Balnicity Index Research Articles

The Nature of LoBAL QSOs. II. HST/WFC3 Observations Reveal Host Galaxies Dominated by Mergers

Low-ionization broad absorption line QSOs (LoBALs) are suspected to be merging systems in which extreme, active galactic nucleus-driven outflows have been triggered. Whether or not LoBALs are uniquely associated with mergers, however, has yet to be established. To characterize the morphologies of LoBALs, we present the first high-resolution morphological analysis of a volume-limited sample of 22 Sloan Digital Sky Survey (SDSS)-selected LoBALs at 0.5 < z < 0.6 from Hubble Space Telescope Wide Field Camera 3 observations. Host galaxies are resolved in 86% of the systems in F125W, which is sensitive to old stellar populations, while only 18% are detected in F475W, which traces young, unobscured stellar populations. Signs of recent or ongoing tidal interaction are present in 45%–64% of the hosts, including double nuclei, tidal tails, bridges, plumes, shells, and extended debris. Ongoing interaction with a companion is apparent in 27%−41% of the LoBALs, with as much as 1/3 of the sample representing late-stage mergers at projected nuclear separations <10 kpc. Detailed surface brightness modeling indicates that 41% of the hosts are bulge dominated while only 18% are disks. We discuss trends in various properties as a function of merger stage and parametric morphology. Notably, mergers are associated with slower, dustier winds than those seen in undisturbed/unresolved hosts. Our results favor an evolutionary scenario in which quasar-level accretion during various merger stages is associated with the observed outflows in low-z LoBALs. We discuss differences between LoBALs and FeLoBALs and show that selection via the traditional balnicity index would have excluded all but one of the mergers.

The WISSH quasars project

Context.The WISSH quasars project aims at studying the nuclear and host galaxy properties of the most luminous quasars (Lbol &gt; 1047erg s−1, 1.8 &lt; z &lt; 4.6), with special emphasis on the occurrence and physical parameters of winds at different scales.Aims.Nuclear winds are manifested as UV-broad (≥2000 km s−1) absorption lines (BAL) in about 15% of quasars. We aim at studying the incidence and properties of such winds in the WISSH sample to investigate possible differences to active galactic nucleus regimes with lower luminosity.Methods.We collected optical spectra from the Sloan Digital Sky Survey (SDSS) data release 12, and identified those showing absorption troughs in the region between the Si IVand C IVemission lines. We used three different indices for BAL absorption: the classic balnicity index (BI), the absorption index (AI), and the intermediate AI1000.Results.We find a higher observed fraction of C IVBAL quasars in the WISSH sample (24%) than in previous catalogues (10−15%). These WISSH BAL quasars are also characterised by a higher average BI (∼4000 km s−1) and maximum velocity (∼17 000 km s−1). Moreover, for two objects we discovered BAL features bluewards of the Si IVpeak, which can be associated with C IVabsorption with a velocity of 0.15c. We also updated previous studies on the dependence of maximum outflow velocity upon bolometric luminosity, showing that BAL winds have intermediate properties compared to molecular or ionised winds and ultra-fast outflows. Finally, the radio properties of the WISSH BAL quasars as a whole are in line with those of samples at lower luminosities from previous studies.Conclusions.Our results suggest that the higherLbolof the WISSH quasars likely favours the acceleration of BAL outflows and that their most likely driving mechanism is radiation pressure. Furthermore, we estimate that the kinetic power associated with these winds in hyperluminous quasars for the highest column density and fastest winds is sufficient to provide efficient feedback onto the host galaxy.

The origin of radio emission in broad absorption line quasars: Results from the LOFAR Two-metre Sky Survey

We present a study of the low-frequency radio properties of broad absorption line quasars (BALQSOs) from the LOFAR Two-metre Sky-Survey Data Release 1 (LDR1). The value-added LDR1 catalogue contains Pan-STARRS counterparts, which we match with the Sloan Digital Sky Survey (SDSS) DR7 and DR12 quasar catalogues. We find that BALQSOs are twice as likely to be detected at 144 MHz than their non-BAL counterparts, and BALQSOs with low-ionisation species present in their spectra are three times more likely to be detected than those with only high-ionisation species. The BALQSO fraction at 144 MHz is constant with increasing radio luminosity, which is inconsistent with previous results at 1.4 GHz, indicating that observations at the different frequencies may be tracing different sources of radio emission. We cross-match radio sources between the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and LDR1, which provides a bridge via the LDR1 Pan-STARRS counterparts to identify BALQSOs in SDSS. Consequently we expand the sample of BALQSOs detected in FIRST by a factor of three. The LDR1-detected BALQSOs in our sample are almost exclusively radio-quiet (log(R144 MHz) &lt; 2), with radio sizes at 144 MHz typically less than 200 kpc; these radio sizes tend to be larger than those at 1.4 GHz, suggesting more extended radio emission at low frequencies. We find that although the radio detection fraction increases with increasing balnicity index (BI), there is no correlation between BI and either low-frequency radio power or radio-loudness. This suggests that both radio emission and BI may be linked to the same underlying process, but are spatially distinct phenomena.

X-ray-selected broad absorption line quasi-stellar objects

We study a sample of six X-ray selected broad absorption line (BAL) quasi-stellar objects (QSOs) from the XMM-Newton Wide Angle Survey. All six objects are classified as BALQSOs using the classic balnicity index, and together they form the largest sample of X-ray selected BALQSOs. We find evidence for absorption in the X-ray spectra of all six objects. An ionized absorption model applied to an X-ray spectral shape that would be typical for non-BAL QSOs (a power law with energy index alpha=0.98) provides acceptable fits to the X-ray spectra of all six objects. The optical to X-ray spectral indices, alpha_OX, of the X-ray selected BALQSOs, have a mean value of 1.69 +- 0.05, which is similar to that found for X-ray selected and optically selected non-BAL QSOs of similar ultraviolet luminosity. In contrast, optically-selected BALQSOs typically have much larger alpha_OX and so are characterised as being X-ray weak. The results imply that X-ray selection yields intrinsically X-ray bright BALQSOs, but their X-ray spectra are absorbed by a similar degree to that seen in optically-selected BALQSO samples; X-ray absorption appears to be ubiquitous in BALQSOs, but X-ray weakness is not. We argue that BALQSOs sit at one end of a spectrum of X-ray absorption properties in QSOs related to the degree of ultraviolet absorption in C IV 1550.

Discovery of two broad absorption line quasars at redshift about 4.75 using the Lijiang 2.4 m telescope

The ultraviolet broad absorption lines have been seen in the spectra of quasars at high redshift, and are generally considered to be caused by outflows with velocities from thousands kilometers per second to one tenth of the speed of light. They provide crucial implications for the cosmological structures and physical evolutions related to the feedback of active galactic nuclei (AGNs). Recently, through a dedicated program of optically spectroscopic identifications of selected quasar candidates at redshift 5 by using the Lijiang 2.4 m telescope, we discovered two luminous broad absorption line quasars (BALQSOs) at redshift about 4.75. One of them may even have the potentially highest absorption Balnicity Index (BI) ever found to date, which is remarkably characterized by its deep, broad absorption lines and sub-relativistic outflows. Further physical properties, including the metal abundances, variabilities, evolutions of the supermassive black holes (SMBH) and accretion disks associated with the feedback process, can be investigated with multi-wavelength follow-up observations in the future.

A VLBI survey of compact broad absorption line quasars with balnicity index BI &gt; 0

Aims. Outflows manifest as broad absorption lines (BALs) in the quasars spectra. Although outflows are one of the most common astrophysical processes in the Universe, the BAL quasars are rare. Radio emission is another tool that can help to understand the phenomenon of BAL quasars. The aim of this paper is to study their orientation and age by very long baseline interferometry (VLBI) imaging and radio-loudness parameter distribution.

VLBI survey of compact broad absorption line quasars with balnicity index BI = 0

We present high-resolution observations, using both the European VLBI Network (EVN) at 1.7-GHz, and the Very Long Baseline Array (VLBA) at 5 and 8.4-GHz to image radio structures of 14 compact sources classified as broad absorption line (BAL) quasars based on the absorption index (AI). All source but one were resolved, with the majority showing core-jet morphology typical for radio-loud quasars. We discuss in details the most interesting cases. The high radio luminosities and small linear sizes of the observed objects indicate they are strong young AGNs. Nevertheless, the distribution of the radio-loudness parameter, log(Ri), of a larger sample of AI quasars shows that the objects observed by us constitute the most luminous, small subgroup of AI population. Additionally we report that for the radio-loudness parameter, the distribution of AI quasars and those selected by using the traditional balnicity index (BI), BI quasars differ significantly. Strong absorption is connected with the lower log(Ri), and thus probably with larger viewing angles. Since, the AI quasars have on average larger log(Ri), the orientation can cause that we see them less absorbed. However, we suggest that the orientation is not the only parameter that affects the detected absorption. The fact that the strong absorption is associated with the weak radio emission is equally important and worth exploring.

The rest-frame ultraviolet properties of radio-loud broad absorption line quasars

We recently presented radio observations of a large sample of radio-loud broad absorption line (BAL) quasars from the SDSS and FIRST surveys, as well as a well matched sample of unabsorbed quasars, primarily to measure their radio spectral indices and estimate ensemble orientations. Here, we analyze the SDSS spectra of these samples and compare the rest-frame ultraviolet properties of radio-loud BAL and non-BAL quasars. Ultraviolet properties include the continuum shape, emission-line measurements of C IV, Al III, C III], Fe II, and Mg II, and BAL properties including the balnicity index (BI), absorption index (AI), and minimum and maximum outflow velocities. We find that radio-loud BAL quasars have similar ultraviolet properties compared to radio-loud non-BAL sources, though they do appear to have redder continua and stronger Fe II emission, which is consistent with what is found for radio-quiet BAL sources. No correlations exist between outflow properties and orientation (radio spectral index), suggesting that BAL winds along any line of sight are driven by the same mechanisms. There are also few correlations between spectral index and other properties. We conclude that BAL outflows occur along all lines of sight with similar strengths and velocities.

X-ray and optical properties of broad absorption line quasars in the Canada-France-Hawaii Telescope Legacy Survey

We study the X-ray and optical properties of 16 Broad Absorption Line (BAL) quasars detected in about 3 degree square region common to the wide synoptic (W-1) component of the Canada-France-HawaiiTelescope Legacy Survey (CFHTLS) and the XMM Large Scale Structure survey (XMM-LSS). The BAL fraction is found to be 10% in full sample, 7% for the optical colour selected QSOs and as high as 33% if we consider QSOs selected from their IR colours. The X-ray detected non-BAL and BAL quasars have a mean observed X-ray-to-optical spectral slope of -1.47 +/- 0.13 and -1.66 +/- 0.17 respectively. We also find that the BAL QSOs have alpha_ox systematically smaller than what is expected from the relationship between optical luminosity and alpha_ox as derived from our sample. Based on this, we show, as already reported in the literature for quasars with high optical luminosities, our new sample of BAL QSOs have X-ray luminosity a factor of three smaller than what has been found for non-BAL QSOs with similar optical luminosities. Comparison of hardness ratio of the BAL and non-BAL QSOs suggests a possible soft X-ray weakness of BAL QSOs. Combining our sample, of relatively fainter QSOs, with others from the literature we show that larger balnicity index (BI) and maximum velocity (V_max) of the C IV absorption are correlated with steeper X-ray to optical spectral index. We argue that this is most likely a consequence of the existence of a lower envelope in the distribution of BI (or V_max) values versus optical luminosity. Our results thus show that the previously known X-ray weakness of BAL QSOs extends to lower optical luminosities as well.

THE TRANSITION FROM “NORMAL” TO “BROAD ABSORPTION LINE QUASAR” OF TON 34

We report the emergence of a high velocity, broad absorption line outflow in the luminous quasar Ton 34, at z=1.928. The outflow is detected through an ultraviolet CIV broad absorption line, in a spectrum obtained in January 2006 by the Sloan Digital Sky Survey. No absorption trough was present in two different spectra acquired in 1981 at Las Campanas and Palomar observatories, indicating the emergence of the outflow in less than ~8 yr (rest-frame). The absorption line spans a velocity range from ~5,000-26,000 km s-1}, and resembles typical troughs found in Broad Absorption Line quasars (BALQSOs). We measure a balnicity index >600 (tough this value might be an underestimation due to a conservativeplacing of the continuum). The absorption trough is likely saturated, with the absorbing gas covering ~25% of the emitting region. We explore different scenarios for the emergence of this outflow, and find an existing wind moving across our line of sight to the source as the most likely explanation. This indicates that high velocity outflows (producing broad absorption troughs in BALQSOs) might be ubiquitous in quasars, yet only become observable when the wind accidentally crosses our line vision to the central source.

A revision of the X-ray absorption nature of BALQSOs

Broad absorption line quasars (BALQSOs) are key objects for studying the structure and emission/absorption properties of AGN. However, despite their fundamental importance, the properties of BALQSOs are still not well understood. In order to investigate the X-ray nature of these sources, as well as the correlations between X-ray and rest-frame UV properties, we compile a large sample of 88 BALQSOs observed by XMM-Newton. We performed a full X-ray spectral analysis on a sample of 39 sources with higher X-ray spectral quality, and an approximate HR analysis on the remaining sources. Using available optical spectra, we calculate the BALnicity index and investigate the dependence between this optical parameter and different X-ray properties. Using the neutral absorption model, we found that 36% of our BALQSOs have NH < 5x10^21 cm^-2, lower than the expected X-ray absorption for such objects. However, when we used a physically-motivated model for the X-ray absorption in BALQSOs, i.e. ionized absorption, \sim 90% of the objects are absorbed. The absorption properties also suggest that LoBALs may be physically different objects from HiBALs. In addition, we report on a correlation between the ionized absorption column density and BAL parameters. There is evidence (at 98% level) that the amount of X-ray absorption is correlated with the strength of high-ionization UV absorption. This correlation, not previously reported, can be naturally understood in virtually all BALQSO models, as driven by the total amount of gas mass flowing towards the observer.

LOW-zMg II BROAD ABSORPTION-LINE QUASARS FROM THE SLOAN DIGITAL SKY SURVEY

We present a sample of 68 low-z MgII low-ionization broad absorption-line (loBAL) quasars. The sample is uniformly selected from the SDSS5 according to the following criteria: (1) 0.4<z<0.8, (2) median S/N>7, and (3) MgII absorption-line width > 1600 \kms. The last criterion is a trade-off between the completeness and consistency with respect to the canonical definition of BAL quasars that have the `balnicity index' BI>0 in CIV BAL. We adopted such a criterion to ensure that ~90% of our sample are classical BAL quasars and the completeness is ~80%, based on extensive tests using high-z quasar samples with measurements of both CIV and MgII BALs. We found (1) MgII BAL is more frequently detected in quasars with narrower Hbeta emission-line, weaker [OIII] emission-line, stronger optical FeII multiplets and higher luminosity. In term of fundamental physical parameters of a black hole accretion system, loBAL fraction is significantly higher in quasars with a higher Eddington ratio than those with a lower Eddington ratio. The fraction is not dependent on the black hole mass in the range concerned. The overall fraction distribution is broad, suggesting a large range of covering factor of the absorption material. (2) [OIII]-weak loBAL quasars averagely show undetected [NeV] emission line and a very small line ratio of [NeV] to [OIII]. However, the line ratio in non-BAL quasars, which is much larger than that in [OIII]-weak loBAL quasars, is independent of the strength of the [OIII] line. (3) loBAL and non-loBAL quasars have similar colors in near-infrared to optical band but different colors in ultraviolet. (4) Quasars with MgII absorption lines of intermediate width are indistinguishable from the non-loBAL quasars in optical emission line properties but their colors are similar to loBAL quasars, redder than non-BAL quasars. We also discuss the implication of these results.

THE CORRELATION BETWEEN X-RAY AND UV PROPERTIES OF BAL QSOs

We compile a large sample of broad absorption line (BAL) quasars with X-ray observations from the XMM-Newton archive data and Sloan Digital Sky Survey Data Release 5. The sample consists of 41 BAL QSOs. Among 26 BAL quasars detected in X-ray, spectral analysis is possible for 12 objects. X-ray absorption is detected in all of them. Complementary to that of Gallagher et?al., our sample spans wide ranges of both BALnicity index (BI) and maximum outflow velocity (v max). Combining our sample with that of Gallagher et?al., we find very significant correlations between the intrinsic X-ray weakness and both BI and the maximum velocity of the absorption trough. We do not confirm the previously claimed correlation between absorption column density and BAL parameters. Our tentative interpretation is that X-ray absorption is necessary to the production of the BAL outflow, but the properties of the outflow are largely determined by intrinsic spectral energy distribution of the quasars.

Dependence of the Broad Absorption Line Quasar Fraction on Radio Luminosity

We find that the fraction of classical broad absorption line quasars (BALQSOs) among the FIRST radio sources in the Sloan Data Release 3, is -->20.5+ 7.3?5.9% at the faintest radio powers detected ( -->L1.4 GHz ~ 1032 erg s?1), and rapidly drops to 8% at -->L1.4 GHz ~ 3 ? 1033 erg s?1. Similarly, adopting the broader absorption index (AI) definition of Trump et al., we find the fraction of radio BALQSOs to be -->44+ 8.1?7.8%, reducing to -->23.1+ 7.3?6.1% at high luminosities. While the high fraction at low radio power is consistent with the recent near-IR estimates by Dai et al., the lower fraction at high radio powers is intriguing and confirms previous claims based on smaller samples. The trend is independent of the redshift range, the optical and radio flux selection limits, or the exact definition of a radio match. We also find that at fixed optical magnitude, the highest bins of radio luminosity are preferentially populated by non-BALQSOs, consistent with the overall trend. We do find, however, that those quasars identified as AI-BALQSOs but not under the classical definition do not show a significant drop in their fraction as a function of radio power, further supporting independent claims that these sources, characterized by lower equivalent width, may represent an independent class from the classical BALQSOs. We find the balnicity index, a measure of the absorption trough in BALQSOs, and the mean maximum wind velocity to be roughly constant at all radio powers. We discuss several plausible physical models which may explain the observed fast drop in the fraction of the classical BALQSOs with increasing radio power, although none is entirely satisfactory. A strictly evolutionary model for the BALQSO and radio emission phases requires a strong fine-tuning to work, while a simple geometric model, although still not capable of explaining polar BALQSOs and the paucity of FRII BALQSOs, is statistically successful in matching the data if part of the apparent radio luminosity function is due to beamed, non-BALQSOs.

The intrinsic fraction of broad-absorption line quasars

We carefully reconsider the problem of classifying broad-absorption line quasars (BALQSOs) and derive a new, unbiased estimate of the intrinsic BALQSO fraction from the Sloan Digital Sky Survey (SDSS) DR3 quasi-stellar object (QSO) catalogue. We first show that the distribution of objects selected by the so-called 'absorption index' (AI) is clearly bimodal in log AI, with only one mode corresponding to definite BALQSOs. The surprisingly high BALQSO fractions that have recently been inferred from AI-based samples are therefore likely to be overestimated. We then present two new approaches to the classification problem that are designed to be more robust than the AI, but also more complete than the traditional 'balnicity index' (BI). Both approaches yield observed BALQSO fractions around 13.5 per cent, while a conservative third approach suggests an upper limit of 18.3 per cent. Finally, we discuss the selection biases that affect our observed BALQSO fraction. After correcting for these biases, we arrive at our final estimate of the intrinsic BALQSO fraction. This is fBALQSO= 0.17 ± 0.01 (stat) ± 0.03 (sys) with an upper limit of fBALQSO? 0.23 . We conclude by pointing out that the bimodality of the log AI distribution may be evidence that the BAL-forming region has clearly delineated physical boundaries.

Unusual high-redshift radio broad absorption-line quasar 1624+3758

We present observations of the most radio-luminous broad absorption-line (BAL) quasar known, 1624+3758, at redshift z = 3.377. The quasar has several unusual properties. (1) The Fe II UV191 1787-A emission line is very prominent. (2) The BAL trough (BALnicity index 2990 km s −1 )i sdetached by 21 000 km s −1 and extends to velocity v =− 29 000 km s −1 . There are additional intrinsic absorbers at −1900 and −2800 km s −1 . (3) The radio rotation measure of the quasar, 18 350 rad m −2 ,i sthe second highest known. The radio luminosity is P 1.4 GHz = 4.3 × 10 27 WH z −1 (H 0 = 50 km s −1 Mpc −1 , q 0 = 0.5) and the radio loudness is R ∗ = 260. The radio source is compact ( ∼ 2.8 kpc) and the radio spectrum is GHz-peaked, consistent with it being relatively young. The width of the C IV emission line, in conjunction with the total optical luminosity, implies a black hole mass M BH ∼ 10 9 M� , L/L Eddington ≈ 2. The high Eddington ratio and the radio-loudness place this quasar in one corner of Boroson’s two-component scheme for the classification of active galactic nuclei, implying a very high accretion rate, and this may account for some of the unusual observed properties. The v = −1900 km s −1 absorber is a possible Lyman-limit system, with N (H I) = 4 × 10 18 cm −2 , and a covering factor of 0.7. A complex mini-BAL absorber at v =− 2200 to −3400 km s −1 is detected in each of C IV ,N V and O VI. The blue and red components of the C IV doublet happen to be unblended, allowing both the covering factor and optical depth to be determined as a function of velocity. Variation of the covering factor with velocity dominates the form of the mini-BAL, with the absorption being saturated (e −τ ≈ 0) over most of the velocity range. The velocity dependence of the covering factor and the large velocity width imply that the mini-BAL is intrinsic to the quasar. There is some evidence of line-locking between velocity components in the C IV mini-BAL, suggesting that radiation pressure plays a role in accelerating the outflow. Ke yw ords: galaxies: high-redshift ‐ intergalactic medium ‐ quasars: absorption lines ‐ quasars: emission lines ‐ quasars: general ‐ early Universe.

Polarization properties of broad absorption line QSOs: New statistical clues

We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations between ten optical indices and the polarization degree p0 are systematically searched for. We find six significant non-trivial correlations. In order to identify the most important correlations, we perform a principal component analysis with a sample of 30 BAL QSOs and eight quantities (including p0). Most of the variance (∼57%) in the data is contained in two principal components called PC1 and PC2. PC1 is mainly dominated by the correlation between the balnicity index BI and the strength of the Fe  emission; it may be driven by the accretion rate of matter onto the central compact object. The variance in PC2 is essentially due to the anti-correlation between p0 and the detachment index DI, indicating that BAL QSOs with P Cygni profiles (DI� ) are usually more polarized than those objects with C  absorption troughs well detached from the corresponding emission lines (DI� ). We show that PC2 may be related to the orientation of the BAL QSOs with respect to the line of sight. We also present new spectropolarimetric observations of six BAL QSOs. By adding spectropolarimetric data from the literature, we build a sample of 21 BAL QSOs for which we define four spectropolarimetric indices describing the polarization properties of the absorption and emission lines. We find that the polarization of the C ) emission line is systematically higher than the po- larization of the C  emission line, and that the highest polarization in the troughs is correlated to the balnicity index. Another important result emerging from the statistical tests performed on this spectropolarimetric sample is a possible anti-correlation between the detachment index and a quantity SI which measures the ratio of the depths of the C  absorption in the polarized flux and in the total flux. This correlation indicates that in BAL QSOs with P cygni profiles, the BAL troughs in the polarized flux are nearly as deep as in the total flux while, in BAL QSOs with detached absorptions, the BAL troughs in the polarized flux are much weaker than in the total flux. We show that our main results may be explained in the framework of a two-component wind model which is a natural exten- sion of the classical wind-from-disk models. In this model, the broad absorption occurs in a dense equatorial wind emerging from the accretion disk, while scattering and polarization mainly take place in a polar region. The orientation relative to the observer drives the correlations p0 - DI and DI - SI. While most of our observations can be explained within this framework, there are also several indications that other polarization mechanisms, and more particularly resonance scattering, may also be at work.

Broad Absorption Line Quasars in the Early Data Release from the Sloan Digital Sky Survey

A new broad absorption line quasar (BAL) sample is derived from the first data released by the Sloan Digital Sky Survey. With 116 objects, it is the largest BAL sample yet assembled. Over the redshift range 1.8 < z < 3.8, the crude fraction with broad absorption in the CIV line is roughly 15%. This fraction may be subject to small selection-efficiency adjustments. There are also hints of redshift-dependence in the BAL fraction. The sample is large enough to permit the first estimate of the distribution of balnicity index: subject to certain arbitrary parameters in the definition of this quantity, it is very broad, with (roughly) equal numbers of objects per logarithmic interval of balnicity. BAL quasars are also found to be redder on average than non-BAL quasars. The fraction of radio-loud BAL quasars is (weakly) consistent with the fraction of radio-loud ordinary quasars.

ITAL]J[/ITAL]-Band Spectroscopy of the [CLC][ITAL]z[/ITAL][/CLC] = 5.74 Broad Absorption Line Quasar SDSSp J104433.04−012502.2

We use NIRSPEC, a near-IR spectrometer on Keck II, to obtain moderate-resolution (R = 1540) spectroscopy that shows conclusively that the C IV emission line in the z = 5.74 quasar SDSSp J104433.04-012502.2 is accompanied by broad, blueshifted C IV absorption. The line has a "balnicity index" of 900 km s-1 and a rest-frame equivalent width of 13.1 ± 1.3 Å relative to the continuum. This confirms its membership in the class of objects called "broad absorption line" (BAL) quasi-stellar objects (QSOs). SDSSp J1044-0125 was previously suggested to be a BAL QSO based on its UV-to-X-ray flux ratio, which is larger than most non-BAL QSOs. The C IV emission is of normal strength, implying a metallicity similar to that found in other, lower redshift, QSOs.

Comparisons of the emission-line and continuum properties of broad absorption line and normal quasi-stellar objects

The emission-line and continuum properties of a set of 25 broad absorption line QSOs (BALs) and 29 normal QSOs (i.e., non-BALs) are compared. This sample is augmented by an additional 17 BALs. A balnicity index is defined in order to separate the non-BALs from the BALs as objectively as possible, as well as to provide a measure of the strength of the broad absorption line features. It is found that the emission-line properties and the continua of non-BALs and BALs are remarkably similar.