Extended line emission around seven radio-loud quasars at redshift z ∼ 2

We present near-infrared spectra of seven radio-loud quasars with a median redshift of 2.1, five of which were previously known to have Ly α nebulae. Extended [O  iii ] λ 5007 and H α emission are evident around six objects, at the level of a few times 10⁻¹⁶ erg cm⁻² arcsec⁻² s⁻¹ within ≃2 arcsec of the nucleus (≡16 kpc in the adopted cosmology). Nuclear [O  ii ] λ 3727 is detected in three of the five quasars studied at this wavelength and clearly extended in one of them.
The extended [O  iii ] tends to be brighter on the side of the nucleus with the stronger, jet-like radio emission, indicating at least that the extranuclear gas is distributed anisotropically. It is also typically redshifted by several hundred km s⁻¹ from the nuclear [O  iii ], perhaps because of the latter being blueshifted from the host galaxy's systemic velocity. Alternatively, the velocity shifts could be due to infall (which is suggested by linewidths ∼1000 km s⁻¹ FWHM) in combination with a suitable dust geometry. Ly α /H α ratios well below the case B value suggest that some dust is present.
Photoionization modelling of the [O  iii ]/[O  ii ] ratios in the extended gas suggests that its pressure is around or less than a few times 10⁷ cm⁻³ K; any confining intracluster medium is thus likely to host a strong cooling flow. A comparison with lower redshift work suggests that there has been little evolution in the nuclear emission-line properties of radio-loud quasars between redshifts 1 and 2.     

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.     

A new look at the isotropy of narrow-line emission in extragalactic radio sources

We undertake a quantitative investigation, using Monte Carlo simulations, of the amount by which quasars are expected to exceed radio galaxies in optical luminosity in the context of the 'receding torus' model. We compare these simulations with the known behaviour of the [O  III ] λ5007 and [O  II ] λ3727 emission lines and conclude that [O  III ] is the better indicator of the strength of the underlying non-stellar continuum.     

Late-type galaxies observed with SAURON: two-dimensional stellar and emission-line kinematics of 18 spirals

We present the stellar and gas kinematics of a sample of 18 nearby late-type spiral galaxies (Hubble types ranging from Sb to Sd), observed with the integral-field spectrograph SAURON at the 4.2-m William Herschel Telescope. SAURON covers the spectral range 4800–5380 Å, allowing us to measure the Hβ, Fe, Mg b absorption features and the emission in the Hβ line and the  [O  iii ]λλ4959, 5007 Å  and  [N  i ]λλ5198, 5200 Å  doublets over a  33 × 41-arcsec²  field of view. The maps cover the nuclear region of these late-type galaxies and in all cases include the entire bulge. In many cases the stellar kinematics suggests the presence of a cold inner region, as visible from a central drop in the stellar velocity dispersion. The ionized gas is almost ubiquitous and behaves in a complicated fashion: the gas velocity fields often display more features than the stellar ones, including wiggles in the zero-velocity lines, irregular distributions, ring-like structures. The line ratio [O  iii ]/Hβ often takes on low values over most of the field, probably indicating a wide-spread star formation.     

Overpressured emission-line clouds in the haloes of powerful radio galaxies

We present accurate measurements of the physical conditions in five powerful radio galaxies, as derived from deep, long-slit spectroscopic observations. All five objects show prominent extended line emission, and have X-ray luminosities similar to those of isolated elliptical galaxies. The data are high enough quality that the electron density and temperature can be measured at several positions across the emission-line nebulae.
We subtract a model continuum comprising a combination of a 15-Gyr stellar template, a young stellar template and a power law, so as to be better able to measure faint diagnostic lines. Electron temperatures measured from the [O  iii ](4959+5007)/4363 line ratio are in the range  10 000< T _e<20 000 K  , whilst  [S  ii ](6716/6731)  densities fall between  100–500 cm^-3.  Using these values, we find pressures within the line-emitting clouds a factor of  10–100  times higher than expected for pressure balance with the hot X-ray haloes of the host galaxies.
Previous studies of sources that show significant evidence of jet–cloud interactions, both in terms of their kinematics and ionization, have concluded that the overpressure is a result of the warm, line-emitting gas being compressed by the radio cocoon; however, there is no evidence that the radio jet is influencing the emission-line regions in four of our five objects.
We suggest that it is plausible that the line-emitting clouds have not yet relaxed into pressure equilibrium from their initial photoionization by the central active galactic nucleus.     

Near-infrared spectroscopy of powerful compact steep-spectrum radio sources

We have obtained near-infrared spectroscopy of a small sample of powerful compact steep-spectrum (CSS) radio sources mainly, but not exclusively, from the 3CR sample. We find no differences between the distributions in the equivalent width and luminosity of the [O  iii ]λ5007 line for our sample and other larger, presumably older, high-redshift 3C objects, suggesting that the underlying quasar luminosity remains roughly constant as quasars age. We also find a possible broad line in 3C 241, adding to recent evidence for broad lines in some radio galaxies.     

The relation between extended radio and line emission for radio-loud quasars

We explore the relationship between the extended radio and line emission for a radio-loud quasar sample including both core-dominated and lobe-dominated quasars. A strong correlation is present between the extended radio and broad-line emission. The core emission is also correlated with the broad-line emission for core-dominated quasars in the sample. The statistical behaviour of the core emission of lobe-dominated quasars is rather different from that of core-dominated quasars. The extended radio luminosity is a good tracer for jet power, while the core luminosity can only be a jet power tracer for core-dominated quasars.     

Precision abundance analysis of bright H ii galaxies

We present high signal-to-noise ratio spectrophotometric observations of seven luminous H  ii galaxies. The observations have been made with the use of a double-arm spectrograph which provides spectra with a wide wavelength coverage, from 3400 to 10 400 Å free of second-order effects, of exactly the same region as that of a given galaxy. These observations are analysed applying a methodology designed to obtain accurate elemental abundances of oxygen, sulphur, nitrogen, neon, argon and iron in the ionized gas. Four electron temperatures and one electron density are derived from the observed forbidden line ratios using the five-level atom approximation. For our best objects, errors of 1 per cent in t _e([O  iii ]), 3 per cent in t _e([O  ii ]) and 5 per cent in t _e([S  iii ]) are achieved with a resulting accuracy of 7 per cent in total oxygen abundances, O/H.
The ionization structure of the nebulae can be mapped by the theoretical oxygen and sulphur ionic ratios, on the one side, and the corresponding observed emission line ratios, on the other – the η and η' plots. The combination of both is shown to provide a means to test photoionization model sequences presently applied to derive elemental abundances in H  ii galaxies.     

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.     

An XMM–Newton observation of Mkn 3 – a Seyfert galaxy just over the edge

A 100-ks XMM–Newton observation of the nearby Seyfert 2 galaxy Mkn 3 offers a unique opportunity to explore the complexity of its X-ray spectrum. We find the  ∼3–8 keV  continuum to be dominated by reflection from cold matter, with fluorescent K-shell lines detected from Ni, Fe, Ca, Ar, S, Si and Mg. At higher energies an intrinsic power-law continuum, with canonical Seyfert 1 photon index, is seen through a near-Compton-thick cold absorber. A soft excess below ∼3 keV is found to be dominated by line emission from an outflow of 'warm' gas, photoionized and photoexcited by the intrinsically strong X-ray continuum. Measured blueshifts in the strong Fe Kα and O  vii and O  viii emission lines are discussed in terms of the properties of the putative molecular torus and ionized outflow.     

ASCA observations of two steep soft X-ray quasars

Steep soft X-ray (0.1–2 keV) quasars share several unusual properties: narrow Balmer lines, strong Fe  II emission, large and fast X-ray variability, and a rather steep 2–10 keV spectrum. These intriguing objects have been suggested to be the analogues of Galactic black hole candidates in the high, soft state. We present here results from ASCA observations for two of these quasars: NAB 0205 + 024 and PG 1244 + 026.   Both objects show similar variations (factor of ∼ 2 in 10 ks), despite a factor of ∼ 10 difference in the 0.5–10 keV luminosity (7.3 × 10⁴³ erg s⁻¹ for PG 1244 + 026 and 6.4 × 10⁴⁴ erg s⁻¹ for NAB 0205 + 024, assuming isotropic emission, H ₀ = 50.0 and q ₀ = 0.0).   The X-ray continuum of the two quasars flattens by 0.5–1 going from the 0.1–2 keV band towards higher energies, strengthening recent results on another half-dozen steep soft X-ray active galactic nuclei.   PG 1244 + 026 shows a significant feature in the '1-keV' region, which can be described either as a broad emission line centred at 0.95 keV (quasar frame) or as edge or line absorption at 1.17 (1.22) keV. The line emission could be a result of reflection from a highly ionized accretion disc, in line with the view that steep soft X-ray quasars are emitting close to the Eddington luminosity. Photoelectric edge absorption or resonant line absorption could be produced by gas outflowing at a large velocity (0.3–0.6 c ).     

Emission-line CCD imaging of three southern symbiotic stars

Symbiotic stars that are strong radio sources and have cool dust emitting in the infrared are expected to have extended emission nebulae around them. In order to search for such emission nebulae, we have carried out CCD imaging of three symbiotic stars (R Aqr, RR Tel and H1-36) with narrow-band filters centred at the emission lines of [O III] λ5007, Hα λ6563, [N II] λ6584, [S II] λ6717 + 6731. RR Tel and H1-36 images do not show any extended nebulosities around them. The CCD image of the R Aqr nebulosity in the high excitation [O m] line is different from its image in Hα and the low excitation lines of [N II] and [S II] indicating ionization-stratification in the nebula. In H1-36 the optical nebulosity (if it exists) is smaller than ∽2 arcsec while the radio image size is known to be large (∽5 arcsec). This behaviour is opposite to that seen in R Aqr in which the radio emission comes from the core region of a much larger optical nebulosity. Interstellar and/or circumstellar extinctions are suggested to be responsible for this difference     

Chandra measurements of the X-ray core and cluster of 3C 220.1

We report results of an 18-ks exposure with the ACIS instrument on Chandra of the powerful z =0.62 radio galaxy 3C 220.1. The X-ray emission separates into cluster gas of emission-weighted kT ∼5 keV , 0.7–12 keV luminosity (to a radius of 45 arcsec) of 5.6×10⁴⁴ erg s⁻¹ and unresolved emission (coincident with the radio core). While the extended X-ray emission is clearly thermal in nature, a straightforward cooling-flow model, even in conjunction with a point-source component, is a poor fit to the radial profile of the X-ray emission. This is despite the fact that the measured properties of the gas suggest a massive cooling flow of ∼130 M_⊙ yr⁻¹, and the data show weak evidence for a temperature gradient. The central unresolved X-ray emission has a power-law spectral energy index α ∼0.7 and 0.7–12 keV luminosity of 10⁴⁵ erg s⁻¹, and any intrinsic absorption is relatively small. The two-point spectrum of the core emission between radio and X-ray energies has α _rx=0.75 . Since this is a flatter spectrum than seen in other sources where the X-ray emission is presumed to be radio-related, regions close to the active galactic nucleus (AGN) in this source may dominate the central X-ray output, as is believed to be the case for lobe-dominated quasars. Simple unification models would be challenged if this were found to be the case for a large fraction of high-power radio galaxies.     

Polarization of radio cores and the unified scheme

In the unified scheme for high-luminosity radio galaxies and quasars, the core-dominated quasars are seen at small angles to the line of sight and the lobe-dominated quasars at intermediate angles, while the radio galaxies lie close to the plane of the sky. In radio galaxies, the quasar nucleus is hidden from our view by a putative torus. Such a scenario should also affect the observed polarization properties of the cores, with the core-dominated quasars, lobe-dominated quasars and radio galaxies having progressively lower core polarization at a given frequency and higher rotation measure because of Faraday effects. In this paper, we report that the core polarization of weak-cored quasars has a median value of less than about 0.4 per cent and is indeed much smaller than for core-dominated quasars, where the median value is about 2.5 per cent. We suggest that this might be a result of the depolarization caused by the edge of the obscuring torus or disc. We also examine the relative orientation of the core-polarization E -vector at λ6 cm and the radio axis for the weak-cored quasars. The sample is small but does not show the significant trend reported earlier for cores of moderate strength. This could also be the result of Faraday rotation by the material in the edge of the torus or disc. These results are consistent with the basic ideas of the unified scheme.     

The emission and kinematic structures of the bipolar planetary nebula M 1-8

We have undertaken echelle spectroscopy and narrow-band line imaging of the bipolar planetary nebula M 1-8. This has permitted us to map the outflow in [N  ii ]λλ 6548+6583 Å, Hα, and in the v = 1–0 S(1) transition of H₂ at λ 2.122 μm. It has also permitted us to acquire high-resolution spectra for [N  ii ]λ 6583 Å, Hα and He  ii λ 6560 Å. Our observations support the results of a previous 2MASS analysis by two of the authors (J. P. Phillips and G. Ramos-Larios), and confirm that there is strong H₂ emission outside of the ionized zone, as well as along the major axis of the outflow. Finally, we have investigated the spatial structure of the outflow in low and high excitation lines, and noted evidence for strong ionization stratification within the envelope of the source. We also note that major axis spectra show asymmetries attributable to outflow along the lobes, oriented at an angle i ∼ 35°–40° to the line of sight. Asymmetries along the minor axis, by contrast, appear to be associated with the central collimating disc, and may be interpretable in terms of asymmetries in disc structure, or rotation at an angular velocity of Ω∼ 1.4 10⁻¹² rad s⁻¹. If the disc arises due to common-envelope evolution, then it seems that angular momentum constraints must be relatively tight, and can only be satisfied given fairly extreme physical assumptions (such as low disc mass, high primary star mass, a low distance to the source and so forth).     

Global velocity field and bubbles in the blue compact dwarf galaxy Mrk 86

We have studied the velocity field of the blue compact dwarf galaxy Mrk 86 (NGC 2537) using data provided by 14 long-slit optical spectra obtained in 10 different orientations and positions. This kinematical information is complemented with narrow-band ([O  iii ]5007 Å and H α ) and broad-band ( B , V , Gunn r and K ) imaging. The analysis of the galaxy global velocity field suggests that the ionized gas could be distributed in a rotating inclined disc, with projected central angular velocity of Ω=34 km s⁻¹ kpc⁻¹. The comparison between the stellar, H  i and modelled dark matter density profile indicates that the total mass within its optical radius is dominated by the stellar component. Peculiarities observed in its velocity field can be explained by irregularities in the ionized gas distribution or local motions induced by star formation.
Kinematical evidences for two expanding bubbles, Mrk 86–B and Mrk 86–C, are given. They show expanding velocities of 34 and 17 km s⁻¹, H α luminosities of 3×10³⁸ and 1.7×10³⁹ erg s⁻¹, and physical radii of 374 and 120 pc, respectively. The change in the [S  ii ]/H α , [N  ii ]/H α , [O  ii ]/[O  iii ] and [O  iii ]/H β line ratios with the distance to the bubble precursor suggests a diminution in the ionization parameter and, in the case of Mrk 86–B, an enhancement of the shock-excited gas emission. The optical–near-infrared colours of the bubble precursors are characteristic of low‐metallicity star‐forming regions (∼0.2 Z_⊙) with burst strengths of about 1 per cent in mass.     

Discovery of extended radio emission in the young cluster Wd1

We present 10-μm ISO -SWS and Australia Telescope Compact Array observations of the region in the cluster Wd1 in Ara centred on the B[e] star Ara C. An ISO -SWS spectrum reveals emission from highly ionized species in the vicinity of the star, suggesting a secondary source of excitation in the region. We find strong radio emission at both 3.5 and 6.3 cm, with a total spatial extent of over 20 arcsec. The emission is found to be concentrated in two discrete structures, separated by ∼ 14 arcsec. The westerly source is resolved, with a spectral index indicative of thermal emission. The easterly source is clearly extended and non-thermal (synchrotron) in nature. Positionally, the B[e] star is found to coincide with the more compact radio source, while the southerly lobe of the extended source is coincident with Ara A, an M2 I star. Observation of the region at 10 μm reveals strong emission with an almost identical spatial distribution to the radio emission. Ara C is found to have an extreme radio luminosity in comparison with prior radio observations of hot stars such as O and B supergiants and Wolf–Rayet stars, given the estimated distance to the cluster. An origin in a detatched shell of material around the central star is therefore suggested; however given the spatial extent of the emission, such a shell must be relatively young (τ ∼ 10³ yr). The extended non-thermal emission associated with the M star Ara A is unexpected; to the best of our knowledge this is a unique phenomenon. SAX (2–10 keV) observations show no evidence of X-ray emission, which might be expected if a compact companion were present.     

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.     

On the origin and excitation of the extended nebula surrounding NGC 1275

We use line-of-sight velocity information on the filamentary emission-line nebula of NGC 1275 to infer a dynamical model of the nebula's flow through the surrounding intracluster gas. We detect outflowing gas and flow patterns that match simulations of buoyantly rising bubbles from which we deduce that some of the nebula filaments have been drawn out of NGC 1275. We find a radial gradient of the ratio [N  ii ]λ6584/Hα which may be due to a variation in metallicity, interactions with the surrounding intracluster medium or a hardening of the excitation mechanism. We find no preferred spatial correlation of stellar clusters within the filaments and there is a notable lack of [O  iii ]λ5007 emission, therefore it is unlikely that the filaments are ionized by stellar ultraviolet.     

Are there any Type 2 QSOs? The case of AXJ0341.4–4453

The X-ray source AXJ0341.4–4453 was described by Boyle et al. as a Type 2 active galactic nucleus (AGN) at z =0.672 based on the absence of broad emission lines in the observed wavelength range 4000–7000 Å. We obtained a new spectrum of AXJ0341.4–4453 extending to 9600 Å which reveals broad Balmer lines and other characteristics of Seyfert 1 galaxies. The FWHM of broad H β is at least 1600 km s⁻¹, while [O  iii ] λ 5007 has FWHM=730 km s⁻¹. The flux ratio [O  iii ] λ 5007/H β =1. Thus, AXJ0341.4–4453 is by definition a narrow-line Seyfert 1 galaxy, or perhaps a moderately reddened Seyfert 1 galaxy, but it is not a Type 2 QSO. Although examples of the latter have long been sought, particularly in connection with the problem of the X-ray background, there is still virtually no evidence for the existence of any Type 2 QSO among X-ray selected samples.