LSB Galaxies and the Tully-Fisher Relation
Authors: Aeree Chung, J. H. van Gorkom, K. O'Neil, G. D. Bothun
Published:The Astronomical Journal (2002), accepted.
ABSTRACT:
We present VLA HI imaging of four LSB galaxies which were thought to strongly
deviate from the TF relation based on Arecibo single-dish observations. We do not
detect three of the four targeted LSB galaxies in HI down to a 4-sigma limit of
0.08Jy km/s. We find that two of the four of these LSBs have bright galaxies which
have contaminated the Arecibo signal. A further examination of the Arecibo sample
shows that five out of the six galaxies that were found to deviate from TF have
nearby bright galaxies and we conclude that possibly all but one of the non-TF
galaxies are contaminated by HI from nearby galaxies. The sixth galaxy was not
detected by us. A new observation by Arecibo did not confirm the earlier detection.
The integrated profiles of the bright galaxies are consistent with the Arecibo results
both in velocity range and amplitude, which indicates that most of the extreme
deviators from the TF relation must have been affected by bright companions in
this earlier HI survey. A more recent determination of the sidelobe structure of the
Arecibo beam supports our conclusion and shows that the degree of sidelobe
contamination was much larger than could have been initially predicted. Hence, we
have corrected the results found in O'Neil et al. (2000) and have reconstructed the
TF relation. These new observations then show a) a reconstructed TF relation that
has relatively large scatter at all values of rotational velocity (possibly indicating the
true range in disk galaxy properties) and b) the presence of at least some red, gas
poor, LSB disks that indeed may be in an advanced evolutionary state as the faded
remnants of their former high surface brightness actively star forming state.
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