| dc.contributor | ALBERTO CARRAMIÑANA ALONSO | |
| dc.contributor | WILLIAM FRANK WALL | |
| dc.creator | JUAN NOE SUAREZ PEREA | |
| dc.date | 2010-08 | |
| dc.date.accessioned | 2018-11-19T14:28:11Z | |
| dc.date.available | 2018-11-19T14:28:11Z | |
| dc.identifier | http://inaoe.repositorioinstitucional.mx/jspui/handle/1009/605 | |
| dc.identifier.uri | http://repositorioslatinoamericanos.uchile.cl/handle/2250/2258747 | |
| dc.description | A model of diffuse gamma-ray emission is presented. The diffuse
gamma-ray emission is directly related to the distribution of gas and radiation in
an object and to its star formation. The relationship with star formation is due
to supernovae behaving as cosmic-ray accelerators. To model this emission from
M31, I have used the HI map of Brinks & Shane (1984) to represent the atomic
gas content and the CO map of Nieten et al (2006) to represent the molecular
hydrogen content. To represent the radiation field, I have used maps of M31 in
different bands, from infrared to ultraviolet. These images have been normalized to
the spectral energy distribution of M31. The cosmic-ray spectrum is a power law
whose indices are p = 2.76 for electrons and k = 2.71 for protons; heavier nuclei
are not currently included. These two spectra have been normalized assuming
energy equipartition between cosmic-rays and the magnetic field and a protonto-
electron ratio of 100. In these calculations I used the values for the magnetic
field strength given by Beck (1981) of 3.2 ± 0.9μG in the ring and 2.4μG in the
disk. The gamma-ray mechanisms that are used in this model are neutral pion
decay, bremsstrahlung and inverse Compton scattering. Production functions that
express the number of gamma-rays produced per unit of time per unit of nucleon
energy were obtained from Berstch et al (1993) and Haung et al (2007). The
model uses maps of gas derived from HI and CO emission lines, and maps of the
radiation field, and production functions as inputs. This gives a map of emission
in gamma-rays of M31. The integrated flux above photon energies of 100MeV is
2.11 × 10−8 photon s−1cm−2. A maximum likelihood analysis was applied to the
model map and the all-sky maps observed by EGRET. With this analysis I found
an upper limit of 7.9×10−9photons cm−2s−1 to the gamma-ray flux above 100MeV
for M31, implying a modification of the input parameters to the model. The most
probable error in the input was adopting a magnetic field strength a factor of ∼ 2
too high. A field strength of ∼ 2μG is the most appropriate value on large scales
in M31. The results of this model have been compared with flux estimates of
M31 in the same energy range made by other authors. ¨Ozel & Berkhuijsen (1987)
estimated a flux of 2.4×10−8ξ photons cm−2s−1 with ξ < 5 and Pavlidou & Fields
(2001) calculated 1×10−8photons cm−2s−1 respectively. | |
| dc.format | application/pdf | |
| dc.language | spa | |
| dc.publisher | Instituto Nacional de Astrofísica, Óptica y Electrónica | |
| dc.relation | citation:Suarez Perea J.N. | |
| dc.rights | info:eu-repo/semantics/openAccess | |
| dc.rights | http://creativecommons.org/licenses/by-nc-nd/4.0 | |
| dc.subject | info:eu-repo/classification/Astronomía de rayos gamma/Gamma-ray astronomy | |
| dc.subject | info:eu-repo/classification/Mecanismos de radiación astrofísica/Astrophysical radiation mechanisms | |
| dc.subject | info:eu-repo/classification/Rayos gamma/Gamma-rays | |
| dc.subject | info:eu-repo/classification/cti/1 | |
| dc.subject | info:eu-repo/classification/cti/21 | |
| dc.title | Modelo de emisión de rayos gamma de la galaxia de Andrómeda | |
| dc.type | Tesis | |
| dc.type | info:eu-repo/semantics/acceptedVersion | |
| dc.audience | students | |
| dc.audience | researchers | |
| dc.audience | generalPublic | |
