Broad Absorption Line Quasar APM Research Articles

A multi-epoch study of the C IV absorption variability in the broad absorption line quasar APM 08279+5255

Broad absorption line (BAL) variability potentially represents a powerful tool to investigate the physical nature and the structure of gas outflows in active galactic nuclei. Most existing BAL variability studies rely on observations taken at a few epochs for samples of tens of BAL QSOs. In this study we present the first “monitoring” of a single object, APM 08279+5255, which has been observed more than 20 times since 2003. All available spectra from the literature have also been analysed, including two high resolution spectra, extending the time interval from 1998 to 2012. A relative stability of the shape of the absorption profile is found. At the same time significant variations of the equivalent width are observed. A correlation of the BAL equivalent width with the QSO luminosity is found for the first time. These results suggest that changes in the ionisation state of the gas are causing opacity changes.

A STUDY OF THE X-RAYED OUTFLOW OF APM 08279+5255 THROUGH PHOTOIONIZATION CODES

We present new results from our study of the X-rayed outflow of the z = 3.91 gravitationally lensed broad absorption line (BAL) quasar APM 08279+5255. These results are based on spectral fits to all the long exposure observations of APM 08279+5255 using a new quasar-outflow model. This model is based on cloudy simulations of a near-relativistic quasar outflow. The main conclusions from our multi-epoch spectral re-analysis of Chandra, XMM-Newton and Suzaku observations of APM 08279+5255 are: 1) In every observation we confirm the presence of two strong features, one at rest-frame energies between 1-4 keV, and the other between 7-18 keV. 2) We confirm that the low-energy absorption (1-4 keV rest-frame) arises from a low-ionization absorber with logNH~23 and the high-energy absorption (7-18 keV rest-frame) arises from highly ionized (3>log xi>4; where xi is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation, we find that the velocities on the outflow could get up to ~0.7c. 3) We confirm a correlation between the maximum outflow velocity and the photon index and find possible trends between the maximum outflow velocity and the X-ray luminosity, and between the total column density and the photon index. We performed calculations of the force multipliers of material illuminated by absorbed power laws and a Mathews-Ferland SED. We found that variations of the X-ray and UV parts of the SEDs and the presence of a moderate absorbing shield will produce important changes in the strength of the radiative driving force. These results support the observed trend found between the outflow velocity and X-ray photon index in APM 08279+5255. If this result is confirmed it will imply that radiation pressure is an important mechanism in producing quasar outflows.

CONFIRMATION OF AND VARIABLE ENERGY INJECTION BY A NEAR-RELATIVISTIC OUTFLOW IN APM 08279+5255

We present results from multi-epoch spectral analysis of XMM-Newton and Chandra observations of the broad absorption line (BAL) quasar APM 08279+5255. Our analysis shows significant X-ray BALs in all epochs with rest-frame energies lying in the range of ~ 6.7-18 keV. The X-ray BALs and 0.2-10 keV continuum show significant variability on timescales as short as 3.3 days (proper time) implying a source size-scale of ~ 10 r_g, where r_g is the gravitational radius. We find a large gradient in the outflow velocity of the X-ray absorbers with projected outflow velocities of up to 0.76 c. The maximum outflow velocity constrains the angle between the wind velocity and our line of sight to be less than ~ 22 degrees. We identify the following components of the outflow: (a) Highly ionized X-ray absorbing material (2.9 < logxi < 3.9) and a column density of log N_H ~ 23 outflowing at velocities of up to 0.76 c. (b) Low-ionization X-ray absorbing gas with log N_H ~ 22.8. We find that flatter spectra appear to result in lower outflow velocities. Based on our spectral analysis of observations of APM 08279+5255 over a period of 1.2 years (proper time) we estimate the mass-outflow rate and efficiency of the outflow to have varied between 16(-8,+12) M_solar yr^-1 and 64(-40,+66) M_solar yr^-1 and 0.18(-0.11,+0.15) to 1.7(-1.2+1.9), respectively. Assuming that the outflow properties of APM 08279+5255 are a common property of most quasars at similar redshifts, our results then imply that quasar winds are massive and energetic enough to influence significantly the formation of the host galaxy, provide significant metal enrichment to the interstellar medium and intergalactic medium, and are a viable mechanism for feedback at redshifts near the peak in the number density of galaxy mergers.

SUZAKUOBSERVATIONS OF NEAR-RELATIVISTIC OUTFLOWS IN THE BAL QUASAR APM 08279+5255

We present results from three Suzaku observations of the z=3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. We detect strong and broad absorption at rest-frame energies of <2 keV (low-energy) and 7-12 keV (high-energy). The detection of these features confirms the results of previous long-exposure (80-90 ks) Chandra and XMM-Newton observations. The low and high-energy absorption is detected in both the back-illuminated (BI) and front-illuminated (FI) Suzaku XIS spectra (with an F-test significance of >99%). We interpret the low-energy absorption as arising from a low-ionization absorber with log NH~23 and the high-energy absorption as due to lines arising from highly ionized (2.75 < log xi < 4.0; where xi is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation we find that the velocities in the outflow range between 0.1c and 0.6c. We constrain the angle between the outflow direction of the X-ray absorber and our line of sight to be <36 degrees. We also detect likely variability of the absorption lines (at the >99.9% and >98% significance levels in the FI and BI spectra, respectively) with a rest-frame time scale of ~1 month. Assuming that the detected high-energy absorption features arise from Fe xxv, we estimate that the fraction of the total bolometric energy injected over the quasar's lifetime into the intergalactic medium in the form of kinetic energy to be >10%.

Physical and kinematical properties of the X-ray absorber in the broad absorption line quasar APM 08279+5255

Context. We have re-analyzed the X-ray spectra of the gravitational lensed high-redshift BAL QSO APM 08279+5255, observed with the XMM−Newton and Chandra observatories. Previous studies (Hasinger et al. 2002, ApJ, 573, L77; Chartas et al. 2002, ApJ, 579, 169) detected unusual, highly-ionized iron absorption features, but differed in their interpretation of these features, regarding the kinematical and ionization structure. Aims. We seek one physical model that can be successfully applied to both observations. Methods. For the first time we have performed detailed photoionization modeling on the X-ray spectrum of APM 08279+5255. Results. The absorbing gas in APM 08279+5255 can be represented by a two-absorbers model with column densities NH(1) ≈ 7 × 10 22 cm −2 , NH(2) ≈ 6 × 10 22 cm −2 , and ionization parameters log ξ(1) ≈ 1. 5a nd logξ(2) ≈ 3, with one of them (the high-ionization component) outflowing at v ≈ 0.18(±0.01)c, carrying large amount of gas out of the system. We find that the Chandra spectrum of APM 08279+5255 requires the same Fe/O ratio overabundance (previously) indicated by the XMM−Newton observation, showing that both absorber components underwent similar chemical evolution and/or have similar origin.

SMA High Angular Resolution Imaging of the Lensed Quasar APM 08279+5255

We present Submillimeter Array observations of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255 which spatially resolve the 1.0 mm (200 μm rest frame) dust continuum emission. At 0.4'' resolution, the emission is separated into two components, a stronger, extended one to the northeast (46 ± 5 mJy) and a weaker, compact one to the southwest (15 ± 2 mJy). We have carried out simulations of the gravitational lensing effect responsible for the two submillimeter components in order to constrain the intrinsic size of the submillimeter continuum emission. Using an elliptical lens potential, the best-fit lensing model yields an intrinsic (projected) diameter of ~80 pc, which is not as compact as the optical/near-infrared (NIR) emission and agrees with previous size estimates of the gas and dust emission in APM 08279+5255. Based on our estimate, we favor a scenario in which the 200 μm (rest frame) emission originates from a warm dust component (Td = 150-220 K) that is mainly heated by the AGN rather than by a starburst. The flux is boosted by a factor of ~90 in our model, consistent with recent estimates for APM 08279+5255.

Highly-excited CO emission in APM 08279+5255 atz = 3.9

We report the detection of the CO 4–3, 6–5, 9–8, 10–9, and 11–10 lines in the Broad Absorption Line quasar APM 08279+5255 at using the IRAM 30 m telescope. We also present IRAM PdBI high spatial resolution observations of the CO 4–3 and 9–8 lines, and of the 1.4 mm dust radiation as well as an improved spectrum of the HCN(5–4) line. Unlike CO in other QSO host galaxies, the CO line SED of APM 08279+5255 rises up to the CO(10–9) transition. The line fluxes in the CO ladder and the dust continuum fluxes are best fit by a two component model, a “cold” component at ~ K with a high density of n(H2) = 1105 cm-3, and a “warm”, ~ K component with a density of 1104 cm-3. We show that IR pumping via the 14 bending mode of HCN is the most likely channel for the HCN excitation. From our models we find, that the CO(1–0) emission is dominated by the dense gas component which implies that the CO conversion factor is higher than usually assumed for high-z galaxies with 5 (K km s-1 pc2)-1. Using brightness temperature arguments, the results from our high-resolution mapping, and lens models from the literature, we argue that the molecular lines and the dust continuum emission arise from a very compact (r ≈ 100-300 pc), highly gravitationally magnified () region surrounding the central AGN. Part of the difference relative to other high-z QSOs may therefore be due to the configuration of the gravitational lens, which gives us a high-magnification zoom right into the central 200-pc radius of APM 08279+5255 where IR pumping plays a significant role for the excitation of the molecular lines.

Resolved nuclear CO(1-0) emission in APM 08279+5255: gravitational lensing by a naked cusp?

The ultraluminous broad absorption line quasar APM 08279+5255 is one of the most luminous systems known. Here, we present an analysis of its nuclear CO(1–0) emission. Its extended distribution suggests that the gravitational lens in this system is highly elliptical, probably a highly inclined disc. The quasar core, however, lies in the vicinity of a naked cusp, indicating that APM 08279+5255 is truly the only odd-image gravitational lens. This source is the second system for which the gravitational lens can be used to study structure on sub-kiloparsec scales in the molecular gas associated with the AGN host galaxy. The observations and lens model require CO distributed on a scale of ∼400 pc. Using this scale, we find that the molecular gas mass makes a significant, and perhaps dominant, contribution to the total mass within a couple of hundred parsecs of the nucleus of APM 08279+5255.

Photometric Monitoring of the Gravitationally Lensed Ultraluminous Broad Absorption Line Quasar APM 08279+5255

ABSTRACTWe report on 1 year of photometric monitoring of the ultraluminous broad absorption line quasar APM 08279+5255. The temporal sampling reveals that this gravitationally lensed system has brightened by ∼0.2 mag in 100 days. Two potential causes present themselves: either the variability is intrinsic to the quasar, or it is the result of microlensing by stars in a foreground system. The data are consistent with both hypotheses, and further monitoring is required before either case can be conclusively confirmed. We demonstrate, however, that gravitational microlensing cannot play a dominant role in explaining the phenomenal properties exhibited by APM 08279+5255. The identification of intrinsic variability, coupled with the simple gravitational lensing configuration, would suggest that APM 08279+5255 is a potential “golden lens” from which the cosmological parameters can be derived and is worthy of a monitoring program at high spatial resolution.

KECK HIRES Spectroscopy of APM 08279+525511The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

ABSTRACTWith an optical R‐band magnitude of 15.2, the recently discovered z = 3.911 broad absorption line quasar APM 08279+5255 is an exceptionally bright high‐redshift source. Its brightness has allowed us to acquire a high signal‐to‐noise ratio (∼80), high‐resolution (∼6 km s−1) spectrum using the HIRES echelle spectrograph on the 10 m Keck I telescope. Given the quality of the data, these observations provide an unprecedented view of associated and intervening absorption systems. Here we announce the availability of this spectrum to the general astronomical community and present a brief analysis of some of its main features.

Detection of CO (4–3), CO (9–8), and Dust Emission in the Broad Absorption Line Quasar APM 08279+5255 at a Redshift of 3.9

With the IRAM interferometer, we detected the lines of CO (4-3) and CO (9-8) from the recently discovered broad absorption line quasar APM 08279+5255. The molecular lines are at a redshift of 3.911, which we take to be the true cosmological redshift of the quasar's host galaxy. This means that the quasar emission lines at z=3.87 are blueshifted by a kinematic component of -2500 km s−1 and, along with the broad absorption lines, are probably emitted in the quasar's wind or jet, moving toward us. The CO line ratios suggest that the molecular gas is at a temperature of ~200 K, at a density of ~4000 cm−3. We also detected the dust emission at 94 and 214 GHz (with emitted wavelengths of 650 and 290 μm). The spectral index of the millimeter/submillimeter continuum is 3.2, indicating that the dust emission is optically thin in this part of the spectrum. The extremely high CO and dust luminosities suggest magnification by gravitational lensing. Using the optical extent and our limit on the size of the CO region, we estimate a magnification of 7-30 for the CO lines and the far-IR continuum and 14-60 for the optical/UV. In this interpretation, the molecular gas and dust are in a nuclear disk of radius 90-270 pc around the quasar. The quasar is 25-100 times stronger than, but otherwise resembles, the nucleus of Mrk 231.

Submillimeter Observations of the Ultraluminous Broad Absorption Line Quasar APM 08279+5255

With an inferred bolometric luminosity of 5?10 -->15 L?, the recently identified z=3.87, broad absorption line quasar APM 08279+5255 is apparently the most luminous object currently known. Since half of its prodigious emission occurs in the infrared, APM 08279+5255 also represents the most extreme example of an ultraluminous infrared galaxy. Here we present new submillimeter observations of this phenomenal object; while indicating that a vast quantity of dust is present, these data prove to be incompatible with the current models of emission and reprocessing mechanisms in ultraluminous systems. The influence of gravitational lensing on these models is considered, and we find that while the emission from the central continuum-emitting region may be significantly enhanced, lensing-induced magnification cannot easily reconcile the models with the observations. We conclude that further modeling, including the effects of any differential magnification, is required to explain the observed emission from APM 08279+5255.