Broad Absorption Line QSOs Research Articles

BAL effect in quasars due to source orientation

AbstractWe investigated a scenario where the presence of a broad absorption line (BAL) feature in quasars (QSOs) is contingent upon the line of sight being situated within an outflow cone emanating from the source. We examined the mechanism of dust-driven winds based on the failed radiatively accelerated dusty outflow (FRADO) model proposed by Czerny & Hryniewicz, letting it be responsible for the formation of massive outflow. We calculated the probability of observing the BAL effect from the geometry of outflow which is a function of global parameters of black hole mass (M•), Eddington ratio (αEdd), and metallicity (Z). We then compared the results with prevalence of BAL QSOs in a sample of observational data from SDSS. The consistency of our model with the data supports the interpretation of the BAL phenomenon as a result of source orientation, rather than a transitory stage in AGN evolution.

Dust-driven wind as a model of broad absorption line quasars

Context. We test the scenario according to which the broad absorption line (BAL) phenomenon in quasars (QSOs) is not a temporary stage of their life. In this scenario, the BAL effect acts only if the line of sight is within a spatially limited and collimated massive outflow cone covering only a fraction of the sky from the point of view of the nucleus. Aims. The aim is to understand the theoretical mechanism behind the massive outflow in BAL QSOs, which is important for modelling the impact of quasars on the star formation rate in the host galaxy, and, subsequently, on the galaxy evolution. Methods. We applied the specific theoretical model of dust-driven wind that was developed to explain broad emission lines. The model has considerable predictive power. The 2.5D version of the model called failed radiatively accelerated dusty outflow (FRADO) includes the formation of fast funnel-shaped outflow from the disk for a certain range of black hole masses, Eddington ratios, and metallicities. We now interpret BAL QSO as sources that are viewed along the outflowing stream. We calculated the probabilities of seeing the BAL phenomenon as functions of these global parameters, and we compared these probabilities to those seen in the observational data. We included considerations of the presence or absence of obscuring torus. Results. Comparing our theoretical results with observational data for a sample of QSOs consisting of two sub-populations of BAL and non-BAL QSOs, we found that in the model and in the data, the BAL phenomenon mostly occurs for sources with black hole masses higher than 108 M⊙. The effect increases with accretion rate, and high metallicities are also more likely in QSOs showing BAL features if a torus is taken into account. Conclusions. The consistency of the model with the data supports the interpretation of the BAL phenomenon as the result of the orientation of the source. It also supports the underlying theoretical model, although more consistency checks should be made in the future.

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.

MALS SALT-NOT Survey of MIR-selected Powerful Radio-bright AGN at 0 < z < 3.5

We present results of an optical spectroscopic survey using SALT and the Nordic Optical Telescope to build a Wide-field Infrared Survey Explorer mid-infrared color-based, dust-unbiased sample of powerful radio-bright (>200 mJy at 1.4 GHz) active galactic nuclei (AGN) for the MeerKAT Absorption Line Survey (MALS). Our sample has 250 AGN (median z = 1.8) showing emission lines, 26 with no emission lines, and 27 without optical counterparts. Overall, our sample is fainter (Δi = 0.6 mag) and redder (Δ(g−i) = 0.2 mag) than radio-selected quasars, and representative of fainter quasar population detected in optical surveys. About 20% of the sources are narrow-line AGN (NLAGN)–65% of these, at z < 0.5 are galaxies without strong nuclear emission, and 10% at z > 1.9, have emission line ratios similar to radio galaxies. The farthest NLAGN in our sample is M1513-2524 (z em = 3.132), and the largest radio source (size ∼330 kpc) is M0909-3133 (z em = 0.884). We discuss in detail 110 AGN at 1.9 < z < 3.5. Despite representing the radio loudest quasars (median R = 3685), their Eddington ratios are similar to the Sloan Digital Sky Survey quasars having lower R. We detect four C iv broad-absorption line (BAL) QSOs, all among AGN with least R, and highest black hole masses and Eddington ratios. The BAL detection rate (%) is consistent with that seen in extremely powerful (L 1.4GHz > 1025 W Hz−1) quasars. Using optical light curves, radio polarization, and γ-ray detections, we identify seven high-probability BL Lacertae objects. We also summarize the full MALS footprint to search for H i 21 cm and OH 18 cm lines at z < 2.

Near-infrared spectroscopy of extreme BAL QSOs from the QUBRICS bright quasar survey

ABSTRACT We report on the spectral confirmation of 18 quasi-stellar object (QSO) candidates from the QUasars as BRIght beacons for Cosmology in the Southern hemisphere (QUBRICS) survey, previously observed in the optical band, for which we acquired new spectroscopic data in the near-infrared band with the Folded-port InfraRed Echellette (FIRE) spectrograph at the Magellan Baade telescope. In most cases, further observations were prompted by the peculiar nature of the targets, whose optical spectra displayed unexpected absorption features. All candidates have been confirmed as bona fide QSOs, with average emission redshift z ≃ 2.1. The analysis of the emission and absorption features in the spectra, performed with astrocook and QSFit, reveals that the large majority of these objects are broad absorption line (BAL) QSOs, with almost half of them displaying strong Fe ii absorption (typical of the so-called FeLoBAL QSOs). The detection of such a large fraction of rare objects (which are estimated to account for less than 1 per cent of the general QSO population) is interpreted as an unexpected (yet favourable) consequence of the particular candidate selection procedure adopted within the QUBRICS survey. The measured properties of FeLoBAL QSOs observed so far provide no evidence that they are a manifestation of a particular stage in active galactic nucleus (AGN) evolution. In this paper, we present an explorative analysis of the individual QSOs, to serve as a basis for a further, more detailed investigation.

The Physical Constraints on a New LoBAL QSO at z = 4.82

Abstract Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts, to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered by the Lijiang 2.4 m Telescope, with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirm that it is a LoBAL, with a new redshift determination of 4.82 ± 0.01 based on the Mg ii emission-line. The new Mg ii redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimate a black hole mass of ∼2.3 × 109 M ⊙ and Eddington ratio of ∼1.0 according to the empirical Mg ii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power (&gt;0.9% L Edd) is derived from both emission and absorption lines, indicating that these outflows play a significant role in the feedback process that regulates the growth of its black hole, as well as host galaxy evolution.

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.

A SCUBA-2 survey of FeLoBAL QSOs. Are FeLoBALs in a ‘transition phase’ between ULIRGs and QSOs?

It is thought that a class of broad absorption line (BAL) QSOs, characterised by Fe absorption features in their UV spectra (called `FeLoBALs'), could mark a transition stage between the end of an obscured starburst event and a youthful QSO beginning to shed its dust cocoon, where Fe has been injected into the interstellar medium by the starburst. To test this hypothesis we have undertaken deep SCUBA-2 850 $\mu$m observations of a sample of 17 FeLoBAL QSOs with 0.89 $\leq$ z $\leq$ 2.78 and -23.31 $\leq$ M$_{B}$ $\leq$-28.50 to directly detect an excess in the thermal emission of the dust which would probe enhanced star-formation activity. We find that FeLoBALs are not luminous sources in the submillimetre, none of them are individually detected at 850 $\mu$m, nor as a population through stacking ($F_{s}=1.14\pm0.58$ mJy). Statistical and survival analyses reveal that FeLoBALs have sub-mm properties consistent with BAL and non-BAL QSOs with matched redshifts and magnitudes. An SED fitting analysis shows that the FIR emission is dominated by AGN activity, and a starburst component is required only in 6/17 sources of our sample; moreover the integrated total luminosity of 16/17 sources is L$\geq$10$^{12}$L$_{\odot}$, high enough to classify FeLoBALs as infrared luminous. In conclusion, we do not find any evidence in support of FeLoBAL QSOs being a transition population between a ULIRG and an unobscured QSO; in particular, FeLoBALs are not characterized by a cold starburst which would support this hypothesis.

Multicomponent Analysis of the UV Si IV and C IV Broad Absorption Troughs in BALQSO Spectra: The Examples of J01225 + 1339 and J02287 + 0002

Broad Absorption Line QSOs (BALQSOs) are a subtype of radio-quite QSOs that exhibit complex and unusually broad (FWHM ≥ 2,000 km/s) absorption lines. The existence of these lines in BALQSO spectra raises some questions with respect to the properties, the physical conditions and kinematics of the BAL material as well as the morphology of BAL troughs. In this study, taking into consideration the clumpy structure of the AGN outflow winds, we propose a physical model in order to explain the formation of BAL troughs and we give the mathematical description of this model. We also propose a method for analyzing spectroscopically the BAL profiles in the UV region of the electromagnetic spectrum. This method consists of the criteria we set during the fitting process of BAL troughs. The purpose of these criteria is to enable us to determine the exact number of components needed to simulate accurately the BAL troughs and guarantee the uniqueness of the fit. We give an application of the model and the method for Si IV and C IV resonance lines in the case of two BALQSOs. From the analysis, we conclude that the BAL material is in the form of clouds (density enhancements) that move radially and intercept the line-of-sight to the central continuum source. Using our method, we find the number of absorption components needed to simulate the BAL profiles, which means the number of clouds in the line-of-sight. We calculate the velocity shifts, the FWHM and the optical depths of the absorption components of BALs and we propose an internal structure for these clouds. Finally, we give some correlations between the properties of absorption components of Si IV and C IV.

Variability of QSOs with variable regions in broad absorption troughs from the Sloan Digital Sky Survey

The variability of broad absorption lines is investigated for a sample of 188 broad-absorption-line (BAL) quasars (QSOs) ($z > 1.7$) with at least two-epoch observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), covering a time-scale of about 0.001 -- 3 years in the rest frame. Considering only the longest time-scale between epochs for each QSO, 73 variable regions in the \civ BAL troughs are detected for 43 BAL QSOs. The proportion of BAL QSOs showing variable regions increases with longer time-interval than about 1 year in the rest frame. The velocity width of variable regions is narrow compared to the BAL-trough outflow velocity. For 43 BAL QSOs with variable regions, it is found that there is a medium strong correlation between the variation of the continuum luminosity at 1500 \AA\ and the variation of the spectral index. With respect to the total 188 QSOs, larger proportion of BAL QSOs with variable regions appears bluer during their brighter phases, which implies that the origin of BAL variable regions is related to the central accretion process. For 43 BAL QSOs with variable regions, it is possible that there is a negative medium strong correlation between the absolute variation of the equivalent width and the \mgii-based black hole mass, and a medium strong correlation between the maximum outflow velocity of variable regions and the Eddington ratio. These results imply the connection between the BAL-trough variation and the central accretion process.

ON LOCAL IONIZATION EQUILIBRIUM AND DISK WINDS IN QSOs

We present theoretical C iv λλ1548,1550 absorption line profiles for QSOs calculated assuming the accretion disk wind (ADW) scenario. The results suggest that the multiple absorption troughs seen in many QSOs may be due to the discontinuities in the ion balance of the wind (caused by X-rays), rather than discontinuities in the density/velocity structure. The profiles are calculated from a 2.5-dimensional time-dependent hydrodynamic simulation of a line-driven disk wind for a typical QSO black hole mass, a typical QSO luminosity, and for a standard Shakura–Sunyaev disk. We include the effects of ionizing X-rays originating from within the inner disk radius by assuming that the wind is shielded from the X-rays from a certain viewing angle up to 90° ("edge on"). In the shielded region, we assume constant ionization equilibrium, and thus constant line-force parameters. In the non-shielded region, we assume that both the line-force and the C iv populations are nonexistent. The model can account for P-Cygni absorption troughs (produced at edge on viewing angles), multiple absorption troughs (produced at viewing angles close to the angle that separates the shielded region and the non-shielded region), and for detached absorption troughs (produced at an angle in between the first two absorption line types); that is, the model can account for the general types of broad absorption lines seen in QSOs as a viewing angle effect. The steady nature of ADWs, in turn, may account for the steady nature of the absorption structure observed in multiple-trough broad absorption line QSOs. The model parameters are Mbh = 109 M☉ and Ldisk = 1047 erg s−1.

Radio-loud and radio-quiet BAL quasars: a detailed ultraviolet comparison

Studies of radio-loud (RL) broad absorption line (BAL) quasars indicate that popular orientation-based BAL models fail to account for all observations. Are these results extendable to radio-quiet (RQ) BAL quasars? Comparisons of RL and RQ BAL quasars show that many of their properties are quite similar. Here we extend these analyses to the rest-frame ultraviolet (UV) spectral properties, using a sample of 73 RL and 473 RQ BAL quasars selected from the Sloan Digital Sky Survey (SDSS). Each RQ quasar is individually matched to a RL quasar in both redshift (over the range $1.5 < z < 3.5$) and continuum luminosity. We compare several continuum, emission line, and absorption line properties, as well as physical properties derived from these measurements. Most properties in the samples are statistically identical, though we find slight differences in the velocity structure of the BALs that cause apparent differences in CIV emission line properties. Differences in the velocities may indicate an interaction between the radio jets and the absorbing material. We also find that UV FeII emission is marginally stronger in RL BAL quasars. All of these differences are subtle, so in general we conclude that RL and RQ BAL QSOs are not fundamentally different objects, except in their radio properties. They are therefore likely to be driven by similar physical phenomena, suggesting that results from samples of RL BAL quasars can be extended to their RQ counterparts.

Investigating the radio-loud phase of broad absorption line quasars

Broad absorption lines (BALs) are present in the spectra of ~20% of quasars (QSOs); this indicates fast outflows (up to 0.2c) that intercept the observer's line of sight. These QSOs can be distinguished again into radio-loud (RL) BAL QSOs and radio-quiet (RQ) BAL QSOs. The first are very rare, even four times less common than RQ BAL QSOs. The reason for this is still unclear and leaves open questions about the nature of the BAL-producing outflows and their connection with the radio jet. We explored the spectroscopic characteristics of RL and RQ BAL QSOs with the aim to find a possible explanation for the rarity of RL BAL QSOs. We identified two samples of genuine BAL QSOs from SDSS optical spectra, one RL and one RQ, in a suitable redshift interval (2.5$<z<$3.5) that allowed us to observe the Mg II and H$\beta$ emission lines in the adjacent near-infrared (NIR) band. We collected NIR spectra of the two samples using the Telescopio Nazionale Galileo (TNG, Canary Islands). By using relations known in the literature, we estimated the black-hole mass, the broad-line region radius, and the Eddington ratio of our objects and compared the two samples. We found no statistically significant differences from comparing the distributions of the cited physical quantities. This indicates that they have similar geometries, accretion rates, and central black-hole masses, regardless of whether the radio-emitting jet is present or not. These results show that the central engine of BAL QSOs has the same physical properties with and without a radio jet. The reasons for the rarity of RL BAL QSOs must reside in different environmental or evolutionary variables.

Variability of broad absorption lines in QSO SDSS J022844.09+000217.0 on multiyear time-scales

The variability of the broad absorption lines is investigated for a broad absorption line (BAL) QSO, SDSS J022844.09+000217.0 (z = 2.719), with 18 SDSS/BOSS spectra covering 4128 days in the observed frame. With the ratio of the rms spectrum to the mean spectrum, the relative flux change of the BAL-trough is larger than that of the emission lines and the continuum. Fitting the power-law continuum and the emission line profiles of \civ $\lambda$1549 and \siiv$\lambda$1399, we calculate the equivalent width (EW) for different epochs, as well as the continuum luminosity and the spectral index. It is found that there is a strong correlation between the BAL-trough EW and the spectral index, and a weak negative correlation between the BAL-trough EW and the continuum luminosity. The strong correlation between the BAL-trough EW and the spectral index for this one QSO suggests that dust is intrinsic to outflows. The weak correlation between the BAL variability and the continuum luminosity for this one QSO implies that the BAL-trough variation is not dominated by photoionization.

C iv absorption-line variability in X-ray-bright broad absorption-line quasi-stellar objects

C iv absorption-line variability in X-ray-bright broad absorption-line quasi-stellar objects

Variability in Low Ionization Broad Absorption Line outflows

We present results of our time variability studies of Mg II and Al III absorption lines in a sample of 22 Low Ionization Broad Absorption Line QSOs (LoBAL QSOs) at 0.2 <= zem <= 2.1 using the 2m telescope at IUCAA Girawali Observatory over a time-scale of 10 days to 7.69 years in the QSO's rest frame. Spectra are analysed in conjunction with photometric light curves from Catalina Real-Time Transient Survey. Long time-scale (i.e >= 1 year) absorption line variability is seen in 8 cases (36% systems) while only 4 of them (i.e 18% systems) show variability over short time-scales (i.e < 1 year). We notice a tendency of highly variable LoBAL QSOs to have high ejection velocity, low equivalent width and low redshift. The detection rate of variability in LoBAL QSOs showing Fe fine-structure lines (FeLoBAL QSOs) is less than that seen in non-Fe LoBAL QSOs. Absorption line variability is more frequently detected in QSOs having continuum dominated by Fe emission lines compared to rest of the QSOs. Confirming these trends with a bigger sample will give vital clues for understanding the physical distinction between different BAL QSO sub-classes. We correlate the absorption line variability with various parameters derived from continuum light curves and find no clear correlation between continuum flux and absorption line variabilities. However, sources with large absorption line variability also show large variability in their light curves. We also see appearance/disappearance of absorption components in 2 cases and clear indications for profile variations in 4 cases. The observed variability can be best explained by a combination of process driven by continuum variations and clouds transiting across the line of sight.

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 simple disc wind model for broad absorption line quasars

Approximately 20% of quasi-stellar objects (QSOs) exhibit broad, blue-shifted absorption lines in their ultraviolet spectra. Such features provide clear evidence for significant outflows from these systems, most likely in the form of accretion disk winds. These winds may represent the "quasar" mode of feedback that is often invoked in galaxy formation/evolution models, and they are also key to unification scenarios for active galactic nuclei (AGN) and QSOs. To test these ideas, we construct a simple benchmark model of an equatorial, biconical accretion disk wind in a QSO and use a Monte Carlo ionization/radiative transfer code to calculate the ultraviolet spectra as a function of viewing angle. We find that for plausible outflow parameters, sightlines looking directly into the wind cone do produce broad, blue-shifted absorption features in the transitions typically seen in broad absorption line QSOs. However, our benchmark model is intrinsically X-ray weak in order to prevent overionization of the outflow, and the wind does not yet produce collisionally excited line emission at the level observed in non-BAL QSOs. As a first step towards addressing these shortcomings, we discuss the sensitivity of our results to changes in the assumed X-ray luminosity and mass-loss rate, Mdot(wind). In the context of our adopted geometry, Mdot(wind) ~ Mdot(acc) is required in order to produce significant BAL features. The kinetic luminosity and momentum carried by such outflows would be sufficient to provide significant feedback.

LINE SHIFTS, BROAD-LINE REGION INFLOW, AND THE FEEDING OF ACTIVE GALACTIC NUCLEI

Velocity-resolved reverberation mapping suggests that the broad-line regions (BLRs) of AGNs can have significant net inflow. We use the STOKES radiative transfer code to show that electron and Rayleigh scattering off the BLR and torus naturally explains the blueshifted profiles of high-ionization lines and the ionization dependence of the blueshifts. This result is insensitive to the geometry of the scattering region. If correct, this model resolves the long-standing conflict between the absence of outflow implied by velocity-resolved reverberation mapping and the need for outflow if the blueshifting is the result of obscuration. The accretion rate implied by the inflow is sufficient to power the AGN. We suggest that the BLR is part of the outer accretion disk and that similar MHD processes are operating. In the scattering model the blueshifting is proportional to the accretion rate so high-accretion-rate AGNs will show greater high-ionization line blueshifts as is observed. Scattering can lead to systematically too high black hole mass estimates from the C IV line. We note many similarities between narrow-line region (NLR) and BLR blueshiftings, and suggest that NLR blueshiftings have a similar explanation. Our model explains the higher blueshifts of broad absorption line QSOs if they are more highly inclined. Rayleigh scattering from the BLR and torus could be more important in the UV than electron scattering for predominantly neutral material around AGNs. The importance of Rayleigh scattering versus electron scattering can be assessed by comparing line profiles at different wavelengths arising from the same emission-line region.

Herschel-ATLAS: the far-infrared properties and star formation rates of broad absorption line quasi-stellar objects

We have used data from the Herschel-ATLAS at 250, 350 and 500 \mu m to determine the far-infrared (FIR) properties of 50 Broad Absorption Line Quasars (BAL QSOs). Our sample contains 49 high-ionization BAL QSOs (HiBALs) and 1 low-ionization BAL QSO (LoBAL) which are compared against a sample of 329 non-BAL QSOs. These samples are matched over the redshift range 1.5 \leq z < 2.3 and in absolute i-band magnitude over the range -28 \leq M_{i} \leq -24. Of these, 3 BAL QSOs (HiBALs) and 27 non-BAL QSOs are detected at the > 5 sigma level. We calculate star-formation rates (SFR) for our individually detected HiBAL QSOs and the non-detected LoBAL QSO as well as average SFRs for the BAL and non-BAL QSO samples based on stacking the Herschel data. We find no difference between the HiBAL and non-BAL QSO samples in the FIR, even when separated based on differing BAL QSO classifications. Using Mrk 231 as a template, the weighted mean SFR is estimated to be \approx240\pm21 M_{\odot} yr^{-1} for the full sample, although this figure should be treated as an upper limit if AGN-heated dust makes a contribution to the FIR emission. Despite tentative claims in the literature, we do not find a dependence of {\sc C\,iv} equivalent width on FIR emission, suggesting that the strength of any outflow in these objects is not linked to their FIR output. These results strongly suggest that BAL QSOs (more specifically HiBALs) can be accommodated within a simple AGN unified scheme in which our line-of-sight to the nucleus intersects outflowing material. Models in which HiBALs are caught towards the end of a period of enhanced spheroid and black-hole growth, during which a wind terminates the star-formation activity, are not supported by the observed FIR properties.