Star formation concentration as a tracer of environmental quenching in action:a study of the EAGLE and C-EAGLE simulations

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Wang, Di, Lagos, Claudia D. P., Croom, Scott M., Wright, Ruby J., Bahé, Yannick M, Bryant, Julia J., van de Sande, Jesse, Vaughan, Sam P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: galaxies: clusters: general; galaxies: evolution; galaxies: groups: general; galaxies: star formation; methods: numerical; sami
• Online Access: https://researchers.mq.edu.au/en/publications/cc3ae83f-6e44-42d8-8546-7f92a66c2952; https://doi.org/10.1093/mnras/stad1864; https://research-management.mq.edu.au/ws/files/298379877/285048469.pdf; http://www.scopus.com/inward/record.url?scp=85165203566&partnerID=8YFLogxK

We study environmental quenching in the eagle/c-eagle cosmological hydrodynamic simulations over the last 11 Gyr (i.e. z = 0-2). The simulations are compared with observations from the SAMI Galaxy Survey at z = 0. We focus on satellite galaxies in galaxy groups and clusters (10 12 M ⊙ ≲ M 200 < 3 x 10 15 M ⊙ ). A star-formation concentration index [C-index = log 10(r50, SFR/r50, rband) ] is defined, which measures how concentrated star formation is relative to the stellar distribution. Both eagle/c-eagle and SAMI show a higher fraction of galaxies with low C-index in denser environments at z = 0-0.5. Low C-index galaxies are found below the SFR-M ⋆ main sequence (MS), and display a declining specific star formation rate (sSFR) with increasing radii, consistent with 'outside-in' environmental quenching. Additionally, we show that C-index can be used as a proxy for how long galaxies have been satellites. These trends become weaker at increasing redshift and are absent by z = 1-2. We define a quenching time-scale t quench as how long it takes satellites to transition from the MS to the quenched population. We find that simulated galaxies experiencing 'outside-in' environmental quenching at low redshift (z = 0 ∼0.5) have a long quenching time-scale (median tquench > 2 Gyr). The simulated galaxies at higher redshift (z = 0.7 ∼2) experience faster quenching (median t quench < 2 Gyr). At z ≳ 1-2 galaxies undergoing environmental quenching have decreased sSFR across the entire galaxy with no 'outside-in' quenching signatures and a narrow range of C-index, showing that on average environmental quenching acts differently than at z ≲ 1.