INSPIRALLING SUPERMASSIVE BLACK HOLES: A NEW SIGNPOST FOR GALAXY MERGERS

By J. Comerford, B. Gerke, J. Newman, M. Davis, R. Yan, M. Cooper, S. Faber, D. Koo, A. Coil, D. Rosario and 1 more. 2008

149 citations recorded by the source corpus.

We present a new technique for observationally identifying galaxy mergers spectroscopically rather than through host galaxy imaging. Our technique exploits the dynamics of supermassive black holes (SMBHs) powering active galactic nuclei (AGNs) in merger-remnant galaxies. Because structure in the universe is built up through galaxy mergers and nearly all galaxies host a central SMBH, some galaxies should possess two SMBHs near their centers as the result of a recent merger. These SMBHs spiral to the center of the resultant merger-remnant galaxy, and one or both of the SMBHs may power AGNs. Using the DEEP2 Galaxy Redshift Survey, we have examined 1881 red galaxies, of which 91 exhibit [O iii] and Hβ emission lines indicative of Seyfert 2 activity. Of these, 32 AGNs have [O iii] emission-line redshifts significantly different from the redshifts of the host galaxies' stars, corresponding to velocity offsets of ∼50 km s−1 to ∼300 km s−1. Two of these AGNs exhibit double-peaked [O iii] emission lines, while the remaining 30 AGNs each exhibit a single set of velocity-offset [O iii] emission lines. After exploring a variety of physical models for these velocity offsets, we argue that the most likely explanation is inspiralling SMBHs in merger-remnant galaxies. Based on this interpretation, we find that roughly half of the red galaxies hosting AGNs are also merger remnants, which implies that mergers may trigger AGN activity in red galaxies. The AGN velocity offsets we find imply a merger fraction of ∼30% and a merger rate of ∼3 mergers Gyr−1 for red galaxies at redshifts 0.34 < z < 0.82.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a2b6abe3fca48a4ff39544cf80f780398d794429

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Citations in the corpus

MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE (2010, background): “…better than the apparent order-of-magnitude scatterin predictions (see e.g. Kartaltepe et al. 2007; Lin et al. 2008; Domingue et al. 2009; Bundy et al. 2009; Conselice et al. 2009; Robaina et al. 2009, 2010; Comerford et al. 2009; Lotz et al. 2008b; Bridge et al. 2007; López-Sanjuan et al. 2009b).”
A LARGE SYSTEMATIC SEARCH FOR CLOSE SUPERMASSIVE BINARY AND RAPIDLY RECOILING BLACK HOLES (2011, unknown): “…could arise in biconical outflows from single active nuclei (see Crenshaw et al. 2010), some of them turn out to trace dual active nuclei in merging galaxies, as shown by followup studies (e.g., Comerford et al. 2009a,b; Liu et al. 2010a,b; Shen et al. 2010b; Smith et al. 2010b; Fu et al. 2010).”
A SEARCH FOR BINARY ACTIVE GALACTIC NUCLEI: DOUBLE-PEAKED [O iii] AGNs IN THE SLOAN DIGITAL SKY SURVEY (2009, methodology): “Additional examples of optically resolved binary AGNs include a z = 0.36 galaxy from the COSMOS survey with a spacing of 2.5 kpc (Comerford et al. 2009b) and a z = 0.44 binary quasar with a spacing of 21 kpc (Green et al. 2010).”
The cosmic evolution of massive black holes in the Horizon-AGN simulation (2016, result): “Observational searches, instead, are based on selecting for a velocity shift caused by Doppler motion in the AGN and galaxy spectra (Comerford et al. 2009), therefore our results should be only taken as an indication of astrophysical trends rather than a prediction directly comparable to…”
UNDERSTANDING DUAL ACTIVE GALACTIC NUCLEUS ACTIVATION IN THE NEARBY UNIVERSE (2012, result): “We also find a higher total fraction of dual AGN compared to dual AGN studies using the double peaked method (Comerford et al. 2009).”
FEEDBACK IN LUMINOUS OBSCURED QUASARS (2011, background): “Other candidates have been identified based on spatially offset nuclei (Barthet al. 2008; Comerford et al. 2009a).”
What drives the growth of black holes (2011, background): “On the basis of the incidence of double-peaked emission lines, Comerford et al. (2009) estimated a ≈ 30% merger fraction, similar to the upper end of merger fractions estimated from imaging data.”
Quasar feedback and the origin of radio emission in radio-quiet quasars (2014, background): “…usually requires follow-up observations at high spatial resolution, and the relative frequency of these scenarios remains a matter of debate (Comerford et al. 2009; Liu et al. 2010; Shen et al. 2010; Fu et al. 2012; Barrows et al. 2013; Blecha et al. 2013), but it appears that outflows…”
THE DEEP2 GALAXY REDSHIFT SURVEY: DESIGN, OBSERVATIONS, DATA REDUCTION, AND REDSHIFTS (2012, background): “…matches red sequence quenching rate after z∼ 1 Montero-Dorta et al. (2009) Numbers and environments of red sequence Seyferts and LINERS evolve after z∼ 1 Comerford et al. (2009) Thirty-two candidate in-spiraling supermassive black holes Yan et al. (2011) Fractions of obscured and Compton-thick AGN…”