km/s, as measured from the VLA data.



Astronomical database entries for HI cloud G19.4 6.3
• Query SIMBAD for more HI cloud G19.4 6.3 data

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