Comments on "Modeling Galaxy Halos Using Dark Matter with Pressure"

TL;DR

This paper critiques a previous study on galaxy halo modeling with dark matter pressure, identifying calculation errors that affected light deflection estimates, but suggests observational features remain testable.

Contribution

It highlights a calculational mistake in the prior work and clarifies the corrected behavior of light deflection in dark matter halos with pressure.

Findings

Incorrect deflection angle estimates for certain w_r ranges

Solution for w_r>0 should not exist

Deflection angle characteristics remain observationally testable

Abstract

We comment on the calculational mistake in the paper "Modeling galaxy halos using dark matter with pressure" by Somnath Bharadwaj and Sayan Kar. The authors made a mistake while calculating the metric, which led to an overestimate of the deflection angle of light passing through the halos for -1<w_r<-0.5 and an underestimate of the deflection angle for -0.5<w_r<0. In addition, solution for w_r>0 should not exist. Although the Bharadwaj-Kar solution should be corrected, it appears that the characteristics of the deflection angle under the supposed non-conventional non-ideal fluid equation of state for the dark matter halo remain sensitive to the impact parameter and may be verifiable through observations.