Coincidence between morphology and star formation activity through cosmic time: the impact of the bulge growth

Abstract

The origin of the quenching in galaxies is still highly debated. Different scenarios and processes are proposed. We use multi band (400 − 1600 nm) bulge-disc decompositions of massive galaxies in the redshift range 0 < 𝑧 < 2 to explore the distribution and the evolution of galaxies in the 𝑙𝑜𝑔 𝑆𝐹𝑅 − 𝑙𝑜𝑔 𝑀∗ plane as a function of the stellar mass weighted bulge-to-total ratio (𝐵/𝑇𝑀∗ ) and also for internal galaxy components (bulge/disc) separately. We find evidence of a clear link between the presence of a bulge and the flattening of the Main Sequence in the high-mass end. All bulgeless galaxies (𝐵/𝑇𝑀∗<0.2) lie on the main-sequence, and there is little evidence of a quenching channel without bulge growth. Galaxies with a significant bulge component (𝐵/𝑇𝑀∗>0.2) are equally distributed in number between star forming and passive regions. The vast majority of bulges in the Main Sequence galaxies are quiescent, while star-formation is localized in the disc component. Our current findings underline a strong correlation between the presence of the bulge and the star formation state of the galaxy. A bulge, if present, is often quiescent, independently of the morphology or the star formation activity of the host galaxy. Additionally, if a galaxy is quiescent, with a large probability, is hosting a bulge. Conversely, if the galaxy has a disky shape is highly probable to be star forming.

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