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Register a new userThe Quasar SDSS J105041.35+345631.3: Black Hole Recoil or Extreme Double-Peaked Emitter?
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The quasar SDSS J105041.35+345631.3 (z = 0.272) has broad emission lines blueshifted by 3500 km/s relative to the narrow lines and the host galaxy. Such an object may be a candidate for a recoiling supermassive black hole, binary black hole, a superposition of two objects, or an unusual geometry for the broad emission-line region. The absence of narrow lines at the broad line redshift argues against superposition. New Keck spectra of J1050+3546 place tight constraints on the binary model. The combination of large velocity shift and symmetrical H-beta profile, as well as aspects of the narrow line spectrum, make J1050+3546 an interesting candidate for black hole recoil. Other aspects of the spectrum, however, suggest that the object is most likely an extreme case of a ``double-peaked emitter. We discuss possible observational tests to determine the true nature of this exceptional object.
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The quasar SDSS J153636.22+044127.0, exhibiting peculiar broad emission-line profiles with multiple components, was proposed as a candidate sub-parsec binary supermassive black hole system. More recently, imaging revealed two spatially distinct sources, leading some to suggest the system to be a quasar pair separated by ~5 kpc. We present Palomar and Keck optical spectra of this system from which we identify a third velocity component to the emission lines. We argue that the system is more likely an unusual member of the class of active galactic nuclei (AGNs) known as double-peaked emitters than a sub-parsec black hole binary or quasar pair. We find no significant velocity evolution of the two main peaks over the course of 0.95 yr, with a 3-sigma upper limit on any secular change of 70 km/s/yr. We also find that the three velocity components of the emission lines are spatially coincident to within 0.015 along the slit, apparently ruling out the double-quasar hypothesis.
SDSS J092712.65+294344.0 has been proposed as a candidate for a supermassive black hole (~10^8.8 solar masses) ejected at high speed from the host galactic nucleus by gravitational radiation recoil, or alternatively for a supermassive black hole binary. This is based on a blueshift of 2650 km/s of the broad emission lines (b-system) relative to the narrow emission lines (r-system) presumed to reflect the galaxy velocity. New observations with the Hobby-Eberly Telescope (HET) confirm the essential features of the spectrum. We note a third redshift system, characterized by weak, narrow emission lines of [O III] and [O II] at an intermediate velocity 900 km/s redward of the broad line velocity (i-system). A composite spectrum of SDSS QSOs similar to J0927 illustrates the feasibility of detecting the calcium K absorption line in spectra of sufficient quality. The i-system may represent the QSO host galaxy or a companion. Photoionization requires the black hole to be ~3 kpc from the r-system emitting gas, implying that we are observing the system only 10^6 yr after the recoil event and contributing to the low probability of observing such a system. The HET observations give an upper limit of 10 km/s per year on the rate of change of the velocity difference between the r- and b-systems, constraining the orbital phase in the binary model. These considerations and the presence of a cluster of galaxies apparently containing J0927 favor the idea that this system represents a superposition of two AGN.
We present a detailed study of a peculiar source in the COSMOS survey at z=0.359. Source CXOCJ100043.1+020637 (CID-42) presents two compact optical sources embedded in the same galaxy. The distance between the 2, measured in the HST/ACS image, is 0.495 that, at the redshift of the source, corresponds to a projected separation of 2.46 kpc. A large (~1200 km/s) velocity offset between the narrow and broad components of Hbeta has been measured in three different optical spectra from the VLT/VIMOS and Magellan/IMACS instruments. CID-42 is also the only X-ray source having in its X-ray spectra a strong redshifted broad absorption iron line, and an iron emission line, drawing an inverted P-Cygni profile. The Chandra and XMM data show that the absorption line is variable in energy by 500 eV over 4 years and that the absorber has to be highly ionized, in order not to leave a signature in the soft X-ray spectrum. That these features occur in the same source is unlikely to be a coincidence. We envisage two possible explanations: (1) a gravitational wave recoiling black hole (BH), caught 1-10 Myr after merging, (2) a Type 1/ Type 2 system in the same galaxy where the Type 1 is recoiling due to slingshot effect produced by a triple BH system. The first possibility gives us a candidate gravitational waves recoiling BH with both spectroscopic and imaging signatures. In the second case, the X-ray absorption line can be explained as a BAL-like outflow from the foreground nucleus (a Type 2 AGN) at the rearer one (a Type 1 AGN), which illuminates the otherwise undetectable wind, giving us the first opportunity to show that fast winds are present in obscured AGN.
In this manuscript, an interesting blue Active Galactic Nuclei (AGN) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H$beta$ but single-peaked broad H$alpha$. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical conditions to two central BLRs in a central BBH system in SDSS J1547. Furthermore, the long-term light curve from CSS can be well described by a sinusoidal function with a periodicity about 2159days, providing further evidence to support the expected central BBH system in SDSS J1547. Therefore, it is interesting to treat different line profiles of broad Balmer emission lines as intrinsic indicators of central BBH systems in broad line AGN. Under assumptions of BBH systems, 0.125% of broad line AGN can be expected to have very different line profiles of broad Balmer emission lines. Future study on more broad line AGN with very different line profiles of broad Balmer emission lines could provide further clues on the different line profiles of broad Balmer emission lines as indicator of BBH systems.
Several active galactic nuclei (AGN) with multiple sets of emission lines separated by over 2000 km/s have been observed recently. These have been interpreted as being due to massive black hole (MBH) recoil following a black hole merger, MBH binaries, or chance superpositions of AGN in galaxy clusters. Moreover, a number of double-peaked AGN with velocity offsets of ~ a few 100 km/s have also been detected and interpreted as being due to the internal kinematics of the narrow line regions or MBH binary systems. Here we reexamine the superposition model. Using the Millennium Run we estimate the total number of detectable AGN pairs as a function of the emission line offset. We show that AGN pairs with high velocity line separations up to ~2000 km/s are very likely to be chance superpositions of two AGN in clusters of galaxies for reasonable assumptions about the relative fraction of AGN. No superimposed AGN pairs are predicted for velocity offsets in excess of ~3000 km/s as the required AGN fractions would violate observational constraints. The high velocity AGN pair numbers predicted here are competitive with those predicted from the models relying on MBH recoil or MBH binaries. However, the model fails to account for the largest emission line velocity offsets that require the presence of MBH binaries.
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