Unveiling the origin of the bulge of M81 with spectroscopicobservations and the TNG50 simulation

GARGIULO, IGNACIO D.; CASO, JUAN P.; ESCUDERO, CARLOS G.; SESTO, LEANDRO A.; MONACHESI, ANTONELLA; GOMEZ, FACUNDO A.

Córdoba

Congreso; 63a Reunión anual de la Asociación Argentina de Astronomía; 2021

Observatorio Astronómico de Córdoba (OAC, UNC) y el Instituto de Astronomía Teórica y Experimental (IATE, CONICET-UNC).

We present the main remarks of an ongoing study about the origin of the bulge of the nearby spiralgalaxy 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 literatureas a classical bulge. This type of bulge is commonly linked to a merger origin. However, the quiet merger historyrevealed by the stellar halo of M81 puts strong constraints on this scenario. We placed four long-slits to coverthe central region of M81 with such a disposition that will allow us to study radial profiles of ages, chemicalabundances and the moments of the line-of-sight velocity distribution (e.g., mean velocity, velocity dispersion)at different galactic latitudes. We define M81 analogues in the simulation by means of a bulge mass - accretedstellar halo mass relation and find three simulated galaxies that lie close to M81 in such diagram. The threeM81 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