Broad Absorption Line Quasars Research Articles

XMM-NewtonSpectroscopy of the Highly Polarized and Luminous Broad Absorption Line Quasar CSO 755

We present the results from XMM-Newton observations of the highly optically polarized broad absorption line quasar (BALQSO) CSO 755. By analyzing its X-ray spectrum with a total of ∼3000 photons, we find that this source has the X-ray continuum of a typical radio-quiet quasar, with a photon index of Γ = 1.83 and a rather flat (X-ray bright) intrinsic optical–X-ray spectral slope of αox = -1.51. The source shows evidence for intrinsic absorption, and fitting the spectrum with a neutral-absorption model gives a column density of NH ∼ 1.2 × 1022 cm-2; this is among the lowest X-ray columns measured for BALQSOs. We do not detect, with high significance, any other absorption features in the X-ray spectrum. We place upper limits on the rest-frame equivalent width of a neutral (ionized) Fe Kα line, ≤180 eV (≤120 eV), and on the Compton-reflection component parameter, R ≤ 0.2, suggesting that most of the X-rays from the source are directly observed rather than being scattered or reflected; this is also supported by the relatively flat intrinsic αox we measure. The possibility that most of the X-ray flux is scattered due to the high level of UV-optical polarization is ruled out. Considering data for 46 BALQSOs from the literature, including CSO 755, we have found that the UV-optical continuum polarization level of BALQSOs is not correlated with any of their X-ray properties. A lack of significant short- and long-term X-ray flux variations in the source may be attributed to a large black hole mass in CSO 755. We note that another luminous BALQSO, PG 2112+059, has both similar shallow C IV BALs and moderate X-ray absorption.

Near infrared imaging of the broad absorption line quasar BAL QSO 0134+3253

In this paper we present near infrared (NIR) imaging data of the host galaxy of the broad absorption line quasar (BALQ) at $z=2.169$, serendipitously found close to 3C 48 (Canalizo et al. 1998, AJ, 115, 890). The data were obtained with the ESO-VLT camera ISAAC during period 67. We find extended, rest-frame optical emission around the BALQ after subtracting a scaled stellar point spread function from the quasar nucleus in J , H , and $K{\rm s}$. The extended rest-frame optical emission can be interpreted as an approximately 2 Gyr old stellar population composing the host galaxy of the BALQ or a stellar population of similar age associated with an intermediate ($z=1.667$) absorption system spectroscopically identified by Canalizo et al. (1998). The rest-frame-UV emission on the other hand is dominated by a young, ~500 Myr old stellar population (Canalizo et al. 1998). The UV/optical colors resemble a mixture of the two populations, of which the young one accounts for about 80%. Assuming that the residual emission is located at the BALQ redshift, we find that the host galaxy has a resolved flux of about 10% of the BALQ flux. The physical scale is quite compact, typical for radio quiet QSOs or Lyman break galaxies at these redshifts, indicating that the systems are still in the process of forming.

Discovery of an Optically Faint Quasar at z = 5.70 and Implications for the Faint Endof the Quasar Luminosity Function

We present observations of an optically faint quasar, RD J114816.2+525339 (hereafter RD J1148+5253), discovered from deep multicolor observations of the field around the z = 6.42 quasar SDSS J1148+5251. The two quasars have a projected separation of 109'' and both are outliers in r - z versus z - J color-color space. Keck spectroscopy reveals RD J1148+5253 to be a broad absorption line quasar at z = 5.70. With zAB = 23.0, RD J1148+5253 is 3.3 mag fainter than SDSS J1148+5251, making it the faintest quasar known at z > 5.5. This object was identified in a survey of ≈2.5 deg2. The implied surface density of quasars at these redshifts and luminosities is broadly consistent with previous extrapolations of the faint end of the quasar luminosity function and supports the idea that active galaxies provide only a minor component of the reionizing ultraviolet flux at these redshifts.

ChandraX-Ray Observations of Radio-Loud Broad Absorption Line Quasars

We report the results of a Chandra X-Ray Observatory survey of five formally radio-loud broad absorption line (BAL) quasars. These five objects include BAL quasars with a range of properties, including both high- and low-ionization BALs. All five BAL quasars are detected in 5 ks ACIS-S exposures, with counts ranging from 12 to 55. The X-ray count rates are down by factors of 40 or more compared to expectations based on the spectral energy distributions of normal, unabsorbed radio-loud quasars; this is the same sort of behavior seen in radio-quiet BAL quasars. Interestingly, the hardness ratios are rather soft and inconsistent with absorption from a neutral hydrogen column density large enough to suppress the X-rays as observed. We conclude that in many cases the X-rays emanating from BAL quasars must be reflected, scattered, or leaked through an ionized absorber or a neutral absorber that does not completely cover the X-ray source (covering ≥98%), or that we are seeing an unabsorbed X-ray source perhaps associated with a radio jet. Much higher counts are required to distinguish among these possibilities. We note several suggestive correlations involving X-ray properties that require verification using larger samples. One source, FIRST J1556+3517, appears to be the X-ray brightest low-ionization BAL quasar known, other than the special case of the nearby Mrk 231. The very faint X-ray emission from FIRST J1044+3656 is consistent with significant obscuration, which strongly favors the multiphase X-ray shielding models of this object in the literature.

Variation in the Scattering Shroud Surrounding Markarian 231

We present a detailed study of the nuclear structure of the highly polarized broad absorption line quasar, Mrk 231, through a multiwavelength campaign of Chandra observations, optical spectroscopy, optical spectropolarimetry, and imaging polarimetry. This campaign was designed to extend the 40 ks Chandra study of Gallagher and coworkers and the optical and UV spectropolarimetric study of Smith and coworkers to probe variability on multiple timescales. As direct emission from the nucleus is heavily obscured at optical through X-ray wavelengths, the detailed study of scattered emission has lead to insights into the stratified and complex central region of this active galaxy. Although significant continuum variability is not detected in any of the three new 40 ks Chandra observations, we investigate Fe K? emission features in the individual and combined spectra. Comparing echelle spectra of the Na I D absorption lines with the literature, we show that one system disappeared in 2000 only to reappear in later epochs. Notably, we detect a large decrease in polarization across the entire optical spectrum of Mrk 231 from 1995 to 2003. Although the polarization fraction fell, e.g., from 4% to 3% at ?obs ~ 6000 ?, the polarization position angle spectrum remained unchanged. The optical polarization behavior is consistent with a decrease in the flux scattered by circumnuclear material on spatial scales where the broad-line region is resolved by the scattering material. Ultraviolet imaging polarimetry of Mrk 231 by the Hubble Space Telescope sets an upper limit on the distance between the active nucleus and the scattering regions of <20 pc.

XMM-Newton spectroscopy of high-redshift quasars

XMM‐Newton observations of 29 high-redshift (z > 2) quasars, including seven radio-quiet, 16 radio-loud and six broad absorption line (BAL) objects, are presented; due to the high redshifts, the rest-frame energy bands extend up to ∼30‐70 keV. Over 2‐10 keV, the quasars can be well fitted in each case by a simple power law, with no strong evidence for iron emission lines. The lack of iron lines is in agreement both with dilution by the radio jet emission (for the radio-loud quasars) and the X-ray Baldwin effect. No Compton reflection humps at higher energies (i.e. above 10 keV in the rest frame) are detected either. Over the broad-band (0.3‐ 10 keV), approximately half (nine out of 16) of the radio-loud quasars are intrinsically absorbed, with the values of NH generally being 1 × 10 22 to 2 × 10 22 cm −2 in the rest frames of the objects. None of the seven radio-quiet objects shows excess absorption, while four of the six BAL quasars are absorbed. The radio-loud quasars have flatter continuum slopes than their radio-quiet counterparts (� RL ∼ 1.55; � RQ ∼ 1.98 over 2‐10 keV), while, after modelling the absorption, the underlying photon index for the six BAL quasars is formally consistent with the non-BAL radio-quiet objects. Ke yw ords: galaxies: active ‐ quasars: general ‐ X-rays: galaxies.

Rest-frame optical and far-infrared observations of extremely bright Lyman-break galaxy candidates atz∼ 2.5

We have investigated the rest-frame optical and far-infrar ed properties of a sample of extremely bright candidate Lyman-break galaxies (LBG) identified in the Sloan Digital Sky Survey. Their high ultraviolet luminosities and lack of str ong ultraviolet emission lines are suggestive of massive starbursts, although it is possible t hat they are more typical luminosity LBGs which have been highly magnified by strong gravitationa l lensing. Alternatively, they may be an unusual class of weak-lined quasars. If the ultraviolet and submillimetre properties of these objects mirror those of less luminous, starbur st LBGs, then they should have detectable rest-frame far-infrared emission. However, our submm photometry fails to detect such emission, indicating that these systems are not merely scaled-up (either intrinsically or as a result of lensing) examples of typical LBGs. In addition we have searched for the morphological signatures of strong lensing, using high-resol ution, near-infrared imaging, but we find none. Instead, near-infrared spectroscopy reveals tha t these systems are, in fact, a rare class of broad absorption-line (BAL) quasars.

The Sloan Digital Sky Survey Quasar Catalog. III. Third Data Release

We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than Mi = -22 (in a cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7), have at least one emission line with FWHM larger than 1000 km s-1 or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is ≈4188 deg2. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than 4, of which 17 are at redshifts greater than 5. For each object the catalog presents positions accurate to better than 02 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800–9200 A at a spectral resolution of 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.

Fine structure effective collision strengths for the electron impact excitation of Al III

Context. $\ion{S}{v}$ emission lines have been observed in solar flares, solar upper atmospheres, quiet sun regions and broad band absorption line quasars, with particular lines being used as diagnostics for electron temperature and density. Accurate atomic data are needed to analyse the observational data and to date the best available calculations for this ion have not included contributions from resonances. Aims. To calculate fine structure effective collision strengths for the electron impact excitation of $\ion{S}{v}$ using a method which incorporates resonances. Methods. A 14-state R -matrix calculation has been performed. The target states are represented by configuration interaction wavefunctions and consist of the 14 lowest LS states, having configurations (2p 6 )3s 2 , 3s3p, 3p 2 , 3s3d, 3s4s, 3p3d. These target states give rise to 26 fine structure levels and 325 possible transitions. The fine structure collision strengths were obtained by transforming to a jj -coupling scheme using the JAJOM program of Saraph and have been determined at a sufficiently fine energy mesh to delineate properly the resonance structure. The effective collision strengths were calculated by averaging the electron collision strengths over a Maxwellian distribution of velocities. Results. Tabulations of the non-zero effective collision strengths for transitions between both the LS states and the fine structure levels are given for electron temperatures ( T e ) in the range $\log_{10} T_{\rm e} ({\rm K}) = 4.0{-}6.0$. Comparisons are made with previous R -matrix and distorted-wave calculations.

Diagnostics of Quasar Broad Absorption Line Geometry: X-Ray Observations and Two-dimensional Optical Spectroscopy

A new generation of sensitive X-ray measurements are indicating that the existence of X-ray attenuation column densities, NH > 1024 cm-2, is quite common among broad absorption line quasars (BALQSOs). This is significant to the geometry of the broad absorption line (BAL) outflow. In particular, such an X-ray shield also shields equatorial accretion disk winds from the UV, thereby preventing high-velocity equatorial outflows from being launched. By contrast, bipolar winds initiated by continuum radiation pressure from the funnel of a slim accretion disk flare outward (like a trumpet) and offer vastly different absorbing columns to the X-ray and UV emission that are emitted from distinct regions of the disk, ~6M and ~10M-40M, respectively (where M is the radius of the black hole). Recent numerical work indicates that it is also possible to launch bipolar outflows from the inner regions of a thin disk. The recent discovery with VLBI that the Galactic analog of a BALQSO, the X-ray binary Circinus X-1 (with high-velocity P Cygni X-ray absorption lines), is viewed virtually along the radio jet axis (and therefore along the spin axis of the black hole and the normal to the accretion disk) has rekindled interest in the bipolar models of BALQSOs. We explore this possibility by studying the nearest BALQSO, Mrk 231. High-resolution two-dimensional optical spectroscopy and VLBI mappings of the radio jet axis indicate that the BAL outflow is parallel to the parsec-scale radio jet.

Near‐Infrared Spectroscopy of High‐Redshift Active Galactic Nuclei. I. A Metallicity–Accretion Rate Relationship

We present new near infrared spectroscopic measurements of the H_beta region for a sample of 29 luminous high redshift quasars. We have measured the width of H_beta in those sources, and added archival H_beta width measurements, to create a sample of 92 active galactic nuclei (AGNs) for which H_beta width and rest-frame UV measurements of N V \lambda 1240 and C IV \lambda 1549 emission-lines are available. Our sample spans six orders of magnitude in luminosity and includes 31 radio-loud AGNs. It also includes 10 narrow-line Seyfert 1 galaxies and one broad absorption-line quasar. We find that metallicity, indicated by the N V/C IV line ratio, is primarily correlated with accretion rate, which is a function of luminosity and H_beta line-width. This may imply an intimate relation between starburst, responsible for the metal enrichment of the nuclear gas, and AGN fueling, represented by the accretion rate. The correlation of metallicity with luminosity, or black hole (BH) mass, is weaker in contrast with recent results which were based on measurements of the width of C IV. We argue that using C IV as a proxy to H_beta in estimating M_BH might be problematic and lead to spurious BH mass and accretion rate estimates in individual sources. We discuss the potential implications of our new result in the framework of the starburst-AGN connection and theories of BH growth.

Extreme gas properties in the most distant quasars

We present near-IR, low resolution spectra of eight of the most distant quasars known, with redshifts in the range 4.9<z<6.4. Half of these quasars are characterized by deep, broad and blueshifted absorption features associated with both high and low ionization species (CIV, SiIV, AlIII, MgII), i.e. they belong to the class of Broad Absorption Line (BAL) quasars, which are associated with powerful outflows of dense gas. Although the sample is small, the large fraction of BAL quasars, the depth and ionization state of the absorption features suggest that these most distant quasars are surrounded by a much larger amount of dense gas than lower redshift (z<4) quasars. The possible interpretation in terms of extremely high accretion rates and the association with the early formation of quasars and of their host galaxies is discussed. The absorption properties of the dust, associated with the gas along the line of sight, appear different with respect to lower redshift quasars, possibly indicating different dust physics at these highest redshifts.

HS 1216+5032: a physical quasar pair with one radio-loud broad absorption line quasar

We report on new multiwavelength observations of HS 1216+5032, a pair of quasi-stellar objects (QSOs) at z = 1.45 separated by 9.1 arcsec, which has been a perennial candidate for a massive dark lens. We explore high signal-to-noise ratio optical spectra from the MMT of both components, which show that aside from the effects of absorption, the emission-line profiles are quite similar. Near-infrared spectra from the United Kingdom Infrared Telescope show identical velocities in Ha emission, but a significant difference in the strength of the narrow component, which is difficult to explain in a lens scenario. We highlight that, based on data from the Very Large Array Faint Images of the Radio Sky survey, HS 1216+5032B is a radio-loud broad absorption line QSO, which certifies HS 1216+5032 as a physical quasar pair. Intriguingly, both quasars show spectroscopic evidence for high accretion rates and large Eddington ratios L/L Edd , supporting the hypothesis that close galaxy interactions trigger nuclear activity.

Dramatic X‐Ray Spectral Variability of the Broad Absorption Line Quasar PG 2112+059

With a 1999 ASCA observation, PG 2112+059 became notable as the first broad absorption line (BAL) quasar found to exhibit a typical radio-quiet quasar X-ray continuum underlying a large amount of intrinsic absorption. We present a recent Chandra ACIS-S3 observation of PG 2112+059 that demonstrates remarkable spectral and luminosity variability since that time. In addition to a decrease in the continuum normalization by a factor of ~3.5, the absorption column density has apparently increased substantially, and a strong feature in the Fe Kα region has appeared. Concurrent Hubble Space Telescope (HST) STIS data compared with archival HST data from earlier epochs show evidence for variability of the continuum (up to a factor of ~1.7 in the ultraviolet), and in some absorption features of the C IV λ1549 BAL since 1992; however, the O VI BAL structure is consistent with a 1995 observation. We also present evidence for Lyβ-O VI λ1037.62 and Lyα-N V λ1242.80 line-locked absorption systems, supporting the assumption that ultraviolet line pressure is driving the BAL outflow. Whereas ultraviolet BALs typically exhibit only modest equivalent width variability over timescales of years, the dramatic X-ray variability of PG 2112+059 suggests that X-ray spectral variability studies of BAL quasars have great potential for probing the physics of quasar winds.

Feedback of kinetic energy into the IGM by supermassive black holes

Our recent Chandra and XMM-Newton observations of two high redshift broad absorption line (BAL) quasars have revealed the presence of massive outflows of highly ionized, high-metallicity material driven from near the black hole (a few gravitational radii) with velocities of up to 0.4c. The inferred mass outflow rates of 1–10 yr−1 and the measured outflow velocities, that significantly exceed the escape velocities of galaxies and clusters of galaxies, imply that quasar winds provide an important feedback mechanism for kinetic energy injection into the IGM. These quasar outflows may also play an important role in the coevolution of black holes and their host galaxies. We present new constraints on the location of the X-ray BAL material based on our analysis of the variability of the ionization properties of the X-ray absorbers. The location and ionization properties of the X-ray BAL material are crucial in inferring the mass outflow rate and rate of kinetic energy injected into the IGM.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Probing broad absorption line quasar outflows: X-ray insights

Energetic outflows appear to occur in conjunction with active mass accretion onto supermassive black holes. These outflows are most readily observed in the ∼10% of quasars with broad absorption lines, where the observer’s line of sight passes through the wind. Until fairly recently, the paucity of X-ray data from these objects was notable, but now sensitive hard-band missions such as Chandra and XMM-Newton are routinely detecting broad absorption line quasars. The X-ray regime offers qualitatively new information for the understanding of these objects, and these new results must be taken into account in theoretical modeling of quasar winds.

The Enrichment of Galaxies by Quasar Outflows

Our recent Chandra and XMM-Newton observations of the gravitationally lensed broad absorption line quasars (BALQSOs) APM 08279+5255 and PG 1115+080 have provided new insights into the structure of quasar outflows and the enrichment of their host galaxies by quasar winds (Chartas et al. 2002, 2003). Our spectral analysis of these observations suggests the presence of X-ray BAL material accelerated to relativistic velocities of up to ~ 0.4c, considerably larger than the observed velocities of the UV BAL absorbers in these objects. We present constraints on the quasar mass-outflow rates based on the observed relativistic outflow velocities and locations of the X-ray BAL material.

Bright Lyman Break Galaxy Candidates in the Sloan Digital Sky Survey First Data Release

We report the discovery of six compact starburst galaxy candidates with redshifts 2.3 < z < 2.8 and r-band magnitudes 19.8-20.5 in the Quasar Catalog of the Sloan Digital Sky Survey (SDSS) First Data Release. The SDSS spectra resemble the composite spectrum of Lyman break galaxies (LBGs) at z ? 3 (albeit with some differences and broader spectral lines), but the objects are 4-5 mag brighter than an L* LBG. These objects could be extremely luminous LBGs, normal LBGs amplified by gravitational lensing, or a rare class of broad absorption line (BAL) quasars. In the first case, star formation rates inferred from the UV continuum luminosities, with no correction for dust extinction, are ~300-1000 M? yr-1, similar to those of ultraluminous infrared galaxies, but in these UV-bright objects the star formation is evidently not obscured by high dust column densities. The SDSS images show no evidence of multiple imaging or foreground lensing structures. The spectra have fairly broad absorption features and prominent high-ionization absorption but do not show high-ionization emission lines and do not resemble known BAL quasars. A rough estimate of the luminosity function of the objects is above a Schechter function extrapolation from LBGs at fainter magnitudes. Improved optical spectra and observations at X-ray, IR, and submillimeter wavelengths could help determine the nature of these remarkable objects.

XMM‐NewtonObservation of Fe Kα Emission from a Broad Absorption Line Quasar: Markarian 231

We present results from a 20 ks XMM-Newton observation of Mrk 231. The European Photon Imaging Camera (EPIC) spectral data reveal strong line emission due to Fe Kα, which has rarely been detected in this class, as broad absorption line quasars (BAL QSOs) are very faint in the X-ray band. The line energy is consistent with an origin in neutral Fe. The width of the line is equivalent to a velocity dispersion ~18,000 km s-1, and thus the line may be attributed to transmission and/or reflection from a distribution of emitting clouds. If, instead, the line originates in the accretion disk, then the line strength and flat X-ray continuum support some contribution from a reflected component, although the data disfavor a model in which the hard X-ray band is purely reflected X-rays from a disk. The line parameters are similar to those obtained for the Fe Kα line detected in another BAL QSO, H1413+117.

XMM‐NewtonReveals the Quasar Outflow in PG 1115+080

We report on an observation of the Broad Absorption Line (BAL) quasar PG 1115+080 performed with the XMM-Newton observatory. Spectral analysis reveals the second case of a relativistic X-ray absorbing outflow in a BAL quasar. The first case was revealed in a recent observation of APM 08279+5255 with the Chandra X-ray Observatory. The spectrum of PG1115+080 indicates the presence of complex low-energy absorption in the 0.2-0.6 keV observed energy band and high-energy absorption in the 2-5 keV observed energy band. The high-energy absorption is best modeled by two Gaussian absorption lines with rest-frame energies of 7.4 keV and 9.5 keV. Assuming that these two lines are produced by resonant absorption due to Fe xxv Kalpha, we infer that the X-ray absorbers are outflowing with velocities of ~0.10c and ~0.34c, respectively. We have detected significant variability of the energies and widths of the X-ray BALs in PG 1115+080 and APM 08279+5255 over timescales of 19 and 1.8 weeks (proper-time), respectively. The BAL variability observed from APM 08279+5255 supports our earlier conclusion that these absorbers are most likely launched at relatively small radii of ~ 10^(16)(M_BH/M_8)^(1/2)cm. A comparison of the ionization properties and column densities of the low-energy and high-energy absorbers indicates that these absorbers are likely distinct; however, higher spectral resolution is needed to confirm this result. Finally, we comment on prospects for constraining the kinematic and ionization properties of these X-ray BALs with the next generation of X-ray observatories.