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The First eROSITA All-Sky Survey

Galaxy Group origin of the Odd Radio Circles

Bulbul et al. (2024b)

Odd radio circles (ORCs) are a newly discovered class of extended faint radio sources of unknown origin. We report the first detection of diffuse X-ray gas at the location of a low-redshift ORC (z=0.046) known as Cloverleaf ORC. The presence of a high-velocity subgroup identified in optical data, the orientation of the brightest cluster galaxy, the disturbed morphologies of galaxies toward the east of the Cloverleaf ORC, and the irregular morphology of the X-ray emission suggest that this system is undergoing a galaxy group merger. The radio power of the ORC could be explained by the shock reacceleration of fossil cosmic rays generated by a previous episode of black hole activity in the central active galactic nucleus.


Cosmological Constraints from Cluster Abundances

Ghirardini et al. (2024)

he cluster mass function traces the growth of linear density perturbations. It provides valuable insights into the growth of structures and the cosmological parameters governing the Universe. The primary science goal of eROSITA, on board the SRG mission, launched in 2019, is to constrain cosmology through the evolution of cluster mass function. The cluster abundances constrain the LCDM parameters, which are the energy density of the total matter and the normalization of the density fluctuations, to be consistent and at a similar precision with the state-of-the-art CMB measurements.

Constraints on Alternative Gravity Models

Artis et al. (2024)

The evolution of the cluster mass function traces the growth of the linear density perturbations and can be utilized for constraining alternative gravity models.or the first time, we present constraints obtained from cluster abundances only. We find a strict upper limit of log |fR0| < -4.31 from cluster abundances only for the first time. Consequently, we do not find any statistical deviation from general relativity from the study of eRASS1 cluster abundances.


Tracing the Large-Scale Structure with a clustering study of galaxy clusters

Seppi et al. (2024)

The spatial distribution of galaxy clusters provides a reliable tracer of the large-scale distribution of matter in the Universe. In this work, we measure the projected two-point correlation function to study the occupation of dark matter halos by clusters and groups detected by the first eROSITA all-sky survey. We constrain the correlation function with halo occupation distribution and halo abundance matching models by simultaneously fitting the cosmological parameters.


Constraints on the Feedback by Supermassive Blackholes in Galaxy Groups

Bahar et al. (2024)

In this work, we stack eROSITA observations of 1178 galaxy groups detected in the first All-Sky Survey to measure thermodynamic properties, including electron density, temperature, and entropy of the intragroup gas. We present the tightest constraints on the impact of AGN feedback through our average entropy and characteristic temperature measurements. The comparisons with the state-of-the-art cosmological hydrodynamic simulations (MillenniumTNG, Magneticum, OWL simulations) reveal that observed entropy profiles in the cores are below the predictions of simulations.


The first catalog of superclusters in the western Galactic hemisphere

Liu et al. 2024

Superclusters are large-scale systems formed through galaxy cluster clustering, marking the overdense regions in the Universe. In this work, we search and study superclusters in the X-ray Universe leveraging the galaxy cluster catalog obtained from the first eROSITA All-Sky Survey. We construct a catalog of more than 1300 supercluster systems, representing the largest-ever X-ray supercluster sample. The large-scale structure depicted by the eRASS1 superclusters perfectly matches the 3D distribution of galaxies in our Universe (see the attached movie).

Optical Identification and Properties of Galaxy Clusters and Groups

Kluge et al. 2024

We present the largest collection of galaxy clusters and groups across the western galactic hemisphere, using the groundbreaking first SRG/eROSITA All-Sky Survey. Combining X-ray data with optical and near-infrared observations from the Legacy Surveys, we identify over 12,000 galaxy clusters and groups and determine their optical properties, such as distance and size, with unmatched accuracy. This extensive dataset not only sets a new standard for the purity and completeness of galaxy cluster catalogs but is also a crucial ingredient for accompanied cosmological analyses that test our best theories of the cosmos.


The first catalog of galaxy clusters and groups in the Western Galactic Hemisphere

Bulbul et al. 2024

The driving science goal of the SRG/eROSITA All-Sky Survey (eRASS) is to assemble a large sample of X-ray-selected clusters with a well-defined selection function to determine the evolution of the mass function and, hence, the cosmological parameters. We present here a catalog of 12247 optically confirmed galaxy groups and clusters detected in the 0.2-2.3 keV as extended X-ray sources in a 13,116 deg^2 region in the western Galactic hemisphere of the sky, which eROSITA surveyed in its first six months of operation. The clusters in the sample span the redshift range 0.003<z<1.32. We also provide the cosmology catalog, which is used to drive cosmology results.

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