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feedback/report/report.tex
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@ -19,6 +19,8 @@
\newcommand{\LCDM}{$\Lambda$CDM}
\newcommand{\apj}{ApJ}
\newcommand{\apjl}{ApJL}
\newcommand{\mnras}{MNRAS}
\newcommand{\apjs}{ApJS}
\newcommand{\nat}{Nature}
\newcommand{\aapr}{AAPR}
@ -40,6 +42,7 @@
Chaotic cold accretion is a likely mechanism by which AGN feedback occurs, allowing the AGN to ``cycle'' through a process of heating and cooling that reaches equilibrium with the host galaxy, until available cold gases are consumed.
Modeling AGN feedback presents significant challenges, but has improved upon observational predictions derived from the \LCDM\ cosmology-based Millennium Simulation.
Only a few subclasses of AGN have been studied regarding their feedback mechanisms, and with only the most rudimentary first-principle approaches, but the necessity of including AGN feedback to correctly predict colors and luminosities of galaxy mergers and quasars seems increasingly likely.
Two possible future models are also considered, one a more rigorous derivation involving chaotic cold accretion, and the other a "bubble" model of heated outflows.
@ -223,7 +226,7 @@
\begin{figure}
\centering
\includegraphics[width=.8\textwidth]{colors.pdf}
\includegraphics[width=.5\textwidth]{colors.pdf}
\caption{
Bimodal color evolution for gas-rich mergers with black hole accretion.
Symbols on the tracks are spaced 0.
@ -256,36 +259,45 @@
\dot M_{cool} \approx 6.7\times10^{-3} \frac{L}{c^{2}},
\end{equation}
where $L_x$ is the luminosity escaping the AGN and c the adiabatic sound speed of the outflowing gas. A number of complications enter into this model, especially with entrainment of gases as outflows leave the AGN. The out-flow velocity can be derived as a function of this entrainment and compared to observations, seen in Figure~\ref{fig:CCAvelocity}. This model agrees with the UFO observations better than the effective subresolution model, and by a significant amount.
where $L_x$ is the luminosity escaping the AGN and c the adiabatic sound speed of the outflowing gas. A number of complications enter into this model, especially with entrainment of gases as outflows leave the AGN. The out-flow velocity can be derived as a function of this entrainment and compared to observations, seen in Figure~\ref{fig:modelcompare}. This model agrees with the UFO observations better than the effective subresolution model, and by a significant amount.
\begin{figure}
\centering
\includegraphics[width=0.48\textwidth]{CCAvelocity.pdf}
\caption{Outflow velocity as a function of radial distance from the SMBH. The green dotted line shows the purely momentum-driven effective subresolution model. The red line is the velocity for the unified X-ray UFO plus warm absorber data reported by Tombesi et al. (2013). The shaded regions are UFO generated regions where most of the inflow mass is ejected. At larger radii, UFO entrains more mass, slowing down. This new model agrees more strongly with the UFO observations than the effective subresolution model.}
\includegraphics[width=.48\textwidth]{CCAvelocity.pdf}
\includegraphics[width=.48\textwidth]{CD_stage_z-0_S1.pdf}
\caption{
Left:
Outflow velocity as a function of radial distance from the SMBH.
The green dotted line shows the purely momentum-driven effective subresolution model.
The red line is the velocity for the unified X-ray UFO plus warm absorber data reported by Tombesi et al. (2013).
The shaded regions are UFO generated regions where most of the inflow mass is ejected. At larger radii, UFO entrains more mass, slowing down.
This new model agrees more strongly with the UFO observations than the effective subresolution model.
Right:
Formation redshifts of the stars belonging to a model galaxy.
The white histogram has only cooling and star formation, and it can be seen that star formation continues until the end of the simulation, which conflicts with observations.
The grey and hatched histograms show how stellar formation times change when ``bubble'' heating is switched on, under two different models of this heating developed by Springel et al.
This heating suppresses any central star formation for z $<$ 0.25 completely, and in both cases suppresses the star formation enough to not be discounted as future hypotheses.
\cite{2006MNRAS.366..397S}
}
\label{fig:modelcompare}
\end{figure}
Another approach is to treat AGN feedback as the periodic release of heating ``bubbles''.
Figure~\ref{fig:bubbles} demonstrates the concept.
In this model, luminous winds drive the creation of pockets of hot gases that are blown into the regions surrounding the SMBH.
This method has not been examined yet against empirical data, but at least Figure~\ref{fig:bubbletest} indicates that the model does regulate star formation rates as expected.
This method has not been examined yet against empirical data, but at least Figure~\ref{fig:modelcompare} indicates that the model does regulate star formation rates as expected.
\cite{2006MNRAS.366..397S}
\begin{figure}
\includegraphics[width=.48\textwidth]{MM_bubbles-1.1-45.eps}
\includegraphics[width=.48\textwidth]{MM_bubbles-1.1-52.eps}
\includegraphics[width=.48\textwidth]{MM_bubbles-1.1-59.eps}
\includegraphics[width=.48\textwidth]{MM_bubbles-1.1-75.eps}
\includegraphics[width=.48\textwidth]{MM_bubbles-1-1-45.pdf}
\includegraphics[width=.48\textwidth]{MM_bubbles-1-1-53.pdf}
\includegraphics[width=.48\textwidth]{MM_bubbles-1-1-59.pdf}
\includegraphics[width=.48\textwidth]{MM_bubbles-1-1-75.pdf}
\caption{
Emission-weighted temperature maps of a galaxy simulation involving AGN heating by non-uniform gases (``bubbles'') after a major merger event, at several red shift epochs.
\cite{2006MNRAS.366..397S} }
\end{figure}
\begin{figure}
\includegraphics[width=.6\textwidth]{CD_stage_z.0_S1.eps}
\caption{
Formation redshifts of the stars belonging to a model galaxy. The white histogram has only cooling and star formation, and it can be seen that star formation continues until the end of the simulation, which conflicts with observations. The grey and hatched histograms show stellar formation times when ``bubble'' heating is switched on, under two different models of this heating developed by Springel et al. This heating suppresses any central star formation for z < 0.25 completely, and in both cases suppresses the star formation enough to not be discounted as future hypotheses. \cite{2006MNRAS.366..397S}
}
\label{fig:bubbles}
\end{figure}