A parsec-resolution simulation of the Antennae galaxies: formation of star clusters during the merger

Abstract

We present a hydrodynamical simulation of an Antennae-like galaxy merger at parsec resolution, including a multi-component model for stellar feedback and reaching numerical convergence in the global star formation rate for the first time. We analyse the properties of the dense stellar objects formed during the different stages of the interaction. Each galactic encounter triggers a starburst activity, but the varying physical conditions change the triggering mechanism of each starburst. During the first two pericenter passages, the starburst is spatially extended and forms many star clusters. However, the starburst associated to the third, final passage is more centrally concentrated: stars form almost exclusively in the galactic nucleus and no new star cluster is formed. The maximum mass of stars clusters in this merger is more than 30 times higher than those in a simulation of an isolated Milky Way-like galaxy. Antennae-like mergers are therefore a formation channel of young massive clusters possibly leading to globular clusters. Monitoring the evolution of a few clusters reveals the diversity of formation scenarios including the gathering and merger of gas clumps, the monolithic formation and the hierarchical formation in sub-structures inside a single cloud. Two stellar objects formed in the simulation yield the same properties as ultra-compact dwarf galaxies. They share the same formation scenario than the most massive clusters, but have a larger radius either since birth, or get it after a violent interaction with the galactic center. The diversity of environments across space and time in a galaxy merger can account for the diversity of the stellar objects formed, both in terms of mass and size.

CALIFA spectroscopy of the interacting galaxy NGC 5394 (Arp 84): starbursts, enhanced [N ii]6584 and signs of outflows and shocks

“…The total mass of intermediate age stars is estimated as 1.200×10 9 M with only 170 million M at r < 4 arcsec. These patterns recall the merger simulation of Renaud, Bournaud & Duc (2015), in which early star-formation is extensive but the final burst is 'almost exclusively central, due to gas inflows'. The concentration of star-formation in the SW disk (the inner western arm, see K02), reflects the lopsided distribution of H2 which would be a short-term effect of the interaction, so is seen in the young population map but not for the intermediate-age stars, which instead are concentrated in the other two disk arms (eastern and outer-western).…”

Shutting down or powering up a (U)LIRG? Merger components in distinctly different evolutionary states in IRAS 19115−2124 (the Bird)

“…This distribution of star formation here is in agreement with triggering of formation of massive clusters by compression of gas (e.g. Renaud et al 2015). The S/N of the present data is not sufficient, however, to study the spectra of these features independently.…”

Star formation triggered by galaxy interactions in modified gravity

“…Any other physical aspect is treated as in Renaud et al (2015a). In short, the galaxy systems (isolated or in pairs) are modelled without accretion of external gas nor DM.…”

“…• Using the orbit of Renaud et al (2015a) designed to reproduce the morphology and kinematics of the Antennae galaxies "N" stands for Newton and "M" for MOND. "A" indicates the orbit of the Antennae model of Renaud et al (2015a), and "S" represents lower initial velocities ("Slow").…”

“…"A" indicates the orbit of the Antennae model of Renaud et al (2015a), and "S" represents lower initial velocities ("Slow").…”