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1. Lopsided Galaxy Distributions in Massive TNG300 Clusters

   https://doi.org/10.3847/2515-5172/ad34b1  

   Mangis, Kelsey A.; Brainerd, Tereasa G. (March 2024, Research Notes of the AAS)

   Abstract Studies of isolated central galaxies and their satellites have shown that the spatial distributions of the satellites are distinctly “lopsided” with respect to the locations of the central galaxies. Here we extend this type of analysis to larger systems by analyzing the lopsidedness of 280 massive galaxy clusters in the IllustrisTNG300 Λ Cold Dark Matter simulation. Using a pairwise clustering statistic, we compute the probability that pairs of cluster galaxies are separated by a given polar angle difference, Δϕ, in the plane of the sky. Relative to the location of the central cluster galaxy, we find a statistically significant excess of galaxy pairs that are located on the same side of the cluster. The lopsidedness of the galaxy distribution is most pronounced for large clusters and for pairs of intrinsically red galaxies. The results summarized here were presented at the 243rd meeting of the American Astronomical Society. 

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2. Massive black hole assembly in nuclear star clusters

   https://doi.org/10.1103/PhysRevD.108.083012  

   Kritos, Konstantinos; Berti, Emanuele; Silk, Joseph (October 2023, Physical Review D)
3. Embedded Young Massive Star Clusters in the Antennae Merger

   https://doi.org/10.3847/1538-4357/ac5628  

   He, Hao; Wilson, Christine; Brunetti, Nathan; Finn, Molly; Bemis, Ashley; Johnson, Kelsey (March 2022, The Astrophysical Journal)

   Abstract The properties of young massive clusters (YMCs) are key to understanding the star formation mechanism in starburst systems, especially mergers. We present Atacama Large Millimeter/submillimeter Array high-resolution (∼10 pc) continuum (100 and 345 GHz) data of YMCs in the overlap region of the Antennae galaxy. We identify six sources in the overlap region, including two sources that lie in the same giant molecular cloud (GMC). These YMCs correspond well with radio sources in lower-resolution continuum (100 and 220 GHz) images at GMC scales (∼60 pc). We find most of these YMCs are bound clusters through virial analysis. We estimate their ages to be ∼1 Myr and that they are either embedded or just beginning to emerge from their parent cloud. We also compare each radio source with a Pa β source, and find they have consistent total ionizing photon numbers, which indicates they are tracing the same physical source. By comparing the free–free emission at ∼10 pc scale and ∼60 pc scale, we find that ∼50% of the free–free emission in GMCs actually comes from these YMCs. This indicates that roughly half of the stars in massive GMCs are formed in bound clusters. We further explore the mass correlation between YMCs and GMCs in the Antennae and find it generally agrees with the predictions of the star cluster simulations. The most massive YMC has a stellar mass that is 1%–5% of its host GMC mass. 

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4. Ubiquitous cold and massive filaments in cool core clusters

   https://doi.org/10.1051/0004-6361/201935350  

   Olivares, V.; Salome, P.; Combes, F.; Hamer, S.; Guillard, P.; Lehnert, M. D.; Polles, F. L.; Beckmann, R. S.; Dubois, Y.; Donahue, M.; et al (November 2019, Astronomy & Astrophysics)

   Multi-phase filamentary structures around brightest cluster galaxies (BCG) are likely a key step of AGN-feedback. We observed molecular gas in three cool cluster cores, namely Centaurus, Abell S1101, and RXJ1539.5, and gathered ALMA (Atacama Large Millimeter/submillimeter Array) and MUSE (Multi Unit Spectroscopic Explorer) data for 12 other clusters. Those observations show clumpy, massive, and long (3−25 kpc) molecular filaments, preferentially located around the radio bubbles inflated by the AGN. Two objects show nuclear molecular disks. The optical nebula is certainly tracing the warm envelopes of cold molecular filaments. Surprisingly, the radial profile of the H α /CO flux ratio is roughly constant for most of the objects, suggesting that (i) between 1.2 and 6 times more cold gas could be present and (ii) local processes must be responsible for the excitation. Projected velocities are between 100 and 400 km s −1 , with disturbed kinematics and sometimes coherent gradients. This is likely due to the mixing in projection of several thin (and as yet) unresolved filaments. The velocity fields may be stirred by turbulence induced by bubbles, jets, or merger-induced sloshing. Velocity and dispersions are low, below the escape velocity. Cold clouds should eventually fall back and fuel the AGN. We compare the radial extent of the filaments, r fil , with the region where the X-ray gas can become thermally unstable. The filaments are always inside the low-entropy and short-cooling-time region, where t cool / t ff  <  20 (9 of 13 sources). The range of t cool / t ff of 8−23 at r fil , is likely due to (i) a more complex gravitational potential affecting the free-fall time t ff (sloshing, mergers, etc.) and (ii) the presence of inhomogeneities or uplifted gas in the ICM, affecting the cooling time t cool . For some of the sources, r fil lies where the ratio of the cooling time to the eddy-turnover time, t cool / t eddy , is approximately unity. 

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5. The Massive and Distant Clusters of WISE Survey. V. Extended Radio Sources in Massive Galaxy Clusters at z ∼ 1

   https://doi.org/10.3847/1538-4357/aaf569  

   Moravec, Emily; Gonzalez, Anthony H.; Stern, Daniel; Brodwin, Mark; Clarke, Tracy; Decker, Bandon; Eisenhardt, Peter R.; Mo, Wenli; O’Donnell, Christine; Pope, Alexandra; et al (February 2019, The Astrophysical Journal)