arXiv subjects

Jane C. Charlton

Publications and source records attributed to Jane C. Charlton.

At least 55 records · Page 3Linked to original sources

arXiv2014

Monitoring the Variability of Intrinsic Absorption Lines in Quasar Spectra

We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 years (1-3.5 years in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems nor in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable broad absorption lines. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density $\sim$ 10$^3$-10$^5$ cm$^{-3}$ and upper limits on the distance of the absorbers from the central engine of order a few kpc. Motivated by the observed variability properties, we suggest that mini-BALs can vary because of fluctuations of the ionizing continuum or changes in partial coverage while NALs can vary primarily because of changes in partial coverage.

astro-ph.GA↗

arXiv2014

Some Like It Hot: Linking Diffuse X-ray Luminosity, Baryonic Mass, and Star Formation Rate in Compact Groups of Galaxies

We present an analysis of the diffuse X-ray emission in 19 compact groups of galaxies (CGs) observed with Chandra. The hottest, most X-ray luminous CGs agree well with the galaxy cluster X-ray scaling relations in $L_X-T$ and $L_X-σ$, even in CGs where the hot gas is associated with only the brightest galaxy. Using Spitzer photometry, we compute stellar masses and classify HCGs 19, 22, 40, and 42 and RSCGs 32, 44, and 86 as fossil groups using a new definition for fossil systems that includes a broader range of masses. We find that CGs with total stellar and HI masses $\gtrsim10^{11.3}$ M$_\odot$ are often X-ray luminous, while lower-mass CGs only sometimes exhibit faint, localized X-ray emission. Additionally, we compare the diffuse X-ray luminosity against both the total UV and 24 $μ$m star formation rates of each CG and optical colors of the most massive galaxy in each of the CGs. The most X-ray luminous CGs have the lowest star formation rates, likely because there is no cold gas available for star formation, either because the majority of the baryons in these CGs are in stars or the X-ray halo, or due to gas stripping from the galaxies in CGs with hot halos. Finally, the optical colors that trace recent star formation histories of the most massive group galaxies do not correlate with the X-ray luminosities of the CGs, indicating that perhaps the current state of the X-ray halos is independent of the recent history of stellar mass assembly in the most massive galaxies.

astro-ph.HE↗

arXiv2014

The COS/UVES Absorption Survey of the Magellanic Stream. III: Ionization, Total Mass, and Inflow Rate onto the Milky Way

Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way, creating the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30 degrees of the 21 cm-emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross section of the Magellanic System is ~11 000 square degrees, or around a quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate that the total mass (atomic plus ionized) of the Magellanic System is ~2.0 billion solar masses, with the ionized gas contributing over twice as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its inflow time of ~0.5-1.5 Gyr, it will represent an average inflow rate of ~3.7-6.7 solar masses per year, potentially raising the Galactic star formation rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Stream may not survive its journey to the disk fully intact, and will instead add material to (and cool) the corona.

astro-ph.GA↗

arXiv2013

A Census of Quasar-Intrinsic Absorption in the Hubble Space Telescope Archive: Systems from High Resolution Echelle Spectra

We present a census of z(abs) < 2, intrinsic (those showing partial coverage) and associated [z(abs) ~ z(em)] quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. (2007) survey of 2 < z(em) < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called "strong N V" intrinsic systems (where the equivalent width of H I Ly alpha is small compared to N V 1238) presented in that work, but find no convincing cases of "strong C IV" intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of "strong O VI" systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is a 3-sigma excess in the number of absorbers near the quasar redshift (|Delta v| <= 5000 km/s) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disk of the quasar.

astro-ph.CO↗

arXiv2013

The Optical Green Valley vs Mid-IR Canyon in Compact Groups

Compact groups of galaxies provide conditions similar to those experienced by galaxies in the earlier universe. Recent work on compact groups has led to the discovery of a dearth of mid-infrared transition galaxies (MIRTGs) in IRAC (3.6 - 8.0 micron) color space (Johnson et al. 2007; Walker et al. 2012) as well as at intermediate specific star formation rates (Tzanavaris et al. 2010). However, we find that in compact groups these mid-infrared (mid-IR) transition galaxies in the mid-infrared dearth have already transitioned to the optical ([g-r]) red sequence. We investigate the optical color-magnitude diagram (CMD) of 99 compact groups containing 348 galaxies and compare the optical CMD with mid-IR color space for compact group galaxies. Utilizing redshifts available from SDSS, we identified new galaxy members for 6 groups. By combining optical and mid-IR data, we obtain information on both the dust and the stellar populations in compact group galaxies. We also compare with more isolated galaxies and galaxies in the Coma cluster, which reveals that, similar to clusters, compact groups are dominated by optically red galaxies. While we find that compact group transition galaxies lie on the optical red sequence, LVL+SINGS mid-IR transition galaxies span the range of optical colors. The dearth of mid-IR transition galaxies in compact groups may be due to a lack of moderately star forming low mass galaxies; the relative lack of these galaxies could be due to their relatively small gravitational potential wells. This makes them more susceptible to this dynamic environment, thus causing them to more easily lose gas or be accreted by larger members.

astro-ph.CO↗

arXiv2013

The Milky Way halo as a QSO absorption-line system. New results from an HST/STIS absorption-line catalogue of Galactic high-velocity clouds

We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering fractions of low- and intermediate ions (OI, CII, SiIII, MgII, FeII, SiIII, CIV, and SiIV) in the range fc = 0.20 - 0.70. For detailed analysis we concentrate on SiII absorption components in HVCs, for which we investigate the distribution of column densities, b-values, and radial velocities. Combining information for SiII and MgII, and using a geometrical HVC model we investigate the contribution of HVCs to the absorption cross section of strong MgII absorbers in the local Universe. We estimate that the Galactic HVCs would contribute on average ~52 % to the total strong MgII cross section of the Milky Way, if our Galaxy were to be observed from an exterior vantage point. We further estimate that the mean projected covering fraction of strong MgII absorption in the Milky Way halo and disc from an exterior vantage point is fc(sMgII) = 0.31 for a halo radius of R = 61 kpc. These numbers, together with the observed number density of strong MgII absorbers at low redshift, indicate that the contribution of infalling gas clouds (i.e., HVC analogues) in the halos of Milky Way-type galaxies to the cross section of strong MgII absorbers is <34 %. These findings are in line with the idea that outflowing gas (e.g., produced by galactic winds) in the halos of more actively star-forming galaxies dominate the absorption-cross section of strong MgII absorbers in the local Universe.

astro-ph.CO↗

arXiv2012

Intragroup and Galaxy-Linked Diffuse X-ray Emission in Hickson Compact Groups

Isolated compact groups of galaxies (CGs) present a range of dynamical states, group velocity dispersions, and galaxy morphologies with which to study galaxy evolution, particularly the properties of gas both within the galaxies and in the intragroup medium. As part of a large, multiwavelength examination of CGs, we present an archival study of diffuse X-ray emission in a subset of nine Hickson compact groups observed with the Chandra X-ray Observatory. We find that seven of the groups in our sample exhibit detectable diffuse emission. However, unlike large-scale emission in galaxy clusters, the diffuse features in the majority of the detected groups are linked to the individual galaxies, in the form of both plumes and halos likely as a result of star formation or AGN activity, as well as in emission from tidal features. Unlike previous studies from earlier X-ray missions, HCGs 31, 42, 59, and 92 are found to be consistent with the Lx-T relationship from clusters within the errors, while HCGs 16 and 31 are consistent with the cluster Lx-sigma relation, though this is likely coincidental given that the hot gas in these two systems is largely due to star formation. We find that Lx increases with decreasing group HI to dynamical-mass ratio with tentative evidence for a dependance in X-ray luminosity on HI morphology whereby systems with intragroup HI indicative of strong interactions are considerably more X-ray luminous than passively evolving groups. We also find a gap in the Lx of groups as a function of the total group specific star formation rate. Our findings suggest that the hot gas in these groups is not in hydrostatic equilibrium and these systems are not low-mass analogs of rich groups or clusters, with the possible exception of HCG 62.

astro-ph.CO↗

arXiv2012

Examining the Role of Environment in a Comprehensive Sample of Compact Groups

(Abridged) Compact groups, with their high number densities, small velocity dispersions, and an interstellar medium that has not been fully processed, provide a local analog to conditions of galaxy interactions in the earlier universe. The frequent and prolonged gravitational encounters that occur in compact groups affect the evolution of the constituent galaxies in a myriad of ways, for example gas processing and star formation. Recently, a statistically significant "gap" has been discovered mid-infrared IRAC colorspace of compact group galaxies. This gap is not seen in field samples and is a new example of how the compact group environment may affect the evolution of member galaxies. In order to investigate the origin and nature of this gap, we have compiled a sample of 49 compact groups. We find that a statistically significant deficit of galaxies in this gap region of IRAC colorspace is persistant in this sample, lending support to the hypothesis that the compact group environment inhibits moderate SSFRs. We note a curvature in the colorspace distribution, which is fully consistent with increasing dust temperature as the activity in a galaxy increases. This full sample of 49 compact groups allows us to subdivide the data according to physical properties of the groups. An analysis of these subsamples indicates that neither projected physical diameter nor density show a trend in colorspace within the values represented by this sample. We hypothesize that the apparent lack of a trend is due to the relatively small range of properties in this sample. Thus, the relative influence of stochastic effects becomes dominant. We analyze spectral energy distributions of member galaxies as a function of their location in colorspace and find that galaxies in different regions of MIR colorspace contain dust with varying temperatures and/or PAH emission.

astro-ph.CO↗

arXiv2010

Mid-Infrared Evidence for Accelerated Evolution in Compact Group Galaxies

Compact galaxy groups are at the extremes of the group environment, with high number densities and low velocity dispersions that likely affect member galaxy evolution. To explore the impact of this environment in detail, we examine the distribution in the mid-infrared (MIR) 3.6-8.0 micron colorspace of 42 galaxies from 12 Hickson compact groups in comparison with several control samples, including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are strongly bimodal, with statistically significant evidence for a gap in their distribution. In contrast, none of the other samples show such a marked gap, and only galaxies in the Coma infall region have a distribution that is statistically consistent with the HCGs in this parameter space. To further investigate the cause of the HCG gap, we compare the galaxy morphologies of the HCG and LVL+SINGS galaxies, and also probe the specific star formation rate (SSFR) of the HCG galaxies. While galaxy morphology in HCG galaxies is strongly linked to position with MIR colorspace, the more fundamental property appears to be the SSFR, or star formation rate normalized by stellar mass. We conclude that the unusual MIR color distribution of HCG galaxies is a direct product of their environment, which is most similar to that of the Coma infall region. In both cases, galaxy densities are high, but gas has not been fully processed or stripped. We speculate that the compact group environment fosters accelerated evolution of galaxies from star-forming and neutral gas-rich to quiescent and neutral gas-poor, leaving few members in the MIR gap at any time.

astro-ph.CO↗

arXiv2010

The Physical Conditions of the Intrinsic N V Narrow Absorption Line Systems of Three Quasars

We employ detailed photoionization models to infer the physical conditions of intrinsic narrow absorption line systems found in high resolution spectra of three quasars at z=2.6-3.0. We focus on a family of intrinsic absorbers characterized by N V lines that are strong relative to the Ly-alpha lines. The inferred physical conditions are similar for the three intrinsic N V absorbers, with metallicities greater than 10 times the solar value (assuming a solar abundance pattern), and with high ionization parameters (log U ~ 0). Thus, we conclude that the unusual strength of the N V lines results from a combination of partial coverage, a high ionization state, and high metallicity. We consider whether dilution of the absorption lines by flux from the broad-emission line region can lead us to overestimate the metallicities and we find that this is an unlikely possibility. The high abundances that we infer are not surprising in the context of scenarios in which metal enrichment takes place very early on in massive galaxies. We estimate that the mass outflow rate in the absorbing gas (which is likely to have a filamentary structure) is less than a few solar masses per year under the most optimistic assumptions, although it may be embedded in a much hotter, more massive outflow.

astro-ph.CO↗

arXiv2010

A Bare Molecular Cloud at z~0.45

Several neutral species (MgI, SiI, CaI, FeI) have been detected in a weak MgII absorption line system (W_r(2796)~0.15 Angstroms) at z~0.45 along the sightline toward HE0001-2340. These observations require extreme physical conditions, as noted in D'Odorico (2007). We place further constraints on the properties of this system by running a wide grid of photoionization models, determining that the absorbing cloud that produces the neutral absorption is extremely dense (~100-1000/cm^3), cold (<100 K), and has significant molecular content (~72-94%). Structures of this size and temperature have been detected in Milky Way CO surveys, and have been predicted in hydrodynamic simulations of turbulent gas. In order to explain the observed line profiles in all neutral and singly ionized chemical transitions, the lines must suffer from unresolved saturation and/or the absorber must partially cover the broad emission line region of the background quasar. In addition to this highly unusual cloud, three other ordinary weak MgII clouds (within densities of ~0.005/cm^3 and temperatures of ~10000K) lie within 500 km/s along the same sightline. We suggest that the "bare molecular cloud", which appears to reside outside of a galaxy disk, may have had in situ star formation and may evolve into an ordinary weak MgII absorbing cloud.

astro-ph.CO↗

arXiv2009

The z = 0.0777 C III Absorber Towards PHL 1811 as a Case Study of a Low Redshift Weak Metal Line Absorber

We consider the physical conditions and origin of the z = 0.0777 absorption system observed in C III, C II, Si III, C IV, O VI, and H I absorption along the line of sight towards the quasar PHL 1811. We analysed the HST/STIS and FUSE spectra of this quasar and compared the results to Cloudy photoionization and collisional ionization models in order to derive densities, temperatures, and metallicities of the absorbing gas. The absorption can be explained by two C III clouds, offset by 35 km/s in velocity, with metallicities of ~one-tenth the solar value. One cloud has a density of order n_H = 1.2 +0.9 -0.5 * 10^-3 cm^-3 (thickness 0.4 +0.3 -0.2 kpc) and produces the observed C II and Si III absorption, while the other has a density of order n_H = 1.2 +0.9 -0.5 * 10^-5 cm^-3 (thickness 80 +70 -40 kpc) and gives rise to the observed weak C IV absorption. Cloud temperatures are ~14,000 +3000 -2000 K and ~34,000 -4000 +2000 K for photoionized models. Although collisionally ionized clouds with T ~ 70,000 K are possible, they are less likely because of the short cooling time-scales involved. Previous studies revealed no luminous galaxy at the absorber's redshift, so it is probably related to tidal debris, ejected material, a dwarf galaxy, or other halo material in a galaxy group. Our models also indicate that one of the two clouds would produce detectable weak Mg II absorption if spectral coverage of that transition existed. We predict what the system would look like at z ~ 1 when the ionizing background radiation was more intense. We find that at z ~ 1 the denser component resembles a C IV absorber. The second C III cloud in this z = 0.0777 absorber may be analogous to a subset of the more diffuse O VI absorbers at higher redshift.

astro-ph.CO↗

arXiv2009

Mid-Infrared Evidence for Accelerated Evolution in Compact Group Galaxies

We find evidence for accelerated evolution in compact group galaxies from the distribution in mid-infrared colorspace of 42 galaxies from 12 Hickson Compact Groups (HCGs) compared to the the distributions of several other samples including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are not uniformly distributed in colorspace, as well as quantitative evidence for a gap. Galaxies in the infall region of the Coma cluster also exhibit a non-uniform distribution and a less well defined gap, which may reflect a similarity with the compact group environment. Neither the Coma Center or interacting samples show evidence of a gap, leading us to speculate that the gap is unique to the environment of high galaxy density where gas has not been fully processed or stripped.

astro-ph.CO↗

arXiv2009

The Magellanic Bridge as a DLA System: Physical Properties of Cold Gas toward PKS0312-770

We measure the physical properties of a local multi-component absorption-line system at V_sol ~ 200 km/s toward the quasar PKS0312-770 behind the Magellanic Bridge (MB) using Hubble Space Telescope STIS spectroscopy in conjunction with photoionization modeling. At an impact parameter of ~ 10 kpc from the Small Magellanic Cloud (SMC), this sightline provides a unique opportunity to probe the chemical properties and ionization structure in a nearby absorption line system with a column density of logN(HI) ~ 20.2, at the transition between Damped Lyman Alpha (DLA) and sub-DLA systems. We find that metallicity of -1.0 < logZ < -0.5 and ionization parameter of -6 < logU < -5 for three low-ionization components and logU ~ -2.6 for one high-ionization component. One component at V_sol = 207 km/s shows an alpha-element abundance log(Si/H) ~ -5.0, making it ~ 0.2 dex more metal rich than both SMC H II regions and stars within the MB and the SMC. The N/Si ratio in this component is log(N/Si) = -0.3+/-0.1, making it comparable to other N-poor dwarf galaxies and ~ 0.2 dex lower than H II regions in the SMC. Another component at V_sol = 236 km/s shows a similar Si/H ratio but has log(N/Si) = -1.0+/-0.2, indicating a nitrogen deficiency comparable to that seen in the most N-poor DLA systems. These differences imply different chemical enrichment histories between components along the same sightline. Our results suggest that, if these absorbers are representative some fraction of DLA systems, then 1) DLA systems along single sight-lines do not necessarily represent the global properties of the absorbing cloud, and b) the chemical composition within a given DLA cloud may be inhomogeneous.

astro-ph.CO↗

arXiv2009

A population of weak metal-line absorbers surrounding the Milky Way

We report on the detection of a population of weak metal-line absorbers in the halo or nearby intergalactic environment of the Milky Way. Using high-resolution ultraviolet absorption-line spectra of bright QSOs obtained with the Space Telescope Imaging Spectrograph (STIS), along six sight lines we have observed unsaturated, narrow absorption in OI and SiII together with mildly saturated CII absorption at high radial velocities (|v_LSR|=100-320 km/s). The measured OI column densities are small, implying that these structures represent Lyman-Limit Systems and sub-Lyman-Limit System with HI column densities < 3x10^18 cm^-2, thus below the detection limits of current 21cm all-sky surveys of high-velocity clouds (HVCs). The absorbers apparently are not directly associated with any of the large high-column density HVC complexes, but rather represent isolated, partly neutral gas clumps embedded in a more tenuous, ionized gaseous medium situated in the halo or nearby intergalactic environment of the Galaxy. We speculate that this absorber population represents the local analog of weak MgII systems that are commonly observed in the circumgalactic environment of low- and high-redshift galaxies.

astro-ph.GA↗

arXiv2008

The Chemical and Ionization Conditions in Weak Mg II Absorbers

We present an analysis of the chemical and ionization conditions in a sample of 100 weak Mg II absorbers identified in the VLT/UVES archive of quasar spectra. Using a host of low ionization lines associated with each absorber in this sample, and on the basis of ionization models, we infer that the metallicity in a significant fraction of weak Mg II clouds is constrained to values of solar or higher, if they are sub-Lyman limit systems. Based on the observed constraints, we present a physical picture in which weak Mg II absorbers are predominantly tracing two different astrophysical processes/structures. A significant population of weak Mg II clouds, those in which N(Fe II) is much less than N(Mg II), identified at both low (z ~ 1) and high (z ~ 2) redshift, are potentially tracing gas in the extended halos of galaxies, analogous to the Galactic high velocity clouds. These absorbers might correspond to alpha-enhanced interstellar gas expelled from star-forming galaxies, in correlated supernova events. On the other hand, N(FeII) approximately equal to N(Mg II) clouds, which are prevalent only at lower redshifts (z < 1.5), must be tracing Type Ia enriched gas in small, high metallicity pockets in dwarf galaxies, tidal debris, or other intergalactic structures.

astro-ph↗

arXiv2008

Super-Solar Metallicity in Weak Mg II Absorption Systems at z ~ 1.7

Through photoionization modeling, constraints on the physical conditions of three z ~ 1.7 single-cloud weak Mg II systems (W_r(2796) < 0.3A) are derived. Constraints are provided by high resolution R = 45,000, high signal-to-noise spectra of the three quasars HE0141-3932, HE0429-4091, and HE2243-6031 which we have obtained from the ESO archive of VLT/UVES. Results are as follows: (1) The single-cloud weak Mg II absorption in the three z ~ 1.7 systems is produced by clouds with ionization parameters of -3.8 < logU < -2.0 and sizes of 1-100 pc. (2) In addition to the low-ionization phase Mg II clouds, all systems need an additional 1-3 high-ionization phase C IV clouds within 100 km/s of the Mg II component. The ionization parameters of the C IV phases range from -1.9 < logU < -1.0, with sizes of tens of parsecs to kiloparsecs. (3) Two of the three single-cloud weak Mg II absorbers have near-solar or super-solar metallicities, if we assume a solar abundance pattern. Although such large metallicities have been found for z < 1 weak Mg II absorbers, these are the first high metallicities derived for such systems at higher redshifts. (4) Two of the three weak Mg II systems also need additional low-metallicity, broad Lya absorption lines, offset in velocity from the metal-line absorption, in order to reproduce the full Lya profile. (5) Metallicity in single-cloud weak Mg II systems are more than an order of magnitude larger than those in Damped Lya systems at z ~ 1.7. In fact, there appears to be a gradual decrease in metallicity with increasing N(HI), from these, the most metal-rich Lya forest clouds, to Lyman limit systems, to sub-DLAs, and finally to the DLAs.

astro-ph↗

arXiv2008

Exploratory Study of the X-Ray Properties of Quasars With Intrinsic Narrow Absorption Lines

We have used archival Chandra and XMM-Newton observations of quasars hosting intrinsic narrow UV absorption lines (intrinsic NALs) to carry out an exploratory survey of their X-ray properties. Our sample consists of three intrinsic-NAL quasars and one "mini-BAL" quasar, plus four quasars without intrinsic absorption lines for comparison. These were drawn in a systematic manner from an optical/UV-selected sample. The X-ray properties of intrinsic-NAL quasars are indistinguishable from those of "normal" quasars. We do not find any excess absorption in quasars with intrinsic NALs, with upper limits of a few times 10^22 cm^-2. We compare the X-ray and UV properties of our sample quasars by plotting the equivalent width and blueshift velocity of the intrinsic NALs and the X-ray spectral index against the "optical-to-X-ray" slope, alpha-ox. When BAL quasars and other AGNs with intrinsic NALs are included, the plots suggest that intrinsic-NAL quasars form an extension of the BAL sequences and tend to bridge the gap between BAL and "normal" quasars. Observations of larger samples of intrinsic-NAL quasars are needed to verify these conclusions. We also test two competing scenarios for the location of the NAL gas in an accretion-disk wind. Our results strongly support a location of the NAL gas at high latitudes above the disk, closer to the disk axis than the dense BAL wind. We detect excess X-ray absorption only in Q0014+8118, which does not host intrinsic NALs. The absorbing medium very likely corresponds to an intervening system at z=1.1, which also produces strong absorption lines in the rest-frame UV spectrum of this quasar. In the appendix we discuss the connection between UV and X-ray attenuation and its effect on alpha-ox.

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