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trunk/MagicSoft/GC-Proposal/GC.tex
r6780 r6781 105 105 \section{Introduction} 106 106 107 %<<<<<<< GC.tex 108 109 %The Galactic Center (GC) region contains many unusual objects which may be responsible for the high energy processes generation gamma rays \cite{Aharonian2005,Atoyan2004,Horns2004}. The GC is rich in massive stellar clusters with up to 100 OB stars \cite{GC_environment}, immersed in a dense gas within the volume of 300 pc and the mass of $2.7 \cdot 10^7 M_{\odot}$, young supernova remnants e.g. G0.570-0.018 or Sgr A East, and nonthermal radio arcs. The dynamical center of the Milky Way is associated with the compact radio source Sgr A$^*$, which is believed to be a massive black hole \cite{GC_black_hole,Melia2001}. An overview of the sources in the GC region is given in Figure \ref{fig:GC_sources}. Some data about the Galactic Center are summarized in Table \ref{table:GC_properties}. 110 %======= 107 111 108 The Galactic Center (GC) region contains many unusual objects which may be 112 109 responsible for the high energy processes generating gamma rays … … 114 111 clusters with up to 100 OB stars \cite{GC_environment}, immersed in a dense 115 112 gas within a radius of 300 pc and the mass of $2.7 \cdot 10^7 M_{\odot}$, 116 young supernova remnants e.g. G0.570-0.018 or Sgr A East, and nonthermal radio arcs. The dynamical center of the Milky Way is associated with the compact radio source Sgr A$^*$, which is believed to be a massive black hole \cite{GC_black_hole,Melia2001}. An overview of the sources in the GC region is given in Figure \ref{fig:GC_sources}. Some data about the G alactic Centerare summarized in Table \ref{table:GC_properties}.117 %>>>>>>> 1.15 113 young supernova remnants e.g. G0.570-0.018 or Sgr A East, and nonthermal radio arcs. The dynamical center of the Milky Way is associated with the compact radio source Sgr A$^*$, which is believed to be a massive black hole \cite{GC_black_hole,Melia2001}. An overview of the sources in the GC region is given in Figure \ref{fig:GC_sources}. Some data about the GC are summarized in Table \ref{table:GC_properties}. 114 118 115 119 116 \begin{table}[h]{\normalsize\center … … 121 118 \hline 122 119 (RA, dec), epoch J2000.0 & $(17^h45^m12^s,-29.01$ deg) 123 \\ heliocentric distance & $8\pm0.4$ kpc \cite{Eisenhauer2003 }120 \\ heliocentric distance & $8\pm0.4$ kpc \cite{Eisenhauer2003, ApJ 597(2003)L121} 124 121 (1 deg = 140 pc) 125 122 \\ mass of the black hole & $2\pm0.5 \cdot 10^6 M_{\odot}$ … … 142 139 In fact, EGRET has detected a strong source in direction of the GC, 143 140 3 EG J1745-2852 \cite{GC_egret}, which has a broken power law spectrum 144 extending up to at least 10 GeV, with the index1.3 below the break at a few141 extending up to at least 10 GeV, with a spectral index of 1.3 below the break at a few 145 142 GeV. Assuming a distance of 8.5 kpc, the gamma ray luminosity of this source 146 143 is very large $~2.2 \cdot 10^{37} \mathrm{erg}/\mathrm{s}$, which is 147 144 equivalent to about 10 Crab pulsars. An independent analysis of the EGRET data 148 \cite{Hooper2002} indicates a source position, excluded beyond 99.9 \% 149 as the GC. 145 \cite{Hooper2002, A&A 335 (1998) 161} indicates a point source whose position is different from the GC at a confidence level beyond 99.9 \%. 150 146 151 147 Up to now, the GC has been observed at … … 154 150 spectra by the other IACTs while Figure \ref{fig:GC_source_location} shows the 155 151 different reconstructed positions of the GC source. Recently a second TeV 156 gamma source only about 1 degree away from the G alactic Centerhas been152 gamma source only about 1 degree away from the GC has been 157 153 discovered \cite{SNR_G09+01}. Its integral flux above 200 GeV represents about 158 2\% of the gamma flux from the Crab nebula with a photon-index of about 2.4.154 2\% of the gamma flux from the Crab nebula with a spectral index of about 2.4. 159 155 160 156 \begin{figure}[h!] … … 162 158 \includegraphics[totalheight=6cm]{sgr_figure4.eps} 163 159 \end{center} 164 \caption[Gamma flux from GC.]{The observed VHE gamma flux with the other IACTs andthe EGRET satellite \cite{GC_hess}.} \label{fig:GC_gamma_flux}160 \caption[Gamma flux from GC.]{The VHE gamma flux as observed by the other IACTs and by the EGRET satellite \cite{GC_hess}.} \label{fig:GC_gamma_flux} 165 161 \end{figure} 166 162 … … 170 166 \includegraphics[totalheight=8cm]{gc_legend.eps} 171 167 \end{center} 172 \caption[Gamma flux from GC.]{The observed VHE source locations withthe other IACTs \cite{Horns2004}.} \label{fig:GC_source_location}168 \caption[Gamma flux from GC.]{The source locations as measured by the other IACTs \cite{Horns2004}.} \label{fig:GC_source_location} 173 169 \end{figure} 174 170 175 The di fferent reconstructed spectra in VHE gammascould indicate inter-calibration problems between the IACTs, a source variability of the order of one year could be due to the different regions in which the signal is integrated.171 The discrepancies between the measured flux spectra could indicate inter-calibration problems between the IACTs, a source variability of the order of one year could be due to the different regions in which the signal is integrated. 176 172 177 173 … … 179 175 \section{Investigators and Affiliations} 180 176 181 The investigators of the proposed observations of the G alactic Centerare stated in Table \ref{table:GC_investigators} together with their assigned analysis tasks. All other interested members of the MAGIC collaboration are invited to join these efforts.177 The investigators of the proposed observations of the GC are stated in Table \ref{table:GC_investigators} together with their assigned analysis tasks. All other interested members of the MAGIC collaboration are invited to join these efforts. 182 178 183 179 … … 198 194 \end{tabular} 199 195 } 200 \caption{The investigators and assigned tasks.}\label{table:GC_investigators}}}196 \caption{The investigators and the assigned tasks.}\label{table:GC_investigators}}} 201 197 \end{table} 202 198 … … 254 250 \subsubsection{Hadronic Models} 255 251 256 One scenario is related to protons accelerated to about $10^{18}$ eV \cite{Aharonian2005}. These protons produce gamma rays via photo-meson processes. This scenario also predicts detectable fluxes of $10^{18}$ eV neutrons and perhaps gamma rays and neutrinos. A hint of an excess of highest energy neutrons from the galactic centerhas been reported in \cite{Hayashida1999}.252 One scenario is related to protons accelerated to about $10^{18}$ eV \cite{Aharonian2005}. These protons produce gamma rays via photo-meson processes. This scenario also predicts detectable fluxes of $10^{18}$ eV neutrons and perhaps gamma rays and neutrinos. A hint of an excess of highest energy neutrons from the GC has been reported in \cite{Hayashida1999}. 257 253 258 254 TeV gamma rays can also be produced by significantly lower energy protons, accelerated by the electric filed close to the gravitational radius or by strong shocks in the accretion disk. In this case the gamma-ray production is dominated by interactions of $10^{13}$ eV protons with the accretion plasma. This scenario predicts a neutrino flux which should be observable with northern neutrino telescopes like NEMO. It also predicts strong TeV--X-ray--IR correlations. … … 262 258 263 259 264 The presence of a Dark Matter halo of the Galaxy is well established by stellar dynamics \cite{Klypin2002}. At present, the nature of Dark Matter is unknown, but a number of viable candidates have been advocated within different theoretical frameworks mainly motivated by particle physics (for a review see \cite{jung96}) including the widely studied models of supersymmetric (SUSY) Dark Matter \cite{Ellis1984}. Also models involving extra dimensions are discussed like Kaluza-Klein Dark Matter \cite{Kaluza_Klein,Bergstrom2004}.260 The presence of a Dark Matter halo of the Galaxy is well established by stellar dynamics \cite{Klypin2002}. At present, the nature of Dark Matter is unknown, but a number of viable candidates have been advocated within different theoretical frameworks, mainly motivated by particle physics (for a review see \cite{jung96}) including the widely studied models of supersymmetric (SUSY) Dark Matter \cite{Ellis1984}. Also models involving extra dimensions are discussed like Kaluza-Klein Dark Matter \cite{Kaluza_Klein,Bergstrom2004}. 265 261 266 262 The supersymmetric particle dark matter candidates might self-annihilate into boson or fermion pairs yielding very high energy gammas in subsequent decays and from hadronisation. The gamma flux above an energy threshold $E_{\mathrm{thresh}}$ per solid angle $\Omega$ is given by: … … 275 271 Numerical simulations of cold dark matter \cite{NFW1997,Stoehr2002,Hayashi2004,Moore1998} predict universal DM halo profiles with a density enhancement in the center of the dark halos. In the very center the dark matter density can be even more enhanced through an adiabatic compression due to the baryons \cite{Prada2004} present. All dark matter distributions that predict observable fluxes are cusped, yielding an approximately point-like source. 276 272 277 Using fits of these dark matter profiles to the rotation data of the milky way predictions for the density profile $\rho_{\chi}$ of the dark matter can be made \cite{Fornego2004,Evans2004}. On the other hand, for a given choice of SUSY parameters $m_{\chi},\;\langle \sigma v \rangle$ and $N_{\gamma}$ are determined.273 Using fits of these dark matter profiles to the rotation data of the Milky Way predictions for the density profile $\rho_{\chi}$ of the dark matter can be made \cite{Fornego2004,Evans2004}. On the other hand, for a given choice of SUSY parameters $m_{\chi},\;\langle \sigma v \rangle$ and $N_{\gamma}$ are determined. 278 274 %Assuming parameters for the SUSY models determine the neutralino mass, the thermally averaged annihilation cross section and the gamma yield. Combining both models about the dark matter distribution and SUSY 279 275 Combining the SUSY predictions with the predictions for the DM density profile 280 276 predictions for the gamma flux from SUSY particle dark matter annihilation are derived. 281 277 282 Figure \ref{fig:exclusion_lmits} shows exclusion limits for MAGIC (straight lines) for the four most promising sources 283 %taking the sensitivity of MAGIC from MC simulations into account for different sources and predictions from typical allowed SUSY models 284 in the plane $N_{\gamma}(E_{\gamma}>E_{\mathrm{thresh}})\langle \sigma v \rangle$ vs. $m_{\chi}$. Due to its proximity the G alactic Center yields the largest expected flux from particle dark matter annihilation. Nevertheless this flux is more than one order of magnitude below the current MAGIC sensitivity. Also the observed flux from the HESS experiment is wayabove the theoretical expectation.278 279 Figure \ref{fig:exclusion_lmits} shows exclusion limits for MAGIC (solid straight lines) for the four most promising sources, 280 in the plane $N_{\gamma}(E_{\gamma}>E_{\mathrm{thresh}})\langle \sigma v \rangle$ vs. $m_{\chi}$. Due to its proximity the GC yields the largest expected flux from particle dark matter annihilation. Nevertheless, this minimum measurable flux is more than one order of magnitude above the highest fluxes predicted by SUSY models. Also the flux measured by the HESS experiment is far above the theoretical expectation. 285 281 286 282 … … 289 285 \includegraphics[totalheight=6cm]{plot_DM_exclusion.eps}%{Dark_exclusion_limits.eps} 290 286 \end{center} 291 \caption[DM exclusion limits.]{Exclusion limits for the four most promising sources of dark matter annihilation radiation. The galactic center is expected to give the largest flux from all sources. For energies above 700 GeV, the flux from the GC as observed by the HESS experimentis within the reach of MAGIC. The solid points represent flux predictions from some typical SUSY models. -- Figure to be updated --} \label{fig:exclusion_lmits}287 \caption[DM exclusion limits.]{Exclusion limits (solid straight lines) for the four most promising sources of dark matter annihilation radiation. The GC is expected to give the largest flux from all sources. For energies above 700 GeV, the flux from the GC as observed by the HESS experiment (dotted line)is within the reach of MAGIC. The solid points represent flux predictions from some typical SUSY models. -- Figure to be updated --} \label{fig:exclusion_lmits} 292 288 \end{figure} 293 289 294 290 295 Detailed discussion of the observed gamma flux from the Galactic Center can be found in \cite{Hooper2004,Horns2004}. The observed spectrum extends to more than 18 TeV, well beyond the favored mass region of the lightest SUSY particle, and the observed flux is larger than the theoretical expectation in most models. This leads to the conclusion that most likely the dominating part of the observed gamma flux from the Galactic Center is not due to SUSY particle Dark Matter annihilation. Other dark matter scenarios like Kaluza-Klein Dark Matter cannot be excluded. 291 292 Detailed discussions of the observed gamma fluxes from the GC can be found in \cite{Hooper2004,Horns2004}. The observed spectrum extends to more than 18 TeV, well beyond the favored mass region of the lightest SUSY particle, and the observed flux is larger than the flux expected in most theoretical models. This leads to the conclusion that most likely the dominating part of the observed gamma flux from the GC is not due to SUSY particle Dark Matter annihilation. Other dark matter scenarios like Kaluza-Klein Dark Matter can not be excluded. 296 293 297 294 … … 411 408 412 409 413 The galactic centerculminates at about 58 deg ZA in La Palma. It is visible414 at up to 60 deg ZA between April and late August for in total about 150 hours. The galactic centerhas a quite large LONS background. This together with the large ZA requires to take dedicated OFF data. Since the LONS level is in any case very large moon observations can be considered in addition to the normal observations.410 The GC culminates at about 58 deg ZA in La Palma. It is visible 411 at up to 60 deg ZA between April and late August for in total about 150 hours. The GC has a quite large LONS background. This together with the large ZA requires to take dedicated OFF data. Since the LONS level is in any case very large moon observations can be considered in addition to the normal observations. 415 412 416 413 … … 437 434 To extend the available observation time we propose to take moon ON and OFF data in addition. Nevertheless, the proposed maximum ZA of 60 deg should not be exceeded during moon observations. 438 435 439 In order to take part in exploring the exciting physics of the galactic center436 In order to take part in exploring the exciting physics of the GC 440 437 we propose to start taking data as soon as possible beginning in April. In this way first results may be presented in the summer conferences 2005. 441 438 … … 443 440 \section{Outlook and Conclusions} 444 441 445 The galactic center is an interesting target in all wavelengths. A great wealth of scientific publications is available, over 600 since 1999. First detections of the Galactic Centerby the other IACTs Whipple, Cangaroo and HESS are made. Nevertheless the reconstructed fluxes differ significantly. This can be explained by calibration problems, time variations of the source or different integrated sources due to different point spread functions. The nature of the source of the VHE gamma rays is not yet been agreed on.446 447 Conventional acceleration mechanisms for the VHE gamma radiation utilize the accretion onto the black hole and supernova remnants. The galactic centeris expected to be the brightest source of VHE gammas from particle dark matter annihilation. Although the observed gamma radiation is most probably not due to dark matter annihilation, it is interesting to investigate and characterize the observed gamma radiation as it is not excluded that a part of the flux is due to dark matter annihilation.442 The GC is an interesting target in all wavelengths. A great wealth of scientific publications is available, over 600 since 1999. First detections of the GC by the other IACTs Whipple, Cangaroo and HESS are made. Nevertheless the reconstructed fluxes differ significantly. This can be explained by calibration problems, time variations of the source or different integrated sources due to different point spread functions. The nature of the source of the VHE gamma rays is not yet been agreed on. 443 444 Conventional acceleration mechanisms for the VHE gamma radiation utilize the accretion onto the black hole and supernova remnants. The GC is expected to be the brightest source of VHE gammas from particle dark matter annihilation. Although the observed gamma radiation is most probably not due to dark matter annihilation, it is interesting to investigate and characterize the observed gamma radiation as it is not excluded that a part of the flux is due to dark matter annihilation. 448 445 449 446 The MAGIC data could help to determine the nature of the source and to solve the flux discrepancies between the measurements by other experiments. Due to the large Zenith angle MAGIC will have a large energy threshold but also a large collection area and good statistics at the highest energies. The observation results can also be used to inter-calibrate the different IACTs.
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