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Title: Half-megasecond Chandra spectral imaging of the hot circumgalactic nebula around quasar MRK 231

Abstract

A deep 400 ks ACIS-S observation of the nearest quasar known, Mrk 231, is combined with archival 120 ks data to carry out the first ever spatially resolved spectral analysis of a hot X-ray-emitting circumgalactic nebula around a quasar. The 65 × 50 kpc X-ray nebula shares no resemblance with the tidal debris seen at optical wavelengths. One notable exception is the small tidal arc ∼3.5 kpc south of the nucleus where excess soft X-ray continuum emission and Si XIII 1.8 keV line emission are detected, consistent with star formation and its associated alpha-element enhancement, respectively. An X-ray shadow is also detected at the location of the 15 kpc northern tidal tail. The hard X-ray continuum emission within ∼6 kpc of the center is consistent with being due entirely to the bright central active galactic nucleus. The soft X-ray spectrum of the outer (≳6 kpc) portion of the nebula is best described as the sum of two thermal components with temperatures ∼3 and ∼8 million K and spatially uniform super-solar alpha-element abundances, relative to iron. This result implies enhanced star formation activity over ∼10{sup 8} yr, accompanied by redistribution of the metals on a large scale. The low-temperature thermal componentmore » is not present within ∼6 kpc of the nucleus, suggesting extra heating in this region from the circumnuclear starburst, the central quasar, or the optically identified ≳3 kpc quasar-driven outflow. The soft X-ray emission is weaker in the western quadrant, coincident with a deficit of Hα and some of the largest columns of neutral gas outflowing from the nucleus. Shocks may heat the gas to high temperatures at this location, consistent with the tentative ∼2σ detection of extended Fe XXV 6.7 keV line emission.« less

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
  2. Observational Cosmology Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  3. Department of Physics, Rhodes College, Memphis, TN 38112 (United States)
  4. Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
  5. Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany)
Publication Date:
OSTI Identifier:
22365497
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DETECTION; ELEMENT ABUNDANCE; EMISSION; EXCEPTIONS; GALAXY NUCLEI; HARD X RADIATION; HEATING; IRON; KEV RANGE; NEBULAE; QUASARS; SOFT X RADIATION; SPECTRA; STARS; X-RAY GALAXIES

Citation Formats

Veilleux, S., Teng, S. H., Rupke, D. S. N., Maiolino, R., and Sturm, E., E-mail: veilleux@astro.umd.edu. Half-megasecond Chandra spectral imaging of the hot circumgalactic nebula around quasar MRK 231. United States: N. p., 2014. Web. doi:10.1088/0004-637X/790/2/116.
Veilleux, S., Teng, S. H., Rupke, D. S. N., Maiolino, R., & Sturm, E., E-mail: veilleux@astro.umd.edu. Half-megasecond Chandra spectral imaging of the hot circumgalactic nebula around quasar MRK 231. United States. doi:10.1088/0004-637X/790/2/116.
Veilleux, S., Teng, S. H., Rupke, D. S. N., Maiolino, R., and Sturm, E., E-mail: veilleux@astro.umd.edu. Fri . "Half-megasecond Chandra spectral imaging of the hot circumgalactic nebula around quasar MRK 231". United States. doi:10.1088/0004-637X/790/2/116.
@article{osti_22365497,
title = {Half-megasecond Chandra spectral imaging of the hot circumgalactic nebula around quasar MRK 231},
author = {Veilleux, S. and Teng, S. H. and Rupke, D. S. N. and Maiolino, R. and Sturm, E., E-mail: veilleux@astro.umd.edu},
abstractNote = {A deep 400 ks ACIS-S observation of the nearest quasar known, Mrk 231, is combined with archival 120 ks data to carry out the first ever spatially resolved spectral analysis of a hot X-ray-emitting circumgalactic nebula around a quasar. The 65 × 50 kpc X-ray nebula shares no resemblance with the tidal debris seen at optical wavelengths. One notable exception is the small tidal arc ∼3.5 kpc south of the nucleus where excess soft X-ray continuum emission and Si XIII 1.8 keV line emission are detected, consistent with star formation and its associated alpha-element enhancement, respectively. An X-ray shadow is also detected at the location of the 15 kpc northern tidal tail. The hard X-ray continuum emission within ∼6 kpc of the center is consistent with being due entirely to the bright central active galactic nucleus. The soft X-ray spectrum of the outer (≳6 kpc) portion of the nebula is best described as the sum of two thermal components with temperatures ∼3 and ∼8 million K and spatially uniform super-solar alpha-element abundances, relative to iron. This result implies enhanced star formation activity over ∼10{sup 8} yr, accompanied by redistribution of the metals on a large scale. The low-temperature thermal component is not present within ∼6 kpc of the nucleus, suggesting extra heating in this region from the circumnuclear starburst, the central quasar, or the optically identified ≳3 kpc quasar-driven outflow. The soft X-ray emission is weaker in the western quadrant, coincident with a deficit of Hα and some of the largest columns of neutral gas outflowing from the nucleus. Shocks may heat the gas to high temperatures at this location, consistent with the tentative ∼2σ detection of extended Fe XXV 6.7 keV line emission.},
doi = {10.1088/0004-637X/790/2/116},
journal = {Astrophysical Journal},
number = 2,
volume = 790,
place = {United States},
year = {Fri Aug 01 00:00:00 EDT 2014},
month = {Fri Aug 01 00:00:00 EDT 2014}
}
  • 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 ∼590 AU and an orbital period of ∼1.2 years. The flat optical and UV continuamore » 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 λ ∼ 4000–2500 Å 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.« less
  • New near- and far-ultraviolet (NUV and FUV) Hubble Space Telescope spectra of Mrk 231, the nearest quasar known, are combined with ground-based optical spectra to study the remarkable dichotomy between the FUV and NUV–optical spectral regions in this object. The FUV emission-line features are faint, broad, and highly blueshifted (up to ∼7000 km s{sup −1}), with no significant accompanying absorption. In contrast, the profiles of the NUV absorption features resemble those of the optical Na i D, He i, and Ca ii H and K lines, exhibiting broad blueshifted troughs that overlap in velocity space with the FUV emission-line featuresmore » and indicate a dusty, high-density and patchy broad absorption line (BAL) screen covering ∼90% of the observed continuum source at a distance ≲2–20 pc. The FUV continuum emission does not show the presence of any obvious stellar features and is remarkably flat compared with the steeply declining NUV continuum. The NUV (FUV) features and continuum emission have not varied significantly over the past ∼22 (3) years and are unresolved on scales ∼40 (170) pc. These results favor an active galactic nucleus origin for the NUV–FUV line and continuum emission. The observed FUV line emission is produced in the outflowing BAL cloud system, while the Balmer lines arise primarily from the standard broad line region seen through the dusty BAL screen. Our data are inconsistent with the recently proposed binary black hole model. We argue instead that Mrk 231 is the nearest example of weak-lined “wind-dominated” quasars with high Eddington ratios and geometrically thick (“slim”) accretion disks; these quasars are likely more common in the early universe.« less
  • The recent discovery by Cantalupo et al. of the largest (∼500 kpc) luminous (L ≃ 1.43 × 10{sup 45} erg s{sup −1}) Lyα nebula associated with the quasar UM287 (z = 2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z ∼ 2 galaxies. Either an enormous reservoir of cool gas is required M ≃ 10{sup 12} M{sub ⊙}, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. However, observations of Lyα emission alone cannot distinguish between these two scenarios. We have obtainedmore » the deepest ever spectroscopic integrations in the He ii λ1640 and C iv λ1549 emission lines with the goal of detecting extended line emission, but detect neither line to a 3σ limiting SB ≃ 10{sup −18} erg s{sup −1} cm{sup −2} arcsec{sup −2}. We construct simple models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. The non-detection of He ii implies that the nebular emission arises from a mass M{sub c} ≲ 6.4 × 10{sup 10} M{sub ⊙} of cool gas on ∼200 kpc scales, distributed in a population of remarkably dense (n{sub H} ≳ 3 cm{sup −3}) and compact (R ≲ 20 pc) clouds, which would clearly be unresolved by current cosmological simulations. Given the large gas motions suggested by the Lyα line (v ≃ 500 km s{sup −1}), it is unclear how these clouds survive without being disrupted by hydrodynamic instabilities. Our work serves as a benchmark for future deep integrations with current and planned wide-field IFU spectrographs such as MUSE, KCWI, and KMOS. Our observations and models suggest that a ≃10 hr exposure would likely detect ∼10 rest-frame UV/optical emission lines, opening up the possibility of conducting detailed photoionization modeling to infer the physical state of gas in the circumgalactic medium.« less
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  • We report on the first high-frequency very long baseline interferometry observations of the nearby broad absorption line quasar, Mrk 231. Three epochs of observations were achieved at 15 GHz and 22 GHz, two of these included 43 GHz observations as well. The nuclear radio source is resolved as a compact double. The core component experienced a strong flare in which the flux density at 22 GHz increased by >150% (45 mJy) in three months. Theoretical models of the flare imply that the emission is likely enhanced by very strong Doppler boosting of a highly relativistic ejecta with a kinetic energymore » flux, Q approx 3 x 10{sup 43} erg s{sup -1}. Combining our data with two previous epochs of 15 GHz data shows marginal evidence for the slow advance of the secondary component (located approx0.97 pc from the core) over a 9.4 year span. We estimate that the long-term time averaged kinetic energy flux of the secondary at Q-barapprox1-{sup 42} erg s{sup -1}. Low-frequency very long baseline array observations indicate that the secondary is seen through a shroud of free-free absorbing gas with an emission measure of approx10{sup 8} cm{sup -6}. The steep spectrum secondary component appears to be a compact radio lobe that is associated with a working surface between the ram pressure confined jet and a dense medium that is likely to be the source of the free-free absorption. The properties of the dense gas are consistent with the temperatures, displacement from the nucleus, and the column density of total hydrogen commonly associated with the BAL wind.« less