The growth of galaxies in the local Universe critically depends on the physical conditions of the hot phase of the interstellar and the circumgalactic medium and on its interplay (via outflows and re-condensation) with the other phases.
The X-ray data from the eROSITA all sky survey are allowing us to get an unprecedented view of the hot plasma, within the Galactic echo-system.
In...
The solar neighbourhood is a volume devoid of neutral material. Instead, it is displaced by a soft X-ray-emitting plasma. This region is known as the local hot bubble (LHB). A holistic view of this emission requires a large covering area, first delivered by the ROSAT All Sky Survey about three decades ago. The properties of the LHB were measured but were unfortunately clouded by the discovery...
In X-ray observations, scattering of photons on dust along the line of sight can lead to the formation of an extended X-ray halo around any source. We have used data from eROSITA to study these dust scattering halos around 29 point sources in eRASS 1.
For bright sources, which are needed to observe halos at the high scattering angles made accessible by eROSITA, pile-up limits our abilities...
The Large Magellanic Cloud (LMC) is a large and nearby satellite galaxy of the Milky Way, which underwent multiple recent star formation episodes. Due to its low inclination and foreground absorption, the properties of the hot phase of its interstellar medium (ISM) can be ideally probed via its diffuse soft X-ray emission. This, in combination with deep available exposure due to the location...
Over the past few decades, multi-wavelength surveys have revolutionized our understanding of active galactic nuclei (AGN) demography, structure, physics, host galaxies and host/AGN co-evolution. Wide-field and deep X-rays and mid-infrared constraints have been particularly essential in this regard as a means to peer through the substantial dust obscuration that surrounds most strongly...
We present a uniform and sensitive X-ray census of active galactic nuclei (AGNs) in the two nearest galaxy clusters, Virgo and Fornax, utilizing the newly released X-ray source catalogs from the first all-sky scan of Spectrum-Roentgen-Gamma/eROSITA. A total of 50 and 10 X-ray sources are found positionally coincident with the nuclei of member galaxies in Virgo and Fornax, respectively, down to...
Determining when and where supermassive black hole growth - seen as Active Galactic Nuclei (AGN) - occurs within the evolving galaxy population is vital to understand the physical mechanisms that drive the growth of black holes as well as what triggers periods of AGN activity, and the impact of AGN feedback on galaxy growth. However, linking galaxy and AGN properties is complicated by the...
X-ray surveys of AGN provide direct constraints on the properties of individual AGN, such as their accretion, reflection, and obscuration. Previous AGN population synthesis models have not addressed such constraints self-consistently. Here we use a simulation-based inference (SBI) approach to constrain the geometrical and physical properties of the AGN population. We perform numerical...
I will present the hard ($2.3-5~$keV) X-ray selected sample of sources detected with eROSITA during the first all-sky survey, comprising 5466 X-ray sources. From this catalog, I have produced a large uniform sample of hard-X-ray selected AGN, and characterised them with supporting multi-wavelength astrometry, photometry and spectroscopy. For the 2863 sources within the sky coverage of the DESI...
Supermassive black holes (SMBHs) reside in the heart of virtually every massive galaxy. However, much less is known about whether dwarf galaxies commonly host SMBHs.
Exploiting the recently published eROSITA X-ray catalogue, we built a sample of actively accreting SMBHs in local dwarf galaxies. This uniformly selected sample of 74 AGN is, to date, one of the largest compilations of...
Bright X-ray sources have been discovered in nearby galaxies since the 1970s and with the wide X-ray surveys carried out with Chandra, XMM-Newton, Swift and eRosita, many more have been revealed. Those X-ray sources with luminosities greater than ~1e39 erg/s, lying outside of the central nucleus, have been referred to as ultraluminous X-ray sources (ULXs) and for the brightest, with...
The LIGO Scientific Collaboration and Virgo Collaboration have so far announced about 90 detections of gravitational waves, all of them associated with mergers of compact objects at high redshifts. These signals are transient and bright, typically presenting a strain amplitude of 10-21 for most of the time. By contrast, continuous gravitational waves (CWs) - a persistent though orders of...
July 13th (2 months ago) was the 5th anniversary of the launch of the Spectrum-Rentgen-Gamma Orbital Observatory on the space track to the 2nd Lagrangian point of the Sun-Earth system. But, like almost all space observatories, the path to launching the SRG was not simple and direct. It began in 1987 at an international meeting held in Moscow in honor of the 30th anniversary of the launch of...
When a star passes too close to a supermassive black hole (SMBH) it can be destroyed, temporarily increasing the accretion rate onto the SMBH. Such tidal disruption events (TDEs) produce bright flares across the electromagnetic spectrum that provide a unique window into the central region of a galaxy, including the previously dormant black hole. Radio observations of TDEs are essential for...
Active galactic nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH) but the structure of this flow is not well understood. Standard accretion disc models match only to zeroth order in predicting the substantial energy dissipated in optically-thick material producing a strong blue/UV continuum. More detailed comparisons to the observed spectral shapes...
Blazars are highly variable radio-loud AGN, with jets closely aligned with the line-of-sight. These sources can be observed over the entire electromagnetic spectrum and are well monitored at, e.g., radio or gamma-ray wavelengths. The eROSITA telescope with its all-sky survey presents a unique opportunity to obtain an unbiased view of the blazar population in the X-ray band. By matching the...
X-ray Quasi-Periodic Eruptions (QPEs) are high-amplitude bursts of X-ray radiation recurring every few hours and originating near the central black holes in galactic nuclei of low-mass galaxies. So far, only a handful of such events has been found, although with rising interest in the broader community given their observational and theoretical connection with tidal disruption events and,...
eROSITA's time-domain capabilities have enabled the discovery and characterization of four new quasi-periodic X-ray eruption (QPE) sources. A wealth of X-ray follow-up observations exists, as does a large number of theoretical models that can broadly explain the X-ray properties of QPEs. While characterizing these sources in more detail with X-ray observations is valuable, multi-wavelength...
The flux magnification by strong gravitational lensing allows detailed observations of QSOs at high redshifts which would otherwise only be possible for a few extremly luminous objects. Recently there has also been renewed interest in the study of lensed QSOs due to the possibility of independent and accurate measurements of the Hubble constant using time-delay cosmography in lensed QSO...
Multiwavelength information is crucial for a complete understanding of the Universe. In the era of big data, large-number statistics is the ideal tool to characterize the demography of galaxy populations and understand the complex phenomena involved in galaxy evolution. Within SPIDERS (Spectroscopic Identification of ERosita Sources), we selected eROSITA X-ray sources to be observed in the...
A complete census of SMBH increases our understanding of the role of AGN evolution over cosmic time. As AGN detection is less affected by obscuration effects in the X-ray window, eROSITA offers increased likelihood and purity in detecting these objects. That being said, a substantial fraction of spectroscopic redshifts for AGN identified by eROSITA will be available only in 2-3 years from now...
I will discuss past and current efforts to simulate the circumgalactic medium around galaxies, I will review theoretical predictions for its physical properties and impact on galaxy evolution and I will contrast these with results and future opportunities about the hot phase of such a halo gas around galaxies.
The first all-sky maps of high ionization lines observed in X-rays by eROSITA provide an excellent probe for the study of the hot phase (T ∼ 10^6 K) of the Milky Way (MW) circumgalactic medium (CGM). In this work we analyse the OVII and OVIII line detected in the eROSITA data. We fit sky maps made in narrow energy bins around the lines, with physical emission models embedded in a 3D geometry...
Low-mass galaxy groups are the most common environments for galaxies in the Universe, and they provide a crucial link between cosmology and galaxy evolution. However, their hot gas and baryon content are poorly constrained by current X-ray observations due to their low surface brightness. In this talk, I will demonstrate the efficiency of X-ray spectral stacking as a method to overcome these...
The CGM's hot phase probes the modern puzzles of galaxy formation and evolution as galaxies' feedback processes imprint their signatures in its volume-filling hot gas distribution. This talk presents state-of-art observed hot gas profiles of the CGM in Milky-Way-sized halos, obtained with the depth of eRASS:4 and the large area optical coverage of the LSS DR10 galaxy survey. Together with...
Every low-mass star in the Milky Way can be expected to host at least one exoplanet on average. Since most stars are intrinsic X-ray emitters, practically every exoplanet known today is embedded in an X-ray radiation environment of some sort. Stellar high-energy emission can drive many phenomena on exoplanets: heating and evaporation of planetary atmospheres, photoionization in the upper...
Accretion onto compact stellar remnants can give rise to luminous X-ray emission, whose properties depend on factors such as the accretion rate and geometry. The majority of the known stellar-mass black holes in the Galaxy have been discovered through their bright X-ray emission, predominantly during outbursts. However, while there are an estimated $10^8$ stellar-mass black holes in the Milky...
X-ray dim isolated neutron stars (XDINSs) are famous for their amazingly clean thermal X-ray emission. The small known population that comprises only a handful sources, however, demands new identifications before their population properties, evolution, and links to other isolated neutron star (INS) families can be constrained. With the potential to constitute a significant fraction of all...
The Magellanic Clouds are our closest star-forming galaxies with low Galactic foreground absorption. This makes them a unique laboratory to study the population of high-energy sources. The SMC hosts a large population of Be/X-ray binaries associated with high star formation activity 25-40 Myr ago. It has been proposed that the HMXB population in the LMC is associated with more recent star...
The supernovae (SNe) explosions expel the stellar interior of the star in the surrounding which enrich the interstellar medium (ISM) with metals. The interaction between the stellar interior and the ISM produce the supernova remnants (SNRs).. Their emission is visible in different wavelength from radio to X-ray. The SNRs can be studied to infer information about the explosion it self and on...
Through gas and stars bound within their gravitational potentials, the millions of massive dark matter halos that thread the web in our sky imprint arcminute-scale features across the electromagnetic spectrum. As surveys from radio to X-ray increase their grasp, populations of galaxy clusters grow in size and fidelity. In this talk I will review a simple, functional model for linking the...
The South Pole Telescope (SPT) is a 10-meter millimeter-wavelength telescope located at the geographic South Pole, one of the world's premier sites for millimeter-wave observations. The SPT has been used to conduct several generations of wide-field high resolution cosmic microwave background (CMB) surveys including the 2500-square-degree SPT-SZ survey, the SPTpol 500d and ECS surveys, and now...
The cosmic web is a network of structures composed of dark matter, galaxies, and gas. In this network, galaxy clusters and groups occupy the position of nodes, connected among them by filaments. Connectivity is a measurement of the number of filaments connected to a node of the cosmic web, be it a cluster or a group. Theoretical works predict a relationship between the connectivity of a node...
The X-ray-emission of high-redshift galaxy clusters and compact nearby groups hosting bright, active galactic nuclei (AGN) can be misclassified as point source emission by the source detection algorithms due to the sizeable point-spread function of eROSITA.
In an analogous way to the treatment of the extended source catalog, we search for clusters in the eROSITA point source catalog. For...
Galaxy cluster gas temperatures ($T$) are crucial for numerous cosmological and astrophysical applications. Potential $T$ biases can propagate to several such cluster applications. Thus, it is important to accurately cross-calibrate X-ray instruments to account for systematic biases. We present the first cross-calibration between eROSITA-Chandra, and between eROSITA-XMM-Newton, using a large...
Galaxy clusters have long proven to be a valuable cosmological tool: arising from the highest peaks of the matter density field, they serve as sensitive probes of the growth of structures and cosmic expansion. Current and upcoming wide-area surveys --- such as DES, Euclid, Rubin LSST, eROSITA, SPT and ACT --- seek to use the abundance and spatial distribution of galaxy clusters detected across...
Galaxy groups and clusters trace the distribution of the most prominent peaks in the matter density field at late time. Therefore, they provide valuable insights into the growth of structure in our Universe, the nature of dark matter, and, in general, the cosmological parameters that describe the content of our Universe and govern its formation and evolution. The primary science goal of...
Axion-like particles are viable dark matter candidates that would fit naturally in the concordance $\Lambda$CDM cosmological model. As bosonic particles, they form Bose-Einstein condensates with scales determined by their thermal de Broglie wavelength. Due to their extremely small masses, ultra-light axions with $10^{-22}$ eV masses can form condensates on scales comparable to dark matter...
Several tensions are currently challenging the standard cosmological model. Among them, the Hubble constant measured at early times is lower than the one inferred from late-time probes. Additionally, Planck indicates cosmological perturbations growing faster than what is inferred from large-scale structure probes. Consequently, it is fundamental to investigate potential deviations from its...
Recent measurements of cosmological parameters highlight possible tensions between values determined by CMB measurements and those determined by late epoch observations which could potentially challenge the current theoretical model, in particular for the clumpiness parameter σ8 which is related to the normalization of the primordial matter power spectrum. In this project, we investigate this...
To compare the observations of galaxy clusters with theoretical predictions and thus constrain the cosmological parameters of the underlying model, precise knowledge of cluster masses and redshifts is required. We provide a new $Y_{\text{SZ}} - M_{500}^{Y_X}$ scaling relation using a sample of clusters from the Planck Early Sunyaev-Zeldovich (ESZ) catalogue that was observed in X-rays by...
The presence of hot, volume-filling gas in galaxy clusters and groups allows for studying various astrophysical processes. In this review talk, I will highlight selected results on cluster mergers and ICM shocks, AGN feedback, and plasma physics, focusing on recent X-ray and radio observations and numerical modeling.
eROSITA allows us to resolve the entire Virgo Cluster and its outskirts on scales between 1 kpc and 3 Mpc, covering a total area on the sky of about 25 by 25 degrees. We present an exploration of the SRG/eROSITA data of the Virgo Cluster from five all-sky surveys. We utilize image manipulation techniques and surface brightness profiles to search for extended emission, surface brightness...
The Fornax cluster is one of the most nearby X-ray bright galaxy groups. Its proximity allows us to study its properties at high spatial resolution. We exploit the essentially unlimited field-of-view of five eROSITA all-sky surveys to study the Fornax cluster from kpc to Mpc scale, tracing the intracluster medium out to beyond the virial radius. We interpret the observations in combination...
We review recent advancements in the measurement of the weak gravitational lensing (WL) signature induced by the potentials of galaxy clusters onto the shapes of background galaxies. In the context of wide photometric surveys, we discuss how this poses unique challenges and opportunities and how we addressed and leveraged them. After discussing the recent advancements in the measurement of WL,...
In this talk I will present the cross-match of Dark Energy Survey (DES) redMaPPer clusters with the eROSITA All-Sky Survey (eRASS), which offers an unprecedented ~4000 deg$^2$ area of overlap between the DES and eRASS survey footprints. Previous efforts of cross-matching DES RM clusters with various X-ray archives, e.g., the XMM Cluster Sample, resulted in a few hundred clusters detected in...
The SRG/eROSITA all-sky survey delivers an unprecedented X-ray scan of the whole sky, which offers a great opportunity for large-scale structure studies. At the same time, the Subaru telescope is amongst the deepest and most powerful optical instruments, which provides a large selection of optically selected galaxy clusters via the detection of the overdensities of the red sequence galaxy...
The eROSITA telescope is revolutionizing X-ray astronomy with its ability to produce large all-sky surveys. eROSITA will catalog the hot intracluster medium (ICM) of thousands of galaxy clusters. This unprecedented sample of galaxy clusters is crucial for updating our theoretical understanding of the physics shaping the gaseous cores of clusters.
Inspired as a theoretical counterpart to...
Groups and clusters of galaxies are pervaded with hot gas (several tens to hundreds of million K), which emits in X-rays (mostly via bremsstrahlung) and which has been routinely observed with the last generations of X-ray telescopes. Because this intracluster medium (ICM) accounts for 70-90% of clusters' total baryonic content, it constitutes a central component in the growth and assembly of...
In the context of an evolutionary model, the outflow phase of an active galactic nucleus (AGN) occurs at the peak of its activity, once the central supermassive black hole (SMBH) is massive enough to generate sufficient power to counterbalance the potential well of the host galaxy. This outflow feedback phase plays a vital role in galaxy evolution. I will present results from our two recent...
Quasar winds blown from the accretion disc are potentially capable of expelling large quantities of gas from their host galaxies and may thus be an important mechanism for feedback. These winds are evident in rest-frame UV spectra in the form of blueshifted broad emission lines. How such winds are launched – and how such launching relates to the physical state of the accretion disc system that...
eROSITA has unleashed a deluge of observations of the stellar X-ray sky in a nexus with other powerful complementary capabilities, such as TESS and Gaia. At the same time, a feeding frenzy of the exoplanet field hungry for data on planetary energetic radiation environments has driven a renaissance of interest and research into stellar coronae and what used to be the backwater of high energy...
The eROSITA all-sky survey (eRASS) largely increased the number of well-characterized X-ray detected stars.
I will present our method, called HamStar, to identify these stars among all eROSITA sources. HamStar assigns
each eROSITA source a value, p_stellar, that describes the individual probability of the source to be stellar
in nature. HamStar uses a Bayesian-framework taking advantage...
The solar corona is often invoked as a template for stellar ones, but the significant difference between solar and non-solar instruments and data makes direct comparison between X-ray observations of the Sun, which is usually of the resolved solar disk, and stellar point-source observations almost impossible. In order to overcome this hurdle, the research group at INAF Osservatorio Astronomico...
We implemented the first half-sky SRG/eROSITA upper limit database to provide X-ray photometric data and flux upper limit to every position in the Western Galactic hemisphere. For variable objects, transients, or a large number of sources detected at wavelengths other than X-rays, eROSITA flux upper limits can be crucial to understanding their physical and statistical properties. Thus, the...
Our recently developed Space and Time Algorithm for Transients in X-rays (STATiX, Ruiz et al. 2024) builds upon tools from the image and signal processing fields and in particular the Multi-Scale Variance Stabilisation Transform (Starck et al. 2009) to provide a complete detection analysis pipeline optimised for finding transient sources on X-ray imaging observations. STATiX operates on...
The Early Data Release and eRASS1 data from the eROSITA space telescope have already revealed a remarkable number of previously undetected X-ray sources. Leveraging Bayesian inference and generative modeling techniques for X-ray imaging, we aim to enhance the sensitivity and scientific value of these observations by denoising, deconvolving, and decomposing the X-ray sky. Utilizing information...
The advent of the new generation of instrumentation in astrophysics like eROSITA poses several challenges due to the high-dimensional signals that vary in space, time, and energy. These typically have non-trivial correlation structures and are often a mixture of overlapping signal components that need to be separated. In order to facilitate multi-instrument analysis of correlated signals in...
For a deep understanding of the X-ray universe, it is crucial to rely on complete and accurate information on its primary constituents. These constituents, such as active galactic nuclei, galaxies, and other compact and diffuse objects display distinct features in the sky and therefore imprint differently on astronomical data. In this work, we leverage these differences to construct...
Despite the potential of GAIA DR3 to reveal a large population of black holes (BHs), only a few BHs have been discovered to date in orbit with luminous stars without an X-ray counterpart. It has recently been shown that black holes in orbit with main sequence companions seldom form accretion disks, from where observable X-ray flux is conventionally thought to be produced. Yet, even without...
The eROSITA all-sky X-ray (0.2-8.0 keV) survey, provides the first unbiased census of the X-ray emission of galaxies, allowing us to study the emission from X-ray binaries (XRBs) and the hot interstellar medium in the full range of stellar population parameters present in the local Universe. By combining the updated version of the HECATE v2.0 value-added catalogue of nearby galaxies...
X-ray binaries (XRBs) are our most accessible way to probe populations of Galactic compact objects in the X-ray regime, and offer crucial constraints on Galactic stellar evolution models. Previously reported distributions of XRBs plateau at intermediate luminosities of $10^{35}$ erg/s, and only reach fluxes down to a few $10^{-12}$ cgs. eROSITA’s improved sensitivity allows us to extend this...
Nova explosions are thermonuclear events on top of an accreting white dwarf in a cataclysmic variable (CV) or a symbiotic system. The nova event results in the increase of the optical luminosity by 7-8 orders of magnitude. That makes the nova outburst detectable at any distance in the Galaxy, in the Local Group and even beyond the Local Group. However, due to the resulting distance...
XMM-Newton observed several SRG/eROSITA detection allowing detailed studies due to the longer exposure time. The talk will present some highlights resulting from such joint studies.
Our nearest star-forming galaxy, the Large Magellanic Cloud (LMC), has been largely neglected in X-ray binary (XRB) populations studies targeting quiescent luminosities. In Chandra Cycle 24, we were awarded a Very Large Program (1 Ms) to perform a comprehensive survey of sources brighter than ~2 x 10^{32} erg/s in 10 LMC fields dominated by young (10 - 100 Myr) stellar populations of different...
I present the first volume-limited surveys of accreting compact binaries made possible through an SRG/eROSITA + Gaia crossmatch. In addition to SRG/eROSITA and Gaia data, I have made use of the Zwicky Transient Facility (ZTF), which has collected optical photometry down to 21 mag across the entire Northern sky for six years.I will primarily focus on cataclysmic variables, which are the most...
Astrophysical black holes are surprisingly simple physical objects. Their gravitational field can be fully described by two parameters: mass and spin. We cannot directly observe black holes as no light escapes from the event horizon. However, we can detect the light from accreting gas, which forms a dense disk around the black hole, known as an accretion disk. The accretion of material by a...
Accreting supermassive black holes, or active galactic nuclei (AGN), are known to grow behind clouds of gas and dust, obscuring their view.
In orientation unification models, unobscured ($20<\log(N_{\rm H}/{\rm cm}^{-2}<22$) and obscured ($22< \log(N_{\rm H}/{\rm cm}^{-2}<24$) AGN differ only by their viewing angle, while evolutionary models suggest that obscuration correspond to a specific...
Theoretical models and hydrodynamical simulations of AGN feedback predict that outflows developing in AGN host galaxies have a multiphase and multiscale nature and that some physical mechanisms must link the inner regions where the SMBH gravitational field dominates, to the larger scales, where its direct influence is negligible. This paradigm has been unambiguously confirmed by a plethora of...
The eRASS is expected to include tens of thousands of blazars. We present the initial results of an extensive search for blazars in both the eRASS1 and EFEDS surveys, primarily conducted at the Brera Observatory using the tools from the Firmamento online platform. We estimate the statistical properties of blazars, distinguishing between low and high energy peaked objects, as well as between...
Through its all-sky surveys, SRG/eROSITA has uncovered a large sample of X-ray transients associated with the nuclei of galaxies that show no signatures of prior AGN activity. A particular subclass is represented by tidal disruption events (TDEs), in which a flare of radiation is emitted as a star is ripped apart by wandering too close to a massive or supermassive black hole. Here, I will...
Period-bounce cataclysmic variables (CVs) are systems where a white dwarf accretes from a brown dwarf donor, having reached a point where the degeneracy of the donor reverses the orbit period evolution. A large portion of the CV population, between 40$\%$ and 70$\%$, is predicted to be made up of period-bouncers. However, due to their intrinsic faintness, only on the order of a dozen such...
We present a novel set of constrained cosmological simulations and zoom-in simulations of galaxy clusters in our Local Universe. These simulations accurately replicate the observed positions and masses of the galaxy clusters, as well as the correct X-ray derived profiles. Our work highlights the current predictions of these structures based on our simulated results, offering a detailed...
The formation and growth of Supermassive Black Holes (BHs) of mass MBH = 10^(6 - 10) Msun, have always challenged our understanding of modern astronomy. Indeed, some of these objects were already in place at very early cosmic times, which makes us wonder how they assembled so quickly, and what happens once they reach such high masses that early in the history of the Universe.
The focus of...
We report the detection of three simultaneous quasi-periodic oscillations (QPOs) at ∼ 40 Hz, ∼ 800 Hz, and ∼ 1100 Hz, along with a broad feature at ∼ 150 Hz from the AstroSat-LAXPC observation of NS-LMXB 4U 1728-34. For the very first time, we obtain thirteen sets of QPO triplets in time-resolved power density spectra for a particular observation. These QPO triplet frequencies are found to...
The four year eROSITA survey revealed over one million quasars. The quasar phase in galaxy evolution is thought to be essential in transforming their host galaxy. However, the triggers of quasars and their impact is still uncertain. We aim to map the environmental conditions favorable to the growth of black holes, in particular its complex dependence on host galaxy stellar mass,...
A direct approach to studying the galaxy-halo connection is the analysis of observed groups and clusters of galaxies that trace the underlying dark matter halos, making identifying galaxy clusters and their associated brightest cluster galaxies (BCGs) crucial. We test and propose a robust density-based clustering algorithm that outperforms the traditional Friends-of-Friends (FoF) algorithm in...
X-ray reprocessing serves as a vital diagnostic tool for gaining insights into the environments of X-ray binary systems. However, the study of X-ray reprocessing encounters challenges arising from the blending of intense primary radiation from the compact star with the reprocessed radiation from the surrounding. Eclipsing X-ray binaries offer a unique opportunity to investigate pure...
Despite many studies, superclusters, the largest structures in the cosmic web containing galaxy clusters on scales of tens to hundreds of megaparsecs (Mpc), remain enigmatic in their evolutionary processes. To shed light on this, we present a catalogue of 662 superclusters identified using a modified Friends-of-Friends algorithm applied to the WHL cluster catalogue within a redshift range of...
Active Galactic Nuclei (AGN) are powered by accretion of gas onto supermassive black holes. Persistently accreting AGNs, alongside inherent stochastic variability, sometimes display extreme flux and spectral changes (X-ray and/or optical fluxes), usually linked to significant variations in the global accretion rate. These drastic changes in the continuum flux are sometimes accompanied by...
Due to its high sensitivity in the soft X-ray band, eROSITA provides the perfect opportunity to study the diffuse X-ray emission of nearby galaxies. A Catalog of Neighboring Galaxies, presented by Karachentsev et al. (2013), was used to establish a sample of 72 nearby galaxies with distances $d \lesssim 17\,\mathrm{Mpc}$. For the 10 most luminous galaxies, the distribution and spectra were...
Thanks to their rapid rotation, millisecond pulsars are one of the most important sources to search for signatures of r-mode oscillations, which may be used to constrain the composition of neutron stars. This requires measurements or bounds on the surface temperatures of these faint objects. e-ROSITA, onboard Spektrum-Roentgen-Gamma satellite, recently completed the most detailed X-ray survey...
We present the preliminary results of our cross-correlation function (CCFs) measurements between eROSITA Final Equatorial-Depth Survey (eFEDS) AGNs and galaxies in the Galaxy And Mass Assembly (GAMA). The overlapped field covers ~60 deg$^2$, about half of the full eFEDS field. The X-ray sample is from our previous work (Comparat et al. 2023). The CCF enables us to measure the clustering...
An accurate mass calibration of galaxy clusters is a crucial step towards precise constraints on the cosmological parameters σ8 and Ωm from clusters. In the millimeter, via the Sunyaev-Zel’dovich (SZ) effect, and X-rays domains, cluster masses can be estimated assuming hydrostatic equilibrium, but several physical and observational effects can alter this calculation. One of those are...
In our project, we analyze the positions of X-ray selected AGNs on the
Baldwin-Phillips-Terlevich (BPT) diagram using eROSITA data. Previous
results from a sample of 1347 galaxies (z < 0.35) in SDSS DR17 revealed
a significant dependence of galaxy positions on the BPT diagram on the
X-ray/Hα flux ratio. Higher log(X-ray/Hα) values are associated with
Seyfert and LINER...
Mapping the distribution of baryonic mass in our Universe down to the group-sized halo masses it is essential to clarify how much baryonic matter is locked up in halos and in filaments. Non-gravitational processes affect the thermodynamical conditions of the hot gas and baryonic content of groups and clusters of galaxies, causing deviations from the theoretical self-similar expectations....
We study the angular distribution of the exponent $(\rm x)$ of the differential number counts $\rm n(S) = \big(\frac{\rm d^{2}N}{\rm dSd\Omega}\big)\propto \rm S^{-1-x}$, i.e., number of quasars per unit solid angle per unit flux density $(\rm S)$, employing the CatWISES2020 catalog. We find the dipole anisotropy in this parameter with dipole amplitude $0.005\pm0.002$ and direction points...
Context. Cosmological simulations indicate that half of the baryons in the nearby universe exist as warm-hot intergalactic medium (WHIM), and half of this WHIM gas resides in cosmic filaments that connect galaxy clusters. Accurate prescription of the filament gas is therefore essential for understanding the gravitational and baryonic processes that affect the assembly of the cosmic...
Detecting a supernova remnant (SNR) along the Galactic plane can be challenging. Any new detection reduces the discrepancy between the expected and known number of remnants.
We present results from a large selection of radio and X-ray data that cover the position of G321.3-3.9. We identified G321.3-3.9 as a new SNR using data collected by several radio surveys, spanning a frequency range...
Classical novae are known to demonstrate a supersoft X-ray source (SSS) state following outbursts. This state is associated with residual thermonuclear burning on the white dwarf (WD) surface. We performed a spectral analysis of the supersoft X-ray phase of the classical nova AT 2018bej, which was observed in X-rays by the eROSITA and XMM-Newton telescopes. To describe the spectrum we...
When measuring photon counts from incoming sky fluxes, X-ray observatories imprint nuisance effects on the data that must be accurately removed. Some detector effects can be easily inverted, while others are not trivially invertible such as the point spread function and shot noise. Using information field theory and Bayes' theorem, we infer the posterior mean and uncertainty for the sky flux....
The first eROSITA All-Sky Survey (eRASS-1) yielded a wealth of galaxy clusters across the sky. With the public release of this data in February 2024, the need for tools to automate and streamline large sample analysis became imperative. We present a sample of approximately 150 galaxy clusters detected by the Dark Energy Survey’s (DES) redMaPPer algorithm, eROSITA source detection, and in XMM...
Although flux variability is one of the fundamental properties of accretion flows onto supermassive black holes, its dependence on physical parameters such as the mass of the compact object and the Eddington ratio are still debated. In this contribution I will present new observational constraints on the Power Spectral Density (PSD) of the X-ray variability of Active Galactic Nuclei as a...
An open question in extragalactic astronomy is the extent to which Active Galactic Nuclei (AGN) affect the evolution of their host galaxies. Host galaxy properties of AGN, such as Star Formation Rate and Stellar Mass, are key parameters for studying the role of AGN in galaxy evolution.
However, disentangling the emission of AGN and star-forming components is a challenging task that...
The interstellar medium (ISM) is heated and ionized by radiation, by stellar winds, and finally, by supernova explosions. Since these processes are often correlated in space and time, they can form large interstellar structures called superbubbles, which are filled with hot thin plasma. If superbubbles expand and break, the hot plasma will escape into the galactic disk and also out of the...
Context. The spatial distribution of galaxy clusters provides a reliable tracer of the large-scale distribution of matter in the Universe.
The clustering signal depends on intrinsic cluster properties and cosmological parameters.
Aims. The ability of eROSITA on board Spectrum-Roentgen-Gamma (SRG) to discover galaxy clusters allows the association of
extended X-ray emission with dark matter...
The soft X-ray telescope eROSITA aboard the Spectrum-Roentgen-Gamma (SRG) mission is the first located in a halo orbit around the Sun-Earth L2 Lagrangian Point. With its main scientific goal to find 100000 clusters of galaxies for cosmological studies detailed knowledge of the background is crucial to be able to distiniguish faint extended objects from point-like sources and to determine...
In this work we will scrutinize the universality of the well-known non-linear relation between the UV and X-ray luminosity of AGNs. The LX-LUV correlation provides insights on the energy generating mechanisms and structural characteristics of AGNs, but it has also been proposed as a cosmological probe, under the assumption that it is redshift independent. However, recent works on the subject...
The formation and evolution of the first supermassive black holes have been put in the spotlight after the discovery of few hundreds extremely massive quasars at high redshift. An interesting twist in our understanding of the matter was introduced by the discovery of an unusual number of jetted sources: X-ray observations of blazars (i.e. AGN with jets aligned to our LoS) at z>4 prove that the...
Accreting compact binaries (ACB) are among the most luminous X-ray sources within the Galaxy. By incorporating machine learning techniques, we have identified roughly 11,000 potential ACB candidates in the eROSITA data sample. Optical spectroscopic observations are, however, now required to determine whether these candidates are true ACBs. For this project we are, therefore, conducting...
Evolutionary scenarios predict that obscured quasars play a key role in the evolution of galaxies; however, this role has not yet been fully understood since quasar samples are typically biased against obscured systems. We select and constrain the AGN and host galaxy properties of a complete and unbiased sample of ~600 infrared (IR) quasars ($L_{\rm AGN,IR}>10^{45} \rm \:erg\: s^{-1}$) at...
Active Galactic Nuclei (AGNs), found at the centers of galaxies, harbor supermassive black holes that emit immense energy across the electromagnetic spectrum. Traditionally, AGNs are classified based on factors like orientation (Type 1 vs. Type 2), radio emission (Radio-Loud vs. Radio-Quiet), or the presence of jets (Jetted vs. non-Jetted). However, these classifications may not fully capture...
AGN feedback is a key process in the evolution of massive systems in the Universe, and one for which new observational information is crucial for better implementation of numerical models. An image-manipulation technique capable of providing such information, X-arithmetic, is applied here to a sample of 15 galaxy clusters and groups deeply observed with Chandra. This technique decomposes...
Galaxy clusters, the largest gravitationally bound structures in the universe, provide astronomers with insights into the formation and evolution of large-scale structures through the study of their mergers. X-ray observations allow for direct analysis of the intracluster gas, revealing vital information such as temperature and entropy distribution, which aids in understanding the merging...
In this talk I will review recent and future (possible)
progress on time domain and multi-messenger astronomy from an X-ray
perspective.
In magnetic cataclysmic variables, X-ray emission is emitted from optically thin shock-heated plasma at the poles of the white dwarf. The X-ray emitting plasma has a continuous temperature distribution that can be reflected and/or reprocessing in the system before reaching the observer. The X-ray photons are reflected by the surface of the white dwarf, leading to a fluorescent iron K-alpha...
