Семинар 275 – 23 сентября 2024 г.


Ольга Сильченко

Презентация

2409.13014 Merging Galaxies in Isolated Environments II. Evolution of Star Formation and Accretion Activity during the Merging Process

Paula Calderón-Castillo, Rory Smith

Published 2024-09-19, A&A accepted. 16 pages, 13+5 figures

It is now well known that certain massive galaxies undergo enormousenhancements in their SFR when they undergo major mergers(100x). To analyse theSF enhancement and AGN fraction evolution during the merger process, we use amore timeline-like merger sequence. Also, to determine the relation between theSF enhancement in mergers and the morphology of the galaxies involved. Takingadvantage of the Mstr and SFR of 600 nearby isolated mergers from our previousstudy, we calculate the distance of our galaxies from the SF MS, which we referto as SFmode. We analyse how the SFmode varies during the merger process, formorphology and Mstr. We also analyse the AGN content of our mergers, usingmultiple diagnostics based on emission line ratios and WISE colours. We observethat, overall, merging galaxies show a SFmode that is governed by theirmorphology. Spirals typically show high SFmode values while highly-disturbedgalaxies are generally even more enhanced (0.8dex and 1dex above the MS, resp).On the contrary, elliptical and lenticular galaxies show the lowest SF modes,as expected. However, even they show SF enhancement compared to theirunperturbed counterparts (their median SFmode is within the 1-sigma scatter ofthe MS, and this can occur even before the galaxies have coalesced). We see atrend for SFmode to gradually increase with increasing merger stage. We do notfind a clear dependency of the observed AGN fraction on merger stage for themajority of our classification methods. We find mergers can significantlyenhance SF in galaxies of all morphologies. For early-type galaxies, this couldsuggest that some gas was present prior to the merger which may be triggered toform stars by the tidal interaction. As the SF enhancement continues throughoutthe merger process, this suggests that the enhancement may be a long-livedevent, contrary to the short starbursts seen in some models.