[Paper Review] SDSS-IV/SPIDERS: A Catalogue of X-Ray Selected AGN Properties; Spectral Properties and Black Hole Mass Estimates for SPIDERS SDSS DR14 Type 1 AGN

Damien Coffey, M. Salvato+8 more|arXiv (Cornell University)|Apr 24, 2019

Astrophysical Phenomena and Observations107 references7 citations

TL;DR

This paper presents a comprehensive spectroscopic catalogue of 8,501 X-ray selected Type 1 AGN from the SPIDERS survey using SDSS DR14 data, measuring emission line properties, continuum fluxes, and black hole masses via Hβ and MgII lines. It provides robust black hole mass estimates up to z ≈ 2.5 using single-epoch methods and publicly releases the results as an SDSS-IV DR14 value-added catalogue.

ABSTRACT

This work presents the catalogue of optical spectral properties for all X-ray selected SPIDERS active galactic nuclei (AGN) up to SDSS DR14. SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV programme that is currently conducting optical spectroscopy of the counterparts to the X-ray selected sources detected in the ROSAT all-sky survey and the XMM-Newton slew survey in the footprint of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). The SPIDERS DR14 sample is the largest sample of X-ray selected AGN with optical spectroscopic follow-up to date. The catalogue presented here is based on a clean sample of 7344 2RXS ($ m \bar{z}$ = 0.5) and 1157 XMM-Newton slew survey ($ m \bar{z}$ = 0.4) type 1 AGN with spectroscopic coverage of the H$ m β$ and/or MgII emission lines. Visual inspection results for each object in this sample are available from a combination of literature sources and the SPIDERS group, which provide both reliable redshifts and source classifications. The spectral regions around the H$ m β$ and MgII emission lines have been fit in order to measure both line and continuum properties, estimate bolometric luminosities, and provide black hole mass estimates using the single-epoch (or photoionisation) method. The use of both H$ m β$ and MgII allows black hole masses to be estimated up to z $ m \simeq$ 2.5. A comparison is made between the spectral properties and black hole mass estimates derived from H$ m β$ and MgII using the subsample of objects which have coverage of both lines in their spectrum. These results have been made publicly available as an SDSS-IV DR14 value added catalogue.

Motivation & Objective

• To create a large, uniformly analyzed sample of X-ray selected Type 1 AGN with high-quality optical spectroscopy for studying AGN demographics and evolution.
• To measure spectral properties such as line fluxes, FWHM, and continuum components in the Hβ and MgII regions for accurate black hole mass estimation.
• To provide publicly accessible, reliable black hole mass and Eddington ratio estimates using multiple calibration methods for the largest X-ray-selected AGN sample to date.
• To enable cross-comparison of black hole mass estimates derived from Hβ and MgII lines in a common, high-redshift sample (up to z ≈ 2.5).

Proposed method

• The study uses optical spectroscopy from the SPIDERS survey (SDSS-IV/eBOSS) to analyze 7,344 2RXS and 1,157 XMM-Newton slew survey Type 1 AGN with redshifts up to z ≈ 2.5.
• Spectral regions around Hβ and MgII emission lines were fitted using a combination of Gaussian components, galaxy templates, and Fe II templates to model continuum and line emission.
• Monochromatic luminosities at 2500 Å, 3000 Å, and 5100 Å were measured to estimate bolometric luminosities using standard scaling relations.
• Black hole masses were estimated using the single-epoch method with the Vestergaard & Peterson (2006) and Assef et al. (2011) calibrations for Hβ, and Shen & Liu (2012) for MgII.
• Eddington ratios were computed as the ratio of bolometric luminosity to Eddington luminosity derived from the respective mass estimates.
• Visual inspection and literature cross-verification ensured reliable redshifts and source classifications, with uncertainty estimates propagated for all derived quantities.

Experimental results

Research questions

• RQ1 How do black hole mass estimates derived from Hβ and MgII lines compare in a large, uniformly analyzed sample of X-ray selected AGN?
• RQ2 What are the spectral properties (line fluxes, FWHM, continuum components) of X-ray selected Type 1 AGN across the redshift range z ≈ 0 to z ≈ 2.5?
• RQ3 What is the distribution of bolometric luminosities and Eddington ratios in a complete, X-ray-selected AGN sample with spectroscopic coverage?
• RQ4 How accurately can black hole masses be estimated using the MgII line at high redshift (z ≈ 2.5) using the Shen & Liu (2012) calibration?
• RQ5 What is the impact of Fe II emission and host galaxy contamination on spectral fitting and derived physical parameters in the Hβ and MgII regions?

Key findings

• The SPIDERS DR14 sample comprises 8,501 X-ray selected Type 1 AGN, making it the largest spectroscopically confirmed sample of X-ray-selected AGN to date.
• Black hole masses were estimated using the Hβ line up to z ≈ 2.5 with the Vestergaard & Peterson (2006) and Assef et al. (2011) calibrations, and using the MgII line up to z ≈ 2.5 with the Shen & Liu (2012) calibration.
• The study provides monochromatic luminosities at 2500 Å, 3000 Å, and 5100 Å with uncertainties, enabling consistent bolometric luminosity estimates.
• Bolometric luminosities were derived from both 3000 Å and 5100 Å luminosities, with associated uncertainties, and used to compute Eddington ratios.
• The catalogue includes 189 derived parameters per source, including line FWHM, flux ratios (e.g., [OIII]5007/Hβ), Fe II normalization, and absorption flags.
• The results are publicly released as an SDSS-IV DR14 value-added catalogue, enabling broad community use for AGN demographics and coevolution studies.