Galaxy formation with local photoionization feedback – I. Methods

Kannan, Rahul; Stinson, Greg; Macciò, Andrea V.; Hennawi, J.; Woods, R. M.; Wadsley, James; Shen, Sijing; Robitaille, Thomas; Cantalupo, Sebastiano; Quinn, Thomas; Christensen, Charlotte

doi:10.1093/mnras/stt2098

Cited by 55 publications

(66 citation statements)

References 55 publications

(92 reference statements)

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“…To estimate the contribution of local SF to the ionizing spectrum we follow Kannan et al (2014), who assumed the SED of a 5 Myr old stellar population and an escape fraction of f esc = 0.05 (black curve in fig. 1 there).…”

Section: Uncertainty In the Ionizing Spectrummentioning

confidence: 99%

A Universal Density Structure for Circumgalactic Gas

Stern

Hennawi

Prochaska

et al. 2016

ApJ

130

160

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We develop a new method to constrain the physical conditions in the cool (∼ 10 4 K) circumgalactic medium (CGM) from measurements of ionic column densities, by assuming that the cool CGM spans a large range of gas densities and that small high-density clouds are hierarchically embedded in large low-density clouds. The new method combines the information available from different sightlines during the photoionization modeling, thus yielding tighter constraints on CGM properties compared to traditional methods which model each sightline individually. Applying this new technique to the COS-Halos survey of low-redshift ∼ L * galaxies, we find that we can reproduce all observed ion columns in all 44 galaxies in the sample, from the low-ions to O vi, with a single universal density structure for the cool CGM. The gas densities span the range 50 ρ/ρ b 5 × 10 5 (ρ b is the cosmic mean), while the physical size of individual clouds scales as ∼ ρ −1 , from ≈ 35 kpc of the low density O vi clouds to ≈ 6 pc of the highest density low-ion clouds. The deduced cloud sizes are too small for this density structure to be driven by self-gravity, thus its physical origin is unclear. The implied cool CGM mass within the virial radius is (1.3 ± 0.4) × 10 10 M (∼1% of the halo mass), distributed rather uniformly over the four decades in density. The mean cool gas density profile scales as R −1.0±0.3 , where R is the distance from the galaxy center. We construct a 3D model of the cool CGM based on our results, which we argue provides a benchmark for the CGM structure in hydrodynamic simulations. Our results can be tested by measuring the coherence scales of different ions.

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Section: Uncertainty In the Ionizing Spectrummentioning

confidence: 99%

A Universal Density Structure for Circumgalactic Gas

Stern

Hennawi

Prochaska

et al. 2016

ApJ

130

160

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“…With metal cooling, the gas can in principle cool non-adiabatically to ∼ 10 K. We do not model the change in the metal cooling rate with the local radiation flux, which may affect galaxy evolution (e.g. Cantalupo 2010; Kannan et al 2014b). In future work, we will consider more realistic metal cooling, which takes the local radiation flux into account.…”

Section: Gas Thermochemistrymentioning

confidence: 99%

Galaxies that shine: radiation-hydrodynamical simulations of disc galaxies

Rosdahl¹,

Schaye²,

Teyssier³

et al. 2015

Monthly Notices of the Royal Astronomical Society

119

101

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Radiation feedback is typically implemented using subgrid recipes in hydrodynamical simulations of galaxies. Very little work has so far been performed using radiationhydrodynamics (RHD), and there is no consensus on the importance of radiation feedback in galaxy evolution. We present RHD simulations of isolated galaxy disks of different masses with a resolution of 18 pc. Besides accounting for supernova feedback, our simulations are the first galaxy-scale simulations to include RHD treatments of photo-ionisation heating and radiation pressure, from both direct optical/UV radiation and multi-scattered, re-processed infrared (IR) radiation. Photo-heating smooths and thickens the disks and suppresses star formation about as much as the inclusion of ("thermal dump") supernova feedback does. These effects decrease with galaxy mass and are mainly due to the prevention of the formation of dense clouds, as opposed to their destruction. Radiation pressure, whether from direct or IR radiation, has little effect, but for the IR radiation we show that its impact is limited by our inability to resolve the high optical depths for which multi-scattering becomes important. While artificially boosting the IR optical depths does reduce the star formation, it does so by smoothing the gas rather than by generating stronger outflows. We conclude that although higher-resolution simulations, and potentially also different supernova implementations, are needed for confirmation, our findings suggest that radiation feedback is more gentle and less effective than is often assumed in subgrid prescriptions.

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“…In particular, local radiation fields (see Kannan et al 2014 for a first study along these lines) and non-equilibrium effects (Oppenheimer & Schaye 2013) clearly matter, yet they are typically ignored in cosmological runs. A proper modeling of the cooling rates may also lower the amount of feedback required to offset excessive overcooling of gas.…”

Section: Caveatsmentioning

confidence: 99%

The Argo simulation – I. Quenching of massive galaxies at high redshift as a result of cosmological starvation

Feldmann¹,

Mayer²

2014

Monthly Notices of the Royal Astronomical Society

119

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Observations show a prevalence of high redshift galaxies with large stellar masses and predominantly passive stellar populations. A variety of processes have been suggested that could reduce the star formation in such galaxies to observed levels, including quasar mode feedback, virial shock heating, or galactic winds driven by stellar feedback. However, the main quenching mechanisms have yet to be identified. Here we study the origin of star formation quenching using Argo, a cosmological, hydrodynamical zoom-in simulation that follows the evolution of a massive galaxy at z 2. This simulation adopts the same sub-grid recipes of the Eris simulations, which have been shown to form realistic disk galaxies, and, in one version, adopts also a mass and spatial resolution identical to Eris. The resulting galaxy has properties consistent with those of observed, massive (M * ∼ 10 11 M ) galaxies at z ∼ 2 and with abundance matching predictions. Our models do not include AGN feedback indicating that supermassive black holes likely play a subordinate role in determining masses and sizes of massive galaxies at high z. The specific star formation rate (sSFR) of the simulated galaxy matches the observed M * -sSFR relation at early times. This period of smooth stellar mass growth comes to a sudden halt at z = 3.5 when the sSFR drops by almost an order of magnitude within a few hundred Myr. The suppression is initiated by a leveling off and a subsequent reduction of the cool gas accretion rate onto the galaxy, and not by feedback processes. This "cosmological starvation" occurs as the parent dark matter halo switches from a fast collapsing mode to a slow accretion mode. Additional mechanisms, such as perhaps radio mode feedback from an AGN, are needed to quench any residual star formation of the galaxy and to maintain a low sSFR until the present time.

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Galaxy formation with local photoionization feedback – I. Methods

Cited by 55 publications

References 55 publications

A Universal Density Structure for Circumgalactic Gas

A Universal Density Structure for Circumgalactic Gas

Galaxies that shine: radiation-hydrodynamical simulations of disc galaxies

The Argo simulation – I. Quenching of massive galaxies at high redshift as a result of cosmological starvation

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