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Register a new userMolecular Oxygen in the nearest QSO Mrk 231
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We report the detection of an emission feature at the 12 sigma level with FWHM line width of about 450 km/s toward the nearest quasi-stellar object, QSO Mrk 231. Based on observations with the IRAM 30 m telescope and the NOEMA Interferometer, the 11-10 transition of molecular oxygen is the likely origin of line with rest frequency close to 118.75 GHz. The velocity of the O2 emission in Mrk 231 coincides with the red wing seen in CO emission, suggesting that it is associated with the outflowing molecular gas, located mainly at about ten kpc away from the central AGN. This first detection of extragalactic molecular oxygen provides an ideal tool to study AGN-driven molecular outflows on dynamic time scales of tens of Myr. O2 may be a significant coolant for molecular gas in such regions affected by AGN-driven outflows. New astrochemical models are needed to explain the implied high molecular oxygen abundance in such regions several kpc away from the center of galaxies.
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We report on the Herschel/PACS observations of OH in Mrk 231, with detections in 9 doublets observed within the PACS range, and present radiative transfer models for the outflowing OH. Signatures of outflowing gas are found in up to 6 OH doublets with different excitation requirements. At least two outflowing components are identified, one with OH radiatively excited, and the other with low excitation, presumably spatially extended. Particularly prominent, the blue wing of the absorption detected in the in-ladder 2Pi_{3/2} J=9/2-7/2 OH doublet at 65 um, with E_lower=290 K, indicates that the excited outflowing gas is generated in a compact and warm (circum)nuclear region. Because the excited, outflowing OH gas in Mrk 231 is associated with the warm, far-IR continuum source, it is likely more compact (diameter of 200-300 pc) than that probed by CO and HCN. Nevertheless, its mass-outflow rate per unit of solid angle as inferred from OH is similar to that previously derived from CO, >~70x(2.5x10^{-6}/X_{OH}) Msun yr^{-1} sr^{-1}, where X_{OH} is the OH abundance relative to H nuclei. In spherical symmetry, this would correspond to >~850x(2.5x10^{-6}/X_{OH}) Msun yr^{-1}, though significant collimation is inferred from the line profiles. The momentum flux of the excited component attains ~15 L_{AGN}/c, with an OH column density of (1.5-3)x10^{17} cm^-2 and a mechanical luminosity of ~10^{11} Lsun. The detection of very excited OH peaking at central velocities indicates the presence of a nuclear reservoir of gas rich in OH, plausibly the 130-pc scale circumnuclear torus previously detected in OH megamaser emission, that may be feeding the outflow. An exceptional ^{18}OH enhancement, with OH/^{18}OH<~30 at both central and blueshifted velocities, is likely the result of interstellar-medium processing by recent starburst/SNe activity.
The quasi-stellar object (QSO)/merger Mrk 231 is arguably the nearest and best laboratory for studying QSO feedback. It hosts several outflows, including broad-line winds, radio jets, and a poorly-understood kpc scale outflow. In this Letter, we present integral field spectroscopy from the Gemini telescope that represents the first unambiguous detection of a wide-angle, kpc scale outflow from a powerful QSO. Using neutral gas absorption, we show that the nuclear region hosts an outflow with blueshifted velocities reaching 1100 km/s, extending 2-3 kpc from the nucleus in all directions in the plane of the sky. A radio jet impacts the outflow north of the nucleus, accelerating it to even higher velocities (up to 1400 km/s). Finally, 3.5 kpc south of the nucleus, star formation is simultaneously powering an outflow that reaches more modest velocities of only 570 km/s. Blueshifted ionized gas is also detected around the nucleus at lower velocities and smaller scales. The mass and energy flux from the outflow are >~2.5 times the star formation rate and >~0.7% of the active galactic nucleus luminosity, consistent with negative feedback models of QSOs.
Supermassive binary black holes (BBHs) are unavoidable products of galaxy mergers and are expected to exist in the cores of many quasars. Great effort has been made during the past several decades to search for BBHs among quasars; however, observational evidence for BBHs remains elusive and ambiguous, which is difficult to reconcile with theoretical expectations. In this paper, we show that the distinct optical-to-UV spectrum of Mrk 231 can be well interpreted as emission from accretion flows onto a BBH, with a semimajor axis of ~590AU and an orbital period of ~1.2 year. The flat optical and UV continua are mainly emitted from a circumbinary disk and a mini-disk around the secondary black hole (BH), respectively; and the observed sharp drop off and flux deficit at wavelength lambda ~ 4000-2500 Angstrom is due to a gap (or hole) opened by the secondary BH migrating within the circumbinary disk. If confirmed by future observations, this BBH will provide a unique laboratory to study the interplay between BBHs and accretion flows onto them. Our result also demonstrates a new method to find sub-parsec scale BBHs by searching for deficits in the optical-to-UV continuum among the spectra of quasars.
Aims: Our goal is to study the chemical composition of the outflows of active galactic nuclei and starburst galaxies. Methods: We obtained high-resolution interferometric observations of HCN and HCO$^+$ $J=1rightarrow0$ and $J=2rightarrow1$ of the ultraluminous infrared galaxy Mrk~231 with the IRAM Plateau de Bure Interferometer. We also use previously published observations of HCN and HCO$^+$ $J=1rightarrow0$ and $J=3rightarrow2$, and HNC $J=1rightarrow0$ in the same source. Results: In the line wings of the HCN, HCO$^+$, and HNC emission, we find that these three molecular species exhibit features at distinct velocities which differ between the species. The features are not consistent with emission lines of other molecular species. Through radiative transfer modelling of the HCN and HCO$^+$ outflow emission we find an average abundance ratio $X(mathrm{HCN})/X(mathrm{HCO}^+)gtrsim1000$. Assuming a clumpy outflow, modelling of the HCN and HCO$^+$ emission produces strongly inconsistent outflow masses. Conclusions: Both the anti-correlated outflow features of HCN and HCO$^+$ and the different outflow masses calculated from the radiative transfer models of the HCN and HCO$^+$ emission suggest that the outflow is chemically differentiated. The separation between HCN and HCO$^+$ could be an indicator of shock fronts present in the outflow, since the HCN/HCO$^+$ ratio is expected to be elevated in shocked regions. Our result shows that studies of the chemistry in large-scale galactic outflows can be used to better understand the physical properties of these outflows and their effects on the interstellar medium (ISM) in the galaxy.
We present the results of a multi-frequency, multi-scale radio polarimetric study with the Very Large Array (VLA) of the Seyfert 1 galaxy and BALQSO, Mrk 231. We detect complex total and polarized intensity features in the source. Overall, the images indicate the presence of a broad, one-sided, curved outflow towards the south which consists of a weakly collimated jet with poloidal inferred magnetic fields, inside a broader magnetized ``wind or ``sheath component with toroidal inferred magnetic fields. The model of a kpc-scale weakly collimated jet/lobe in Mrk 231 is strengthened by its C-shaped morphology, steep spectral index throughout, complexities in the magnetic field structures, and the presence of self-similar structures observed on the 10-parsec-scale in the literature. The ``wind may comprise both nuclear starburst (close to the core) and AGN winds, where the latter maybe the primary contributor. Moving away from the core, the ``wind component may also comprise the outer layers (or ``sheath) of a broadened jet. The inferred value of the (weakly collimated) jet production efficiency, $eta_mathrm{jet}sim$0.01 is consistent with the estimates in the literature. The composite jet and wind outflow in Mrk 231 appears to be low-power and matter-dominated, and oriented at a small angle to our line of sight.
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