Journal articles: 'Circum-galactic medium'

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Li, Jiang‐Tao. "An X‐ray view of the hot circum‐galactic medium." Astronomische Nachrichten 341, no. 2 (February 2020): 177–83. http://dx.doi.org/10.1002/asna.202023775.

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Augustin, Ramona, Céline Péroux, Palle Møller, Varsha Kulkarni, Hadi Rahmani, Bruno Milliard, Matthew Pieri, et al. "Characterizing the circum-galactic medium of damped Lyman-α absorbing galaxies." Monthly Notices of the Royal Astronomical Society 478, no. 3 (May 17, 2018): 3120–32. http://dx.doi.org/10.1093/mnras/sty1287.

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Arrigoni Battaia, Fabrizio, Joseph F. Hennawi, Sebastiano Cantalupo, and J. Xavier Prochaska. "THE STACKED LYαEMISSION PROFILE FROM THE CIRCUM-GALACTIC MEDIUM OFz∼ 2 QUASARS." Astrophysical Journal 829, no. 1 (September 13, 2016): 3. http://dx.doi.org/10.3847/0004-637x/829/1/3.

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Hirashita, Hiroyuki, and Ting-Wen Lan. "Shattering as a source of small grains in the circum-galactic medium." Monthly Notices of the Royal Astronomical Society 505, no. 2 (May 17, 2021): 1794–805. http://dx.doi.org/10.1093/mnras/stab1416.

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ABSTRACT Observed reddening in the circum-galactic medium (CGM) indicates a significant abundance of small grains, of which the origin is still to be clarified. We examine a possible path of small-grain production through shattering of pre-existing large grains in the CGM. Possible sites where shattering occurs on a reasonable time-scale are cool clumps with hydrogen number density nH ∼ 0.1 cm−3 and gas temperature Tgas ∼ 104 K, which are shown to exist through observations of Mg ii absorbers. We calculate the evolution of grain size distribution in physical conditions appropriate for cool clumps in the CGM, starting from a large-grain-dominated distribution suggested from theoretical studies. With an appropriate gas turbulence model expected from the physical condition of cold clumps (maximum eddy size and velocity of ∼100 pc and 10 km s−1, respectively), together with the above gas density and temperature and the dust-to-gas mass ratio inferred from observations (0.006), we find that small-grain production occurs on a time-scale (a few × 108 yr) comparable to the lifetime of cool clumps derived in the literature. Thus, the physical conditions of the cool clouds are favourable for small-grain production. We also confirm that the reddening becomes significant on the above time-scale. Therefore, we conclude that small-grain production by shattering is a probable cause for the observed reddening in the CGM. We also mention the effect of grain materials (or their mixtures) on the reddening at different redshifts (1 and 2).

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Zhou, Zi-Hang, Jin-Ping Zhu, and Kai Wang. "High-energy Neutrino Production from AGN Disk Transients Impacted by the Circum-disk Medium." Astrophysical Journal 951, no. 1 (July 1, 2023): 74. http://dx.doi.org/10.3847/1538-4357/acd380.

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Abstract Various supernovae, compact object coalescences, and tidal disruption events are widely believed to occur embedded in active galactic nucleus (AGN) accretion disks and generate detectable electromagnetic signals. We collectively refer to them as AGN disk transients. The inelastic hadronuclear (pp) interactions between shock-accelerated cosmic rays and AGN disk materials shortly after the ejecta shock breaks out of the disk can produce high-energy neutrinos. However, the expected efficiency of neutrino production would decay rapidly by adopting a pure Gaussian density atmosphere profile applicable for stable gas-dominated disks. On the other hand, AGN outflows and disk winds are commonly found around AGN accretion disks. In this paper, we show that the circum-disk medium would further consume the shock kinetic energy to more efficiently produce high-energy neutrinos, especially for ∼ TeV−PeV neutrinos that IceCube detects. Thanks to the existence of the circum-disk medium, we find that the neutrino production will be enhanced significantly and make a much higher contribution to the diffuse neutrino background. Optimistically, ∼20% of the diffuse neutrino background can be contributed by AGN disk transients.

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Hani, Maan H., Martin Sparre, Sara L. Ellison, Paul Torrey, and Mark Vogelsberger. "Galaxy mergers moulding the circum-galactic medium – I. The impact of a major merger." Monthly Notices of the Royal Astronomical Society 475, no. 1 (December 20, 2017): 1160–76. http://dx.doi.org/10.1093/mnras/stx3252.

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Olsen, Karen, Andrea Pallottini, Aida Wofford, Marios Chatzikos, Mitchell Revalski, Francisco Guzmán, Gergö Popping, et al. "Challenges and Techniques for Simulating Line Emission." Galaxies 6, no. 4 (September 20, 2018): 100. http://dx.doi.org/10.3390/galaxies6040100.

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Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.

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Wendt, Martin, Nicolas F. Bouché, Johannes Zabl, Ilane Schroetter, and Sowgat Muzahid. "MusE GAs FLOw and Wind V. The dust/metallicity-anisotropy of the circum-galactic medium." Monthly Notices of the Royal Astronomical Society 502, no. 3 (January 11, 2021): 3733–45. http://dx.doi.org/10.1093/mnras/stab049.

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ABSTRACT We investigate whether the dust content of the circum-galactic medium (CGM) depends on the location of the quasar sightline with respect to the galaxy major-axis using 13 galaxy-Mg ii absorber pairs (9–81 kpc distance) from the MusE GAs FLOw and Wind (MEGAFLOW) survey at 0.4 < z < 1.4. The dust content of the CGM is obtained from [Zn/Fe] using ultraviolet and visual echelle spectrograph data. When a direct measurement of [Zn/Fe] is unavailable, we estimate the dust depletion from a method that consists in solving for the depletion from multiple singly ionized ions (e.g. Mn ii, Cr ii, and Zn ii) since each ion depletes on dust grains at different rates. We find a positive correlation between the azimuthal angle and [Zn/Fe] with a Pearson’s r = 0.70 ± 0.14. The sightlines along the major axis show [Zn/Fe] < 0.5, whereas the [Zn/Fe] is > 0.8 along the minor axis. These results suggest that the CGM along the minor axis is on average more metal enriched (by ≈ 1 dex) than the gas located along the major axis of galaxies provided that dust depletion is a proxy for metallicity. This anisotropic distribution is consistent with recent results on outflow and accretion in hydro-dynamical simulations.

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Sravan, Niharika, Claude-André Faucher-Giguère, Freeke van de Voort, Dušan Kereš, Alexander L. Muratov, Philip F. Hopkins, Robert Feldmann, Eliot Quataert, and Norman Murray. "Strongly time-variable ultraviolet metal-line emission from the circum-galactic medium of high-redshift galaxies." Monthly Notices of the Royal Astronomical Society 463, no. 1 (August 8, 2016): 120–33. http://dx.doi.org/10.1093/mnras/stw1962.

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Momose, Rieko, Tomotsugu Goto, Yousuke Utsumi, Tetsuya Hashimoto, Chia-Ying Chiang, Seong-Jin Kim, Nobunari Kashikawa, Kazuhiro Shimasaku, and Satoshi Miyazaki. "Possible evolution of the circum-galactic medium around QSOs with QSO age and cosmic time revealed by Ly α haloes." Monthly Notices of the Royal Astronomical Society 488, no. 1 (June 25, 2019): 120–34. http://dx.doi.org/10.1093/mnras/stz1707.

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ABSTRACT We first present new Subaru narrow-band observations of the Ly α halo around the quasi-stellar object (QSO) CFHQ J232908−030158 at z = 6.42, which appears the most luminous and extended halo at z > 5 (LLy α = 9.8 × 1043 erg s−1 within 37 pkpc diameter). Then, combining these measurements with available data in the literature, we find two different evolutions of QSOs’ Ly α haloes. First is a possible short-term evolution with QSO age seen in four z > 6 QSOs. We find the anticorrelation between the Ly α halo scales with QSOs’ infrared (IR) luminosity, with J2329−0301’s halo being the brightest and largest. It indicates that ionizing photons escape more easily out to circum-galactic regions when host galaxies are less dusty. We also find a positive correlation between IR luminosity and black hole mass (MBH). Given MBH as an indicator of QSO age, we propose a hypothesis that a large Ly α halo mainly exists around QSOs in the young phase of their activity due to a small amount of dust. The second is an evolution with cosmic time seen over z ∼ 2–5. We find the increase of surface brightness towards lower redshift with a similar growth rate to that of dark matter haloes (DHs) that evolve to MDH = 1012–1013 M⊙ at z = 2. The extent of Ly α haloes is also found to increase at a rate scaling with the virial radius of growing DHs, $r_\text{vir} \propto M_\text{DH}^{1/3}(1+z)^{-1}$. These increases are consistent with a scenario that the circum-galactic medium around QSOs evolves in mass and size keeping pace with hosting DHs.

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Li, Jiang-Tao, Joel N. Bregman, Q. Daniel Wang, Robert A. Crain, and Michael E. Anderson. "THE CIRCUM-GALACTIC MEDIUM OF MASSIVE SPIRALS. I. AN OVERVIEW AND A CASE STUDY OF NGC 5908." Astrophysical Journal 830, no. 2 (October 18, 2016): 134. http://dx.doi.org/10.3847/0004-637x/830/2/134.

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Gutcke, Thales A., Greg S. Stinson, Andrea V. Macciò, Liang Wang, and Aaron A. Dutton. "NIHAO – VIII. Circum-galactic medium and outflows – The puzzles of H i and O vi gas distributions." Monthly Notices of the Royal Astronomical Society 464, no. 3 (October 5, 2016): 2796–815. http://dx.doi.org/10.1093/mnras/stw2539.

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Leclercq, Floriane, Roland Bacon, Anne Verhamme, Thibault Garel, Jérémy Blaizot, Jarle Brinchmann, Sebastiano Cantalupo, et al. "The MUSE Hubble Ultra Deep Field Survey." Astronomy & Astrophysics 635 (March 2020): A82. http://dx.doi.org/10.1051/0004-6361/201937339.

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We present spatially resolved maps of six individually-detected Lyman α haloes (LAHs) as well as a first statistical analysis of the Lyman α (Lyα) spectral signature in the circum-galactic medium of high-redshift star-forming galaxies (−17.5 > MUV > −21.5) using the Multi-Unit Spectroscopic Explorer. Our resolved spectroscopic analysis of the LAHs reveals significant intrahalo variations of the Lyα line profile. Using a three-dimensional two-component model for the Lyα emission, we measured the full width at half maximum (FWHM), the peak velocity shift, and the asymmetry of the Lyα line in the core and in the halo of 19 galaxies. We find that the Lyα line shape is statistically different in the halo compared to the core (in terms of width, peak wavelength, and asymmetry) for ≈40% of our galaxies. Similarly to object-by-object based studies and a recent resolved study using lensing, we find a correlation between the peak velocity shift and the width of the Lyα line both at the interstellar and circum-galactic scales. This trend has been predicted by radiative transfer simulations of galactic winds as a result of resonant scattering in outflows. While there is a lack of correlation between the spectral properties and the spatial scale lengths of our LAHs, we find a correlation between the width of the line in the LAH and the halo flux fraction. Interestingly, UV bright galaxies (MUV < −20) show broader, more redshifted, and less asymmetric Lyα lines in their haloes. The most significant correlation found is for the FWHM of the line and the UV continuum slope of the galaxy, suggesting that the redder galaxies have broader Lyα lines. The generally broad and red line shapes found in the halo component suggest that the Lyα haloes are powered either by scattering processes through an outflowing medium, fluorescent emission from outflowing cold clumps of gas, or a mix of both. Considering the large diversity of the Lyα line profiles observed in our sample and the lack of strong correlation, the interpretation of our results is still broadly open and underlines the need for realistic spatially resolved models of the LAHs.

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Heckman, Timothy, Sanchayeeta Borthakur, Vivienne Wild, David Schiminovich, and Rongmon Bordoloi. "COS-burst: Observations of the Impact of Starburst-driven Winds on the Properties of the Circum-galactic Medium." Astrophysical Journal 846, no. 2 (September 12, 2017): 151. http://dx.doi.org/10.3847/1538-4357/aa80dc.

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Liu, W., L. Ji, H. Y. Qiu, Z. Lou, M. S. Cai, H. J. Zhou, and T. L. Huo. "Research on a back-illuminated CMOS sensor for LUV imaging." Journal of Instrumentation 17, no. 08 (August 1, 2022): T08004. http://dx.doi.org/10.1088/1748-0221/17/08/t08004.

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Abstract The Lyman UV (LUV) band possesses several unique characteristics that make it useful to study the properties of the interstellar medium and the circum-galactic medium (CGM) surrounding nearby galaxies. MCP detectors are sensitive in the LUV band and can be used as imagers and photon counters in space missions. Instead of MCP, this paper describes a new CMOS imaging system that can be applied to astronomical observations in the LUV band. We adopted a special back-side illuminated CMOS as the image sensor. Using it, we developed a LUV imaging system based on FPGA technology. With the assistance of a synchrotron radiation platform, the properties of the CMOS imaging system were measured and calibrated within the wavelength range from 105 nm to 130 nm. By calibrating gain, photon current, electron number and photon number parameters, we derived the quantum efficiency curve for this wavelength range. Such a development provides a new method to detect and image Lyman UV radiations.

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D’Odorico, V., K. Finlator, S. Cristiani, G. Cupani, S. Perrotta, F. Calura, M. Cènturion, et al. "The evolution of the Si iv content in the Universe from the epoch of reionization to cosmic noon." Monthly Notices of the Royal Astronomical Society 512, no. 2 (February 28, 2022): 2389–401. http://dx.doi.org/10.1093/mnras/stac545.

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ABSTRACT We investigate the abundance and distribution of metals in the high-redshift intergalactic medium and circum-galactic medium through the analysis of a sample of almost 600 Si iv absorption lines detected in high- and intermediate-resolution spectra of 147 quasars. The evolution of the number density of Si iv lines, the column density distribution function, and the cosmic mass density are studied in the redshift interval 1.7 ≲ z ≲ 6.2 and for log N(Si iv) ≥ 12.5. All quantities show a rapid increase between z ∼ 6 and z ≲ 5 and then an almost constant behaviour to z ∼ 2 in very good agreement with what is already observed for C iv absorption lines. The present results are challenging for numerical simulations: When simulations reproduce our Si iv results, they tend to underpredict the properties of C iv, and when the properties of C iv are reproduced, the number of strong Si iv lines [log N(Si iv) > 14] is overpredicted.

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Steinwandel, Ulrich P., Klaus Dolag, Harald Lesch, Benjamin P. Moster, Andreas Burkert, and Almudena Prieto. "On the origin of magnetic driven winds and the structure of the galactic dynamo in isolated galaxies." Monthly Notices of the Royal Astronomical Society 494, no. 3 (March 27, 2020): 4393–412. http://dx.doi.org/10.1093/mnras/staa817.

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ABSTRACT We investigate the build-up of the galactic dynamo and subsequently the origin of a magnetic driven outflow. We use a set-up of an isolated disc galaxy with a realistic circum-galactic medium (CGM). We find good agreement of the galactic dynamo with theoretical and observational predictions from the radial and toroidal components of the magnetic field as function of radius and disc scale height. We find several field reversals indicating dipole structure at early times and quadrupole structure at late times. Together with the magnetic pitch angle and the dynamo control parameters Rα, Rω, and D, we present strong evidence for an α2–Ω dynamo. The formation of a bar in the centre leads to further amplification of the magnetic field via adiabatic compression which subsequently drives an outflow. Due to the Parker instability the magnetic field lines rise to the edge of the disc, break out, and expand freely in the CGM driven by the magnetic pressure. Finally, we investigate the correlation between magnetic field and star formation rate. Globally, we find that the magnetic field is increasing as function of the star formation rate surface density with a slope between 0.3 and 0.45 in good agreement with predictions from theory and observations. Locally, we find that the magnetic field can decrease while star formation increases. We find that this effect is correlated with the diffusion of magnetic field from the spiral arms to the interarm regions which we explicitly include by solving the induction equation and accounting for non-linear terms.

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Leclercq, Floriane, Roland Bacon, Lutz Wisotzki, Peter Mitchell, Thibault Garel, Anne Verhamme, Jérémy Blaizot, et al. "The MUSE Hubble Ultra Deep Field Survey." Astronomy & Astrophysics 608 (November 29, 2017): A8. http://dx.doi.org/10.1051/0004-6361/201731480.

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We report the detection of extended Lyα haloes around 145 individual star-forming galaxies at redshifts 3 ≤ z ≤ 6 in the Hubble Ultra Deep Field observed with the Multi-Unit Spectroscopic Explorer (MUSE) at ESO-VLT. Our sample consists of continuum-faint (− 15 ≥ MUV ≥ −22) Lyα emitters (LAEs). Using a 2D, two-component (continuum-like and halo) decomposition of Lyα emission assuming circular exponential distributions, we measure scale lengths and luminosities of Lyα haloes. We find that 80% of our objects having reliable Lyα halo measurements show Lyα emission that is significantly more extended than the UV continuum detected by HST (by a factor ≈4 to >20). The median exponential scale length of the Lyα haloes in our sample is ≈4.5 kpc with a few haloes exceeding 10 kpc. By comparing the maximal detected extent of the Lyα emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Lyα emission of our selected sample of Lyα emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). This result therefore shows that there must be significant HI reservoirs in the circum-galactic medium and reinforces the idea that Lyα haloes are ubiquitous around high-redshift Lyα emitting galaxies. Our characterization of the Lyα haloes indicates that the majority of the Lyα flux comes from the halo (≈65%) and that their scale lengths seem to be linked to the UV properties of the galaxies (sizes and magnitudes). We do not observe a significant Lyα halo size evolution with redshift, although our sample for z> 5 is very small. We also explore the diversity of the Lyα line profiles in our sample and we find that the Lyα lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km s-1. While the FWHM does not seem to be correlated to the Lyα scale length, most compact Lyα haloes and those that are not detected with high significance tend to have narrower Lyα profiles (<350 km s-1). Finally, we investigate the origin of the extended Lyα emission but we conclude that our data do not allow us to disentangle the possible processes, i.e. scattering from star-forming regions, fluorescence, cooling radiation from cold gas accretion, and emission from satellite galaxies.

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Emonts, Bjorn. "Jet-CO alignments in the environments high-z radio galaxies." Proceedings of the International Astronomical Union 11, S321 (March 2016): 348–50. http://dx.doi.org/10.1017/s1743921316011613.

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AbstractIn the outskirts of massive high-redshift radio galaxies, powerful radio-jets often interact with ambient warm Lyα-emitting gas. We present the discovery of luminous reservoirs of cold molecular gas in these environments, based on CO(1-0) observations with the Australia Telescope Compact Array. The CO-emission is aligned with the radio jets, and found tens of kpc outside the host galaxy. These molecular gas reservoirs have CO luminosities in the range of those found in submm-galaxies (L'CO ~ 4-9 × 1010 K km/s pc2), but they lack any near-infrared counterpart in deep Spitzer imaging. These results suggest that jet-triggered feedback takes place in the circum-galactic environment of high-z radio galaxies. We prefer the interpretation that the CO-emitting gas is formed when the propagating jets enrich, shock and cool pre-existing dusty halo gas. We further argue that sensitive low-surface-brightness CO observations, using radio interferometers in very compact array-configurations, are essential to study the role of the cold molecular medium in the outskirts of massive high-z galaxies.

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Li, Jiang-Tao, Joel N. Bregman, Q. Daniel Wang, Robert A. Crain, and Michael E. Anderson. "Erratum: “The Circum-galactic Medium of Massive Spirals. I. An Overview and a Case Study of NGC 5908” (2016, ApJ, 830, 134)." Astrophysical Journal 902, no. 1 (October 14, 2020): 87. http://dx.doi.org/10.3847/1538-4357/abbacf.

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Li, Jiang-Tao, Joel N. Bregman, Q. Daniel Wang, Robert A. Crain, Michael E. Anderson, and Shangjia Zhang. "The Circum-Galactic Medium of Massive Spirals. II. Probing the Nature of Hot Gaseous Halo around the Most Massive Isolated Spiral Galaxies." Astrophysical Journal Supplement Series 233, no. 2 (December 7, 2017): 20. http://dx.doi.org/10.3847/1538-4365/aa96fc.

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Sarrato-Alós, J., C. Brook, and A. Di Cintio. "Constraining gas metal mixing strength in simulations using observations of the Milky Way’s disc." Monthly Notices of the Royal Astronomical Society 525, no. 1 (August 7, 2023): 279–85. http://dx.doi.org/10.1093/mnras/stad2365.

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ABSTRACT This work explores the mixing rate of metals in the interstellar medium (ISM), comparing observational constraints from our solar neighbourhood to high resolution cosmological hydrodynamical simulations of Milky Way (MW)-like galaxies. The mixing rate, described by the coefficient C, is varied in simulations between 0 and 0.05, with resultant simulated galaxies compared to observations of metallicity dispersion in young star clusters, H ii regions and neutral gas in the disc of the MW. A value of C between 0.003125 and 0.0125 is found to self-consistently match a range of observables, with a best estimate of C = 0.0064 ± 0.0004. We demonstrate that the relationship between metal dispersion in young stars, H ii regions and neutral gas, versus the coefficient C, can be described by a power law. These constrained mixing rates infer a comparatively well-mixed ISM in the solar neighbourhood, at odds with some recent observations that have reported a highly inhomogeneous ISM. The degree of mixing suggested by this work is lower than what often employed in many hydrodynamical simulations. Our results have implications for studying the metallicity distribution of stars as well as of gas in the interstellar and circum-galactic media.

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Wang, Ailing, Tao An, Sumit Jaiswal, Prashanth Mohan, Yuchan Wang, Willem A. Baan, Yingkang Zhang, and Xiaolong Yang. "The obstructed jet in Mrk 231." Monthly Notices of the Royal Astronomical Society 504, no. 3 (March 3, 2021): 3823–30. http://dx.doi.org/10.1093/mnras/stab587.

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ABSTRACT Mrk 231 is the closest radio-quiet quasar known and one of the most luminous infrared galaxies in the local Universe. It is characterized by the co-existence of a radio jet and powerful multiphase multiscale outflows, making it an ideal laboratory to study active galactic nucleus (AGN) feedback. We analyse the multi-epoch very long baseline interferometry data of Mrk 231 and estimate the jet head advance speed to be ≲0.013 c, suggesting a sub-relativistic jet flow. The jet position angle changes from −113○ in the inner parsec to −172○ at a projected distance of 25 pc. The jet structure change might result from either a jet bending following the rotation of the circum-nuclear disc or the projection of a helical jet on the plane of the sky. In the large opening angle (∼60○) cone, the curved jet interacts with the interstellar medium and creates wide-aperture-angle shocks that subsequently dissipate a large portion of the jet power through radiation and contribute to powering the large-scale outflows. The low power and bent structure of the Mrk 231 jet, as well as extensive radiation dissipation, are consistent with the obstruction of the short-length jet by the host galaxy’s environment.

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Falocco, S., J. Larsson, and S. Nandi. "Accretion and jets in a low-luminosity AGN: the nucleus of NGC 1052." Astronomy & Astrophysics 638 (June 2020): A67. http://dx.doi.org/10.1051/0004-6361/202037516.

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Aims. We aim to determine the properties of the central region of NGC 1052 using X-ray and radio data. NGC 1052 (z = 0.005) has been investigated for decades in different energy bands and shows radio lobes and a low-luminosity active galactic nucleus. Methods. We used X-ray images from Chandra and radio images from Very Large Array to explore the morphology of the central area. We also studied the spectra of the nucleus and the surrounding region using observations from Chandra and XMM-Newton. Results. We find diffuse soft X-ray radiation and hot-spots along the radio lobes. The spectrum of the circum-nuclear region is well described by a thermal plasma (T ∼ 0.6 keV) and a power law with photon index Γ ∼ 2.3. The nucleus shows a hard power law (Γ ∼ 1.4) modified by complex absorption. A narrow iron Kα line is also clearly detected in all observations, but there is no evidence for relativistic reflection. Conclusions. The extended emission is consistent with originating from extended jets and from jet-triggered shocks in the surrounding medium. The hard power-law emission from the nucleus and the lack of relativistic reflection supports the scenario of inefficient accretion in an advection-dominated accretion flow.

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Wright, Ruby J., Claudia del P. Lagos, Chris Power, and Camila A. Correa. "Revealing the physical properties of gas accreting to haloes in the EAGLE simulations." Monthly Notices of the Royal Astronomical Society 504, no. 4 (April 17, 2021): 5702–25. http://dx.doi.org/10.1093/mnras/stab1057.

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ABSTRACT The inflow of cosmological gas on to haloes, while challenging to directly observe and quantify, plays a fundamental role in the baryon cycle of galaxies. Using the eagle suite of hydrodynamical simulations, we present a thorough exploration of the physical properties of gas accreting on to haloes – namely, its spatial characteristics, density, temperature, and metallicity. Classifying accretion as ‘hot’ or ‘ cold’ based on a temperature cut-off 105.5 K, we find that the covering fraction (fcov) of cold-mode accreting gas is significantly lower than the hot-mode, with z = 0 fcov values of ${\approx}50{{\ \rm per\ cent}}$ and ${\approx}80{{\ \rm per\ cent}}$, respectively. Active galactic nucleus (AGN) feedback in eagle reduces inflow fcov values by ${\approx}10{{\ \rm per\ cent}}$, with outflows decreasing the solid angle available for accretion flows. Classifying inflow by particle history, we find that gas on first-infall on to a halo is metal depleted by ≈2 dex compared to pre-processed gas, which we find to mimic the circum-galactic medium (CGM) in terms of metal content. We also show that high (low) halo-scale gas accretion rates are associated with metal-poor (rich) CGM in haloes below $10^{12}\, \mathrm{M}_{\odot }$, and that variation in halo-scale gas accretion rates may offer a physical explanation for the enhanced scatter in the star-forming main sequence at low (${\lesssim}10^{9}\, \mathrm{M}_{\odot }$) and high (${\gtrsim}10^{10}\, \mathrm{M}_{\odot }$) stellar masses. Our results highlight how gas inflow influences several halo- and galaxy-scale properties, and the need to combine kinematic and chemical data in order to confidently break the degeneracy between accreting and outgoing gas in CGM observations.

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Travascio, A., L. Zappacosta, S. Cantalupo, E. Piconcelli, F. Arrigoni Battaia, M. Ginolfi, M. Bischetti, et al. "The WISSH quasars project." Astronomy & Astrophysics 635 (March 2020): A157. http://dx.doi.org/10.1051/0004-6361/201936197.

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Context. In recent years, Lyα nebulae have been routinely detected around high redshift, radio-quiet quasars thanks to the advent of the highly sensitive integral field spectrographs. Constraining the physical properties of the Lyα nebulae is crucial for a full understanding of the circum-galactic medium (CGM). The CGM acts both as a repository for intergalactic and galactic baryons as well as a venue of feeding and feedback processes. The most luminous quasars are privileged test-beds to study these processes, given their large ionising fluxes and dense CGM environments in which they are expected to be embedded. Aims. We aim to characterise the rest-frame ultraviolet (UV) emission lines in the CGM around a hyper-luminous, broad emission line, radio-quiet quasar at z ∼ 3.6, which exhibits powerful outflows at both nuclear and host galaxy scales. Methods. We analyse VLT/MUSE observations of the quasar J1538+08 (Lbol = 6 × 1047 erg s−1), and we performed a search for extended UV emission lines to characterise its morphology, emissivity, kinematics, and metal content. Results. We report the discovery of a very luminous (∼2 × 1044 erg s−1), giant Lyα nebula and a likely associated extended (75 kpc) CIV nebula. The Lyα nebula emission exhibits moderate blueshift (∼440 km s−1) compared to the quasar systemic redshift and a large average velocity dispersion (σ¯v ∼ 700 km s−1) across the nebula, while the CIV nebula shows average velocity dispersion of σ¯v ∼ 350 km s−1. The Lyα line profile exhibits a significant asymmetry towards negative velocity values at 20−30 kpc south of the quasar and is well parametrised by the following two Gaussian components: a narrow (σ ∼ 470 km s−1) systemic one plus a broad (σ ∼ 1200 km s−1), blueshifted (∼1500 km s−1) one. Conclusions. Our analysis of the MUSE observation of J1538+08 reveals metal-enriched CGM around this hyper-luminous quasar. Furthermore, our detection of blueshifted emission in the emission profile of the Lyα nebula suggests that powerful nuclear outflows can propagate through the CGM over tens of kiloparsecs.

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Luminari, A., F. Tombesi, E. Piconcelli, F. Nicastro, K. Fukumura, D. Kazanas, F. Fiore, and L. Zappacosta. "The importance of special relativistic effects in modelling ultra-fast outflows." Astronomy & Astrophysics 633 (January 2020): A55. http://dx.doi.org/10.1051/0004-6361/201936797.

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Context. Outflows are observed in a variety of astrophysical sources. Remarkably, ultra-fast (v ≥ 0.1c), highly ionised outflows in the UV and X-ray bands are often seen in active galactic nuclei (AGNs). Depending on their kinetic power and mass outflow rate, Ėout and Ṁout, respectively, these outflows may play a key role in regulating the AGN–host galaxy co-evolution process through cosmic time and metal-feeding the surrounding circum-/inter-galactic medium. It is therefore crucial to provide accurate estimates of the wind properties, including Ṁout and Ėout. Aims. Here we concentrate on special relativistic effects concerning the interaction of light with matter moving at relativistic speed relatively to the source of radiation. Our aim is to assess the impact of these effects on the observed properties of the outflows and implement a correction for these effects in the existing spectral modelling routines. Methods. We define a simple procedure to incorporate relativistic effects in radiative transfer codes. Following this procedure, we run a series of simulations to explore the impact of relativistic effects for different outflow velocities and column densities. Results. The observed optical depth of the wind is usually considered a proxy for its column density NH, independently of the velocity of the outflow. However, our simulations show that the observed optical depth of an outflow with a given NH decreases rapidly as the velocity of the wind approaches relativistic values. This, in turn, implies that when estimating NH from the optical depth, it is necessary to include a velocity-dependent correction, already for moderate velocities (e.g. vout ≳ 0.05c). This correction linearly propagates to the derived quantities Ṁout and Ėout. Conclusions. We demonstrate that special relativistic effects must be considered in order to obtain correct estimates of Ṁout and Ėout for an outflow moving at a mildly relativistic speed relative to the illuminating source of radiation. As an example, we calculate the relativistically corrected values of Ṁout and Ėout for a sample of ∼30 ultra-fast outflows (UFOs) taken from the literature and find correction factors of 20 − 120% within the observed range of outflowing velocities (vout ≈ 0.1 − 0.3c). This brings the ratio between Ṁout and the disc accretion rate close or even above unity for the vast majority of the sources of the sample, highlighting the importance of the reported relativistic corrections to understand the growth of the most massive black holes. The next generation of high-sensitivity X-ray telescopes such as XRISM and Athena will provide a much more complete census of UFOs, especially in the fastest velocity regime where the relativistic corrections are increasingly important.

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Ottolina, Riccardo, Renato Falomo, Aldo Treves, Michela Uslenghi, Jari K. Kotilainen, Riccardo Scarpa, and Emanuele Paolo Farina. "Circum-Galactic Medium in the Halo of Quasars." Frontiers in Astronomy and Space Sciences 4 (December 21, 2017). http://dx.doi.org/10.3389/fspas.2017.00061.

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Sandrinelli, A., R. Falomo, A. Treves, S. Paiano, and R. Scarpa. "The circum-galactic medium of quasars: transverse and line-of-sight absorptions." Astrophysics and Space Science 365, no. 11 (November 2020). http://dx.doi.org/10.1007/s10509-020-03889-0.

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AbstractQuasar projected pairs (QPPs) can be used for investigating the circumgalactic medium of quasars through the study of intervening absorption lines in the spectrum of the background quasar (QSOB) that are at the same redshift of the foreground quasar (QSOF). Here we report on optical spectroscopy, gathered at Gran Telescopio Canarias, of 14 QPPs. In 7 cases we find MgII absorption lines associated with the foreground quasar. Only for two cases line-of-sight absorptions (LOS) are revealed. These new observations complement our previous study performed on other 30 QPPs. A brief discussion of the properties of the intervening absorption lines associated with the foreground quasar for the full dataset is reported.

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Mongardi, C., M. Viel, V. D’Odorico, T. S. Kim, P. Barai, G. Murante, and P. Monaco. "Absorption systems at z ∼ 2 as a probe of the circum galactic medium: a probabilistic approach." Monthly Notices of the Royal Astronomical Society, May 18, 2018. http://dx.doi.org/10.1093/mnras/sty1283.

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Hopkins, Philip F., Iryna S. Butsky, Suoqing Ji, and Dušan Kereš. "A simple sub-grid model for cosmic ray effects on galactic scales." Monthly Notices of the Royal Astronomical Society, April 4, 2023. http://dx.doi.org/10.1093/mnras/stad976.

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Abstract Many recent numerical studies have argued that cosmic rays (CRs) from supernovae (SNe) or active galactic nuclei (AGN) could play a crucial role in galaxy formation, in particular by establishing a CR-pressure dominated circum-galactic medium (CGM). But explicit CR-magneto-hydrodynamics (CR-MHD) remains computationally expensive, and it is not clear whether those results can be applied to simulations that do not explicitly treat magnetic fields or resolved ISM phase structure. We therefore present an intentionally extremely-simplified ‘sub-grid’ model for CRs, which attempts to capture the key qualitative behaviors of greatest interest for those interested in simulations or semi-analytic models including some approximate CR effects on galactic (≳ kpc) scales, while imposing negligible computational overhead. The model is numerically akin to some recently-developed sub-grid models for radiative feedback, and allows for a simple constant parameterization of the CR diffusivity and/or streaming speed; it allows for an arbitrary distribution of sources (proportional to black hole accretion rates or star-particle SNe rates or gas/galaxy star formation rates), and interpolates between the limits where CRs escape the galaxies with negligible losses and those where CRs lose most of their energy catastrophically before escape (relevant in e.g. starburst galaxies). The numerical equations are solved trivially alongside gravity in most codes. We compare this to explicit CR-MHD simulations and discuss where the (many) sub-grid approximations break down, and what drives the major sources of uncertainty.

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Chen, Yaoxin, Yingzhong Xu, and Xi Kang. "Constraining galactic baryon cycle using the galaxy Stellar-to-Halo Mass Relations." Monthly Notices of the Royal Astronomical Society, December 12, 2022. http://dx.doi.org/10.1093/mnras/stac3628.

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Abstract Galaxies display several well-behaved scaling relations between their properties, such as the star formation rate-stellar mass relation (the main sequence) and the stellar mass-halo mass relation (SHMR). In principle, these scaling relations could imply different star formation histories (SFHs) of galaxies and different constraints on galaxy formation physics. In this paper, we derive the SFHs of galaxies by assuming that they always follow the SHMRs at different redshifts and use an empirical model to constrain key processes in their baryon cycle. It is found that, besides cold accretion due to halo growth, outflow of gas produced by stellar feedback has to be recycled to sustain the derived SFHs of galaxies. The recycled fraction is strongly affected by the baryon fraction in accreted low-mass haloes and the mass loading factor which quantifies the ratio between the galactic outflow rate and star formation rate. Our fiducial model predicts that around 20-60 per cent of outflow is recycled in ∼0.5–4 Gyrs, while simulations predict a slightly higher recycle fraction and a lower recycle time. We argue that strong constraints on the baryon cycle process can be obtained from future observation of the circum-galactic medium (CGM) of galaxies, such as the gas cooling rate of CGM. We also find that the implied SFHs from the SHMRs indicate that galaxies stay on the main sequences only for part of their lifetimes. Our model reproduces the evolution of the mass-metallicity relation as well.

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Hopkins, Philip F., Iryna S. Butsky, Georgia V. Panopoulou, Suoqing Ji, Eliot Quataert, Claude-André Faucher-Giguère, and Dušan Kereš. "First predicted cosmic ray spectra, primary-to-secondary ratios, and ionization rates from MHD galaxy formation simulations." Monthly Notices of the Royal Astronomical Society, July 1, 2022. http://dx.doi.org/10.1093/mnras/stac1791.

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Abstract We present the first simulations evolving resolved spectra of cosmic rays (CRs) from MeV-TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-MHD galaxy simulations with star formation and feedback. We utilize new numerical methods including terms often neglected in historical models, comparing Milky Way analogues with phenomenological scattering coefficients ν to Solar-neighborhood (LISM) observations (spectra, B/C, e+/e−, $\bar{p}/p$, 10Be/9Be, ionization, γ-rays). We show it is possible to reproduce observations with simple single-power-law injection and scattering coefficients (scaling with rigidity R), similar to previous (non-dynamical) calculations. We also find: (1) The circum-galactic medium in realistic galaxies necessarily imposes a ∼10 kpc CR scattering halo, influencing the required ν(R). (2) Increasing the normalization of ν(R) re-normalizes CR secondary spectra but also changes primary spectral slopes, owing to source distribution and loss effects. (3) Diffusive/turbulent reacceleration is unimportant and generally sub-dominant to gyroresonant/streaming losses, which are sub-dominant to adiabatic/convective terms dominated by ∼0.1 − 1 kpc turbulent/fountain motions. (4) CR spectra vary considerably across galaxies; certain features can arise from local structure rather than transport physics. (5) Systematic variation in CR ionization rates between LISM and molecular clouds (or Galactic position) arises naturally without invoking alternative sources. (6) Abundances of CNO nuclei require most CR acceleration occurs around when reverse shocks form in SNe, not in OB wind bubbles or later Sedov-Taylor stages of SNe remnants.

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Hopkins, Philip F., T. K. Chan, Suoqing Ji, Cameron B. Hummels, Dušan Kereš, Eliot Quataert, and Claude-André Faucher-Giguére. "Cosmic-Ray Driven Outflows to Mpc Scales from L* Galaxies." Monthly Notices of the Royal Astronomical Society, November 28, 2020. http://dx.doi.org/10.1093/mnras/staa3690.

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Abstract We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (Mhalo ≳ 1011 M⊙), low-redshift (z ≲ 1 − 2) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive halos “traps” galactic outflows near the disk, so they recycle. With CRs injected in supernovae as modeled here, the low-pressure halo allows “escape” and CR pressure gradients continuously accelerate this material well into the IGM in “fast” outflows, while lower-density gas at large radii is accelerated in-situ into “slow” outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disk to >Mpc. The CR-driven outflows are primarily cool (T ∼ 105 K) and low-velocity. All of these effects weaken and eventually vanish at lower halo masses (≲ 1011 M⊙) or higher redshifts (z ≳ 1 − 2), reflecting the ratio of CR to thermal+gravitational pressure in the outer halo. We present a simple analytic model which explains all of the above phenomena. We caution that these predictions may depend on uncertain CR transport physics.

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Liu, Yao, Ming Zhu, Haiyang Yu, Mei Ai, Peng Jiang, Siqi Liu, and Lixia Yuan. "FAST discovery of long tidal tails in NGC 4490/85." Monthly Notices of the Royal Astronomical Society, April 28, 2023. http://dx.doi.org/10.1093/mnras/stad1281.

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Abstract We report the discovery of a 100 kpc H i tail in the merging galaxy pair NGC 4490/85 detected by the Five-Hundred-meter Aperture Spherical radio Telescope (FAST). The tidal tails extended in both the south and north directions, and they are much longer than that reported previously based on the VLA interferometric maps. The NGC 4490/85 is surrounded by a large gas envelope, and a starburst low metallicity dwarf galaxy MAPS 1231+42 is found to be connected with the gas envelope, indicating that galaxy interaction trigged the intense star formation in it. Based on the fact that the metallicity in MAPS 1231+42 is one order of magnitude lower than that in the two disks of NGC 4490 and NGC 4485, we speculate that the gas near this galaxy should be primordial and could be due to gas inflow from the circum-galactic medium (CGM). We also found a collimated gas component pointing at a nearby dwarf galaxy KK 149, suggesting that this galaxy might also be interacting with the NGC 4490 pair. We discuss the possible origin of the long tidal tails and the extended gas envelope in this merging system based on the new data from FAST.

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Cadiou, Corentin, Yohan Dubois, and Christophe Pichon. "Gravitational torques dominate the dynamics of accreted gas at z > 2." Monthly Notices of the Royal Astronomical Society, June 17, 2022. http://dx.doi.org/10.1093/mnras/stac1663.

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Abstract Galaxies form from the accretion of cosmological infall of gas. In the high redshift Universe, most of this gas infall is expected to be dominated by cold filamentary flows which connect deep down inside haloes, and, hence, to the vicinity of galaxies. Such cold flows are important since they dominate the mass and angular momentum acquisition that can make up rotationally-supported disks at high-redshifts. We study the angular momentum acquisition of gas into galaxies, and in particular, the torques acting on the accretion flows, using hydrodynamical cosmological simulations of high-resolution zoomed-in haloes of a few $10^{11}\, \rm M_\odot$ at z = 2. Torques can be separated into those of gravitational origin, and hydrodynamical ones driven by pressure gradients. We find that coherent gravitational torques dominate over pressure torques in the cold phase, and are hence responsible for the spin-down and realignment of this gas. Pressure torques display small-scale fluctuations of significant amplitude, but with very little coherence on the relevant galaxy or halo-scale that would otherwise allow them to effectively re-orientate the gas flows. Dark matter torques dominate gravitational torques outside the galaxy, while within the galaxy, the baryonic component dominates. The circum-galactic medium emerges as the transition region for angular momentum re-orientation of the cold component towards the central galaxy’s mid-plane.

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Scholtz, J., R. Maiolino, G. C. Jones, and S. Carniani. "Evidence of extended cold molecular gas and dust halos around z ∼ 2.3 Extremely Red Quasars with ALMA." Monthly Notices of the Royal Astronomical Society, January 2, 2023. http://dx.doi.org/10.1093/mnras/stac3787.

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Abstract Large-scale outflows are believed to be an important mechanism in the evolution of galaxies. We can determine the impact of these outflows by studying either current galaxy outflows and their effect in the galaxy or by studying the effect of past outflows on the gas surrounding the galaxy. In this work, we examine the CO(7-6), [C i] ($^{3} \rm P_{1} \rightarrow {\rm ^3 P}_{0}$), H2O 211–202 and dust continuum emission of 15 extremely red quasars (ERQs) at z∼2.3 using ALMA. By investigating the radial surface brightness profiles of both the individual sources and the stacked emission, we detect extended cold gas and dust emission on scales of ∼14 kpc in CO(7-6), [C i](2-1), and dust continuum. This is the first time that the presence of a large amount of molecular gas was detected on large, circum-galactic medium scales around quasar host galaxies using [C i] extended emission. We estimate the dust and molecular gas mass of these halos to be 107.6 and 1010.6 M⊙, indicating significant dust and molecular gas reservoirs around these extreme quasars. By estimating the timescale at which this gas can reach these distances by molecular gas outflows (7-32 Myr), we conclude that these halos are a relic of past AGN or starburst activity, rather than an effect of the current episode of extreme quasar activity.

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Journal articles on the topic 'Circum-galactic medium'

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