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  1. Abstract

    The HectoMAP survey provides a complete, mass-limited sample of 30,231 quiescent galaxies withi-band Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) imaging that spans the redshift range 0.2 <z< 0.6. We combine half-light radii based on HSC SSP imaging with redshifts andDn4000 to explore the size–mass relation,Re=A×M*α, and its evolution for the entire HectoMAP quiescent population and for two subsets of the data. Newcomers with 1.5 <Dn4000 < 1.6 at each redshift show a steeper increase inAas the universe ages than the population that descends from galaxies that are already quiescent at the survey limit,z∼ 0.6 (the resident population). In broad agreement with previous studies, evolution in the size–mass relation both for the entire HectoMAP sample and for the resident population (but not for the newcomers alone) is consistent with minor merger driven growth. For the resident population, the evolution in the size–mass relation is independent of the population age atz∼ 0.6. The contrast between the sample of newcomers and the resident population provides insight into the role of commonly termed “progenitor bias” on the evolution of the size–mass relation.

  2. Abstract We use IllustrisTNG simulations to explore the dynamic scaling relation between massive clusters and their—central—brightest cluster galaxies (BCGs). The IllustrisTNG-300 simulation we use includes 280 massive clusters from the z = 0 snapshot with M 200 > 10 14 M ⊙ , enabling a robust statistical analysis. We derive the line-of-sight velocity dispersion of the stellar particles of the BCGs ( σ *,BCG ), analogous to the observed BCG stellar velocity dispersion. We also compute the subhalo velocity dispersion to measure the cluster velocity dispersion ( σ cl ). Both σ *,BCG and σ cl are proportional to the cluster halo mass, but the slopes differ slightly. Thus, like the observed relation, σ *,BCG / σ cl declines as a function of σ cl , but the scatter is large. We explore the redshift evolution of the σ *,BCG − σ cl scaling relation for z ≲ 1 in a way that can be compared directly with observations. The scaling relation has a similar slope at high redshift, but the scatter increases because of the large scatter in σ *,BCG . The simulations imply that high-redshift BCGs are dynamically more complex than their low-redshift counterparts.
    Free, publicly-accessible full text available May 1, 2023
  3. ABSTRACT In this paper, we use Hubble Space Telescope/WFC3 observations of six galaxies from the DYnamics of Newly Assembled Massive Object (DYNAMO) survey, combined with stellar population modelling of the SED, to determine the stellar masses of DYNAMO clumps. The DYNAMO sample has been shown to have properties similar to z ≈ 1.5 turbulent, clumpy discs. DYNAMO sample clump masses offer a useful comparison for studies of z > 1 in that the galaxies have the same properties, yet the observational biases are significantly different. Using DYNAMO, we can more easily probe rest-frame near-IR wavelengths and also probe finer spatial scales. We find that the stellar mass of DYNAMO clumps is typically 107−108M⊙. We employ a technique that makes non-parametric corrections in removal of light from nearby clumps, and carries out a locally determined disc subtraction. The process of disc subtraction is the dominant effect, and can alter clump masses at the 0.3 dex level. Using these masses, we investigate the stellar mass function (MF) of clumps in DYNAMO galaxies. DYNAMO stellar MFs follow a declining power law with slope α ≈ −1.4, which is slightly shallower than, but similar to what is observed in z > 1 lensed galaxies. Wemore »compare DYNAMO clump masses to results of simulations. The masses and galactocentric position of clumps in DYNAMO galaxies are more similar to long-lived clumps in simulations. Similar to recent DYNAMO results on the stellar population gradients, these results are consistent with simulations that do not employ strong ‘early’ radiative feedback prescriptions.« less
    Free, publicly-accessible full text available March 31, 2023