![]() ![]() Low-mass and high-mass subsets were defined by selecting the top and bottom 25 % of clusters by mass in each redshift bin. We find a strong and significant (≈ 10.1σ) evolution of α with redshift for the total composite LFs. For our total redshift-binned LFs, we obtained a characteristic magnitude of m^∗ = 18.51± 0.02, and faint-end slope of α = -1.18 ± 0.01 at = 0.225. A χ^2 minimization technique was then used to estimate the best-fit parameters, m^∗ and α, from the Schechter model. A single Schechter function was fitted to 12 redshift-binned composite LFs and 12 low-mass and high-mass subset LFs. An LF of each cluster was weighted according to the richness and number of contributing galaxies to construct the composite LF. Cluster membership was determined probabilistically using galaxy photometric redshift probability distributions. Taking advantage of accurate photometry from DECaLS, we used photometric redshifts to construct redshift-binned and mass-binned composite LFs over the apparent magnitude range of 17.0 < m_r < 22.5. This type of study has never been performed on this specific cluster sample over this chunk of cosmic time. ![]() We examine the galaxy population of 3008 Sunyaev-Zel’dovich (SZ)-selected galaxy clusters, drawn from the Atacama Cosmology Telescope Data Release 5 (ACT DR5) sample, by measuring their composite r-band LFs from 0.20 < z < 0.80 using optical data from the ninth data release of the Dark Energy Camera Legacy Survey (DECaLS DR9). Deriving LFs in clusters is generally a simple task since they provide a rich collection of galaxies at the same distance, and the density with respect to the surrounding environment is high enough to identify members both photometrically and spectroscopically. Accurate measurements of the LF can tell us how environmental processes influence the properties of current galaxy populations, helping us obtain clues as to which processes are important in shaping galaxy formation and evolution. The galaxy luminosity function (LF) describes the number of galaxies per unit volume as a function of their luminosity. We show that the classic definition of ultra-diffuse galaxies is heavily weighted towards quenched galaxies and thus cannot be used for a study of quenching of mass-size outliers. In contrast, the ultra-diffuse galaxies are overall redder and more quiescent compared with normal satellites. ![]() The quenched fraction is higher for the ultra-puffy galaxies associated with redder hosts as well as those that are closer to the host in projection. Surprisingly, despite being outliers in size, the ultra-puffy galaxies have a similar quenched fraction as normal-sized satellites of Milky Way analogs in both observations and simulations, suggesting that quenching is not tied to being a mass-size outlier. We present the size and radial distributions of mass-size outliers, and derive their quenched fraction to explore the impact of environment. Using the exquisitely deep and wide Hyper Suprime-Cam Strategic Survey images, we search for ultra-puffy galaxies, defined as being $1.5\sigma$ larger than the average size for their mass, around Milky-Way-like galaxies. However, the origin and evolution of these mass-size outliers and the role of environment are still unclear. Recent observations have reignited interest in a population of dwarf galaxies that are large and diffuse for their mass, often called ultra-diffuse galaxies. approximately a sound crossing time), as discussed in the text. The green dashed curve corresponds to equation (7) with α= 2 but with a time-delay factor that accounts for how long it takes for the galaxy to respond to ram pressure stripping (i.e. In both the top and bottom panels, the horizontal dotted lines correspond to the predictions of equation (7) for α= 2, 4, 6, 8 and 10 (bottom to top panel). Thus, the ram pressure is the same for both cases in the bottom panel. In the bottom panel, the same galaxy is run through two different media: the thick red curve corresponds to the case where the background density is the same as in the top panel, but the velocity is 760 km s−1, while the thin red curve corresponds to the case where the velocity is 1000 km s−1 but the density is a factor of (1000/760)2 times lower than in the top panel. The solid red and dashed blue curves show the bound mass of gas and dark matter, respectively, in the simulation. In the top panel, a galaxy of mass M200= 4 × 1012 M⊙ is run through a uniform gaseous medium of density 100 fbρcrit at a velocity of 1000 km s−1. An example of ram pressure stripping in the uniform medium simulations. ![]()
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