Star formation concentration as a tracer of environmental quenching in action: a study of the <scp>eagle</scp> and <scp>c-eagle</scp> 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
• Other Authors: Australian Research Council, NWO, China Scholarship Council, CSC, STFC, BIS
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2023
• Subjects: Space and Planetary Science; Astronomy and Astrophysics; sami
• Online Access: http://dx.doi.org/10.1093/mnras/stad1864; https://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/stad1864/50683720/stad1864.pdf; https://academic.oup.com/mnras/article-pdf/523/4/6020/50768223/stad1864.pdf

ABSTRACT 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 ($10^{12}\, {\rm M}_{\odot }$ ≲ M200 &lt; $3 \times 10^{15}\, {\rm M}_{\odot }$). A star-formation concentration index [C-index = log10(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 tquench 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 &gt; 2 Gyr). The simulated galaxies at higher redshift (z = 0.7 ∼ 2) experience faster quenching (median tquench &lt; 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.