[Paper Review] Optical Spectroscopic ATLAS of the MOJAVE/2cm AGN Sample (1)

J. Torrealba, V. Chavushyan+4 more|arXiv (Cornell University)|Jul 18, 2011

Medical Imaging Techniques and Applications1 references18 citations

TL;DR

This paper presents the first intermediate-resolution (8–15 Å) optical spectroscopic atlas for 123 core-dominated, radio-loud AGN with relativistic jets from the MOJAVE/2cm sample at 15 GHz. It provides homogeneous spectroscopic parameters—line fluxes, FWHM, equivalent widths, and luminosities—for Hβ, [O III] λ5007, Mg II λ2798, C IV λ1549, and Fe II emission lines, alongside B-band photometry for 242 sources, enabling statistical analysis of jet-continuum-emission line connections across multi-scale AGN physics.

ABSTRACT

We present an optical spectroscopic atlas at intermediate resolution (8-15A) for 123 core-dominated radio-loud active galactic nuclei with relativistic jets, drawn from the MOJAVE/2cm sample at 15GHz. It is the first time that spectroscopic and photometric parameters for a large sample of such type of AGN are presented. The atlas includes spectral parameters for the emission lines Hb, [O III] 5007, Mg II 2798 and/or C IV 1549 and corresponding data for the continuum, as well as the luminosities and equivalent widths of the Fe II UV/optical. It also contains the homogeneous photometric information in the B-band for 242 sources of the sample, with a distribution peak at BJ=18.0 and a magnitude interval of 11.1< BJ <23.7.

Motivation & Objective

• To compile a comprehensive, homogeneous spectroscopic and photometric dataset for a large sample of core-dominated, radio-loud AGN with relativistic jets.
• To enable statistical analysis of the physical connections between the central engine, pc-scale jets, and emission-line regions across multi-scale AGN structures.
• To provide high signal-to-noise (S/N ~30) intermediate-resolution spectroscopy for 123 AGN and B-band photometry for 242 AGN from the MOJAVE/2cm sample.
• To establish a foundation for studying correlations between optical, radio, and γ-ray emission in compact, core-dominated AGN.
• To support future investigations into the kinematics, structure, and emission mechanisms of the broad and narrow-line regions relative to jet properties.

Proposed method

• Acquired intermediate-resolution optical spectroscopy (8–15 Å) at OAN–SPM and OAGH for 123 AGN from the MOJAVE/2cm sample.
• Measured fluxes, full width at half maximum (FWHM), and equivalent widths (EW) for key emission lines: Hβ, [O III] λ5007, Mg II λ2798, C IV λ1549, and Fe II λ4570/2490.
• Calculated luminosities and EWs for Fe II emission in 22 and 67 sources, respectively, using a standard template.
• Performed photometric calibration to obtain homogeneous B-band magnitudes (BJ) for 242 sources, with a peak at BJ = 18.0 and range 11.1 ≤ BJ ≤ 23.7.
• Cross-matched data with archival catalogs (USNO-B, MAPS, NED, SDSS, MAST) for source identification and ancillary information.
• Used the resulting dataset to enable statistical analysis of correlations between optical, radio (15 GHz), and jet properties in core-dominated AGN.

Experimental results

Research questions

• RQ1 What are the statistical correlations between optical continuum and 15 GHz radio emission in core-dominated AGN?
• RQ2 How do the properties of broad and narrow emission lines (e.g., FWHM, EW, luminosity) relate to the kinematics and structure of pc-scale relativistic jets?
• RQ3 What is the role of Fe II emission in the optical spectra of these AGN, and how does it correlate with other emission components?
• RQ4 How do the spectroscopic parameters of Hβ, [O III], Mg II, and C IV relate to the viewing angle and jet orientation in superluminal sources?
• RQ5 To what extent does the optical emission in these AGN originate in the jet base or in the broad-line region, and how is this linked to radio variability?

Key findings

• The atlas presents the first homogeneous spectroscopic parameters for 123 core-dominated, radio-loud AGN with relativistic jets, with signal-to-noise ratios ~30.
• Luminosities and equivalent widths of Fe II emission were measured for 22 sources at λ4570 and 67 at λ2490, enabling statistical study of Fe II contribution to the optical spectrum.
• B-band photometry was homogenized for 242 sources, with a magnitude distribution peaking at BJ = 18.0 and spanning 11.1 ≤ BJ ≤ 23.7.
• A significant positive correlation was found between optical nuclear emission and total 15 GHz radio emission in 99 quasars, indicating co-spatial origin in the innermost jet region.
• The data confirm that optical and radio emission in BL Lacs are correlated, supporting a beamed origin of optical emission in the jet base.
• The dataset enables future analysis of the physical link between the central engine, jet kinematics, and emission-line regions across sub-parsec to kpc scales.