Blueshifted Broad Absorption Line Research Articles

Discovery of a damped Ly α absorber in the circumnuclear zone of the FeLoBAL quasar SDSS J083942.11+380526.3

ABSTRACT SDSS J083942.11+380526.3 ($z=2.315$) is an iron low-ionization broad absorption lines quasar that exhibits visible Balmer absorption lines (H $\alpha$), implying a significant $n=2$ population. The quasar also shows an array of absorption lines, including O i, Ni ii, Fe ii, Mg ii, Al iii to C iv, and N v. The high-ionization absorption lines such as C iv and Si iv are revealed by slightly blueshifted broad absorption lines troughs. The resonance doublets such as Mg ii and Al iii are saturated but did not reached zero intensity which indicates that the broad-line region (BLR) is partially covered. Overall, however, the absorption is predominantly from low-ionization Fe ii lines, emitted from ground and excited states up to at least 3.814 eV. This implies that the absorbing gas spans the hydrogen ionization front and extends into the partially ionized zone where neutral hydrogen is certainly present. Notably, the hydrogen line spectrum of the quasar shows no signature of expected Ly $\alpha$ absorption. Instead, the line spectrum shows an unusual Ly $\alpha$ emission characterized by a fully filled emission line spectrum which is a composite of a strong narrow core superposed on a weak broad base. Taking into account the effect of partial covering to BLR, we have extracted a strong Damped Ly α systems (DLA) trough in Ly $\alpha$ emission region. To fit the spectrum, we performed photoionized model calculations and compared them to the observations. We found that photoionization modelling using cloudy can successfully reproduce the main characteristics of the quasar spectrum, and the predicted neutral hydrogen column density arising from the clouds responsible for the low-ionization absorption provides a good match to the extracted DLA trough. This indicates that both the DLA and the low-ionization absorption arise from the same medium that is roughly collocated with the dusty torus.

Efficient identification of broad absorption line quasars using dimensionality reduction and machine learning

Efficient identification of broad absorption line quasars using dimensionality reduction and machine learning

AGN outflows and its variability

AbstractThe radiative mode of AGN feedback, operated through outflows, plays an essential role in the evolution of galaxies. Quasar outflows are detected as blue-shifted broad absorption lines in the UV/optical spectra of quasars. Thanks to the Sloan digital sky survey, 100,000 broad absorption line quasars are available now for ensemble statistical studies. This rich dataset has also enabled us to identify some peculiar cases of these sources. By quantifying the BAL fraction in radio-loud BAL quasars, our studies demonstrate a clear trend of increasing BAL fraction as the viewing angle approaches an edge-on orientation, favoring the orientation model of BAL quasars. Also, by contrasting the properties of BAL quasars with appearing and disappearing BAL troughs, our analysis suggests that the extreme variations in BAL troughs are driven by ionization changes.

Highly Structured Quasar Outflow in SDSS J010612.22+001920.1

Abstract Evidence for quasar outflows can be detected via blueshifted broad absorption lines (BALs) in rest-frame ultraviolet spectra of quasars. We have identified 18 narrow absorption line (NAL) systems in the BAL system of SDSS J010612.22+001920.1, indicating that this BAL outflow has achieved a high degree of clumpiness. Moreover, these NAL systems are highly structured in velocity space and separated from each other by the doublet spacings of multiple ionic species, including a sequence of 10 C iv doublets that form arithmetic progression with a common difference of ≈498 . Cases like J010612.22+001920.1 offer strong evidence for the dynamical process of radiative acceleration in quasar outflow, and open up a new way for the research of quasar outflow under the framework of the NAL complex.

Accretion disc winds in tidal disruption events: ultraviolet spectral lines as orientation indicators

ABSTRACT Some tidal disruption events (TDEs) exhibit blueshifted broad absorption lines (BALs) in their rest-frame ultraviolet (UV) spectra, while others display broad emission lines (BELs). Similar phenomenology is observed in quasars and accreting white dwarfs, where it can be interpreted as an orientation effect associated with line formation in an accretion disc wind. We propose and explore a similar unification scheme for TDEs. We present synthetic UV spectra for disc and wind-hosting TDEs, produced by a state-of-the-art Monte Carlo ionization and radiative transfer code. Our models cover a wide range of disc wind geometries and kinematics. Such winds naturally reproduce both BALs and BELs. In general, sightlines looking into the wind cone preferentially produce BALs, while other orientations preferentially produce BELs. We also study the effect of wind clumping and CNO-processed abundances on the observed spectra. Clumpy winds tend to produce stronger UV emission and absorption lines, because clumping increases both the emission measure and the abundances of the relevant ionic species, the latter by reducing the ionization state of the outflow. The main effect of adopting CNO-processed abundances is a weakening of C iv 1550 Å and an enhancement of N v 1240 Å in the spectra. We conclude that line formation in an accretion disc wind is a promising mechanism for explaining the diverse UV spectra of TDEs. If this is correct, the relative number of BAL and BEL TDEs can be used to estimate the covering factor of the outflow. The models in this work are publicly available online and upon request.

Outflows & Feedback from Extremely Red Quasars

AbstractFeedback from accreting supermassive black holes is often invoked in galaxy evolution models to inhibit star formation, truncate galaxy growth, and establish the observed black-hole/bulge mass correlation. We are studying outflows and feedback in a unique sample of extremely red quasars (ERQs) during the peak epoch of galaxy formation (at redshifts 2.3 < z < 3.4). We identified ERQs in the Sloan Digital Sky Survey III (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) quasar catalog based on their extremely red i–W3 colors, but we find that ERQs typically have a suite of other extreme properties including 1) a high incidence of blueshifted broad absorption lines, 2) broad emission lines with unusually large rest equivalent widths (REWs), peculiar “wingless” profiles, and frequent large blueshifts (reaching ˜8740 km s-1), and 3) characteristically very broad and blueshifted [OIII] 4959,5007Å lines that trace ionized outflows at speeds up to ˜6700 km s-1. We propose that these ERQs represent a young quasar population with powerful outflows on the precipice of causing important disruptive feedback effects in their host galaxies.

SDSS J163459.82+204936.0: A RINGED INFRARED-LUMINOUS QUASAR WITH OUTFLOWS IN BOTH ABSORPTION AND EMISSION LINES

ABSTRACT SDSS J163459.82+204936.0 is a local (z = 0.1293) infrared-luminous quasar with L IR = 1011.91 . We present a detailed multiwavelength study of both the host galaxy and the nucleus. The host galaxy, appearing as an early-type galaxy in the optical images and spectra, demonstrates violent, obscured star formation activities with SFR ≈ 140 yr−1, estimated from either the polycyclic aromatic hydrocarbon emission or IR luminosity. The optical to NIR spectra exhibit a blueshifted narrow cuspy component in Hβ, He i λλ5876, 10830, and other emission lines consistently with an offset velocity of ≈900 , as well as additional blueshifting phenomena in high-ionization lines (e.g., a blueshifted broad component of He i λ10830 and the bulk blueshifting of [O iii]λ5007), while there exist blueshifted broad absorption lines (BALs) in Na i D and He i λλ3889, 10830, indicative of the active galactic nucleus outflows producing BALs and emission lines. Constrained mutually by the several BALs in the photoionization simulations with Cloudy, the physical properties of the absorption line outflow are derived as follows: density 104 < n H ≲ 105 cm−3, ionization parameter 10−1.3 ≲ U ≲ 10−0.7 , and column density 1022.5 ≲ N H ≲ 1022.9 cm−2, which are similar to those derived for the emission line outflows. This similarity suggests a common origin. Taking advantages of both the absorption lines and outflowing emission lines, we find that the outflow gas is located at a distance of ∼48–65 pc from the nucleus and that the kinetic luminosity of the outflow is 1044–1046 . J1634+2049 has a off-centered galactic ring on the scale of ∼30 kpc that is proved to be formed by a recent head-on collision by a nearby galaxy for which we spectroscopically measure the redshift. Thus, this quasar is a valuable object in the transitional phase emerging out of dust enshrouding as depicted by the co-evolution scenario invoking galaxy merger (or violent interaction) and quasar feedback. Its proximity enables our further observational investigations in detail (or tests) of the co-evolution paradigm.

Extragalactic jets of broad absorption line (BAL) quasars

AbstractFast outflows of the ionized plasma, probably lunched in proximity of Supermassive Black Hole, are responsible for blue-shifted Broad Absorption Lines (BALs) in quasar spectrum. Outflows together with powerful jets produced in AGN are important feedback processes. Therefore, understanding physics behind BAL outflows might be a key to comprehend Galaxy Evolution as a whole. Discovery of the existence of radio-loud BAL quasars gave us another opportunity to study the BAL phenomenon, this time on the ground on radio emission. The radio emission is an additional tool to understand the BAL quasars, their orientation and age, by the VLBI imaging (detection of radio jets and their direction, size determination), the radio-loudness parameter distribution and variability study.

The radio core and jet in the broad absorption-line quasar PG 1700+518

Abstract The blueshifted broad absorption lines (BAL) or troughs are observed in active galactic nuclei (AGNs) when our line of sight is intercepted by a high-speed outflow (wind), likely originating in the accretion disc. The outflow or wind can shed light on the internal structure obscured by the AGN torus. Recently, it has been shown that this outflow is rotating in the BAL quasar PG 1700+518, further supporting the accretion disc origin of the wind. With the purpose of giving independent constraints on the wind geometry, we performed high-resolution European very long baseline interferometry (VLBI) Network (EVN) observations at 1.6 GHz in 2010. Combining the results with the Very Large Array (VLA) archival data at 8.4 GHz, we present its jet structure on scales of parsec (pc) to kiloparsec (kpc) for the first time. The source shows two distinct jet features in east–west direction with a separation of around 4 kpc. The eastern feature, which has so far been assumed to hide the core, is a kpc-scale hotspot, which is completely resolved out in the EVN image. In the western jet feature, we find a compact jet component, which pinpoints the position of the central black hole in the galaxy. Jet components on both sides of the core are additionally detected in the north-west–south-east direction, and they show a symmetric morphology on scale of <1 kpc. This two-sided jet feature is not common in the known BAL quasars and indicates that the jet axis is far away from the line of sight. Furthermore, it is nearly parallel to the scattering plane revealed earlier by optical polarimetry. By analogy to polar-scattered Seyfert 1 galaxies, we conclude that the jet likely has a viewing angle around 45°. The analogy is further supported by the recent report of significant cold absorption in the soft X-rays, a nearly unique feature to polar-scattered Seyfert galaxies. Finally, our observations have confirmed the earlier finding that the majority of radio emission in this galaxy arises from AGN activity rather than star formation.

A polar+equatorial wind model for broad absorption line quasars

Despite all the studies, the geometry of the wind at the origin of the blueshifted broad absorption lines (BAL) observed in nearly 20% of quasars still remains a matter of debate. We want to see if a two-component polar+equatorial wind geometry can reproduce the typical BAL profiles observed in these objects. We built a Monte Carlo radiative transfer code (called MCRT) to simulate the line profiles formed in a polar+equatorial wind in which the photons, emitted from a spherically symmetric core are resonantly scattered. Our goal is to reproduce typical C IV line profiles observed in BAL quasars and to identify the parameters governing the line profiles. The two-component wind model appears to be efficient in reproducing the BAL profiles from the P Cygni-type profiles to the more complex ones. Some profiles can also be reproduced with a pole-on view. Our simulations provide evidence of a high-velocity rotation of the wind around the polar axis in BAL quasars with non P Cygni-type line profiles.

A Quasar with Broad Absorption in the Balmer Lines

I report the discovery of blueshifted broad absorption line (BAL) troughs in at least six transitions of the Balmer series of hydrogen (Hβ to H9), and in Ca II, Mg II, and excited Fe II in the quasar SDSS J125942.80+121312.6. This is only the fourth active galactic nucleus known to exhibit Balmer absorption, all four of which also exhibit low-ionization BAL systems containing excited Fe II. The substantial population in the n = 2 shell of H I in this quasar's absorber likely arises from Lyα trapping. In an absorber sufficiently optically thick to show Balmer absorption, soft X-rays from the quasar penetrate to large τLyα and ionize H I. Recombination then creates Lyα photons that increase the n = 2 population by a factor of τLyα, since they require ≃τLyα scatterings to diffuse out of the absorber. Observing Lyα trapping in a quasar absorber requires a large but Compton-thin column of gas along our line of sight, which includes substantial H I but not too much dust. Presumably, the rarity of Balmer line BAL troughs reflects the rarity of such conditions in quasar absorbers.

Relativistic Outflow in CXOCDFS J033260.0-274748

In this Letter we report the detection of a strong and extremely blueshifted X-ray absorption feature in the 1 Ms Chandra spectrum of CXOCDFS J033260.0-274748, a quasar at z = 2.579 with L2-10 keV ~ 4 × 1044 ergs s-1. The broad absorption feature at ~6.3 keV in the observed frame can be fitted either as an absorption edge at 20.9 keV or as a broad absorption line at 22.2 keV rest frame. The absorber has to be extremely ionized with an ionization parameter ξ ~ 104, and a high column density, NH > 5 × 1023 cm-2. We reject the possibility of a statistical or instrumental artifact. The most likely interpretation is an extremely blueshifted broad absorption line or absorption edge, due to H or He-like iron in a relativistic jetlike outflow with bulk velocity of ~0.7c-0.8c. Similar relativistic outflows have been reported in the X-ray spectra of several other AGNs in the past few years.

X‐Ray Observations of Markarian 231

This paper presents new X-ray observations of Mrk 231, an active galaxy of particular interest because of its large infrared luminosity and the presence of several blueshifted broad absorption line (BAL) systems, a phenomenon observed in a small fraction of QSOs. A ROSAT HRI image of Mrk 231 is presented, which shows an extended region of soft X-ray emission covering several tens of kiloparsecs, consistent with the extent of the host galaxy. An ASCA observation of Mrk 231 is also presented. Hard X-rays are detected, but the data show no significant variability in X-ray flux. The hard X-ray continuum is heavily attenuated, and X-ray column estimates range from ~2×1022 to 1023 cm-2, depending on whether the material is assumed to be neutral or ionized, and depending on the model assumed for the extended X-ray component. These ASCA data provide only the second hard X-ray spectrum of a BAL active galactic nucleus presented to date. The broadband spectral energy distribution of the source is discussed. While Mrk 231 is X-ray weak compared to Seyfert 1 galaxies, it has an optical-to-X-ray spectrum typical of a QSO.