Neta Bahcall

We present the splashback radius measurements around the SRG/eROSITA eFEDS X-ray selected galaxy clusters by cross-correlating them with HSC S19A photometric galaxies. The X-ray selection is expected to be less affected by systematics related to projection that affects optical cluster finder algorithms. We use a nearly volume-limited sample of 109 galaxy clusters selected in 0.5–2.0 keV band having luminosity within the redshift z < 0.75 and obtain measurements of the projected cross-correlation with a signal to noise of 17.43. We model our measurements to infer a 3D profile and find that the steepest slope is sharper than −3 and associate the location with the splashback radius. We infer the value of the 3D splashback radius . We also measure the weak-lensing signal of the galaxy clusters and obtain halo mass using the HSC-S16A …

We determine the total stellar mass fraction (stellar mass/total mass) in clusters of galaxies using data from the Dark Energy Survey for~ 300 clusters in the redshift range 0.2-0.3 (Zhang et al. 2019). We use the total observed luminosity of the clusters, including their Brightest Cluster Galaxy (BCG), satellite galaxies, and Intracluster Light (ICL). Previous studies claimed that clusters are inefficient in star formation when investigating the stellar light in the BCG relative to the total cluster mass; the stellar mass of the BCG relative to the total cluster mass drops sharply with increasing cluster mass. Here we find that when the total stellar mass in clusters is included, as obtained from the total cluster luminosity, clusters are not inefficient in star formation. In fact, we find that clusters are as efficient in star formation as expected from the sum of their individual cluster members. We find the total stellar mass fraction in rich clusters …

We report the first detection of the dark matter distribution around Lyman break galaxies (LBGs) at high redshift through the cosmic microwave background (CMB) lensing measurements with the public Planck PR3 κ map. The LBG sample consists of 1 473 106 objects with the median redshift of z∼ 4 that are identified in a total area of 305 deg 2 observed by the Hyper Suprime-Cam Strategic Survey Program survey. After careful investigations of systematic uncertainties, such as contamination from foreground galaxies and cosmic infrared background, we obtain the significant detection of the CMB lensing signal at 5.1 σ that is dominated by 2-halo term signals of the LBGs. Fitting a simple model consisting of the Navarro-Frenk-White profile and the linear-bias model, we obtain the typical halo mass of M h= 2. 9− 2.5+ 9.5× 10 11 h− 1 M⊙. Combining the CMB lensing and galaxy-galaxy clustering signals on the large …

Vera Rubin: A Life is a wonderful book about one of the most influential female astronomers of our time, Vera C. Rubin (pictured), who used her meticulous observations of galaxies to help establish the existence of dark matter in the Universe. The book provides an excellent portrayal of the life and science of this remarkable scientist—a trailblazing astronomer, a true mentor and role model to generations of scientists, a tireless champion of women in science, and a kind and caring human being. This is an informative book for all readers, be they students, professionals or the general public. It tells the inspiring story of a dedicated scientist, her great love of astronomy, her resilience in overcoming many barriers and difficulties, never giving up, never losing her optimism, enthusiasm and kindness throughout, and, eventually, making exciting discoveries and finding fame. The reader will be moved, inspired and …

Using deep images from the Hyper Suprime-Cam (HSC) survey and taking advantage of its unprecedented weak lensing capabilities, we reveal a remarkably tight connection between the stellar mass distribution of massive central galaxies and their host dark matter halo mass. Massive galaxies with more extended stellar mass distributions tend to live in more massive dark matter haloes. We explain this connection with a phenomenological model that assumes, (1) a tight relation between the halo mass and the total stellar content in the halo, (2) that the fraction of in situ and ex situ mass at r <10 kpc depends on halo mass. This model provides an excellent description of the stellar mass functions (SMFs) of total stellar mass () and stellar mass within inner 10 kpc () and also reproduces the HSC weak lensing signals of massive galaxies with different stellar mass distributions. The best-fitting model shows that halo …

Mankind has long been fascinated by the mysteries of our Universe: How old and how big is the Universe? How did the Universe begin and how is it evolving? What is the composition of the Universe and the nature of its dark matter and dark energy? What is our Earth’s place in the cosmos and are there other planets (and life) around other stars?The 2019 Nobel Prize in Physics honors three pioneering scientists for their fundamental contributions to these cosmic questions—Professors James Peebles of Princeton University, Michel Mayor of the University of Geneva, and Didier Queloz of the University of Geneva and the University of Cambridge—“for contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos,” with one half to James Peebles “for theoretical discoveries in physical cosmology,” and the other half jointly to Michel Mayor and Didier Queloz “for the discovery of an …