Emission-line Gas Research Articles

ChandraX‐Ray Observations of the Inner Optical Filaments in Centaurus A

We have obtained Chandra High Resolution Camera (0.1-10 keV) X-ray imaging of the inner optical filaments of Cen A. Faint X-ray emission is observed associated with the filaments with significance levels of 2-3.5 σ when the data are adaptively smoothed. Comparison with optical [O III] λ5007 emission-line imaging suggests that the X-ray-emitting gas is associated with the northwest edge of the optical line-emitting gas. This region of the filaments is closest to the radio jet and is therefore a candidate for shock heating induced by turbulent instabilities in the interstellar medium. The observed X-ray luminosity is significantly smaller than that predicted by purely radiative shock models of the filaments, implying that mechanical energy input does not provide 100% of the ionizing energy budget for the filaments.

Imaging of the Supernova Remnant Cassiopeia A with the Multiband Imaging Photometer for Spitzer (MIPS)

We present new images of the supernova remnant (SNR) Cas A observed in the 24 and 70 μm bands of the Spitzer Space Telescope (Spitzer). The IR emission correlates well with the Si X-ray and optical [S II] emission but poorly with either the synchrotron-dominated radio structure or the continuum X-ray emission. The IR is therefore dominated by thermal emission from dust within the SNR and associated with emission-line gas inside the reverse shock region, confirming earlier IRAS and Infrared Space Observatory results. Supplemented by new photometric measurements from archived Midcourse Space Experiment images, we suggest stochastic heating to model the overall mid- to far-IR spectral energy distribution. The 24 and 70 μm images also reveal a counterjet to the well-known northeast jet feature imaged previously at X-ray, optical, and radio wavelengths. This IR counterjet corresponds well with (optical) fast-moving knots confirming its outflow nature. The opposing jetlike features define a symmetry axis that bisects the SNR and suggest that the supernova explosion was axisymmetric. The IR images also show a region in which the SNR forward shock appears to be propagating into a ~650 M⊙ molecular cloud. The new images also show other details of the surrounding ISM structure, including two groups of knots extending ~6'-12' on either side of the SNR.

On-axis spectroscopy of thez$\mathsf{=0.144}$ radio-loud quasar HE 1434–1600: an elliptical host with a highly ionized ISM

VLT on-axis optical spectroscopy of the radio-loud quasar HE 1434-1600 is presented. The spatially resolved spectra of the host galaxy are deconvolved and separated from those of the central quasar in order to study the dynamics of the stars and gas as well as the physical conditions of the ISM. We find that the host of HE 1434-1600 is an elliptical galaxy that resides in a group of at least 5 member galaxies, and that most likely experienced a recent collision with its nearest companion. Compared with other quasar host galaxies, HE 1434-1600 has a highly ionized ISM. The ionization state corresponds to that of typical Seyferts, but the ionized regions are not distributed in a homogeneous way around the QSO, and are located preferentially several kiloparsecs away from it. While the stellar absorption lines do not show any significant velocity field, the gas emission lines do. The observed gas velocity field is hard to reconcile with dynamical models involving rotating disk, modified Hubble laws or power laws, that all require extreme central masses () to provide only poor fit to the data. Power law models, which best fit the data, provide a total mass of M(<10 kpc) = 9.2 . We conclude that the recent interaction between HE 1434-1600 and its closest companion has strongly affected the gas velocity and ionization state, from the center of the galaxy to its most external parts.

AHubble Space TelescopeWFPC2 Investigation of the Disk-Halo Interface in NGC 891

We present deep narrowband observations with high spatial resolution of extraplanar diffuse ionized gas in the halo of NGC 891, obtained with the WFPC2 on board the HST. Our Hα observations, centered on the northern part of NGC 891, reveal an extended gaseous halo, which fills almost the entire field of view of our WFPC2 observation. Whereas NGC 891 has been studied extensively with ground-based telescopes, here the small-scale structure of the extended emission-line gas is presented at a high spatial resolution of 01, corresponding to 4.6 pc at the distance to NGC 891. The majority of the Hα emission is diffuse. Several discrete features (e.g., filaments) are visible as well. Some of the filaments reach distances of up to 2.2 kpc above the galactic plane and are extremely collimated, even at high galactic latitudes. We compare the morphology of these filaments with theoretical models, which describe possible transport mechanisms in a general way. Despite the prominent dust lane, many bubbles, shells, and supershells can be discerned in the midplane. We also investigate extraplanar dust features, which are best visible in unsharp-masked images of our broadband F675W image, and we compare them with the spatial distribution of DIG filaments. The high-|z| dust is detected out to distances of 2.2 kpc above/below the galactic midplane. Individual dust features, however, are not spatially correlated with diffuse ionized gas counterparts, such as individual filaments. Quite interestingly, the orientation of the dust features changes from being mostly aligned perpendicular to the disk at low galactic latitudes to a parallel alignment at high |z|. We compare the diffuse ionized gas distribution to the hot ionized medium, traced by X-ray observations performed by Chandra. There exists a good correlation of the presence of the warm and hot ionized gas: in particular, an X-ray bright region at |z| ~ 1–1.5 kpc fills the entire northern halo region, whereas the intensity in the midplane is considerably depressed. We also compare the sizes of individual Hα emission line features in the midplane of NGC 891 with similar structures that are known in our Milky Way and in the LMC.

AGNs in LLAGNs: High resolution radio observations of the Palomar sample

We present completed results of a high resolution radio imaging survey of the Palomar Spectroscopic Sample of all (∼470) nearby bright northern galaxies. Almost half the Palomar sample's galaxies have nuclei with emission-lines characteristic of AGN but with L Hα ≤ 10 40 erg s −1 . These are referred to as low-luminosity AGNs or LLAGNs. The power source of such LLAGNs has been long debated. High resolution radio surveys of the sample – with the VLA at 15 GHz (150 mas resolution), and the VLBA at 5 GHz (2 mas resolution) – have now revealed a high incidence of pc-scale radio cores with implied brightness temperatures [gsim ]10 8 K, and sub-parsec scale jets. The results support the presence of accreting black holes in ≥50% of all LLAGNs; there is no evidence against all LLAGNs being mini-AGNs. The detected parsec-scale radio nuclei are preferentially found in massive ellipticals and in type 1 nuclei (i.e. nuclei with broad Hα emission). These nuclei follow the usual correlations between radio and emission-line gas properties found in more powerful AGNs. The radio luminosity function (RLF) of Palomar Sample LLAGNs extends three orders of magnitude below, and is continuous with, that of ‘classical’ AGNs. We find marginal evidence for a low-power turnover in the RLF; nevertheless LLAGNs are responsible for a significant fraction of accretion in the local universe. Low accretion rates (≤10 −2 −10 −3 of the Eddington rate) are implied in both advection- and jet-type models. Within the context of jet models, the accretion energy output is dominated by the energy in the observed jets rather than the radiated bolometric luminosity. These jets would be able to dump sufficient energy into the innermost parsecs to significantly slow the accretion inflow. Detailed results can be found in Nagar et al. (2002, 2004) and references therein. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Spectral Energy Distribution and Emission‐Line Properties of the Narrow‐Line Seyfert 1 Galaxy Arakelian 564

We present the intrinsic spectral energy distribution (SED) of the NLS1 Arakelian 564, constructed with contemporaneous data obtained during a multi-wavelength, multi-satellite observing campaign in 2000 and 2001. We compare it with that of the NLS1 Ton S180 and with those obtained for BLS1s to infer how the relative accretion rates vary among the Sy1 population. Although the peak of the SED is not well constrained, most of the energy is emitted in the 10-100 eV regime, constituting roughly half of the emitted energy in the optical/X-ray ranges. This is consistent with a primary spectral component peaking in the extreme UV/soft X-ray band, and disk-corona models, hence high accretion rates. Indeed, we estimate that \dot{m}~1. We examine the emission lines in its spectrum, and we constrain the physical properties of the line-emitting gas through photoionization modeling. The line-emitting gas is characterized by log n~11 and log U~0, and is stratified around log U~0. Our estimate of the radius of the H\beta-emitting region ~10 \pm 2 lt-days is consistent with the radius-luminosity relationships found for Sy1 galaxies. We also find evidence for super-solar metallicity in this NLS1. We show that the emission lines are not good diagnostics for the underlying SEDs and that the absorption line studies offer a far more powerful tool to determine the ionizing continuum of AGNs, especially if comparing the lower- and higher-ionization lines.

X‐Ray and Optical Filaments in M87

We compare a very deep X-ray image of M87, at the center of the Virgo Cluster, to high-quality optical images of the low excitation emission-line gas in the same region. There are striking coincidences of detail between the two. We explore the possiblity that this represents a thermal interaction between hot gas at 10^7 K and warm gas at 10^4 K. We find two temperatures are present in the X-ray gas, with the lower more prevelant in the vicinity of the optical filaments. Electron conduction from the hot phase to the cooler one provides a quantitatively acceptable energy source for the optical filaments, and we show additionally that it can do so for the brightest X-ray cluster, Perseus. If operative, conduction in the presence of gas-rich galaxy mergers, may explain the presence of cool cores in clusters of galaxies.

Jet-Gas Interactions in Markarian 78. I. Morphology and Kinematics

We present a detailed study of the Seyfert 2 galaxy Markarian 78, using continuum and emission-line images and multiaperture spectra from the Hubble Space Telescope (HST) and a deep 3.6 cm VLA image. Our overall aim is to study the interaction between the radio source and the emission-line gas, since ground-based data already indicate the presence of a strong bipolar jet-driven flow. First, in the wider context, Mrk 78 is probably a post-merger system, with a nuclear dust lane, approximate r1/4 continuum profile, and highly extended asymmetric gas distribution. The [O III] and radio images both show complex structures with many similarities but also important differences. A careful comparison shows convincing morphological evidence for jet-gas interaction: (1) the western inner radio jet terminates and flares at the position of a bright [O III] knot; (2) the weaker eastern radio jet changes direction as it encounters a large [O III] knot; (3) most [O III] features appear limb brightened on the upstream side, and flared on the downstream side; and (4) in the outer regions the radio components tend to lie between or adjacent to [O III] knots, indicating the radio and line emitting phases do not easily interpenetrate. In addition to evidence of jet-gas interaction, two features indicate the importance of a central ionizing radiation field: an inner fanlike structure to the east, with a straight kinematically quiet northern edge; and an approximately fanlike extended narrow-line region to the west, lying well outside the radio source. The [O III] line profiles from 10 Faint Object Spectrograph apertures provide further kinematic insight into the jet-gas interaction. (1) On the eastern side, where the radio source is deflected, the [O III] profile contains a highly redshifted component (~700 km s-1) that is also narrow (FWHM ≤ 200 km s-1), indicating significant coherent gas acceleration with almost no induced turbulence. (2) At this location, the [O III] profile is also double, suggesting lateral expansion away from a jet axis, as it burrows into the cloud complex. (3) In contrast, the bright western inner knot, which seems to disrupt the inner radio jet, has essentially undisturbed kinematics. (4) Across the outer complex western region, gas velocities are higher in the region center, decrease at the leading edge and may be highest where radio flows blow of the region. Overall, morphology and kinematics suggest the western side is best described as an initially disrupted jet that then fills, accelerates, and leaks out of a complex incomplete bubble of ionized gas. The eastern side is best described as a large centrally illuminated fanlike gas structure that is penetrated, accelerated, and ultimately deflects the radio source. We use these different regions to construct a plausible evolutionary sequence: Initially, a dense (molecular?) cloud enters the jet flow and disrupts it (inner western knot); as time passes, the jet begins to penetrate, accelerate, and ablate the cloud (eastern knot complex); continued jet influence further disperses the cloud fragments, sweeping out channels and gaps (western lobe region). This process may repeat itself many times over the lifetime of the jet. In companion papers, we study the ionization mechanisms and jet properties in more detail using recently acquired Space Telescope Imaging Spectrograph spectra, taking a more complete account of the energetics of the radio source and the ionized gas.

Erratum: “Follow‐UpHubble Space Telescope/Space Telescope Imaging Spectroscopy of Three Candidate Tidal Disruption Events” (ApJ, 592, 42 [2003

The fluxes of the emission lines in the HST/STIS spectra of NGC 5905 given in Table 3 were incorrect by multiplicative factors of 2.5 from the G430L spectrum, and 0.5 from the G750M spectrum. This error does not affect the diagnostic line ratios from neighboring lines or the principal conclusions of the paper. A corrected version of Table 3 is given here. The only quantitative change in interpretation comes from the revised Balmer decrement in the nucleus of NGC 5905, H /H 1⁄4 2:50 0:34, which indicates that there is no reddening in the line of sight, and is now consistent with the lack of X-ray absorption in the ROSAT flare spectrum. Thus, we no longer make extinction corrections, and the density estimates for the lineemitting gas calculated in x 4.3 are lowered. The corrected H luminosity of 5:1 10 ergs s 1 implies fcnH 330 cm , while the corrected [O iii] luminosity of 3:5 10 ergs s 1 implies ne fc 240 cm . These constraints, in addition to the unchanged [S ii] line ratio, which requires ne 500 cm , are consistent with photoionized clouds of nH 10 and a large covering fraction fc. The soft X-ray luminosity predicted in x 4.3 for the Seyfert nucleus in NGC 5905, using the correlation of soft X-ray luminosity with H , is 9 10 ergs s , now an order of magnitude below the lowest value observed by the ROSAT PSPC (LX 2 10 ergs s ). It is still argued that the latter detection might also be partly associated with its nuclear starburst. The corrected luminosity of H is 10 times less than the peak H luminosity powered by the flare as calculated in x 4.3, while He ii k4686 is still not detected and can be assigned an upper limit of 1:5 10 ergs s . These corrected values are still evidence that the emission lines are not powered by the flare; He ii k4686 would be expected to be even stronger than H for gas ionized by the flare. In x 4.4 we referred to the possibility of ‘‘a gross error in the H /H measurement in the STIS spectrum due primarily to stellar absorption in those lines.’’ Instead, there was a numerical error, not a physical one.

Subaru Deep Spectroscopy of the Very Extended Emission-Line Region of NGC 4388: Ram Pressure Stripped Gas Ionized by Nuclear Radiation

We report here the results of deep optical spectroscopy of the very extended emission-line region (VEELR) found serendipitously around the Seyfert 2 galaxy NGC 4388 in the Virgo Cluster using the Subaru Telescope. The Hrecession velocities of most of the filaments of the region observed are highly blueshifted with respect to the systemic velocity of the galaxy. The velocity field is complicated, and from the kinematic and morphological points of view, there seem to be several streams of filaments: low-velocity filaments, with radial velocities v with respect to the systemic velocity of NGC 4388 of roughly � 100 km s � 1 ; high-velocity (v �� 300 km s � 1 ) filaments; and a very high velocity (v �� 500 km s � 1 ) cloud complex. The emission-line ratios of the VEELR filaments are well explained by power-law photoionization models with solar abundances, suggesting that the Seyfert nucleus of NGC 4388 is the dominant ionization source of the VEELR and that the VEELR gas has moderate metallicity. In addition to photoionization, shock heating probably contributes to the ionization of the gas. In particular, the filaments outside the ionization cone of the Seyfert nucleus are mainly excited by shocks. The predicted shock velocity is � 200-300 km s � 1 , which is comparable to the velocities of the filaments. We conclude that the VEELR was formerly the disk gas of NGC 4388, which has been stripped by ram pressure due to the interaction between the hot intracluster medium and the galaxy. The velocity field and the morphology of the VEELR closely resemble snapshots from some numerical simulations of this process. In the case of NGC 4388, the ram pressure stripped gas, which is normally seen as extended Hi filaments, happens to be exposed and ionized by the radiation from the active galactic nucleus, and so can be seen as optical emission-line gas.

AHubble Space TelescopeWFPC2 Investigation of the Nuclear Morphology in the Toomre Sequence of Merging Galaxies

We report on the properties of nuclear regions in the Toomre sequence of merging galaxies, based on imaging data gathered with the Hubble Space Telescope WFPC2 camera. We have imaged the 11 systems in the proposed evolutionary merger sequence in the F555W and F814W broadband filters, and in Hα+[N II] narrowband filters. The broadband morphology of the nuclear regions varies from nonnucleated starburst clumps through dust-covered nuclei to a nucleated morphology. There is no unambiguous trend in the morphology with merger stage. The emission-line morphology is extended beyond the nucleus in most cases, but centrally concentrated (within 1 kpc) emission-line gas can be seen in the four latest-stage merger systems. We have quantified the intrinsic luminosity densities and colors within the inner 100 pc and 1 kpc of each identified nucleus. We find little evidence for a clear trend in nuclear properties along the merger sequence other than a suggestive rise in the nuclear luminosity density in the most evolved members of the sequence. The lack of clear trends in nuclear properties is likely due both to the effects of obscuration and geometry, as well as the physical variety of galaxies included in the Toomre sequence.

A Search for Very Extended Ionized Gas in Nearby Starburst and Active Galaxies

We report the results from a pilot study of 10 nearby starburst and active galaxies conducted with the Taurus Tunable Filter (TTF) on the Anglo-Australian and William Herschel telescopes. The main purpose of this imaging survey is to search for warm emission-line gas on the outskirts (galactocentric distances R 10 kpc) of galaxies to provide direct constraints on the size and geometry of the zone of influence of these galaxies on their environment. Gaseous complexes or filaments larger than ~20 kpc are discovered or confirmed in six of the galaxies in the sample (NGC 1068, 1482, 4388, 6240 and 7213, and MR 2251-178). Slightly smaller structures are seen for the first time in the ionization cones and galactic winds of NGC 1365, NGC 1705, the Circinus galaxy, and ESO 484-G036. The TTF data are combined with new optical long-slit spectra, as well as published and archived radio and X-ray maps, to constrain the origin and source of ionization of these filaments. A broad range of phenomena is observed, including large-scale ionization cones and galactic winds, tidal interaction, and ram-pressure stripping by an intracluster medium. The source of ionization in this gas ranges from shock ionization to photoionization by the central AGN or in situ hot young stars. The sample is too small to draw statistically meaningful conclusions about the extent and properties of the warm ionized medium on a large scale and its relevance to galaxy formation and evolution. The next generation of tunable filters on large telescopes promises to improve the sensitivity to faint emission-line fluxes at least tenfold and allow systematic surveys of a large sample of emission-line galaxies.

ChandraObservations of the Interacting NGC 4410 Galaxy Group

We present high resolution X-ray imaging data from the ACIS-S instrument on the Chandra telescope of the nearby interacting galaxy group NGC 4410. Four galaxies in the inner portion of this group are clearly detected by Chandra, including the peculiar low luminosity radio galaxy NGC 4410A. In addition to a nuclear point source, NGC 4410A contains diffuse X-ray emission, including an X-ray ridge extending out to about 12 (6 kpc) to the northwest of the nucleus. This ridge is coincident with an arc of optical emission-line gas, which has previously been shown to have optical line ratios consistent with shock ionization. This structure may be due to an expanding superbubble of hot gas caused by supernovae and stellar winds or by the active nucleus. The Chandra observations also show four or five possible compact ultra-luminous X-ray (ULX) sources (L(x) >= 10^39 erg/s) associated with NGC 4410A. At least one of these candidate ULXs appears to have a radio counterpart, suggesting that it may be due to an X-ray binary with a stellar-mass black hole, rather than an intermediate mass black hole. In addition, a faint diffuse intragroup X-ray component has been detected between the galaxies (L(x) ~ 10^41 erg/s). This supports the hypothesis that the NGC 4410 group is in the process of evolving via mergers from a spiral-dominated group (which typically have no X-ray-emitting intragroup gas) to an elliptical-dominated group (which often have a substantial intragroup medium).

Space Telescope Imaging Spectrograph Spectroscopy of the Emission‐Line Gas in the Nuclei of Nearby FR‐I Galaxies

We present the results of the analysis of a set of medium-resolution spectra, obtained by the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, of the emission-line gas present in the nuclei of a complete sample of 21 nearby, early-type galaxies with radio jets (the UGC FR-I Sample). For each galaxy nucleus we present spectroscopic data in the region of Hα and the derived kinematics.

Emission‐Line Diagnostics of the Central Engines of Weak‐Line Radio Galaxies

A handful of well-studied Weak-Line Radio Galaxies (WLRGs) have been traditionally classified as Low Ionization Nuclear Emission-line Regions (LINERs), suggesting that these two groups of AGNs might be related. In this paper, we present new optical emission-line measurements for twenty Weak-Line Radio Galaxies which we supplement with measurements for an additional four from the literature. Classifying these objects by their emission-line ratios, we find that 50% of the objects are robustly classified as LINERs while an additional 25% are likely to be LINERs. Photoionization calculations show that the Spectral Energy Distribution of the well-studied WLRG 3C 270 (NGC 4261) is able to produce the observed emission-line ratios, but only if the UV emission seen by the narrow emission-line gas is significantly higher than that observed, implying A_V = 2.5-4.2 magnitudes along our line of sight to the nucleus. From the photoionization calculations, we find that the emission-line gas must have an ionization parameter between 10^-3.5 and 10^-4.0 and a wide range in hydrogen density (10^2-10^6 cm^-3) to reproduce the measured emission-line ratios, similar to the properties inferred for the emission-line gas in LINERs. Thus, we find that properties of the emission-line gas as well as the underlying excitation mechanism are indeed similar in LINERs and WLRGs. By extension, the central engines of accretion-powered LINERs and WLRGs, which do host an accreting black hole, may be qualitatively similar.

The Metallicities of Star‐forming Galaxies at Intermediate Redshifts 0.47 &lt;z&lt; 0.92

Estimates of the [O/H] metallicity of the star-forming gas in a sample of 66 Canada-France Redshift Survey galaxies in the range 0.47 75%) have the [O/H] ~ 8.9 metallicities that are seen locally in galaxies of similar luminosities. However, a minority (<25%) appear to have significantly lower metallicities [O/H] < 8.6, as indicated by high values of the Pagel R23 parameter. The fraction of the sample at these lower [O/H] values would be reduced if the reddening in these objects were lower than the EB-V ~ 0.3 assumed. The high metallicities of the majority of the galaxies suggest that they do not fade to be low-metallicity galaxies today. Only one of the 66 galaxies has an optical emission-line spectrum similar to the few Lyman break galaxies recently observed at z ~ 3, emphasizing the differences from that population. The inferred emission-line gas [O/H] metallicity broadly correlates with luminosity in both the rest B and J bands but with considerable scatter introduced, especially at lower luminosities, by the range in [O/H] observed. The metallicity does not appear to correlate well with galaxy size, Hβ strength, or, with the very limited data available, kinematics. The metallicity does correlate well with the continuum optical and optical to infrared colors in a way that could be explained as a combination of photospheric effects, differing ages of the stellar population, and/or different amounts of reddening. None of these should produce large variations in the M/L ratio. These results support a downsizing picture of galaxy evolution, in which the manifestations of star-forming evolutionary activity appear in progressively more massive galaxies at earlier epochs, rather than a fading dwarf picture in which the luminous active galaxies at high redshift are highly brightened galaxies. The overall change in metallicity of star-forming galaxies over the last half of the age of the universe appears to have been modest, Δ[O/H] = 0.08 ± 0.06. This is consistent with the age-metallicity relation in the Galactic disk and is broadly consistent with models for the chemical evolution of the universe, especially those that consider different environments.

Ultraviolet Structure in the Lensed QSO 0957+561

Imaging and spectra of the lensed QSO pair 0957+561 are presented and discussed. The data are principally those from the Space Telescope Imaging Spectrograph near-UV MAMA and cover rest wavelengths from 850 to 1350 A. The QSOs are both extended over about 1'', with morphology that matches with a small rotation and includes one feature aligned with the VLBI radio jets. This is the first evidence of lensed structure in the host galaxy. The off-nuclear spectra arise from emission-line gas and a young stellar population. The gas has velocity components with radial velocities at least 1000 km s-1 with respect to the QSO broad-line region and may be related to the damped Lyα absorber in the nuclear spectra.

Outflowing material in the $z_{\mathsf{em}}$ = 4.92 BAL QSO SDSS J160501.21-011220.0

We present the analysis of broad absorption lines (BALs) seen in the spectrum of the zem ≃4.92 QSO SDSS J160501.21-011220.0. Our high spectral resolution UVES spectrum shows two well detached absorption line systems at zabs= 4.685 and 4.855. The system at zabs= 4.855 covers the background source completely suggesting that the gas is located outside the broad emission line region. On the contrary the system at zabs= 4.685, which covers only on the continuum source, has a covering factor of the order of 0.9. Physical conditions are investigated in the BAL system at zabs= 4.855 using detailed photoionization models. The observed H i absorption line together with the limits on C ii and Si ii absorptions suggest that 16 < log N(H i) (cm −2 ) < 17 in this system. Comparison with models show that the observed column densities of N v , Si iv and C iv in this system require that nitrogen is underabundant by more than a factor 3 compared to silicon if the ionizing radiation is similar to a typical QSO spectrum. This is contrary to what is usually derived for the emission line gas in QSOs. We show that the relative suppression in the N v column density can be explained for Solar abundance ratios or abundance ratios typical of Starburst abundances if an ionizing spectrum devoid of X-rays is used instead. Thus, if the composition of BAL is like that of the emission line regions it is most likely that the cloud sees a spectrum devoid of X-rays similar to what we observe from this QSO. This is consistent with the fact that none of our models have high Compton optical depth to remove X-rays from the QSO. Similar arguments lead to the conclusion that the system at zabs= 4.685 as well is not Compton thick. Using simple Eddington arguments we show that the mass of the central black hole is ∼ 8 × 10 8 M⊙. This suggests that the accretion onto a seed black hole must have started as early as z = 11.

Highly extinguished emission line outflows in the young radio source PKS 1345+12

We present intermediate resolution, large wavelength coverage spectra for the compact radio source PKS 1345+12 (4C 12.50, z = 0.122) that were taken with the aim of investigating the impact of the nuclear activity on thecircumnuclear interstellar medium (ISM). Our spectra show extended line emission up to ∼20 kpc from the nucleus, consistent with the asymmetric halo of diffuse emission observed in optical and infrared images. At the position of the nucleus we observe complex emission line profiles and Gaussian fits to the [O III] emission lines require three components (narrow, intermediate and broad), the broadest of which has width ∼2000 km s - 1 (FWHM) and is blueshifted by ∼2000 km s - 1 with respect to the halo of the galaxy and HI absorption. We interpret this latter component as material in outflow. We also find evidence for large reddening [0.92 4200 cm - 3 ) for the most kinematically disturbed component. The corresponding total mass of line-emitting gas in the kinematically disturbed components is M g a s < 10 6 M O .. Not all emission line profiles can be reproduced by the same model: [OI]λλ6300, 6363 and [SII]λλ6716, 6731 require separate, unique models. We argue that PKS 1345+12 is a young radio source with nuclear regions that are enshrouded in a dense cocoon of gas and dust. The radio jets are expanding through this cocoon, sweeping material out of the nuclear regions. Emission originates from three kinematically distinct regions, though gradients (e.g. in density, ionization potential, velocity) must exist across the regions responsible for the emission of the intermediate and broad components.

On the Origin of Ly Blobs at High Redshift: Kinematic Evidence of a Hyperwind Galaxy at z = 3.1

We present deep optical spectroscopy of an extended Lyα emission-line blob located in an overdense region at redshift z ≈ 3.1 (blob of Steidel et al.). The origin of such Lyα blobs has been debated for some time; two of the most plausible models are (1) that it comes from a dust-enshrouded, extreme starburst galaxy with a large-scale galactic outflow (superwind/hyperwind) or (2) that it is the cooling radiation of protogalaxies in dark matter halos. Examination of the kinematic properties of the Lyα emission-line gas should allow us to determine its nature. With this motivation, we performed optical spectroscopy on blob 1 using the Subaru Telescope and found that its kinematic properties can be well explained in terms of superwind activity.