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.     

The UKIRT Infrared Deep Sky Survey ZY JHK photometric system: passbands and synthetic colours

We present a statistical study of a very large sample of H  ii galaxies taken from the literature. We focus on the differences in several properties between galaxies that show the auroral line [O  iii ]λ4363 and those that do not present this feature in their spectra. It turns out that objects without this auroral line are more luminous, are more metal-rich and present a lower ionization degree. The underlying population is found to be much more important for objects without the [O  iii ]λ4363 line, and the effective temperature of the ionizing star clusters of galaxies not showing the auroral line is probably lower. We also study the subsample of H  ii galaxies whose properties most closely resemble the properties of the intermediate-redshift population of luminous compact blue galaxies (LCBGs). The objects from this subsample are more similar to the objects not showing the [O  iii ]λ4363 line. It might therefore be expected that the intermediate- redshift population of LCBGs is powered by very massive, yet somewhat aged, star clusters. The oxygen abundance of LCBGs would be greater than the average oxygen abundance of local H  ii galaxies.     

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.     

The host galaxies of active galactic nuclei

We examine the properties of the host galaxies of 22 623 narrow-line active galactic nuclei (AGN) with  0.02 < z < 0.3  selected from a complete sample of 122 808 galaxies from the Sloan Digital Sky Survey. We focus on the luminosity of the [O  iii ]λ5007 emission line as a tracer of the strength of activity in the nucleus. We study how AGN host properties compare with those of normal galaxies and how they depend on L [O  iii ]. We find that AGN of all luminosities reside almost exclusively in massive galaxies and have distributions of sizes, stellar surface mass densities and concentrations that are similar to those of ordinary early-type galaxies in our sample. The host galaxies of low-luminosity AGN have stellar populations similar to normal early types. The hosts of high-luminosity AGN have much younger mean stellar ages. The young stars are not preferentially located near the nucleus of the galaxy, but are spread out over scales of at least several kiloparsecs. A significant fraction of high-luminosity AGN have strong Hδ absorption-line equivalent widths, indicating that they experienced a burst of star formation in the recent past. We have also examined the stellar populations of the host galaxies of a sample of broad-line AGN. We conclude that there is no significant difference in stellar content between type 2 Seyfert hosts and quasars (QSOs) with the same [O  iii ] luminosity and redshift. This establishes that a young stellar population is a general property of AGN with high [O  iii ] luminosities.     

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.     

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.     

Oxygen and helium abundances in Galactic H ii regions – I. Observations

Absolute integrated line fluxes of H  ii regions have been measured using a Fabry–Perot spectrophotometer. We describe the observations and calibration procedures. Fluxes are given for 36 H  ii regions with Galactocentric distances ranging from 6.6 to 17.7 kpc. Several emission lines have been measured, mainly [O  ii ] λλ 3726 and 3629, H β , [O  iii ] λ 5007, He  i λ 5876 and H α . The very faint [O  iii ] λ 4363 line has been measured in six regions, allowing a direct determination of the electron temperature. New photometric distances have been derived based on data from the literature. A discussion of these results in terms of extinction, electron density and temperature, and oxygen and helium abundances is given in Paper II.     

Nebular emission-line profiles of Type Ib/c supernovae – probing the ejecta asphericity

In order to assess qualitatively the ejecta geometry of stripped-envelope core-collapse supernovae (SNe), we investigate 98 late-time spectra of 39 objects, many of them previously unpublished. We perform a Gauss-fitting of the [O  i ]  λλ6300, 6364  feature in all spectra, with the position, full width at half maximum and intensity of the  λ6300  Gaussian as free parameters, and the  λ6364  Gaussian added appropriately to account for the doublet nature of the [O  i ] feature. On the basis of the best-fitting parameters, the objects are organized into morphological classes, and we conclude that at least half of all Type Ib/c SNe must be aspherical. Bipolar jet models do not seem to be universally applicable, as we find too few symmetric double-peaked [O  i ] profiles. In some objects, the [O  i ] line exhibits a variety of shifted secondary peaks or shoulders, interpreted as blobs of matter ejected at high velocity and possibly accompanied by neutron-star kicks to assure momentum conservation. At phases earlier than ∼200 d, a systematic blueshift of the [O  i ]  λλ6300, 6364  line centroids can be discerned. Residual opacity provides the most convincing explanation of this phenomenon, photons emitted on the rear side of the SN being scattered or absorbed on their way through the ejecta. Once modified to account for the doublet nature of the oxygen feature, the profile of Mg  i ]  λ4571  at sufficiently late phases generally resembles that of [O  i ]  λλ6300, 6364  , suggesting negligible contamination from other lines and confirming that O and Mg are similarly distributed within the ejecta.     

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.     

Star formation rates and chemical abundances of emission-line galaxies in intermediate-redshift clusters

We examine the evolutionary status of luminous, star-forming galaxies in intermediate-redshift clusters by considering their star formation rates (SFRs) and the chemical and ionization properties of their interstellar emitting gas. Our sample consists of 17 massive, star-forming, mostly disc galaxies with   M_B ≲−20  , in clusters with redshifts in the range  0.31 ≲ z ≲ 0.59  , with a median of  〈 z 〉= 0.42  . We compare these galaxies with the identically selected and analysed intermediate-redshift field sample of Mouhcine et al., and with local galaxies from the Nearby Field Galaxy Survey of Jansen et al.
From our optical spectra, we measure the equivalent widths of  [O  ii ]λ3727, Hβ  and [O  iii ]λ5007 emission lines to determine diagnostic line ratios, oxygen abundances and extinction-corrected SFRs. The star-forming galaxies in intermediate-redshift clusters display emission-line equivalent widths which are, on average, significantly smaller than measured for field galaxies at comparable redshifts. However, a contrasting fraction of our cluster galaxies have equivalent widths similar to the highest observed in the field. This tentatively suggests a bimodality in the SFRs per unit luminosity for galaxies in distant clusters. We find no evidence for further bimodalities, or differences between our cluster and field samples, when examining additional diagnostics and the oxygen abundances of our galaxies. This maybe because no such differences exist, perhaps because the cluster galaxies which still display signs of star formation have recently arrived from the field. In order to examine this topic with more certainty, and to further investigate the way in which any disparity varies as a function of cluster properties, larger spectroscopic samples are needed.     

Gas properties of H ii and starburst galaxies: relation with the stellar population

We study the gas emission of galaxies with active star formation, consisting mostly of H  ii and starburst galaxies, as well as some Seyfert 2 galaxies, and determine chemical and physical parameters. The data consist of 19 high signal-to-noise ratio optical templates, a result of grouping 185 emission-line galaxy spectra. Underlying stellar population models (from Raimann et al.) were subtracted from the templates in order to isolate the pure emission component.
We analyse the distribution of these improved signal-to-noise ratio emission spectra in diagnostic diagrams and find that the H  ii templates show a smaller spread in log([O  iii ]/H β ) values than the individual galaxies, apparently as a result of the population subtraction and a better signal-to-noise ratio. We thus suggest the template sequence as a fiducial observational locus for H  ii galaxies which can be used as reference for models. The sequence of line ratios presented by the H  ii galaxies in the diagram log([O  iii ] λ 5007/H β ) versus log([N  ii ] λ 6584/H α ) is primarily owing to the gas metallicity, of which the log([N  ii ]/H α ) ratio is a direct estimator. We also study the properties of the starburst galaxies and those intermediate between H  ii and starburst galaxies, which are more metal rich and sit on more massive galaxies.
We discuss the present results in the frame of a recently proposed equivalent-width diagnostic diagram for emission-line galaxies (by Rola et al.) and conclude that the observed ranges in W ([O  ii ])/ W (H β ) and W (H β ) are mostly owing to the non-ionizing stellar population contribution. We propose that W (H β ) be used as an estimator of this contribution to the continuum, and briefly discuss implications to the cosmological use of H  ii galaxies.     

Hα photometry of Abell 2390

We present the results of a search for strong H α emission line galaxies (rest frame equivalent widths greater than 50 Å) in the z ≈0.23 cluster Abell 2390. The survey contains 1189 galaxies over 270 arcmin², and is 50 per cent complete at M _r ≈−17.5+5 log  h . The fraction of galaxies in which H α is detected at the 2 σ level rises from 0.0 in the central regions (excluding the cD galaxy) to 12.5±8 per cent at R ₂₀₀. For 165 of the galaxies in our catalogue, we compare the H α equivalent widths with their [O  ii ] λ 3727 equivalent widths, from the Canadian Network for Observational Cosmology (CNOC1) spectra. The fraction of strong H α emission line galaxies is consistent with the fraction of strong [O  ii ] emission galaxies in the CNOC1 sample: only 2±1 per cent have no detectable [O  ii ] emission and yet significant (>2 σ ) H α equivalent widths. Dust obscuration, non-thermal ionization, and aperture effects are all likely to contribute to this non-correspondence of emission lines. We identify six spectroscopically 'secure' k+a galaxies [ W ₀(O  ii )<5 Å and W ₀(H δ )≳5 Å]; at least two of these show strong signs in H α of star formation in regions that are covered by the slit from which the spectra were obtained. Thus, some fraction of galaxies classified as k+a based on spectra shortward of 6000 Å are likely to be undergoing significant star formation. These results are consistent with a 'strangulation' model for cluster galaxy evolution, in which star formation in cluster galaxies is gradually decreased, and is neither enhanced nor abruptly terminated by the cluster environment.     

Stellar velocity dispersion in narrow-line Seyfert 1 galaxies

Several authors have recently explored, for narrow-line Seyfert 1 galaxies (NLS1s), the relationship between black hole mass ( M _BH) and stellar velocity dispersion (σ_*). Their results are more or less in agreement and seem to indicate that NLS1s fill the region below the fit obtained by Tremaine et al., showing a range of σ_* similar to that of Seyfert 1 galaxies, and a lower M _BH. Until now, the [O  iii ] width has been used in place of the stellar velocity dispersion, but some indications have begun to arise against the effectiveness of the gaseous kinematics in representing the bulge potential, at least in NLS1s. Bian & Zhao have stressed the urgency of producing true σ_* measurements. Here, we present new stellar velocity dispersions obtained through direct measurements of the Ca  ii absorption triplet (∼8550 Å) in the nuclei of eight NLS1 galaxies. The resulting σ_* values and a comparison with σ_[O III] confirm our suspicion that [O  iii ] typically overestimates the stellar velocity dispersion. We demonstrate that NLS1s follow the   M _BH–σ_*  relation as Seyfert 1, quasars and non-active galaxies.     

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.     

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.     

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.     

Optical integral field spectroscopy of the extended line emission around six radio-loud quasars

We present integral field spectroscopy of a small sample of radio-loud quasars at intermediate redshift (0.26< z <0.60), most of which are associated with large radio sources. All have oxygen line emission extended over tens of kpc, and these nebulae display a diverse range in both morphology and kinematic behaviour. Two quasars show 'plumes' of extended line emission, two show a clumpy structure and a further one shows a smooth distribution. There is no clear pattern with regard to the distribution of the ionized gas in relation to the radio source axis; the extended emission-line regions are found both parallel and perpendicular – and also totally unrelated to – the radio axis. The velocity structure of the ionized gas ranges from essentially static to apparent smooth rotation, and in two cases shows a clear association with the radio source. Given the disparity in properties, the nebulae all show a surprisingly similar ionization state, as measured by the extended lines of [O  ii ] λ 3727 and [O  iii ] λ 5007. Assuming the gas is ionized by at least the nearby quasar nucleus, we use the emission line ratios to infer a pressure in the ionized gas; in all cases we find it to be at high pressure, suggesting confinement by an external (probably intracluster) medium.     

Planetary nebula velocities in the disc and bulge of M31

We present radial velocities for a sample of 723 planetary nebulae in the disc and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel Telescope. Velocities are determined using the [O  iii ] λ5007 emission line. Rotation and velocity dispersion are measured to a radius of 50 arcmin (11.5 kpc), the first stellar rotation curve and velocity dispersion profile for M31 to such a radius. Our kinematics are consistent with rotational support at radii well beyond the bulge effective radius of 1.4 kpc, although our data beyond a radius of 5 kpc are limited. We present tentative evidence for kinematic substructure in the bulge of M31 to be studied fully in a later work. This paper is part of an ongoing project to constrain the total mass, mass distribution and velocity anisotropy of the disc, bulge and halo of M31.     

On the relation between electron temperatures in the O+ and O++ zones in high-metallicity H ii regions

We suggest a new way to establish the relation between the electron temperature t ₃ within the [O  iii ] zone and the electron temperature t ₂ within the [O  ii ] zone in high-metallicity  (12 + log(O/H) > 8.25)  H  ii regions. The   t ₂– t ₃  diagram is constructed by applying our method to a sample of 372 H  ii regions. We find that the correlation between t ₂ and t ₃ is tight and can be approximated by a linear expression. The new   t ₂– t ₃  relation can be used to determine t ₂ and accurate abundances in high-metallicity H  ii regions with a measured t ₃. It can also be used in conjunction with the ff relation for the determination of t ₃ and t ₂ and oxygen abundances in high-metallicity H  ii regions, where the [O  iii ]λ4363 auroral line is not detected. The derived   t ₂– t ₃  relation is independent of photoionization models of H  ii regions.     

Emission-line properties of Seyfert 2 nuclei

This is the third paper of a series devoted to the study of the global properties of Joguet's sample of 79 nearby galaxies observable from the southern hemisphere, of which 65 are Seyfert 2 galaxies. We use the population synthesis models of Paper II to derive 'pure' emission-line spectra for the Seyfert 2 galaxies in the sample, and thus explore the statistical properties of the nuclear nebular components and their relation to the stellar populations. We find that the emission-line clouds suffer substantially more extinction than the starlight, and we confirm the correlations between stellar and nebular velocity dispersions and between emission-line luminosity and velocity dispersions, although with substantial scatter. Nuclear luminosities correlate with stellar velocity dispersions, but Seyferts with conspicuous star-forming activity deviate systematically towards higher luminosities. Removing the contribution of young stars to the optical continuum produces a tighter and steeper relation,   L ∝σ⁴_★  , consistent with the Faber–Jackson law.
Emission-line ratios indicative of the gas excitation such as [O  iii ]/Hβ and [O  iii ]/[O  ii ] are statistically smaller for Seyferts with significant star formation, implying that ionization by massive stars is responsible for a substantial and sometimes even a dominant fraction of the Hβ and [O  ii ] fluxes. We use our models to constrain the maximum fraction of the ionizing power that can be generated by a hidden active galactic nucleus (AGN). We correlate this fraction with classical indicators of AGN photoionization (i.e. X-ray luminosity and nebular excitation), but find no significant correlations. Thus, while there is a strong contribution of starbursts to the excitation of the nuclear nebular emission in low-luminosity Seyferts, the contribution of the hidden AGN remains elusive even in hard X-rays.