One of the challenges related to stellar bars is to determine accurately the
length of the bar in a disc galaxy. In past literature, a wide variety of
methods has been employed to measure the extent of a bar. However, a systematic
study on determining the robustness and accuracy of different bar length
estimators is still beyond our grasp. Here, we investigate the accuracy and the
correlation (if any) between different bar length measurement methods while
using an N-body model of a barred galaxy where the bar evolves
self-consistently in presence of a live dark matter halo. We investigate the
temporal evolution of the bar length, using different estimators (involving
isophotal analysis of de-projected surface brightness distribution and Fourier
decomposition of surface density), and study their robustness and accuracy.
Further attempts have been made towards determining correlation between any two
of these bar length estimators used here. In presence of spirals, the bar
length estimators which only consider the amplitudes of different Fourier
moments (and do not take into account the phase-angle of m=2 Fourier moment),
systematically overestimate the length of the bar. The strength dark-gaps
(produced by bars) correlates strongly with the bar length in early rapid
growth phase, and is only weakly anti-correlated during subsequent quiescent
phase of bar evolution. However, the location of dark-gaps correlates only
weakly with the bar length, hence can not be used as a robust proxy for
determining the bar length. In addition, the bar length estimators, obtained
using isophotal analysis of de-projected surface brightness distribution,
systematically overestimate the bar length. The implications of bar length
over(under)estimation in the context of determining fast/slow bars are further
discussed.Comment: 12 pages, 10 figures (including appendix), comments are welcome