A5036252956- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- History and Developments in Astronomy
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Geophysics and Gravity Measurements
- Laser-Plasma Interactions and Diagnostics
- CCD and CMOS Imaging Sensors
- Black Holes and Theoretical Physics
- Photocathodes and Microchannel Plates
- Particle Detector Development and Performance
- Mechanics and Biomechanics Studies
- Radio Astronomy Observations and Technology
- Magnetic confinement fusion research
- Statistical and numerical algorithms
- Statistics Education and Methodologies
- Particle accelerators and beam dynamics
Arcetri Astrophysical Observatory
2021-2025
Istituto Nazionale di Fisica Nucleare, Sezione di Roma I
2025
University of Florence
2020-2024
University of California, Los Angeles
2023-2024
National Institute for Astrophysics
2021-2022
We present a new catalogue of ∼2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM–Newton . The sample can be used to investigate the non-linear relation between ultraviolet (UV) luminosity as well build Hubble diagram up redshift z ∼ 7.5. sources that are neither reddened by dust in optical UV nor obscured gas X-rays, whose fluxes free flux-limit-related biases. After checking for any possible systematics, we confirm, agreement our...
ABSTRACT We analyse some open debates in cosmology light of the most updated quasar (QSO) sample, covering a wide redshift range up to $\mathit{ z}$ ∼ 7.5, combined with type Ia supernovae (SNe) and baryon acoustic oscillations (BAOs). Indeed, extending cosmological analyses high-redshift data is key distinguishing between different models that are degenerate at low redshifts, allowing better constraints on possible dark energy (DE) evolution. Also, we discuss combinations BAO, SNe, QSO...
Cosmography is a powerful tool to investigate the Universe kinematic and then reconstruct dynamics in model-independent way. However, recent new measurements of supernovae Ia quasars have populated Hubble diagram up high redshifts ($z \sim 7.5$) application traditional cosmographic approach has become less straightforward due large implied. Here we this issue through an expansion luminosity distance-redshift relation terms "orthogonal" logarithmic polynomials. In particular point out...
Abstract We fit the UV/optical lightcurves of Seyfert 1 galaxy Mrk 817 to produce maps accretion disk temperature fluctuations δ T resolved in time and radius. The are dominated by coherent radial structures that move slowly ( v ≪ c ) inward outward, which conflicts with idea variability is driven only reverberation. Instead, these slow-moving likely due intrinsic disk. test how modifying input smoothing subtracting them changes resulting find most exist over relatively long timescales...
Abstract We investigate the X-ray properties of a sample 71 broad line and narrow AGN at 2<z<11 discovered by JWST in GOODS fields, which have deepest Chandra observations ever obtained. Despite widespread presence signatures their rest-optical -UV spectra, vast majority them is undetected. The stacked data non-detected sources also results non-detection. upper limit on emission for many these one or even two orders magnitude lower than expected from standard SED. absorption...
A fundamental ingredient in the unified model of active galactic nuclei (AGN) is obscuring torus, whose innermost, hottest region dominates near infrared (NIR) emission. Characterising change torus properties and its interplay with primary AGN emission key for our understanding physics, evolution, classification. Its covering factor (CF) largely responsible classification on basis detection broad lines. It still not clear whether evolve over time how they relate accretion parameters nucleus....
The non-linear relation between the X-ray and ultraviolet (UV) luminosity in quasars has been used to derive quasar distances build a Hubble diagram at redshifts up z ∼ 7. This cosmological application is based on assumption of independence redshift luminosity. We want test reliability this hypothesis by studying spectroscopic properties high-redshift UV bands. performed one-by-one analysis sample 130 > 2.5 with high-quality observations. found that not only does correlation still hold...
Context. A non-linear relation between quasar monochromatic luminosities at 2500 Å and 2 keV holds all observed redshifts luminosities, it has been used to derive distances build a Hubble diagram of quasars. The choice the X-ray UV indicators so far somewhat arbitrary typically relied on photometric data. Aims. We aim determine proxies that provide smallest dispersion in order obtain more precise distance estimates confirm reliability X-ray-to-UV as indicator. Methods. performed complete...
We present the analysis of rest frame ultraviolet and optical spectra 30 bright blue quasars at z ∼ 3, selected to examine suitability active galactic nuclei as cosmological probes. In our previous works, based on pointed XMM-Newton observations, we found an unexpectedly high fraction (≈25%) X-ray weak in sample. The latter sources also display a flatter UV continuum broader fainter C IV profile archival data with respect their normal counterparts. Here new observations Large Binocular...
Abstract We present the results of XMM-Newton and NuSTAR observations taken as part ongoing, intensive multiwavelength monitoring program Seyfert 1 galaxy Mrk 817 by AGN Space Telescope Optical Reverberation Mapping 2 (AGN STORM 2) Project. The campaign revealed an unexpected transient obscuring outflow, never before seen in this source. Of our four XMM-Newton/NuSTAR epochs, one fortuitously during a bright X-ray state has strong narrow absorption lines high-resolution grating spectra. From...
The 500ks Chandra ACIS-I observation of the field around $z=6.31$ quasar SDSS J1030+0524 is currently 5th deepest extragalactic X-ray survey. rich multi-band coverage allowed for an effective identification and redshift determination source counterparts: to date a catalog 243 sources with either spectroscopic or photometric estimate in range $z\approx0-6$ available over 355 arcmin$^2$ area. Given its depth information, this excellent resource investigate spectral properties distant Active...
We analyse the properties of CIV broad emission line in connection with X-ray 30 bright SDSS quasars at z~3.0-3.3 pointed XMM-Newton observations, which were selected to test suitability AGN as cosmological tools. In our previous work, we found that a large fraction (~25%) this sample are underluminous by factors >3-10. As absorbing columns >10$^{23}$ cm$^{-2}$ can be safely ruled out, their weakness is most likely intrinsic. Here explore possible correlations between UV and features these...
The recent extension of the Hubble diagram supernovae and quasars to redshifts much higher than 1 prompted a revived interest in nonparametric approaches test cosmological models measure expansion rate Universe. In particular, it is great infer model-independent constraints on possible evolution dark energy component. Here we present new method, based neural network regression, analyze completely nonparametric, fashion. We first validated method through simulated samples with same redshift...
In the past few years, we built a Hubble diagram of quasars up to redshift z$\sim$7, based on nonlinear relation between quasars' x-ray and UV luminosities. Such shows >4$\sigma$ deviation from standard flat $\Lambda$CDM model at z>1.5. Given important consequences this result, it is fundamental rule out any systematic effect in selection sample and/or flux measurements, investigate possible dependences relation, that would invalidate use as candles. Here review all observational results...
We present the analysis of rest frame ultraviolet and optical spectra 30 bright blue quasars at $z\sim3$, selected to examine suitability AGN as cosmological probes. In our previous works, we found an unexpectedly high fraction ($\approx 25 \%$) X-ray weak in sample. The latter sources also display a flatter UV continuum broader fainter CIV profile archival data with respect their normal counterparts. Here new observations LBT both $zJ$ (rest-frame $\simeq$2300-3100 $\rm \mathring{A}$) $K_S$...
We analyse some open debates in cosmology light of the most updated quasar (QSO) sample, covering a wide redshift range up to $z\sim7.5$, combined with type Ia supernovae (SNe) and baryon acoustic oscillations (BAO). Indeed, extending cosmological analyses high-redshift data is key distinguishing between different models that are degenerate at low redshifts, allowing better constraints on possible dark energy (DE) evolution. Also, we discuss combinations BAO, SNe, QSO understand their...
Proceeding of the "HACK100" Conference, 6-10 June 2022, Trieste, Italy - In recent years, quasars have been shown to be reliable standardizable candles, thanks non-linear relation between their X-rays and ultraviolet luminosity. Quasars are also very numerous they found at all observed redshifts: this allows us investigate expansion rate Universe cosmological parameters in a previously almost untested redshift range ($z\sim2-7$). At higher than 1.5, Hubble Diagram shows significant tension...
A sample of quasars has been recently assembled to investigate the non-linear relation between their monochromatic luminosities at 2500{\AA}, and 2 keV exploit as a new class standardized candles. The use this technique for cosmological purposes relies on non-evolution with redshift UV-optical spectral properties quasars, well absence possible contaminants such dust extinction host-galaxy contribution. We address these issues by analysing our quasar sample. produced composite spectra in...
A characteristic feature of quasars is the observed non-linear relationship between their monochromatic luminosities at rest-frame 2500 Å and 2 keV. This evident across all redshifts and, due to its non-linearity, can be implemented estimate quasar distances construct a Hubble Diagram for quasars. Historically, significant challenge in cosmological application this relation has been high dispersion. Recent studies have demonstrated that dispersion reduced by excluding biased objects from...
A sample of quasars has been recently assembled to investigate the non-linear relation between their monochromatic luminosities at 2500 Å and 2 keV exploit as a new class ‘standardized candles’. The use this technique for cosmological purposes relies on non-evolution with redshift UV-optical spectral properties quasars, well absence possible contaminants such dust extinction host galaxy contribution. We address these issues by analysing our quasar sample. produced composite spectra in...
We present the results of XMM-Newton and NuSTAR observations taken as part ongoing, intensive multi-wavelength monitoring program Seyfert 1 galaxy Mrk 817 by AGN Space Telescope Optical Reverberation Mapping 2 (AGN STORM 2) Project. The campaign revealed an unexpected transient obscuring outflow, never before seen in this source. Of our four XMM-Newton/NuSTAR epochs, one fortuitously during a bright X-ray state has strong narrow absorption lines high-resolution grating spectra. From these...
A fundamental ingredient in the unified model of active galactic nuclei (AGN) is obscuring torus, whose innermost, hottest region dominates near infrared (NIR) emission. Characterising change torus properties and its interplay with main AGN emission key for our understanding physics, evolution classification. Its covering factor ($CF$) largely responsible classification on basis detection broad lines. It still not clear whether evolve over time how they relate accretion parameters nucleus....