Quasars as Cosmological Standard Candles

C Alenka Negrete,Ascensión Del Olmo,Paola Marziani,Mary L Martínez-Aldama,Jack W Sulentic,Donají Esparza-Arredondo,Deborah Dultzin

doi:10.3389/fspas.2017.00059

Abstract

We propose the use of quasars with accretion rate near to Eddington ratio (extreme quasars) as standard candles. The selection criteria is based on the Eigenvector 1 (E1) formalism. Our first sample is a selection of 334 optical quasar spectra from the SDSS DR7 database with a S/N \gt 20. Using the E1, we define primary and secondary selection criteria in the optical spectral range. We show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Our results are consistent with concordance cosmology but we need to work with other spectral ranges to take into account the quasar orientation, among other constrains.

Highlights

Active Galactic Nuclei (AGN or quasars) are among the most powerful objects in the Universe
Sulentic et al (2000) propose the presence of two main populations based on the optical plane (FWHM(HβBC) vs RFeII): Population A for quasars with FWHM(HβBC) < 4,000 km s−1and Population B for those with FWHM(HβBC) > 4,000 km s−1 (Figure 1 of Sulentic et al, 2002)
We used a sample of quasars chosen from the Sloan Digital Sky Survey Data Release 7 Shen et al (2011), to identify the extreme accretors in the optical range at low redshift (z < 0.8). The identification of these quasars will follow the description of the E1 parameter space in the optical plane

Summary

INTRODUCTION

Active Galactic Nuclei (AGN or quasars) are among the most powerful objects in the Universe. Sulentic et al (2000) propose the presence of two main populations based on the optical plane (FWHM(HβBC) vs RFeII): Population A for quasars with FWHM(HβBC) < 4,000 km s−1and Population B for those with FWHM(HβBC) > 4,000 km s−1 (Figure 1 of Sulentic et al, 2002) Their phenomenological study shows that there are spectral characteristics that distinguish objects within the same population, especially those within Pop. A. There have been several works focused on measuring cosmological distances using different objects as standard candles. In 2014, Marziani and Sulentic (2014) proposed the use of a specific type of quasars as standard candles They studied objects that show extreme accretion near to the Eddington limit.

SAMPLE SELECTION

METHODOLOGY

EXTREME ACCRETORS AS STANDARD CANDLES