The Mid-Infrared Narrow Line Baldwin Effect Revealed by Spitzer

Abstract

We present our discovery of a narrow-line Baldwin effect, an anti-correlation between the equivalent width (EW) of a line and the flux of the associated continuum, in 5-20$\mu$m mid-infared lines from a sample of 68 Active Galactic Nuclei (AGN), located at z$<$0.5, observed with the Infrared Spectrograph on the {\it Spitzer Space Telescope}. Our analysis reveals a clear anti-correlation between the EW of the [SIV] 10.51$\mu$m, [NeII] 12.81$\mu$m, and [NeIII] 15.56$\mu$m lines and their mid-IR continuum luminosities, while the Baldwin effect for [NeV] 14.32$\mu$m is not as obvious. We suggest that this anti-correlation is driven by the central AGN and not circumnuclear star formation in the host galaxy. We also find that the slope of the narrow-line Baldwin effect in the mid-infrared does not appear to steepen with increasing ionization potential. Examining the dependence of the EW to the Eddington Ratio ($L/L_{Edd}$) we find no strong relationship for mid-IR lines. Our study indicates that the narrow-line mid-infrared Baldwin Effect is quite different from the broad-line optical/UV Baldwin effect and it is possible that the two effects are unrelated. The discovered anti-correlations open new possibilities in the understanding the physics of the ionizing region and the continuum reprocessing by dust.

18 pages, 4 figures. Accepted for publication by ApJ

References in corpus (23)

• The Infrared Spectrograph on the Spitzer Space Telescope
• Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships
• What Powers Ultra-luminous IRAS Galaxies?
• AGN Black Hole Masses and Bolometric Luminosities
• The SMART Data Analysis Package for the Infrared Spectrograph on the Spitzer Space Telescope
• Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope II: The IRAS Bright Galaxy Sample
• Mid-IR Galaxy Classification Based on Silicate Obscuration and PAH Equivalent Width
• On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies
• The nature and evolution of Ultraluminous Infrared Galaxies: A mid-infrared spectroscopic survey
• Cepheid Calibrations from the Hubble Space Telescope of the Luminosity of Two Recent Type Ia Supernovae and a Re-determination of the Hubble Constant
• The Detection of Silicate Emission from Quasars at 10 and 18 Microns
• MCG-6-30-15: Long Timescale X-Ray Variability, Black Hole Mass and AGN High States
• Continuum and Emission Line Strength Relations for a large Active Galactic Nuclei Sample
• On the dependence of the iron K-line profiles with luminosity in Active Galactic Nuclei
• The correlation of line strength with luminosity and redshift from composite QSO spectra
• Spectral decomposition of starbursts and AGNs in 5-8 micron Spitzer IRS spectra of local ULIRGs
• On the origin of the C IV Baldwin effect in AGN
• Black hole masses from power density spectra: determinations and consequences
• The Baldwin Effect and Black Hole Accretion: A Spectral Principal Component Analysis of a Complete QSO Sample
• A Relation Between Supermassive Black Hole Mass and Quasar Metallicity?
• Quasar Evolution and the Baldwin Effect in the Large Bright Quasar Survey
• XMM-Newton observations of 3C 273
• Discovery of a strong Baldwin effect in mid-infrared AGN lines

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• Far-infrared line spectra of active galaxies from the Herschel/PACS Spectrometer: the complete database
• PAH features within few hundred parsecs of active galactic nuclei
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• Dust Emission from Unobscured Active Galactic Nuclei
• The Baldwin effect in the narrow emission lines of AGNs
• The AGN contribution to the UV-FIR luminosities of interacting galaxies and its role in identifying the Main Sequence
• The environment of weak emission-line quasars
• Polar Dust Emission in Quasar IR SEDs and Its Correlation with Narrow Line Regions
• Characterizing Quasars in the Mid-infrared: High Signal-to-Noise Spectral Templates
• Narrow lines correlations in an SDSS sample of type 1 quasars