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1. Galaxy Clustering in the Mira-Titan Universe. I. Emulators for the Redshift Space Galaxy Correlation Function and Galaxy–Galaxy Lensing

   https://doi.org/10.3847/1538-4357/acd92f  

   Kwan, Juliana ; Saito, Shun ; Leauthaud, Alexie ; Heitmann, Katrin ; Habib, Salman ; Frontiere, Nicholas ; Guo, Hong ; Huang, Song ; Pope, Adrian ; Rodriguéz-Torres, Sergio ( July 2023 , The Astrophysical Journal)

   We construct accurate emulators for the projected and redshift space galaxy correlation functions and excess surface density as measured by galaxy–galaxy lensing, based on halo occupation distribution modeling. Using the complete Mira-Titan suite of 111N-body simulations, our emulators vary over eight cosmological parameters and include the effects of neutrino mass and dynamical dark energy. We demonstrate that our emulators are sufficiently accurate for the analysis of the Baryon Oscillation Spectroscopic Survey DR12 CMASS galaxy sample over the range 0.5 ≤r≤ 50h⁻¹Mpc. Furthermore, we show that our emulators are capable of recovering unbiased cosmological constraints from realistic mock catalogs over the same range. Our mock catalog tests show the efficacy of combining small-scale galaxy–galaxy lensing with redshift space clustering and that we can constrain the growth rate andσ₈to 7% and 4.5%, respectively, for a CMASS-like sample using only the measurements covered by our emulator. With the inclusion of a cosmic microwave background prior onH₀, this reduces to a 2% measurement of the growth rate.

    

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2. Galaxy populations in the most distant SPT-SZ clusters: II. Galaxy structural properties in massive clusters at 1.4 ≲ z ≲ 1.7

   https://doi.org/10.1051/0004-6361/202245268  

   Strazzullo, V. ; Pannella, M. ; Mohr, J. J. ; Saro, A. ; Ashby, M. L. ; Bayliss, M. B. ; Canning, R. E. ; Floyd, B. ; Gonzalez, A. H. ; Khullar, G. ; et al ( January 2023 , Astronomy & Astrophysics)

   We investigate structural properties of massive galaxy populations in the central regions (< 0.7  r 500 ) of five very massive ( M 200  > 4 × 10 14   M ⊙ ), high-redshift (1.4 ≲  z  ≲ 1.7) galaxy clusters from the 2500 deg 2 South Pole Telescope Sunyaev Zel’dovich effect (SPT-SZ) survey. We probe the connection between galaxy structure and broad stellar population properties at stellar masses of log( M / M ⊙ ) > 10.85. We find that quiescent and star-forming cluster galaxy populations are largely dominated by bulge- and disk-dominated sources, respectively, with relative contributions being fully consistent with those of field counterparts. At the same time, the enhanced quiescent galaxy fraction observed in these clusters with respect to the coeval field is reflected in a significant morphology-density relation, with bulge-dominated galaxies already clearly dominating the massive galaxy population in these clusters at z  ∼ 1.5. At face value, these observations show no significant environmental signatures in the correlation between broad structural and stellar population properties. In particular, the Sersic index and axis ratio distribution of massive, quiescent sources are consistent with field counterparts, in spite of the enhanced quiescent galaxy fraction in clusters. This consistency suggests a tight connection between quenching and structural evolution towards a bulge-dominated morphology, at least in the probed cluster regions and galaxy stellar mass range, irrespective of environment-related processes affecting star formation in cluster galaxies. We also probe the stellar mass–size relation of cluster galaxies, and find that star-forming and quiescent sources populate the mass–size plane in a manner largely similar to their field counterparts, with no evidence of a significant size difference for any probed sub-population. In particular, both quiescent and bulge-dominated cluster galaxies have average sizes at fixed stellar mass consistent with their counterparts in the field. 

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3. 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)
4. What boost galaxy mergers in two massive galaxy protoclusters at z  = 2.24?

   https://doi.org/10.1093/mnras/stad1543  

   Liu, Shuang ; Zheng, Xian Zhong ; Shi, Dong Dong ; Cai, Zheng ; Fan, Xiaohui ; Wang, Xin ; Yuan, Qirong ; Xu, Haiguang ; Pan, Zhizheng ; Liu, Wenhao ; et al ( May 2023 , Monthly Notices of the Royal Astronomical Society)

   Characterizing the structural properties of galaxies in high-redshift protoclusters is key to our understanding of the environmental effects on galaxy evolution in the early stages of galaxy and structure formation. In this study, we assess the structural properties of 85 and 87 Hα emission-line candidates (HAEs) in the densest regions of two massive protoclusters, BOSS1244 and BOSS1542, respectively, using the Hubble Space Telescope (HST) H-band imaging data. Our results show a true pair fraction of 22 ± 5 (33 ± 6) per cent in BOSS1244 (BOSS1542), which yields a merger rate of 0.41 ± 0.09 (0.52 ± 0.04) Gyr−1 for massive HAEs with log (M*/M⊙) ≥ 10.3. This rate is 1.8 (2.8) times higher than that of the general fields at the same epoch. Our sample of HAEs exhibits half-light radii and Sérsic indices that cover a broader range than field star-forming galaxies. Additionally, about 15 per cent of the HAEs are as compact as the most massive (log (M*/M⊙) ≳ 11) spheroid-dominated population. These results suggest that the high galaxy density and cold dynamical state (i.e. velocity dispersion of <400 km s−1) are key factors that drive galaxy mergers and promote structural evolution in the two protoclusters. Our findings also indicate that both the local environment (on group scales) and the global environment play essential roles in shaping galaxy morphologies in protoclusters. This is evident in the systematic differences observed in the structural properties of galaxies between BOSS1244 and BOSS1542.

    

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5. 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 mirror 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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