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1. Balmer Absorption in Iron Low-ionization Broad Absorption Line Quasars

   https://doi.org/10.3847/1538-4357/ae04df  

   Leighly, Karen M; Gallagher, Sarah C; Choi_최, Hyunseop 현섭; Terndrup, Donald M; Voelker, Julianna R; Richards, Gordon T; Morabito, Leah K (October 2025, The Astrophysical Journal)

   Abstract While Civis the most common absorption line in broad absorption line quasar spectra, Balmer absorption lines (BALs) are among the rarest. We present analysis of Balmer absorption in a sample of 14 iron low-ionization BAL quasars (FeLoBALQs); eight are new identifications. We measured velocity offset, width, and apparent optical depth. The partial covering that is ubiquitous in BAL quasar spectra alters the measured Balmer optical depth ratios; accounting for this, we estimated the true H(n= 2) column density. We found the anticipated correlation between Eddington ratio and outflow speed, but it is weak in this sample because nearly all of the objects have the low outflow speeds characterizing loitering outflow FeLoBAL quasars, objects that are also found to have low accretion rates. Measurements ofdN/dv, the differential column density with respect to the outflow speed, are anticorrelated with the luminosity and Eddington ratio: the strongest absorption is observed at the lowest speeds in the lowest-luminosity objects. The absorption line width is correlated withα_oi, theF_λpoint-to-point slope between 5100 Å and 3μm. This parameter is strongly correlated with the Eddington ratio among low-redshift quasars. BALs have been recently found in the spectra of little red dots (LRDs), a class of high-redshift objects discovered by JWST. We note suggestive similarities between LRDs and FeLoBAL quasars in the emission-line shape, the presence of steep reddening and a scattered blue continuum, the lack of hot dust emission, and X-ray weakness. 

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2. Gemini Near Infrared Spectrograph−Distant Quasar Survey: Rest-frame Ultraviolet−Optical Spectral Properties of Broad Absorption Line Quasars

   https://doi.org/10.3847/1538-4357/ad3e69  

   Ahmed, Harum; Shemmer, Ohad; Matthews, Brandon; Dix, Cooper; Ha, Trung; Richards, Gordon_T; Brotherton, Michael_S; Myers, Adam_D; Brandt, W_N; Gallagher, Sarah_C; et al (June 2024, The Astrophysical Journal)

   Abstract We present the rest-frame ultraviolet−optical spectral properties of 65 broad absorption line (BAL) quasars from the Gemini Near Infrared Spectrograph−Distant Quasar Survey (GNIRS-DQS). These properties are compared with those of 195 non-BAL quasars from GNIRS-DQS in order to identify the drivers for the appearance of BALs in quasar spectra. In particular, we compare equivalent widths and velocity widths, as well as velocity offsets from systemic redshifts, of principal emission lines. In spite of the differences between their rest-frame ultraviolet spectra, we find that luminous BAL quasars are generally indistinguishable from their non-BAL counterparts in the rest-frame optical band at redshifts 1.55 ≲z≲ 3.50. We do not find any correlation between BAL trough properties and the Hβ-based supermassive black hole masses and normalized accretion rates in our sample. Considering the Sloan Digital Sky Survey quasar sample, which includes the GNIRS-DQS sample, we find that a monochromatic luminosity at rest-frame 2500 Å of ≳10⁴⁵erg s⁻¹is a necessary condition for launching BAL outflows in quasars. We compare our findings with other BAL quasar samples and discuss the roles that accretion rate and orientation play in the appearance of BAL troughs in quasar spectra. 

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3. Shedding New Light on Weak Emission-line Quasars in the C iv–Hβ Parameter Space

   https://doi.org/10.3847/1538-4357/acd04d  

   Ha, Trung; Dix, Cooper; Matthews, Brandon M.; Shemmer, Ohad; Brotherton, Michael S.; Myers, Adam D.; Richards, Gordon T.; Maithil, Jaya; Anderson, Scott F.; Brandt, W. N.; et al (June 2023, The Astrophysical Journal)

   Abstract Weak emission-line quasars (WLQs) are a subset of type 1 quasars that exhibit extremely weak Lyα+ Nvλ1240 and/or Civλ1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 “ordinary” type 1 quasars and 18 WLQs atz< 0.5 and 1.5 <z< 3.5 that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the Hβ-based black hole mass (M_BH) estimates of these quasars using the strength of the optical Feiiemission. We confirm previous findings that WLQs’M_BHvalues are overestimated by up to an order of magnitude using the traditional broad-emission-line region size–luminosity relation. With thisM_BHcorrection, we find a significant correlation between Hβ-based Eddington luminosity ratios and a combination of the rest-frame Civequivalent width and Civblueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional Civparameter space can serve as an indicator of accretion rate in all type 1 quasars across a wide range of spectral properties. 

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4. The SDSS-V Black Hole Mapper Reverberation Mapping Project: C iv Broad Absorption Line Acceleration in the Quasar SBS 1408+544

   https://doi.org/10.3847/1538-4357/ad429e  

   Wheatley, Robert; Grier, Catherine_J; Hall, Patrick_B; Brandt, W_N; Lotz, Jonah; Schneider, D_P; Trump, Jonathan_R; Shen, Yue; Seaton, Lucas_M; Anderson, Scott_F; et al (June 2024, The Astrophysical Journal)

   Abstract We present the results of an investigation of a highly variable Civbroad absorption line (BAL) feature in spectra of the quasar SBS 1408+544 (z= 2.337) that shows a significant shift in velocity over time. This source was observed as a part of the Sloan Digital Sky Survey (SDSS) Reverberation Mapping project and the SDSS-V Black Hole Mapper Reverberation Mapping project, and has been included in two previous studies, both of which identified significant variability in a high-velocity CivBAL on timescales of just a few days in the quasar rest frame. Using ∼130 spectra acquired over 8 yr of spectroscopic monitoring with SDSS, we have determined that this BAL is not only varying in strength, but is also systematically shifting to higher velocities. Using cross-correlation methods, we measure the velocity shifts (and corresponding acceleration) of the BAL over a wide range of timescales, measuring an overall velocity shift of $\mathrm{\Delta }v=-{683}_{-84}^{+89}$km s⁻¹over the 8 yr monitoring period. This corresponds to an average rest-frame acceleration ofa= 1.04 ${}_{-0.13}^{+0.14}$cm s⁻², though the magnitude of the acceleration on shorter timescales is not constant throughout. We place our measurements in the context of BAL-acceleration models and examine various possible causes of the observed velocity shift. 

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5. The host galaxies of radio-loud quasars at z > 5 with ALMA

   https://doi.org/10.1051/0004-6361/202451290  

   Mazzucchelli, C; Decarli, R; Belladitta, S; Bañados, E; Meyer, R A; Connor, T; Momjian, E; Rojas-Ruiz, S; Eilers, A-C; Khusanova, Y; et al (February 2025, Astronomy & Astrophysics)

   The interaction between radio jets and quasar host galaxies plays a paramount role in quasar and galaxy co-evolution. However, very little is known at present about this interaction at very high−z. Here, we present new Atacama Large Millimeter/submillimeter Array (ALMA) observations in Bands 7 and 3 of six radio-loud (RL) quasar host galaxies atz > 5. We recovered [C II] 158 μm line and underlying dust continuum emission at > 2σfor five sources, while we obtained upper limits for the CO(6-5) emission line and continuum for the remaining source. At the spatial resolution of our observations (∼1″​​_.0–1″​​_.4), we did not recover any perturbed or extended morphologies or kinematics, which are known signatures of potential mergers. These galaxies already host large quantities of gas (∼10¹⁰M_⊙), with [C II] luminosities ofL_[C II] ∼ 10^8 − 9 L_⊙and [C II]-based star formation rates of 30 − 400 M_⊙yr⁻¹. In building their radio/submillimeter (radio/submm) spectral energy distributions (SEDs), we found that in at least four cases, the 1 mm continuum intensity arises from a combination of synchrotron and dust emission. The initial estimation of synchrotron contribution at 300 GHz in these cases is of ≳10%. Assuming a scenario where the continuum emission is solely due to cold dust as an upper limit, we obtained infrared (IR) luminosities ofL_IR ∼ 10^{11 − 12} L_⊙. We compared the properties of the sources inspected here with a large collection of radio-quiet sources from the literature, as well as a sample of RL quasars from previous studies at comparable redshifts. We recovered a mild potential decrease inL_[C II]for the RL sources, which might be due to a suppression of the cool gas emission due to the radio jets. We did not find any [C II] emitting companion galaxy candidate around the five RL quasars observed in Band 7. Given the depth of our dataset, this result is still consistent with what has been observed around radio-quiet quasars. Future higher spatial-resolution observations, over a broader frequency range, of high−zRL quasars hosts will allow us to further improve our understanding of the physics of these sources. 

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