Composite spectra of quasars with different UV spectral index

Ivashchenko, G.; Sergijenko, O.; Torbaniuk, O.

doi:10.1093/mnras/stt2137

Cited by 10 publications

(12 citation statements)

References 42 publications

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“…Previously, using composite spectra of quasars with different α λ , we showed that there is no correlation between α λ and log l 1450 (Ivashchenko, Sergijenko & Torbaniuk 2013), and did not found any dependence of EW of lines within 1210-1450Å on spectral index α λ (calculated within the range 1270-1480Å) (Torbaniuk, Ivashchenko & Sergijenko 2012). But due to the fact, that the latter study was carried out without separation by luminosity, its result requires verification on a sample of spectra with different luminosity as well.…”

Section: Introductionmentioning

confidence: 77%

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Dependence of equivalent width of quasar emission lines on UV-optical spectral index

Torbaniuk

Ivashchenko

2013

Proc. IAU

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Abstract. Using 192 composite spectra stacked from subsamples of individual SDSS quasar spectra binned in spectral index, α λ , and logarithm of monochromatic luminosity at 1450Å, log l1450 , and modelling separate spectral ranges with superposition of emission lines it was found that: there is a dependence of emission line equivalent width (EW) on α λ (correlation or anti-correlation) for some lines, mostly for those lines for which the Baldwin effect is detected, while for the lines for which the Baldwin effect is not observed any α λ -dependence was found.

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Section: Introductionmentioning

confidence: 77%

“…For our study we stacked 16 × 12 = 192 composite spectra from spectra subsamples binned in α λ = −2.3 + i · 0.1 (i = 0.15) and log l 1450 = 42.2 + k · 0.1 (k = 0.11), using a sample of quasar spectra selected from the Sloan Digital Sky Survey (SDSS) Data Release 7 by Ivashchenko, Sergijenko & Torbaniuk (2013).…”

Section: The Data and Methodsmentioning

confidence: 99%

Dependence of equivalent width of quasar emission lines on UV-optical spectral index

Torbaniuk

Ivashchenko

2013

Proc. IAU

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“…The subsample compiled for the composite spectra production will also be used for studying the spectral properties of quasars and relations between them, that can shed light on the quasar physics. For example, in our previous studies with the smaller sample of quasar spectra from SDSS DR7, we showed that there is no correlation between the spectral index α λ and the monochromatic luminosity at 1450 Å, log l 1450 [2]. We also found that there is a dependence of the emission line equivalent width on spectral index (correlation or anti-correlation) for some of the lines, mostly for those for which the Baldwin eect is detected, and that there is no dependence between the virial mass of the central supermassive black hole of a quasar and its spectral index α λ [8,9].…”

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confidence: 85%

A quasar sample for the Lyα forest studies from the Data Release 10 of the Sloan Digital Sky Survey

Torbaniuk¹

2015

Adv.Astron.Spa.Physics

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Main Astronomical Observatory of the NAS of Ukraine, 27 Akademika Zabolotnoho Str., Kyiv 03680, UkraineWe present a new sample of the z ≥ 2 quasar spectra. It contains 102 643 spectra which were visually selected from the SDSS DR10, and includes also a subsample of 65 976 spectra for the composite spectra compilation. This sample will be used for the Lyα forest studies, and can be used for other studies, including those of the quasar spectral properties and the spatial distribution of quasars at z > 2. The compiled composite spectra will be used for the determination of the intrinsic spectrum in the Lyα forest studies. Those objects which were not included into the main sample and rejected during the visual examination, are 11 192 quasars with the broad absorption lines, 6 804 spectra with the damped Lyα systems, 1 248 and 493 spectra with the absorption in the Lyα and Lyβ lines, respectively. The non-quasar objects, including 191 candidates for blazars and 30 galaxies with starburst, as well as 617 quasar spectra with wrong redshift, 417 incomplete spectra and 1 497 spectra with low S/N ratio, were also excluded.

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“…For example, Richards et al (2011) argue that the C IV emission varies with quasar winds and the spectrum of the ionizing continuum. The color of the quasar defined by the spectral index is another feature of spectral diversity; e.g., Ivashchenko et al (2014) report that variations in spectral index lead to systematic errors in redshift estimates.…”

Section: Sample Selectionmentioning

confidence: 99%

Measurements of Effective Optical Depth in the Lyα Forest from the BOSS DR12 Quasar Sample

Kamble

Dawson²,

Bourboux³

et al. 2020

ApJ

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We measure the effective optical depth in the Lyα forest using 40,035 quasar spectra from the Twelfth Data Release (DR12) of the Baryon Oscillation Spectroscopic Survey of Sloan Digital Sky Survey IV. A rigorous selection based on spectral index and the equivalent width of the C IV emission line is applied to choose seven uniform samples with minimal intrinsic variations across redshifts. Modeling the redshift evolution of the effective optical depth with a power law,´-5.54 0.64 10 0 3 and g =  3.182 0.074. The 2.2% precision estimate on γ is dominated by systematic errors, likely arising from the bias and uncertainties in spectral index estimates. Even after incorporating the systematic errors, this work provides the most precise estimates of optical depth parameters to date. Finally, using the reconstructed Lyα forest continuum to directly measure the transmitted flux ratio as a function of redshift, we find deviations of less than 2.5% from the predictions from the global model and no convincing evidence for signal associated with He II reionization.

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Composite spectra of quasars with different UV spectral index

Cited by 10 publications

References 42 publications

Dependence of equivalent width of quasar emission lines on UV-optical spectral index

Dependence of equivalent width of quasar emission lines on UV-optical spectral index

A quasar sample for the Lyα forest studies from the Data Release 10 of the Sloan Digital Sky Survey

Measurements of Effective Optical Depth in the Lyα Forest from the BOSS DR12 Quasar Sample

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