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1. The Assembly of the First Massive Black Holes

   https://doi.org/10.1146/annurev-astro-120419-014455  

   Inayoshi, Kohei; Visbal, Eli; Haiman, Zoltán (August 2020, Annual Review of Astronomy and Astrophysics)

   null (Ed.)

   The existence of ∼10 9 M ⊙ supermassive black holes (SMBHs) within the first billion years of the Universe has stimulated numerous ideas for the prompt formation and rapid growth of black holes (BHs) in the early Universe. Here, we review ways in which the seeds of massive BHs may have first assembled, how they may have subsequently grown as massive as ∼10 9 M ⊙ , and how multimessenger observations could distinguish between different SMBH assembly scenarios. We conclude the following: ▪  The ultrarare ∼10 9 M ⊙ SMBHs represent only the tip of the iceberg. Early BHs likely fill a continuum from the stellar-mass (∼10M ⊙ ) to the supermassive (∼10 9 ) regimes, reflecting a range of initial masses and growth histories. ▪  Stellar-mass BHs were likely left behind by the first generation of stars at redshifts as high as ∼30, but their initial growth typically was stunted due to the shallow potential wells of their host galaxies. ▪  Conditions in some larger, metal-poor galaxies soon became conducive to the rapid formation and growth of massive seed holes, via gas accretion and by mergers in dense stellar clusters. ▪  BH masses depend on the environment (such as the number and properties of nearby radiation sources and the local baryonic streaming velocity) and on the metal enrichment and assembly history of the host galaxy. ▪  Distinguishing between assembly mechanisms will be difficult, but a combination of observations by the Laser Interferometer Space Antenna (probing massive BH growth via mergers) and by deep multiwavelength electromagnetic observations (probing growth via gas accretion) is particularly promising. 

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2. The Massive and Distant Clusters of WISE Survey. VIII. Radio Activity in Massive Galaxy Clusters

   https://doi.org/10.3847/1538-4357/abb08d  

   Mo, Wenli; Gonzalez, Anthony; Brodwin, Mark; Decker, Bandon; Eisenhardt, Peter; Moravec, Emily; Stanford, S. A.; Stern, Daniel; Wylezalek, Dominika (September 2020, The Astrophysical Journal)
3. Massive Star Formation in the Tarantula Nebula

   https://doi.org/10.3847/1538-4357/acac8b  

   Nayak, Omnarayani; Green, Alex; Hirschauer, Alec S.; Indebetouw, Rémy; Meixner, Margaret; Wong, Tony; Chevance, Mélanie; De Marchi, Guido; Lebouteiller, Vianney; Lee, Min-Young; et al (February 2023, The Astrophysical Journal)

   Abstract In this work, we present 299 candidate young stellar objects (YSOs) in 30 Doradus discovered using Spitzer and Herschel point-source catalogs, 276 of which are new. We study the parental giant molecular clouds in which these YSO candidates form using recently published Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 7 observations of 12 CO and 13 CO. The threshold for star formation in 30 Doradus inferred by the LTE-based mass surface density is 178 M ⊙ pc −2 , 40% higher than the threshold for star formation in the Milky Way. This increase in star formation threshold in comparison to the Milky Way and increase in line width seen in clumps 11 pc away in comparison to clumps 45 pc away from the R136 super star cluster could be due to injected turbulent energy, increase in interstellar medium pressure, and/or local magnetic field strength. Of the 299 YSO candidates in this work, 62% are not associated with 12 CO molecular gas. This large fraction can be explained by the fact that 75%–97% of the H 2 gas is not traced by CO. We fit a Kroupa initial mass function to the YSO candidates and find that the total integrated stellar mass is 18,000 M ⊙ and that the region has a star formation rate (SFR) of 0.18 M ⊙ yr −1 . The initial mass function determined here applies to the four 150″ × 150″ (37.5 pc × 37.5 pc) subfields and one 150″ × 75″ (37.5 pc × 18.8 pc) subfield observed with ALMA. The SFR in 30 Doradus has increased in the past few million years. 

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4. The most massive white dwarfs in the solar neighbourhood

   https://doi.org/10.1093/mnras/stab767  

   Kilic, Mukremin; Bergeron, P; Blouin, Simon; Bédard, A (April 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than $$1.3\, {\rm M}_{\odot }$$ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to M = 1.334 M⊙, which corresponds to the high-density limit of our equation-of-state tables, ρ = 109 g cm−3. We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products. 

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5. The MASSIVE Survey. XV. A Stellar Dynamical Mass Measurement of the Supermassive Black Hole in Massive Elliptical Galaxy NGC 1453

   https://doi.org/10.3847/1538-4357/ab6f71  

   Liepold, Christopher M.; Quenneville, Matthew E.; Ma, Chung-Pei; Walsh, Jonelle L.; McConnell, Nicholas J.; Greene, Jenny E.; Blakeslee, John P. (March 2020, The Astrophysical Journal)