A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes -- IV. Ultraviolet spectroscopy

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Main Authors: Runnoe, Jessie C., Eracleous, Michael, Bogdanović, Tamara, Halpern, Jules, Sigurðsson, Steinn
Format: Preprint
Published: 2025
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_version_ 1866913655558242304
author Runnoe, Jessie C.
Eracleous, Michael
Bogdanović, Tamara
Halpern, Jules
Sigurðsson, Steinn
author_facet Runnoe, Jessie C.
Eracleous, Michael
Bogdanović, Tamara
Halpern, Jules
Sigurðsson, Steinn
contents We present Hubble Space Telescope ultraviolet (UV) of 13 quasars at z<0.7, along with contemporaneous optical spectra from ground-based telescopes. The targets were selected to have broad H-beta emission lines with substantial velocity offsets relative to the rest frame of their host galaxy. By analogy to single-line spectroscopic binary stars, these objects have been regarded as supermassive black hole binary (SBHB) candidates where the offset emission lines may be caused by bulk orbital motion. The best alternative explanation is that the H-beta line profile is the result of non-axisymmetric emission from a disk-like broad-line region associated with a single supermassive black hole. We use the broad UV line profiles to discriminate between these two scenarios. We describe our methodology for isolating the broad optical and UV line profiles and the criteria we apply for comparing them. Of the 13 SBHB candidates, three have strong evidence in support of the SBHB hypothesis, five have tentative support, one is disfavored, and four have such severely absorbed UV line profiles that the results are inconclusive.
format Preprint
id arxiv_https___arxiv_org_abs_2501_10574
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes -- IV. Ultraviolet spectroscopy
Runnoe, Jessie C.
Eracleous, Michael
Bogdanović, Tamara
Halpern, Jules
Sigurðsson, Steinn
Astrophysics of Galaxies
High Energy Astrophysical Phenomena
We present Hubble Space Telescope ultraviolet (UV) of 13 quasars at z<0.7, along with contemporaneous optical spectra from ground-based telescopes. The targets were selected to have broad H-beta emission lines with substantial velocity offsets relative to the rest frame of their host galaxy. By analogy to single-line spectroscopic binary stars, these objects have been regarded as supermassive black hole binary (SBHB) candidates where the offset emission lines may be caused by bulk orbital motion. The best alternative explanation is that the H-beta line profile is the result of non-axisymmetric emission from a disk-like broad-line region associated with a single supermassive black hole. We use the broad UV line profiles to discriminate between these two scenarios. We describe our methodology for isolating the broad optical and UV line profiles and the criteria we apply for comparing them. Of the 13 SBHB candidates, three have strong evidence in support of the SBHB hypothesis, five have tentative support, one is disfavored, and four have such severely absorbed UV line profiles that the results are inconclusive.
title A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes -- IV. Ultraviolet spectroscopy
topic Astrophysics of Galaxies
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2501.10574