arXiv subjects

Jack W. Sulentic

Publications and source records attributed to Jack W. Sulentic.

At least 19 recordsLinked to original sources

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

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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arXiv2013

Quasars and their emission lines as cosmological probes

Quasars are the most luminous sources in the Universe. They are currently observed out to redshift z ~ 7 when the Universe was less than one tenth of its present age. Since their discovery 50 years ago astronomers have dreamed of using them as standard candles. Unfortunately quasars cover a very large range (8 dex) of luminosity making them far from standard. We briefly review several methods that can potentially exploit quasars properties and allow us to obtain useful constraints on principal cosmological parameters. Using our 4D Eigenvector 1 formalism we have found a way to effectively isolate quasars radiating near the Eddington limit. If the Eddington ratio is known, under several assumptions it is possible to derive distance independent luminosities. We discuss and the main statistical and systematic errors involved, and whether these "standard Eddington candles" can be actually used to constrain cosmological models.

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arXiv2013

Is Mg II 2800 a Reliable Virial Broadening Estimator for Quasars?

[Abridged] Broad MgII 2800 and Hbeta lines have emerged as the most reliable virial estimators of black hole mass in quasars. Which is more reliable? Comparison of MgII 2800 and Hbeta profile measures in the same sources and especially FWHM measures that provide the virial broadening estimator. Identification of 680 bright Sloan Digital Sky Survey DataRelease 7 quasars with spectra showing both MgII 2800 and Hbeta lines, at redshift 0.4 < z < 0.75. The s/n of these spectra are high enough to allow binning in the "four-dimensional (4D) eigenvector 1'' optical plane and construction of high s/n composite spectra. We confirm that MgII 2800 shows a profile that is ~ 20% narrower as suggested in some previous studies. FWHM measures for Population B sources (i.e., with FWHM of Hbeta larger than 4000 km/s) are uncertain because they show complex profiles with at least two broad-line components involving a nearly unshifted broad and redshifted very-broad component. Only the broad component is likely to be a valid virial estimator. If Hbeta and MgII 2800 are not corrected for the very broad component then black hole mass values for Population B sources will be systematically overestimated by up to logM ~ 0.3-0.4 dex. We suggest a simple correction that can be applied to the majority of sources. MgII 2800 is the safer virial estimator for Population B sources because the centroid shifts with respect to rest frame are lower than for Hbeta. In the broad and very broad component profile interpretation this is a consequence of the lower very broad to broad component intensity ratio for MgII 2800. Effective discrimination of black hole mass and Eddington ratio at fixed redshift is not achieved via luminosity binning but rather by binning in a "4D eigenvector 1'' context that reflects different broad line region geometry/kinematics likely driven by Eddington ratio.

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arXiv2012

Quasar Outflows in the 4D Eigenvector 1 Context

Gas outflows appear to be a phenomenon shared by the vast majority of quasars. Observations indicate that there is wide range in outflow prominence. In this paper we review how the 4D eigenvector 1 scheme helps to organize observed properties and lead to meaningful constraints on the outflow physical and dynamical processes.

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arXiv2011

Estimating Black Hole Masses in Quasars Using Broad Optical and UV Emission Lines

We review past work using broad emission lines as virial estimators of black hole masses in quasars. Basically one requires estimates of the emitting region radius and virial velocity dispersion to obtain black hole masses. The three major ways to estimate the broad-line emitting region (BLR) radius involve: (1) direct reverberation mapping, (2) derivation of BLR radius for larger samples using the radius-luminosity correlation derived from reverberation measures, and (3) estimates of BLR radius using the definition of the ionization parameter solved for BLR radius (photoionization method). At low redshift (z < 0.7) FWHM H-beta serves as the most widely used estimator of virial velocity dispersion. FWHM H-beta can provide estimates for tens of thousands of quasars out to z ~ 3.8 (IR spectroscopy beyond z ~ 1). A new photoionization method also shows promise for providing many reasonable estimates of BLR radius via high S/N IR spectroscopy of the UV region 1300 -- 2000 A. FWHM MgII 2800 can serve as a surrogate for FWHM H-beta in the range 0.4 < z < 6.5 while CIV 1549 is affected by broadening due to non-virial motions and best avoided (i.e. there is no clear conversion factor between FWHM H-beta and FWHM CIV 1549). Most quasars yield black hole mass estimates in the range 7 < log M< 9.7. There is no strong evidence for values above 10.0 and there may be evidence for a turnover in the maximum black hole mass near z ~ 5.

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arXiv2008

New Insights on the QSO Radio-Loud/Radio-Quiet Dichotomy: SDSS Spectra in the Context of the 4D Eigenvector1 Parameter Space

We search fora dichotomy/bimodality between Radio Loud (RL) and Radio Quiet (RQ) Type 1 Active Galactic Nuclei (AGN). We examine several samples of SDSS QSOs with high S/N optical spectra and matching FIRST/NVSS radio observations. We use the radio data to identify the weakest RL sources with FRII structure to define a RL/RQ boundary which corresponds to log L$_{1.4GHz}$=31.6 ergs s$^{-1}$ Hz$^{-1}$. We measure properties of broad line H$β$ and FeII emission to define the optical plane of a 4DE1 spectroscopic diagnostic space. The RL quasars occupy a much more restricted domain in this optical plane compared to the RQ sources, which a 2D Kolmogorov-Smirnov test finds to be highly significant. This tells us that the range of BLR kinematics and structure for RL sources is more restricted than for the RQ QSOs, which supports the notion of dichotomy. FRII and CD RL sources also show significant 4DE1 domain differences that likely reflect differences in line of sight orientation (inclined vs. face-on respectively) for these two classes. The possibility of a distinct Radio Intermediate (RI) population between RQ and RL source is disfavored because a 4DE1 diagnostic space comparison shows no difference between RI and RQ sources. We show that searches for dichotomy in radio vs. bolometric luminosity diagrams will yield ambiguous results mainly because in a reasonably complete sample the radio brightest RQ sources will be numerous enough to blur the gap between RQ and RL sources. Within resolution constraints of NVSS and FIRST we find no FRI sources among the broad line quasar population.

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arXiv2007

Our Search for an H-R Diagram of Quasars

The 4D Eigenvector 1 parameter space was introduced seven years ago as an attempt at multiwavelength spectroscopic representation of quasars. It appears to be the most effective diagnostic space for unifying the diversity of broad line AGN. This progress report shows that the diagnostic power of 4DE1 is confirmed using optical spectra from the SDSS, UV spectra from HST and X-ray spectra from XMM. Our introduction of the population A-B concept continues to provide useful insights into quasar diversity. Largely radio-quiet, high accreting, low BH mass Pop. A sources (FWHM H_beta <= 4000 km/s) show strong FeII emission, a soft X-ray excess and a CIV profile blueshift. Low accreting large BH mass Pop. B quasars (FWHM H_beta > 4000 km/s) include most radio-loud AGN and show weak FeII emission and little evidence for a soft X-ray excess or a CIV blueshift.

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arXiv2007

CIV 1549 as an Eigenvector 1 Parameter for Active Galactic Nuclei

[Abridged] We have been exploring a spectroscopic unification for all known types of broad line emitting AGN. The 4D Eigenvector 1 (4DE1) parameter space shows promise as a unification capable of organizing quasar diversity on a sequence primarily governed by Eddington ratio. This paper considers the role of CIV 1549 measures with special emphasis on the CIV 1549 line shift as a principal 4DE1 diagnostic. We use HST archival spectra for 130 sources with S/N high enough to permit reliable CIV 1549 broad component (BC) measures. We find a CIV 1549 BC profile blueshift that is strongly concentrated among (largely radio-quiet: RQ) sources with FWHM(H beta BC) < 4000 km/s (which we call Population A). Narrow line Seyfert 1 (NLSy1, with FWHM H beta < 2000 km/s) sources belong to this population but do not emerge as a distinct class. The systematic blueshift, widely interpreted as arising in a disk wind/outflow, is not observed in broader lined AGN which we call Population B. We find new correlations between FWHM(CIV 1549 BC) and CIV 1549 line shift as well as the equivalent width of CIV 1549. They are seen only in Pop. A sources. CIV 1549 measures enhance the apparent dichotomy at FWHM(Hbeta BC) approx. 4000 \kms\ (Sulentic et al. 2000) suggesting that it has more significance in the context of Broad Line Region structure than the more commonly discussed RL vs. RQ dichotomy. Black hole masses computed from FWHM CIV 1549 BC for about 80 AGN indicate that the CIV 1549 width is a poor virial estimator. Comparison of mass estimates derived from Hbeta BC and CIV 1549 reveals that the latter show different and nonlinear offsets for population A and B sources. A significant number of sources also show narrow line CIV 1549 emission. We present a recipe for CIV 1549 narrow component extraction.

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arXiv2006

Accretion onto Supermassive Black Holes in Quasars: Learning from Optical/UV Observations

Accretion processes in quasars and active galactic nuclei are still poorly understood, especially as far as the connection between observed spectral properties and physical parameters is concerned. Quasars show an additional degree of complexity compared to stars that is related to anisotropic emission/obscuration influencing the observed properties in most spectral ranges. This complicating factor has hampered efforts to define the equivalent of an Hertzsprung-Russel diagram for quasars. Even if it has recently become possible to estimate black hole mass and Eddington ratio for sources using optical and UV broad emission lines, the results are still plagued by large uncertainties. Nevertheless, robust trends are emerging from multivariate analysis of large spectral datasets of quasars. A firm observational basis is being laid out by accurate measurements of broad emission line properties especially when the source rest-frame is known. We consider the most widely discussed correlations (i.e. the so-called "eigenvector 1 parameter space" and the "Baldwin effect") and analyze how they can be explained in terms of accretion properties, broad line region structure, and source evolution. We critically review recent estimates of black hole mass, accretion rate, spin and possible orientation indicators, stressing that any improvement in these parameters will provide a much better understanding of the physics and dynamics of the region producing the optical and UV broad emission lines. More accurate measurements of Eddington ratio and black hole mass may have a significant impact on our ideas about evolution of quasar properties with redshift and luminosity as well as on broader cosmological issues.

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arXiv2005

Mixed Morphology Pairs as a Breeding Ground for Active Nuclei

Mixed morphology pairs offer a simplification of the interaction equation that involves a gas-rich fast rotator paired with a gas-poor slow rotator. In past low resolution IRAS studies it was assumed that the bulk of the far infrared emission originated in the spiral component. However our ISO studies revealed a surprising number of early-type components with significant IR emission some of which turned out to show active nuclei. This motivated us to look at the current statistics of active nuclei in mixed pairs using the FIR-radio continuum correlation as a diagnostic. We find a clear excess of early-type components with radio continuum emission and an active nucleus. We suggest that they arise more often in mixed pairs via cross fueling of gas from the spiral companion. This fuel is more efficiently channeled into the nucleus of the slow rotating receptor. In a sample of 112 mixed-morphology pairs from the Karachentsev catalog we find that about 25-30% of detected mixed pairs show a displacement from the radio-FIR relation defined by normal star forming galaxies. The latter objects show excess radio continuum emission while others extend the relation to unusually high radio and FIR flux levels. Many of the outliers/extreme emitters involve an early-type component with an active nucleus. The paired E/S0 galaxies in the sample exhibit a significant excess detection fraction and a marginal excess luminosity distribution compared to isolated unpaired E/S0 galaxies.

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arXiv2003

Searching For the Physical Drivers of Eigenvector 1: Influence of Black Hole Mass and Eddington Ratio

[Abridged] We compute the virial mass of the central black hole (M) and the luminosity-to-mass (L/M) ratio of ~ 300 low-z quasars and luminous Seyfert 1 nuclei. We analyze: (1) whether radio-quiet and radio-loud objects show systematic differences in terms of M and L/M; (2) the influence of M and L/M on the shape of the H-beta broad component line profile; (3) the significance of the so-called "blue outliers" i.e., sources showing a significant blueshift of the [OIII] 4959, 5007 lines with respect to the narrow component of H-beta which is used as an estimator of the quasar reference frame. We show that M and L/M distributions for RQ and RL sources are likely different for samples matched in luminosity and redshift. Line profile comparisons for median spectra computed over narrow ranges of M and L/M indicate that a Lorentz function provides a better fit for higher L/M sources and a double Gaussian for lower L/M values. A second (redshifted) Gaussian component at low L/M appears as a red asymmetry frequently observed in radio-loud and radio-quiet sources with broader (FWHM > 4000 km/s) H-beta broad component profiles. This component becomes stronger in larger mass and lower L/M sources. No specific influence of radio loudness on the H-beta broad component profile is detected, although equivalent widths of H-beta broad component and especially of [OIII] 4959,5007 are larger for radio-loud sources. We identify five more "blue outlier" sources. Since these sources are, on average, one magnitude brighter than other AGNs with similar mass, they are accreting at an Eddington ratio that is 2-3 times higher. We hint at evolutionary effects that explain some of these results and reinforce the "Eigenvector 1" correlations.

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arXiv2001

A Multiwavelength Study of Stephan's Quintet

Stephan's Quintet (SQ) is a compact group that we find in an atypical moment when a high velocity intruder is passing through it. The intrusion is particularly interesting because a previous intruder had stripped most of the gas from the group members. This debris field was shocked in the ongoing collision with the new intruder. This evolutionary history agrees well with observations and explains how a strongly interacting system can show low levels of star formation. We present new multiwavelength data including previously unpublished ROSAT X-ray, Ha interference filter/FP, ISO MIR/FIR and radio line and continuum images. These observations and previously published data provide new insights as well as support for some previous hypotheses. 1) FP and HI velocities allow us to unambiguously distinguish between gas associated with SQ and the new intruder. 2) Most detected emission regions are found in the remnant ISM of the NI which allows us to infer its size and present physical state. 3) The few emission regions associated with the stripped ISM of SQ include the best candidate tidal dwarf galaxy. 4) Multiwavelength data suggest that strong MIR/FIR emission from the Seyfert 2 nucleus of NGC7319 comes from dust heated directly by a power-law continuum rather than a starburst. 5) The correspondance between extended X-ray/radio continuum/forbidden optical emission confirms the existence of a large scale shock in SQ.

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