Galaxy IC 4329A Research Articles

The X-ray polarization of the Seyfert 1 galaxy IC 4329A

ABSTRACT We present an X-ray spectro-polarimetric analysis of the bright Seyfert galaxy IC 4329A. The Imaging X-ray Polarimetry Explorer (IXPE) observed the source for ∼500 ks, supported by XMM–Newton (∼60 ks) and NuSTAR (∼80 ks) exposures. We detect polarization in the 2–8 keV band with 2.97σ confidence. We report a polarization degree of 3.3 ± 1.1 per cent and a polarization angle of 78° ± 10° (errors are 1σ confidence). The X-ray polarization is consistent with being aligned with the radio jet, albeit partially due to large uncertainties on the radio position angle. We jointly fit the spectra from the three observatories to constrain the presence of a relativistic reflection component. From this, we obtain constraints on the inclination angle to the inner disc (<39° at 99 per cent confidence) and the disc inner radius (<11 gravitational radii at 99 per cent confidence), although we note that modelling systematics in practice add to the quoted statistical error. Our spectropolarimetric modelling indicates that the 2–8 keV polarization is consistent with being dominated by emission directly observed from the X-ray corona, but the polarization of the reflection component is completely unconstrained. Our constraints on viewer inclination and polarization degree tentatively favour more asymmetric, possibly out-flowing, coronal geometries that produce more highly polarized emission, but the coronal geometry is unconstrained at the 3σ level.

AstroSat/UVIT observations of IC 4329A: constraining the accretion disc inner radius

ABSTRACT We present a study of far- and near ultraviolet (UV) emission from the accretion disc in a powerful Seyfert 1 galaxy IC 4329A using observations performed with the Ultraviolet Imaging Telescope (UVIT) onboard AstroSat. These data provide the highest spatial resolution and deepest images of IC 4329A in the far- and near UV bands acquired to date. The excellent spatial resolution of the UVIT data has allowed us to accurately separate the extended emission from the host galaxy and the AGN emission in the far- and near UV bands. We derive the intrinsic AGN flux after correcting for the Galactic and internal reddening, as well as for the contribution of emission lines from the broad and narrow-line regions. The intrinsic UV continuum emission shows a marked deficit compared to that expected from the ‘standard’ models of the accretion disc around an estimated black hole mass of $1-2\times 10^8\, {\rm M}_{\odot }$ when the disc extends to the innermost stable circular orbit. We find that the intrinsic UV continuum is fully consistent with the standard disc models, but only if the disc emits from distances larger than ∼80–150 gravitational radii.

The new primary X-ray component confirmed in the Seyfert I galaxy IC 4329A

Abstract The bright and highly variable Seyfert I active galactic nucleus IC 4329A was observed with Suzaku five times in 2007 August, with intervals of ∼5 days and a net exposure of 24–31 ks each. Another longer observation was carried out in 2012 August with a net exposure of 118 ks. In the six observations, a source was detected in 2–45 keV with an average 2–10 keV fluxes of (0.67–1.2) × 10−10 erg cm−2 s−1. Its intensity changed by a factor of 2 among the five observations in 2007, and 1.5 within the 2012 observation. A difference of spectrum among these observations revealed that the variability of IC 4329A was carried mainly by a power-law component with a photon index Γ ∼ 2.0. However, in addition to this primary component and its associated reflection, the broad-band Suzaku data required another, harder, and less-variable component with Γ ∼ 1.4. The presence of this new continuum was also confirmed by analyzing the same six data sets through the spectral decomposition technique developed by Noda et al. (2013a, ApJ, 771, 100). This Γ ∼ 1.4 continuum is considered to be a new primary component that has not been recognized in the spectra of IC 4329A so far, although it was recently identified in those of several other Seyfert I galaxies (Noda et al. 2013a, ApJ, 771, 100; Noda et al. 2014, ApJ, 794, 2).

Relativistic iron Kα line detection in the Suzaku spectra of IC 4329A

Abstract We present an analysis of five Suzaku observations of the bright Seyfert1 galaxy IC 4329A. The broad energy band and high signal-to-noise ratio of the data give new constraints on the iron Kα line profile and its relationship with the Compton hump at higher energies. The Fe K bandpass is dominated by a narrow core (EW = 57$_{-3}^{+3}$ eV) at 6.4 keV consistent with neutral material. Using a physically motivated model, our analysis also reveals the presence of a broad iron Kα line (EW = 124$_{-11}^{+11}$ eV), most likely produced in the inner part of the accretion disc and blurred by general relativistic effects. This component is not immediately evident from the individual spectra, but is clearly present in the stacked residuals of all five observations, and has high statistical significance. This highlights the difficulty in identifying broad iron lines in active galactic nuclei, even in data with very high signal-to-noise ratio, as they are difficult to disentangle from the continuum. The data are consistent with the narrow and broad iron line components tracking the Compton Hump, but do not provide clear evidence that this is the case. An additional narrow Fe xxvi emission line at 6.94 keV is also seen, suggesting the presence of ionized material relatively distant from the central region. There is also a hint of variability, so the precise origin of this line remains unclear.

THE BROAD-BAND X-RAY SPECTRUM OF IC 4329A FROM A JOINTNuSTAR/SUZAKUOBSERVATION

We have obtained a deep, simultaneous observation of the bright, nearby Seyfert galaxy IC 4329A with Suzaku and NuSTAR. Through a detailed spectral analysis, we are able to robustly separate the continuum, absorption and distant reflection components in the spectrum. The absorbing column is found to be modest at $N_H = 6 \times 10^{21}$ cm$^2$, and does not introduce any significant curvature in the Fe K band. We are able to place a strong constraint on the presence of a broadened Fe K{\alpha} line: $E = 6.46^{+0.08}_{-0.07}$ keV rest frame with ${\sigma} = 0.33^{+0.08}_{-0.07}$ keV and $EW = 34^{+8}_{-7}$ eV, though we are not able to constrain any of the parameters of a relativistic reflection model. These results highlight the range in broad Fe K{\alpha} line strengths observed in nearby, bright AGN (roughly an order of magnitude), and imply a corresponding range in the physical properties of the inner accretion disk in these sources. We have also updated our previously reported measurement of the high-energy cutoff of the hard X-ray emission using both observatories rather than just NuSTAR alone: $E_{cut} = 186 \pm 14$ keV. This high-energy cutoff acts as a proxy for the temperature of the coronal electron plasma, enabling us to further separate this parameter from the optical depth of the plasma and to update our results for these parameters as well. We derive $kT = 50^{+6}_{-3}$ keV with ${\tau} = 2.34^{+0.16}_{-0.11}$ using a spherical geometry, $kT = 61 \pm 1$ keV with ${\tau} = 0.68 \pm 0.02$ for a slab geometry, with both having an equivalent goodness-of-fit.

MEASURING THE CORONAL PROPERTIES OF IC 4329A WITHNuSTAR

We present an analysis of a ~160 ks NuSTAR observation of the nearby bright Seyfert galaxy IC4329A. The high-quality broadband spectrum enables us to separate the effects of distant reflection from the direct coronal continuum, and to therefore accurately measure the high-energy cutoff to be $E_{cut}=178^{+74}_{-40}$ keV. The coronal emission arises from accretion disk photons Compton up-scattered by a thermal plasma, with the spectral index and cutoff being due to a combination of the finite plasma temperature and optical depth. Applying standard Comptonization models, we measure both physical properties independently using the best signal-to-noise obtained to date in an AGN over the 3-79 keV band. We derive $kT_e=37^{+7}_{-6}$ keV with $\tau=1.25^{+0.20}_{-0.10}$ assuming a slab geometry for the plasma, and $kT_e=33^{+6}_{-6}$ keV with $\tau=3.41^{+0.58}_{-0.38}$ for a spherical geometry, with both having an equivalent goodness-of-fit.

Fe K Emission and Absorption in theXMM‐EPIC Spectrum of the Seyfert Galaxy IC 4329a

We present a re-analysis of the XMM-Newton long-look of the X-ray bright Seyfert galaxy IC 4329a. The Fe K bandpass is dominated by two peaks, consistent with emission from neutral or near-neutral Fe Ka and KP. A relativistic diskline model whereby both peaks are the result of one doubly-peaked diskline profile is found to be a poor description of the data. Models using two relativistic disklines are found to describe the emission profile well. A low-inclination, moderately-relativistic dual-diskline model is possible if the contribution from narrow components, due to distant material, is small or absent. A high-inclination, moderately relativistic profile for each peak is possible if there are roughly equal contributions from both the broad and narrow components. Upper limits on Fe XXV and Fe XXVI emission and absorption at the systemic velocity of IC 4329a are obtained. We also present the results of RXTE monitoring of this source obtained so far; the combined XMM-Newton and RXTE data sets allow us to explore the time-resolved spectral behavior of this source on time scales ranging from hours to 2 years. We find no strong evidence for variability of the Fe Ka emission line on any time scale probed, likely due to the minimal level of continuum variability. We detect a narrow absorption line, at a energy of 7.68 keV in the rest frame of the source; its significance has been confirmed using Monte Carlo simulations. This feature is most likely due to absorption from Fe XXVI blueshifted to approximately 0.1c relative to the systemic velocity, making IC 4329a the lowest-redshift AGN known with a high-velocity, highly-ionized outflow component. As is often the case with similar outflows seen in high-luminosity quasars, the estimated mass outflow rate is larger than the inflow accretion rate, signaling that the outflow represents a substantial portion of the total energy budget of the AGN. The outflow could arise from a radiatively-driven disk wind, or it may be in the form of a discrete, transient blob of ejected material.

XMM-Newton observations of the heavily absorbed Seyfert 1 galaxy IC 4329A

We detect seven distinct absorbing systems in the high-resolution X-ray spectrum of the Seyfert 1 galaxy IC 4329A, taken with XMM-Newton. Firstly we detect absorption due to cold gas in our own Galaxy and warm gas in the Galactic halo or the Local Group. This local warm gas is only detected through O VII absorption, from which we deduce a temperature between 0.03 and 0.2 keV. In IC 4329A we detect absorption from the host galaxy as well as from a warm absorber, close to the nucleus, which has 4 components. The absorption from the host galaxy is well modeled by neutral material. The warm absorber detected in IC 4329A is photoionized and has an ionization range between log $\xi$ = -1.37 and log $\xi$ = 2.7. A broad excess is measured at the O VIII Ly$\alpha$ and N VII Ly$\alpha$ emission lines, which can be modeled by either disklines or multiple Gaussians. From the lightcurve we find that the source changed luminosity by about 20 % over the 140 ks observation, while the spectral shape, i.e. the softness ratio did not vary. In the EPIC spectra a narrow Fe K$\alpha$ and Fe XXVI Ly$\alpha$ emission line are detected. The narrowness of the Fe K$\alpha$ line and the fact that there is no evidence for flux variability between different observations leads us to conclude that the Fe K$\alpha$ line is formed at a large distance from the central black hole.

High‐Resolution X‐Ray Spectroscopy of the Fe K Complex in IC 4329A

We report the detection of complex Fe K line emission from a Chandra High Energy Transmission Grating Spectrometer (HETGS) observation of the Seyfert 1 galaxy IC 4329A. The line emission is double-peaked, one peak centered at ~6.3 keV and the other at ~6.9 keV in the source rest frame. When modeled by Gaussians, the lower energy peak is resolved by the high-energy grating at greater than 99% confidence, while the higher energy peak is resolved at only less than 90% confidence. The best-fitting widths are ~21,000 and ~4000 km s-1 FWHM for the ~6.3 and ~6.9 keV peaks, respectively. If the peaks correspond to two distinct emission lines, then the peak energies are redshifted with respect to the expected line energies of Fe I Kα and Fe XXVI Lyα by at least 650 and 950 km s-1, respectively. Alternatively, the Fe K line profile may be due to a single line from a relativistic accretion disk. In that case, the inclination angle of the disk is required to be 24 degrees, the outer radius is constrained to several tens of gravitational radii, and the radial line emissivity is flatter than r-0.7. Another possibility is that both peaks are due to distinct lines but that each one is relativistically broadened by a disk. In that case, the lower energy peak could correspond to emission from Fe in a low ionization state and the high-energy peak to Fe XXVI Lyα emission. Then the inclination angle is even less, restricted to a few degrees. However, the radial emissivity law is allowed to be steeper (~r-2.5), and the outer radius does not have to be fine-tuned. Yet another scenario is that the lower energy peak originates in a disk but the higher energy peak originates in more distant matter. The disk inclination angle is then intermediate between the last two cases, but the emissivity is again required to be flat. We cannot rule out Fe XXV He-like absorption modifying the observed line profile. However, the data and the inferred emission-line parameters are insensitive to the presence of a Compton reflection continuum. Including Compton reflection does, however, allow a steeper radial emissivity law for the relativistic line. Future missions, such as Astro-E2, will be able to break a lot of the degeneracy in the physically distinct models that can all account for the Chandra data. Since IC 4329A is one of the brightest Seyfert 1 galaxies, it should be a good astrophysical laboratory for studying the ionization structure of accretion disks around supermassive black holes.

The Relativistic Iron Line Profile in the Seyfert 1 Galaxy IC 4329A

We present simultaneous ASCA and RXTE data on the bright Seyfert 1 galaxy IC4329a. The iron line is significantly broadened, but not to the extent expected from an accretion disk which extends down to the last stable orbit around a black hole. We marginally detect a narrow line component, presumably from the molecular torus, but even including this gives a line profile from the accretion disk which is significantly narrower that that seen in MCG-6-30-15, and is much more like that seen from the low/hard state galactic black hole candidates. This is consistent with the inner disk being truncated before the last stable orbit, forming a hot flow at small radii as in the ADAF models. However, we cannot rule out the presence of an inner disk which does not contribute to the reflected spectrum, either because of extreme ionisation suppressing the characteristic atomic features of the reflected spectrum or because the X-ray source is intrinsically anisotropic, so it does not illuminate the inner disk. The source was monitored by RXTE every 2 days for 2 months, and these snapshot spectra show that there is intrinsic spectral variability. The data are good enough to disentangle the power law from the reflected continuum and we see that the power law softens as the source brightens. The lack of a corresponding increase in the observed reflected spectrum implies that either the changes in disk inner radial extent/ionisation structure are small, or that the variability is actually driven by changes in the seed photons which are decoupled from the hard X-ray mechanism.

Warm Absorber, Reflection, and Fe K Line in the X-Ray Spectrum of IC 4329A

Results from the X-ray spectral analysis of the ASCA PV phase observation of the Seyfert 1 galaxy IC 4329A are presented. We find that the 0.4 - 10 keV spectrum of IC 4329A is best described by the sum of a steep ($\Gamma \sim 1.98$) power-law spectrum passing through a warm absorber plus a strong reflection component and associated Fe K line, confirming recent results (Madejski et al. 1995, Mushotsky et al. 1995). Further cold absorption in excess of the Galactic value and covering the entire source is also required by the data, consistent with the edge-on galactic disk and previous X-ray measurements. The effect of the warm absorber at soft X-ray energies is best parameterized by two absorption edges, one consistent with OVI, OVII or NVII, the other consistent with OVIII. A description of the soft excess in terms of blackbody emission, as observed in some other Seyfert 1 galaxies, is ruled out by the data. A large amount of reflection is detected in both the GIS and SIS detectors, at similar intensities. We find a strong correlation between the amount of reflection and the photon index, but argue that the best solution with the present data is that given by the best statistical fit. The model dependence of the Fe K line parameters is also discussed. Our best fit gives a slightly broad ($\sigma \simeq 0.11 \pm 0.08$ keV) and redshifted (E $\simeq 6.20 \pm 0.07$ keV) Fe K line, with equivalent width $\simeq$ 89 $\pm$ 33 eV. The presence of a weak Fe K line with a strong reflection can be reconciled if one assumes iron underabundances or ionized reflection. We also have modeled the line with a theoretical line profile produced by an accretion disk. This yields results in better agreement with the constraints obtained from the reflection component.

Joint ROSAT-Compton GRO observations of the X-ray bright Seyfert galaxy IC 4329A

view Abstract Citations (79) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Joint ROSAT--Compton GRO Observations of the X-Ray--bright Seyfert Galaxy IC 4329A Madejski, G. M. ; Zdziarski, A. A. ; Turner, T. J. ; Done, C. ; Mushotzky, R. F. ; Hartman, R. C. ; Gehrels, N. ; Connors, A. ; Fabian, A. C. ; Nandra, K. ; Celotti, A. ; Rees, M. J. ; Johnson, W. N. ; Grove, J. E. ; Starr, C. H. Abstract We report a simultaneous ROSAT and GRO observation of the X-ray-bright Seyfert galaxy IC 4329A. For the GRO OSSE detector, we also present the sum of the data for this and earlier observations. The overall spectrum is very well described as a power law with an energy spectral index of ~1 absorbed at low energies plus a strong Compton reflection component, typical for Seyfert 1 galaxies. The low energy absorption can be well described by a sum of a neutral column density of ~3 x 10^21^ cm^-2^, most of which is associated with the edge-on galactic disk of IC 4329A, plus an edgelike feature at ~700 eV; this feature implies either complex absorption (due to additional ionized material, or due to partial covering), or a soft excess. The data only weakly constrain the presence of a high-energy cutoff in the underlying power law; they are compatible with an exponential cutoff at any energy E_c_ ~> 100 keV. The relative steepness of the OSSE data, with the powerlaw energy index of 1.6 +/- 0.2, can be accounted for entirely by the contribution of the high-energy tail of the reflection component when E_c_ approaches {infinity}. (We find that the definite cutoff at an energy E_c_ ~ 130 keV suggested in the recently published analysis of the OSSE data for this object is due to a data reduction error.) Including nonsimultaneous Ginga observations with 2 keV fluxes matching well that of ROSAT gives us likely broadband X-ray/γ-ray spectra of the object from ~0.1 keV up to several hundred keV. Joint spectral analysis of the data sets from the three instruments gives results similar to those from ROSAT/OSSE only, except that the cutoff energy is now constrained to be at 250 keV <~ E_c_ <~ 1700 keV. The constraint on E_c_ markedly distinguishes this object from NGC 4151, where E_c_ was lower, ~50 keV; this has implications for emission models for AGNs as well as for their contribution to the X-ray background. We also report the ROSAT spectrum of the companion object to the Seyfert galaxy, the elliptical galaxy IC 4329 located ~3' away. Its spectrum is well described by an optically thin thermal plasma wi4th kT = 0.9 keV, with a 0.1-2 keV flux of 8 x 10^-13^ ergs cm^-2^ s^-1`^, corresponding to a luminosity of ~8 x 10^41^ ergs s^-1^. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175111 Bibcode: 1995ApJ...438..672M Keywords: Brightness; Elliptical Galaxies; Seyfert Galaxies; Stellar Spectra; X Rays; Gamma Ray Observatory; Gamma Rays; Ginga Satellite; Rosat Mission; Spectrum Analysis; Astrophysics; GAMMA RAYS: OBSERVATIONS; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4329A; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4329; GALAXIES: SEYFERT; X-RAYS: GALAXIES full text sources ADS | data products SIMBAD (4) NED (3) HEASARC (1)

OSSE Observations of the Bright Seyfert 1 Galaxy IC 4329A: Erratum

view Abstract Citations References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OSSE Observations of the Bright Seyfert 1 Galaxy IC 4329A: Erratum Fabian, A. C. ; Nandra, K. ; Celotti, A. ; Rees, M. J. ; Grove, J. E. ; Johnson, W. N. Abstract In the Letter "OSSE Observations of the Bright Seyfert 1 Galaxy IC 4329A" by A. C. Fabian, K. Nandra, A. Celotti, M. J. Rees, J. E. Grove, and W. N. Johnson (ApJ, 416, L57 [1993]), there was a normalization error of a factor of 4 in the OSSE detector response matrix used. Therefore, the OSSE spectrum shown in Figure 4 should be increased by this factor relative to the Ginga data. This weakens the evidence for a spectral break, which must now have an e-folding energy greater than 350 keV. A paper discussing the reanalysis of the data, and the theoretical implications, is in preparation. Publication: The Astrophysical Journal Pub Date: February 1994 DOI: 10.1086/187196 Bibcode: 1994ApJ...421L..95F Keywords: ERRATA; ADDENDA full text sources ADS | data products NED (1) Related Materials (1) Original Paper: 1993ApJ...416L..57F

OSSE Observations of the Bright Seyfert 1 Galaxy IC 4329A

view Abstract Citations (12) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OSSE Observations of the Bright Seyfert 1 Galaxy IC 4329A Fabian, A. C. ; Nandra, K. ; Celotti, A. ; Rees, M. J. ; Grove, J. E. ; Johnson, W. N. Abstract We present the first hard X-ray/soft γ-ray observations from the Oriented Scintillation Spectrometer Experiment (OSSE) of a bright Seyfert 1 galaxy, IC 4329A. Significant variability was seen over the 3 week observing period. The 50-200 keV spectrum is steep and can be characterized by a power-law spectrum of photon index 2.84 +/- 0.36, at 90% confidence. This is significantly steeper than the X-ray spectrum found from Ginga data of the source. Joint fits of the Ginga and OSSE data are well modeled by a thermal model represented by an exponential spectral break with an e-folding energy at about 130 keV. Good fits are also obtained if a reflection component is included. We constrain possible nonthermal continuum models involving photon-photon pair production. There is a similarity between the X-ray/γ-ray spectra of IC 4329A and Cygnus X-1. Publication: The Astrophysical Journal Pub Date: October 1993 DOI: 10.1086/187070 Bibcode: 1993ApJ...416L..57F Keywords: GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4329A; GALAXIES: SEYFERT; GAMMA RAYS: OBSERVATIONS; GAMMA RAYS: THEORY full text sources ADS | data products SIMBAD (4) NED (1) HEASARC (1) Related Materials (1) Erratum: 1994ApJ...421L..95F

X-ray observations of the bright Seyfert galaxy IC 4329A

We have performed a detailed analysis of the broad-band (0.1-25 keV) EXOSAT observations of the high-luminosity, nearby Seyfert type I galaxy IC 4329A. The observations were carried out on two occasions, 1984 July and 1985 July. The X-ray luminosity decreased by ~35% over one year. A significant short-term variability where the intensity decreased by ~12% on a time scale of ~2 x 10^4^ s was detected in the 1985 data. The observed X-ray spectra are all well fitted by simple power-law models with nearly 10 times larger absorption than the Galactic value, indicating significant absorbing matter local to the source, consistent with the reddening observed in the optical spectrum. We do not find any evidence for low-energy excess in the spectra. The photon index {GAMMA} is measured to be 1.85+/- 0.06 (90% confidence) in 1984 and 1.7^+0.06^_- 0.05_(90% confidence) in 1985. We find a Fe line emission at 6.4 keV with an equivalent width of 169^+124^_-113_ eV in the 1984 data when the source was bright. The results are used to constrain the mass of the putative supermassive black hole in the nucleus of IC 4329A. The implications of the results on the matter surrounding the active galactic nucleus in IC 4329A are discussed.

IC 4329A - The nearest quasar

A spectrophotometric study of the Seyfert galaxy IC 4329A has been made with the Anglo-Australian Telescope. Fe II emission is found in the spectrum as well as forbidden lines with ionizations ranging up to (Fe X) lambda6374. The Balmer lines are double peaked, the secondary (more highly redshifted) component having a flatter Balmer decrement than the main one. The equivalent widths of most lines seem to be variable, with changes in the continuum level being the most plausible explanation.That the nucleus of IC 4329A is heavily reddened is indicated by the facts that (i) a prominent dust lane is seen to bisect the nucleus, (ii) the Balmer decrement (H..cap alpha../H..beta..approx. =12) is steeper than found in any other Seyfert galaxy, (iii) the observed nuclear optical continuum is very steep (F/sub ..nu../proportional..nu../sup -4.4/), and (iv) prominent Na I D-line absorption is seen at the redshift of IC 4329A. The values of A/sub upsilon/ derived from (ii), (iii), and (iv) above are 4.8, 2.5, and >1.6 mags, respectively. If Aupsilon lies in the range 2.5--4.8 mag, as seems most likely, the absolute nuclear magnitude M/sub upsilon/ lies in the range -23.0 to -25.3, values typical of quasars. The observations of the Namore » I D lines have also been used to deduce that the velocity dispersion of the absorbing sodium atoms lies in the range 8.4--13.5 km s/sup -1/ with 90% confidence. This small dispersion suggests that noncircular motions in the disk of IC 4329A are small and that the velocity dispersion of its interstellar medium is quite comparable to that in our Galaxy, contrary to theoretical speculations that the interstellar medium in Seyferts might be seriously disrupted.« less