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

summary

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

In short

The study characterized powerful ionised outflows in 39 luminous quasars at redshift z~5 using combined UV/optical and FIR tracers from VLT/X-Shooter and ALMA. Researchers found high-velocity outflows exceeding 48,000 km/s, suggesting efficient black hole feedback is active around z~6 and continuing to z~5. A correlation exists between absorption and emission outflows, indicating different physical mechanisms might be involved.

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.

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This episode discusses

The paper

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

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

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.

DOI: 10.1051/0004-6361/202554010

Transcript

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>.

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