HUBBLE-SPACE-TELESCOPE WIDE-FIELD PLANETARY CAMERA 2 IMAGING OF UGC-12695 - A REMARKABLY UNEVOLVED GALAXY AT LOW-REDSHIFT

Utilizing the F814W and F300W filters, short-exposure Hubble Space Tel escope Wide Field Planetary Camera 2 images were taken of UGC 12695, a nearby (z similar to 0.021) low surface brightness disk galaxy. UGC 1 2695 has an unusual morphology,consisting of a Y-shaped nucleus surrou nded by a faint spiral arm with a number of bright H II regions inters persed throughout the galaxy. Surface photometry indicates that the ma jority of recent star formation in this galaxy occurred in these very localized regions, most of which have a radius of less than or similar to 2 ''. This uneven stellar distribution, combined with the galaxy's overall extremely blue color and low metallicity, indicates that UGC 12695 is an unevolved galaxy. Some of the structural peculiarities of this galaxy arise because a number of background galaxies, previously thought to be morphological components of this galaxy, are showing thr ough both the outer nucleus and spiral arms of UGC 12695. Surface phot ometry of these galaxies shows them to be fairly small (alpha < 1.'' 8 ) disk galaxies with total magnitudes ranging from 19.6 through 24.2 m ag and central surface brightnesses in the range 20.2 mag arcsec(-2) l ess than or equal to mu(0) less than or equal to 23.1 mag arcsec(-2). When possible, the U, B, V, and I colors of these galaxies were measur ed using ground-based images, which show the galaxies to be fairly red , indicating that they are likely at redshifts z 2 0.5. Inclusion of t hem in the photometry of UGC 12695 makes the galaxy appear significant ly redder. When these galaxies are masked out, the resultant U-I color of UGC 12695 is -0.2 +/- 0.1, making it perhaps the bluest galaxy eve r measured in this color system and confirming its nature as a very un evolved galaxy at low redshift. Spectroscopy of these background galax ies, through the transparent disk of UGC 12695, may help to clarify it s chemical evolution and current heavy-element content.