Atomic Gas in 'The Mice'

Image
Minimum credit line: Image courtesy of NRAO/AUI and J. Hibbard & J. van Gorkom(for details, see Image Use Policy).

About this Image

A composite image of the optical light (green), warm gas (pinkish white), and cold atomic hydrogen gas (blue) in the well known interacting pair of galaxies known as "The Mice", or NGC 4676. The nickname of this object derives from its optical appearance, specifically the narrow tails emering from oval shaped bodies, reminiscent of two mice . This system is the result of two spiral galaxies which are falling together. As computer simulations demonstrate, the tidal tails are thrown out after the galaxies pass each other once and are pulled together by their mutual gravitational attraction. The tails emerge from the far side of the disks, which is pulled less than the other parts of the galaxy. The tails are, in effect, the material that gets "left behind" as the galaxies fall back together.

The atomic hydrogen observations, taken with the VLA in its C- and D-array configurations, show the tidal tails to be rich in cold gas, confirming the gas-rich nature of the progenitor disks. The warm gas, as mapped in the Halpha line emission, is likely heated by the young massive stars in star forming regions. There are numerous such regions distributed all along the tails, which may seed the formation of small stellar systems, and possibly even distinct dwarf galaxies.

Investigator(s):  J. Hibbard & J. van Gorkom

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Technical Data

    Telescope VLA 
    Date of Observation 1991-05-13 
    Type of Observation Spectral Line Observations 
    Wavelength 21 cm 
    Frequency 1420.4 MHz 
    Species HI 
    Center of Image RA: 12:46:10.76, Dec: 30:43:36.00 (J2000)  
    Field of View 0.0500 x 0.0833 degrees  
    Technical Caption VLA C+D array observations with a resolution of 30". Optical image is an B-band image, and both this image and the continuum subtracted Halpha image were obtained with the KPNO 2.1m telescope.  

  • Astronomical database entries for NGC4676
    • Query NED for images of NGC4676
    • Query SIMBAD for more NGC4676 data

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