C. Vignali - Univ. Bologna

C. Vignali
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Name
C. Vignali
Affiliation
Univ. Bologna
City
Bologna
Country
Italy

Pubs By Year

Pub Categories

 
Astrophysics of Galaxies (43)
 
High Energy Astrophysical Phenomena (19)
 
Cosmology and Nongalactic Astrophysics (9)
 
Instrumentation and Methods for Astrophysics (2)

Publications Authored By C. Vignali

We present a coherent multi-band modelling of the CO Spectral Energy Distribution of the local Seyfert Galaxy NGC7130 to assess the impact of the AGN activity on the molecular gas. We take advantage of all the available data from X-ray to the sub-mm, including ALMA data. The high-resolution (~0. Read More

We investigate the star formation properties of a large sample of ~2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z~3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analysis of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. Read More

We present a systematic analysis of X-ray archival data of all the 29 quasars (QSOs) at $z$ > 5.5 observed so far with Chandra, XMM-Newton and Swift-XRT, including the most-distant quasar ever discovered, ULAS J1120+0641 ($z$ = 7.08). Read More

We investigate the dependence of black-hole accretion rate (BHAR) on host-galaxy star formation rate (SFR) and stellar mass ($M_*$) in the CANDELS/GOODS-South field in the redshift range of $0.5\leq z < 2.0$. Read More

We report the virial measurements of the BH mass of a sample of 17 type 2 AGN, drawn from the Swift/BAT 70-month 14-195 keV hard X-ray catalogue, where a faint BLR component has been measured via deep NIR (0.8-2.5 $\mu$m) spectroscopy. Read More

We study the spectrophotometric properties of a highly magnified (\mu~40-70) pair of stellar systems identified at z=3.2222 behind the Hubble Frontier Field galaxy cluster MACS~J0416. Five multiple images (out of six) have been spectroscopically confirmed by means of VLT/MUSE and VLT/X-Shooter observations. Read More

We present a detailed spectral analysis of the brightest Active Galactic Nuclei (AGN) identified in the 7Ms Chandra Deep Field-South (CDF-S) survey over a time span of 16 years. Using a model of an intrinsically absorbed power-law plus reflection, with a possible soft excess and narrow Fe K\alpha line, we perform a systematic X-ray spectral analysis, both on the total 7Ms exposure and in four different periods with lengths of 2-21 months. With this approach, we not only present the power-law slopes, column densities N_H, observed fluxes, and intrinsic (absorption-corrected) rest-frame 2-10 keV luminosities L_X for our sample of AGNs, but also identify significant spectral variabilities among them on time scales of a few years. Read More

The coeval AGN and galaxy evolution and the observed local relations between SMBHs and galaxy properties suggest some connection or feedback between SMBH growth and galaxy build-up. We looked for correlations between properties of X-ray detected AGN and their FIR detected host galaxies, to find quantitative evidences for this connection, highly debated in the latest years. We exploit the rich multi-wavelength data set available in the COSMOS field for a large sample (692 sources) of AGN and their hosts, in the redshift range $0. Read More

Misaligned AGN (MAGNs), i.e., radio-loud AGNs with the jet not pointing directly towards us, represent a new class of GeV emitters revealed by the Fermi space telescope. Read More

We report on the detection of a remarkable new fast high-energy transient found in the Chandra Deep Field-South, robustly associated with a faint ($m_{\rm R}=27.5$ mag, $z_{\rm ph}$$\sim$2.2) host in the CANDELS survey. Read More

Models and observations suggest that both power and effects of AGN feedback should be maximised in hyper-luminous (L_Bol>10^47 erg/s) quasars, i.e. objects at the brightest end of the AGN luminosity function. Read More

The Chandra Deep Field South (CDF-S) was observed by XMM-Newton for a total of about 3 Ms in many periods over the past decade (2001-2002 and 2008-2009). The main goal of the survey was to obtain good quality X-ray spectroscopy of the AGN responsible for the bulk of the X-ray background. We will present the scientific highlights of the XMM-Newton survey and briefly discuss the perspectives of future observations to pursue XMM deep survey science with current and forthcoming X-ray facilities. Read More

We present X-ray source catalogs for the $\approx7$ Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2 arcmin$^2$. Utilizing WAVDETECT for initial source detection and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0. Read More

In this paper we present an overview of the MAGNA (Multiple AGN Activity) project aiming at a comprehensive study of multiple supemassive black hole systems. With the main goal to characterize the sources in merging systems at different stages of evolution, we selected a sample of objects optically classified as multiple systems on the basis of emission line diagnostics and started a massive multiband observational campaign. Here we report on the discovery of the exceptionally high AGN density compact group SDSS~J0959+1259. Read More

We present medium resolution near infrared spectroscopic observations of 41 obscured and intermediate class AGN (type 2, 1.9 and 1.8; AGN2) with redshift $z \lesssim$0. Read More

2016Oct

The XXL survey currently covers two 25 sq. deg. patches with XMM observations of ~10ks. Read More

We present the measurement of the projected and redshift space 2-point correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy AGN at 2.9$\leq$z$\leq$5.5 ($\langle L_{bol} \rangle \sim$10$^{46}$ erg/s) using the generalized clustering estimator based on phot-z probability distribution functions (Pdfs) in addition to any available spec-z. Read More

We perform long-term ($\approx 15$ yr, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms $Chandra$ Deep Field-South (CDF-S) survey; the majority are in the redshift range of $0.6-3.1$, providing access to penetrating rest-frame X-rays up to $\approx 10-30$ keV. Read More

We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. 38% of the sources are optically classified Type 1 active galactic nuclei (AGN), 60% are Type 2 AGN and 2% are passive, low-redshift galaxies. Read More

We exploit the 7 Ms \textit{Chandra} observations in the \chandra\,Deep Field-South (\mbox{CDF-S}), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from 2076 galaxies at $3.5\leq z < 6.5$. Read More

Matter flows in the central regions of quasars during their active phases are probably responsible for the properties of the super-massive black holes and that of the bulges of host galaxies. To understand how this mechanism works, we need to characterize the geometry and the physical state of the accreting matter at cosmological redshifts. The few high quality X-ray spectra of distant QSO have been collected by adding sparse pointings of single objects obtained during X-ray monitoring campaigns. Read More

We present the properties of X-ray detected dust obscured galaxies (DOGs) in the Chandra Deep Field South. In recent years, it has been proposed that a significant percentage of the elusive Compton-thick (CT) active galactic nuclei (AGN) could be hidden among DOGs. In a previous work, we presented the properties of X-ray detected DOGs by making use of the deepest X-ray observations available at that time, the 2Ms observations of the Chandra deep fields. Read More

In the last decade, using single epoch virial based techniques in the optical band, it has been possible to measure the central black hole mass on large AGN1 samples. However these measurements use the width of the broad line region as a proxy of the virial velocities and are therefore difficult to be carried out on those obscured (type 2) or low luminosity AGN where the nuclear component does not dominate in the optical. Here we present the optical and near infrared spectrum of the starburst/Seyfert galaxy NGC 6221, observed with X-shooter/VLT. Read More

We present the discovery of a giant $\gtrsim$100~kpc Ly$\alpha$ nebula detected in the core of the X-ray emitting cluster CL~J1449+0856 at $z=1.99$ through Keck/LRIS narrow-band imaging. This detection extends the known relation between Ly$\alpha$ nebulae and overdense regions of the Universe to the dense core of a $5-7\times10^{13}$ M$_{\odot}$ cluster. Read More

We present measurements of the evolution of normal-galaxy X-ray emission from $z \approx$ 0-7 using local galaxies and galaxy samples in the 6 Ms Chandra Deep Field-South (CDF-S) survey. The majority of the CDF-S galaxies are observed at rest-frame energies above 2 keV, where the emission is expected to be dominated by X-ray binary (XRB) populations; however, hot gas is expected to provide small contributions to the observed- frame < 1 keV emission at $z < 1$. We show that a single scaling relation between X-ray luminosity ($L_{\rm X}$) and star-formation rate (SFR) is insufficient for characterizing the average X-ray emission at all redshifts. Read More

PG1247+267 is one of the most luminous known quasars at $z\sim2$ and is a strongly super-Eddington accreting SMBH candidate. We obtained NuSTAR data of this intriguing source in December 2014 with the aim of studying its high-energy emission, leveraging the broad band covered by the new NuSTAR and the archival XMM-Newton data. Several measurements are in agreement with the super-Eddington scenario for PG1247+267: the soft power law ($\Gamma=2. Read More

X-ray extragalactic surveys are ideal laboratories for the study of the evolution and clustering of active galactic nuclei (AGN). The XXL Survey spans two fields of a combined 50 $deg^2$ observed for more than 6Ms with XMM-Newton, occupying the parameter space between deep surveys and very wide area surveys; at the same time it benefits from a wealth of ancillary data. This paper marks the first release of the XXL point source catalogue selected in the 2-10 keV energy band with limiting flux $F_{2-10keV}=4. Read More

We present new estimates of AGN accretion and star-formation luminosity in galaxies obtained for the local 12-$\mu$m sample of Seyfert galaxies (12MGS), by performing a detailed broad-band spectral energy distribution (SED) decomposition including the emission of stars, dust heated by star formation and a possible AGN dusty torus. Thanks to the availability of data from the X-rays to the sub-millimetre, we constrain and test the contribution of the stellar, AGN and star-formation components to the SEDs. The availability of Spitzer-IRS low resolution mid-infrared (mid-IR) spectra is crucial to constrain the dusty torus component at its peak wavelengths. Read More

Star-forming galaxies are considered to be the leading candidate sources that dominate the cosmic reionization at z>7, and the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently a active line of research. We have observed a star-forming galaxy at z=3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730-890A rest-frame, and detect LyC emission. Read More

The XMM-LSS, XMM-COSMOS, and XMM-CDFS surveys are complementary in terms of sky coverage and depth. Together, they form a clean sample with the least possible variance in instrument effective areas and PSF. Therefore this is one of the best samples available to determine the 2-10 keV luminosity function of AGN and its evolution. Read More

We present the XXL Survey, the largest XMM programme totaling some 6.9 Ms to date and involving an international consortium of roughly 100 members. The XXL Survey covers two extragalactic areas of 25 deg2 each at a point-source sensitivity of ~ 5E-15 erg/sec/cm2 in the [0. Read More

We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 square degrees of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. Read More

We derive the CO luminosity function (LF) for different rotational transitions (i.e. (1-0), (3-2), (5-4)) starting from the Herschel LF by Gruppioni et al. Read More

2015Sep
Affiliations: 1Dipartimento di Fisica e Astronomia, Bologna, 2ICREA and ICC, Universitat de Barcelona, 3INAF-Osservatorio Astronomico di Bologna, 4INAF-Osservatorio Astronomico di Bologna, 5INAF-Osservatorio Astronomico di Bologna, 6Institute for Astronomy & Astrophysics, National Observatory of Athens, 7INAF-Osservatorio Astronomico di Bologna, 8ESO, Garching, 9Institute for Astronomy & Astrophysics, National Observatory of Athens, 10Instituto de Fisica de Cantabria, Santander, 11Sterrenkundig Observatorium, Universiteit Gent, 12Dipartimento di Fisica e Astronomia, Bologna, 13Department of Astronomy & Astrophysics, The Pennsylvania State University, 14Instituto de Astrofisica, Pontificia Universidad Catolica de Chile, 15INAF-Osservatorio Astronomico di Roma, Monteporzio, Roma, 16Department of Astronomy, University of Maryland

In active galactic nuclei (AGN)-galaxy co-evolution models, AGN winds and outflows are often invoked to explain why super-massive black holes and galaxies stop growing efficiently at a certain phase of their lives. They are commonly referred to as the leading actors of feedback processes. Evidence of ultra-fast (v>0. Read More

2015Sep
Affiliations: 1INAF-OABrera, Italy, 2INAF-OABrera, Italy, 3INAF-OABrera, Italy, 4INAF-OABrera, Italy, 5INAF-OABrera, Italy, 6INAF-OABrera, Italy, 7INAF-OABrera, Italy, 8Universita' di Bologna, Italy

In this paper we present the results obtained with a monitoring programme (23 days long) performed with Swift-XRT on the local Seyfert galaxy Mrk 915. The light-curve analysis shows a significant count rate variation (about a factor of 2-3) on a time-scale of a few days, while the X-ray colours show a change in the spectral curvature below 2 keV and the presence of two main spectral states. From the spectral analysis we find that the observed variations can be explained by the change of the intrinsic nuclear power (about a factor of 1. Read More

We present a spectral and imaging analysis of the XMM-Newton and Chandra observations of the Seyfert 2 galaxy ESO138-G001, with the aim of characterizing the circumnuclear material responsible for the soft (0.3-2.0 keV) and hard (5-10 keV) X-ray emission. Read More

[Abridged] We investigate the physical properties of a Lyman continuum emitter candidate at $z=3.212$ with photometric coverage from $U$ to MIPS 24$\mu$m band and VIMOS/VLT and MOSFIRE/Keck spectroscopy. Investigation of the UV spectrum confirms a direct spectroscopic detection of the Lyman continuum emission with $S/N>5$. Read More

We present a multi-wavelength study of a newly discovered compact group (CG), SDSS J0959+1259, based data from XMM-Newton, SDSS and the Calar Alto optical imager BUSCA. With a maximum velocity offset of 500 km s$^{-1}$, a mean redshift of 0.035, and a mean spatial extension of 480 kpc, this CG is exceptional in having the highest concentration of nuclear activity in the local Universe, established with a sensitivity limit L$_{X}>4\times $10$^{40}$ erg s$^{-1}$ in 2--10 keV band and R-band magnitude $M_R < -19$. Read More

2015Jun
Affiliations: 1INAF-OABrera, Italy, 2INAF-OABrera, Italy, 3INAF-OABrera, Italy, 4INAF-OABrera, Italy, 5INAF-OABrera, Italy, 6INAF-OABrera, Italy, 7Universita' degli Studi di Bologna, Italy

Galaxy merging is widely accepted to be a key driving factor in galaxy formation and evolution, while the feedback from AGN is thought to regulate the BH-bulge coevolution and the star formation process. In this context, we focused on 1SXPSJ050819.8+172149, a local (z=0. Read More

The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z<1, the X-ray spectra can only be reliably characterized using broad-band measurements which extend to energies above 10 keV. Using the hard X-ray observatory NuSTAR, along with archival Chandra and XMM-Newton data, we study the broad-band X-ray spectra of nine optically selected (from the SDSS), candidate Compton-thick (NH > 1. Read More

2015May
Affiliations: 1INAF-OABrera, Italy, 2INAF-OABrera, Italy, 3INAF-OABrera, Italy, 4INAF-OABrera, Italy, 5INAF-OABrera, Italy, 6INAF-OABrera, Italy, 7INAF-OABrera, Italy, 8INAF-OABrera, Italy, 9Universita' degli Studi di Bologna, Italy

One of the key ingredients of the Unified Model of Active Galactic Nuclei (AGN) is the presence of a torus-like optically thick medium composed by dust and gas around the putative supermassive black hole. However, the structure, size and composition of this circumnuclear medium are still matter of debate. To this end, the search for column density variations through X-ray monitoring on different timescales (months, weeks and few days) is fundamental to constrain size, kinematics and location of the X-ray absorber(s). Read More

2015May
Affiliations: 1CEA - Saclay, 2CEA - Saclay, 3CEA - Saclay, 4CEA - Saclay, 5CEA - Saclay, 6CEA - Saclay, 7CEA - Saclay, 8CEA - Saclay, 9Institute for Astronomy, ETH Zuric, 10Aix Marseille Université, CNRS, LAM, 11Department of Physics, University of Surrey, 12Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna

When the cosmic star formation history peaks (z ~ 2), galaxies vigorously fed by cosmic reservoirs are gas dominated and contain massive star-forming clumps, thought to form by violent gravitational instabilities in highly turbulent gas-rich disks. However, a clump formation event has not been witnessed yet, and it is debated whether clumps survive energetic feedback from young stars, thus migrating inwards to form galaxy bulges. Here we report spatially resolved spectroscopy of a bright off-nuclear emission line region in a galaxy at z = 1. Read More

Highly obscured active galactic nuclei (AGN) are common in nearby galaxies, but are difficult to observe beyond the local Universe, where they are expected to significantly contribute to the black hole accretion rate density. Furthermore, Compton-thick (CT) absorbers (NH>10^24 cm^-2) suppress even the hard X-ray (2-10 keV) AGN nuclear emission, and therefore the column density distribution above 10^24 cm^-2 is largely unknown. We present the identification and multi-wavelength properties of a heavily obscured (NH>~10^25 cm^-2), intrinsically luminous (L(2-10keV)>10^44 erg s^-1) AGN at z=0. Read More

The ionising continuum from active galactic nuclei (AGN) is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. Furthermore, it provides hints on how matter accretes onto supermassive black holes. Using HST's Wide Field Camera 3 we have constructed the first stacked ultraviolet (rest-frame wavelengths 600-2500\AA) spectrum of 53 luminous quasars at z=2. Read More

We construct the rest-frame 2--10 keV intrinsic X-ray luminosity function of Active Galactic Nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field-South. We use ~3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of the XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. Read More