scholarly journals Deviations from hydrostatic equilibrium in the circumgalactic medium: spinning hot haloes and accelerating flows

2018 ◽  
Vol 480 (3) ◽  
pp. 2963-2975 ◽  
Author(s):  
Benjamin D Oppenheimer
Keyword(s):  
Hydrostatic Equilibrium ◽  
Circumgalactic Medium ◽  
Accelerating Flows

scholarly journals Properties of the simulated circumgalactic medium

2020 ◽  
Vol 493 (1) ◽  
pp. 1461-1478 ◽  
Author(s):  
Cassandra Lochhaas ◽  
Greg L Bryan ◽  
Yuan Li ◽  
Miao Li ◽  
Drummond Fielding
Keyword(s):  
Galaxy Formation ◽  
Pressure Support ◽  
Initial Conditions ◽  
Dynamic Pressure ◽  
Hydrostatic Equilibrium ◽  
Central Galaxy ◽  
Galaxy Formation And Evolution ◽  
Effective Dynamic ◽  
Formation And Evolution ◽  
Circumgalactic Medium

ABSTRACT The circumgalactic medium (CGM) is closely linked to galaxy formation and evolution, but difficult to characterize observationally and typically poorly resolved in cosmological simulations. We use spherically symmetric, idealized, high-resolution simulations of the CGM in $10^{12}$ and $10^{11}\, \mathrm{M}_\odot$ dark matter haloes to characterize the gas pressure, turbulent and radial velocities, and degree of thermal and effective dynamic pressure support in the overall CGM as well as in its high- and low-temperature phases. We find that the $10^{12}\, \mathrm{M}_\odot$ halo contains a CGM mostly formed of a hot gas halo in hydrostatic equilibrium out of which cold gas condenses and falls on to the central galaxy, while the $10^{11}\, \mathrm{M}_\odot$ halo’s CGM is not in hydrostatic equilibrium, has a wider spread of properties at a given galactocentric radius, does not have a clear separation of hot and cold phases, and is dominated by bulk motions. We also find that the degree of pressure support in the $10^{11}\, \mathrm{M}_\odot$ halo is strongly dependent on the parameters of the galactic winds of the central galaxy. These results promote the idea that there is no ‘average’ CGM and care must be taken when setting the initial conditions for a small-box simulation of a patch of the CGM.

scholarly journals Characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with SDSS DR16

2021 ◽  
Vol 504 (1) ◽  
pp. 65-88
Author(s):  
Abhijeet Anand ◽  
Dylan Nelson ◽  
Guinevere Kauffmann
Keyword(s):  
Formation Rate ◽  
Sloan Digital Sky Survey ◽  
Gas Absorption ◽  
Dark Matter Halo ◽  
Star Forming ◽  
Sky Survey ◽  
Optical Continuum ◽  
Circumgalactic Medium ◽  
Emission Line Galaxies ◽  
Red Galaxies

ABSTRACT In order to study the circumgalactic medium (CGM) of galaxies we develop an automated pipeline to estimate the optical continuum of quasars and detect intervening metal absorption line systems with a matched kernel convolution technique and adaptive S/N criteria. We process ∼ one million quasars in the latest Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and compile a large sample of ∼ 160 000 Mg ii absorbers, together with ∼ 70 000 Fe ii systems, in the redshift range 0.35 < zabs < 2.3. Combining these with the SDSS DR16 spectroscopy of ∼1.1 million luminous red galaxies (LRGs) and ∼200 000 emission line galaxies (ELGs), we investigate the nature of cold gas absorption at 0.5 < z < 1. These large samples allow us to characterize the scale dependence of Mg ii with greater accuracy than in previous work. We find that there is a strong enhancement of Mg ii absorption within ∼50 kpc of ELGs, and the covering fraction within 0.5rvir of ELGs is 2–5 times higher than for LRGs. Beyond 50 kpc, there is a sharp decline in Mg ii for both kinds of galaxies, indicating a transition to the regime where the CGM is tightly linked with the dark matter halo. The Mg ii-covering fraction correlates strongly with stellar mass for LRGs, but weakly for ELGs, where covering fractions increase with star formation rate. Our analysis implies that cool circumgalactic gas has a different physical origin for star-forming versus quiescent galaxies.

scholarly journals Efficiency of thermal conduction in a magnetized circumgalactic medium

2021 ◽  
Vol 502 (1) ◽  
pp. 1263-1278
Author(s):  
Richard Kooij ◽  
Asger Grønnow ◽  
Filippo Fraternali
Keyword(s):  
Magnetic Field ◽  
Thermal Conduction ◽  
Large Temperature ◽  
Gas Condensation ◽  
Circumgalactic Medium ◽  
Field Lines ◽  
Gas Accretion ◽  
Cloud Evolution ◽  
The Magnetic Field ◽  
Cold Gas

ABSTRACT The large temperature difference between cold gas clouds around galaxies and the hot haloes that they are moving through suggests that thermal conduction could play an important role in the circumgalactic medium. However, thermal conduction in the presence of a magnetic field is highly anisotropic, being strongly suppressed in the direction perpendicular to the magnetic field lines. This is commonly modelled by using a simple prescription that assumes that thermal conduction is isotropic at a certain efficiency f < 1, but its precise value is largely unconstrained. We investigate the efficiency of thermal conduction by comparing the evolution of 3D hydrodynamical (HD) simulations of cold clouds moving through a hot medium, using artificially suppressed isotropic thermal conduction (with f), against 3D magnetohydrodynamical (MHD) simulations with (true) anisotropic thermal conduction. Our main diagnostic is the time evolution of the amount of cold gas in conditions representative of the lower (close to the disc) circumgalactic medium of a Milky-Way-like galaxy. We find that in almost every HD and MHD run, the amount of cold gas increases with time, indicating that hot gas condensation is an important phenomenon that can contribute to gas accretion on to galaxies. For the most realistic orientations of the magnetic field with respect to the cloud motion we find that f is in the range 0.03–0.15. Thermal conduction is thus always highly suppressed, but its effect on the cloud evolution is generally not negligible.

scholarly journals The impact of galactic feedback on the circumgalactic medium

2015 ◽  
Vol 448 (1) ◽  
pp. 895-909 ◽  
Author(s):  
Joshua Suresh ◽  
Simeon Bird ◽  
Mark Vogelsberger ◽  
Shy Genel ◽  
Paul Torrey ◽  
...  
Keyword(s):  
Circumgalactic Medium ◽  
The Impact ◽  
Galactic Feedback

scholarly journals The 2017 May 20th stellar occultation by the elongated centaur (95626) 2002 GZ32

2020 ◽  
Author(s):  
P Santos-Sanz ◽  
J L Ortiz ◽  
B Sicardy ◽  
G Benedetti-Rossi ◽  
N Morales ◽  
...  
Keyword(s):  
Rotation Period ◽  
Hydrostatic Equilibrium ◽  
Homogeneous Body ◽  
Ellipsoidal Shape ◽  
Stellar Occultation ◽  
Path Prediction ◽  
Error Bars ◽  
Geometric Albedo ◽  
Radiometric Technique ◽  
Broad Region

Abstract We predicted a stellar occultation of the bright star Gaia DR1 4332852996360346368 (UCAC4 385-75921) (mV= 14.0 mag) by the centaur 2002 GZ32 for 2017 May 20th. Our latest shadow path prediction was favourable to a large region in Europe. Observations were arranged in a broad region inside the nominal shadow path. Series of images were obtained with 29 telescopes throughout Europe and from six of them (five in Spain and one in Greece) we detected the occultation. This is the fourth centaur, besides Chariklo, Chiron and Bienor, for which a multi-chord stellar occultation is reported. By means of an elliptical fit to the occultation chords we obtained the limb of 2002 GZ32 during the occultation, resulting in an ellipse with axes of 305 ± 17 km × 146 ± 8 km. From this limb, thanks to a rotational light curve obtained shortly after the occultation, we derived the geometric albedo of 2002 GZ32 (pV = 0.043 ± 0.007) and a 3-D ellipsoidal shape with axes 366 km × 306 km × 120 km. This shape is not fully consistent with a homogeneous body in hydrostatic equilibrium for the known rotation period of 2002 GZ32. The size (albedo) obtained from the occultation is respectively smaller (greater) than that derived from the radiometric technique but compatible within error bars. No rings or debris around 2002 GZ32 were detected from the occultation, but narrow and thin rings cannot be discarded.

scholarly journals Challenges and Techniques for Simulating Line Emission

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 100 ◽  
Author(s):  
Karen Olsen ◽  
Andrea Pallottini ◽  
Aida Wofford ◽  
Marios Chatzikos ◽  
Mitchell Revalski ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
Line Emission ◽  
Emission Lines ◽  
Synthetic Spectra ◽  
Recent Advances ◽  
The Future ◽  
Important Quality ◽  
Circumgalactic Medium

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.

scholarly journals THE BIMODAL METALLICITY DISTRIBUTION OF THE COOL CIRCUMGALACTIC MEDIUM ATz≲ 1

2013 ◽  
Vol 770 (2) ◽  
pp. 138 ◽  
Author(s):  
N. Lehner ◽  
J. C. Howk ◽  
T. M. Tripp ◽  
J. Tumlinson ◽  
J. X. Prochaska ◽  
...  
Keyword(s):  
Circumgalactic Medium ◽  
Metallicity Distribution
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