The GOGREEN survey: dependence of galaxy properties on halo mass at z > 1 and implications for environmental quenching

Abstract

We use photometric redshifts and statistical background subtraction to measure stellar mass functions in galaxy group-mass (4.5 − 8 × 1013 M⊙) haloes at 1 < z < 1.5. Groups are selected from COSMOS and SXDF, based on X-ray imaging and sparse spectroscopy. Stellar mass (Mstellar) functions are computed for quiescent and star-forming galaxies separately, based on their rest-frame UVJ colours. From these we compute the quiescent fraction and quiescent fraction excess (QFE) relative to the field as a function of Mstellar. QFE increases with Mstellar, similar to more massive clusters at 1 < z < 1.5. This contrasts with the apparent separability of Mstellar and environmental factors on galaxy quiescent fractions at z ∼ 0. We then compare our results with higher mass clusters at 1 < z < 1.5 and lower redshifts. We find a strong QFE dependence on halo mass at fixed Mstellar; well fit by a logarithmic slope of d(QFE)/dlog (Mhalo) ∼ 0.24 ± 0.04 for all Mstellar and redshift bins. This dependence is in remarkably good qualitative agreement with the hydrodynamic simulation BAHAMAS, but contradicts the observed dependence of QFE on Mstellar. We interpret the results using two toy models: one where a time delay until rapid (instantaneous) quenching begins upon accretion to the main progenitor (“no pre-processing”) and one where it starts upon first becoming a satellite (“pre-processing”). Delay times appear to be halo mass dependent, with a significantly stronger dependence required without pre-processing. We conclude that our results support models in which environmental quenching begins in low-mass (<1014M⊙) haloes at z > 1.

A systematic search for galaxy protocluster cores at the transition epoch of their star formation activity

“…This means that environmental quenching depends on stellar mass and is more effective for higher-mass galaxies. At 𝑧 1, environmental quenching is independent of stellar mass (e.g., Peng et al 2010), while stellar-mass dependent environmental quenching has been found at 𝑧 1 (Balogh et al 2014;van der Burg et al 2020;Reeves et al 2021). Our result shows that this trend continues at 𝑧 > 1 at a statistically high significance.…”

“…They have obtained 0.1 QFE 0.2 for galaxies with 10.25 < log(𝑀 * /𝑀 ) < 11. Reeves et al (2021) have found QFE ∼ 0.27 for galaxies with log(𝑀 * /𝑀 ) > 10 in groups at 1 < 𝑧 < 1.5 with 13.65 < log(𝑀 h /𝑀 ) < 13.9 conformed by the X-ray and spectroscopic observations of the GOGREEN survey. The RFE of our study is smaller than these studies: 0.081 ± 0.002 around all centrals for galaxies with log(𝑀 * /𝑀 ) > 10 (see also Table 4).…”

“…In fact, when we calculate the RFE within a smaller radius of 0.3 pMpc, the RFE is found to be 0.121 ± 0.004 around all centrals for galaxies with log(𝑀 * /𝑀 ) > 10, comparable to the QFE of Sarron & Conselice (2021) (see also Table 4). The QFE also has halo mass dependence, with lower QFEs for lower mass haloes (Nantais et al 2016;Reeves et al 2021). As shown in Fig.…”

“…8, our PC core sample contains less massive haloes at least down to log(𝑀 h,min /𝑀 ) ∼ 13.5. This could lead to the lower RFE compared to the QFE of Reeves et al (2021) who mainly use on average a more massive sample (see their Table 1).…”

“…At 1.5 < 𝑧 < 2.5, PC cores dominated by the quiescent population have also been found (Strazzullo et al 2013;Newman et al 2014;Cooke et al 2016;Lee-Brown et al 2017;Willis et al 2020). Below 𝑧 = 1.5, somewhat matured clusters or groups show a high fraction of quenched galaxies compared to the field (e.g., Balogh et al 2016;van der Burg et al 2018van der Burg et al , 2020Reeves et al 2021;Sarron & Conselice 2021).…”