VERITAS Observations Of M 31and some results about my recent work

2015.11.24

1.Gamma-ray emission in M31

• M31 is the closest galaxy to the Milky Way. extend to 3.2*1degree^2, allowing its internal structure to be studied in detail. It has a gas rich star forming ring ~10kpc from galaxy center.

• There are two main contributors to the VHE emission from M 31: a. diffuse emission from the interaction of cosmic rays with the interstellar medium. b. unresolved point-source emission.

• For diffuse emission, the emission is more diffuse and coming from regions away from potential sources. it will suggest that the emission is caused by cosmic-rays diffusing large distances through the galaxy from their sources. Since hadronic cosmic rays have a significantly longer life time than leptonic cosmic rays this would provide good evidence for a hadronic origin. Another significant evidence for hadronic origin is pion-bump around 0.1 GeV.

• For unresoved point sources. It could be regions where there are a number of potentially unresolved point sources, suggesting the sources themselves, or cosmic rays that are only diffusing a short distance from the source population, that are producing the signal.

Process of Fermi LAT Data

• six and half year pass7 data, 0.1-300 GeV.• ROI=15 degree• Fermi Science Tool v9r33p0• IRF: P7REP_SOURCE_V15 • background models : galactic diffuse model

gll_iem_v05_rev1, isotropic diffuse model iso_source_v05, point sources from the 3FGL catalogue

• add a point source at (RA, Dec (J2000)) = (00h 40m 53s.43,+42 15’ 02".0)

spatial templates of M31

Ralph Bird et al.

VERITAS Observation and results

• VERITAS is an array of four imaging atmospheric Cherenkov telescopes (IACT) located at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona.

• Each telescope has a mirror area of 110m2 and is equipped with a 499-pixel camera of 3:5 diameter field-of-view (FoV) with an angular resolution of 0.1 deg at 1TeV

• Energy range from 85GeV to > 30TeV• 54.69 hours of data are used

results of VERITAS observation

results of my work

spectrums

Thank you!