Search

We investigated a scenario where the presence of a broad absorption line (BAL) feature in quasars (QSOs) is contingent upon the line of sight being situated within an outflow cone emanating from the source. We examined the mechanism of dust-driven winds based on the failed radiatively accelerated dusty outflow (FRADO) model proposed by Czerny & Hryniewicz, letting it be responsible for the formation of massive outflow. We calculated the probability of observing the BAL effect from the geometry of outflow which is a function of global parameters of black hole mass (M$_{BH}$), Eddington ratio ($\alpha_{Edd}$), and metallicity (Z). We then compared the results with prevalence of BAL QSOs in a sample of observational data from SDSS. The consistency of our model with the data supports the interpretation of the BAL phenomenon as a result of source orientation, rather than a transitory stage in AGN evolution, Comment: 5 pages, 3 plots, Submitted to the Proceedings of IAU Symposium 378: Black hole winds at all scales

We test the usefulness of the intermediate ionisation lines AlIII 1860 and CIII] 1909 as reliable virial mass estimators for quasars. We identify a sample of 309 quasars from the SDSS DR16 in the redshift range 1.2 < z < 1.4 to have [OII] 3728 recorded on the same spectrum of AlIII 1860, SiIII 1890, and CIII] 1909. We set the systemic quasar redshift using careful measurements of [OII]. We then classified the sources as Population A, extreme Population A (xA) and Population B, and analysed the 1900Å blend using multi-component models to look for systematic line shifts of the AlIII and CIII] along the quasar main sequence. We do not find significant shifts of the AlIII line peak in Pop. B and the wide majority of Pop. A. For Pop. xA, a small median blueshift of -250 km/s was observed, motivating a decomposition of the AlIII line profile into a virialized component centred at rest-frame and a blueshifted component for an outflow emission. For Pop. B objects, we proved the empirical necessity to fit a redshifted very broad component (VBC), clearly seen in CIII], and analysed the physical implications on a Pop. B composite spectrum using CLOUDY simulations. We find consistent black hole mass estimations using AlIII and CIII] as virial estimators for the bulk of Population A. AlIII (and even CIII]) is a reliable virial black hole mass estimator for Pop. A and B objects. xA sources deserve special attention due to the significant blueshifted excess observed in the line profile of AlIII, although not as large as those observed in CIV 1549., Accepted for publication in Astronomy and Astrophysics

Much effort has been done in order to better understand the active galactic nuclei mechanisms behind the relativistic jets observed in radio-loud sources. These phenomena are commonly seen in luminous objects with intermediate/high redshift such as quasars, so that the analysis of the spectroscopic properties of these sources may be a way to clarify this issue. Measurements are presented and contextualized taking advantage of the set of correlations associated with the quasar Main Sequence (MS), a parameter space that allows to connect observed properties to the relative relevance of radiative and gravitational forces. In the redshift range we consider, the low-ionization HI Balmer line H\b{eta} is shifted into the near infrared. Here we present first results of a sample of 22 high-luminosity quasars with redshift between 1.4 and 3.8. Observations covering the H\b{eta} spectral region were collected with the IR spectrometer ISAAC at ESO-VLT. Additional data were collected from SDSS in order to cover the UV region of our sources. The comparison between the strong C IV {\lambda}1549 high-ionization line and H\b{eta} in terms of line widths and shifts with respect to the rest-frame leads to an evaluation of the role of radiative forces in driving an accretion disk wind. While for non-jetted quasars the wind properties have been extensively characterized as a function of luminosity and other physical parameters, the situation is by far less clear for jetted sources. The overarching issue is the effect of the relativistic jets on the wind, and on the structure of the emitting region in general. We present results from our analysis of the optical and UV line profiles aimed to identifying the wind contribution to the line emission., Comment: 5 pages, 4 figures, based on talk presented at the XLIV SAB meeting

Nuclear Activity in Galaxies Across Cosmic Time, Proceedings of the conference held 7-11 October 2019 in Addis Ababa, Ethiopia. Edited by Mirjana Pović et al. Proceedings of the International Astronomical Union, Volume 356, Cambridge, UK: Cambridge University Press, 2021., Financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709)

Open Access.-Attribution 4.0 International (CC BY 4.0) The last 25 years saw a major step forward in the analysis of optical and UV spectroscopic data of large quasar samples. Multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. We discuss the empirical correlates of the so-called >main sequence> associated with the quasar Eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. We also briefly discuss quasars in a segment of the main sequence that includes the strongest FeII emitters. These sources show a small dispersion around a well-defined Eddington ratio value, a property which makes them potential Eddington standard candles.© Copyright © 2018 Marziani, Dultzin, Sulentic, Del Olmo, Negrete, Martínez-Aldama, D'Onofrio, Bon, Bon and Stirpe. AD and MM-A acknowledge financial support from the Spanish Ministry for Economy and Competitiveness through grants AYA2013-42227-P and AYA2016-76682-C3-1-P. DD and CN acknowledge support from grants PAPIIT108716, UNAM, and CONACyT221398. EB and NB acknowledge grants 176003 Gravitation and the large scale structure of the Universe and 176001 Astrophysical spectroscopy of extragalactic objects supported by the Ministry of Education and Science of the Republic of Serbia.

The most luminous quasars (with bolometric luminosities are 1E47 erg/s) show a high prevalence of CIV {\lambda}1549 and [OIII]{\lambda}{\lambda}4959,5007 emission line profiles with strong blueshifts. Blueshifts are interpreted as due to Doppler effect and selective obscuration, and indicate outflows occurring over a wide range of spatial scales. We found evidence in favor of the nuclear origin of the outflows diagnosed by [OIII]{\lambda}{\lambda} 4959,5007. The ionized gas mass, kinetic power, and mechanical thrust are extremely high, and suggest widespread feedback effects on the host galaxies of very luminous quasars, at cosmic epochs between 2 and 6 Gyr from the Big Bang. In this mini-review we summarize results obtained by our group and reported in several major papers in the last few years with an eye on challenging aspects of quantifying feedback effects in large samples of quasars., Comment: 10 pages, 2 figures. Contribution to the Proceedings of the meeting "Quasars at all cosmic epochs", held in Padova on April 2-7, 2017

Broad emission lines in quasars enable us to "resolve" structure and kinematics of the broad line emitting region (BLR) thought to in- volve an accretion disk feeding a supermassive black hole. Interpretation of broad line measures within the 4DE1 formalism simplifies the apparent confusion among such data by contrasting and unifying properties of so-called high and low accreting Population A and B sources. H�� serves as an estimator of black hole mass, Eddington ratio and source rest frame, the latter a valuable input for Civ��1549 studies which allow us to isolate the blueshifted wind component. Optical and HST-UV spectra yield H�� and Civ��1549 spectra for low-luminosity sources while VLT-ISAAC and FORS and TNG-LRS provide spectra for high Luminosity sources. New high S/N data for Civ in high-luminosity quasars are presented here for comparison with the other previously published data. Comparison of H�� and Civ��1549 profile widths/shifts indicates that much of the emission from the two lines arise in regions with different structure and kinematics. Covering a wide range of luminosity and redshift shows evidence for a correlation between Civ��1549 blueshift and source Eddington ratio, with a weaker trend with source luminosity (similar amplitude outflows are seen over 4 of the 5 dex luminosity range in our combined samples). At low luminosity (z < 0.7) only Population A sources show evidence for a significant outflow while at high luminosity the outflow signature begins to appear in Population B quasars as well., 18 pages, 11 figures

The most luminous quasars (with bolometric luminosities are 1E47 erg/s) show a high prevalence of CIV ��1549 and [OIII]����4959,5007 emission line profiles with strong blueshifts. Blueshifts are interpreted as due to Doppler effect and selective obscuration, and indicate outflows occurring over a wide range of spatial scales. We found evidence in favor of the nuclear origin of the outflows diagnosed by [OIII]���� 4959,5007. The ionized gas mass, kinetic power, and mechanical thrust are extremely high, and suggest widespread feedback effects on the host galaxies of very luminous quasars, at cosmic epochs between 2 and 6 Gyr from the Big Bang. In this mini-review we summarize results obtained by our group and reported in several major papers in the last few years with an eye on challenging aspects of quantifying feedback effects in large samples of quasars., 10 pages, 2 figures. Contribution to the Proceedings of the meeting "Quasars at all cosmic epochs", held in Padova on April 2-7, 2017

Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar ''main sequence'' with both extreme optical Fe II emission (RFe II ~ 1) and a large CIV λ1549 profile blueshift (~-1500 km s-1). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+year time-scale consistent with compact steep-spectrum (or young LD) over core-dominated morphology. In the 4DE1 context where LD RL are usually low L/LEdd quasars, we suggest that 3C 57 is an evolved RL quasar (i.e. large blackhole mass) undergoing a major accretion event leading to a rejuvenation reflected by strong Fe II emission, perhaps indicating significant heavy metal enrichment, high bolometric luminosity for a low-redshift source and resultant unusually high Eddington ratio giving rise to the atypical CIV λ1549.

While quasar outflows may be quasi-ubiquitous, there are significant differences on a source-by- source basis. These differences can be organized along the 4D Eigenvector 1 sequence: at least at low z, with only Population A sources radiating at relatively high Eddington ratio and showing prominent high-velocity outflows in Civ ��1549 line profiles. We discuss in this paper VLT-FORS observations of Civ ��1549 emission line profiles for a high-luminosity sample of Hamburg- ESO quasars and how they are affected by outflow motion as a function of quasar luminosity. Our high- luminosity sample has the notable advantage that the rest frame has been accurately determined from previous VLT-ISAAC observations of H�� in the J, H, and K bands. This makes measures of inter-line velocity shifts accurate and free of systemic biases. As the redshift increases and the luminosity of the brightest quasars increases, powerful, high-velocity outflows become more frequent. We discuss the outflow contextualisation, fol- lowing the 4DE1 formalism, as a tool for understanding the nature of the so-called weak lined quasars (WLQ) discovered in recent years as a new, poorly understood class of quasars. We estimate the kinetic power associ- ated with Civ ��1549 outflows and suggest that the host galaxies in the most luminous sources likely experience significant feedback., Accepted for publication in Astrophysics and Space Science

The empirical basis of quasar astronomy can be overawing especially in the twenty-first century. A first source of intricacy involves the nomenclature that has evolved to label the multifold phenomenological manifestations now united under the umbrella of active galactic nuclei (AGNs). A further complication involves observations of the many subclasses with the observations now spanning the electromagnetic spectrum.

Most of the questions in this chapter deal with sources that do not show the “classical” broad emission-line spectrum that characterizes the majority of known AGNs at high and low redshift. If that majority represents a “parent population” of AGNs, is the apparent absence of broad lines a result of obscuration, orientation, or different physical conditions? Can all of the subclasses be unified under the AGN umbrella? With the unification scheme set in place and assumed to be fundamentally correct, there are at least four overarching questions: do all type-2 AGNs possess an obscured broad-line region? Or how can we distinguishing type-2 AGNs without a broad-line region if they exist? Where is the low end of quasar activity? The least luminous AGNs are the so-called low-ionization nuclear emission-line regions (LINERs), but it is legitimate to ask if they are all true AGNs.

We present preliminary results from a pencil-beam spectroscopic survey of low-luminosity quasars at z ~ 2.2-2.5. Our goal is to compare these sources with low redshift analogues of similar luminosity. High s/n and moderate resolution spectra were obtained for 15 sources using the faint object spectrograph Osiris on the 10m Gran Telescopio Canarias. The new data make possible an almost unprecedented comparison between sources with the same (moderate) luminosity at widely different cosmic epochs. Preliminary analysis of our spectra confirms the presence of a relatively evolved population of quasars radiating at modest Eddington ratios. A notable difference between the low and high z quasars may involve the presence of lower metallicity quasars at high redshift., Accepted for publication in Advances in Space Research. Contributed talk presented at the 9th Serbian Conference on Spectral Line Shapes in Astrophysics (SCSLSA) held in Banja Koviliaca, on May 13-17, 2013. Minor corrections from previous version

We test the recent claim by Hu et al. (2008) that FeII emission in Type 1 AGN shows a systematic redshift relative to the local source rest frame and broad-line Hbeta. We compile high s/n median composites using SDSS spectra from both the Hu et al. sample and our own sample of the 469 brightest DR5 spectra. Our composites are generated in bins of FWHM Hbeta and FeII strength as defined in our 4D Eigenvector 1 (4DE1) formalism. We find no evidence for a systematic FeII redshift and consistency with previous assumptions that FeII shift and width (FWHM) follow Hbeta shift and FWHM in virtually all sources. This result is consistent with the hypothesis that FeII emission (quasi-ubiquitous in type 1 sources) arises from a broad-line region with geometry and kinematics the same as that producing the Balmer lines., Comment: 12 pages, 1 table, 1 figure - accepted for publication in ApJ Letters

[Abridged] We compare broad emission line profiles and estimate line ratios for all major emission lines between Ly-alpha and H-beta in a sample of six quasars. The sources were chosen with two criteria in mind: the existence of high quality optical and UV spectra as well as the possibility to sample the spectroscopic diversity in the 4D Eigenvector 1 context . In the latter sense each source occupies a region (bin) in the FWHM(H-beta) vs. optical FeII strength plane that is significantly different from the others. High S/N H-beta emission line profiles are used as templates for modeling the other lines (Ly-alpha, CIV 1549, HeII 1640, Al III 1860, Si III] 1892, and Mg II 2800). We can adequately model all broad lines assuming the existence of three components distinguished by blueshifted, unshifted and redshifted centroids (indicated as blue, broad and very broad component respectively). The broad component (high electron density, low ionization parameter; high column density) is present in almost all type-1 quasars and therefore corresponds most closely to the classical broad line emitting region (the reverberating component). The blue component emission (lower electron density; high ionization; low column density) arises in less optically thick gas; it is often thought to arise in an accretion disk wind. The least understood component involves the very broad component (high ionization and large column density). It is perhaps the most distinguishing characteristic of quasars with FWHM H-beta > 4000 km/s that belong to the so-called Population B of our 4DE1 space. Population A quasars (FWHM H-beta < 4000 km/s) are dominated by broad component emission in H-beta and blue component emission in CIV 1549 and other high ionization lines. 4DE1 appears to be the most useful current context for revealing and unifying spectral diversity in type-1 quasars., 7 Tables, 5 Figures; accepted for publication in Monthly Notices of the Royal Astronomical Society

We consider the properties of radio-loud (RL) AGN in the context of the Eigenvector 1 (E1) parameter space. RL sources show a restricted E1 parameter space occupation relative to the radio-quiet (RQ) majority. The Fanaroff-Riley II ``parent population'' of relatively un-boosted RL sources (median radio/optical flux ratio ~490) shows the most restricted occupation. RL sources have different broad line properties (and inferred black hole masses and Eddington ratios). FWHM H_beta for the broad line component in RL sources are at least twice as large as the RQ majority. The average broad FeII emission line strength is also about half that for RQ sources. Our sample suggests that the RL cutoff occurs near R_k=70 or logP(6cm)=32.0 ergs/s/Hz. Sources below this cutoff are RQ although we cannot rule out the existence of a distinct intermediate population. We show that the Doppler boosted core-dominated RL sources (median flux ratio ~1000) lie towards smaller FWHM(H_beta_bc) and stronger FeII in E1 as expected if the lines arise in an accretion disk. Our subsample of superluminal sources, with orientation inferred from the synchrotron self Compton model, reinforce this general E1 trend and allow us to estimate the role of source orientation in driving E1 domain occupation., 9 pages, 3 figures, accepted for publication in ApJL

We investigated the optical FeII emission in a sample of about 215 low-redshift AGN (quasars and luminous Seyfert 1 galaxies). We find that a scaled and broadened FeII template based on the I Zw 1 spectrum can satisfactorily model the FeII emission in almost all sources in our sample. We confirm that FWHM H$\beta$ and FeII$\lambda$4570 are strongly correlated. The correlation is different for sources with FWHM(H$\beta$) greater than or less than $\sim$4000 km s$^{-1}$. Sources with FWHM H$\beta$$\leq$ 4000 km s$^{-1}$ (Population A) show no difference between FWHM H$\beta$ and FeII while sources with FWHM(H$\beta$) $\geq$ 4000 km s$^{-1}$ (Population B) show FWHM FeII that is systematically smaller than FWHM H$\beta$. This may be telling us that FeII emission in Pop. B sources comes from only the outermost part of the H$\beta$\ emitting region where the degree of ionization is lowest., Comment: 4 pages, 4 figures. Poster presented at "AGN5: Inflows, Outflows and Reprocessing around Black Holes". Como, 11-14 June 2002. Also available at: www.unico.it/ilaria/AGN5/proceedings.html

We investigate the radial velocity difference between the [OIII]5007,4959 and H-beta lines for a sample of 200 low redshift AGN. We identify seven objects showing an [OIII]5007 blueshift relative to H-beta with amplitude larger than 250 km/s (blue "outliers"). These line shifts are found in sources where the broad high ionization lines (e.g. CIV1549) also show a large systematic blueshift. Such blueshifts occur only in the population A region of the Eigenvector 1 parameter domain (that also contains NLSy1 sources). We suggest that [OIII] blueshifts are also associated with the high ionization outflow originating in these sources. This is a direct kinematic linkage between narrow and broad line emitting gas., Comment: accepted for publication by ApJ Lett

We tested the ejector-propeller model of the Be/X-ray binary LSI+61303 (V 615 Cas, GT 0236+620) by using the parameters predicted by the model in the calculations of the X-ray and radio variability. The results are: (1) in terms of the Ejector-Propeller model, the X-ray maximum is due to the periastron passage; (2) the radio outburst can be really a result of the transition from the propeller to ejector regimes; (3) the radio outburst will delay with respect to the X-ray maximum every orbital period. The proposed scenario seems to be in good agreement with the observations., Comment: 9 pages, 4 figures, 2nd CNOC, "Astrophysics of Compact Objects" Sept. 19-21, 2001, Bologna, Italy

As a consequence of improved S/N, spectral resolution and wavelength coverage various authors have introduced, without strong justification, new emitting regions to account for various emission line profile differences in AGN. The so-called CIVlambda1549 intermediate line region (ILR) appears to be especially ill-defined. We present observational evidence that suggests the ILR is statistically indistinguishable from the classical narrow line region (NLR). We present the results of theoretical models showing that a smooth density gradient in the NLR can produce CIV and Balmer emission lines with different widths. The putative ILR component has often been included with the broad line profile in studies of CIV BLR properties. Failure to account for the composite nature of CIV emission, and for the presence of sometimes appreciable NLR CIV emission, has important consequences for our understanding of the BLR., 3 Figs. 1 Table, accepted for publication in Astrophysical Journal Letters

We examine the properties of the Fe emission lines that arise near 6.4 keV in the ASCA spectra of AGN. Our emphasis is on the Seyfert 1 galaxies where broad and apparently complex Fe K alpha emission is observed. We consider various origins for the line but focus on the pros and cons for line emitting accretion disk models. We develop a simple model of an illuminated disk capable of producing both X-ray and optical lines from a disk. The model is able to reproduce the observed Fe K alpha FWHM ratio as well as the radii of maximum emissivity implied by the profile redshifts. The overall profile shapes however do not fit well the predictions of our disk illumination model nor do we derive always consistent disk inclinations for the two lines. We conclude that the evidence for and against an accretion disk origin for the Fe K alpha emission is equal at best. The bulk of the data requires a very disparate set of line fits which shed little light on a coherent physical model. We briefly consider alternatives to disk emission models and show that a simple bicone model can reproduce the FE line profiles equally well., 29 pages, 6 tables, 6 figures. Submitted for publication in the Astrophysical Journal part I

We present spectroscopic observations of the quasar PG~1512+370, covering the Hbeta line spectral range and collected at moderate resolution (2-7 A FWHM) from 1988 to 1996. The observations show that the blue wing of the Hbeta broad profile component has changed significantly in flux and shape between 1988 and 1990 and between 1995 and 1996. A displaced blue peak on the Hbeta profile, visible in 1988, but not in the 1990-1995 spectra, is revealed again in one of the spectra obtained in 1996. The blue peak (in both the 1988 and 1996 spectra) is centered at Delta v_r ~ -3000 +/- 500 km/s from the rest frame defined by the narrow component of Hbeta, and the OIII lambda4959,5007 lines. We discuss several conflicting interpretations of the data. We find that the variability of the Hbeta blue wing is consistent with Balmer line emission from regions whose motion is predominantly radial, if variations of the blue wing are a response to continuum changes. Alternatively, we note that observed Hbeta line profile variations are consistent with a variable line component as in a ``binary black hole'' scenario. More frequent observations of Hbeta are needed to distinguish among these hypotheses., Comment: 19 pages, 1 embedded figure (eps), to appear in ApJ 495

We present new optical and infrared photometric observations and high resolution H$\alpha$ spectra of the periodic radio star \lsi. The optical photometric data set covers the time interval 1985-1993 and amounts to about a hundred nights. A period of $\sim$26 days is found in the V band. The infrared data also present evidence for a similar periodicity, but with higher amplitude of variation (0\rmag 2). The spectroscopic observations include 16 intermediate and high dispersion spectra of \lsi\ collected between January 1989 and February 1993. The H$\alpha$ emission line profile and its variations are analyzed. Several emission line parameters -- among them the H$\alpha$ EW and the width of the H$\alpha$ red hump -- change strongly at or close to radio maximum, and may exhibit periodic variability. We also observe a significant change in the peak separation. The H$\alpha$ profile of \lsi\ does not seem peculiar for a Be star. However, several of the observed variations of the H$\alpha$ profile can probably be associated with the presence of the compact, secondary star., Comment: 9 pages, LaTeX file. Figures available on request from josepmp@mizar.ub.es

We present new optical and infrared photometric observations and high resolution H α spectra of the periodic radio star LSI+61◦303. The optical photometric data set covers the time interval 1985-1993 and amounts to about a hundred nights. A period of ∼26 days is found in the V band. The infrared data also present evidence for a similar periodicity, but with higher amplitude of variation ((0.m 2). The spectroscopic observations include 16 intermediate and high dispersion spectra of LSI+61◦303 collected between January 1989 and February 1993. The H α emission line profile and its variations are analyzed. Several emission line parameters -- among them the H α EW and the width of the H α red hump -- change strongly at or close to radio maximum, and may exhibit periodic variability. We also observe a significant change in the peak separation. The H α profile of LSI+61◦303 does not seem peculiar for a Be star. However, several of the observed variations of the H α profile can probably be associated with the presence of the compact, secondary star.

We present new optical and infrared photometric observations and high resolution H$��$ spectra of the periodic radio star \lsi. The optical photometric data set covers the time interval 1985-1993 and amounts to about a hundred nights. A period of $\sim$26 days is found in the V band. The infrared data also present evidence for a similar periodicity, but with higher amplitude of variation (0\rmag 2). The spectroscopic observations include 16 intermediate and high dispersion spectra of \lsi\ collected between January 1989 and February 1993. The H$��$ emission line profile and its variations are analyzed. Several emission line parameters -- among them the H$��$ EW and the width of the H$��$ red hump -- change strongly at or close to radio maximum, and may exhibit periodic variability. We also observe a significant change in the peak separation. The H$��$ profile of \lsi\ does not seem peculiar for a Be star. However, several of the observed variations of the H$��$ profile can probably be associated with the presence of the compact, secondary star., 9 pages, LaTeX file. Figures available on request from josepmp@mizar.ub.es

UGC 3995 is a close pair of spiral galaxies whose eastern component hosts a Seyfert 2 nucleus. We present a detailed analysis of this system using long slit spectroscopy and narrow (\ha + \nii) as well as broad band (B, R) imaging and an archive WFPC2 image. The component galaxies reveal surprisingly small signs of interaction considering their spatial proximity and almost identical recession velocities, as the bright filament is probably an optical illusion due to the superposition of the bar of the Seyfert galaxy and of the spiral arms of the companion. The broad band morphology, a B--R color map, and a continuum-subtracted \ha + \nii image demonstrate that the western component UGC 3995B is in front of the Seyfert-hosting component UGC 3995A, partly obscuring its western side. The small radial velocity difference leaves the relative motion of the two galaxies largely unconstrained. The observed lack of major tidal deformations, along with some morphological peculiarities, suggests that the galaxies are proximate in space but may have recently approached each other on the plane of the sky. The geometry of the system and the radial velocity curve at P. A. = 106 suggest that the encounter may be retrograde or, alternatively, prograde before perigalacticon. The partial overlap of the two galaxies allows us to estimate the optical thickness of the disk of component B. We derive an extinction = 0.18 visual magnitudes in the infra-arms parts of the foreground galaxy disk, and >= 1-1.5 visual magnitudes in correspondence of the spiral arms., Accepted for publication in the Astronomical Journal (June 1999 issue)

We present BeppoSAX and XMM-Newton observations of MKN 231. These observations and in particular the BeppoSAX PDS data allowed us to unveil, for the first time, the highly absorbed (N$_H\sim 2\times10^{24}$ cm$^{-2}$) AGN component. We find that: a) the AGN powering MKN231 has an intrinsic 2-10 keV luminosity of $1^{+1}_{-0.5}\times 10^{44}$ erg/s; b) the strong starburst activity contributes significantly in the 0.1-10 keV energy range. We propose that the starburst activity strongly contributes to the far infrared luminosity of MKN 231; this is also suggested by the multiwavelength properties of MKN 231., Comment: 4 pages, 2 fugures, Proc. of the meeting: "The Restless High-Energy Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers Eds

Results from a spectroscopic study of the nuclear emission of a sample of 97 spirals in isolated galaxy pairs with mixed morphology (E+S) are presented and discussed. The Main results of this study are: (1) AGN activity is found in 40% of the spiral galaxies in these pairs, (2) Only one out of the 39 AGN found shows type 1 activity, and (3) AGN tend to have closer companions than star forming galaxies. These results are at odds with a simple Unified Model for Seyferts, where only obscuration/orientation effects are of relevance, and neatly support an evolutionary scenario where interactions trigger nuclear activity.

"Sulentic et al. (2007) defined the 4DE1, which is a four dimensions parameter space that uses optical, UV and X-ray measures to discriminate between different classes of AGN. Using new X-ray data from the satellite XMM-Newton, we present a way to visualize all the parameters in one 3D graph made by the open source software TOP CAT. The different correlations have been framed in the context of an evolutionary scheme and we make an interpretation of the underlying physics."

In this paper, we study the circumgalactic environment of LINER host galaxies, in a sample of 166 objects drawn from a Multifrequency Catalogue of LINERs by Carrillo et al. (1999). The aim of our work is to compare the environment of different types of LINERs, therefore we subdivided our sample in three groups: LINERs type 1, type 2, and transition objects (TL). The search has been carried out on the Digitized Sky Survey (DSS) up to a projected linear distance of 300 kpc using methods applied in several previous studies. We found that type 2 LINERs and TLs seem to possess a richer environment than those of type 1. In addition, type 2 LINERs and TLs show large companions with frequency similar to that of bright IRAS galaxies and Seyfert 2 host galaxies. We suggest that an evolutionary sequence from starbursting systems, to type 2 and eventually to type-1 AGN, may be appropriate for most AGN and may be independent of luminosity.

Improving our understanding of the nuclear properties of high-Eddington-ratio (λEdd) active galactic nuclei (AGN) is necessary since at this regime the radiation pressure is expected to affect the structure and efficiency of the accretion disc-corona system. This may cause departures from the typical nuclear properties of low-λEdd AGN, which have been largely studied so far. We present here the X-ray spectral analysis of 14 radio-quiet, λEdd ≳ 1 AGN at 0.4 ≤ z ≤ 0.75, observed with XMM-Newton. Optical/UV data from simultaneous Optical Monitor observations have also been considered. These quasars were selected to have relatively high values of black hole mass (MBH ∼ 108 − 8.5 M⊙) and bolometric luminosity (Lbol ∼ 1046 erg s−1) in order to complement previous studies of high-λEdd AGN at lower MBH and Lbol. We studied the relation between λEdd and other key X-ray spectral parameters, such as the photon index (Γ) of the power-law continuum, the X-ray bolometric correction (kbol, X), and the optical/UV-to-X-ray spectral index (αox). Our analysis reveals that, despite the homogeneous optical and supermassive black hole accretion properties, the X-ray properties of these high-λEdd AGN are quite heterogeneous. We indeed measured values of Γ between 1.3 and 2.5, at odds with the expectations based on previously reported Γ − λEdd relations, for which Γ ≥ 2 would be a ubiquitous hallmark of AGN with λEdd ∼ 1. Interestingly, we found that ∼30% of the sources are X-ray weak, with an X-ray emission about a factor of ∼10 − 80 fainter than that of typical AGN at similar UV luminosities. The X-ray weakness seems to be intrinsic and not due to the presence of absorption along the line of sight to the nucleus. This result may indicate that high-λEdd AGN commonly undergo periods of intrinsic X-ray weakness. Furthermore, results from follow-up monitoring with Swift of one of these X-ray weak sources suggest that these periods can last for several years. © ESO 2022., This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. Part of this work is based on archival data, software and online services provided by the Space Science Data Center – ASI. This work has been partially supported by the ASI-INAF program I/004/11/4. ML acknowledges financial support from the PhD programme in Astronomy, Astrophysics and Space Science supported by MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca). EP, LZ, FT, SB, AL and GV acknowledge financial support under ASI/INAF contract 2017-14-H.0. EP, SB, MB and GV acknowledge support from PRIN MIUR project “Black Hole winds and the Baryon Life Cycle of Galaxies: the stone-guest at the galaxy evolution supper”, contract #2017PH3WAT. AdO acknowledges financial support from the State Agency for Research of the Spanish MCIU through the project PID2019-106027GB-C41 and the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). RM acknowledges the financial support of INAF (Istituto Nazionale di Astrofisica), Osservatorio Astronomico di Roma, ASI (Agenzia Spaziale Italiana) under contract to INAF: ASI 2014-049-R.0 dedicated to SSDC. CR acknowledges support from the Fondecyt Iniciacion grant 11190831.

Flexible conductive composites based on ultra-high molecular weight polyethylene (UHMWPE) filled with multi-walled carbon nanotubes (CNTs) modified by perfluoropolyethers (PFPEs) were produced. The bonding of PFPE chains, added in 1:1 and 2:1 weight ratios, on CNTs influences the dispersion of nanotubes in the UHMWPE matrix due to the non-polar nature of the polymer, facilitating the formation of nanofillers-rich conductive pathways and improving composites’ electrical conductivity (two to five orders of magnitude more) in comparison to UHMWPE-based nanocomposites obtained with pristine CNTs. Electrochemical atomic force microscopy (EC-AFM) was used to evaluate the morphological changes during cyclic voltammetry (CV). The decrease of the overpotential for hydrogen oxidation peaks in samples containing PFPE-functionalized CNTs and hydrogen production (approximately −1.0 V vs. SHE) suggests that these samples could find application in fuel cell technology as well as in hydrogen storage devices. Carbon black-containing composites were prepared for comparative study with CNTs containing nanocomposites.

Editorial on the Research Topic Frontiers in astronomy and space sciences: Rising stars

We discuss XMM-Newton and BeppoSAX observations of MKN 231, the lowest-redshift Broad Absorption Line (BAL) QSO known so far and one of the best-studied Ultra Luminous Infrared Galaxies. By combining the XMM-Newton spectral resolution and the high-energy bandpass of BeppoSAX we have been able to study in more detail than previously possible its 0.2--50 keV spectral properties. The BeppoSAX PDS data unveiled, for the first time, a highly absorbed ($N_H\sim 2\times 10^{24}$cm$^{-2}$) power-law component. We find that: a) below 10 keV we are seeing only reprocessed radiation through reflection and/or scattering; b) the intrinsic 2-10 keV luminosity of MKN 231 is $1^{+1.0}_{-0.5} \times 10^{44}$ ergs s$^{-1}$, i.e. more than an order of magnitude greater than previous measurements; c) the starburst activity significantly contributes to the soft ($E, 11 pages,3 figures, Latex manuscript, Accepted for publication in Astronomy and Astrophysics

The Cofin 2000 project titled `Obscuration and reprocessing in the cosmic history of AGN' aims to study the physical and morphologic characteristics of the obscuring material in active galactic nuclei (AGN), and the cosmic history of the obscured AGN, to be compared with the history of unobscured AGN and with that of star formation. The project is in progress; as it is still too early to make a synthesis of the results, we will instead discuss separately the status of several different lines of research.