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OVI Asymmetry and an Accelerated Outflow in an Obscured Seyfert: FUSE and HST STIS Spectroscopy of Markarian533

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Prajval Shastri, John Hutchings, Jayant Murthy, Mark Whittle, Beverley J. Wills

Astrophysics · Submitted 31 Mar 2006 · 35 references

Pith's verdict: A careful single-object FUSE/STIS study that delivers a credible O VI doublet-ratio measurement and a plausible but not uniquely supported acceleration inference.

T0 · AI review

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arXiv IDastro-ph/0603842 (version 1)
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CitationBeverley J. Wills, Jayant Murthy, John Hutchings, Mark Whittle, Prajval Shastri. "OVI Asymmetry and an Accelerated Outflow in an Obscured Seyfert: FUSE and HST STIS Spectroscopy of Markarian533." arXiv:astro-ph/0603842 (2006). https://pith.science/paper/KISNKUPY
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The paper

The paper claims

The gas outflow in the Seyfert 2 galaxy Mrk 533 accelerates as it moves outward, with the highest-ionization O VI line confined to the inner 30 parsecs while [O III] reaches about -2000 km/s at 50-100 parsecs.

The reading

This paper tries to establish that the narrow-line gas in the Seyfert 2 galaxy Mrk 533 is not just outflowing but accelerating: near the nucleus the O VI and the core of [O III] move at only a few hundred km/s, while 50–100 pc away the [O III] develops a wing to about -2000 km/s. The authors read this as a single outflow whose receding side is hidden, accelerated by a nuclear wind or jet. If correct, it gives a direct look at how AGN winds deposit momentum in the host galaxy's inner few hundred parsecs. It also shows that the highest-ionization gas stays close to the nucleus, because the fast outer gas emits no O VI, which they take as evidence that the outflow is photoionized rather than shock-ionized.

What carries the argument

The central object is the comparison between two velocity profiles: the FUSE large-aperture O VI profile and the spatially resolved [O III] lambda 5007 profiles extracted from the STIS slit at the continuum maximum and 0.1–0.2 arcsec off-nucleus along the radio axis. This spatial-velocity ladder is what lets the authors separate the inner, mildly outflowing high-ionization gas from the outer, accelerated low-ionization gas; the O VI doublet ratio serves as an optical-depth check on the inner region.

Extended reading notes

Core claim

The central discovery is a spatial-velocity sequence in the emission-line gas. In the FUSE far-UV spectrum, the O VI lambda-lambda 1032,1038 doublet is narrow, centered near the systemic velocity of 8659 km/s, and has only a moderate shortward asymmetry; the doublet intensity ratio is about 1, which the authors take to mean the emission is optically thick. In the HST STIS spectrum, the [O III] lambda 5007 profile on the continuum peak matches this O VI profile and arises within about 0.05 arcsec (about 30 pc) of the nucleus, with a peak at systemic and a blue shoulder near -100 km/s. But only 0.1–0.2 arcsec (50–100 pc) to the northwest, along the radio axis, the [O III] peak shifts to about +200 km/s and a strong wing extends to about -2000 km/s. The authors conclude that the innermost region is in mild outflow at a few hundred km/s with its receding side hidden, while beyond about 30 pc the gas has been strongly accelerated by a nuclear wind or jet; the absence of O VI in the fast gas indicates that this gas is photoionized by the central source rather than shock-ionized.

Load-bearing premise

The argument assumes the gas seen at 30 pc and at 50–100 pc is one continuous outflow viewed from one side, so the rising velocity with radius is acceleration rather than unrelated kinematic components.

Editorial extensions

If this is right

  • Above about 30 pc the outflow is accelerating, so the kinetic energy and momentum injected into the host galaxy grow with radius rather than being fixed at launch.
  • The hidden receding side of the outflow means the observed blue wings and one-sided [O III] morphology are natural consequences of torus or dust obscuration, not of intrinsic asymmetry in the wind.
  • The O VI emission is confined within about 30 pc and is optically thick, so far-UV O VI profiles in Seyfert 2s trace only the innermost narrow-line region.
  • The absence of O VI in the fastest gas argues that the high-velocity component is photoionized, not shock-ionized, constraining the ionization mechanism of AGN outflows.
  • The profile differences predict that other Seyfert 2s viewed through their tori should show similarly narrow, symmetric O VI cores with blue wings only in lower-ionization lines.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If this acceleration pattern is generic, high-spatial-resolution IFU surveys of Seyfert 2s should find the same velocity gradient: a few hundred km/s at the nucleus growing to about 2000 km/s within 100 pc; that would turn a single-object result into a class property.
  • The hidden receding side predicts a specific dust geometry; subarcsecond mid-infrared imaging could locate the obscuring material and test whether it is a torus or clumpy dust.
  • A direct test would be to search for O VI absorption or emission in the off-nuclear 50–100 pc gas with a narrow slit; detecting it would weaken the photoionization-confinement argument.
  • The doublet ratio near unity could be used as an optical-depth diagnostic for Seyfert 2 narrow-line regions, complementing the standard broad-line-region ratio of about two.
Original abstract

We present far-ultraviolet spectra of the Seyfert2 galaxy Mrk533 obtained with FUSE. These spectra show narrow asymmetrical OVI 1032,1038 emission lines with stronger wings shortward of the peak wavelength, but the degree of asymmetry of these wings in velocity is much lower than that of the wings of the lines of lower ionization. In the combined OVI profile there are marginal indications of local absorptions in the outflow. The CIII 977 line is seen weakly with a similar profile, but with very low signal to noise. These FUV spectra are among the first for a Seyfert of type2, i.e., a purportedly obscured Seyfert. The HST STIS spectral image of Mrk533 allows delineation of the various components of the outflow, and we infer that the outflow is accelerated. We discuss the results in terms of nuclear geometry and kinematics.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 5,611 input tokens.

What the abstract itself states, as probabilities: claims first 0.30 · states limitation 0.81 · human participants 0.01 · controlled comparison 0.04 · randomized assignment 0.01 · states quantitative result 0.11 · compares with prior results 0.45 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

We present far-ultraviolet spectra of the Seyfert2 galaxy Mrk533 obtained with FUSE. These spectra show narrow asymmetrical OVI 1032,1038 emission lines with stronger wings shortward of the peak wavelength, but the degree of asymmetry of these wings in velocity is much lower than that of the wings of the lines of lower ionization. In the combined OVI profile there are marginal indications of local absorptions in the outflow. The CIII 977 line is seen weakly with a similar profile, but with very low signal to noise. These FUV spectra are among the first for a Seyfert of type2, i.e., a purportedly obscured Seyfert. The HST STIS spectral image of Mrk533 allows delineation of the various components of the outflow, and we infer that the outflow is accelerated. We discuss the results in terms of nuclear geometry and kinematics.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We present far-ultraviolet spectra of the Seyfert2 galaxy Mrk533 obtained with FUSE. contribution 0.75 0.96 0.02 asserted 0.99
s1 These spectra show narrow asymmetrical OVI 1032,1038 emission lines with stronger wings shortward of the peak wavelength, but the degree of asymmetry of these wings in velocity is much lower than that of the wings of the lines of lower ionization. result 1.00 0.94 0.14 asserted 1.00
s2 In the combined OVI profile there are marginal indications of local absorptions in the outflow. result 1.00 0.92 0.05 hedged possibility 0.99
s3 The CIII 977 line is seen weakly with a similar profile, but with very low signal to noise. result 0.97 0.93 0.02 asserted 1.00
s4 These FUV spectra are among the first for a Seyfert of type2, i.e., a purportedly obscured Seyfert. contribution 0.50 0.44 0.04 asserted 0.95
s5 The HST STIS spectral image of Mrk533 allows delineation of the various components of the outflow, and we infer that the outflow is accelerated. result 0.56 0.95 0.62 asserted 0.50
s6 We discuss the results in terms of nuclear geometry and kinematics. interpretation 0.93 0.74 0.05 unclear 0.76

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.91.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. — The O VI doublet region of the spectrum of Mrk 533. Data from the detectors LiF1A & LiF2B which give redundant coverage of this region, have been combined (lower panel). On top in this panel an example of a model absorption spectrum of Galactic H2 at zero redshift that corresponds to a H2 column density of 5× 1019cm−2 is illustrated (cf., 2.4), showing that several of the dips in the Mrk 533 spectra are contamination from absorption in our Galaxy. The positions of these troughs are indicated by horizontal lines above the upper H2 spectrum. The dashed lines marked on the O…
Figure 2. — The Mrk 533 spectra in the O VI region plotted in veloc
Figure 3. — The spectrum in the C IIIregion plotted in velocity space. The S/N is much lower in this region, but nevertheless the C III emission is detected. The model H2 absorption spectrum at zero redshift is plotted on top. A symmetrical (Gaussian) profile is plotted to guide the eye, but no attempt has been made to remove the effect of Galactic H2 absorption. A trough is seen (in both detectors, combined here) in a region that is clear of Galactic H2 absorption, which corresponds to a velocity of −200km s−1 , but is at best of marginal significance. from hot stars is negligible. This…
Figure 4. — The HST ST IS spectral image of Mrk 533 in the region of [O III]λ5007 line is plotted in velocity space. The vertical spatial axis is along the ST IS slit at a PA of 124◦ (along the radio axis). The zero position of this axis corresponds to the peak of the continuum in the off-line region. The zero position of the horizontal dispersion axis corresponds to the systemic velocity of 8659km s−1 (cf., Sec.4). 5.1. The Line-Ratio of the O VI Doublet The statistical weights of the upper levels of the O VI doublet transitions are two and four for the longward and shortward wavelength…
Figure 5. — The profiles of the [O III]λ5007 and Hβ lines from the HST ST IS data are plotted together with the O VI profile from F USE . In the top panel, the solid and dashed curves represent the profiles of the [O III]λ5007 and Hβ lines respectively, as extracted from a ST IS long￾slit aperture. In the middle panel, the solid curve represents the profile of the [O III]λ5007 line extracted from a ‘nuclear’ aperture (the 42nd pixel row in the ST IS data which is at the continuum position). The dashed curve represents the profile from the off-nuclear region, ∼ 0 ′′.15 NW from the ‘nucleus’…

Figures reproduced from arXiv:astro-ph/0603842 by the authors.

References

Discussion

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