NGC 4522  BVR 

Broadband color image of the Virgo Cluster spiral 
galaxy NGC4522. Most of the light in this picture 
arises from stars. The dark lanes are due to dust 
which blocks some of the starlight. This highly 
inclined galaxy has a relatively normal 
distribution of old stars, but bright, blue 
newly-formed star clusters can be seen embedded 
within gas filaments which emerge from the disk 
plane toward the NW. 
Image from WIYN 3.5-meter telescope.

  

 NGC 4522 H-alpha  

H-alpha image of the Virgo 
Cluster spiral galaxy 
NGC4522. H-alpha emission
arises from hot ionized gas
surrounding recently formed
massive stars. This image
is to the same scale as the
broadband image to the left.
Image from WIYN 3.5-meter 
telescope.

  

        NGC 4522   H-alpha and R 

H-alpha and broadband (R band) optical maps of the Virgo Cluster 
spiral galaxy NGC4522. The galaxy has been rotated for this figure. 
(a) The top panel shows grayscale and contour maps of H-alpha 
emission. Note that there is no H-alpha emission, and therefore 
no ionized gas and no star formation, in the outer disk.
(b) The middle panel shows grayscale and contour maps of R-band 
emission. The distribution of starlight appears normal for an 
inclined spiral disk galaxy.
(c) The bottom panel shows an overlay of the H-alpha map (grayscale) 
on the R-band map (contours). Note that the distributions of stars 
and gas are very different! There is no gas in the outer disk, but 
there are gas filaments emerging from the plane of the disk. This is 
gas in the process of leaving the galaxy, as it is stripped by the 
ram pressure force exerted by gas in the intracluster medium.
Images from WIYN 3.5-meter telescope.