Absence of radio-bright dominance in a near-infrared selected sample of red quasars
arxiv(2024)
Abstract
(Abridged). We explore the fraction of radio loud quasars in the eHAQ+GAIA23
sample, which contains quasars from the High A(V) Quasar (HAQ) Survey, the
Extended High A(V) Quasar (eHAQ) Survey, and the Gaia quasar survey. All
quasars in this sample have been found using a near-infrared color selection of
target candidates that have otherwise been missed by the Sloan Digital Sky
Survey (SDSS). We implemented a redshift-dependent color cut in g-i to select
red quasars in the sample and divided them into redshift bins, while using a
nearest-neighbors algorithm to control for luminosity and redshift differences
between our red quasar sample and a selected blue sample from the SDSS. Within
each bin, we cross-matched the quasars to the Faint Images of the Radio Sky at
Twenty centimeters (FIRST) survey and determined the radio-detection fraction.
We find similar radio-detection fractions for red and blue quasars within 1
sigma, independent of redshift. This disagrees with what has been found in the
literature for red quasars in SDSS. It should be noted that the fraction of
broad absorption line (BAL) quasars in red SDSS quasars is about five times
lower than in our sample. BAL quasars have been observed to be more frequently
radio quiet than other quasars, therefore the difference in BAL fractions could
explain the difference in radio-detection fraction. The observed higher
proportion of BAL quasars in our dataset relative to the SDSS sample, along
with the higher rate of radio detections, indicates an association of the
redness of quasars and the inherent BAL fraction within the overall quasar
population. This finding highlights the need to explore the underlying factors
contributing to both the redness and the frequency of BAL quasars, as they
appear to be interconnected phenomena.
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