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1. Galaxy Zoo: Morphological Classification of Galaxy Images from the Illustris Simulation

   https://doi.org/10.3847/1538-4357/aaa250  

   Dickinson, Hugh ; Fortson, Lucy ; Lintott, Chris ; Scarlata, Claudia ; Willett, Kyle ; Bamford, Steven ; Beck, Melanie ; Cardamone, Carolin ; Galloway, Melanie ; Simmons, Brooke ; et al ( February 2018 , The Astrophysical Journal)
2. Massive central galaxies of galaxy groups in the Romulus simulations: an overview of galaxy properties at z  = 0

   https://doi.org/10.1093/mnras/stac1622  

   Jung, S. Lyla ; Rennehan, Douglas ; Saeedzadeh, Vida ; Babul, Arif ; Tremmel, Michael ; Quinn, Thomas R. ; Loubser, S. Ilani ; O’Sullivan, E. ; Yi, Sukyoung K. ( June 2022 , Monthly Notices of the Royal Astronomical Society)

   Contrary to many stereotypes about massive galaxies, observed brightest group galaxies (BGGs) are diverse in their star formation rates, kinematic properties, and morphologies. Studying how they evolve into and express such diverse characteristics is an important piece of the galaxy formation puzzle. We use a high-resolution cosmological suite of simulations Romulus and compare simulated central galaxies in group-scale haloes at z = 0 to observed BGGs. The comparison encompasses the stellar mass–halo mass relation, various kinematic properties and scaling relations, morphologies, and the star formation rates. Generally, we find that Romulus reproduces the full spectrum of diversity in the properties of the BGGs very well, albeit with a tendency toward lower than the observed fraction of quenched BGGs. We find both early-type S0 and elliptical galaxies as well as late-type disc galaxies; we find Romulus galaxies that are fast-rotators as well as slow-rotators; and we observe galaxies transforming from late-type to early-type following strong dynamical interactions with satellites. We also carry out case studies of selected Romulus galaxies to explore the link between their properties, and the recent evolution of the stellar system as well as the surrounding intragroup/circumgalactic medium. In general, mergers/strong interactions quench star-forming activity and disrupt themore »stellar disc structure. Sometimes, however, such interactions can also trigger star formation and galaxy rejuvenation. Black hole feedback can also lead to a decline of the star formation rate but by itself, it does not typically lead to complete quenching of the star formation activity in the BGGs.

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3. Constraints on S 8 from a full-scale and full-shape analysis of redshift-space clustering and galaxy–galaxy lensing in BOSS

   https://doi.org/10.1093/mnras/stad473  

   Lange, Johannes U. ; Hearin, Andrew P. ; Leauthaud, Alexie ; van den Bosch, Frank C. ; Xhakaj, Enia ; Guo, Hong ; Wechsler, Risa H. ; DeRose, Joseph ( February 2023 , Monthly Notices of the Royal Astronomical Society)

   We present a novel simulation-based cosmological analysis of galaxy–galaxy lensing and galaxy redshift-space clustering. Compared to analysis methods based on perturbation theory, our simulation-based approach allows us to probe a much wider range of scales, $0.4 \, h^{-1} \, \mathrm{Mpc}$ to $63 \, h^{-1} \, \mathrm{Mpc}$, including highly non-linear scales, and marginalizes over astrophysical effects such as assembly bias. We apply this framework to data from the Baryon Oscillation Spectroscopic Survey LOWZ sample cross-correlated with state-of-the-art gravitational lensing catalogues from the Kilo Degree Survey and the Dark Energy Survey. We show that gravitational lensing and redshift-space clustering when analysed over a large range of scales place tight constraints on the growth-of-structure parameter $S_8 = \sigma _8 \sqrt{\Omega _{\rm m} / 0.3}$. Overall, we infer S8 = 0.792 ± 0.022 when analysing the combination of galaxy–galaxy lensing and projected galaxy clustering and S8 = 0.771 ± 0.027 for galaxy redshift-space clustering. These findings highlight the potential constraining power of full-scale studies over studies analysing only large scales and also showcase the benefits of analysing multiple large-scale structure surveys jointly. Our inferred values for S8 fall below the value inferred from the CMB, S8 = 0.834 ± 0.016. While this difference is not statistically significant by itself, our results mirrormore »other findings in the literature whereby low-redshift large-scale structure probes infer lower values for S8 than the CMB, the so-called S8-tension.

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4. Hubble Space Telescope Wide Field Camera 3 Identifies an r _p = 1 Kpc Dual Active Galactic Nucleus in the Minor Galaxy Merger SDSS J0924+0510 at z = 0.1495

   https://doi.org/10.3847/1538-4357/aac9cb  

   Liu, Xin ; Guo, Hengxiao ; Shen, Yue ; Greene, Jenny E. ; Strauss, Michael A. ( July 2018 , The Astrophysical Journal)
5. The XXL Survey. XLII. The LX − σ v relation of galaxy groups and clusters detected in the XXL and GAMA surveys

   https://doi.org/10.1093/mnras/stab3626  

   Giles, P. A. ; Robotham, A. ; Ramos-Ceja, M. E. ; Maughan, B. J. ; Sereno, M. ; McGee, S. ; Phillipps, S. ; Iovino, A. ; Turner, D. J. ; Adami, C. ; et al ( February 2022 , Monthly Notices of the Royal Astronomical Society)

   The XXL Survey is the largest homogeneous survey carried out with XMM-Newton. Covering an area of 50 deg2, the survey contains several hundred galaxy clusters out to a redshift of ≈2, above an X-ray flux limit of ∼6 × 10−15 er g cm−2 s−1. The GAMA spectroscopic survey of ∼300 000 galaxies covers ≈286 deg2, down to an r-band magnitude of r < 19.8 mag. The region of overlap of these two surveys (covering 14.6 deg2) represents an ideal opportunity to study clusters selected via two independent selection criteria. Generating two independently selected samples of clusters, one drawn from XXL (spanning a redshift range 0.05 ≤ z ≤ 0.3) and another from GAMA (0.05 ≤ z ≤ 0.2), both spanning 0.2 ≲ M500 ≲ 5 × 1014 M⊙, we investigate the relationship between X-ray luminosity and velocity dispersion (LX − σv relation). Comparing the LX − σv relation between the X-ray selected and optically selected samples, when not accounting for the X-ray selection, we find that the scatter of the X-ray selected sample is 2.7 times higher than the optically selected sample (at the 3.7σ level). Accounting for the X-ray selection to model the LX − σv relation, we find that the difference in the scatter increases (with the X-ray selectedmore »sample having a scatter 3.4 times larger than the optically selected sample). Although the scatter of the optically selected sample is lower, we find 13 optically selected GAMA groups undetected in X-rays. Inspection of the difference in magnitude between the first and second brightest galaxies in the cluster, and a stacked X-ray image of these 13 groups, suggests that these are young systems still in the process of forming.

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