Some results about Fermi observation of M31

Residual maps of different energy bands 2 year statistc by Abdo et al. M31~ 240 1ES ~8 5 year counts of M31~ 629

Counts statistic roughly 200mev-1gev1-20gev20-300gev ps ps ps3 7 ？7 ？ 83.6 ps

GeV5 Ps model TSfluxindex ps e-11 ±1.1e ps e-11±1.2e-121 ps328.13e-11±1.3e ps e-11±1.6e-125 M31-6.5e-9 ~02.8e-20±2.9e-165 Disc model ps e-11±4.5e ps e-11±4.7e-121 ps328.73e-11±5.1e ps e-11±1.5e-125 M31-9.2e-9 ~02.6e-20±2.8e-165

200MeV-300 GeV Ps model TSfluxindexTSfluxindex ps e-9 ±5e e-9±4.9e-102 ps2159.7e-11±8.5e e-11±8.4e ps3363e-10±2.3e ps e-10±4.7e e-10±4.7e M e-9±9.7e e-9±9.5e Disc model ps e-9±5.4e e-9±5.5e ps215.11e-10±9e e-11±8.7e ps e-10±1e ps462.4e-10±2.7e e-10±2.7e M e-9±1.1e e-9±9.6e-102.3

1-20 GeV Ps model TSfluxindexTSfluxindex ps e-10 ±7e e-10±7.1e ps e-11±4.2e e-11±4.2e ps e-11±6.4e ps e-11±7.7e e-11±7.8e M e-10±9.9e e-10±9.7e Disc model ps e-10±6.7e e-10±7e ps e-11±4.2e e-11±4.3e ps e-11±4.3e ps e-11±6.1e e-11±6.6e M e-10±1.4e e-10±1.4e-102.6

200MeV-1 GeV Ps model TSfluxindexTSfluxindex ps115.81e-9±1.7e e-10±1.3e ps2-8.39e-78.1e-11±2.1e ps e-10±1.6e ps e-10±1.4e M e-9±3e e-9±3.5e-10 Disc model ps115.21e-9±4.8e e-9±6.9e ps2-4.4e-71.2e-15±1.2e ps e-10±2.7e-109.8e ps e-15±4.9e M e-9±7.6e e-9±1.1e-92

200MeV-20 GeV Ps model TSfluxindexTSfluxindex ps e-9 ±6.3e e-9±6.1e-102 ps e-11±1.2e e-11±1.2e ps e-10±8.3e ps e-10±5.1e e-10±5.9e M e-9±1.1e e-9±9.5e Disc model ps e-9±6.5e e-9±6.6e-102 ps23.39e-11±1.3e e-11±1.3e ps e-11±1.5e ps e-11±1.1e e-11±9.4e M e-9±1e e-9±1e-92.4

Compare to formal work TS Flux ph cm − 2 s − 1 Index Abdo et al. 200mev-20gev Ps disc ± 4.7e-9 (>100mev) 2.1 Yuan et al. 200mev-300gev Ps Disc mev -1gev Ps ±0.3e-93 Disc ±0.8e gev Ps ±1e disc ±1e mev-20gev ps ±1e-92.6 disc ±1e mev-300gev ps ±1e-92.7 disc ±1e-92.6

PS4 calculation—flux and size d m31 = 780kpc L bubble = 4*10^37 erg/s Flux= L/4 π d^2 = 5*10^-13 erg/s/cm^-2 Flux of PS4 ~ 7*10^-14 erg/s/cm^-2 Bubble size ±50°d=9.6kpc ~11.4kpc Ps4 size ~7.48kpc Fermi bubble emission at 1-50 gev with index 2 harder than π 0 decay. While ps4 emission mainly at >1 gev, with index 1.8 (M31 ps model).

Near infrared K-band model The distribution of LMXBs( MSPs) is consistent with the distribution of the K-band light, and show dense concentrate with 1 arcminute in M31 bulge. (R. Voss et al. 2007, N. Kevork et al. 2012) 200mev-20gev TSfluxindex K-band model ±0.9e-92.5 Ir_model ±1e-92.4 Ps model ±0.9e-92.6

Summury M31 gamma ray emission mainly at energy 20gev. While total flux mainly contribute to <1gev. Flux 1-20gev is about 1/8 flux 200mev-1gev. PS3 corresponding to BL Lac object 1ES (Abdo et al.), contribute gamma ray photon mainly above 1gev, which affect likelihood analysis results of M31, lead to a deflection of disc model at total band. We find that in 200mev-1gev band, emission like a disc better(4.2 σ ), while in 1gev-20gev, emission is more concentrate, more like a pointsource （ 3.7 σ ).

PS4 near center of M31 seem to elongate with minor axis, emission mainly on energy band >1gev. Which remind us about Fermi bubble of our galaxy. The luminosity and size of ps4 are comparable with values if Fermi bubble in M31 distance. However it is one side structure, different from Fermi bubble. We have to think more about the origin of this structure.

PS1 very close to north point of major axis of M31, emission from 200mev- 300gev, powerlaw index ~1.9, luminosity is 1/5 of M31 in total bands. We consider it a very significant source. While we also curious about its origin.

Further to work K-band model Two component

问题汇总 低能角分辨率不高，有没有使点源看起 来像盘。 在 likelihood analysis 中点源和盘模型还 是有区别的。如果做出来是盘模型 ts 值 更高只能说明更像盘模型。即使在低能 段，盘和点源的辐射也是有区别的。

分能段做会导致点源 ts 值和 index 不符合 真实。 这里实际上主要是普模型的影响。 Ts 值只是反应在这个能段下在这个谱模型 和空间模型下，获得光子的概率。如果 普模型和空间模型定的准确，那么该源 在这个能段的 ts 值也就可以知道了。 关键在于如何给出普模型。这涉及到 fermi 如何拟合源的过程。假如一个源 在