Low Surface Brightness Galaxies and the Tully-Fisher Relation

We present VLA HI imaging of four LSB galaxies which were thought to stronglydeviate from the TF relation based on Arecibo single-dish observations. We donot detect three of the four targeted LSB galaxies in HI down to a 4-sigmalimit of 0.08Jy km/s. We find that two of the four of these LSBs have brightgalaxies which have contaminated the Arecibo signal. A further examination ofthe Arecibo sample shows that five out of the six galaxies that were found todeviate from TF have nearby bright galaxies and we conclude that possibly allbut one of the non-TF galaxies are contaminated by HI from nearby galaxies. Thesixth galaxy was not detected by us. A new observation by Arecibo did notconfirm the earlier detection. The integrated profiles of the bright galaxiesare consistent with the Arecibo results both in velocity range and amplitude,which indicates that most of the extreme deviators from the TF relation musthave been affected by bright companions in this earlier HI survey. A morerecent determination of the sidelobe structure of the Arecibo beam supports ourconclusion and shows that the degree of sidelobe contamination was much largerthan could have been initially predicted. Hence, we have corrected the resultsfound in O'Neil et al. (2000) and have reconstructed the TF relation. These newobservations then show a) a reconstructed TF relation that has relatively largescatter at all values of rotational velocity (possibly indicating the truerange in disk galaxy properties) and b) the presence of at least some red, gaspoor, LSB disks that indeed may be in an advanced evolutionary state as thefaded remnants of their former high surface brightness actively star formingstate.