Surveyed Pegasus and Cancer clusters, fields around known galaxies in the Great Wall


( Table)

• Images inspected for obvious flaws

• Images bias subtracted and flat fielded using IMARITH

• Multiple images were shifted and registered, then median averaged using IMCOMBINE

• Zeropoints for each field were found using kown galaxies and stars within the field

• Resultant images checked by eye for registration errors > 0.66"

• Peak intensity or physical center was found for each galaxy

• Annular intensities found around the center using GASP

• Surface brightness profiles then plotted

• Galaxies with U-B < -0.2, B-V < 0.6, V-I < 1.0

• Very blue LSB galaxies have been noted often in the past

• Show LSB galaxies aren't just the faded remnants of HSB galaxies

• Could be partially due to low metallicity, but colors are often bluer than the most very metal poor globular clusters

• Probably due to a young mean age

• When redshifted into the blue/visual filter these could be the local counterparts to the very blue high redshift galaxies recently found

• LSB galaxies with U-B > 0.4 and B-V > 0.9 never before seen

• Lack of red LSB galaxies has been a concern, since it appeared no faded LSB galaxies exist at present

• Colors similar to the colors of some of the oldest galaxies

• Colors match a galaxy which underwent a massive burst of star formation for 20 Gyrs ago and has been quiescent ever since

• Significant groups has old B-V and V-I colors and young U-B colors

• Probably old galaxies undergoing a small, but significant burst of star formation

• have a HI surface density at or below the threshold for normal star formation
  (McGaugh & Bothun 1994)

• are deficient in molecular material (Schombert, etal 1990)

• are, on average, more isolated then their HSB counterparts (Bothun, et al 1990)

• evolve with a low time-averaged star formation rate due to lack of external triggers

• HSB tidal encounters typically result in a central inflow of gas and often the formation of a central bar

• LSB galaxies are stable against the growth of bar formation and large scale central inflow of gas during tidal encounters ( Mihos, etal 1997)

• LSB galaxies are not necessarily stable against local instabilities

• Varied all possible galaxy parameters:
  
  color
  µ(0)
  scale length
  M/L
  Mgas/MT
  burst concentration
  burst percentage
  radius of burst

• Allowed up to 75% of the galaxies' HI mass to undergo starburst

• Found

  • It was possible to significantly change the galaxy's total color

    (U-B) = -0.1
    (B-V) = -0.1,
    (V-I) = -0.04

  • Virtually impossible to alter the central surface brightness!

Made and analysed a Monte-Carlo simulation of the night sky

• Two different underlying galaxy distributions - Flat and Gaussian

• Sky background = 21.76 +\- 0.04 mag arcsec

• Sky resolution was 1.0 "/pixel, images were 800x800 pixels

• 17 +\- 1 galaxies/frame, with =6.5+\-4", i=50 +\- 10

• Galaxies had exponential profile (half had bright central core)

No significant difference is evident between either observed distribution and the Texas data

Therefore no information can be gained from a CCD survey more then 2.5 mag arcsec fainter than the sky brightness.

• Galaxies have been found with µ(0) > 24.0 mag arcsec

• Each time a survey probe goes deeper fainter galaxies are found