Unveiling the origin of the bulge of M81 with spectroscopic observations and the TNG50 simulation

GARGIULO, IGNACIO; CASO, JUAN PABLO; ESCUDERO, CARLOS; SESTO, LEANDRO; MONACHESI, ANTONELLA; GÓMEZ, FACUNDO

Seúl

Workshop; Gemini Observatory Science Meeting 2022; 2022

Gemini Observatory

We present preliminary results of a study about the origin of the bulge of the nearby spiral galaxy M81 combining spectral data, obtained using Gemini/GMOS-N observations, and the cosmological hydro-dynamical simulation TNG50-1 of the IllustrisTNG collaboration. The bulge of M81 is classified in the literature as a classical bulge. This type of bulge is commonly linked to a merger origin. However, the quiet merger history revealed by the stellar halo of M81 puts strong constraints on this scenario. We placed four long-slits to cover the central region of M81 with such a disposition that will allow us to study radial profiles of ages, chemical abundances and the moments of the line-of-sight velocity distribution (e.g., mean velocity, velocity dispersion, h3, h4) at different galactic latitudes. We define M81 analogues in the simulation by means of a bulge mass - accreted stellar halo mass relation and find three simulated galaxies that lie close to M81 in such diagram. The three M81 analogues show low to negligible fractions of accreted stellar particles in their kinematically selected bulge, implying that mergers may not be the main mechanism for the build-up of M81’s classical bulge.