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1
Tanner, Ryan, and Kimberly A. Weaver. "Simulations of AGN-driven Galactic Outflow Morphology and Content." Astronomical Journal 163, no. 3 (2022): 134. http://dx.doi.org/10.3847/1538-3881/ac4d23.
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Abstract Using a series of 3D relativistic hydrodynamical simulations of active galactic nuclei (AGN) we investigate how AGN power, a clumpy interstellar medium (ISM) structure, and AGN jet angle with respect to the galactic disk affect the morphology and content of the resulting galactic outflow. For low-power AGN across three orders of magnitude of AGN luminosities (1041–1043 erg s−1) our simulations did not show significant changes to either the morphology or total mass of the outflow. Changing the angle of the AGN jet with respect to the galaxy did show small changes in the total outflow mass of a factor of 2–3. Jets perpendicular to the galactic disk created hot single-phase outflows, while jets close to parallel with the disk created multiphase outflows with equal parts warm and hot, and significant cold gas. Overall the final morphology of low-power AGN outflows depends primarily on how the jet impacts and interacts with large, dense clouds in the clumpy ISM. These clouds can disrupt, deflect, split, or suppress the jet, preventing it from leaving the galactic disk as a coherent structure. But for simulations with AGN luminosities > 1044 erg s−1 the ISM played a minor role in determining the morphology of the outflow with an undisrupted jet leaving the disk. The final morphology of AGN outflows is different for low-power AGNs versus high-power AGNs with the final morphology of low-power AGN outflows dependent on the ISM structure within the first kiloparsec surrounding the AGN.
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Wu, Kinwah, Kaye Jiale Li, Ellis R. Owen, Li Ji, Shuinai Zhang, and Graziella Branduardi-Raymont. "Charge-exchange emission and cold clumps in multiphase galactic outflows." Monthly Notices of the Royal Astronomical Society 491, no. 4 (2019): 5621–35. http://dx.doi.org/10.1093/mnras/stz3301.
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ABSTRACT Large-scale outflows from starburst galaxies are multiphase, multicomponent fluids. Charge-exchange lines that originate from the interfacing surface between the neutral and ionized components are a useful diagnostic of the cold dense structures in the galactic outflow. From the charge-exchange lines observed in the nearby starburst galaxy M82, we conduct surface-to-volume analyses and deduce that the cold dense clumps in its galactic outflow have flattened shapes, resembling a hamburger or a pancake morphology rather than elongated shapes. The observed filamentary H α features are therefore not prime charge-exchange line emitters. They are stripped material torn from the slow-moving dense clumps by the faster moving ionized fluid, which are subsequently warmed and stretched into elongated shapes. Our findings are consistent with numerical simulations that have shown that cold dense clumps in galactic outflows can be compressed by ram pressure, and also progressively ablated and stripped before complete disintegration. We have shown that some clumps could survive their passage along a galactic outflow. These are advected into the circumgalactic environment, where their remnants would seed condensation of the circumgalactic medium to form new clumps. The infall of these new clumps back into the galaxy and their subsequent re-entrainment into the galactic outflow form a loop process of galactic material recycling.
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Fluetsch, A., R. Maiolino, S. Carniani, et al. "Properties of the multiphase outflows in local (ultra)luminous infrared galaxies." Monthly Notices of the Royal Astronomical Society 505, no. 4 (2021): 5753–83. http://dx.doi.org/10.1093/mnras/stab1666.
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ABSTRACT Galactic outflows are known to consist of several gas phases; however, the connection between these phases has been investigated little and only in a few objects. In this paper, we analyse Multi Unit Spectroscopic Explorer (MUSE)/Very Large Telescope (VLT) data of 26 local (U)LIRGs and study their ionized and neutral atomic phases. We also include objects from the literature to obtain a sample of 31 galaxies with spatially resolved multiphase outflow information. We find that the ionized phase of the outflows has on average an electron density three times higher than the disc (ne,disc ∼ 145 cm−3 versus ne,outflow ∼ 500 cm−3), suggesting that cloud compression in the outflow is more important than cloud dissipation. We find that the difference in extinction between outflow and disc correlates with the outflow gas mass. Together with the analysis of the outflow velocities, this suggests that at least some of the outflows are associated with the ejection of dusty clouds from the disc. This may support models where radiation pressure on dust contributes to driving galactic outflows. The presence of dust in outflows is relevant for potential formation of molecules inside them. We combine our data with millimetre data to investigate the molecular phase. We find that the molecular phase accounts for more than 60 ${{\ \rm per\ cent}}$ of the total mass outflow rate in most objects and this fraction is higher in active galactic nuclei (AGN)-dominated systems. The neutral atomic phase contributes of the order of 10 ${{\ \rm per\ cent}}$, while the ionized phase is negligible. The ionized-to-molecular mass outflow rate declines slightly with AGN luminosity, although with a large scatter.
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Mao, Junjie. "Density diagnostics of photoionized outflows in active galactic nuclei." Proceedings of the International Astronomical Union 15, S350 (2019): 274–77. http://dx.doi.org/10.1017/s1743921319007750.
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AbstractPhotoionized outflows in active galactic nuclei (AGNs) are thought to influence their circumnuclear and host galactic environment. However, the distance of the outflow with respect to the black hole is poorly constrained, which limits our understanding of the kinetic power by the outflow. Therefore, the impact of AGN outflows on their host galaxies is uncertain. If the density of the outflow is known, its distance can be derived. Density measurement via variability studies and density sensitive lines have been used, albeit not very effective in the X-ray band. Good measurements are rather demanding or challenging for the current generation of (grating) spectrometers. The next generation of spectrometers will certainly provide data with better quality and large quantity, leading to tight constraints on the location and the kinetic power of AGN outflows. This contribution summarizes the state-of-the-art in this field.
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Ishibashi, W., A. C. Fabian, and N. Arakawa. "AGN-driven galactic outflows: comparing models to observations." Monthly Notices of the Royal Astronomical Society 502, no. 3 (2021): 3638–45. http://dx.doi.org/10.1093/mnras/stab266.
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ABSTRACT The actual mechanism(s) powering galactic outflows in active galactic nuclei (AGNs) is still a matter of debate. At least two physical models have been considered in the literature: wind shocks and radiation pressure on dust. Here, we provide a first quantitative comparison of the AGN radiative feedback scenario with observations of galactic outflows. We directly compare our radiation pressure-driven shell models with the observational data from the most recent compilation of molecular outflows on galactic scales. We show that the observed dynamics and energetics of galactic outflows can be reproduced by AGN radiative feedback, with the inclusion of radiation trapping and/or luminosity evolution. The predicted scalings of the outflow energetics with AGN luminosity can also quantitatively account for the observational scaling relations. Furthermore, sources with both ultrafast and molecular outflow detections are found to be located in the ‘forbidden’ region of the NH–λ plane. Overall, an encouraging agreement is obtained over a wide range of AGN and host galaxy parameters. We discuss our results in the context of recent observational findings and numerical simulations. In conclusion, AGN radiative feedback is a promising mechanism for driving galactic outflows that should be considered, alongside wind feedback, in the interpretation of future observational data.
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Tokuda, Kazuki, Sarolta Zahorecz, Yuri Kunitoshi, et al. "The First Detection of a Protostellar CO Outflow in the Small Magellanic Cloud with ALMA." Astrophysical Journal Letters 936, no. 1 (2022): L6. http://dx.doi.org/10.3847/2041-8213/ac81c1.
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Abstract Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in the Small Magellanic Cloud with 0.2 Z ⊙, using Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.1 pc toward the massive protostar Y246. The bipolar outflow is nicely illustrated by high-velocity wings of CO(3–2) emission at ≳15 km s−1. The evaluated properties of the outflow (momentum, mechanical force, etc.) are consistent with those of the Galactic counterparts. Our results suggest that the molecular outflows, i.e., the guidepost of the disk accretion at the small scale, might be universally associated with protostars across the metallicity range of ∼0.2–1 Z ⊙.
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Mitchell, Peter D., Joop Schaye, Richard G. Bower, and Robert A. Crain. "Galactic outflow rates in the EAGLE simulations." Monthly Notices of the Royal Astronomical Society 494, no. 3 (2020): 3971–97. http://dx.doi.org/10.1093/mnras/staa938.
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ABSTRACT We present measurements of galactic outflow rates from the eagle suite of cosmological simulations. We find that gas is removed from the interstellar medium (ISM) of central galaxies with a dimensionless mass loading factor that scales approximately with circular velocity as $V_{\mathrm{c}}^{-3/2}$ in the low-mass regime where stellar feedback dominates. Feedback from active galactic nuclei causes an upturn in the mass loading for halo masses ${\gt}10^{12} \, \mathrm{M_\odot }$. We find that more gas outflows through the halo virial radius than is removed from the ISM of galaxies, particularly at low redshifts, implying substantial mass loading within the circumgalactic medium. Outflow velocities span a wide range at a given halo mass/redshift, and on average increase positively with redshift and halo mass up to $M_{200} \sim 10^{12} \, \mathrm{M_\odot }$. Outflows exhibit a bimodal flow pattern on circumgalactic scales, aligned with the galactic minor axis. We present a number of like-for-like comparisons to outflow rates from other recent cosmological hydrodynamical simulations, and show that comparing the propagation of galactic winds as a function of radius reveals substantial discrepancies between different models. Relative to some other simulations, eagle favours a scenario for stellar feedback where agreement with the galaxy stellar mass function is achieved by removing smaller amounts of gas from the ISM, but with galactic winds that then propagate and entrain ambient gas out to larger radii.
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Takasao, Shinsuke, Yuri Shuto, and Keiichi Wada. "Spontaneous Formation of Outflows Powered by Rotating Magnetized Accretion Flows in a Galactic Center." Astrophysical Journal 926, no. 1 (2022): 50. http://dx.doi.org/10.3847/1538-4357/ac38a8.
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Abstract We investigate how magnetically driven outflows are powered by a rotating, weakly magnetized accretion flow onto a supermassive black hole using axisymmetric magnetohydrodynamic simulations. Our proposed model focuses on the accretion dynamics on an intermediate scale between the Schwarzschild radius and the galactic scale, which is ∼1–100 pc. We demonstrate that a rotating disk formed on a parsec-scale acquires poloidal magnetic fields via accretion, and this produces an asymmetric bipolar outflow at some point. The formation of the outflow was found to follow the growth of strongly magnetized regions around disk surfaces (magnetic bubbles). The bipolar outflow grew continuously inside the expanding bubbles. We theoretically derived the growth condition of the magnetic bubbles for our model that corresponds to a necessary condition for outflow growth. We found that the north–south asymmetrical structure of the bipolar outflow originates from the complex motions excited by accreting flows around the outer edge of the disk. The bipolar outflow comprises multiple mini-outflows and downflows (failed outflows). The mini-outflows emanate from the magnetic concentrations (magnetic patches). The magnetic patches exhibit inward drifting motions, thereby making the outflows unsteady. We demonstrate that the inward drift can be modeled using a simple magnetic patch model that considers magnetic angular momentum extraction. This study could be helpful for understanding how asymmetric and nonsteady outflows with complex substructures are produced around supermassive black holes without the help of strong radiation from accretion disks or entrainment by radio jets such as molecular outflows in radio-quiet active galactic nuclei, e.g., NGC 1377.
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Barai, Paramita. "How to Simulate Galactic Outflows?" Proceedings of the International Astronomical Union 10, S309 (2014): 300–301. http://dx.doi.org/10.1017/s1743921314009971.
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AbstractA challenge in cosmological simulations is to formulate a physical model of star-formation (SF) and supernovae (SN) feedback which produces galactic outflows like that widely observed. In several models an outflow velocity (vout) and mass loading factor (η) are input to the sub-resolution recipe. We present results from our MUPPI model, which uses local properties of gas, and is able to develop galactic outflows whose properties correlate with global galaxy properties, consistent with observations; demonstrating a significant improvement in such work.
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Avery, Charlotte R., Stijn Wuyts, Natascha M. Förster Schreiber, et al. "Incidence, scaling relations and physical conditions of ionized gas outflows in MaNGA." Monthly Notices of the Royal Astronomical Society 503, no. 4 (2021): 5134–60. http://dx.doi.org/10.1093/mnras/stab780.
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ABSTRACT In this work, we investigate the strength and impact of ionized gas outflows within z ∼ 0.04 MaNGA galaxies. We find evidence for outflows in 322 galaxies ($12{{\ \rm per\ cent}}$ of the analysed line-emitting sample), 185 of which show evidence for hosting an active galactic nucleus (AGN). Most outflows are centrally concentrated with a spatial extent that scales sublinearly with Re. The incidence of outflows is enhanced at higher masses, central surface densities, and deeper gravitational potentials, as well as at higher star formation rate (SFR) and AGN luminosity. We quantify strong correlations between mass outflow rates and the mechanical drivers of the outflow of the form $\dot{M}_{\rm out} \propto \rm SFR^{0.97}$ and $\dot{M}_{\rm out} \propto L_{\rm AGN}^{0.55}$. We derive a master scaling relation describing the mass outflow rate of ionized gas as a function of M⋆, SFR, Re, and LAGN. Most of the observed winds are anticipated to act as galactic fountains, with the fraction of galaxies with escaping winds increasing with decreasing potential well depth. We further investigate the physical properties of the outflowing gas finding evidence for enhanced attenuation in the outflow, possibly due to metal-enriched winds, and higher excitation compared to the gas in the galactic disc. Given that the majority of previous studies have focused on more extreme systems with higher SFRs and/or more luminous AGN, our study provides a unique view of the non-gravitational gaseous motions within ‘typical’ galaxies in the low-redshift Universe, where low-luminosity AGN and star formation contribute jointly to the observed outflow phenomenology.
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Xu, Xinfeng, Timothy Heckman, Alaina Henry, et al. "CLASSY III. The Properties of Starburst-driven Warm Ionized Outflows*." Astrophysical Journal 933, no. 2 (2022): 222. http://dx.doi.org/10.3847/1538-4357/ac6d56.
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Abstract We report the results of analyses of galactic outflows in a sample of 45 low-redshift starburst galaxies in the COS Legacy Archive Spectroscopic SurveY (CLASSY), augmented by five additional similar starbursts with Cosmic Origins Spectrograph (COS) data. The outflows are traced by blueshifted absorption lines of metals spanning a wide range of ionization potential. The high quality and broad spectral coverage of CLASSY data enable us to disentangle the absorption due to the static interstellar medium (ISM) from that due to outflows. We further use different line multiplets and doublets to determine the covering fraction, column density, and ionization state as a function of velocity for each outflow. We measure the outflow’s mean velocity and velocity width, and find that both correlate in a highly significant way with the star formation rate, galaxy mass, and circular velocity over ranges of four orders of magnitude for the first two properties. We also estimate outflow rates of metals, mass, momentum, and kinetic energy. We find that, at most, only about 20% of silicon created and ejected by supernovae in the starburst is carried out in the warm phase we observe. The outflows’ mass-loading factor increases steeply and inversely with both circular and outflow velocity (log–log slope ∼−1.6), and reaches ∼10 for dwarf galaxies. We find that the outflows typically carry about 10%–100% of the momentum injected by massive stars and about 1%–20% of the kinetic energy. We show that these results place interesting constraints on, and new insights into, models and simulations of galactic winds.
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Skretas, I. M., and L. E. Kristensen. "Connecting Galactic and extragalactic outflows: From the Cygnus-X cluster to active galaxies." Astronomy & Astrophysics 660 (April 2022): A39. http://dx.doi.org/10.1051/0004-6361/202141944.
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Context. Molecular outflows are commonly detected originating from both protostellar and extragalactic sources. Separate studies of low-mass, isolated high-mass, and extragalactic sources reveal scaling relations connecting the force carried by an outflow and the properties of the source that drives it, as for example the mass and luminosity. Aims. The aim of this work is twofold: first, to examine the effects, if any, of clustered star formation on the protostellar outflows and their scaling relations and, second, to explore the possibility that outflows varying in scale and energetics by many orders of magnitude are consistent with being launched by the same physical processes. Methods. To that end, high-angular resolution CO J = 3–2 observations were used of ten high-mass protostars in the Cygnus-X molecular cloud, obtained at the SubMilliMeter Array as part of the Protostellar Interferometric Line Survey of Cygnus-X (PILS-Cygnus). From these data, the outflow force, that is the momentum ejection rate, was measured. In addition, an extended sample of protostellar and extragalactic outflow-force measurements was assembled from existing literature to allow for a direct comparison of the scaling relations of the two types of outflows. Results. Molecular outflows were detected originating from all ten sources of the PILS-Cygnus survey, and their outflow forces are found to be in close agreement with measurements from the literature. In addition, the comparison of the protostellar and extragalactic sources reveals, with 95% confidence, that Class 0 protostars and extragalactic sources follow the same outflow force–bolometric luminosity correlation. Conclusions. The close agreement between the Cygnus-X sources and sources of similar envelope mass and bolometric luminosity suggests that clustered star formation has no significant effect on protostellar outflows. We find a strong indication that protostellar and extragalactic outflows are consistent with having a similar launch mechanism. The existence of such a mechanism would enable the development of a single universal outflow launch model, although more observations are required in order to verify this connection.
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Jana, Ranita, Siddhartha Gupta, and Biman B. Nath. "Role of cosmic rays in the early stages of galactic outflows." Monthly Notices of the Royal Astronomical Society 497, no. 3 (2020): 2623–40. http://dx.doi.org/10.1093/mnras/staa2025.
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ABSTRACT Using an idealized set-up, we investigate the dynamical role of cosmic rays (CRs) in the early stages of galactic outflows for galaxies of halo masses 108, 1011, and 1012 M⊙. The outflow is launched from a central region in the galactic disc where we consider three different constant star formation rates (0.1, 1, and 10 $\mathrm{M}_\odot \, \mathrm{yr}^{-1}$) over a dynamical time-scale of 50 Myr. We determine the temperature distribution of the gas and find that CRs can reduce the temperature of the shocked gas, which is consistent with previous results. However, we show that CRs do not have any noticeable effect on the mass loading by the outflow. We find that CRs can reduce the size of the outflow, which contradicts previous claims of efficient dynamical impact of CRs; however, it is consistent with earlier theoretical models of CR-driven blastwave as well as stellar wind. We discuss the dependence of our results on CR injection prescriptions and compare them with earlier studies. We conclude that in the early stages of galactic outflows the dynamical role of CRs is not important.
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Reichardt Chu, Bronwyn, Deanne B. Fisher, Alberto D. Bolatto, et al. "DUVET: Spatially Resolved Observations of Star Formation Regulation via Galactic Outflows in a Starbursting Disk Galaxy." Astrophysical Journal 941, no. 2 (2022): 163. http://dx.doi.org/10.3847/1538-4357/aca1bd.
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Abstract We compare 500 pc scale, resolved observations of ionized and molecular gas for the z ∼ 0.02 starbursting disk galaxy IRAS08339+6517, using measurements from KCWI and NOEMA. We explore the relationship of the star-formation-driven ionized gas outflows with colocated galaxy properties. We find a roughly linear relationship between the outflow mass flux ( Σ ̇ out ) and star formation rate surface density (ΣSFR), Σ ̇ out ∝ Σ SFR 1.06 ± 0.10 , and a strong correlation between Σ ̇ out and the gas depletion time, such that Σ ̇ out ∝ t dep − 1.1 ± 0.06 . Moreover, we find these outflows are so-called breakout outflows, according to the relationship between the gas fraction and disk kinematics. Assuming that ionized outflow mass scales with total outflow mass, our observations suggest that the regions of highest ΣSFR in IRAS08 are removing more gas via the outflow than through the conversion of gas into stars. Our results are consistent with a picture in which the outflow limits the ability of a region of a disk to maintain short depletion times. Our results underline the need for resolved observations of outflows in more galaxies.
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Zubovas, Kastytis, and Emanuele Nardini. "Intermittent AGN episodes drive outflows with a large spread of observable loading factors." Monthly Notices of the Royal Astronomical Society 498, no. 3 (2020): 3633–47. http://dx.doi.org/10.1093/mnras/staa2652.
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ABSTRACT The properties of large-scale galactic outflows, such as their kinetic energy and momentum rates, correlate with the luminosity of the active galactic nucleus (AGN). This is well explained by the wind-driven outflow model, where a fraction of the AGN luminosity drives the outflow. However, significant departures from these correlations have been observed in a number of galaxies. This may happen because AGN luminosity varies on a much shorter time-scale (∼104–105 yr) than outflow properties do (∼106 yr). We investigate the effect of AGN luminosity variations on outflow properties using 1D numerical simulations. This effect can explain the very weak outflow in PDS 456: if its nucleus is currently much brighter than the long-term average luminosity, the outflow has not had time to react to this luminosity change. Conversely, the outflow in Mrk 231 is consistent with being driven by an almost continuous AGN, while IRAS F11119+3257 represents an intermediate case between the two. Considering a population of AGN, we find that very low momentum loading factors $\dot{p}_{\rm out} \lt L_{\rm AGN}/c$ should be seen in a significant fraction of objects – up to $15{{\ \rm per\ cent}}$ depending on the properties of AGN variability and galaxy gas fraction. The predicted distribution of loading factors is consistent with the available observational data. We discuss how this model might help constrain the duty cycles of AGN during the period of outflow inflation, implications for multiphase, and spatially distinct outflows, and suggest ways of improving AGN prescriptions in numerical simulations.
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Perrotta, Serena, Alison L. Coil, David S. N. Rupke, et al. "Kinematics, Structure, and Mass Outflow Rates of Extreme Starburst Galactic Outflows." Astrophysical Journal 949, no. 1 (2023): 9. http://dx.doi.org/10.3847/1538-4357/acc660.
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Abstract We present results on the properties of extreme gas outflows in massive (M * ∼ 1011 M ⊙), compact, starburst (star formation rate, SFR∼ 200 M ⊙ yr−1) galaxies at z = 0.4–0.7 with very high star formation surface densities (ΣSFR ∼ 2000 M ⊙ yr−1 kpc−2). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies, we identify outflows with maximum velocities of 820–2860 km s−1. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T ∼ 104 K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies’ star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong Mg ii absorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of ∼50–2200 M ⊙ yr−1, assuming a fiducial outflow size of 5 kpc, and mass loading factors of η ∼ 5 for most of the sample. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution.
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Chisholm, John, Christy A. Tremonti, Claus Leitherer, and Yanmei Chen. "The mass and momentum outflow rates of photoionized galactic outflows." Monthly Notices of the Royal Astronomical Society 469, no. 4 (2017): 4831–49. http://dx.doi.org/10.1093/mnras/stx1164.
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Husemann, B., J. Scharwächter, T. A. Davis, et al. "The Close AGN Reference Survey (CARS)." Astronomy & Astrophysics 627 (July 2019): A53. http://dx.doi.org/10.1051/0004-6361/201935283.
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Context. Galaxy-wide outflows driven by star formation and/or an active galactic nucleus (AGN) are thought to play a crucial rule in the evolution of galaxies and the metal enrichment of the inter-galactic medium. Direct measurements of these processes are still scarce and new observations are needed to reveal the nature of outflows in the majority of the galaxy population. Aims. We combine extensive, spatially-resolved, multi-wavelength observations, taken as part of the Close AGN Reference Survey (CARS), for the edge-on disc galaxy HE 1353−1917 in order to characterise the impact of the AGN on its host galaxy via outflows and radiation. Methods. Multi-color broad-band photometry was combined with spatially-resolved optical, near-infrared (NIR) and sub-mm and radio observations taken with the Multi-Unit Spectroscopy Explorer (MUSE), the Near-infrared Integral Field Spectrometer (NIFS), the Atacama Large Millimeter Array (ALMA), and the Karl G. Jansky Very Large Array (VLA) to map the physical properties and kinematics of the multi-phase interstellar medium. Results. We detect a biconical extended narrow-line region ionised by the luminous AGN orientated nearly parallel to the galaxy disc, extending out to at least 25 kpc. The extra-planar gas originates from galactic fountains initiated by star formation processes in the disc, rather than an AGN outflow, as shown by the kinematics and the metallicity of the gas. Nevertheless, a fast, multi-phase, AGN-driven outflow with speeds up to 1000 km s−1 is detected close to the nucleus at 1 kpc distance. A radio jet, in connection with the AGN radiation field, is likely responsible for driving the outflow as confirmed by the energetics and the spatial alignment of the jet and multi-phase outflow. Evidence for negative AGN feedback suppressing the star formation rate (SFR) is mild and restricted to the central kpc. But while any SFR suppression must have happened recently, the outflow has the potential to greatly impact the future evolution of the galaxy disc due to its geometrical orientation. Conclusions.. Our observations reveal that low-power radio jets can play a major role in driving fast, multi-phase, galaxy-scale outflows even in radio-quiet AGN. Since the outflow energetics for HE 1353−1917 are consistent with literature, scaling relation of AGN-driven outflows the contribution of radio jets as the driving mechanisms still needs to be systematically explored.
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Venturi, Giacomo, and Alessandro Marconi. "The physical properties and impact of AGN outflows from high to low redshift." Proceedings of the International Astronomical Union 15, S359 (2020): 212–20. http://dx.doi.org/10.1017/s1743921320002203.
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AbstractFeedback from active galactic nuclei (AGN) on their host galaxies, in the form of gas outflows capable of quenching star formation, is considered a major player in galaxy evolution. However, clear observational evidence of such major impact is still missing; uncertainties in measuring outflow properties might be partly responsible because of their critical role in comparisons with models and in constraining the impact of outflows on galaxies. Here we briefly review the challenges in measuring outflow physical properties and present an overview of outflow studies from high to low redshift. Finally, we present highlights from our MAGNUM survey of nearby AGN with VLT/MUSE, where the high intrinsic spatial resolution (down to ˜ 10 pc) allows us to accurately measure the physical and kinematic properties of ionised gas outflows.
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Steinwandel, Ulrich P., Klaus Dolag, Harald Lesch, and Andreas Burkert. "Driving Galactic Outflows with Magnetic Fields at Low and High Redshift." Astrophysical Journal 924, no. 1 (2022): 26. http://dx.doi.org/10.3847/1538-4357/ac2ffd.
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Abstract Although galactic outflows play a key role in our understanding of the evolution of galaxies, the exact mechanism by which galactic outflows are driven is still far from being understood and, therefore, our understanding of associated feedback mechanisms that control the evolution of galaxies is still plagued by many enigmas. In this work, we present a simple toy model that can provide insight on how non-axisymmetric instabilities in galaxies (bars, spiral arms, warps) can lead to local exponential magnetic field growth by radial flows beyond the equipartition value by at least two orders of magnitude on a timescale of a few 100 Myr. Our predictions show that the process can lead to galactic outflows in barred spiral galaxies with a mass-loading factor η ≈ 0.1, in agreement with our numerical simulations. Moreover, our outflow mechanism could contribute to an understanding of the large fraction of barred spiral galaxies that show signs of galactic outflows in the chang-es survey. Extending our model shows the importance of such processes in high-redshift galaxies by assuming equipartition between magnetic energy and turbulent energy. Simple estimates for the star formation rate in our model together with cross correlated masses from the star-forming main sequence at redshifts z ∼ 2 allow us to estimate the outflow rate and mass-loading factors by non-axisymmetric instabilities and a subsequent radial inflow dynamo, giving mass-loading factors of η ≈ 0.1 for galaxies in the range of M ⋆ = 109–1012 M ⊙, in good agreement with recent results of sinfoni and kmos 3D.
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Roos, Orianne, and Frédéric Bournaud. "Ultra-Fast Outflows in Typical Redshift 2 Star-Forming Galaxies." Proceedings of the International Astronomical Union 11, S319 (2015): 41–44. http://dx.doi.org/10.1017/s1743921315010340.
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AbstractGalactic outflows are observed in star-forming galaxies up to high redshift. Still, their physical origins are not well understood, and most simulations fail to reproduce all observed parameters from first principles. With the POGO simulations (Physical Origins of Galactic Outflows), we model AGN and stellar feedback (FB) based on physical assumptions, and investigate their impact on the outflow parameters and on the host-galaxy at very high resolution (1.5 pc). Here, we show that AGN and stellar FB couple non-linearly, and that the mass loading of the resulting outflow highly depends on the mass of the host.
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Roberts-Borsani, G. W. "Observational constraints on the multiphase nature of outflows using large spectroscopic surveys at z ∼ 0." Monthly Notices of the Royal Astronomical Society 494, no. 3 (2020): 4266–78. http://dx.doi.org/10.1093/mnras/staa1006.
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ABSTRACT Mass outflow rates and loading factors are typically used to infer the quenching potential of galactic-scale outflows. However, these generally rely on observations of a single gas phase that can severely underestimate the total ejected gas mass. To address this, we use observations of high mass (≥1010 M⊙), normal star-forming galaxies at z ∼ 0 from the MaNGA, xCOLD GASS, xGASS, and ALFALFA surveys and a stacking of Na d, Hα, CO(1–0), and H i 21 cm tracers with the aim of placing constraints on an average, total mass outflow rate, and loading factor. We find detections of outflows in both neutral and ionized gas tracers, with no detections in stacks of molecular or atomic gas emission. Modelling of the outflow components reveals velocities of |vNa d| = 131 km s−1 and |vHα| = 439 km s−1 and outflow rates of $\dot{M}_{\rm {Na\,\small{D}}}$ = 7.55 M⊙ yr−1 and $\dot{M}_{\text{H}\alpha }$ = 0.10 M⊙ yr−1 for neutral and ionized gas, respectively. Assuming a molecular/atomic outflow velocity of 200 km s−1, we derive upper limits of $\dot{M}_{\text{CO}}\lt 19.43$ M⊙ yr−1 and $\dot{M}_{\rm {H\,\small {I}}}\lt $ 26.72 M⊙ yr−1 for the molecular and atomic gas, respectively. Combining the detections and upper limits, we find average total outflow rates of $\dot{M}_{\text{tot}}\lesssim$27 M⊙ yr−1 and a loading factor of ηtot ≲ 6.39, with molecular gas likely contributing ≲72 per cent of the total mass outflow rate, and neutral and ionized gas contributing ∼28 and <1 per cent, respectively. Our results suggest that, to first order, a degree of quenching via ejective feedback could occur in normal galaxies when considering all gas phases, even in the absence of an active galactic nucleus.
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Maiolino, R., H. R. Russell, A. C. Fabian, et al. "Star formation inside a galactic outflow." Nature 544, no. 7649 (2017): 202–6. http://dx.doi.org/10.1038/nature21677.
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Lochhaas, Cassandra, Todd A. Thompson, and Evan E. Schneider. "The characteristic momentum of radiatively cooling energy-driven galactic winds." Monthly Notices of the Royal Astronomical Society 504, no. 3 (2021): 3412–23. http://dx.doi.org/10.1093/mnras/stab1101.
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ABSTRACT Energy injection by supernovae may drive hot supersonic galactic winds in rapidly star-forming galaxies, driving metal-enriched gas into the circumgalactic medium and potentially accelerating cool gas. If sufficiently mass-loaded, such flows become radiative within the wind-driving region, reducing the overall mass outflow rate from the host galaxy. We show that this sets a maximum on the total outflow momentum for hot energy-driven winds. For a spherical wind of Solar metallicity driven by continuous star formation, $\dot{p}_\mathrm{max} \simeq 1.9\times 10^4\ M_\odot \ \mathrm{yr}^{-1}\ \mathrm{km\ s}^{-1}(\alpha /0.9)^{0.86}\left[R_\star /(300\ \mathrm{pc})\right]^{0.14}[\dot{M}_\star /(20\ M_\odot \ \mathrm{yr}^{-1})]^{0.86},$ where α is the fraction of supernova energy that thermalizes the wind, and $\dot{M}_\star$ and R⋆ are the star formation rate and radius of the wind-driving region. This maximum momentum for hot winds can also apply to cool, ionized outflows that are typically observed in starburst galaxies, if the hot wind undergoes bulk radiative cooling or if the hot wind transfers mass and momentum to cool clouds within the flow. We show that requiring the hot wind to undergo single-phase cooling on large scales sets a minimum on the total outflow momentum rate. These maximum and minimum outflow momenta have similar values, setting a characteristic momentum rate of hot galactic winds that can become radiative on large scales. We find that most observations of photoionized outflow wind momentum fall below the theoretical maximum and thus may be signatures of cooling hot flows. On the other hand, many systems fall below the minimum momentum required for bulk cooling, indicating that perhaps the cool material observed has instead been entrained in or mixed with the hot flow.
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Deng, Hui-Hong, and De-Fu Bu. "Hot Accretion Flow in Two-Dimensional Spherical Coordinates: Considering Pressure Anisotropy and Magnetic Field." Universe 5, no. 9 (2019): 197. http://dx.doi.org/10.3390/universe5090197.
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For systems with extremely low accretion rate, such as Galactic Center Sgr A* and M87 galaxy, the ion collisional mean free path can be considerably larger than its Larmor radius. In this case, the gas pressure is anisotropic to magnetic field lines. In this paper, we pay attention to how the properties of outflow change with the strength of anisotropic pressure and the magnetic field. We use an anisotropic viscosity to model the anisotropic pressure. We solve the two-dimensional magnetohydrodynamic (MHD) equations in spherical coordinates and assume that the accretion flow is radially self-similar. We find that the work done by anisotropic pressure can heat the accretion flow. The gas temperature is heightened when anisotropic stress is included. The outflow velocity increases with the enhancement of strength of the anisotropic force. The Bernoulli parameter does not change much when anisotropic pressure is involved. However, we find that the energy flux of outflow can be increased by a factor of 20 in the presence of anisotropic stress. We find strong wind (the mass outflow is about 70% of the mass inflow rate) is formed when a relatively strong magnetic field is present. Outflows from an active galactic nucleus can interact with gas in its host galaxies. Our result predicts that outflow feedback effects can be enhanced significantly when anisotropic pressure and a relatively powerful magnetic field is considered.
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Dorfi, Ernst A., and Daniel Steiner. "High-energy particles from SN-explosions near the Galactic center." Proceedings of the International Astronomical Union 9, S303 (2013): 454–55. http://dx.doi.org/10.1017/s1743921314001124.
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AbstractSeveral supernovae exploding in a compact cluster of massive stars generate a galactic outflow with embedded shock waves. Based on numerical simulations for an expanding superbubble above the Galactic center we find that these individual waves generated by the repeated SN-explosions, interact with each other and finally coalesce into a single strong shock at a distance of 5 kpc above the Galactic plane at about 5 ċ 106 years after outbreak. The resulting shock with a Mach number M ≃ 10 propagates up to 100 kpc in less than 108 years. The time-dependent mass an energy loss out of the superbubble affects the further evolution of the outflow. In such long lasting shock waves energetic particles can be accelerated above the knee of 1015 eV already near the galactic plane by a first-order Fermi-mechanism. The additional pressure gradients from such cosmic rays lead to further accelerations of the galactic outflow since these ultra-relativistic particles suffer less from adiabatic losses than the thermal gas.
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Lutz, D., E. Sturm, A. Janssen, et al. "Molecular outflows in local galaxies: Method comparison and a role of intermittent AGN driving." Astronomy & Astrophysics 633 (January 2020): A134. http://dx.doi.org/10.1051/0004-6361/201936803.
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We report new detections and limits from a NOEMA and ALMA CO(1-0) search for molecular outflows in 13 local galaxies with high far-infrared surface brightness, and combine these with local universe CO outflow results from the literature. The CO line ratios and spatial outflow structure of our targets provide some constraints on the conversion steps from observables to physical quantities such as molecular mass outflow rates. Where available, ratios between outflow emission in higher J CO transitions and in CO(1-0) are typically consistent with excitation Ri1 ≲ 1. However, for IRAS 13120−5453, R31 = 2.10 ± 0.29 indicates optically thin CO in the outflow. Like much of the outflow literature, we use αCO(1 − 0) = 0.8, and we present arguments for using C = 1 in deriving molecular mass outflow rates Ṁout = CMoutvout/Rout. We compare the two main methods for molecular outflow detection: CO millimeter interferometry and Herschel OH-based spectroscopic outflow searches. For 26 sources studied with both methods, we find an 80% agreement in detecting vout ≳ 150 km s−1 outflows, and non-matches can be plausibly ascribed to outflow geometry and signal-to-noise ratio. For a published sample of 12 bright ultraluminous infrared galaxies with detailed OH-based outflow modeling, CO outflows are detected in all but one. Outflow masses, velocities, and sizes for these 11 sources agree well between the two methods, and modest remaining differences may relate to the different but overlapping regions sampled by CO emission and OH absorption. Outflow properties correlate better with active galactic nucleus (AGN) luminosity and with bolometric luminosity than with far-infrared surface brightness. The most massive outflows are found for systems with current AGN activity, but significant outflows in nonAGN systems must relate to star formation or to AGN activity in the recent past. We report scaling relations for the increase of outflow mass, rate, momentum rate, and kinetic power with bolometric luminosity. Short flow times of ∼106 yr and some sources with resolved multiple outflow episodes support a role of intermittent driving, likely by AGNs.
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Igarashi, Asuka, Masao Mori, and Shin-ya Nitta. "Transonic galactic outflows in a dark matter halo with a central black hole." Proceedings of the International Astronomical Union 11, A29B (2015): 741. http://dx.doi.org/10.1017/s1743921316006645.
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AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming an isothermal, steady and spherically symmetric state. Transonic solutions of galactic outflows are classified according to their topological features. As result, we find two types of transonic solutions distinguished by a magnitude relationship between the gravity of DMH and that of SMBH. The loci of transonic points for two types are different; one transonic point is formed at a central region (< 0.01kpc) and another is at a very distant region (> 100kpc). Also, mass fluxes and outflow velocities are different for two solutions. Thus, these solutions may differently influence the evolution of galaxies and the release of metals into the intergalactic space.Furthermore, we apply our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as the trace of galactic outflows while the star-formation rate is low, and the observed gas density distribution is similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a solution that this galaxy has a slowly accelerating outflow; the transonic point forms in a very distant region (~ 120 kpc) and the wide subsonic region spreads across the stellar distribution. Thus, the gas density distribution in the observed region is similar to the hydrostatic state. Such slowly accelerating outflows are different from high-velocity outflows conventionally studied (Igarashi et al. 2014).However, this isothermal model requires an unrealistically large mass flux. Then, we apply the polytropic model to this galaxy incorporating mass flux supplied by stellar components. We find that it can reproduce the observed gas density and the temperature distributions with the realistic mass flux. Thus, our polytropic model successfully demonstrates the existence of the slowly accelerating outflow in the Sombrero galaxy (Igarashi et al. 2015).
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Hogarth, L. M., A. Saintonge, L. Cortese, et al. "Centrally concentrated molecular gas driving galactic-scale ionized gas outflows in star-forming galaxies." Monthly Notices of the Royal Astronomical Society 500, no. 3 (2020): 3802–20. http://dx.doi.org/10.1093/mnras/staa3512.
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ABSTRACT We perform a joint analysis of high spatial resolution molecular gas and star-formation rate (SFR) maps in main-sequence star-forming galaxies experiencing galactic-scale outflows of ionized gas. Our aim is to understand the mechanism that determines which galaxies are able to launch these intense winds. We observed CO(1→0) at 1-arcsec resolution with ALMA in 16 edge-on galaxies, which also have 2-arcsec spatial-resolution optical integral field observations from the SAMI Galaxy Survey. Half the galaxies in the sample were previously identified as harbouring intense and large-scale outflows of ionized gas (‘outflow types’) and the rest serve as control galaxies. The data set is complemented by integrated CO(1→0) observations from the IRAM 30-m telescope to probe the total molecular gas reservoirs. We find that the galaxies powering outflows do not possess significantly different global gas fractions or star-formation efficiencies when compared with a control sample. However, the ALMA maps reveal that the molecular gas in the outflow-type galaxies is distributed more centrally than in the control galaxies. For our outflow-type objects, molecular gas and star-formation are largely confined within their inner effective radius (reff), whereas in the control sample, the distribution is more diffuse, extending far beyond reff. We infer that outflows in normal star-forming galaxies may be caused by dynamical mechanisms that drive molecular gas into their central regions, which can result in locally enhanced gas surface density and star-formation.
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Yaqoob, Tahir. "Mass outflow constraints in active nuclei and quasars from X-ray spectroscopy." Proceedings of the International Astronomical Union 3, S245 (2007): 263–68. http://dx.doi.org/10.1017/s1743921308017882.
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AbstractAbsorption in the X-ray spectra of active galactic nuclei from outflowing gas can be modeled to yield critical physical information on the outflows. The outflow rate of mass ejected back into the ISM of the host galaxy and the resulting feedback could potentially have an impact on evolution. We give a brief overview of the current observational constraints on the outflows that should be taken into account by models of evolution and feedback.
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Hamann, Fred, Nissem Kanekar, Jason X. Prochaska, et al. "New Results on Quasar Outflows." Proceedings of the International Astronomical Union 5, S267 (2009): 399. http://dx.doi.org/10.1017/s1743921310006836.
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AbstractAccretion disk outflows are an important part of the quasar phenomenon. They might play a major role in distributing metals to the galactic surroundings, halting growth of the central black hole and providing kinetic energy “feedback” to regulate star formation in the host galaxies. Some models of galaxy evolution indicate that feedback requires kinetic energy luminosities, LK, that are ~5% of the quasar bolometric; LK/L = Ṁwν2/2η:Ṁaccc2 ~ 5% is possible if Ṁw ~ Ṁacc (with ν~ 0.1c, and η ~ 0.1). Here we describe results from two studies designed to test the theoretical energetics of radiatively driven outflows and derive observational constraints on the outflow geometry and physical properties emphasizing weaker outflow features like NALs and mini-BALs.
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Lopez-Rodriguez, Enrique. "The Magnetic Fields of Starburst Galaxies. I. Identification and Characterization of the Thermal Polarization in the Galactic Disk and Outflow." Astrophysical Journal 953, no. 1 (2023): 113. http://dx.doi.org/10.3847/1538-4357/ace110.
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Abstract Far-infrared polarized emission by means of magnetically aligned dust grains is an excellent tracer of the magnetic fields (B-fields) in the cold phase of the galactic outflows of starburst galaxies. We present a comprehensive study of the B-fields in three nearby (3.5–17.2 Mpc) starbursts (M82, NGC 253, and NGC 2146) at 5 pc–1.5 kpc resolutions using publicly available 53–890 μm imaging polarimetric observations with Stratospheric Observatory for Infrared Astronomy/HAWC+, James Clerk Maxwell Telescope/POL-2, and ALMA. We find that the polarized spectral energy distributions (SEDs) of the full galaxies are dominated by the polarized SEDs of the outflows with dust temperatures of T d , outflow PI ∼ 45 K and an emissive index of β outflow PI ∼ 2.3 . The disks are characterized by low T d , disk PI = [ 24 , 31 ] K and β disk PI ∼ 1 . We show that disk- and outflow-dominated galaxies can be better distinguished by using polarized SEDs instead of total SEDs. We compute the 53–850 μm polarization spectrum of the disk and outflow, and find that dust models of the diffuse ISM can reproduce the fairly constant polarization spectrum of the disk, 〈 P disk〉 = 1.2% ± 0.5%. The dust models of heterogenous clouds and two-temperature components are required to explain the polarization spectrum of the outflow (2%–4% at 53 μm, ∼1% at 850 μm, and a minimum within 89–154 μm). We conclude that the polarized dust grains in the outflow arise from a dust population with higher dust temperature and emissivities than those from the total flux. The B-fields of the outflows have maximum extensions within 89–214 μm reaching heights of ∼4 kpc, and have flatter polarized fluxes than total fluxes. The extension of the B-field permeating the circumgalactic medium increases as the star formation rate increases.
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Davis, Julie D., Christy A. Tremonti, Cameren N. Swiggum, et al. "Extending the Dynamic Range of Galaxy Outflow Scaling Relations: Massive Compact Galaxies with Extreme Outflows." Astrophysical Journal 951, no. 2 (2023): 105. http://dx.doi.org/10.3847/1538-4357/accbbf.
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Abstract We investigate galactic winds in the HizEA galaxies, a collection of 46 late-stage galaxy mergers at z = 0.4–0.8, with stellar masses of log ( M * / M ⊙ ) = 10.4 – 11.5 , star formation rates (SFRs) of 20–500 M ⊙ yr−1, and ultra-compact (a few 100 pc) central star-forming regions. We measure their gas kinematics using the Mg ii λ λ 2796,2803 absorption lines in optical spectra from MMT, Magellan, and Keck. We find evidence of outflows in 90% of targets, with maximum outflow velocities of 550–3200 km s−1. We combine these data with ten samples from the literature to construct scaling relations for outflow velocity versus SFR, star formation surface density (ΣSFR), M *, and SFR/M *. The HizEA galaxies extend the dynamic range of the scaling relations by a factor of ∼2–4 in outflow velocity and an order of magnitude in SFR and ΣSFR. The ensemble scaling relations exhibit strong correlations between outflow velocity, SFR, SFR/R, and ΣSFR, and weaker correlations with M * and SFR/M *. The HizEA galaxies are mild outliers on the SFR and M * scaling relations, but they connect smoothly with more typical star-forming galaxies on plots of outflow velocity versus SFR/R and ΣSFR. These results provide further evidence that the HizEA galaxies’ exceptional outflow velocities are a consequence of their extreme star formation conditions rather than hidden black hole activity, and they strengthen previous claims that ΣSFR is one of the most important properties governing the velocities of galactic winds.
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Zabl, Johannes, Nicolas F. Bouché, Ilane Schroetter, et al. "MusE GAs FLOw and Wind (MEGAFLOW) IV. A two sightline tomography of a galactic wind." Monthly Notices of the Royal Astronomical Society 492, no. 3 (2019): 4576–88. http://dx.doi.org/10.1093/mnras/stz3607.
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ABSTRACT Galactic outflows are thought to eject baryons back out to the circumgalactic medium. Studies based on metal absorption lines (Mg ii in particular) in the spectra of background quasars indicate that the gas is ejected anisotropically, with galactic winds likely leaving the host in a bi-conical flow perpendicular to the galaxy disc. In this paper, we present a detailed analysis of an outflow from a z = 0.7 ‘green-valley’ galaxy [log (M*/M⊙) = 9.8; $\mbox{SFR}=0.5\, \mathrm{M}_{\odot }\, \mathrm{yr}^{-1}$] probed by two background sources from the MusE GAs FLOw and Wind (MEGAFLOW) survey. Thanks to a fortuitous configuration with a background quasar (SDSSJ1358 + 1145) and a bright background galaxy at z = 1.4, both at impact parameters of $\approx\! 15\, \hbox{kpc}$, we can – for the first time – probe both the receding and approaching components of a putative galactic outflow around a distant galaxy. We measure a significant velocity shift between the Mg ii absorption from the two sightlines ($84\pm 17\, \hbox{km~s$^{-1}$}$), which is consistent with the expectation from our simple fiducial wind model, possibly combined with an extended disc contribution.
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Morganti, Raffaella, Judit Fogasy, Zsolt Paragi, Tom Oosterloo, and Monica Orienti. "Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action." Science 341, no. 6150 (2013): 1082–85. http://dx.doi.org/10.1126/science.1240436.
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The energy released by an active galactic nucleus (AGN) has a strong impact on the surrounding interstellar medium (ISM). This feedback is considered to be the regulating factor for the growth of the central massive black hole and for the rate of star formation in a galaxy. We have located, using very-long-baseline interferometry, the fast outflow of neutral hydrogen in the young, restarted radio-loud AGN 4C12.50. The outflow is located 100 parsec from the nucleus where the radio jet interacts with the ISM, as well as around the associated radio lobe. These observations show that the radio plasma drives the outflow and removes gas from the central regions and that jet-driven outflows can play a relevant role in feedback mechanisms.
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Yusef-Zadeh, F., R. G. Arendt, M. Wardle, and I. Heywood. "The Population of the Galactic Center Filaments: Position Angle Distribution Reveals a Degree-scale Collimated Outflow from Sgr A* along the Galactic Plane." Astrophysical Journal Letters 949, no. 2 (2023): L31. http://dx.doi.org/10.3847/2041-8213/acd54b.
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Abstract We have examined the distribution of the position angle (PA) of the Galactic center filaments with lengths L > 66″ and <66″ as well as their length distribution as a function of PA. We find bimodal PA distributions of the filaments, and long and short populations of radio filaments. Our PA study shows the evidence for a distinct population of short filaments with PA close to the Galactic plane. Mainly thermal, short-radio filaments (<66″) have PAs concentrated close to the Galactic plane within 60° < PA < 120°. Remarkably, the short filament PAs are radial with respect to the Galactic center at l < 0° and extend in the direction toward Sgr A*. On a smaller scale, the prominent Sgr E H ii complex G358.7-0.0 provides a vivid example of the nearly radial distribution of short filaments. The bimodal PA distribution suggests a different origin for two distinct filament populations. We argue that the alignment of the short-filament population results from the ram pressure of a degree-scale outflow from Sgr A* that exceeds the internal filament pressure, and aligns them along the Galactic plane. The ram pressure is estimated to be 2 × 106 cm−3 K at a distance of 300 pc, requiring biconical mass outflow rate 10−4 M ⊙ yr−1 with an opening angle of ∼40°. This outflow aligns not only the magnetized filaments along the Galactic plane but also accelerates thermal material associated with embedded or partially embedded clouds. This places an estimate of ∼6 Myr as the age of the outflow.
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Westmoquette, M. S., L. J. Smith, and J. S. Gallagher. "Studying the galactic outflow in NGC 1569." Monthly Notices of the Royal Astronomical Society 383, no. 3 (2007): 864–78. http://dx.doi.org/10.1111/j.1365-2966.2007.12628.x.
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McClure-Griffiths, N. M., J. A. Green, A. S. Hill, et al. "ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW." Astrophysical Journal 770, no. 1 (2013): L4. http://dx.doi.org/10.1088/2041-8205/770/1/l4.
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Crenshaw, D. M. "ASTROPHYSICS: Mass Outflow in Active Galactic Nuclei." Science 292, no. 5521 (2001): 1500–1501. http://dx.doi.org/10.1126/science.1061145.
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Xu, Xinfeng, Timothy Heckman, Alaina Henry, et al. "CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies." Astrophysical Journal 948, no. 1 (2023): 28. http://dx.doi.org/10.3847/1538-4357/acbf46.
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Abstract Galaxy formation and evolution are regulated by the feedback from galactic winds. Absorption lines provide the most widely available probe of winds. However, since most data only provide information integrated along the line of sight, they do not directly constrain the radial structure of the outflows. In this paper, we present a method to directly measure the gas electron density in outflows (n e ), which in turn yields estimates of outflow cloud properties (e.g., density, volume filling factor, and sizes/masses). We also estimate the distance (r n ) from the starburst at which the observed densities are found. We focus on 22 local star-forming galaxies primarily from the COS Legacy Archive Spectroscopic SurveY (CLASSY). In half of them, we detect absorption lines from fine-structure excited transitions of Si ii (i.e., Si ii*). We determine n e from relative column densities of Si ii and Si ii*, given Si ii* originates from collisional excitation by free electrons. We find that the derived n e correlates well with the galaxy’s star formation rate per unit area. From photoionization models or assuming the outflow is in pressure equilibrium with the wind fluid, we get r n ∼ 1–2r * or ∼5r *, respectively, where r * is the starburst radius. Based on comparisons to theoretical models of multiphase outflows, nearly all of the outflows have cloud sizes large enough for the clouds to survive their interaction with the hot wind fluid. Most of these measurements are the first ever for galactic winds detected in absorption lines and, thus, will provide important constraints for future models of galactic winds.
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Keshet, Noa, and Ehud Behar. "Ionization Distributions in Outflows of Active Galaxies: Universal Trends and Prospect of Future XRISM Observations." Astrophysical Journal 934, no. 2 (2022): 124. http://dx.doi.org/10.3847/1538-4357/ac7c6b.
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Abstract The physics behind the ionization structure of outflows from black holes is yet to be fully understood. Using archival observations with the Chandra/HETG gratings over the past two decades, we measured an absorption measure distribution for a sample of outflows in nine active galactic nuclei (AGNs), namely the dependence of outflow column density, N H, on the ionization parameter, ξ. The slope of log N H versus log ξ is found to be between 0.00 and 0.72. We find an anticorrelation between the log of total column density of the outflow and the log of AGN luminosity, and none with the black hole mass and accretion efficiency. A major improvement in the diagnostics of AGN outflows will potentially occur with the launch of the XRISM/Resolve spectrometer. We study the ability of Resolve to reveal the outflow ionization structure by constructing the absorption measure distribution from simulated Resolve spectra, utilizing its superior resolution and effective area. Resolve constrains the column density as well as HETG, but with much shorter observations.
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Ryś, S., K. T. Chyży, M. Weżgowiec, M. Ehle, and R. Beck. "Extraplanar gas and magnetic fields in the cluster spiral galaxy NGC 4569." Proceedings of the International Astronomical Union 2, S237 (2006): 470. http://dx.doi.org/10.1017/s174392130700258x.
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AbstractThe Virgo Cluster spiral NGC 4569 is known for its compact starburst in the core and unusual outflow of Hα emitting gas perpendicular to the galaxy disk. Recent radio polarimetric observations with the Effelsberg telescope reveal huge magnetized outflows. Preliminary results of our XMM-Newton observations uncover not only hot gas in the disk but also an extensive X-ray envelope around it. We investigate the possibility of starburst-induced galactic outflows in various gas phases and cluster influence on the galaxy evolution.
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Igarashi, Asuka, Masao Mori, and Shin-ya Nitta. "A new concept of transonic galactic outflows and its application to the Sombrero galaxy." Proceedings of the International Astronomical Union 11, S321 (2016): 125. http://dx.doi.org/10.1017/s1743921316011340.
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AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming a polytropic, steady and spherically symmetric state. We have classified the transonic solutions with respect to their topology in the phase space. As a result, we have found two types of transonic solutions characterized by a magnitude relationship between the gravity of DMH and that of SMBH. These two types of solutions have different loci of the transonic points; one transonic point is formed at a central region (< 0.01kpc) and another is at a distant region (> 100kpc). Also, mass fluxes and outflow velocities are different between the two solutions. These two transonic solutions may play different roles on the star formation history of galaxies and the metal contamination of intergalactic space. Furthermore, we have applied our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as an apparent trace of galactic outflows while the star-formation rate is disproportionately low, and the observed gas density distribution is quite similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a slowly accelerating outflow in which the transonic point forms in a distant region (~ 120 kpc) and the subsonic region spreads across the stellar distribution. In the subsonic region, the gas density distribution is similar to that of the hydrostatic state. Our model predicts the possibility of the slowly accelerating outflow in the Sombrero galaxy. Igarashi et al. 2014 used the isothermal model and well reproduced the observed gas density distribution, but the estimated mass flux (1.8M⊙/yr) is lager than the mass of the gas supplied by stars (0.3-0.4M⊙/yr). Then, we expect that the polytropic model may reproduce the observational mass of the supplied gas (Igarashi et al. 2015). Such slowly accelerating outflows should be distinguished from the conventional supersonic outflows frequently argued in star-forming galaxies.
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Barnes, David J., Rahul Kannan, Mark Vogelsberger, and Federico Marinacci. "Radiative AGN feedback on a moving mesh: the impact of the galactic disc and dust physics on outflow properties." Monthly Notices of the Royal Astronomical Society 494, no. 1 (2020): 1143–64. http://dx.doi.org/10.1093/mnras/staa591.
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ABSTRACT Feedback from accreting supermassive black holes (BHs), active galactic nuclei (AGNs), is now a cornerstone of galaxy formation models. In this work, we present radiation-hydrodynamic simulations of radiative AGN feedback using the novel arepo-rt code. A central BH emits radiation at a constant luminosity and drives an outflow via radiation pressure on dust grains. Utilizing an isolated Navarro–Frenk–White (NFW) halo we validate our set-up in the single- and multiscattering regimes, with the simulated shock front propagation in excellent agreement with the expected analytic result. For a spherically symmetric NFW halo, an examination of the simulated outflow properties with radiation collimation demonstrates a decreasing mass outflow rate and momentum flux, but increasing kinetic power and outflow velocity with decreasing opening angle. We then explore the impact of a central disc galaxy and the assumed dust model on the outflow properties. The contraction of the halo during the galaxy’s formation and modelling the production of dust grains result in a factor 100 increase in the halo’s optical depth. Radiation then couples momentum more efficiently to the gas, driving a stronger shock and producing a mass-loaded $\sim \!10^{3}\, \mathrm{M}_{\odot }\, \mathrm{yr}^{-1}$ outflow with a velocity of $\sim \!2000\, \mathrm{km}\, \mathrm{s}^{-1}$. However, the inclusion of dust destruction mechanisms, like thermal sputtering, leads to the rapid destruction of dust grains within the outflow, reducing its properties below the initial NFW halo. We conclude that radiative AGN feedback can drive outflows, but a thorough numerical and physical treatment is required to assess its true impact.
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Butler, Kirsty M., Paul P. van der Werf, Theodoros Topkaras, et al. "Molecular Outflows in z > 6 Unobscured QSO Hosts Driven by Star Formation." Astrophysical Journal 944, no. 2 (2023): 134. http://dx.doi.org/10.3847/1538-4357/acad03.
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Abstract Feedback and outflows in galaxies that are associated with a quasar phase are expected to be pivotal in quenching the most massive galaxies. However, observations targeting the molecular outflow phase, which dominates both the mass and momentum and removes the immediate fuel for star formation, are limited in high-z QSO hosts. Massive quiescent galaxies found at z ∼ 4 are predicted to have quenched star formation already by z ∼ 5 and undergone their most intense growth at z > 6. Here, we present two Atacama Large Millimeter/submillimeter Array (ALMA) detections of molecular outflows, traced by blueshifted absorption of the OH 119 μm doublet, from a sample of three z > 6 infrared luminous QSO hosts: J2310+1855 and P183+05. OH 119 μm is also detected in emission from P183+05, and tentatively in the third source: P036+03. Using similar assumptions as for high-z dusty star-forming galaxy outflows, we find that our QSOs drive molecular outflows with comparable mass outflow rates, which are comparably energetic except for J2310+1855's significantly lower outflow energy flux. We do not find evidence, nor require additional input from the central active galactic nucleus (AGN) to drive the molecular outflow in J2310+1855, but we cannot rule out an AGN contribution in P183+05 if a significant AGN contribution to L FIR is assumed and/or if the outflow covering fraction is high (≥53%), which evidence from the literature suggests is unlikely in these sources. Differences observed in the blueshifted absorption spectral properties may instead be caused by the QSO hosts’ more compact dust continuums, limiting observations to lower altitude and more central regions of the outflow.
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Andrews, H., E. De Beck, and P. Hirvonen. "Multiple components in the molecular outflow of the red supergiant NML Cyg." Monthly Notices of the Royal Astronomical Society 510, no. 1 (2021): 383–98. http://dx.doi.org/10.1093/mnras/stab3244.
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ABSTRACT Despite their large impact on stellar and galactic evolution, the properties of outflows from red supergiants are not well characterized. We used the Onsala 20m telescope to perform a spectral survey at 3 and 4 mm (68–116 GHz) of the red supergiant NML Cyg, alongside the yellow hypergiant IRC + 10420. Our observations of NML Cyg were combined with complementary archival data to enable a search for signatures of morphological complexity in the circumstellar environment, using emission lines from 15 molecular species. The recovered parameters imply the presence of three distinct, coherent, and persistent components, comprised of blue-shifted and red-shifted components, in addition to an underlying outflow centred at the stellar systemic velocity. Furthermore, to reproduce 12CO emission with 3D radiative transfer models required a spherical outflow with three superposed conical outflows, one towards and one away from the observer, and one in the plane of the sky. These components are higher in density than the spherical outflow by up to an order of magnitude. We hence propose that NML Cyg’s circumstellar environment consists of a small number of high-density large-scale coherent outflows embedded in a spherical wind. This would make the mass-loss history similar to that of VY CMa, and distinct from μ Cep, where the outflow contains many randomly distributed smaller clumps. A possible correlation between stellar properties, outflow structures, and content is critical in understanding the evolution of massive stars and their environmental impact.
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Sugahara, Yuma, Masami Ouchi, Yuichi Harikane, Nicolas Bouché, Peter D. Mitchell, and Jérémy Blaizot. "Galactic outflows in star-forming galaxies at z ∼ 6 studied with deep UV spectra and ALMA emission line." Proceedings of the International Astronomical Union 15, S341 (2019): 307–8. http://dx.doi.org/10.1017/s1743921319002126.
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AbstractWe present a velocity of galactic outflows in star-forming galaxies at the highest redshift, z ∼ 6, so far studied with metal absorption lines. Absorption-line studies of galactic outflows need well-determined redshifts, but there are few strong emission lines in the observed-frame optical spectra of galaxies at high redshifts. In this work, we use the systemic redshifts determined by the ALMA [CII]158 μm emission lines. The sample consists of seven Lyman break galaxies at 5.1 < z < 5.7 whose Keck/DEIMOS and ALMA data are available in the archive. The outflow maximum velocity (νmax) is estimated by a fitting of line profiles to metal absorption lines in a composite spectrum. We find that νmax monotonically increases from z ∼ 0 to 6 and that νmax tightly correlates with the halo circular velocity estimated from the stellar mass.
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Yamasaki, Shotaro, Kazumi Kashiyama, and Kohta Murase. "Multi-wavelength constraints on the outflow properties of the extremely bright millisecond radio bursts from the galactic magnetar SGR 1935 + 2154." Monthly Notices of the Royal Astronomical Society 511, no. 3 (2022): 3138–49. http://dx.doi.org/10.1093/mnras/stac234.
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ABSTRACT Extremely bright coherent radio bursts with millisecond duration, reminiscent of cosmological fast radio bursts, were codetected with anomalously-hard X-ray bursts from a Galactic magnetar SGR 1935 + 2154. We investigate the possibility that the event was triggered by the magnetic energy injection inside the magnetosphere, thereby producing magnetically-trapped fireball (FB) and relativistic outflows simultaneously. The thermal component of the X-ray burst is consistent with a trapped FB with an average temperature of ∼200–300 keV and size of ∼105 cm. Meanwhile, the non-thermal component of the X-ray burst and the coherent radio burst may arise from relativistic outflows. We calculate the dynamical evolution of the outflow, launched with an energy budget of 1039–1040 erg comparable to that for the trapped FB, for different initial baryon load η and magnetization σ0. If hard X-ray and radio bursts are both produced by the energy dissipation of the outflow, the outflow properties are constrained by combining the conditions for photon escape and the intrinsic timing offset ≲ 10 ms among radio and X-ray burst spikes. We show that the hard X-ray burst must be generated at rX ≳ 108 cm from the magnetar, irrespective of the emission mechanism. Moreover, we find that the outflow quickly accelerates up to a Lorentz factor of 102 ≲ Γ ≲ 103 by the time it reaches the edge of the magnetosphere and the dissipation occurs at 1012 cm ≲ rradio, X ≲ 1014 cm. Our results imply either extremely-clean (η ≳ 104) or highly-magnetized (σ0 ≳ 103) outflows, which might be consistent with the rarity of the phenomenon.
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Nelson, Dylan, Annalisa Pillepich, Volker Springel, et al. "First results from the TNG50 simulation: galactic outflows driven by supernovae and black hole feedback." Monthly Notices of the Royal Astronomical Society 490, no. 3 (2019): 3234–61. http://dx.doi.org/10.1093/mnras/stz2306.
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Abstract We present the new TNG50 cosmological, magnetohydrodynamical simulation – the third and final volume of the IllustrisTNG project. This simulation occupies a unique combination of large volume and high resolution, with a 50 Mpc box sampled by 21603 gas cells (baryon mass of 8 × 104 M⊙). The median spatial resolution of star-forming interstellar medium gas is ∼100−140 pc. This resolution approaches or exceeds that of modern ‘zoom’ simulations of individual massive galaxies, while the volume contains ∼20 000 resolved galaxies with $M_\star \gtrsim 10^7$ M⊙. Herein we show first results from TNG50, focusing on galactic outflows driven by supernovae as well as supermassive black hole feedback. We find that the outflow mass loading is a non-monotonic function of galaxy stellar mass, turning over and rising rapidly above 1010.5 M⊙ due to the action of the central black hole (BH). The outflow velocity increases with stellar mass, and at fixed mass it is faster at higher redshift. The TNG model can produce high-velocity, multiphase outflows that include cool, dense components. These outflows reach speeds in excess of 3000 km s−1 out to 20 kpc with an ejective, BH-driven origin. Critically, we show how the relative simplicity of model inputs (and scalings) at the injection scale produces complex behaviour at galactic and halo scales. For example, despite isotropic wind launching, outflows exhibit natural collimation and an emergent bipolarity. Furthermore, galaxies above the star-forming main sequence drive faster outflows, although this correlation inverts at high mass with the onset of quenching, whereby low-luminosity, slowly accreting, massive BHs drive the strongest outflows.
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Kannan, R., M. Vogelsberger, F. Marinacci, L. V. Sales, P. Torrey, and L. Hernquist. "Dust entrainment in galactic winds." Monthly Notices of the Royal Astronomical Society 503, no. 1 (2021): 336–43. http://dx.doi.org/10.1093/mnras/stab416.
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ABSTRACT Winds driven by stellar feedback are an essential part of the galactic ecosystem and are the main mechanism through which low-mass galaxies regulate their star formation. These winds are generally observed to be multiphase with detections of entrained neutral and molecular gas. They are also thought to enrich the circumgalactic medium around galaxies with metals and dust. This ejected dust encodes information about the integrated star formation and outflow history of the galaxy. Therefore it is important to understand how much dust is entrained and driven out of the disc by galactic winds. Here, we demonstrate that stellar feedback is efficient in driving dust-enriched winds and eject enough material to account for the amount of extraplanar dust observed in nearby galaxies. The amount of ejected dust depends on the sites from where they are launched, with dustier galaxies launching more dust-enriched outflows. Moreover, the outflowing cold and dense gas is significantly more dust enriched than the volume filling hot and tenuous material. These results provide an important new insight into the dynamics, structure, and composition of galactic winds and their role in determining the dust content of the extragalactic gas in galaxies.