Abstract
The third EGRET catalog contains a large number of unidentified sources. This subset of objects is expected to include known gamma-ray emitters of Galactic origin such as pulsars and supernova remnants, in addition to an extragalactic population of blazars. However, current data allows the intriguing possibility that some of these objects may represent a new class of yet undiscovered gamma-ray sources. Many theoretically motivated candidate emitters (e.g. clumps of annihilating dark matter particles) have been suggested to account for these detections. We take a new approach to determine to what extent this population is Galactic and to investigate the nature of the possible Galactic component. By assuming that galaxies similar to the Milky Way should host comparable populations of objects, we constrain the allowed Galactic abundance and distribution of various classes of gamma-ray sources using the EGRET data set. We find it is highly improbable that a large number of the unidentified sources are members of a Galactic halo population, but that a distribution of the sources entirely in the disk and bulge is plausible. Finally, we discuss the additional constraints and new insights that GLAST will provide.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Berezinsky, V., Dokuchaev, V., Eroshenko, Y.: Small-scale clumps in the galactic halo and dark matter annihilation. Phys. Rev. D 68(10), 103003 (2003)
Bergström, L., et al.: Clumpy neutralino dark matter. Phys. Rev. D 59(4), 043506 (1999)
Bertone, G., Zentner, A.R., Silk, J.: New signature of dark matter annihilations: gamma rays from intermediate-mass black holes. Phys. Rev. D 72(10), 103517 (2005)
Blasi, P., Olinto, A.V., Tyler, C.: Detecting WIMPs in the microwave sky. Astropart. Phys. 18, 649 (2003)
Blom, J.J., Paglione, T.A.D., Carramiñana, A.: Diffuse gamma-ray emission a from starburst galaxies and M31. Astrophys. J. 516, 744 (1999)
Calcáneo-Roldán, C., Moore, B.: Surface brightness of dark matter: unique signatures of neutralino annihilation in the galactic halo. Phys. Rev. D 62(12), 123005 (2000)
Casandjian, J.M., et al.: The EGRET sky: a new interstellar emission model and source detection. In: International Cosmic Ray Conference, p. 9 (2005)
Digel, S., et al.: What can GLAST say about the origin of cosmic rays in other galaxies?. In: AIP Conf. Proc., vol. 528, p. 449 (2000)
Gehrels, N., Michelson, P.: GLAST: the next-generation high energy gamma-ray astronomy mission. Astropart. Phys. 11, 277 (1999)
Hartman, R.C., et al.: The third EGRET catalog of high-energy gamma-ray sources. Astrophys. J. 123, 79 (1999)
Hernquist, L.: An analytical model for spherical galaxies and bulges. Astrophys. J. 356, 359 (1990)
Johnston, K.V., Hernquist, L., Bolte, M.: Fossil signatures of ancient accretion events in the halo. Astrophys. J. 465, 278 (1996)
Klypin, A., Zhao, H., Somerville, R.S.: ΛCDM-based models for the Milky Way and M31. I. Dynamical models. Astrophys. J. 573, 597 (2002)
La Palombara, N., et al.: XMM-Newton and ESO observations of the two unidentified γ-ray sources 3EG J0616-3310 and 3EG J1249-8330. Astron. Astrophys. 458, 245 (2006)
Mattox, J.R., Hartman, R.C., Reimer, O.: A quantitative evaluation of potential radio identifications for 3EG EGRET sources. Astrophys. J. Suppl. Ser. 135, 155 (2001)
Miyamoto, M., Nagai, R.: Three-dimensional models for the distribution of mass in galaxies. Publ. Astron. Soc. Jpn. 27, 533 (1975)
Navarro, J.F., Frenk, C.S., White, S.D.M.: Simulations of X-ray clusters. Mon. Not. Roy. Astron. Soc. 275, 720 (1995)
Nolan, P.L., et al.: Variability of EGRET gamma-ray sources. Astrophys. J. 597, 615 (2003)
Paredes, J.M., et al.: Discovery of a high-energy gamma-ray-emitting persistent microquasar. Science 288, 2340 (2000)
Pavlidou, V., Fields, B.D.: Diffuse gamma rays from local group galaxies. Astrophys. J. 558, 63 (2001)
Pavlidou, V., et al.: Unidentified EGRET sources and the extragalactic gamma-ray background. Astrophys. Space Sci., doi: 10.1007/s10509-007-9456-1 (2007)
Roberts, M.S.E., et al.: Pulsar wind nebulae in egret error boxes. Astrophys. Space Sci. 297, 93 (2005)
Tasitsiomi, A., Olinto, A.V.: Detectability of neutralino clumps via atmospheric Cherenkov telescopes. Phys. Rev. D 66(8), 083006 (2002)
Taylor, J.E., Silk, J.: The clumpiness of cold dark matter: implications for the annihilation signal. Mon. Not. Roy. Astron. Soc. 339, 505 (2003)
Ullio, P., et al.: Cosmological dark matter annihilations into γ rays: a closer look. Phys. Rev. D 66(12), 123502 (2002)
Author information
Authors and Affiliations
Corresponding author
Additional information
This work was supported by the Kavli Institute for Cosmological Physics through the grant NSF PHY-0114422 and by DOE grant DE-FG0291-ER40606 at the University of Chicago.
Rights and permissions
About this article
Cite this article
Siegal-Gaskins, J.M., Pavlidou, V., Olinto, A.V. et al. Population studies of the unidentified EGRET sources. Astrophys Space Sci 309, 43–49 (2007). https://doi.org/10.1007/s10509-007-9468-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10509-007-9468-x