arXiv subjects

Paola Marziani

Publications and source records attributed to Paola Marziani.

At least 73 records · Page 4Linked to original sources

arXiv2018

AGN Broad Line Region variability in the context of Eigenvector 1: case of NGC 5548

Many active galactic nuclei (AGN) show strong variability of the optical continuum. Since the line flux, profile shapes and intensity ratios are changing, we analyze the variability patterns and possible periodicity of Type 1 AGN NGC 5548, using the Eigenvector 1 (EV1) diagram in different variability states, taking advantage of very long term monitoring campaign data. The preliminary results suggest that NGC 5548 - a highly variable object that over several decades has shown large amplitude continuum fluctuations and flaring behavior - remains Pop B. This means that the range in Eddington ratio, even when the source is in a bright state, remains consistent with the value of the low accreting Pop B. We inspected EV 1 parameters of a single object though long term monitoring, assuming an inclination and black hole mass to be constant during the observational time. Our results imply that the main driver for the variations along the EV 1 diagram could be dimensionless accretion rate. If so, then it appears that the source never crossed the boundary for structural changes, indicatively placed at $L/L_{Edd} \sim$ 0.2.

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arXiv2017

Phylogenetic Analyses of Quasars and Galaxies

Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z < 0.7) which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. Cladistics is not only able to group sources radiating at higher Eddington ratios, to separate radio-quiet (RQ) and radio-loud (RL) quasars and properly distinguishes core-dominated and lobe-dominated quasars, but it suggests a black hole mass threshold for powerful radio emission as already proposed elsewhere. An interesting interpretation from this work is that the phylogeny of quasars may be represented by the ontogeny of their central black hole, i.e. the increase of the black hole mass. However these exciting results are based on a small sample of low-z quasars, so that the work must be extended. We are here faced with two difficulties. The first one is the current lack of a larger sample with similar observables. The second one is the prohibitive computation time to perform a cladistic analysis on more that about one thousand objects. We show in this paper an experimental strategy on about 1500 galaxies to get around this difficulty. Even if it not related to the quasar study, it is interesting by itself and opens new pathways to generalize the quasar findings.

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arXiv2017

The phylogeny of quasars and the ontogeny of their central black holes

The connection between multifrequency quasar observational and physical parameters related to accretion processes is still open to debate. In the last 20 year, Eigenvector 1-based approaches developed since the early papers by Boroson and Green (1992) and Sulentic et al. (2000b) have been proven to be a remarkably powerful tool to investigate this issue, and have led to the definition of a quasar "main sequence". In this paper we perform a cladistic analysis on two samples of 215 and 85 low-z quasars (z 0.7) which were studied in several previous works and which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. The data encompass accurate measurements of observational parameters which represent key aspects associated with the structural diversity of quasars. Cladistics is able to group sources radiating at higher Eddington ratios, as well as to separate radio-quiet (RQ) and radio-loud (RL) quasars. The analysis suggests a black hole mass threshold for powerful radio emission and also properly distinguishes core-dominated and lobe-dominated quasars, in accordance with the basic tenet of RL unification schemes. Considering that black hole mass provides a sort of "arrow of time" of nuclear activity, a phylogenetic interpretation becomes possible if cladistic trees are rooted on black hole mass: the ontogeny of black holes is represented by their monotonic increase in mass. More massive radio-quiet Population B sources at low-z become a more evolved counterpart of Population A i.e., wind dominated sources to which the "local" Narrow-Line Seyfert 1s belong.

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arXiv2016

On the origin of the Fundamental Plane and Faber-Jackson relations: consequences for the star formation problem

The aim of this work is to show that the origin of the Fundamental Plane (FP) relation for early-type galaxies (ETGs) can be traced back to the existence of a fine-tuning between the average star formation rate $ $ of galaxies and their structural and dynamical characteristics. To get such result it is necessary to imagine the existence of two distinct "virtual planes" for each galaxy in the $\log(R_e)-\log(I_e)-\log(σ)$ space. The first one (named Virial Plane VP) represents the total galaxy mass using the scalar Virial Theorem and the mass-to-light ratio $M/L$, while the second plane comes from an expression of the total galaxy luminosity as a function of the mean star formation rate $ $ and the velocity dispersion $σ$, through a relation $L=L'_0 σ^{-2}$ (named here pseudo-Faber-Jackson (PFJ)) which is a mathematical convenient way for expressing the independency of light from the virial equilibrium. Its validity can be connected to the mutual correlation $L\simσ\sqrt{ }$ observed for all ETGs. A posteriori it is possible to see that this approach permits to explain the observed properties of the FP (tilt and scatter) and the Zone of Exclusions (ZOE) visible in the FP projections. Furthermore, the link between the properties of the FP and the SFR of galaxies provides a new idea of the star formation, as a phenomenon driven by the initial conditions of proto-galaxies and regulated across the whole cosmic history by the variation of the main galaxy parameters (mass, luminosity, structural shape and velocity dispersion).

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arXiv2016

The Extreme Ultraviolet Variability of Quasars

We study the extreme ultraviolet (EUV) variability (rest frame wavelengths 500 - 920 $Å$) of high luminosity quasars using HST (low to intermediate redshift sample) and SDSS (high redshift sample) archives. The combined HST and SDSS data indicates a much more pronounced variability when the sampling time between observations in the quasar rest frame is $> 2\times 10^{7}$ sec compared to $< 1.5\times 10^{7}$ sec. Based on an excess variance analysis, for time intervals $< 2\times 10^{7}$ sec in the quasar rest frame, $10\%$ of the quasars (4/40) show evidence of EUV variability. Similarly, for time intervals $>2\times 10^{7}$ sec in the quasar rest frame, $55\%$ of the quasars (21/38) show evidence of EUV variability. The propensity for variability does not show any statistically significant change between $2.5\times 10^{7}$ sec and $3.16\times 10^{7}$ sec (1 yr). The temporal behavior is one of a threshold time interval for significant variability as opposed to a gradual increase on these time scales. A threshold time scale can indicate a characteristic spatial dimension of the EUV region. We explore this concept in the context of the slim disk models of accretion. We find that for rapidly spinning black holes, the radial infall time to the plunge region of the optically thin surface layer of the slim disk that is responsible for the preponderance of the EUV flux emission (primarily within 0 - 7 black hole radii from the inner edge of the disk) is consistent with the empirically determined variability time scale.

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arXiv2016

The Extreme Ultraviolet Spectra of Low Redshift Radio Loud Quasars

This paper reports on the extreme ultraviolet (EUV) spectrum of three low redshift ($z \sim 0.6$) radio loud quasars, 3C 95, 3C 57 and PKS 0405-123. The spectra were obtained with the Cosmic Origins Spectrograph (COS) of the Hubble Space Telescope. The bolometric thermal emission, $L_{bol}$, associated with the accretion flow is a large fraction of the Eddington limit for all of these sources. We estimate the long term time averaged jet power, $\overline{Q}$, for the three sources. $\overline{Q}/L_{bol}$, is shown to lie along the correlation of $\overline{Q}/L_{bol}$ and $α_{EUV}$ found in previous studies of the EUV continuum of intermediate and high redshift quasars, where the EUV continuum flux density between 1100 Å\, and 700 Å\, is defined by $F_ν \sim ν^{-α_{EUV}}$. The high Eddington ratios of the three quasars extends the analysis into a wider parameter space. Selecting quasars with high Eddington ratios has accentuated the statistical significance of the partial correlation analysis of the data. Namely. the correlation of $\overline{Q}/L_{\mathrm{bol}}$ and $α_{EUV}$ is fundamental and the correlation of $\overline{Q}$ and $α_{EUV}$ is spurious at a very high statistical significance level (99.8\%). This supports the regulating role of ram pressure of the accretion flow in magnetically arrested accretion models of jet production. In the process of this study, we use multi-frequency and multi-resolution Very Large Array radio observations to determine that one of the bipolar jets in 3C 57 is likely frustrated by galactic gas that keeps the jet from propagating outside the host galaxy.

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arXiv2016

Gravitational Redshift of Emission Lines in the AGN Spectra

The detection of gravitationally redshifted optical emission lines has been reported just for a few active galaxies. In this paper we give a short overview of studies that analyzed or exploited the detection of the gravitational redshift in optical AGN spectra. In addition, we tested the consistency of gravitational redshift as the physical origin of the redward shifts observed in their spectra using a sample of $\approx$ 50 Hamburg-ESO intermediate to high redshift quasars that are among the most luminous quasars known ($10^{47} \lesssim L \lesssim 10^{48}$ erg/s), and are expected to host very massive black holes. To this aim we modeled the line profile with accretion disk models around a black hole.

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arXiv2015

The Extreme Ultraviolet Deficit - Jet Connection in the Quasar 1442+101

In previous studies, it has been shown that the long term time average jet power, $\overline{Q}$, is correlated with the spectral index in the extreme ultraviolet (EUV), $α_{EUV}$ (defined by $F_ν \sim ν^{-α_{EUV}}$ computed between 700Å\, and 1100Å\,). Larger $\overline{Q}$ tends to decrease the EUV emission. This is a curious relationship because it connects a long term average over $\sim 10^{6}$ years with an instantaneous measurement of the EUV. The EUV appears to be emitted adjacent to the central supermassive black hole and the most straightforward explanation of the correlation is that the EUV emitting region interacts in real time with the jet launching mechanism. Alternatively stated, the $\overline{Q}$ - $α_{EUV}$ correlation is a manifestation of a contemporaneous (real time) jet power, $Q(t)$, correlation with $α_{EUV}$. In order to explore this possibility, this paper considers the time variability of the strong radio jet of the quasar 1442+101 that is not aberrated by strong Doppler enhancement. This high redshift (z = 3.55) quasar is uniquely suited for this endeavor as the EUV is redshifted into the optical observing window allowing for convenient monitoring. More importantly, it is bright enough to be seen through the Lyman forest and its radio flux is strong enough that it has been monitored frequently. Quasi-simultaneous monitoring (five epochs spanning $\sim 40$ years) show that increases in $Q(t)$ correspond to decreases in the EUV as expected.

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arXiv2015

The transformation of Spirals into S0 galaxies in the cluster environment

We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04 < z < 0.07) and EDisCS (0.4 < z < 0.8). The most important results are: 1) the average number of S0 galaxies in clusters is almost a factor of $\sim 3 - 4$ larger today than at redshift $z \sim 1$; 2) the fraction of S0's to Spirals increases on average by a factor $\sim$ 2 every Gyr; 3) the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web) is: $\sim$ 5 Sp into S0's per Gyr and $\sim$ 2 Sp into E's per Gyr; 4) there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; 5) there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: 1) the ratio between the number of S0's and Spirals (NS0/NSp) in the WINGS clusters is correlated with their X-ray luminosity $L_X$ ; 2) that the brightest and massive S0's are always close to the cluster center; 3) that the mean Sersic index of S0's is always larger than that of Spirals (and lower than E's) for galaxy stellar masses above $10^9.5$ Msun; 4) that the number of E's in clusters cannot be constant; 5) that the largest difference between the mean mass of S0's and E's with respect to Spirals is observed in clusters with low velocity dispersion. Finally, by comparing the properties of the various morphological types for galaxies in clusters and in the field, we find that the most significant effect of the environment is the stripping of the outer galaxy regions, resulting in a systematic difference in effective radius and Sersic index.

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arXiv2015

The Extreme Ultraviolet Spectrum of the Kinetically Dominated Quasar 3C 270.1

Only a handful of quasars have been identified as kinetically dominated, their long term time averaged jet power, $\overline{Q}$, exceeds the bolometric thermal emission, $L_{bol}$, associated with the accretion flow. This letter presents the first extreme ultraviolet (EUV) spectrum of a kinetically dominated quasar, 3C 270.1. The EUV continuum flux density of 3C 270.1 is very steep, $F_ν \sim ν^{-α_{EUV}}$, $α_{EUV} =2.98\pm 0.15$. This value is consistent with the correlation of $\overline{Q}/L_{bol}$ and $α_{EUV}$ found in previous studies of the EUV continuum of quasars, the EUV deficit of radio loud quasars. Curiously, although ultraviolet broad absorption line (BAL) troughs in quasar spectra are anti-correlated with $\overline{Q}$, 3C 270.1 has been considered a BAL quasar based on an SDSS spectrum. This claim is examined in terms of the EUV spectrum of OVI 1and the highest resolution CIV spectrum in the archival data and the SDSS spectrum. First, from [OIII]4959,5007 (IR) observations and the UV spectral lines, it is concluded that the correct redshift for 3C 270.1 is 1.5266. It is then found that the standard measure of broad absorption, BALnicity = 0, for MgII 2800, CIV 1549 and OVI 1032 in all epochs.

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arXiv2015

Quasars in the 4D Eigenvector 1 Context: A stroll down memory lane

Recently some pessimism has been expressed about our lack of progress in understanding quasars over the 50+ year since their discovery. It is worthwhile to look back at some of the progress that has been made - but still lies under the radar - perhaps because few people are working on optical/UV spectroscopy in this field. Great advances in understanding quasar phenomenology have emerged using eigenvector techniques. The 4D eigenvector 1 context provides a surrogate H-R Diagram for quasars with a source main sequence driven by Eddington ratio convolved with line-of-sight orientation. Appreciating the striking differences between quasars at opposite ends of the main sequence (so-called population A and B sources) opens the door towards a unified model of quasar physics, geometry and kinematics. We present a review of some of the progress that has been made over the past 15 years, and point out unsolved issues.

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arXiv2015

OI and CaII observations in intermediate redshift quasars

We present an unprecedented spectroscopic survey of the CaII triplet + OI for a sample of 14 luminous ($-$26 $\gtrsim$ M$_V$ $\gtrsim$ $-$29), intermediate redshift (0.85 $\lesssim$ $z$ $\lesssim$ 1.65) quasars. The ISAAC spectrometer at ESO VLT allowed us to cover the CaII NIR spectral region redshifted into the H and K windows. We describe in detail our data analysis which enabled us to detect CaII triplet emission in all 14 sources (with the possible exception of HE0048-2804) and to retrieve accurate line widths and fluxes of the triplet and OI $λ$8446. The new measurements show trends consistent with previous lower $z$ observations, indicating that CaII and optical FeII emission are probably closely related. The ratio between the CaII triplet and the optical FeII blend at $λ$4570 $Å$ is apparently systematically larger in our intermediate redshift sample relative to a low-$z$ control sample. Even if this result needs a larger sample for adequate interpretation, higher CaII/optical FeII should be associated with recent episodes of star formation in the intermediate redshift quasars and, at least in part, explain an apparent correlation of CaII triplet equivalent width with $z$ and $L$. The CaII triplet measures yield significant constraints on the emitting region density and ionization parameter, implying CaII triplet emission from log n$_H$ $\gtrsim$ 11 [cm$^{-3}$] and ionization parameter log $U$ $\lesssim$ 1.5. Line width and intensity ratios suggest properties consistent with emission from the outer part of a high density broad line region (a line emitting accretion disk?).

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arXiv2014

Low- and high-z highly accreting quasars in the 4D Eigenvector 1 context

Highly accreting quasars are characterized by distinguishing properties in the 4D eigenvector 1 parameter space that make them easily recognizable over a broad range range of redshift and luminosity. The 4D eigenvector 1 approach allows us to define selection criteria that go beyond the restriction to Narrow Line Seyfert 1s identified at low redshift. These criteria are probably able to isolate sources with a defined physical structure i.e., a geometrically thick, optically thick advection-dominated accretion disk (a "slim" disk). We stress that the importance of highly accreting quasars goes beyond the understanding of the details of their physics: their Eddington ratio is expected to saturate toward values of order unity, making them possible cosmological probes.

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arXiv2014

GTC Spectra of z ~ 2.3 Quasars: Comparison with Local Luminosity Analogues

[Abridged] Context: The advent of 8-10m class telescopes makes possible for the first time detailed comparison of quasars with similar luminosity and very different redshifts. Aims: A search for z-dependent gradients in line emission diagnostics and derived physical properties by comparing, in a narrow bolometric luminosity range (log L ~ 46.1 +/- 0.4 [\ergss]), some of the most luminous local (z < 0.6) quasars with some of the lowest luminosity sources yet found at redshift z = 2.1 ~ 2.5. Method: Spectra for 22 high z sources were obtained with the 10.4m Gran Telescopio Canarias (GTC) while the HST (largely FOS) archive provides a low redshift control sample. Comparison is made in the context of the 4D Eigenvector 1 formalism meaning that we divide both source samples into high accreting Population A and low accreting Population B sources. Results: CIV 1549 shows very similar properties at both redshifts confirming at high redshift the CIV profile differences between Pop. A and B that are well established in local quasars. The CIV blueshift that appears quasi- ubiquitous in higher L sources is found in only half (Pop. A) of quasars observed in both of our samples. A CIV evolutionary Baldwin effect is certainly disfavored. We find evidence for lower metallicity in the GTC sample that may point toward a gradient with z. No evidence for a gradient in black hole mass or Eddington ratio is found. Conclusions: Spectroscopic differences established at low redshift are also present in much higher redshift quasars. Given that our samples involve sources with very similar luminosity the evidence for a systematic metallicity decrease, if real, points toward an evolutionary effect. Our samples appear representative of a slow evolving quasar population likely present at all redshifts.

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arXiv2014

Highly Accreting Quasars: Sample Definition and Possible Cosmological Implications

We propose a method to identify quasars radiating closest to the Eddington limit, defining primary and secondary selection criteria in the optical, UV and X-ray spectral range based on the 4D eigenvector 1 formalism. We then show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Using preliminary samples of these sources in three redshift intervals (as well as two mock samples), we test a range of cosmological models. Results are consistent with concordance cosmology but the data are insufficient for deriving strong constraints. Mock samples indicate that application of the method proposed in this paper using dedicated observations would allow to set stringent limits on Omega_M and significant constraints on Omega_Lambda.

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arXiv2013

Low ionization lines in high luminosity quasars: The calcium triplet

In order to investigate where and how low ionization lines are emitted in quasars we are studying a new collection of spectra of the CaII triplet at $λ$8498, $λ$8542, $λ$8662 observed with the Very Large Telescope (VLT) using the Infrared Spectrometer And Array Camera (ISAAC). Our sample involves luminous quasars at intermediate redshift for which CaII observations are almost nonexistent. We fit the CaII triplet and the OI $λ$8446 line using the H$β$ profile as a model. We derive constraints on the line emitting region from the relative strength of the CaII triplet, OI $λ$8446 and H$β$.

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arXiv2013

Low Ionization Emission Lines in Quasars: Clues from OI 8446 and the CaII Triplet

The formation of low emission lines in quasars and active galactic nuclei is still an open issue. Aided by the organizing power of the 4D eigenvector 1 scheme, we review basic developments since the 1980s, devoting special attention to the CaII IR triplet and the OI 8446 emission lines. Coverage of these lines is cumbersome since they are shifted in an inconvenient IR domain already at modest redshifts (~ 0.2). Their detection is also difficult since they are faint and often buried in the Ca II absorption of the host galaxy. We discuss how these lines can provide unambiguous constraints on the physical conditions of the broad line emitting regions of quasars when detected in emission, and summarise preliminary results for a sample of luminous, intermediate redshift quasars.

astro-ph.CO↗

arXiv2013

Techniques for Profile Binning and Analysis of Eigenvector Composite Spectra: Comparing Hbeta and MgII 2800 as Virial Estimators

We review the basic techniques for extracting information about quasar structure and kinematics from the broad emission lines in quasars. We consider which lines can most effectively serve as virial estimators of black hole mass. At low redshift the Balmer lines,particularly broad H beta, are the lines of choice. For redshifts greater than 0.7 - 0.8 one can follow H beta into the IR windows or find an H beta surrogate. We explain why UV CIV 1549 is not a safe virial estimator and how MgII 2800 serves as the best virial surrogate for H beta up to the highest redshift quasar known at z ~ 7. We show how spectral binning in a parameter space context (4DE1) makes possible a more effective comparison of H beta and MgII. It also helps to derive more accurate mass estimates from appropriately binned spectra and, finally, to map the dispersion in black hole mass and Eddington ratio across the quasar population. FWHM MgII is about 20% smaller than FWHM H beta in the majority of type 1 AGN requiring correction when comparing black hole mass estimates from these two lines. The 20% of sources showing narrowest FWHM H beta (< 4000 km/s) and strongest FeII (R_FeII >~ 1.0) emission (we call them bin A3-4 sources) do not show this FWHM difference and a blueshift detected in MgII for these sources suggests that FWHM H beta is the safer virial estimator for these extreme Eddington emitters.

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