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NASA NTRS2022

Polarization Constraints on the X-ray Corona in Seyfert Galaxies: MCG-05-23-16

We report on the first observation of a radio-quiet Active Galactic Nucleus (AGN) inpolarized X-rays: the Seyfert 1.9 galaxy MCG-05-23-16. This source was pointed at with theImaging X-ray Polarimetry Explorer(IXPE) starting on May 14, 2022 for a net observing timeof 486 ks, simultaneously with XMM-Newton(58 ks) andNuSTAR(83 ks). A polarizationdegreeΠsmaller than 4.7% (at the 99% confidence level) is derived in the 2–8 keV energyrange, where emission is dominated by the primary component ascribed to the hot corona.The broad-band spectrum, inferred from a simultaneous fit to theIXPE,NuSTAR, and XMM-Newtondata, is well reproduced by a power law with photon indexΓ=1.85±0.01and ahigh-energy cutoffEC=120±15keV. A comparison with Monte Carlo simulations showsthat a lamp-post and a conical geometry of the corona are consistent with the observed upperlimit, a slab geometry is allowed only if the inclination angle of the system is less than 50◦

A Marinucci↗
NASA NTRS2002

The X-ray Reflectors in the Nucleus of the Seyfert Galaxy NGC 1068

Based on observations of the Seyfert nucleus in NGC 1068 with ASCA, RXTE and BeppoSAX, we report the discovery of a flare (increase in flux by a factor of approximately 1.6) in the 6.7 keV Fe K line component between observations obtained four months apart, with no significant change in the other (6.21, 6.4, and 6.97 keV) Fe Kalpha line components. During this time, the continuum flux decreased by approximately 20%. The RXTE spectrum requires an Fe K absorption edge near 8.6 keV (Fe XXIII- XXV). The spectral data indicate that the 2-10 keV continuum emission is dominated (approximately 2/3 of the luminosity) by reflection from a previously unidentified region of warm, ionized gas located approximately or less than 0.2 pc from the AGN. The remaining approximately 1/3 of the observed X-ray emission is reflected from optically thick, neutral gas. The coronal gas in the inner Narrow-Line Region (NLR) and/or the cold gas at the inner surface of the obscuring 'torus' are possible cold reflectors. The inferred properties of the warm reflector are: size (diameter) approximately or less than 0.2 pc, gas density n approximately or greater than 10(exp 5.5)/cu cm, ionization parameter xi is approximately 10(exp 3.5) erg cm s(exp -1), and covering fraction 0.003 (L(sub 0)/ 10(exp 43.5) erg s(exp -1)(exp -1) less than (omega/4pi) less than 0.024 (L(sub 0)/ 10(exp 43.5) erg s(exp -1) (exp -1) where L(sub 0) is the intrinsic 2-10 keV X-ray luminosity of the AGN. We suggest that the warm reflector gas is the source of the (variable) 6.7 keV Fe line emission, and the 6.97 keV Fe line emission. The 6.7 keV line flare is assumed to be due to an increase in the emissivity of the warm reflector gas from a decrease (by 20-30%) in L(sub 0). The properties of the warm reflector are most consistent with an intrinsically X-ray weak AGN with L(sub 0) approximately equals 10(exp 43.0) erg s(exp -1). The optical and UV emission that scatters from the warm reflector into our line of sight is required to suffer strong extinction, which can be reconciled if the line-of-sight skims the outer surface of the torus. Thermal bremsstrahlung radio emission from the warm reflector may be detectable in VLBA radio maps of the NGC 1068 nucleus.

Colbert, Edward J. M.↗
NASA NTRS1992

Anisotropic ionizing radiation in Seyfert galaxies. I - The extended narrow-line region in Markarian 573

The morphology, kinematics, and ionization state of the nuclear extended narrow-line region (ENLR) of the Seyfert 2 galaxy Mrk 573 are studied using narrow-band images of a grid of long-slit spectra. The entire ENLR is mapped spectroscopically, and velocity structure is studied. The velocity field map shows a typical galactic rotation picture with some important deviations. A simple geometric model, in accordance with the 'unified schemes', is employed to study the effects of various parameters of the observed picture. The best match is achieved when a biconical radiation field illuminates the ISM of the host galaxy that takes part in a normal galaxy rotation but also has radial motions close to the nucleus. The emission-line images reveal an ENLR elongated along the radio axis in the northwest-southeast direction, but a map of the flux ratio forbidden O III 5007/(H-alpha + forbidden N II) shows a different structure, with the highest excitation peak offset by about 4 arcsec along the radio axis to the southeast.

Tsvetanov, Zlatan↗
DOE OSTI2021

A comparative study of the physical properties for a representative sample of Narrow and Broad-line Seyfert galaxies

ABSTRACT We present a comparative study of the physical properties of a homogeneous sample of 144 Narrow line Seyfert 1 (NLSy1) and 117 Broad-line Seyfert 1 (BLSy1) galaxies. These two samples are in a similar luminosity and redshift range and have optical spectra available in the 16th data release of Sloan Digital Sky Survey (SDSS-DR16) and X-ray spectra in either XMM-NEWTON or ROSAT. Direct correlation analysis and a principal component analysis (PCA) have been performed using ten observational and physical parameters obtained by fitting the optical spectra and the soft X-ray photon indices as another parameter. We confirm that the established correlations for the general quasar population hold for both types of galaxies in this sample despite significant differences in the physical properties. We characterize the sample also using the line shape parameters, namely the asymmetry and kurtosis indices. We find that the fraction of NLSy1 galaxies showing outflow signatures, characterized by blue asymmetries, is higher by a factor of about 3 compared to the corresponding fraction in BLSy1 galaxies. The presence of high iron content in the broad-line region of NLSy1 galaxies in conjunction with higher Eddington ratios can be the possible reason behind this phenomenon. We also explore the possibility of using asymmetry in the emission lines as a tracer of outflows in the inner regions of Active Galactic Nuclei. The PCA results point to the NLSy1 and BLSy1 galaxies occupying different parameter spaces, which challenges the notion that NLSy1 galaxies are a subclass of BLSy1 galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

The continuum of type 1 Seyfert galaxies. I - A single form modified by the effects of dust

Broad-band measurements from 1 to 20 microns of 26 emission-line active galactic nuclei (AGNs), mainly Seyfert 1 galaxies, have been made. These data have been combined with previous optical and infrared photometry and IRAS 12, 25, 60 and 100 micron fluxes, giving a total sample of 37 AGNs, all of which have hard X-ray measurements. The sample includes all the emission-line AGNs identified in the Piccinotti et al. (1982) survey. When corrected for stellar contributions in the near-infrared, the continuum energy distributions can be classified observationally into three types: (1) bare, minimally reddened AGNs; (2) reddened AGNs; and (3) AGNs for which the far-infrared emission is contaminated by the host galaxy. These classifications reflect a range of luminosities and different environments rather than intrinsic differences in the primary continuum of the AGNs. The data are consistent with a single underlying form of active galaxy continuum modified by the presence of dust and of the host galaxy.

Ward, Martin↗
NASA NTRS1987

Broad-band properties of the CfA Seyfert Galaxies. II - Infrared to millimeter properties

IR and mm observations of the 48 Seyfert 1 and 2 galaxies (SG1s and SG2s) of the CfA sample (Huchra and Berg, 1987) are reported. Data obtained (1) in the NIR using the 1.55-m reflector at Stewart Observatory and the 3-m IRTF during 1984-1986, (2) in the FIR with IRAS, and (3) at 1.3 mm using the 12-m NRAO telescope at KPNO in June 1984 are presented in extensive tables and graphs and characterized in detail. None of the objects was detected at 1.3 mm, and the IR spectra of the SG2s are found to be significantly steeper (indicating thermal emission) than those of SG1s and QSOs (nonthermal emission). Turnover in the IR emission below 100 microns (in half of the objects detected at three or more IRAS wavelengths) is shown to be consistent with an accretion disk in dust-free SG1s and with unusually warm (35-65 K) dust in SG2s. It is inferred that a 60-100-micron cool excess is masking turnover in the other SGs, so that a general association of SG nuclei with strong star formation can be confirmed.

Edelson, R. A.↗
NASA NTRS1992

Seyfert galaxy ultraviolet emission-line intensities and variability - A self-consistent photoionization analysis applied to broad-line-emitting gas in NGC 3783

Well-constrained photoionization models for the Seyfert I galaxy NGC 3783 are developed. Both cross-correlation analyses and line variability trends with varying ionizing radiation flux require a multicomponent picture. All the data for He II 1640 A, C IV 1549 A, and semiforbidden C III 1909 A can be reasonably well reproduced by two cloud components. One has a source-cloud distance of 24 lt-days, gas density around 3 x 10 exp 10/cu cm, ionization parameter range of 0.04-0.2, and cloud thickness such that about half of the carbon is doubly ionized and about half is triply ionized. The other component is located approximately 96 lt-days from the source, is shielded from the source by the inner cloud, has a density about 3 x 10 to the 9th/cu cm, and is characterized by an ionization parameter range of 0.001-0.03, The cloud thickness is such that about 45 percent carbon is doubly ionized and about 55 percent is singly ionized.

Koratkar, Anuradha P.↗
NASA NTRS1981

Rapid X-ray variability in the Seyfert galaxy NGC 6814

In contrast with the Tennant et al (1981) sample of over 30 active galactic nuclei, HEAO 1 A-2 high time resolution X-ray observations of the X-ray emitting Seyfert 1 galaxy NGC 6814 show strong X-ray variability on time scales of less than 3 hr. On a time scale of 90 min, the mean flux varied by a factor of about 2.5, and a characteristic time for variability of 100 + 60 or - 25 sec is obtained by autocorrelation analysis. There is no indication of spectral variability with an upper limit on a change in the power law spectral index of less than about 0.37, for a factor 2 change in intensity. The constraints of such rapid variability on a range of X-ray source mechanisms is discussed.

Tennant, A. F.↗
NASA NTRS1987

Broad, variable absorption lines in the Seyfert Galaxy NGC 3516 - Probing the structure of the emission-line regions

Nineteen short-wavelength IUE archive images were analyzed in order to probe the structure of the active nucleus in NGC 3516, an SB0 Seyfert I galaxy. The measurements of these features are presented, and the strength, variability, and morphology of the emission and absorption lines and their relation to the continuum are analyzed. It is shown that the absorption must arise within 10 pc of the nonthermal continuum source and that its variability must stem from changes in the velocity space coverage of clouds optically thin to the Lyman continuum. Two possible sites of absorption are discussed: dense clouds in the narrow-line region and optically thin clouds in the broad-line region. A theoretical model that explains the anticorrelation of C IV absorption with continuum flux is described.

Voit, G. Mark↗
DOE OSTI2024

A post-merger enhancement only in star-forming Type 2 Seyfert galaxies: the deep learning view

ABSTRACT Supermassive black holes require a reservoir of cold gas at the centre of their host galaxy in order to accrete and shine as active galactic nuclei (AGN). Major mergers have the ability to drive gas rapidly inwards, but observations trying to link mergers with AGN have found mixed results due to the difficulty of consistently identifying galaxy mergers in surveys. This study applies deep learning to this problem, using convolutional neural networks trained to identify simulated post-merger galaxies from survey-realistic imaging. This provides a fast and repeatable alternative to human visual inspection. Using this tool, we examine a sample of ∼8500 Seyfert 2 galaxies ($L[\mathrm{O\, {\small III}}] \sim 10^{38.5 - 42}$ erg s−1) at z < 0.3 in the Sloan Digital Sky Survey and find a merger fraction of $2.19_{-0.17}^{+0.21}$ per cent compared with inactive control galaxies, in which we find a merger fraction of $2.96_{-0.20}^{+0.26}$ per cent, indicating an overall lack of mergers among AGN hosts compared with controls. However, matching the controls to the AGN hosts in stellar mass and star formation rate reveals that AGN hosts in the star-forming blue cloud exhibit a ∼2 × merger enhancement over controls, while those in the quiescent red sequence have significantly lower relative merger fractions, leading to the observed overall deficit due to the differing M*–SFR distributions. We conclude that while mergers are not the dominant trigger of all low-luminosity, obscured AGN activity in the nearby Universe, they are more important to AGN fuelling in galaxies with higher cold gas mass fractions as traced through star formation.

Avirett-Mackenzie, M. S.↗
NASA NTRS2019

Spatially Resolved Outflows in a Seyfert Galaxy at z=2.39

We present the first spatially resolved analysis of rest-frame optical and UV (UltraViolet) imaging and spectroscopy for a lensed galaxy at z equals 2.39 hosting a Seyfert active galactic nucleus (AGN). Proximity to a natural guide star has enabled observations with high signal-to-noise ratio using Very Large Telescope SINFONI (Spectrograph for INtegral Field Observations in the Near Infrared) plus adaptive optics (AO) of rest-frame optical diagnostic emission lines, which exhibit an underlying broad component with full width at half maximum approximately 700 kilometers per second in both the Balmer and forbidden lines. Measured line ratios place the outflow robustly in the region of the ionization diagnostic diagrams associated with AGNs. This unique opportunity - combining gravitational lensing, AO guiding, redshift, and AGN activity - allows for a magnified view of two main tracers of the physical conditions and structure of the interstellar medium in a star-forming galaxy hosting a weak AGN at Cosmic Noon. By analyzing the spatial extent and morphology of the Lyman alpha spectral line and dust-corrected Hydrogen spectral line emission, disentangling the effects of star formation and AGN ionization on each tracer, and comparing the AGN-induced mass outflow rate to the host star formation rate, we find that the AGN does not significantly impact the star formation within its host galaxy.

Fischer, Travis C.↗
NASA NTRS1981

UGC 10683B - A possible X-ray emitting Seyfert galaxy

Optical spectra are presented for both members of the pair of interacting galaxies UGC 10683, lying close to the HEAO-A1 satellite's unidentified, high-altitude X-ray source 1H 1703-01. It is determined that one galaxy of the pair, UGC 10683B, is of Seyfert Type I, and it is suggested that it may be related to the X-ray source. Higher-resolution X-ray observations are deemed necessary to determine whether there is an identity between UGC 10683B and 1H 1703-01.

Wilson, A. S.↗
NASA NTRS1974

On the steady flow of gas from the nuclei of Seyfert galaxies

Heating of gas energy released during explosive events produces hot winds in Seyfert nuclei. Steady-state solutions indicate that supersonic velocities up to about 800 km per sec are obtainable. Lyman continuum radiation emitted by the wind ionizes and maintains temperature of cooler gas clouds seen in emission, and dominates energy losses during early stages of expansion. A study of stability of the thermal equilibrium state leads to a two-component model: a hot stable phase (the wind), in pressure equilibrium with a cooler stable phase (clouds). Extreme variations in cloud electron densities are a consequence of the steep decrease with radius of external pressure. Cloud dynamics are related to the radius of formation and internal parameters. Permitted lines of H are emitted by high-density clouds formed at the base of the wind, while forbidden lines arise in radially moving clouds, produced throughout the wind.

Wolfe, A. M.↗
NASA NTRS1988

Molecular tori in Seyfert galaxies - Feeding the monster and hiding it

The principal properties of the tori of gas which surround Seyfert nuclei are discussed. The internal state of the clouds and their size distribution function are examined, and it is shown that the Jeans mass scale results in clouds which are individually sufficiently opaque to block out the nucleus, and that the balance of processes which controls their size distribution function also forces the covering factor to be of the order of or greater than unity. Where the gravitational potential is dominated by stars, cloud-cloud collisions keep the molecular clouds close to the equatorial plane. Stirring by stellar processes is never strong enough to compete with collisional losses. The position of the inner edge of the torus is determined by a balance between the inward flow of clouds and the rate at which the nuclear continuum can evaporate them.

Krolik, Julian H.↗
NASA NTRS1983

Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies

Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The averager spectral index alpha is 0.66 + or - .36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N(H) 10 to the 22nd power/sq cm; the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0175-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium.

Petre, R.↗
NASA NTRS1984

Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies

Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The average spectral index alpha is 0.66 + or -0.36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N sub H greater than 10 to the 22nd power/sq cm); the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0.75-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s) or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium. Previously announced in STAR as N84-14082

Petre, R.↗
DOE OSTI2022

Chemical abundances in Seyfert galaxies – Ⅸ. Helium abundance estimates

For the first time, the helium abundance relative to hydrogen (He/H), which relied on direct measurements of the electron temperature, has been derived in the narrow line regions (NLRs) from a local sample of Seyfert 2 nuclei. In view of this, optical emission line intensities [3000 < λ(Å) < 7000] of 65 local Seyfert 2 nuclei (z < 0.2), taken from Sloan Digital Sky Survey Data Release 15 and additional compilation from the literature, were considered. Here we used photoionization model grid to derive an Ionization Correction Factor (ICF) for the neutral helium. The application of this ICF indicates that the NLRs of Seyfert 2 present a neutral helium fraction of ~50 percent in relation to the total helium abundance. We find that Seyfert 2 nuclei present helium abundance ranging from 0.60 to 2.50 times the solar value, while ~85 percent of the sample present oversolar abundance values. The derived (He/H)–(O/H) abundance relation from the Seyfert 2 is stepper than that of star-forming regions (SFs) and this difference could be due to excess of helium injected into the interstellar medium by the winds of Wolf–Rayet stars. From a regression to zero metallicity, by using Seyfert 2 estimates combined with SFs estimates, we obtained a primordial helium mass fraction Y p = 0.2441 ± 0.0037, a value in good agreement with the one inferred from the temperature fluctuations of the cosmic microwave background by the Planck Collaboration, i.e. $Y_{p}^{Planck}$ =0.2471 ± 0.0003.

79 ASTRONOMY AND ASTROPHYSICS↗