Near-infrared emission line diagnostics for AGN from the local Universe to z~3. (2023)
Keywords :
ISM galaxies - galaxies: high-redshift - galaxies: evolution - galaxies: Seyfert - galaxies: active
Abstract:Optical rest-frame spectroscopic diagnostics are usually employed to distinguish between star formation and active galactic nucleus (AGN) powered emission. However, this method is biased against dusty sources, hampering a complete census of the AGN population across cosmic epochs. To mitigate th is effect, it is crucial to observe at longer wavelengths in the rest-frame near-infrared (near-IR), which is less affected by dust attenuation and can thus provide a better description of the intrinsic properties of galaxies. AGN diagnostics in this regime have not been fully exploited so far, due to the scarcity of near-IR observations of both AGNs and star-forming galaxies, especially at redshifts higher than 0.5. Using Cloudy
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Measurements of emission lines from fully calibrated spectra observed
with JWST/NIRSpec in M-grating mode (R=1000) for 90 emission line
galaxies in CEERS in the redshift range 1<z<3. The emission lines are
modeled as Gaussians and fitted with MPFIT (Markwardt et al., 2009,
Astronomical Data Analysis Software and Systems XVIII, 411, 251
doi:10.48550/arXiv.0902.2850) following the procedure explained in
Section 2.2 of the paper. The spectroscopic redshift zspec and the
velocity width sigma of the lines are first determined from the
highest S/N emission line (typically H{alpha} or [SIII] 9530.65{AA}).
and then fixed when fitting the remaining lines, with a tolerance of
500km/s and 100km/s, respectively. The H{beta}+[OIII] line complex in
the optical is fitted simultaneously, that is, assuming a single
redshift, line velocity width, and underlying continuum in the form of
first order polynomial. The same approach is followed when fitting the
H-alpha + [NII] complex, the [SII] doublet, the HeI+Pa{gamma}
complex, and the [FeII]+Pa{beta} complex. In this table we report the
results (including redshift, flux, flux uncertainty, underlying
continuum, and line width) for the emission lines ranging from H{beta}
to Pa{alpha}.
When upper limit flag (f in f_Flux) the flux of the corresponding
emission line should be treated as an upper limit at 1sigma. For the
broad line AGNs selected in the paper, the flux, redshift, and
velocity width of permitted lines always refer to the narrow
component.
Antonello Calabro, antonello.calabro(at)inaf.it
