A Search for “Dwarf” Seyfert Nuclei. VI. Properties of Emission‐Line Nuclei in Nearby Galaxies

The results of the emission-line and radio imaging survey of radio galaxies presented in Baum et al. (1988) and Baum and Heckman (1989) are used here to look for statistical evidence of energetic and spatial relationships between the extended emission-line gas and the radio source in powerful radio galaxies. It is found that radio luminosity correlates with the optical narrow emission-line luminosity over roughly four orders of magnitude in line luminosity and five in radio luminosity. The total emission-line luminosity of the powerful radio galaxies in the sample is roughly half of the luminosity of the associated radio source. There is a better correlation between the radio and narrow-line luminosity than between the radio and the total emission-line luminosities in radio galaxies. Statistical evidence is found for a spatial relationship between the very extended emission-line gas and the radio source. 88 references.

We analyse the integral field spectroscopy data for the ≈10 000 galaxies in final data release of the MaNGA survey. We identify 188 galaxies for which the emission lines cannot be described by single Gaussian components. These galaxies can be classified into (1) 38 galaxies with broad $\rm H\alpha$ and [O iii] $\rm \lambda$5007 lines, (2) 101 galaxies with broad $\rm H\alpha$ lines but no broad [O iii] $\rm \lambda$5007 lines, and (3) 49 galaxies with double-peaked narrow emission lines. Most of the broad-line galaxies are classified as active galactic nuclei (AGNs) from their line ratios. The catalogue helps us further understand the AGN-galaxy coevolution through the stellar population of broad-line region host galaxies and the relation between broad lines’ properties and the host galaxies’ dynamical properties. The stellar population properties (including mass, age, and metallicity) of broad-line host galaxies suggest there is no significant difference between narrow-line Seyfert-2 galaxies and Type-1 AGNs with broad $\rm H\alpha$ lines. We use the broad-$\rm H\alpha$ line width and luminosity to estimate masses of black hole in these galaxies, and test the MBH–σe relation in Type-1 AGN host galaxies. Furthermore, we find three dual AGN candidates supported by radio images from the VLA FIRST survey. This sample may be useful for further studies on AGN activities and feedback processes.

We use the sample of emission-line nuclei derived from a recently completed optical spectroscopic survey of nearby galaxies to quantify the incidence of local (z ≈ 0) nuclear activity. Particular attention is paid to obtaining accurate measurements of the emission lines and reliable spectral classifications. The resulting database contains the largest collection of star-forming nuclei and active galactic nuclei (AGNs) currently known for nearby galaxies. It consists of 420 emission-line nuclei detected from a nearly complete, magnitude-limited sample of 486 galaxies with BT ≤ 12.5 mag and declination greater than 0°; the equivalent width detection limit of the brightest emission line, usually Hα, is ~0.25 A. As is consistent with previous studies, we find detectable amounts of ionized gas in the central few hundred parsecs of most galaxies (86%); emission lines are present in essentially every spiral galaxy and in a large fraction of ellipticals and lenticulars. Based on their narrow-line spectra, half of the objects can be classified as H II or star-forming nuclei and the other half as some form of AGN, of which we distinguish three classes: Seyfert nuclei, low-ionization nuclear emission-line regions (LINERs), and transition objects that we assume to be composite LINER/H II-nucleus systems. The population of AGNs is consequently very large; approximately 43% of the galaxies in our survey can be regarded as active, although, for a number of reasons, this fraction is still rather uncertain. Most of the objects have much lower luminosities than commonly studied AGNs; the median luminosity of the narrow Hα line, after correcting for extinction, is only 2 × 1039 ergs s-1. Our sample therefore occupies the extreme faint end of the AGN luminosity function. We detect signatures of a broad-line region, as revealed by visible broad Hα emission, in ~20% of the AGN sample. Seyfert nuclei, both type 1 and type 2, reside in ~10% of all galaxies. LINERs make up the bulk (1/2-3/4) of the AGN population and a significant fraction (1/5-1/3) of all galaxies. A nonnegligible subset of LINERs emit broad Hα emission, furnishing direct evidence that a least some LINERs are indeed physically related to the AGN phenomenon. The dominant ionization mechanism of the nuclear emission depends strongly on the morphological type and luminosity of the host galaxy. AGNs are found predominantly in luminous, early-type (E-Sbc) galaxies, while H II nuclei prefer less luminous, late-type (Sbc and later) systems. The various AGN subclasses have broadly similar host galaxies.

Theoretically, bound binaries of massive black holes are expected as the natural outcome of mergers of massive galaxies. From the observational side, however, massive black hole binaries remain elusive. Velocity shifts between narrow and broad emission lines in quasar spectra are considered a promising observational tool to search for spatially unresolved, dynamically bound binaries. In this series of papers we investigate the nature of such candidates through analyses of their spectra, images and multi-wavelength spectral energy distributions. Here we investigate the properties of the optical spectra, including the evolution of the broad line profiles, of all the sources identified in our previous study. We find a diverse phenomenology of broad and narrow line luminosities, widths, shapes, ionization conditions and time variability, which we can broadly ascribe to 4 classes based on the shape of the broad line profiles: 1) Objects with bell-shaped broad lines with big velocity shifts (>1000 km/s) compared to their narrow lines show a variety of broad line widths and luminosities, modest flux variations over a few years, and no significant change in the broad line peak wavelength. 2) Objects with double-peaked broad emission lines tend to show very luminous and broadened lines, and little time variability. 3) Objects with asymmetric broad emission lines show a broad range of broad line luminosities and significant variability of the line profiles. 4) The remaining sources tend to show moderate to low broad line luminosities, and can be ascribed to diverse phenomena. We discuss the implications of our findings in the context of massive black hole binary searches.

NMA survey of CO and HCN emission from nearby active galaxies

We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from the Palomar optical spectroscopic survey of nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers a wide range of nuclear powers, from L2 10keV # 10 43 erg/s down to very low luminosities (L2 10keV # 10 38 erg/s). Best available data from Chandra, XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks to the good spatial resolution available from these observations and a proper modeling of the various spectral components, it has been possible to obtain accurate nuclear X-ray luminosities not contaminated by o! -nuclear sources and/or di! use emission. X-ray luminosities have then been corrected taking into account the likely candidate Compton thick sources, which are a high fraction (>30%) among type 2 Seyferts in our sample. The main result of this study is that we confirm strong linear correlations between 2-10 keV, (OIII)! 5007, H luminosities which show the same slope as quasars and luminous Seyfert galaxies, independent of the level of nuclear activity displayed. Moreover, despite the wide range of Eddington ratios (L/LEdd) tested here (six orders of magnitude, from 0.1 down to # 10 7 ), no correlation is found between the X-ray or optical emission line luminosities and the black hole mass. Our results suggest that Seyfert nuclei in our sample are consistent with being a scaled-down version of more luminous AGN.

Using all available major samples of Seyfert galaxies and their corresponding closely matched control samples of nonactive galaxies, we find that the bar ellipticities (or axial ratios) in Seyfert galaxies are systematically different from those in nonactive galaxies. Overall, there is a deficiency of bars with large ellipticities (i.e., "thin" or "strong" bars) in Seyfert galaxies compared to nonactive galaxies. Accompanied with a large dispersion due to small number statistics, this effect is strictly speaking at the 2 sigma level. To obtain this result, the active galaxy samples of near-infrared surface photometry were matched to those of normal galaxies in type, host galaxy ellipticity, absolute magnitude, and, to some extent, redshift. We discuss possible theoretical explanations of this phenomenon within the framework of galactic evolution, and, in particular, of radial gas redistribution in barred galaxies. Our conclusions provide further evidence that Seyfert hosts differ systematically from their nonactive counterparts on scales of a few kiloparsecs.

The Unified Model of Active Galactic Nuclei (AGN) has provided a successful explanation for the observed diversity of AGN in the local Universe. However, recent analysis of multi-wavelength spectral and image data suggests that the Unified Model is only a partial theory of AGN, and may need to be augmented to remain consistent with all observations. Recent studies using high spatial resolution ground- and space-based observations of local AGN show that Seyfert class and the "core" (r<~1 kpc) host-galaxy morphology are correlated. Currently, this relationship has only been established qualitatively, by visual inspection of the core morphologies of low redshift (z<0.035) Seyfert host galaxies (Malkan et al. 1998). We re-establish this empirical relationship in Hubble Space Telescope (HST) optical imaging by visual inspection of a catalog of 85 local (D<63 Mpc) Seyfert galaxies. We also attempt to re-establish the core morphology-Seyfert class relationship using an automated, non-parametric technique that combines both existing classification parameters methods (the adapted CAS, G-M20), and a new method which implements the Source Extractor software for feature detection in unsharp-mask images. This new method is designed explicitly to detect dust features in the images. We use our automated approach to classify the morphology of the AGN cores and determine that Sy2 galaxies visually appear, on average, to have more dust features than Sy1. With the exception of this "dustiness" however, we do not measure a strong correlation between the dust morphology and the Seyfert class of the host galaxy using quantitative techniques. We discuss the implications of these results in the context of the Unified Model.

We use isophote analysis performed on near-infrared images of matched samples of Seyfert and non-active galaxies to study the overall bar fractions, and properties of the bars. We conclude that there is a small but significant excess of bars among the host galaxies of Seyferts as compared to non-Seyfert control galaxies. Whereas 59% ± 9% of control galaxies are barred, 79% ± 8% of Seyfert hosts are barred. We also find that the bars in Seyfert galaxies are statistically less elliptical, thus “thicker” or “weaker”, than those in non-active galaxies. Implications for models of fuelling of AGN, as well as possible caveats in the interpretation of our results in that context, are briefly discussed.

view Abstract Citations (81) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Study of the Structure and Kinematics of the Narrow-Line Region in Seyfert Galaxies. II. Analysis of the Line-Profile Parameters Veilleux, Sylvain Abstract The results of the analysis of the line profiles presented in Paper I are reported. It is shown that the line-profile parameters derived from low- resolution data are often greatly affected by the finite width of the instrumental profile. These resolution effects generally result in overestimates of the line widths and underestimates of the line asymmetries. In spite of these important systematic errors, many of the results of low-resolution studies are confirmed in the high-resolution data. The narrow-line profiles of Seyfert galaxies have a stronger base relative to core than a Gaussian. Most of the emission lines present a blueward asymmetry in a lower portion of their profile. The widths of all of the emission lines are correlated with the emission-line/infrared/radio luminosities. None of the profile parameters correlates strongly with the reddening, ionization level, temperature, or density of the gas producing the narrow emission lines. The host galaxy probably plays a role in the kinematics of some of the gas in the narrow-line region. There is a tendency for galaxies with early morphological types to have broader and stubbier line profiles than objects of later types. A correlation is also observed between the [O III] line width and the luminosity of the galactic bulge. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1991 DOI: 10.1086/191535 Bibcode: 1991ApJS...75..383V Keywords: GALAXIES: INTERNAL MOTIONS; GALAXIES: NUCLEI; GALAXIES: SEYFERT; LINE PROFILES full text sources ADS | data products SIMBAD (16) NED (16) Related Materials (2) Part 1: 1991ApJS...75..357V Part 3: 1991ApJ...369..331V

Copper (Cu) interconnect lines are widely used in advanced, high-density ICs. Compared with aluminum (Al), Cu has many advantages, such as the higher conductivity and longer lifetime. However, Cu is difficult to etch into fine lines using the plasma etching method because the reaction product is nonvolatile. Another problem of Cu interconnect is that it has poor adhesion to the dielectric film unless an adhesion layer is used. Recently, Kuo’s group solved the etching problem with a novel room-temperature process that consumes the patterned Cu thin film with a plasma reaction and then removes the reaction product with a liquid solution [1,2]. This method has been used in the fabrication of ICs and TFT LCDs [3]. One of the most critical issues in applying Cu lines in products is the reliability - lifetime prediction, which is usually done by the electromigration (EM) measurement [4]. Previously, the Kuo’s group has studied temperature and mechanical bending effects on the Cu fine line’s lifetime [5,6]. However, there are few studies on the geometry effects of the Cu line on the lifetime. In the paper, authors investigated the relationship between the width or length of the Cu line and the EM lifetime. The TiW (10 nm)/Cu (200 nm) thin film stack was sputter deposited on a Corning glass. The TiW film was deposition at 5 mTorr in Ar at 75 W for 15 minutes. The Cu film was deposited at 10 mTorr in Ar at 80W for 60 minutes. The Cu film was patterned with a lithography process using a line-and-space mask. Then, the sample was exposed to a Cl2 /CF4 plasma in the PlasmaTherm 700C system operated in the RIE mode at room temperature. The condition was Cl2/CF4 10/5 sccm at 50 mTorr, 600 W for 3 minutes, corresponding to -VDC = 237 V [7]. After the RIE reaction, the sample was dipped in the 10:1 diluted HCl solution to dissolve the CuClx reaction product. Then, the underneath TiW was RIE etched with CF4 5 sccm at 40 mTorr, 600W for 2 minutes corresponding to -VDC = 273V. The failure time was determined by stressing a sample with the constant current density at room temperature until the current suddenly jumped by several orders of magnitude. Relationships between the line width or length and the EM failure time at different current densities were measured, as shown in Figures 1 and 2, where “L” means the line length and “W” means the line width. Several conclusions can be summarized from these figures. First, the line failure time is shortened with the increase of the current density. Second, under the same current density, the narrow line has a longer lifetime than the wide line. Third, the influence of the line length to the failure time is highly dependent on the line width. In Fig. 1, for 30 µ wide lines, the 800 µ long line has a slightly longer lifetime than that of the 400 µ long line. However, in Fig. 2, for 10 µ wide lines, the 20 µ long line has a lifetime slightly longer than that of the 200 µ long line at the current density of 2.5x106 A/cm2. Separately, for the same 20 µ line length, the lifetime of the 3 µ wide line is longer than that of the 10 µ wide line. For all 10 µ wide lines, the lifetime appears to be longer with the shortening of the line length. The further study on the Cu line width and length effect for narrow Cu lines, i.e., less than 3 µ, is in progress of which the result will be reported. In addition, the breakdown of the Cu line may be related to the edge roughness or the TiW/Cu interface quality, which will also be clarified and reported. Authors acknowledge to support of this work through the NSF CMMI 1633580 project. 1. Y. Kuo and S. Lee, Jpn. J. Appl. Phys. 39(3AB), L188-L190 (2000). 2. Y. Kuo and S. Lee, Appl. Phys. Lett., 78(7), 1002-1004 (2001). 3. Y. Kuo, invited, Proc. 16th Intl. Workshop on Active-Matrix Flat Panel Displays and Devices, 211-214 (2009). 4. J. R. Black, IEEE Reliability Physics Symposium, 142-149 (1974). 5. G. Liu and Y. Kuo, Electrochem. Soc., 156(7), H579-H584. (2009). 6. C. C. Lin and Y. Kuo., Journal of Applied Physics 111(6), 265-10130 (2012). 7. S. Lee and Y. Kuo, Electrochem. Soc., 148(9), G524-G529 (2001). Figure 1

We search for possible correlations between luminosity, extinction, and morphological-related properties of 246 Seyfert and starburst galaxies. In particular, we investigate the relation between [O III] λ5007 profile asymmetry and dust-related signatures, and between line and continuum luminosities and tidal perturbations on the host galaxies. We find that line asymmetry is well-correlated with Hα/Hβ flux ratios in Seyfert 2's, and with 60 microns/[O III] λ5007 flux ratios in both Seyfert types, which suggest that the media responsible for emission-line attenuation, for profile asymmetry, and for far-infrared emission are intimately related. Although these correlations are statistically significant, the scatter is large in many instances. We also find a positive correlation between soft X-ray luminosities and optical reddening for Seyfert 2's and a negative correlation for Seyfert 1's. These and other correlations are discussed in the context of current models of active nuclei. No similar correlations were found in the starburst sample. We find that there are no statistically significant differences between Seyferts with and without companions, except that interacting Seyfert 2's have excess infrared and radio-continuum emission. Optical and X-ray luminosities for both types are uncorrelated with tidal parameters, although luminosities for Seyferts with companions are marginally higher than for those without.

Obscured active galactic nuclei, which are classified optically as type 2 (narrow-line) Seyfert galaxies in the local universe, are by far the most promising candidates for the origin of the hard (2-10 keV) X-ray background radiation. However, optical follow-up observations of faint X-ray sources in deep Chandra images have revealed surprising numbers of apparently normal galaxies at modest redshift. Such objects represent ~40-60% of the sources classified in deep Chandra surveys, raising the possibility that the X-ray galaxy population has evolved with cosmic time. Alternatively, most of the faint X-ray galaxies in question are so distant that their angular diameters are comparable to the slit widths used in ground-based spectroscopic observations; thus, their nuclear spectral features may be overwhelmed (``hidden'') by host-galaxy light. To test this hypothesis, we have obtained integrated spectra of a sample of nearby, well-studied Seyfert 2 galaxies. The data, which accurately simulate observations of distant Chandra sources, demonstrate convincingly that the defining spectral signatures of Seyfert 2s can be hidden by light from their host galaxies. In fact, 60% of the observed objects would not be classified as Seyfert 2s on the basis of their integrated spectra, similar to the fraction of faint X-ray sources identified with ``normal'' galaxies. Thus, the numbers of narrow-line active galaxies in deep Chandra surveys (and perhaps all ground-based spectroscopic surveys of distant galaxies) are likely to have been underestimated.

We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (H i) in 16 nearby spiral galaxies hosting low luminosity active galactic nuclei (AGN), observed with high spectral and spatial resolution (resolution: ∼20'', ∼5 km s−1) using the NRAO Very Large Array (VLA). The sample contains a range of nuclear types ranging from Seyfert to star-forming nuclei, and was originally selected for the NUclei of GAlaxies project (NUGA)—a spectrally and spatially resolved interferometric survey of gas dynamics in nearby galaxies designed to identify the fueling mechanisms of AGN and the relation to host galaxy evolution. Here we investigate the relationship between the H i properties of these galaxies, their environment, their stellar distribution, and their AGN type. The large-scale H i morphology of each galaxy is classified as ringed, spiral, or centrally concentrated; comparison of the resulting morphological classification with the AGN type reveals that ring structures are significantly more common in low-ionization narrow emission-line regions (LINER) than in Seyfert host galaxies, suggesting a time evolution of the AGN activity together with the redistribution of the neutral gas. Dynamically disturbed H i disks are also more prevalent in LINER host galaxies than in Seyfert host galaxies. While several galaxies are surrounded by companions (some with associated H i emission), there is no correlation between the presence of companions and the AGN type (Seyfert/LINER).

A northern subsample of 89 Spitzer GLIMPSE extended green objects (EGOs), the\ncandidate massive young stellar objects, are surveyed for molecular lines in\ntwo 1-GHz ranges: 251.5- 252.5 and 260.188-261.188 GHz. A comprehensive catalog\nof observed molecular line data and spectral plots are presented. Eight\nmolecular species are undoubtedly detected: H13CO+, SiO, SO, CH3OH, CH3OCH3,\nCH3CH2CN, HCOOCH3, and HN13C. H13CO+ 3-2 line is detected in 70 EGOs among\nwhich 37 ones also show SiO 6-5 line, demonstrating their association to dense\ngas and supporting the outflow interpretation of the extended 4.5 um excess\nemission. Our major dense gas and outflow tracers (H13CO+, SiO, SO and CH3OH)\nare combined with our previous survey of 13CO, 12CO and C18O 1-0 toward the\nsame sample of EGOs for a multi-line multi- cloud analysis of line width and\nluminosity correlations. Good log-linear correlations are found among all\nconsidered line luminosities, which requires a universal similarity of density\nand thermal structures and probably of shock properties among all EGO clouds to\nexplain. It also requires that the shocks should be produced within the natal\nclouds of the EGOs. Diverse degrees of correlation are found among the line\nwidths. However, both the line width and luminosity correlations tend to\nprogressively worsen across larger cloud subcomponent size-scales, depicting\nthe increase of randomness across cloud subcomponent sizes. Moreover, the line\nwidth correlations among the three isotopic CO 1-0 lines show data scatter as\nlinear functions of the line width itself, indicating that the velocity\nrandomness also increases with whole-cloud sizes and has some regularity\nbehind.\n