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Host Dark Matter Halos of SDSS Red and Blue Quasars: No Significant Difference in Large-scale Environment

Petter, Grayson C.; Hickox, Ryan C.; Alexander, David M.; Geach, James E.; Myers, Adam D.; Rosario, David J.; Fawcett, Victoria A.; Klindt, Lizelke; Whalen, Kelly E.

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Grayson C. Petter

Ryan C. Hickox

James E. Geach

Adam D. Myers

David J. Rosario

Victoria A. Fawcett

Lizelke Klindt

Kelly E. Whalen


The observed optical colors of quasars are generally interpreted in one of two frameworks: unified models that attribute the color to the random orientation of the accretion disk along the line of sight, and evolutionary models that invoke connections between quasar systems and their environments. We test these schemas by probing the dark matter halo environments of optically selected quasars as a function of g − i optical color by measuring the two-point correlation functions of ∼0.34 million eBOSS quasars as well as the gravitational deflection of cosmic microwave background photons around ∼0.66 million XDQSO photometric quasar candidates. We do not detect a trend of halo bias with optical color through either analysis, finding that optically selected quasars at 0.8 < z < 2.2 occupy halos of characteristic mass Mh ∼ 3 × 1012 h−1 M⊙ regardless of their color. This result implies that a quasar's large-scale halo environment is not strongly connected to its observed optical color. We also confirm the findings of fundamental differences in the radio properties of red and blue quasars by stacking 1.4 GHz FIRST images at their positions, suggesting the observed differences cannot be attributed to orientation. Instead, the differences between red and blue quasars likely arise on nuclear-galactic scales, perhaps owing to reddening by a nuclear dusty wind. Finally, we show that optically selected quasars' halo environments are also independent of their r − W2 optical–infrared colors, while previous work has suggested that mid-infrared-selected obscured quasars occupy more massive halos. We discuss the implications of this result for models of quasar and galaxy coevolution.


Petter, G. C., Hickox, R. C., Alexander, D. M., Geach, J. E., Myers, A. D., Rosario, D. J., …Whalen, K. E. (2022). Host Dark Matter Halos of SDSS Red and Blue Quasars: No Significant Difference in Large-scale Environment. Astrophysical Journal, 927(1), Article 16.

Journal Article Type Article
Acceptance Date Jan 18, 2022
Online Publication Date Mar 2, 2022
Publication Date Mar 1, 2022
Deposit Date Jun 13, 2022
Publicly Available Date Jun 13, 2022
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 927
Issue 1
Article Number 16
Public URL


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Copyright Statement
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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