Scaling Relations in Dissipationless Spiral-like Galaxy Mergers

TL;DR

This study investigates the scaling relations of galaxy remnants resulting from dissipationless spiral galaxy mergers, finding that these relations are largely consistent with observations and suggesting dissipationless processes play a significant role.

Contribution

It provides new insights into how dissipationless mergers influence galaxy scaling relations, challenging previous assumptions about the necessity of dissipative processes.

Findings

Remnants exhibit scaling indices similar to observed ellipticals.

The Fundamental Plane and luminosity-phase space relations are consistent with observations.

Results suggest dissipationless processes significantly shape galaxy scaling relations.

Abstract

We determine both representations of the Fundamental Plane [Re Sig^a Ie^b and Re (Sig^2/Ie)^lambda] and the luminosity-effective phase space density [L fe^(-gamma)] scaling relation for N-body remnants of binary mergers of spiral-like galaxies. The main set of merger simulations involves a mass-ratio of the progenitors in the range of about 1:1 to 1:5, harboring or not a bulge-like component, and are constructed using a cosmological motivated model. Equal-mass mergers are also considered. Remnants lead to average values for the scaling indices of <a>~1.6, <b>~0.6, <lambda>~0.7, and <gamma>~0.65. These values are consistent with those of K--band observations (Mobasher et al. 1999) of ellipticals: <a>~1.5, <b>~0.8, <lambda>~0.7, and <gamma>~0.60. The b index is, however, not well reproduced. This study does not allow us to establish a conclusive preference for models with or without a bulge as progenitors. Our results indicate that the L--fe and FP scalings might be determined to a large extent by dissipationless processes, a result that appears to be in contradiction to other dissipationless results.