We derive the recent growth history of the Fornax Cluster, in particular the recent infall of the giant elliptical galaxy NGC 1404. We show, using a simple cluster minor merger simulation tailored to Fornax and NGC 1404, that a second or more likely third encounter between the two reproduces all the main merger features observed in both objects; we firmly exclude a first infall scenario. Our simulations reveal a consistent picture: NGC 1404 passed by NGC 1399 about 1.1-1.3 Gyr ago from the northeast to the southwest and is now almost at the point of its next encounter from the south. This scenario explains the sloshing patterns observed in Fornax - a prominent northern cold front and an inner southern cold front. This scenario also explains the truncated atmosphere, the gas-stripping radius of NGC 1404, and its faint gas tail. Independent of the exact history, we can make a number of predictions. A detached bow shock south of NGC 1404 should exist, which is a remnant of the galaxy's previous infall at a distance from NGC 1404 between 450 and 750 kpc with an estimated Mach number between 1.3 and 1.5. The wake of NGC 1404 also lies south of the galaxy with enhanced turbulence and a slight enhancement in metallicity compared to the undisturbed regions of the cluster. Southwest of NGC 1404, there is likely evidence of old turbulence originating from the previous infall. No scenario predicts enhanced turbulence outside of the cold front northwest of the cluster center.
|State||Published - Oct 1 2018|
Bibliographical noteFunding Information:
ER acknowledges the support of STFC, through the University of Hull’s Consolidated Grant ST/R000840/1 and access to viper, the University of Hull High Performance Computing Facility. Software:FLASH (Fryxell et al. 2000).
© 2018. The American Astronomical Society. All rights reserved.
- galaxies: clusters: individual (Fornax)
- galaxies: clusters: intracluster medium
- galaxies: individual (NGC 1404)
- hydrodynamics - methods: numerical
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science