by Megan Johnson (CASS)

We present a detailed study of the dwarf irregular galaxy ESO 324-G024 – colored green and seen in projection against the northern lobe of the radio galaxy Centaurus A (Cen A, NGC 5128). ESO 324-G024 lies only ~104 kpc from the center of NGC 5128, which is a giant elliptical galaxy and host to the radio source known as Cen A. We find that ESO 324-G024 has a peculiar neutral hydrogen (HI) morphology with a tail extending 2.5 kpc beyond its disk. Our data indicates that ESO 324-G024 may have passed through the northern radio lobe of Cen A and experienced ram pressure forces, which are the dominant mechanism for creating its tail.

In this figure we see the giant radio lobes of Cen A – as mapped by HIPASS ( Calabretta et al. 2014 ) – together with the factor 10 enlarged HI intensity maps of the Cen A Group members from the Local Volume HI Survey (LVHIS) . The colors indicate if a group member is in front of , behind or at the same distance as Cen A.

Reference: Johnson, Kamphuis, Koribalski, Wang, Oh, Hill, O’Sullivan, Haan, Serra 2015 ( arXiv:1505.07554 )