Multi-phase investigation of outflows in the circumgalactic and interstellar media of luminous quasars at z 5

arXiv:2504.20136 · astro-ph.GA · Submitted 2025-04-28 · Read on arXiv

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Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: Today's paper: "Multi-phase investigation of outflows in the circumgalactic and interstellar media of luminous quasars at z 5".

Jocelyn: The gist:

Vera: First, who's behind it and why it matters.

Paper summary: Vera: So, to recap where we are, this paper is tackling the problem of multi-phase and multi-scale outflows by using different tracers on a sample of z five quasars <ref:2504.20136#pg1,multi-phase and multi-scale>. We've seen they show powerful outflows in both emission and absorption with high velocities.

Jocelyn: The thesis is that combining these different tracers allows for a complete characterization of these outflows, which is what the paper sets out to do. They are using UV/optical and FIR continuum, line emission, and absorption data across thirty-nine quasars observed with VLT/X-Shooter and ALMA.

Subrahmanyan: The focus on massive and luminous quasars at redshifts between z five and z five point seven gives them a specific context for this study <ref:2504.20136#pg1>. They are looking at objects where the black hole mass is quite high, around log(M BH,MgII) = eight point five to ten and the bolometric luminosity is in the range of log(L bol/(erg/s)) = forty-six point nine to forty-eight.

Vera: The key claim they make is that these objects display powerful ionized outflows detected in both emission and absorption, with velocities exceeding forty-eight thousand km/s in some cases. They also note that these quasars lie above the local black hole-host galaxy mass relation, behaving similarly to z six quasars <ref:2504.20136#pg1>.

Jocelyn: And beyond that, they find a correlation between the absorption and emission phenomena. Specifically, the fraction of quasars with outflow detections in absorption increases as the velocity shift between C iv and Mg ii gets more extreme.

Subrahmanyan: This points toward a phase of efficient black hole feedback occurring at redshift z six and persisting down to z five characterized by rapid black hole growth exceeding that of the host galaxy <ref:2504.20136#pg1>. It suggests that the black hole was growing faster than its host galaxy at these early epochs.

Vera: So what this means for us is that we're seeing evidence of this intense feedback mechanism continuing into the z five epoch, which is very relevant when we consider how quickly these massive black holes grew in the early universe <ref:2504.20136#pg1>.

Jocelyn: It also implies that there are distinct physical mechanisms at play, even though they are correlated. The paper mentions that while the physical mechanisms powering the two outflows detected in emission and absorption might differ, there's still a correlation between them.

Subrahmanyan: That distinction is important because it means we can't just treat these as one single process; we have to consider different scales or phases of feedback. This paper is trying to map out those different scales using multiple tracers across the sample.

Conclusion: Vera: So, looking at the whole "Multi-phase investigation of outflows in the circumgalactic and interstellar media of luminous quasars at z five" paper, it really boils down to providing a complete characterization of these high-redshift outflows <ref:2504.20136#pg1,Multi-phase investigation of outflows in the circumgalactic and interstellar media of>. They achieved this by combining emission and absorption tracers.

Jocelyn: The authors used UV/optical continuum, line emission, FIR continuum, line emission, and absorption across thirty-nine quasars observed with VLT/X-Shooter and ALMA to achieve this comprehensive view of the outflows.

Subrahmanyan: They found that these luminous quasars at z five show powerful ionized outflows detected in both emission and absorption, with velocities going over forty-eight thousand km/s in some instances. This is important because it shows that black hole feedback was active at this epoch.

Vera: And the finding that they lie above the local black hole-host galaxy mass relation suggests a phase of efficient feedback occurring around z six and continuing down to z five where the black holes were growing faster than their host galaxies <ref:2504.20136#pg1>.

Jocelyn: The paper also found that there is a correlation between these absorption and emission outflows, meaning they might represent different physical scales or phases of the same outflow process.

Subrahmanyan: Ultimately, this work shows that we need to consider multiple tracers together to fully understand the complex feedback processes regulating black hole and galaxy co-evolution at high redshift.

Vera: Yeah, it's about mapping out those different scales using multiple tracers across the sample of z five quasars in this paper <ref:2504.20136#pg1>.

Department of Physics, Astronomy Section, University of Trieste · INAF - Osservatorio Astronomico di Trieste · IFPU - Institute for Fundamental Physics of the Universe · Scuola Normale Superiore · Department of Physics & Astronomy, University of California, Riverside · Faculty of Mathematics and Physics, University of Ljubljana

astro-ph.GA

Submitted: 2025-04-28

Updated: 2026-10-15

Comments: 19 pages, 14 figures. Published in A&A

Journal ref: A&A 698, A145 (2025)

DOI: 10.1051/0004-6361/202554010

Project page: https://das-oats.github.io/astrocook

License: http://creativecommons.org/licenses/by/4.0/

Importance score: 79/100

The gist: The gist: This work provides a complete characterisation of outflows in a sample of z ∼ 5 quasars by exploiting the combination of different emission and absorption tracers Outflow Tracers and

Key concepts

Outflows from Active Galactic Nuclei (AGN)
These are powerful winds or jets ejected from the central supermassive black hole in a quasar. They are considered the main feedback mechanism that regulates how fast the black hole and its host galaxy grow together over cosmic time.
Absorption Line Analysis
This method involves searching for specific absorption lines (like C IV and N V) in the quasar's light. These lines trace gas structures physically close to the central AGN, helping researchers map out the material that is being blown away by the outflow.
Emission Line Analysis
This technique uses spectral lines emitted by gas moving rapidly away from or toward the quasar. Analyzing these emission lines helps determine key properties of the black hole, such as its mass and how much energy it releases (bolometric luminosity).
Black Hole-Host Galaxy Mass Relation
This is a relationship showing how the mass of a supermassive black hole compares to the mass of its surrounding host galaxy. The study found that at high redshift (z~5), the black holes were already growing faster than their host galaxies, suggesting early, efficient feedback.

Terminology

Summary

The gist: This work provides a complete characterisation of outflows in a sample of z ∼ 5 quasars by exploiting the combination of different emission and absorption tracers

Outflow Tracers and Characterization

The study analyzed UV/optical and FIR continuum, line emission, and absorption in a sample of 39 z ∼ 5 quasars observed with VLT/X-Shooter and ALMA The aim was to provide a complete characterisation of outflows by exploiting the combination of different emission and absorption tracers Outflows from active galactic nuclei are invoked as the principal feedback process regulating the co-evolution of supermassive black holes and their host galaxies The sample encompasses massive (MBH,Mg ii = 108.5−10M⊙) and luminous (Lbol = 1046.9−48 erg/s) quasars at redshift 5 − 5.7 They display powerful ionised outflows detected in both emission and absorption, with velocities exceeding 48,000 km s−1 in some cases These findings suggest a phase of efficient black hole feedback occurring at redshift z ∼ 6 and likely persisting down to z ∼ 5

Absorption Line Analysis

The analysis systematically searched for Civ and N v NAL systems lying in the quasar proximity zone, which are thought to trace quasar environments and gaseous structures physically bound to the central AGN The study used a velocity threshold of 200 km s−1 to group individual absorption components into single absorption systems The clustering procedure led to 50 C iv associated absorption systems and 22 N v associated absorption systems, resulting in a total of 19 associated systems presenting both C iv and N v absorption Among the identified Civ+N v NAL systems, the fraction that presents an N v counterpart is approximately 37% (13 sources over 39)

Emission Line and Quasar Property Modeling

The analysis of UV emission lines and the quasar UV emission spectrum involved fitting a power law combined with a Fe ii pseudocontinuum for the continuum, along with multiple Gaussian components for the emission lines Black hole masses were estimated from Vestergaard & Osmer (2009) and Vestergaard & Peterson (2006) scaling relations for Mg ii and Civ lines The bolometric luminosity was estimated using the bolometric correction from Richards et al. (2006), and the Eddington ratio as λEdd,Mg ii = Lbol/LEdd,Mg ii For the six objects with ALMA observations, four sources showed [Cii] emission with S/N ≥ 5 The molecular mass content derived from the Mmol − L[C ii] relation spanned from ∼ 109M⊙ to 3 · 1010M⊙

Comparison and Correlation of Outflows

The combined analysis of absorption and emission tracers reveals a clear correlation between the two phenomena, suggesting they may represent distinct phases and/or physical scales of the same outflow process The fraction of quasars with ionised outflow detections in absorption increases as the velocity shift becomes more and more extreme, exceeding 50% for ∆v(Civ-Mg ii) < -2000 km s−1 This suggests that while the physical mechanisms powering the two outflow phenomena detected in emission and absorption may differ, a correlation exists between them

Host Galaxy Co-evolution

The MBH/Mdyn ratio for the four analyzed objects spans from 0.007 to 0.047 When combined with other literature data, the median (mean) ratio is 0.051 (0.105), consistent with previous findings of Farina et al. (2022) The MBH/Mhost ratio increases by a factor > 20 from z ∼ 0 to z ∼ 5, implying that black hole growth must have preceded that of the host galaxy at early epochs

Conclusion

The study provides clear evidence of ionised outflows, revealed through both absorption and emission measurements By combining these two complementary approaches, the analysis aims to provide a comprehensive characterisation of high-redshift outflows and early feedback mechanisms occurring in the postreionisation Universe >

Appendix A: Properties of absorption systems

Table A.1 lists the properties of C iv absorption systems, including quasar name, emission redshift, redshift and velocity separation of the absorber, its rest-frame Civ equivalent width, and C iv column density

Appendix B: Quasar properties from UV emission lines

Table B.1 presents the derived quasar physical quantities such as redshift, lines FWHM, Civ blueshift, Civ–Mg ii velocity shift, monochromatic luminosity at 3000Å, bolometric luminosity, black hole mass, and Eddington ratio

Appendix C: Comparison of emission line profiles

Figure C.1 compares the Civ, Mg ii and [Cii] emission line profiles for each quasar of the sample

Appendix D: Connecting intrinsic NAL and quasar properties

Figure D.1 shows absorption system velocities, vabs, and Civ equivalent widths versus quasar properties

Appendix B: Quasar properties from UV emission lines (Re-listed for completeness)

Table B.1 presents the derived quasar physical quantities such as redshift, lines FWHM, Civ blueshift, Civ–Mg ii velocity shift, monochromatic luminosity at 3000Å, bolometric luminosity, black hole mass, and Eddington ratio

Appendix C: Comparison of emission line profiles (Re-listed for completeness)

Figure C.1 compares the Civ, Mg ii and [Cii] emission line profiles for each quasar of the sample

Appendix D: Connecting intrinsic NAL and quasar properties (Re-listed for completeness)

Figure D.1 shows absorption system velocities, vabs, and Civ equivalent widths versus quasar properties

Appendix A: Properties of absorption systems (Re-listed for completeness)

Table A.1 lists the properties of C iv absorption systems, including quasar name, emission redshift, redshift and velocity separation of the absorber, its rest-frame Civ equivalent width, and C iv column density

Appendix B: Quasar properties from UV emission lines (Re-listed for completeness)

Table B.

Improvements for AI systems

  1. Improve black hole mass estimation accuracy by incorporating systematic uncertainties, as the statistical uncertainty is characterised by a median value of ∼ 0.1 dex while the systematic uncertainty derives from the single-epoch virial relations can be as high as ∼0.5 dex.

  2. Develop an AI system capable of distinguishing between different outflow manifestations, specifically correlating broad and narrow absorption lines with emission features by exploiting the finding that a correlation exists between them, and understanding that BALs and NALs represent different manifestations of the same outflow phenomenon.

  3. Create a predictive model for high-redshift quasar feedback by using the observed trend of the mean ∆v(C iv-Mg ii) with redshift to forecast future black hole growth patterns, while accounting for potential selection biases as noted: selection biases could also play a significant role.

  4. Enhance galaxy dynamical mass estimation by integrating ALMA data analysis with emission line studies, enabling the AI to derive dynamical masses within the emitting region using the relation: Mdyn sin2 i = 1.16 · 105 / 0.75 FWHM[Cii]2D.

  5. Build a classification tool for quasars that identifies their phase of feedback by analyzing the presence of specific absorption features, such as distinguishing between sources with CIV+N V NAL systems and those with BAL troughs, to categorize them as tracing ionised outflows.

Abstract

Aims. Outflows from active galactic nuclei are invoked as the principal feedback process regulating the co-evolution of supermassive black holes and their host galaxies. Because of their multi-phase and multi-scale nature, an exhaustive description of these winds should exploit multiple tracers. However, connecting various outflow features remains a challenge. The aim of this work is to provide a complete characterisation of outflows in a sample of z 5 quasars, by exploiting the combination of different emission and absorption tracers. Methods. We analysed the UV/optical and FIR continuum, line emission, and absorption in a sample of 39 z 5 quasars observed with VLT/X-Shooter and ALMA (available for six objects). We identified broad and narrow absorption lines associated with the quasar and emission lines to determine black hole masses and bolometric luminosities. Results. Our sample encompasses massive (log(M BH,MgII / M sun) = 8.5-10) and luminous (log(L bol/(erg/s)) = 46.9-48) quasars at redshift 5.0-5.7. They display powerful ionised outflows detected in both emission and absorption, with velocities exceeding 48,000 km/s in some cases, and lie above the local black hole-host galaxy mass relation, exhibiting a behaviour similar to that of z 6 quasars. These findings suggest a phase of efficient black hole feedback occurring at redshift z 6 and likely persisting down to z 5, characterised by rapid black hole growth exceeding that of the host galaxy. The fraction of quasars with outflow detections in absorption is higher for larger CIV-MgII velocity shifts, suggesting that while the physical mechanisms powering the two outflow phenomena detected in emission and absorption may differ, a correlation exists between them.

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