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Some of my results on outflows driven by supermassive black holes
Some of my results on outflows driven by supermassive black holes
AGN-driven outflows in clumpy media: multiphase structure and scaling relations
AGN-driven outflows in clumpy media: multiphase structure and scaling relations
Figure from Ward, Costa, Harrison & Mainieri 2024, MNRAS, 573, 1733 (2024), arXiv:2407.17593, ADS
Across two papers, Samuel Ward (a PhD student in my group at the time) developed a new set of controlled numerical experiments to explore how a quasar wind interacts with a clumpy, multi-phase interstellar medium (ISM). A variety of ISM conditions and AGN powers were explored. The simulations show the vastly different multi-phase structure of the resultant outflows compared to a smooth disk, and equivalent assumptions used in analytical models of AGN-driven outflows.
The first paper explores many important characteristics of the energy, mass and momentum content of these outflows - and the implications for observed outflows. This includes how outflows could be miss-interpreted as momentum- or energy-driven, how the multi-phase content is subject to many uncertainties and how kinetic coupling efficiencies are not easy to interpret. Predictions for outflow scaling relationships (i.e., energy and mass content as a function of AGN power) are also explored.
In the second paper, predictions are made for the X-ray emission produced by the interaction of the quasar winds with the ISM material. Thermal Bremsstrahlung and high-ionization metal line emission is produced in the mixing phase and we find that it could contribute significantly to the X-ray output of the outflow. The level could contribute as much to the soft X-ray luminosities as that produced by star formation in the host galaxies.
Figure from Ward, Costa, Harrison & Mainieri 2026, MNRAS, 545, pTBC, (2026), arXiv:2511.14834, ADS
The figure shows a quasar wind (coming from the direction of the arrow) interacting with a cold gas cloud in the ISM. The panels show the predicted X-ray emission (first panel), the temperature (second panel), density (third panel), and the different phases of the gas (right-most panel). The strongest X-rays are coming from the mixed wind/ISM material.
The Quasar Feedback Survey: Multi-phase outflows, turbulence and evidence for feedback caused by low power radio jets
The Quasar Feedback Survey: Multi-phase outflows, turbulence and evidence for feedback caused by low power radio jets
Figure from Girdhar, Harrison et al. 2022, MNRAS, 512, 1608, (2022), arXiv:2201.02208, ADS
The Figure shows, a summary set of figures from Girdhar et al. (2022) for J1316+1753. The left-most panel is a schematic summary of the main findings of the study. The central panel is a stellar velocity dispersion map, not the enhanced stellar velocities along the jet axis. The right-upper panel is a velocity width map (W80) for the molecular gas (CO(3-2)), note the enhanced velocity dispersion expanding above the jet. The right-bottom panel is a velocity width map (W80) for the ionised gas ([O III]), note the cones of ~1000 km/s gas both above and below the jet axis.
As part of her PhD, Aish Girdhar perform analysis on multi-phase outflow measurements of sources from the Quasar Feedback Survey.
In the first paper we present multi-wavelength observations of one of the targets, J1316+1753, including MUSE, ALMA and VLA. The source has small (~1kpc) and low power radio jets that are inclined into the host galaxy disk. Our data reveal that these jets are causing high levels of outflowing turbulent gas in both the ionised gas and the molecular gas. This gas is expanding in an apparent cone above and below the disk. The jets are seen to be strongly interacting with the interstellar medium (ISM) through enhanced ionised emission and disturbed/depleted molecular gas at the jet termini. We see further evidence for jet-induced feedback through significantly higher stellar velocity-dispersion aligned, and co-spatial with, the jet axis (<5 deg). We discuss how jet-induced feedback could be an important feedback mechanism even in bolometrically luminous ‘radio-quiet’ quasars.
In the second paper we explored four targets from the Quasar Feedback Survey. which exhibit radio structueson ~10 kiloparsec scales. We focussed on the molecular gas emission traced via CO(3-2) in ALMA observations. The inferred velocities (v = 250-440 km/s) and spatial scales (0.6-1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9-53 per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jet-cloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation.
Figure from Girdhar, Harrison et al. 2024, MNRAS, 527, 9322 (2024), arXiv:2311.03453, ADS
The figure shows the two targets from this survey that exhibit extended molecular gas structures around ~10 kpc radio lobes (radio emission traced by the contours). The maps shows the velocities of the CO(3-2) emission.
Extreme ionised outflows are more prevalent when the radio emission is compact in AGN host galaxies
Extreme ionised outflows are more prevalent when the radio emission is compact in AGN host galaxies
Figure from Molyneux, Harrison and Jarvis 2019, A&A, 631, 132, (2019), arXiv:1909.05260, ADS
In Molyneux et al. 2019, we investigated the connection between radio emission and ionised outflows. We used the ~3000 SDSS-selected z<0.2 AGN from Mullaney+13 which have a radio detection in FIRST and/or NVSS radio surveys. We then determined which sources were extended or compact in the radio using a mixture of direct radio size measurements and morphological classifications and searched for ionised outflows using the [O III] emission line.
The Figure shows, example 1.4 GHz images (≈5 arcsec resolution from FIRST) and, where available, overlaid green contours from ≈1 arcsec resolution 1.4 GHz images (from our follow up VLA observations on a subset of targets). The insets show ≈0.3 arcsec resolution 6 GHz images (with blue contours). Synthesised beams are represented by appropriately coloured ellipses. Compact radio sources (top row) have their radio emission dominated within the SDSS fibre extent (magenta circles), whilst extended sources (bottom row) show significant emission outside of this. Right: Cumulative fraction of AGN with [O III] emission-line components with FWHMB greater than a given value, for: all sources (blue curve), compact radio sources (orange curve) and extended radio sources (green curve). Extreme ionised gas velocities are more prevalent for compact radio sources. This reveals a strong connection between radio emission and ionised outflows; possibly due to compact radio jets which are interacting with the host galaxy.
AGN outflows and feedback 20 years on
AGN outflows and feedback 20 years on
Figure from Harrison et al. 2018, NatAs, 2, 198, (2018), arXiv:1802.10306, ADS
In 2018 I wrote a review covering the challenges of measuring AGN outflow properties and understanding their impact (in particular in relation to simulations).
The figure shows a compilation of observationally determined kinetic coupling efficiencies for warm ionised gas from optical or near-infrared (NIR) emission lines (circles) and cold molecular gas from CO emission lines (squares). Hollow symbols are for single galaxies and filled symbols are for galaxy samples. The vertical lines show the range of values quoted, or in the case of an error bar, the quoted error on the average value. The horizontal lines show the range of bolometric luminosity for each sample. In the left panel we show the efficiencies that we found explicitly quoted as the representative/typical values in the abstracts (for warm ionised outflows) or within the papers (for cold molecular outflows) from our ADS search of the “active & galactic & nuclei & outflows” subset described in Figure 1 (see Table 1). The middle panel shows the compilation from Fiore et al. where kinetic powers were derived from literature observations using a uniform set of assumptions (no errors are provided by the authors). The horizontal dashed line in these two panels shows the “representative” (but variable) kinetic coupling efficiency calculated by Costa et al. The right panel shows coupling efficiencies employed by fiducial AGN feedback models, using the “quasar mode” value where applicable. In these models, a 100% of the injected energy is unlikely to become kinetic power in the outflow, so E_kin/L_AGN < εf , and direct comparisons to observed kinetic coupling efficiencies should not be made.
Storm in a Teacup: X-ray, radio and ionised gas bubbles from a `radio quiet' quasar
Storm in a Teacup: X-ray, radio and ionised gas bubbles from a `radio quiet' quasar
Figure from Lansbury, Jarvis, Harrison et al. 2018, ApJL, 856, 1, arXiv:1803.00009
Chandra Popular Releases about article
"Storm Rages in Cosmic Teacup" (image and article)
"Storm Rages in Cosmic Teacup" (videos)
Using Chandra time (that I obtained as PI) my team observed the Teacup AGN, which we had previously identified as having large bubbles of ionised gas (green colour in image) and radio emission (red colour in image) to obtain spatially-resolved X-ray measurements. Using these data, in combination with existing XMM-Newton X-ray observations , we obtained the best constraints to date on the bolometric output (and level of obscuring material) of the growing supermassive black hole at the centre of this galaxy. These results revealed that the quasar may not be "fading away" as previously thought, based on earlier less robust constraints on the bolometric output. Furthermore, in the Chandra data we detected the large bubble in X-ray emission (see blue contours in image), providing tentative evidence for a very hot outflowing gas component within the bubble. This source appears to be showing outflows in multiple phases of gas, driven by the supermassive black hole lurking at its centre.
The prevalence of ionised outflows in high-redshift AGN
The prevalence of ionised outflows in high-redshift AGN
Figure from Harrison et al. 2016b, MNRAS, 456, 1195, (2016), arXiv:1511.00008
ESO messenger articles on this survey:
Using KMOS we have built up the largest ever sample of distant AGN with integral field spectroscopic observations. This KASHz survey is providing crucial information on the prevalence and properties of ionised outflows in the host galaxies of AGN during the peak epoch of galaxy formation. This figure, from our initial paper of the survey, shows the cumulative fraction of sources with an ionised gas velocity above a certain velocity. Velocities >600 km/s are indicative of outflow-dominated ionised gas kinematics and this is seen in ~50% of distant (z~1.5) AGN - shown by the blue curve. For AGN of matched power, this outflow prevalence agrees with that seen in the local Universe (z<0.4; grey curves).
Galaxy-wide outflows are common among quasars
Galaxy-wide outflows are common among quasars
Figure from Harrison et al. 2014a, MNRAS, 441, 3306 (2014), (arXiv:1403.3086).
Gemini press/popular articles on this paper:
Galaxy-wide Outflows, Powered by Supermassive Black Holes, Common Among Quasars, (2014). Also featured in Gemini Focus Science Highlights July 2014
Gemini Focus Year in Review 2014 (page 30).
Using GMOS’s integral field spectrograph, we traced the properties of the gas across the host galaxies of 16 z<0.2 type 2 (obscured) quasars. Critically, GMOS on Gemini South enabled us to trace the velocity of the gas over the full spatial extent of the quasars’ host galaxies. By using emission lines produced by ionized hydrogen and oxygen to trace the gas velocities the observations revealed that outflows, reaching velocities of >1000 kilometers/second, were found over the full spatial extent of the host galaxies of all of the quasars observed (e.g., see figure). Estimates of the masses involved in these outflows indicate that they are removing significant amounts of gas from the galaxies and their overall properties are in line with model predictions. A key aspect of this work is the quasars that were observed with GMOS were initially selected from a parent sample of several thousand objects with optical spectra. These observations can thus be placed in the context of the overall population and reveal properties of quasars generally. For example, these observations imply that at least ~50% of the most luminous quasars (those predicted by models to drive the feedback mechanisms) exhibit outflows of this type and at least 70% of these outflows are extended of galaxy scales.
Energetic galaxy-wide outflows in high-redshift ultra-luminous infrared galaxies hosting AGN activity
Energetic galaxy-wide outflows in high-redshift ultra-luminous infrared galaxies hosting AGN activity
Figure from Harrison et al. 2012, MNRAS, 426, 1072 (2012) , arXiv:1205.1801.
The figure compares the spatial extent of the [O III] emission with the velocity offsets (left) and the velocity widths (right). The sources in this work are shown as red squares. Also shown are other high-redshift sources with IFU data: z ≈ 2–3 radio galaxies (Nesvadba et al. 2006, 2008), compact radio galaxies (Nesvadba et al. 2007), z ≈ 3.5 obscured quasars (Nesvadba et al. 2011) and a z = 2.4 quasar (Cano-Diaz et al. 2012).
We present integral field spectroscopy observations, covering the [O III] of eight high-redshift (z = 1.4–3.4) ultraluminous infrared galaxies (ULIRGs) that host active galactic nucleus (AGN) activity. We decouple kinematic components due to the galaxy dynamics and mergers from those due to outflows. We find evidence in the four most luminous systems for the signatures of large-scale energetic outflows: extremely broad [O III] emission (full width at half-maximum ≈ 700–1400 km/s) across ≈4–15 kpc, with high velocity offsets from the systemic redshifts (up to ≈850 km/s). The four less luminous systems have lower quality data displaying weaker evidence for spatially extended outflows. These observations show that extreme radio luminosities are not necessary for powerful outflows at cosmic noon, although they may not be as extended as sources with large radio structures (see figure).
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