A large systematic search for close supermassive binary and rapidly recoiling black holes

Michael Eracleous, Todd A. Boroson, Jules P. Halpern, Jia Liu

Research output: Contribution to journalReview article

89 Citations (Scopus)

Abstract

We have carried out a systematic search for subparsec supermassive black hole (BH) binaries among z ≲ 0.7 Sloan Digital Sky Survey quasars. These are predicted by models of supermassive BH and host galaxy coevolution, therefore their census and population properties constitute an important test of these models. In our working hypothesis, one of the two BHs accretes at a much higher rate than the other and carries with it the only broad emission line region of the system, making the system analogous to a single-lined spectroscopic binary star. Accordingly, we used spectroscopic principal component analysis to search for broad Hβ emission lines that are displaced from the quasar rest frame by |Δ v| ≳ 1000 km s -1. This method also yields candidates for rapidly recoiling BHs. Of the 88 candidates, several were previously reported in the literature. We found a correlation between the peak offset and skewness of the broad Hβ profiles, suggesting a common physical explanation for these profiles. We carried out follow-up spectroscopic observations of 68 objects to search for changes in the peak velocities of the Hβ lines. We measured statistically significant changes in 14 objects, with implied accelerations between -120 and +120kms -1 yr -1. Interpreting the offset broad emission lines as signatures of supermassive binaries is subject to many caveats. Many more follow-up observations over a long temporal baseline are needed to characterize the variability pattern of the broad lines and test that it is consistent with orbital motion. The possibility that some of the objects in this sample are rapidly recoiling BHs remains open.

Original languageEnglish (US)
Article number23
JournalAstrophysical Journal, Supplement Series
Volume201
Issue number2
DOIs
StatePublished - Aug 1 2012

Fingerprint

recoilings
quasars
H lines
census
skewness
binary stars
coevolution
profiles
principal components analysis
principal component analysis
signatures
galaxies
orbits
test

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "A large systematic search for close supermassive binary and rapidly recoiling black holes",
abstract = "We have carried out a systematic search for subparsec supermassive black hole (BH) binaries among z ≲ 0.7 Sloan Digital Sky Survey quasars. These are predicted by models of supermassive BH and host galaxy coevolution, therefore their census and population properties constitute an important test of these models. In our working hypothesis, one of the two BHs accretes at a much higher rate than the other and carries with it the only broad emission line region of the system, making the system analogous to a single-lined spectroscopic binary star. Accordingly, we used spectroscopic principal component analysis to search for broad Hβ emission lines that are displaced from the quasar rest frame by |Δ v| ≳ 1000 km s -1. This method also yields candidates for rapidly recoiling BHs. Of the 88 candidates, several were previously reported in the literature. We found a correlation between the peak offset and skewness of the broad Hβ profiles, suggesting a common physical explanation for these profiles. We carried out follow-up spectroscopic observations of 68 objects to search for changes in the peak velocities of the Hβ lines. We measured statistically significant changes in 14 objects, with implied accelerations between -120 and +120kms -1 yr -1. Interpreting the offset broad emission lines as signatures of supermassive binaries is subject to many caveats. Many more follow-up observations over a long temporal baseline are needed to characterize the variability pattern of the broad lines and test that it is consistent with orbital motion. The possibility that some of the objects in this sample are rapidly recoiling BHs remains open.",
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A large systematic search for close supermassive binary and rapidly recoiling black holes. / Eracleous, Michael; Boroson, Todd A.; Halpern, Jules P.; Liu, Jia.

In: Astrophysical Journal, Supplement Series, Vol. 201, No. 2, 23, 01.08.2012.

Research output: Contribution to journalReview article

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AU - Liu, Jia

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