A New Method to Obtain the Broad Line Region Size of High Redshift Quasars

Negrete, C. A.; Dultzin, D.; Marziani, Paola; Sulentic, J. W.

doi:10.1088/0004-637x/794/1/95

Cited by 22 publications

(25 citation statements)

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“…We were able to distinguish populations A and B on the basis of the same criteria as were employed at low z applied to the UV (Sect. 2.3 and Negrete et al 2014), and quantitative population A-B differences in EW and profile measurements previously found at low redshift are confirmed in the high-redshift GTC sample. Civλ1549 in population A sources shows a systematically lower EW than population B, as well as blue asymmetric and blueshifted profiles.…”

Section: Resultssupporting

confidence: 79%

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GTC spectra ofz≈ 2.3 quasars: comparison with local luminosity analogs

Sulentic¹,

Marziani²,

Olmo³

et al. 2014

A&A

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Context. The advent of 8−10 m class telescopes for the first time makes it possible to compare in detail quasars with similar luminosity and very different redshifts. Aims. We conducted 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 [erg s −1 ]), 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. Methods. Moderate signal-to-noise ratio spectra for 22 high-redshift sources were obtained with the 10.4 m Gran Telescopio Canarias (GTC), for which the HST (largely the Faint Object Spectrograph) archive provides a low-redshift control sample. We compared the spectra in the context of the 4D Eigenvector 1 formalism, meaning that we divided both source samples into highly accreting population A and population B sources accreting at a lower rate. Results. Civλ1549, the strongest and most reliable diagnostic line, shows very similar properties at both redshifts, which confirms the Civλ1549 profile differences at high redshift between populations A and B, which are well established in local quasars. The Civλ1549 blueshift that appears quasi-ubiquitous in higher L sources is found in only half (population A) of the quasars observed in the two samples. A Civλ1549 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 M BH or L/L Edd is found. Conclusions. Spectroscopic differences established at low z are also present in much higher redshift quasars. Our results on the Civλ1549 blueshift suggest that it depends both on source luminosity and L/L Edd . 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 are not large enough to effectively constrain possible changes of M BH or L/L Edd with redshift. The two samples appear representative of a slowly evolving quasar population that is most likely present at all redshifts.

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Section: Resultssupporting

confidence: 79%

“…The optical and UV (as well as X-ray) criteria are summarized in Sulentic et al (2007). Criteria employed in the present paper are also discussed in Negrete et al (2014) and entail the following: (1) line widths of Aliiiλ1860 and Siiiλ1814 Fig. 3.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

GTC spectra ofz≈ 2.3 quasars: comparison with local luminosity analogs

Sulentic¹,

Marziani²,

Olmo³

et al. 2014

A&A

Self Cite

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“…More problematic could be the challenge of measuring some of these lines. For example, [Ne iii]λ3343 can potentially be blended with the [Ne v]λ3347 line (Schirmer et al 2013), while Si ii λ1814 has been found to be very weak in high-redshift quasars (Negrete et al 2014). …”

Section: Ne-based Diagnostics In the Near Ultravioletmentioning

confidence: 99%

Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths

Feltre¹,

Charlot²,

Gutkin³

2016

Mon. Not. R. Astron. Soc.

296

461

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In the context of observations of the rest-frame ultraviolet and optical emission from distant galaxies, we explore the emission-line properties of photoionization models of active and inactive galaxies. Our aim is to identify new line-ratio diagnostics to discriminate between gas photoionization by active galactic nuclei (AGN) and star formation. We use a standard photoionization code to compute the emission from AGN narrow-line regions and compare this with calculations of the nebular emission from star-forming galaxies achieved using the same code. We confirm the appropriateness of widely used optical spectral diagnostics of nuclear activity versus star formation and explore new diagnostics at ultraviolet wavelengths. We find that combinations of a collisionally excited metal line or line multiplet, such as C iv λλ1548, 1551,iii]λ1892 and [C iii]λ1907+C iii]λ1909, with the He ii λ1640 recombination line are individually good discriminants of the nature of the ionizing source. Diagrams involving at least 3 of these lines allow an even more stringent distinction between active and inactive galaxies, as well as valuable constraints on interstellar gas parameters and the shape of the ionizing radiation. Several line ratios involving Ne-based emission lines, such as [Ne iv]λ2424, [Ne iii]λ3343 and [Ne v]λ3426, are also good diagnostics of nuclear activity. Our results provide a comprehensive framework to identify the sources of photoionization and physical conditions of the ionized gas from the ultraviolet and optical nebular emission from galaxies. This will be particularly useful to interpret observations of high-redshift galaxies with future facilities, such as the James Webb Space Telescope and extremely large ground-based telescopes.

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“…The existence and the brightness of the semi-forbidden emission C III]λ1909 allows to estimate the density as ∼ 10 10 cm −3 (Osterbrock & Ferland 2006). Higher density values are favoured by Moloney & Shull (2014), Negrete et al (2014) and Ruff et al (2012) who fitted the existing hydrogen line intensities with CLOUDY models to reconstruct the spectral shape of the source. They also arrive to a rather large value of ionization parameter U ∼ 0.3.…”

Section: Model Setupmentioning

confidence: 99%

“…In particular, lower-ionization lines like Mg IIλ2800 require systematically lower ionization parameters (and thus larger radii or larger volume and column densities) than higher-ionization lines like C IVλ1549 and He IIλ1640. As it was mentioned in numerous works (Korista & Goad 2000;Negrete et al 2014;Ruff et al 2012;Moloney & Shull 2014), any reasonable fit aiming to reproduce the spectrum of a BLR in details should be multi-component. It is also instructive in more comprehensive models to consider more sophisticated radial distributions of cloud density.…”

Section: Appearance Of the Blrmentioning

confidence: 99%

Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

Abolmasov

Poutanen

2016

Mon. Not. R. Astron. Soc.

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The GeV-range spectra of blazars are shaped not only by non-thermal emission processes internal to the relativistic jet but also by external pair-production absorption on the thermal emission of the accretion disc and the broad-line region (BLR). For the first time, we compute here the pair-production opacities in the GeV range produced by a realistic BLR accounting for the radial stratification and radiation anisotropy. Using photoionization modelling with the CLOUDY code, we calculate a series of BLR models of different sizes, geometries, cloud densities, column densities and metallicities. The strongest emission features in the model BLR are Lyα and He II Lyα. Contribution of recombination continua is smaller, especially for hydrogen, because Ly continuum is efficiently trapped inside the large optical depth BLR clouds and converted to Lyman emission lines and higher-order recombination continua. The largest effects on the gamma-ray opacity are produced by the BLR geometry and localization of the gamma-ray source. We show that when the gamma-ray source moves further from the central source, all the absorption details move to higher energies and the overall level of absorption drops because of decreasing incidence angles between the gamma-rays and BLR photons. The observed positions of the spectral breaks can be used to measure the geometry and the location of the gamma-ray emitting region relative to the BLR. Strong dependence on geometry means that the soft photons dominating the pair-production opacity may be actually produced by a different population of BLR clouds than the bulk of the observed broad line emission.

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A New Method to Obtain the Broad Line Region Size of High Redshift Quasars

Cited by 22 publications

References 100 publications

GTC spectra ofz≈ 2.3 quasars: comparison with local luminosity analogs

GTC spectra ofz≈ 2.3 quasars: comparison with local luminosity analogs

Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths

Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

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