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تسجيل مستخدم جديدFiguring Out Gas & Galaxies in Enzo (FOGGIE). II. Emission from the z=3 Circumgalactic Medium
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Observing the circumgalactic medium (CGM) in emission provides 3D maps of the spatial and kinematic extent of the gas that fuels galaxies and receives their feedback. We present mock emission-line maps of highly resolved CGM gas from the FOGGIE project (Figuring Out Gas & Galaxies in Enzo) and link these maps back to physical and spatial properties of the gas. By increasing the spatial resolution alone, the total luminosity of the line emission increases by an order of magnitude. This increase arises in the abundance of dense small-scale structure resolved when the CGM gas is simulated to < 100 pc scales. Current integral field unit instruments like KCWI and MUSE should be able to detect the brightest knots and filaments of such emission, and from this to infer the bulk kinematics of the CGM gas with respect to the galaxy. We conclude that accounting for small-scale structure well below the level of instrument spatial resolution is necessary to properly interpret such observations in terms of the underlying gas structure driving observable emission.
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We present simulations from the new Figuring Out Gas & Galaxies in Enzo (FOGGIE) project. In contrast to most extant simulations of galaxy formation, which concentrate computational resources on galactic disks and spheroids with fluid and particle el
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The circumgalactic medium (CGM) of the Milky Way is mostly obscured by nearby gas in position-velocity space because we reside inside the Galaxy. Substantial biases exist in most studies on the Milky Ways CGM that focus on easier-to-detect high-veloc
ity gas. With mock observations on a Milky-Way analog from the FOGGIE simulation, we investigate four observational biases related to the Milky Ways CGM. First, QSO absorption-line studies probe a limited amount of the CGM mass: only 35% of the mass is at high Galactic latitudes $|b|>20$ degrees, of which only half is moving at $|v_{rm LSR}|gtrsim100$ km s$^{-1}$. Second, the inflow rate ($dot{M}$) of the cold gas observable in HI 21cm is reduced by a factor of $sim10$ as we switch from the local standard of rest to the galaxys rest frame; meanwhile $dot{M}$ of the cool and warm gas does not change significantly. Third, OVI and NV are promising ions to probe the Milky Ways outer CGM ($rgtrsim$15 kpc), but CIV may be less sensitive. Lastly, the scatter in ion column density is a factor of 2 higher if the CGM is observed from inside-out than from external views because of the gas radial density profile. Our work highlights that observations of the Milky Ways CGM, especially those using HI 21cm and QSO absorption lines, are highly biased. We demonstrate that these biases can be quantified and calibrated through synthetic observations with simulated Milky-Way analogs.
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a emitters recently obtained with the MUSE instrument (halo masses ~10^10-10^11 solar masses). We show that supernova feedback has a significant impact on both the inflowing and outflowing circumgalactic medium by driving outflows, reducing diffuse inflow rates, and by increasing the neutral fraction of inflowing gas. By temporally stacking simulation outputs we find that significant net mass exchange occurs between inflowing and outflowing phases: none of the phases are mass-conserving. In particular, we find that the mass in neutral outflowing hydrogen declines exponentially with radius as gas flows outwards from the halo centre. This is likely caused by a combination of both fountain-like cycling processes and gradual photo/collisional ionization of outflowing gas. Our simulations do not predict the presence of fast-moving neutral outflows in the CGM. Neutral outflows instead move with modest radial velocities (~ 50 kms^-1), and the majority of the kinetic energy is associated with tangential rather than radial motion.
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