A Census of Active Galactic Nuclei Identified by the Mid-infrared [Ne <scp>v</scp> ] Line at <i>z</i> ≤ 0.025

Abstract We present a census of local active galactic nuclei (AGN) at a redshift of z ≤ 0.025 selected using the high-ionization [Ne v ] λ 14.32 μ m emission line from the Infrared Database of Extragalactic Observables from Spitzer. We identify 103 sources with detected [Ne v ] emission, which we regard as AGN within the volume. This sample represents ∼18% of the galaxy population within this redshift range, consistent with AGN fractions derived using other selection techniques. We investigate the biases and properties of this [Ne v ]-selected AGN sample by comparing it with traditional AGN selection methods based on hard X-ray, optical, and mid-infrared colors. We find that our selection significantly misses AGN with underdeveloped narrow-line regions (NLRs), which account for approximately half of the AGN identified by NLR-independent methods. However, ∼10% of our sample is undetected in optical diagnostics, while ∼40% is missed by hard X-rays and ∼70% by infrared continuum. Notably, ∼15% of our AGN are missed by all classical methods, constituting a population of previously unidentified AGN revealed solely by the [Ne v ] emission line. Based on our analysis, we show that this line can efficiently select heavily Compton-thick and host-dominated AGN systems. Our analysis also yields mean bolometric luminosities of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">bol</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">erg</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>44.5</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.7</mml:mn> </mml:math> , black hole masses of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">BH</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>7.3</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.6</mml:mn> </mml:math> , and an Eddington ratio of λ Edd = 0.15 ± 0.11. Our sample harbors AGN with comparable luminosities but systematically lower-mass black holes accreting at higher Eddington ratios than those in the hard X-ray-selected sample. This suggests that our AGN may represent local analogs of the rapidly growing SMBH population prevalent at cosmic noon.