# The Near and Mid-infrared photometric properties of known redshift $z\geq5$ Quasars

## TL;DR

This study compiles a large catalog of high-redshift quasars ($z extgreater=5$), analyzing their near- and mid-infrared properties, detection rates, and variability, providing valuable data for understanding early universe supermassive black holes.

## Contribution

It presents the first extensive infrared property catalog of 488 spectroscopically confirmed $z extgreater=5$ quasars, including variability analysis and detection statistics.

## Key findings

- 97% detected in NIR bands, mainly limited by coverage.
- 80% detected at 3.4μm in W1 band, all $z extgreater=7$ quasars detected in W1 and W2.
- Weak or marginal variability observed in a few quasars.

## Abstract

We assemble a catalogue of 488 spectroscopically confirmed very high ($z\geq5.00$) redshift quasars and report their near- ($ZYJHK_{s}/K$) and mid- (WISE W1234) infrared properties. 97\% of the VH$z$Q sample is detected in one or more NIR ($ZYJHK/K_{s}$) band, with lack of coverage rather than lack of depth being the reason for the non-detections. 389 (80\%) of the very high redshift quasars are detected at 3.4$\mu$m in the W1 band from the unWISE catalog and all of the $z\geq7$ quasars are detected in both unWISE W1 and W2. Using archival WFCAM/UKIRT and VIRCAM/VISTA data we check for photometric variability that might be expected from super-Eddington accretion. We find 28 of the quasars have sufficient NIR measurements and signal-to-noise ratio to look for variability. Weak variability was detected in multiple bands of SDSS J0959+0227, and very marginally in the $Y$-band of MMT J0215-0529. Only one quasar, SDSS J0349+0034, shows significant differences between WFCAM and VISTA magnitudes in one band. With supermassive black hole accretion likely to be redshift invariant up to very high-redshift, further monitoring of these sources is warranted. All the data, analysis codes and plots used and generated here can be found at: https://github.com/d80b2t/VHzQ}{\tt github.com/d80b2t/VHzQ.