Near-Infrared Spectroscopy of Low-Redshift Palomar-Green Quasars and Composite Spectra
Abstract
The Palomar-Green (PG) Quasars have been used extensively to establish the spectral properties of luminous active galactic nuclei (AGNs) at low redshifts in many wavebands, but not the near-infrared (NIR). We present NIR spectra of all 87 PG quasars with z < 0.5 observed with the Apache Point Observatory 3.5-m telescope and the TripleSpec spectrograph in standard cross-dispersed mode. Here we employ our data set to construct a NIR composite quasar spectrum spanning rest-frame wavelengths from approximately 8800-22000 angstroms reaching a signal-to-noise ratio of several hundred in the H-band for 4 angstrom pixels. We characterize the continuum and emission-line properties of this composite. Additionally, we construct composite spectra as a function of luminosity and Eddington ratio, finding some differences, not entirely unexpected. In particular, more luminous composite NIR spectra grow increasingly red at long wavelengths, consistent with relatively stronger dust emission at higher temperatures.
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BibTeX
@misc{cavanaugh2026nearinfrared,
title = {{Near-Infrared Spectroscopy of Low-Redshift Palomar-Green Quasars and Composite Spectra}},
author = {Amy Cavanaugh and Michael Brotherton and Jacob McLane and Richard Green},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.27773},
eprint = {2608.27773},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.27773},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Near-Infrared Spectroscopy of Low-Redshift Palomar-Green Quasars and Composite Spectra
AU - Amy Cavanaugh
AU - Michael Brotherton
AU - Jacob McLane
AU - Richard Green
PY - 2026
DA - 2026/08/27
PB - arXiv
DO - 10.48550/arxiv.2608.27773
UR - https://arxiv.org/abs/2608.27773
AB - The Palomar-Green (PG) Quasars have been used extensively to establish the spectral properties of luminous active galactic nuclei (AGNs) at low redshifts in many wavebands, but not the near-infrared (NIR). We present NIR spectra of all 87 PG quasars with z < 0.5 observed with the Apache Point Observatory 3.5-m telescope and the TripleSpec spectrograph in standard cross-dispersed mode. Here we employ our data set to construct a NIR composite quasar spectrum spanning rest-frame wavelengths from approximately 8800-22000 angstroms reaching a signal-to-noise ratio of several hundred in the H-band for 4 angstrom pixels. We characterize the continuum and emission-line properties of this composite. Additionally, we construct composite spectra as a function of luminosity and Eddington ratio, finding some differences, not entirely unexpected. In particular, more luminous composite NIR spectra grow increasingly red at long wavelengths, consistent with relatively stronger dust emission at higher temperatures.
ER -