Active Galactic Nuclei in a Mid-Infrared Selected Galaxy Sample at z>0.13: [Ne V]3426 Line Emission as a Benchmark
The Astrophysical Journal(2024)
摘要
We present a 24 um-selected spectroscopic sample z > 0.13 (median z = 0.41)
in the Lockman Hole field, consisting of 4035 spectra. Our aim is to identify
AGNs and determine their fraction in this mid-infrared selected sample. In this
work, we use the [Ne V]3426 emission line to spectroscopically identify AGNs.
Combined with broad-line Type I AGNs selected in our previous study, our sample
consists of 887 (22
analysis on the remaining spectra, and find that in various MIR-wedge-selected
AGN candidates, the stacked spectra still show significant [Ne V]3426 emission,
In contrast, no clear [Ne V]3426 signal is detected in non-AGN candidates
falling outside the wedges. Assuming a range of AGN mid-IR SED slope of 0.3<
alpha <0.7, and an average star-forming relation derived from 65 star-forming
templates, we develop a robust method to separate the AGN and star-forming
contributions to the mid-IR SEDs using the rest-frame L12 /L1.6 vs L4.5 /L1.6
diagram. We separate the objects into bins of L12 , and find that AGN fraction
increases with increasing L12. We also find that the stacked [Ne V]3426
strength scales with L12 . The pure AGN luminosity at 12 um exhibits a positive
correlation with the star formation rates, indicating possible co-evolution and
common gas supply between the AGN and their host galaxies. Varying population
properties across the redshift range explored contribute to the observed
correlation.
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关键词
Active galactic nuclei,Galaxy spectroscopy,Infrared galaxies,AGN host galaxies
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