Evolutionary unification in composite active galactic nuclei

In this paper, we present an evolutionary unification scenario, involving supermassive black holes (SMBHs) and starbursts (SBs) with outflow (OF), that seems capable of explaining most of the observational properties (of at least part) of active galactic nuclei (AGN).
The scenario includes a nuclear/circumnuclear SB closely associated with the AGN where the narrow-line region (NLR), broad-line region (BLR) and broad absorption line (BAL) region are produced in part by the OF process with shells and in compact supernova remnants (cSNRs).
The OF process in BAL quasi-stellar objects (QSOs) with extreme infrared (IR) and Fe  ii emission is studied. In addition, the Fe  ii problem regarding the BLR of AGN is analysed. The correlations between the BAL, IR emission, Fe  ii intensity and the intrinsic properties of the AGN are not clearly understood. We suggest here that the behaviour of the BAL, IR and Fe  ii emission in AGN can be understood within an evolutionary and composite model for AGN.
In our model, strong BAL systems and Fe  ii emission are present (and intense) in young IR objects. Parameters like the BALs, IR emission, Fe  ii /Hβ intensity ratio, Fe  ii equivalent width (EW), broad-line width, [O  iii ]λ5007-Å intensity and width, NLR size, X-ray spectral slope in radio quiet (RQ) AGN plus lobe separation, and lobe to core intensity ratio in radio loud (RL) AGN are proposed to be fundamentally time-dependent variables inside time-scales of the order of 10⁸ yr. Orientation/obscuration effects take the role of a second parameter providing the segregation between Seyfert 1/Seyfert 2 galaxies (Sy1/Sy2) and broad-/narrow-line radio galaxies (BLRG/NLRG).     

Near-infrared spectra of Seyfert galaxies and line production mechanisms

New observations are reported of J -band spectra (1.04–1.4 μm) of three Seyfert 2 galaxies, Mkn 34, Mkn 78 and NGC 5929. In each case the spectral range includes the near-infrared lines of [Fe  ii ], [P  ii ], He  i and Paβ. Each Seyfert galaxy has a known radio jet, and we investigate the infrared line ratios of the nuclear and extended regions of each galaxy compared to the radio structure. In Mkn 34 there is a clear indication of an extranuclear region, probably coincident with a shock induced by the radio jet, in which [Fe  ii ] is considerably enhanced, although the nuclear emission is almost certainly the result of photoionization by the continuum of the active nucleus. Similar effects in extranuclear regions are seen in the other objects, in the case of Mkn 78 confirming recent studies by Ramos Almeida et al. A possible detection of extranuclear [P  ii ] emission suggests, if real, that photoionization by the active nucleus is the dominant line excitation mechanism over the whole source, including the regions coincident with the radio jet.     

Emission-line outflows in PKS1549−79: the effects of the early stages of radio-source evolution?

We present new spectroscopic observations of the southern radio galaxy         . Despite the flat-spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and non-stellar continuum characteristic of quasar nuclei and broad-line radio galaxies. However, the high-ionization forbidden lines, including [O  iii ] λλ 5007, 4959, are unusually broad for a narrow-line radio galaxy     , and are blueshifted by 600 km s⁻¹ relative to the low-ionization lines such as [O  ii ] λλ 3726,3729. The [O  ii ] lines are also considerably narrower     than the [O  iii ] lines, and have a redshift consistent with that of the recently detected H  i 21-cm absorption-line system. Whereas the kinematics of the [O  iii ] emission lines are consistent with outflow in an inner narrow-line region, the properties of the [O  ii ] emission lines suggest that they are emitted by a more extended and quiescent gaseous component. We argue that, given the radio properties of the source, our line of sight is likely to be lying close to the direction of bulk outflow of the radio jets. In this case it is probable that the quasar nucleus is entirely obscured at optical wavelengths by the material responsible for the H  i absorption-line system. The unusually broad [O  iii ] emission lines suggest that the radio source is intrinsically compact. Overall, our data are consistent the idea that     is a radio source in an early stage of evolution.     

Stellar indices and kinematics in Seyfert 1 nuclei

We present spectra of six type 1 and two type 2 Seyfert galaxies, a starburst galaxy and a compact narrow-line radio galaxy, taken in two spectral ranges centred around the near-infrared Ca  ii triplet (∼8600 Å), and the Mgb stellar feature at 5180 Å. We measured the equivalent widths (EWs) of these features and the Fe₅₂ and Fe₅₃ spectral indices.
We found that the strength of the infrared Ca  ii triplet (CaT) in type 1 Seyfert galaxies with prominent central point sources is larger than what would be expected from the observed strength of the blue indices. This could be explained by the presence of red supergiants in the nuclei of Seyfert 1 galaxies. On the other hand, the blue indices of these galaxies could also be diluted by the strong Fe  ii multiplets that can be seen in their spectra.
We have also measured the stellar‐ and gas-velocity dispersions of the galaxies in the sample. The stellar velocity dispersions were measured using both the Mgb and CaT stellar features. The velocity dispersion of the gas in the narrow-line region (NLR) was measured using the strong emission lines [O  iii ] λλ 5007, 4959 and [S  iii ] λ 9069. We compare the gas- and star-velocity dispersions and find that the magnitudes of both are correlated in Seyfert galaxies.
Most of the Seyfert 1 galaxies that we observe have stellar‐velocity dispersions somewhat greater than that of the gas in the NLR.     

AGN with strong forbidden high-ionization lines selected from the Sloan Digital Sky Survey

We have defined a sample of 63 active galactic nuclei with strong forbidden high-ionization line (FHIL) emission. These lines, with ionization potentials  ≳100  eV, respond to a portion of the spectrum that is often difficult to observe directly, thereby providing constraints on the extreme ultraviolet-soft X-ray continuum. The sources are selected from the Sloan Digital Sky Survey (SDSS) on the basis of their [Fe  x ]λ6374 Å emission, yielding one of the largest and the most homogeneous samples of FHIL-emitting galaxies. We fit a sequence of models to both FHILs ([Fe  xi ], [Fe  x ] and [Fe  vii ]) and lower ionization emission lines ([O  iii ], [O  i ],  Hα  , [N  ii ], [S  ii ]) in the SDSS spectra. These data are combined with X-ray measurements from the ROSAT satellite, which are available for half of the sample. The correlations between these parameters are discussed for both the overall sample and subsets defined by spectroscopic classifications. The primary results are evidence that (1) the [Fe  x ] and [Fe  xi ] lines are photoionized and their strength is proportional to the continuum flux around 250 eV, (2) the FHIL-emitting clouds form a stratified outflow in which the [Fe  x ] and [Fe  xi ] source regions extend sufficiently close to the broad-line region that they are partially obscured in Seyfert 2s, whereas the [Fe  vii ] source region is more extended and is unaffected by obscuration, (3) narrow-lined Seyfert 1s (NLS1s) tend to have the strongest [Fe  x ] flux (relative to lower ionization lines) and (4) the most extreme [Fe  x ] ratios (such as [Fe  x ]/[O  iii ] or [Fe  x ]/[Fe  vii ]) are found in the NLS1s with the narrowest broad lines and appear to be an optical-band indication of objects with strong X-ray soft excesses.     

X-ray absorption in the strong Fe ii narrow-line Seyfert 1 galaxy Markarian 507

We present results from spectral analysis of ASCA data on the strong Fe  ii narrow-line Seyfert 1 galaxy Mrk 507. This galaxy was found to have an exceptionally flat ROSAT spectrum among the narrow-line Seyfert 1 galaxies (NLS1s) studied by Boller, Brandt & Fink. The ASCA spectrum, however, shows a clear absorption feature in the energy band below 2 keV, which partly accounts for the flat spectrum observed with the ROSAT Position Sensitive Proportional Counter (PSPC). Such absorption is rarely observed in other NLS1s. The absorption is mainly the result of cold (neutral or slightly ionized) gas with a column density of (2–3) × 10²¹ cm⁻². A reanalysis of the PSPC data shows that an extrapolation of the best-fitting model for the ASCA spectrum underpredicts the X-ray emission observed with the PSPC below 0.4 keV if the absorber is neutral (which indicates that the absorber is slightly ionized), covers only part of the central source, or there is extra soft thermal emission from an extended region. There is also evidence that the X-ray absorption is complex; an additional edge feature marginally detected at 0.84 keV suggests the presence of an additional high-ionization absorber, which imposes a strong O  viii edge on the spectrum. After correction for the absorption, the photon index of the intrinsic continuum, Γ ≃ 1.8, obtained from the ASCA data is quite similar to that of ordinary Seyfert 1 galaxies. Mrk 507 still has one of the flattest continuum slopes among the NLS1s, but is no longer exceptional. The strong optical Fe  ii emission remains unusual in the light of the correlation between Fe  ii strengths and steepness of soft X-ray slope.     

Near-infrared [Fe ii] emission from supernova remnants and the supernova rate of starburst galaxies

In an effort better to calibrate the supernova rate of starburst galaxies as determined from near-infrared [Fe  ii ] features, we report on a [Fe  ii ] λ 1.644 μm line-imaging survey of a sample of 42 optically selected supernova remnants (SNRs) in M33. A wide range of [Fe  ii ] luminosities are observed within our sample (from less than 6 to 695 L_⊙). Our data suggest that the bright [Fe  ii ] SNRs are entering the radiative phase and that the density of the local interstellar medium (ISM) largely controls the amount of [Fe  ii ] emission. We derive the following relation between the [Fe  ii ] λ 1.644 μm line luminosity of radiative SNRs and the electronic density of the post-shock gas, n _e: L _{[Fe  ii ]}     (cm⁻³). We also find a correlation in our data between L _{[Fe  ii ]} and the metallicity of the shock-heated gas, but the physical interpretation of this result remains inconclusive, as our data also show a correlation between the metallicity and n _e. The dramatically higher level of [Fe  ii ] emission from SNRs in the central regions of starburst galaxies is most likely due to their dense environments, although metallicity effects might also be important. The typical [Fe  ii ]-emitting lifetime of a SNR in the central regions of starburst galaxies is found to be of the order of 10⁴ yr. On the basis of these results, we provide a new empirical relation allowing the determination of the current supernova rate of starburst galaxies from their integrated near-infrared [Fe  ii ] luminosity.     

X-ray synchrotron emission from the oblique shock in the jet of the powerful radio galaxy 3C 346

We report the first detection, with Chandra , of X-ray emission from the jet of the powerful narrow-line radio galaxy 3C 346. X-rays are detected from the bright radio and optical knot at which the jet apparently bends by approximately 70°. The Chandra observation also reveals a bright galaxy-scale atmosphere within the previously known cluster and provides a good X-ray spectrum for the bright core of 3C 346. The X-ray emission from the knot is synchrotron radiation, as seen in lower-power sources. In common with these sources, there is evidence of morphological differences between the radio/optical and X-ray structures, and the spectrum is inconsistent with a one-component continuous-injection model. We suggest that the X-ray-bright knot is associated with a strong oblique shock in a moderately relativistic, light jet, at ∼ 20° to the line of sight, and that this shock is caused by the jet interacting with the wake in the cluster medium behind the companion galaxy of 3C 346. The general jet curvature can result from pressure gradients in the cluster atmosphere.     

New, high-resolution, near-infrared observations of HH 1

We present new, high-resolution, near-infrared images of the HH 1 jet and bow shock. H₂ and [Fe  ii ] images are combined to trace excitation changes along the jet and across the many shock features in this flow. Echelle spectra of H₂ profiles towards a few locations in HH 1 are also discussed. Gas excitation in oblique, planar C-type shocks best explains the observations, although J-type shocks must be responsible for the observed [Fe  ii ] emission features. Clearly, no single shock model can account for all of the observations. This will probably be true of most, if not all, Herbig–Haro flows.     

Star formation in southern Seyfert galaxies

We have produced radio maps, using the Australia Telescope Compact Array, of the central regions of six southern type 2 Seyfert galaxies (NGC 1365, 4945, 6221, 6810, 7582 and Circinus) with circumnuclear star formation, to estimate the relative contribution of star formation activity compared to activity from the active galactic nucleus (AGN). The radio morphologies range from extended diffuse structures to compact nuclear emission, with no evidence, even in the relatively compact sources, for synchrotron self-absorption. In each case the radio to far-infrared (FIR) ratio has a value consistent with star formation, and in all but one case the radio to [Fe  II ] ratio is also consistent with star formation. We derive supernova rates and conclude that, despite the presence of a Seyfert nucleus in these galaxies, the radio, FIR and [Fe  II ] line emissions are dominated by processes associated with the circumnuclear star formation (i.e. supernova remnants and H  II regions) rather than with the AGN.     

The quasar fraction in low-frequency-selected complete samples and implications for unified schemes

Low-frequency radio surveys are ideal for selecting orientation-independent samples of extragalactic sources because the sample members are selected by virtue of their isotropic steep-spectrum extended emission. We use the new 7C Redshift Survey along with the brighter 3CRR and 6C samples to investigate the fraction of objects with observed broad emission lines – the 'quasar fraction'– as a function of redshift and of radio and narrow-emission-line luminosity. We find that the quasar fraction is more strongly dependent upon luminosity (both narrow-line and radio) than it is on redshift. Above a narrow [O  ii ] emission-line luminosity of log₁₀( L _{[O  ii ]}/W)≳35 [or radio luminosity log₁₀( L ₁₅₁/W Hz⁻¹ sr⁻¹)≳ 26.5], the quasar fraction is virtually independent of redshift and luminosity; this is consistent with a simple unified scheme with an obscuring torus with a half-opening angle θ _trans≈53°. For objects with less luminous narrow lines, the quasar fraction is lower. We show that this is not due to the difficulty of detecting lower luminosity broad emission lines in a less luminous, but otherwise similar, quasar population. We discuss evidence which supports at least two probable physical causes for the drop in quasar fraction at low luminosity: (i) a gradual decrease in θ _trans and/or a gradual increase in the fraction of lightly reddened (0≲ A _V ≲5) lines of sight with decreasing quasar luminosity; and (ii) the emergence of a distinct second population of low-luminosity radio sources which, like M87, lack a well-fed quasar nucleus and may well lack a thick obscuring torus.     

M BH–σ relation in Sloan Digital Sky Survey flat-spectrum radio quasars

The relationship between the black hole mass and velocity dispersion indicated with [O  iii ] linewidth is investigated for a sample of 87 flat-spectrum radio quasars selected from the Sloan Digital Sky Survey Data Release 3 quasar catalogue. We found that the   M _BH−σ_[O III]  relation is different from the Tremaine et al. relation for nearby inactive galaxies, with a larger black hole mass at given velocity dispersion. There is no strong evidence of cosmology evolution in the   M _BH−σ_[O III]  relation up to   z ∼ 0.8  . A significant correlation between the [O  iii ] luminosity and broad-line region (BLR) luminosity is found. When transferring the [O  iii ] luminosity to narrow-line region (NLR) luminosity, the BLR luminosity is, on average, larger than the NLR one by about one order of magnitude. We found a strong correlation between the synchrotron peak luminosity and NLR luminosity, which implies a tight relation between the jet physics and accretion process.     

Molecular hydrogen emission in Cygnus A

We present J , H and K -band spectroscopy of Cygnus A, spanning 1.0–2.4 μm in the rest-frame and hence several rovibrational H₂, H recombination and [Fe  ii ] emission lines. The lines are spatially extended by up to 6 kpc from the nucleus, but their distinct kinematics indicate that the three groups (H, H₂ and [Fe  ii ]) are not wholly produced in the same gas. The broadest line, [Fe  ii ] λ 1.644, exhibits a non-Gaussian profile with a broad base (FWHM≃1040 km s⁻¹), perhaps because of the interaction with the radio source. Extinctions to the line-emitting regions substantially exceed earlier measurements based on optical H recombination lines.
Hard X-rays from the quasar nucleus are likely to dominate the excitation of the H₂ emission. The results of Maloney, Hollenbach & Tielens are thus used to infer the total mass of gas in H₂ v=1–0 S(1)-emitting clouds as a function of radius, for gas densities of 10³ and 10⁵ cm⁻³, and stopping column densities N _H=10²²–10²⁴ cm⁻². Assuming azimuthal symmetry, at least 2.3×10⁸ M_⊙ of such material is present within 5 kpc of the nucleus, if the line-emitting clouds see an unobscured quasar spectrum. Alternatively, if the bulk of the X-ray absorption to the nucleus inferred by Ueno et al. actually arises in a circumnuclear torus, the implied gas mass rises to ∼10¹⁰ M_⊙. The latter plausibly accounts for 10⁹ yr of mass deposition from the cluster cooling flow, for which within this radius.     

Ultraviolet Fe ii emission in z∼ 2 quasars

We present spectra of six luminous quasars at   z ∼ 2  , covering rest wavelengths 1600−3200 Å. The fluxes of the UV Fe  ii emission lines and Mg  ii λ2798 doublet, the line widths of Mg  ii and the 3000 Å luminosity were obtained from the spectra. These quantities were compared with those of low-redshift quasars at   z = 0.06–0.55  studied by Tsuzuki et al. In a plot of the Fe  ii (UV)/Mg  ii flux ratio as a function of the central black hole mass, Fe  ii (UV)/Mg  ii in our   z ∼ 2  quasars is systematically greater than in the low-redshift quasars. We confirmed that luminosity is not responsible for this excess. It is unclear whether this excess is caused by rich Fe abundance at   z ∼ 2  over low-redshift or by non-abundance effects such as high gas density, strong radiation field and high microturbulent velocity.     

A spectroscopic study of NGC 6251 and its companion galaxies

Measurements of the velocities of galaxies thought to be associated with the giant radio galaxy NGC 6251 confirm the presence of a poor cluster with a systemic redshift of and a line-of-sight velocity dispersion of _z =283(+109,52) km s¹. This suggests a cluster atmosphere temperature of T =0.7(+0.6,0.2) keV, which is not enough to confine the radio jet by gas pressure. The core of NGC 6251 shows strong emission lines of [O  iii ] and H +[N  ii ], but there is no evidence for line emission from the jet (detected in optical continuum by Keel).     

A survey of molecular hydrogen in the central galaxies of cooling flows

We present a large sample of H - and K -band spectra of 32 optically line-luminous central cluster galaxies. We find significant rovibrational H₂ emission in 23 of these galaxies as well as H recombination and/or [Fe  ii ] emission in another five. This represents a fourfold increase in the number of molecular line detections known. A number of the detections are of extended emission (5–20 kpc). In several objects we find significant [Si  vi ] emission that appears to correlate with the strength of high ionization lines in the optical (e.g. [O  iii ]). This comprehensive sample builds on previous work and confirms that warm (1000–2500 K) molecular hydrogen is present wherever there is ionized material in the cores of cooling flows and in most cases it also coincides with CO molecular line emission.     

The gas kinematics in the Mrk 533 nucleus and circumnuclear region: a gaseous outflow

We present an analysis of 3D spectra of Mrk 533, observed with the integral-field spectrograph MultiPupil Fiber Spectrograph (MPFS) and using the Fabry-Perot Interferometer (FPI) of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) 6-m telescope. We found emissions of gas from the active type 2 Seyfert nucleus in the centre and also from the H  ii regions in a spiral structure and a circumnuclear region. The gas kinematics shows regular non-circular motions in the wide range of galactocentric distances from 500 pc up to 15 kpc. The maps of inward and outward radial motions of the ionized gas were constructed. We found that the narrow-line region (NLR) is composed of at least two (probably three) kinematically separated regions. We detect a stratification in the NLR of Mrk 533 with the outflow velocity ranging from 20–50 km s⁻¹ to 600–700 km s⁻¹, respectively, on the radial distances of ∼2.5 and ∼1.5 kpc. The maximal outflow velocity comes from the nucleus and corresponds to the position of the observed radio structure, which is assumed to be created in an approaching jet. We suggest that these ionized gas outflows are triggered by the radio jet intrusion in an ambient medium.     

Identification of newly discovered radio-emitting X-ray sources: results from spectroscopy

We present optical identifications for a sample of 20 previously unknown X-ray/radio sources that are present both in the source catalogue of ROSAT PSPC pointed observations ( ROSAT SRC) and in the NRAO VLA Sky Survey (NVSS). The optical spectroscopy was carried out with the 2.1-m telescope at San Pedro Martir (Mexico) during 1995 April and September. We have identified 15 active galactic nuclei [including 12 broad-emission-line (FWHM >1000 km s⁻¹) objects, one bona fide BL Lac, one BL Lac candidate and one narrow-line (FWHM < 1000 km s⁻¹) radio galaxy] and five radio galaxies. We derive the X-ray fluxes and luminosities by analysing the PSPC exposures, and show the radio morphology from the NVSS maps.  We find that the correlation between the monochromatic X-ray luminosity at 2 keV and the core radio luminosity at 5 GHz for the radio galaxies in our sample follows that found for the 3CR radio galaxies, suggesting a possible nuclear origin for the X-ray emission in these sources. This correlation is weaker in the case of broad-line objects, indicating the presence of another (unbeamed) mechanism for the X-ray emission only weakly related to the radio emission.     

An infrared proper motion study of the Orion bullets

We report the first infrared proper motion measurements of the HerbigHaro objects in OMC-1 using a 4-yr time baseline. The [Fe  ii ]-emitting bullets are moving of the order of 0.08 arcsec per year, or at about 170 km s¹. The direction of motion is similar to that inferred from their morphology. The proper motions of H₂-emitting wakes behind the [Fe  ii ] bullets, and of newly found H₂ bullets, are also measured. H₂ bullets have smaller proper motion than [Fe  ii ] bullets, while H₂ wakes with leading [Fe  ii ] bullets appear to move at similar speeds to their associated bullets. A few instances of variability in the emission can be attributed to dense, stationary clumps in the ambient cloud being overrun, setting up a reverse-oriented bullet. Differential motion between [Fe  ii ] bullets and their trailing H₂ wakes is not observed, suggesting that these are not separating, and also that they have reached a steady-state configuration over at least 100 yr. The most distant bullets have, on average, larger proper motions, but are not consistent with free expansion. Nevertheless, an impulsive, or short-lived (<<1000 yr), duration for their origin seems likely.     

The excitation and kinematical properties of H2 and [Fe ii] in the HH 46/47 bipolar outflow

Long-slit spectra of the molecular outflow Herbig–Haro (HH) 46/47 have been taken in the J and K near-infrared bands. The observed H₂ line emission confirms the existence of a bright and extended redshifted counter-jet outflow south-west of HH 46. In contrast with the optical appearance of this object, we show that this outflow seems to be composed of two different emission regions characterized by distinct heliocentric velocities. This implies an acceleration of the counter-jet.
The observed [Fe  ii ] emission suggests an average extinction of 7–9 visual magnitudes for the region associated with the counter-jet.
Through position–velocity diagrams, we show the existence of different morphologies for the H₂ and [Fe  ii ] emission regions in the northern part of the HH 46/47 outflow. We have detected for the first time high-velocity (−250 km s⁻¹) [Fe  ii ] emission in the region bridging HH 46 to HH 47A. The two strong peaks detected can be identified with the optical positions B8 and HH 47B.
The H₂ excitation diagrams for the counter-jet shock suggest an excitation temperature for the gas of T _ex≈2600 K . The lack of emission from the higher energy H₂ lines, such as the 4–3 S(3) transition, suggests a thermal excitation scenario for the origin of the observed emission. Comparison of the H₂ line ratios with various shock models yielded useful constraints about the geometry and type of these shocks. Planar shocks can be ruled out whereas curved or bow shocks (both J- and C-type) can be parametrized to fit our data.