THE COMPOSITE SPECTRUM OF BOSS QUASARS SELECTED FOR STUDIES OF THE Lyα FOREST

Harris, David W.; Jensen, Trey W.; Suzuki, N.; Bautista, Julian; Dawson, Kyle; Vivek, M.; Brownstein, Joel R.; Ge, Jian; Hamann, Fred; Herbst, H.; Jiang, Linhua; Moran, Sarah E.; Myers, Adam D.; Olmstead, Matthew D.; Schneider, Donald P.

doi:10.3847/0004-6256/151/6/155

Cited by 49 publications

(29 citation statements)

References 57 publications

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“…The first major change improves the way atmospheric differential refraction (ADR) corrections are applied to eBOSS spectra, and is described in T. Jensen et al (2016, in preparation). The improved ADR corrections are similar to prior work (Margala et al 2015;Harris et al 2016) and primarily improve flux calibrations for quasar spectra. The second change corrects a known bias in the co-addition of individual exposures.…”

Section: Optimization Of Redmonster Parameters For Eboss Lrgssupporting

confidence: 64%

REDSHIFT MEASUREMENT AND SPECTRAL CLASSIFICATION FOR eBOSS GALAXIES WITH THE REDMONSTER SOFTWARE

Hutchinson

Bolton

Dawson

et al. 2016

Self Cite

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We describe the redmonster automated redshift measurement and spectral classification software designed for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). We describe the algorithms, the template standard and requirements, and the newly developed galaxy templates to be used on eBOSS spectra. We present results from testing on early data from eBOSS, where we have found a 90.5% automated redshift and spectral classification success rate for the luminous red galaxy sample (redshifts 0.6  z  1.0). The redmonster performance meets the eBOSS cosmology requirements for redshift classification and catastrophic failures and represents a significant improvement over the previous pipeline. We describe the empirical processes used to determine the optimum number of additive polynomial terms in our models and an acceptable c D r 2 threshold for declaring statistical confidence. Statistical errors on redshift measurement due to photon shot noise are assessed, and we find typical values of a few tens of km s −1 . An investigation of redshift differences in repeat observations scaled by error estimates yields a distribution with a Gaussian mean and standard deviation of μ∼0.01 and σ∼0.65, respectively, suggesting the reported statistical redshift uncertainties are over-estimated by ∼54%. We assess the effects of object magnitude, signal-to-noise ratio, fiber number, and fiber head location on the pipeline's redshift success rate. Finally, we describe directions of ongoing development.

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Section: Optimization Of Redmonster Parameters For Eboss Lrgssupporting

confidence: 64%

REDSHIFT MEASUREMENT AND SPECTRAL CLASSIFICATION FOR eBOSS GALAXIES WITH THE REDMONSTER SOFTWARE

Hutchinson

Bolton

Dawson

et al. 2016

Self Cite

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“…Harris et al (2016) provide an empirical, global correction to this effect by using standard stars observed in the same fashion as quasar targets. Likewise, Margala et al (2015) derive a first principles estimate of ADR for each quasar target and apply corrections to the final coadded spectra.…”

Section: Data Reductionmentioning

confidence: 99%

“…After application of these constraints, 143,341 quasar spectra remain. Additionally, all quasars observed at an airmass above 1.2 are removed, as the spectrophotometric correction (see Harris et al 2016) may be less certain at high airmass. The remaining sample is large enough that removing the ∼30,000 high airmass quasars will not significantly affect the final results.…”

Section: Sample Selectionmentioning

confidence: 99%

“…The spectral index is defined by fitting the power law l l = a l f b ( ) to the estimated quasar continuum. We choose a range of wavelengths to model the quasar continuum in which visual inspection of the high S/N composite spectrum from Harris et al (2016) reveals no clear features. We use two regions: 1440-1480 Å and 2160-2230 Å.…”

Section: Sample Selectionmentioning

confidence: 99%

“…Weaker emission lines, unidentifiable in single objects, are detectable in composite spectra. This method has been employed over a wide range of quasar samples such as the Large Bright Quasar Survey (Francis et al 1991;Hewett et al 1995), FIRST Bright Quasar Survey (White et al 2000;Brotherton et al 2001), Sloan Digital Sky Survey (SDSS; York et al 2000;Vanden Berk et al 2001), Hubble Space Telescope (HST; Zheng et al 1997;Telfer et al 2002), HST-Far Ultraviolet Spectroscopic Explorer (Scott et al 2004), HST-Cosmic Origin Spectrograph (Shull et al 2012;Stevans et al 2014;Tilton et al 2016), Baryon Acoustic Oscillation Spectroscopic Survey (BOSS; Dawson et al 2013;Harris et al 2016), and VLT-XSHOOTER (Selsing et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Spectral Evolution in High Redshift Quasars From the Final Baryon Oscillation Spectroscopic Survey Sample

Jensen

Vivek

Dawson

et al. 2016

ApJ

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We report on the diversity in quasar spectra from the Baryon Oscillation Spectroscopic Survey. After filtering the spectra to mitigate selection effects and Malmquist bias associated with a nearly flux-limited sample, we create high signal-to-noise ratio composite spectra from 58,656 quasars (   z 2.1 3.5), binned by luminosity, spectral index, and redshift. With these composite spectra, we confirm the traditional Baldwin effect (BE, i.e., the anticorrelation of C IV equivalent width (EW) and luminosity) that follows the relation µ , and −0.41±0.005 for z=2.25, 2.46, and 2.84, respectively. In addition to the redshift evolution in the slope of the BE, we find redshift evolution in average quasar spectral features at fixed luminosity. The spectroscopic signature of the redshift evolution is correlated at 98% with the signature of varying luminosity, indicating that they arise from the same physical mechanism. At a fixed luminosity, the average C IV FWHM decreases with increasing redshift and is anti-correlated with C IV EW. The spectroscopic signature associated with C IV FWHM suggests that the trends in luminosity and redshift are likely caused by a superposition of effects that are related to black hole mass and Eddington ratio. The redshift evolution is the consequence of a changing balance between these two quantities as quasars evolve toward a population with lower typical accretion rates at a given black hole mass.

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Extreme quasars at high redshift

Martínez-Aldama

Olmo

Marziani

et al. 2018

A&A

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Context. Quasars radiating at extreme Eddington ratios (hereafter xA quasars) are likely a prime mover of galactic evolution and have been hailed as potential distance indicators. Their properties are still scarcely known. Aims. We test the effectiveness of the selection criteria defined on the "4D Eigenvector 1" (4DE1) for identifying xA sources. We provide a quantitative description of their rest-frame UV spectra (1300 -2200 Å) in the redshift range 2 z 2.9, with a focus on major emission features. Methods. Nineteen extreme quasar candidates were identified using 4DE1 selection criteria applied to SDSS spectra: Aliiiλ1860/Siiii]λ1892 0.5 and Ciii]λ1909/Siiii]λ1892 1. The emission line spectra was studied using multicomponent fits of deep spectroscopic observations (S/N 40 − 50; spectral resolution ≈ 250 km s −1 ) obtained with the OSIRIS at Gran Telescopio Canarias (GTC). Results. GTC spectra confirm that almost all of these quasars are xA sources with very similar properties. We provide spectrophotometric and line profile measurements for the Siivλ1397+Oiv]λ1402, Civλ1549+Heiiλ1640, and the 1900Å blend. This last feature is found to be predominantly composed of Aliiiλ1860, Siiii]λ1892 and Feiii emission features, with weak Ciii]λ1909. The spectra can be characterized as very low ionization (ionization parameter, log U ∼ −3), a condition that explains the significant Feiii emission observed in the spectra. xA quasars show extreme properties in terms of Civλ1549 equivalent width and blueshift amplitudes. Civλ1549 shows low equivalent width, with a median value of 15Å ( 30 Å for the most sources), and high or extreme blueshift amplitudes (-5000 c( 1 2 ) -1000 km s −1 ). Weak-lined quasars appear as extreme xA quasars and not as an independent class. The Civλ1549 high amplitude blueshifts coexists in all cases save one with symmetric and narrower Aliiiλ1860 and Siiii]λ1892 profiles. Estimates of the Eddington ratio using the Aliiiλ1860 FWHM as a virial broadening estimator are consistent with the ones of a previous xA sample.Conclusions. xA quasars show distinguishing properties that make them easily identifiable in large surveys and potential "standard candles" for cosmological applications. It is now feasible to assemble large samples of xA quasars from the latest data releases of the SDSS. We provide evidence that Aliiiλ1860 could be associated with a low-ionization virialized sub-system, supporting previous suggestions that Aliii is a reliable virial broadening estimator.

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THE COMPOSITE SPECTRUM OF BOSS QUASARS SELECTED FOR STUDIES OF THE Lyα FOREST

Cited by 49 publications

References 57 publications

REDSHIFT MEASUREMENT AND SPECTRAL CLASSIFICATION FOR eBOSS GALAXIES WITH THE REDMONSTER SOFTWARE

REDSHIFT MEASUREMENT AND SPECTRAL CLASSIFICATION FOR eBOSS GALAXIES WITH THE REDMONSTER SOFTWARE

Spectral Evolution in High Redshift Quasars From the Final Baryon Oscillation Spectroscopic Survey Sample

Extreme quasars at high redshift

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