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    r6802 r6825  
    4646a few hundred GeV has been detected by the Whipple, Cangaroo and HESS
    4747collaborations. The reconstructed spectra from Cangaroo and HESS show
    48 significant differences. The acceleration mechanisms have still to be
    49 identified.
    50 
    51 Various possibilities for the acceleration of the very high energy (VHE)
    52 gamma rays are discussed in the literature, like accretion flow onto the
     48significant differences. The reasons for this discrepancy and the acceleration mechanisms have still to be identified.
     49
     50Various possibilities for the production of very-high-energy (VHE)
     51gamma rays near the GC are discussed in the literature, like accretion flow onto the
    5352central black
    5453hole, supernova shocks in Sgr A East, proton acceleration near the event
    … …  
    6160
    6261At La Palma, the GC culminates at about 58 deg zenith angle (ZA). It can be
    63 observed with MAGIC at up to 60 deg ZA for about 150 hours per year, between
    64 April and late August. The expected integral flux above 700 GeV derived from
     62observed with MAGIC at up to 60 deg ZA, between
     63April and late August, yielding a total of 150 hours per year. The expected integral flux above 700 GeV derived from
    6564the HESS data is $(3.2 \pm 1.0)\cdot 10^{-12}\mathrm{cm}^{-2}\mathrm{s}^{-1}$.
    6665Comparing this to the expected MAGIC sensitivity from MC simulations, this
    … …  
    7271
    7372\begin{itemize}
    74 \item to measure the gamma flux and its energy dependence (due to the high
     73\item to measure the gamma-ray flux and its energy dependence (due to the high
    7574zenith angles higher energies are accessible),
    7675\item to inter-calibrate MAGIC and HESS,
    … …  
    107106
    108107The Galactic Center (GC) region contains many unusual objects which may be
    109 responsible for the high energy processes generating gamma rays
     108responsible for the high-energy processes generating gamma rays
    110109\cite{Aharonian2005,Atoyan2004,Horns2004}. The GC is rich in massive stellar
    111110clusters with up to 100 OB stars \cite{GC_environment}, immersed in a dense
    … …  
    142141GeV. Assuming a distance of 8.5 kpc, the gamma ray luminosity of this source
    143142is very large $~2.2 \cdot 10^{37} \mathrm{erg}/\mathrm{s}$, which is
    144 equivalent to about 10 Crab pulsars. An independent analysis of the EGRET data
     143equivalent to about 10 times the gamma flux from the Crab nebula. An independent analysis of the EGRET data
    145144\cite{Hooper2002} indicates a point source whose position is different from the GC at a confidence level beyond 99.9 \%. %\cite{Hooper2002, A&A 335 (1998) 161}
    146145
    147 Up to now, the GC has been observed at
    148 energies above 200 GeV by Veritas, Cangaroo and HESS, \cite{GC_whipple,
    149 GC_cangaroo,GC_hess}. Figure \ref{fig:GC_gamma_flux} shows the reconstructed
    150 spectra by the other IACTs while Figure \ref{fig:GC_source_location} shows the
     146At energies above 200 GeV, the GC has been observed by Veritas, Cangaroo and HESS, \cite{GC_whipple,
     147GC_cangaroo,GC_hess}. The spectra as measured by these experiments are displayed in Figure \ref{fig:GC_gamma_flux} while Figure \ref{fig:GC_source_location} shows the
    151148different reconstructed positions of the GC source. Recently a second TeV
    152149gamma source only about 1 degree away from the GC has been
    … …  
    158155\includegraphics[totalheight=6cm]{sgr_figure4.eps}
    159156\end{center}
    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}
     157\caption[Gamma flux from GC.]{The VHE gamma flux as observed by Whipple, Cangaroo , HESS and by the EGRET experiment \cite{GC_hess}.} \label{fig:GC_gamma_flux}
    161158\end{figure}
    162159
    … …  
    169166\end{figure}
    170167
    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.
     168The discrepancies between the measured flux spectra could indicate inter-calibration problems between the IACTs. An apparent source variability of the order of one year could be due to the different regions in which the signal is integrated.
    172169
    173170
    … …  
    175172\section{Investigators and Affiliations}
    176173
    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.
     174The investigators of the proposed observations of the GC are stated in Table \ref{table:GC_investigators} together with their assigned analysis tasks. All members of the MAGIC collaboration are invited to join these efforts.
    178175
    179176
    … …  
    190187\\ Pepe Flix           & IFAE Barcelona& jflix@ifae.es & data analysis, disp
    191188\\ Sabrina Stark       & ETH Zurich    & lstark@particle.phys.ethz.ch  & data analysis, spectra
    192 \\ Wolfgang Wittek     & MPI Munich    & wittek@mppmu.mpg.de & padding
     189\\ Wolfgang Wittek     & MPI Munich    & wittek@mppmu.mpg.de & padding, unfolding
    193190\\
    194191\hline
    … …  
    198195\end{table}
    199196
     197The principal investigator is .......
    200198
    201199\section{Scientific Case}
    202200
    203201
    204 In the GC region high energy gamma rays can be produced in different sources:
     202In the GC region high-energy gamma rays can be produced in different sources:
    205203
    206204\begin{itemize}
    207 \item{entire innermost 10 pc region (interaction between cosmic rays and the dense ambient gas)}
    208 \item{non-thermal radio filaments  \cite{Pohl1997}}
    209 \item{young SNR Sgr A East \cite{Fatuzzo2003}}
     205\item{interaction between cosmic rays and the dense ambient gas within the innermost 10 pc region}
     206\item{in non-thermal radio filaments  \cite{Pohl1997}}
     207\item{in the young SNR Sgr A East \cite{Fatuzzo2003}}
    210208\item{in the compact radio source Sgr A*}
    211 \item{central part of the dark matter halo.}
     209\item{in the central part of the dark matter halo.}
    212210\end{itemize}
    213211
    214 It is quite possible that some of these potential gamma-ray production sites contribute comparably to the the observed TeV flux.
    215 
    216 
    217 % in the non-thermal radio filaments by high-energy leptons which scatter background infrared photons from the nearby ionized clouds \cite{Pohl1997,Aharonian2005}, or by hadrons colliding with dense matter. These high energy hadrons can be accelerated by the massive black hole \cite{GC_black_hole}, associated with the Sgr A$^*$, by supernovae or by energetic pulsars. Alternative mechanisms invoke the hypothetical annihilation of super-symmetric dark matter particles (for a review see \cite{jung96}) or curvature radiation of protons in the vicinity of the central super-massive black hole \cite{GC_black_hole,Melia2001}.
    218 
    219 
    220 In order to shed new light on the high energy phenomena in the GC region, and to constrain the emission mechanisms and sources, new observations with high sensitivity, good energy and angular resolution are necessary. For the interpretation of the observed gamma flux the following observables are important:
     212It is quite possible that some of these potential gamma-ray production sites contribute comparably to the observed TeV flux.
     213
     214
     215% in the non-thermal radio filaments by high-energy leptons which scatter background infrared photons from the nearby ionized clouds \cite{Pohl1997,Aharonian2005}, or by hadrons colliding with dense matter. These high-energy hadrons can be accelerated by the massive black hole \cite{GC_black_hole}, associated with the Sgr A$^*$, by supernovae or by energetic pulsars. Alternative mechanisms invoke the hypothetical annihilation of super-symmetric dark matter particles (for a review see \cite{jung96}) or curvature radiation of protons in the vicinity of the central super-massive black hole \cite{GC_black_hole,Melia2001}.
     216
     217
     218In order to shed new light on the high-energy phenomena in the GC region, and to constrain the emission mechanisms and sources, new observations with high sensitivity, good energy and angular resolution are necessary. For the interpretation of the observed gamma flux the following observables are important:
    221219
    222220\begin{itemize}
    … …  
    237235
    238236
    239 \subsection{Emission from Sgr A$^*$}
    240 
    241 Production of high-energy gamma rays within 10 Schwarzschild radii of a black hole (of any mass) could be copious because of effective acceleration of particles by the rotation-induced electric fields close to the event horizon or by strong shocks in the inner parts of the accretion disk. However, these energetic gamma rays generally cannot escape the source because of severe absorption due to interactions with the dense, low-frequency radiation through photon-photon pair production. But fortunately the supermassive black hole in our Galaxy is an exception because of its unusually low bolometric luminosity. The propagation effects related to the possible cascading in the photon filed may extend the high-energy limit to 10 TeV or even beyond \cite{Aharonian2005}.
     237\subsection{Models for the gamma-ray emission from Sgr A$^*$}
     238
     239Production of high-energy gamma rays within 10 Schwarzschild radii of a black hole (of any mass) could be copious because of effective acceleration of particles by the rotation-induced electric fields close to the event horizon or by strong shocks in the inner parts of the accretion disk. However, these energetic gamma rays generally cannot escape the source because of severe absorption due to interactions with the dense, low-frequency radiation through photon-photon pair production. Fortunately the supermassive black hole in our Galaxy is an exception because of its unusually low bolometric luminosity. The propagation effects related to the possible cascading in the photon filed may extend the high-energy limit to 10 TeV or even beyond \cite{Aharonian2005}.
    242240
    243241
    … …  
    245243\subsubsection{Leptonic Models}
    246244
    247 Also advection dominated accretion flow (ADAF) models can describe the production of high energy gamma radiation in the Galactic Center \cite{Atoyan2004}.
    248 
    249 A viable site of acceleration of highly energetic electrons could be the compact region within a few gravitational radii of the black hole. In this case the electrons produce not only curvature radiation, which peaks around 1 GeV, but also inverse Compton gamma rays (produced in the Klein-Nishina regime) with the peak emission around 100 TeV. As these high energy gammas cannot escape the source the observed gamma rays would be due to an electromagnetic cascade.
     245Also advection dominated accretion flow (ADAF) models can describe the production of high-energy gamma radiation in the Galactic Center \cite{Atoyan2004}.
     246
     247A viable site of acceleration of highly energetic electrons could be the compact region within a few gravitational radii of the black hole. In this case the electrons produce not only curvature radiation, which peaks around 1 GeV, but also inverse Compton gamma rays (produced in the Klein-Nishina regime) with the peak emission around 100 TeV. As these high-energy gammas cannot escape the source the observed gamma rays would be due to an electromagnetic cascade.
    250248
    251249\subsubsection{Hadronic Models}
    … …  
    261259The 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}.
    262260
    263 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:
     261The 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:
    264262
    265263\begin{equation*}
    … …  
    279277
    280278Figure \ref{fig:exclusion_lmits} shows exclusion limits for MAGIC (solid straight lines) for the four most promising sources,
    281 in the plane $N_{\gamma}(E_{\gamma}>E_{\mathrm{thresh}})\langle \sigma v \rangle$ vs. $m_{\chi}$. The energy threshold $E_th$ has been assumed to be 100 GeV. Due to its proximity the GC yields the largest expected flux from particle dark matter annihilation and thus the lowest exclusion limit. Nevertheless, this minimum measurable flux is more than one order of magnitude above the highest fluxes predicted by SUSY models (full circles). Also the flux measured by the HESS experiment is far above the theoretical expectation.
     279in the plane $N_{\gamma}(E_{\gamma}>E_{\mathrm{thresh}})\langle \sigma v \rangle$ vs. $m_{\chi}$. The energy threshold $E_{th}$ has been assumed to be 100 GeV. Due to its proximity the GC yields the largest expected flux from particle dark matter annihilation and thus the lowest exclusion limit. Nevertheless, this minimum measurable flux is more than one order of magnitude above the highest fluxes predicted by SUSY models (full circles). Also the flux measured by the HESS experiment is far above the theoretical expectation (dotted line).
    282280
    283281
    … …  
    286284\includegraphics[totalheight=6cm]{plot_DM_exclusion.eps}%{Dark_exclusion_limits.eps}
    287285\end{center}
    288 \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 full circles represent flux predictions from some typical SUSY models.  -- Figure to be updated --} \label{fig:exclusion_lmits}
     286\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 (lowest exclusion limits) amongst 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 full circles represent flux predictions from some typical SUSY models.  -- Figure to be updated --} \label{fig:exclusion_lmits}
    289287\end{figure}
    290288
    … …  
    343341%\end{figure}
    344342
     343Preliminary conclusion : ??????????????????
     344
    345345
    346346\section{Feasibility}
    347 
     347\label{section:feasibility}
     348
     349\subsection{Expected gamma-ray fluxes}
    348350The HESS collaboration has observed the GC for 16.5 hours, at zenith angles around 20 degrees, with energy thresholds between 165 and 255 GeV. The total number of excess events amounts to $\sim$300, and the differential gamma flux is measured as \cite{GC_hess}:
    349351
    350352\begin{equation}
    351 \frac{\mathrm{d}N_{\gamma}}{\mathrm{d}A\mathrm{d}t\mathrm{d}E} = (2.50 \pm 0.21 \pm 0.6) \cdot 10^{-12} \frac{1}{\mathrm{cm}^2\mathrm{sTeV}} \left(\frac{E}{\mathrm{TeV}}\right)^{-2.21\pm 0.09 \pm 0.15}
    352 \end{equation}
    353 
    354 A fit to the published Cangaroo flux data points \cite{GC_cangaroo} yields:
     353\frac{\mathrm{d}N_{\gamma}}{\mathrm{d}A\;\mathrm{d}t\;\mathrm{d}E} = (2.50 \pm 0.21 \pm 0.6) \cdot 10^{-12} \frac{1}{\mathrm{cm}^2\;\mathrm{s\;TeV}} \left(\frac{E}{\mathrm{TeV}}\right)^{-2.21\pm 0.09 \pm 0.15}
     354\end{equation}
     355
     356A fit to the flux data points from Cangaroo \cite{GC_cangaroo} yields:
    355357
    356358\begin{equation}
    357 \frac{\mathrm{d}N_{\gamma}}{\mathrm{d}A\mathrm{d}t\mathrm{d}E} = (3.4 \pm 3.8) \cdot 10^{-12} \frac{1}{\mathrm{cm}^2\mathrm{sTeV}} \left(\frac{E}{\mathrm{TeV}}\right)^{-4.4\pm 1.1}
    358 \end{equation}
    359 
    360 
    361 For a 60 deg ZA we conservatively estimate the analysis energy threshold to be about 700 GeV. The integrated flux of the HESS spectrum is:
     359\frac{\mathrm{d}N_{\gamma}}{\mathrm{d}A\;\mathrm{d}t\;\mathrm{d}E} = (3.4 \pm 3.8) \cdot 10^{-12} \frac{1}{\mathrm{cm}^2\;\mathrm{s\;TeV}} \left(\frac{E}{\mathrm{TeV}}\right)^{-4.4\pm 1.1}
     360\end{equation}
     361
     362The flux integrated above 700 GeV is determined as
    362363
    363364\begin{equation}
    364 \frac{\mathrm{d}N_{\gamma}(E>700 \mathrm{GeV})}{\mathrm{d}A\mathrm{d}t}=(3.2 \pm 1.0)\cdot 10^{-12}\frac{1}{\mathrm{cm}^2\mathrm{s}}
    365 \end{equation}
    366 
    367 
    368 while the integrated flux above 700 GeV obtained from the Cangaroo spectrum is given by:
    369 
    370 \begin{equation}
    371 \frac{\mathrm{d}N_{\gamma}(E>700 \mathrm{GeV})}{\mathrm{d}A\mathrm{d}t}=(3 \pm 5)\cdot 10^{-12}\frac{1}{\mathrm{cm}^2\mathrm{s}} \ .
    372 \end{equation}
    373 
    374 
    375 Thus the integral fluxes above 700 GeV based on the HESS and Cangaroo data agree within errors.
    376 
    377 Using MC simulations \cite{MC-Camera} for small zenith angles we conservatively estimate MAGICs sensitivity \cite{MC-Sensitivity} to the integral flux to be:
    378 
    379 \begin{equation}
    380 \frac{\mathrm{d}N_{\gamma}(E>700 \mathrm{GeV})}{\mathrm{d}A\mathrm{d}t}\vline_{\mathrm{min}} \approx 6\cdot 10^{-13}\frac{1}{\mathrm{cm}^2\mathrm{s}} \ .
    381 \end{equation}
    382 
    383 Assuming this sensitivity and using the integrated flux of $3.2\cdot 10^{-12} \mathrm{cm}^{-2}\mathrm{s}^{-1}$ MAGIC will obtain an excess at the 5
    384 $\sigma$ significance level in $1.8 \pm 0.5$ h observation time.
    385 
    386 The observed Cangaroo and HESS spectra differ
    387 substantially in the spectral index. While the Cangaroo spectrum only extends
    388 to about 2 TeV, the recently published HESS spectrum goes up to about 9 TeV. Figure \ref{fig:MAGIC_flux_limits} shows the HESS and Cangaroo observed fluxes together with the minimum flux detectable by MAGIC in 20 hours observation time.
    389 
    390 MAGIC will be able to solve the obvious discrepancy between the observed fluxes. Due to the observation under high zenith angle of about 60 deg MAGIC will be able to extend the source spectrum to higher energies.
     365\frac{\mathrm{d}N_{\gamma}(E>700 \mathrm{GeV})}{\mathrm{d}A\;\mathrm{d}t}=(3.2 \pm 1.0)\cdot 10^{-12}\frac{1}{\mathrm{cm}^2\;\mathrm{s}}
     366\end{equation}
     367
     368for HESS and $(3 \pm 5)\cdot 10^{-12}\frac{1}{\mathrm{cm}^2\mathrm{s}}$
     369for Cangaroo, respectively.
     370
     371The energy thresholds and flux sensitivities estimated for MAGIC on the basis of MC simulations (\cite{MC-Sensitivity, ECO-1000}) are given in Table \ref{table:MAGIC_sensitivity}.
     372
     373\begin{table}[h]{\normalsize\center
     374\begin{tabular}{c|cccc}
     375 \hline
     376 ZA          &  $E_{th}$      & sensitivity    & $\Phi(E>E_{th})$           
     377                              & $T_{5\sigma}$       \\
     378             &                & above $E_{th}$ &   &\\
     379$[^{\circ}]$ & $[{\rm GeV}]$  & $[{\rm cm}^2\;{\rm s}]^{-1}$ 
     380                              & $[{\rm cm}^2\;{\rm s}]^{-1}$     
     381                              &  $ [{\rm hours}]$   \\
     382\hline
     383 60   &   700     & $6\cdot10^{-13}$ &  $3.20\cdot10^{-12}$ &  1.8        \\
     384 70   &  1900     & $4\cdot10^{-13}$ &  $0.95\cdot10^{-12}$ &  8.9        \\
     385\hline
     386\end{tabular}
     387\caption{Energy threshold $E_{th}$ and sensitivity for MAGIC for 2 zenith angles ZA. The 4th and 5th column contain the expected integrated flux above $E_{th}$ and the time needed for observing a 5$\sigma$ excess, respectively.}\label{table:MAGIC_sensitivity}}
     388\end{table}
     389
     390
     391Figure \ref{fig:MAGIC_flux_limits} shows the HESS and Cangaroo fluxes together with the minimum flux detectable by MAGIC in 20 hours observation time.
     392
     393
    391394
    392395
    … …  
    398401\end{figure}
    399402
    400 
    401 
    402 %?? How long do we have to observe to get a good spectrum above 7 TeV??
    403 
     403It can be seen from Table \ref{table:MAGIC_sensitivity}
     404that in the ZA range from 60 to 70 degrees the energy threshold rises from 700 GeV to 1900 GeV. Correspondingly, the time necessary for observing a 5$\sigma$ excess (assuming an integrated gamma flux as measured by HESS) increases from 1.8 to 8.9 hours. This strongly suggests the MAGIC data to be taken at the smallest ZA possible. Only then the MAGIC observations will contribute to an understanding of the discrepancies between the HESS and Cangaroo results. Due to the observation under high zenith angles ($\sim$60 deg) MAGIC will be able to extend the measurements of the energy spectrum to higher energies ($\sim$20 TeV).
     405
     406
     407???? We still have no good estimate of the expected number of excess event for the different conditions. ??? \\
     408
     409???? How long do we have to observe to get a good spectrum above 7 TeV  ??? \\
     410
     411\subsection{Verification of the MAGIC analysis at high zenith angles}
     412In order to verify the correct performance of the MAGIC analysis at high ZA it is proposed to take Crab data in the interesting ZA range from 58$^{\circ}$ to 70$^{\circ}$, to reconstruct the gamma energy spectrum and to compare it with existing measurements. Like for the GC, either dedicated OFF data should be taken or observations should be made in the wobble mode.
    404413
    405414
    … …  
    407416
    408417
    409 The GC culminates at about 58 deg ZA in La Palma. Below 60 deg ZA, it is visible between April and late August for about 150 hours. The GC has a quite large LONS background. This together with the large ZA requires to take either dedicated OFF data or to take data in the wobble mode. Since the LONS level is in any case very large moon observations are considered in addition to the normal observations.
     418The GC culminates at about 58 deg ZA in La Palma. Below 60 deg ZA, it is visible between April and late August for about 150 hours. The GC region has a quite high level of background light from the night sky. This together with the large ZA requires to take either dedicated OFF data or to take data in the wobble mode (see Section \ref{section:skydirections}).
     419%Since the LONS level is in any case very large moon observations are considered in addition to the normal observations.
    410420
    411421
    412422\section{Requested Observation Time}
    413423
    414 Based on the above estimates a 5 $\sigma$ excess is expected to be observed in about 2 hours. To acquire a data set which is comparable in size to those of the other experiments at least 40 hours of observation time are requested. These 40 hours may be either split into 20 hours ON and 20 hours OFF data taking or be devoted exclusively to data taking in the wobble mode. It is still being investigated which of the observation modes is to be preferred.
    415 
    416 To get the lowest possible threshold all data shall be taken at the
     424Based on the above estimates a 5$\sigma$ excess is expected to be observed in about 2 hours, under optimal conditions. To acquire a data set which is comparable in size to those of the other experiments at least 40 hours of observation time are requested. These 40 hours may be either split into 20 hours ON and 20 hours OFF data taking or be devoted exclusively to data taking in the wobble mode. At present, the prefered mode is the wobble mode. However, a final decision has not yet been taken.
     425
     426As pointed out in Section \ref{section:feasibility}, all data should be taken at the
    417427smallest possible zenith angles between culmination at about 58 deg and 60
    418428deg. This limits the data taking interval to about 1 hour per night between
    419 April and August. In order to have the most appropriate OFF data we propose to
    420 take OFF data each night directly before or after the ON observations under
    421 the same condition, i.e. ZA and azimuth. At such high zenith angles the effect
    422 of the earth's magnetic field can be non-negligible. This depends of course on
    423 ZA and azimuth under which the data is taken.
    424 
    425 To extend the available observation time we propose to take moon ON and OFF data in addition. Also in this case, the proposed maximum ZA of 60 deg should not be exceeded during moon observations.
     429April and August.
     430
     431
     432To increase statistics we propose to take data during moonshine in addition. Also in this case, the maximum ZA of 60 deg should not be exceeded.
    426433
    427434In order to take part in exploring the exciting physics of the GC
    … …  
    429436
    430437
     438\section{Suggested sky directions to be tracked}
     439\label{section:skydirections}
     440
     441%The number of bright stars around the GC, up to a magnitude of 9, within a distance of 1.75 degrees is given in Table \ref{table:GC_brightstars}. Their total number is 42, of which 16 have a distance to the GC of less than 1 degree. The brightest star is Sgr 3  with a magnitude of 4.5 at a distance of 1.3 degrees. There is no star brighter than mag = 8.4 which is closer than 1 degree to the GC.
     442
     443
     444%\begin{table}[h]{\normalsize\center
     445%\begin{tabular}{c|cc|c}
     446% \hline
     447% mag range & distance$<1^{\circ}$ & 1$^{\circ}<$distance$<1.75^{\circ}$
     448%                                  & total number \\
     449%           &                      &                &           \\
     450%\hline
     451% 4 - 5     &          0           &        1       &     1     \\
     452% 5 - 6     &          0           &        0       &     0     \\
     453% 6 - 7     &          0           &        1       &     1     \\
     454% 7 - 8     &          0           &        5       &     5     \\
     455% 8 - 9     &         16           &       19       &    35     \\
     456%\hline
     457% 4 - 9     &         16           &       26       &    42     \\
     458%\end{tabular}
     459%\caption{Number of bright stars in the region around the Galactic center, including stars up to mag = 9.
     460%}\label{table:GC_brightstars}}
     461%\end{table}
     462
     463\subsection{Wobble mode}
     464The star field around the GC, including stars up to a magnitude of 14, is depicted in Figure \ref{fig:GC_starfield}. One can see that the star field is roughly uniform except for the left lower part (RA$\;>\;$RA$_{GC}+4.7$ min), where the field is significantly brighter. The sky directions (WGC1, WGC2) to be tracked in the wobble mode should be chosen such that in the camera the sky field relative to the source position (GC) is similar to the sky field relative to the mirror source position (anti-source position). For this reason the prefered directions for the wobble mode are WGC1 = (RA$_{GC}$, dec$_{GC}$+0.4$^{\circ}$) and WGC2 = (RA$_{GC}$, dec$_{GC}$-0.4$^{\circ}$. During one night, 50\% of the data should be taken at WGC1 and 50\% at WGC2, switching between the 2 directions every 30 minutes.
     465
     466\begin{figure}[h!]
     467\begin{center}
     468\includegraphics[totalheight=16cm]{GCregion14.eps}
     469\end{center}
     470\caption[Star field around the GC.]{Star field around the GC. Stars up to a magnitude of 14 are plotted. The 2 big circles correspond to distances of 1$^{\circ}$ and 1.75$^{\circ}$ from the GC, respectively. The x axis is pointing into the direction of decreasing RA, the y axis into the direction of increasing declination. The grid spacing in the declination is 20 arc minutes.
     471} \label{fig:GC_starfield}
     472\end{figure}
     473
     474\begin{figure}[h!]
     475\begin{center}
     476\includegraphics[totalheight=16cm]{GCregion14large.eps}
     477\end{center}
     478\caption[Star field around the GC.]{Star field around the GC. Stars up to a magnitude of 14 are plotted. The 2 big circles correspond to distances of 1$^{\circ}$ and 1.75$^{\circ}$ from the GC, respectively. The x axis is pointing into the direction of decreasing RA, the y axis into the direction of increasing declination. The grid spacing in the declination is 1 degree.
     479} \label{fig:GC_starfield_large}
     480\end{figure}
     481
     482\begin{figure}[h!]
     483\begin{center}
     484\includegraphics[totalheight=16cm]{GCregionOFF.eps}
     485\end{center}
     486\caption[Star field around the GC.]{Star field around the GC. Stars up to a magnitude of 12 are plotted. The ON region is indicated by the bigger circle in the center. A possible OFF region is shown by the bigger circle in the left upper part of the figure. The x axis is pointing into the direction of decreasing RA, the y axis into the direction of increasing declination. The grid spacing in the declination is 1 degree.
     487} \label{fig:GC_starfield_OFF}
     488\end{figure}
     489
     490\subsection{ON/OFF mode}
     491
     492A larger sky area than in Fig.\ref{fig:GC_starfield} is shown in Figs. \ref{fig:GC_starfield_large} and \ref{fig:GC_starfield_OFF}. The bigger circle in the center indicates the ON region around the GC. An appropriate OFF region, with a sky field similar to that of the ON region,  would be the one marked by the bigger circle in the upper left part of Fig.\ref{fig:GC_starfield_OFF} . It is centered at the Galactic Plane, contains the bright star Sgr 3 (at (RA, dec) = $(17^h47^m34^s,\;-27^{\circ}49'51"$) ) in its outer part and has the coordinates GC$_{OFF}$ = (RA, dec) = $(17^h52^m00^s,\;-26^{\circ}39'06")$. The difference in RA between the GC and GC$_{OFF}$ corresponds to about 7 minutes.
     493
     494%In order to have the most appropriate OFF data we propose to
     495%take OFF data each night directly before or after the ON observations under
     496%the same condition.
     497
     498
     499
     500
    431501\section{Outlook and Conclusions}
    432502
    433 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.
    434 
    435 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.
    436 
    437 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.
     503The GC is an interesting target in all wavelength bands. There is a great wealth of scientific publications, over 600 since 1999. First detections of the GC by the IACTs Whipple, Cangaroo and HESS were made. The measured fluxes exhibit significant differences. These may be explained by calibration problems, by time variations of the source or by different source regions due to different point spread functions. The nature of the source of the VHE gamma rays has not yet been identified.
     504
     505Conventional 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 a contribution due to dark matter annihilation is not excluded.
     506
     507Data taken by MAGIC could help to determine the nature of the source and to understand the flux discrepancies. Due to the large zenith angles MAGIC will have a large energy threshold but also a large collection area and good statistics at the highest energies. The measurements may also be used to inter-calibrate the different IACTs.
    438508
    439509
    … …  
    450520The authors thank A. Moralejo for helpful discussions about the Monte Carlo simulations.
    451521
     522\newpage
    452523
    453524\bibliography{bibbib}
    454525\bibliographystyle{GC}
    455 
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    463526
    464527
    … …  
    529592\end{equation}
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  • trunk/MagicSoft/GC-Proposal/bibbib.bib

    r6794 r6825  
    66     eprint    = "astro-ph/0212509",
    77     SLACcitation  = "%%CITATION = ASTRO-PH 0212509;%%"
     8}
     9
     10@Article{ECO-1000,
     11     author    = {{Martinez}, M. and others},
     12     title     = "ECO, the European Gamma-Ray Observatory: Low-threshold
     13Telescopes at La Palma",
     14     year      = "2003",
     15     eprint    = "",
     16     SLACcitation  = "%%CITATION = ASTRO-PH xxxxx;%%"
    817}
    918
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