Browsing by Author "Pardo, S."
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Item The exotic fraction among unassociated Fermi sources(2010-07-15) Mirabal, N.; Nieto, D.; Pardo, S.Revealing the nature of unassociated high-energy (> 100 MeV) gamma-ray sources remains a challenge 35 years after their discovery. Of the 934 gamma-ray sources at high Galactic latitude (|b| > 15 degrees) in the First Fermi-LAT catalogue (1FGL), 316 have no obvious associations at other wavelengths. In this paper, we apply the K-means unsupervised classification algorithm to isolate potential counterparts for 18 unassociated Fermi sources contained within a 3000 square degree `overlap region' of the sky intensively covered in radio and optical wavelengths. Combining our results with previous works, we reach potential associations for 119 out of the 128 Fermi sources within said region. If these associations are correct, we estimate that less than 20% of all remaining unassociated 1FGL sources at high Galactic latitude (|b| > 15 degrees) might host `exotic' counterparts distinct from known classes of gamma-ray emitters. Potentially even these outliers could be explained by high-redshift/dust-obscured analogues of the associated sample or by intrinsically faint radio objects. Although such estimate leaves some room for novel discoveries, it severely restricts the possibility of detecting dark matter subhaloes and other unconventional types of gamma-ray emitters in the 1FGL. In closing, we argue that the identification of Fermi sources at the low end of the flux density distribution will be a complex process that might only be achieved through a clever combination of refined classification algorithms, multi-wavelength efforts, and dedicated optical spectroscopy.Item The search for galactic dark matter clump candidates with Fermi and MAGIC(2011-09-27) Nieto, D.; Aleksić, J.; Barrio, J.A.; Contreras, J.L.; Doro, M.; Lombardi, S.; Mirabal, N.; Moralejo, A.; Pardo, S.; Rico, J.; Zandanel, F.; the MAGIC CollaborationWe present a systematic search for potential dark matter clumps in our Galaxy among the 630 unassociated sources included in the LAT 1-year Point Source Catalog. Assuming a dark matter particle that generates observable gamma-ray photons beyond the Fermi energy range through self-annihilation, we compile a list of reasonable targets for the MAGIC Imaging Atmospheric Cherenkov Telescopes. In order to narrow down the origin of these enigmatic sources, we summarize ongoing multiwavelength studies including X-ray, radio, and optical spectroscopy. We report on observations of two of these candidates using the MAGIC Telescopes. We find that the synergy between Fermi and Cherenkov telescopes, along with multiwavelength observations, could play a key role in indirect searches for dark matter.Item A search for possible dark matter subhalos as IACT targets in the First Fermi-LAT Source Catalog(2011-10-21) Nieto, D.; Martínez, V.; Mirabal, N.; Barrio, J. A.; Satalecka, K.; Pardo, S.; Lozano, I.; UMBC Joint Center for Earth Systems Technology (JCET); UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)We present a systematic search for potential dark matter subhalos in our Galaxy among the 630 unassociated sources included in the First Fermi-LAT Source Catalog. Assuming a hypothetical dark matter particle that could generate observable gamma-ray photons beyond the Fermi energy range through self-annihilation, we look for reasonable targets for ground-based Imaging Atmospheric Cherenkov Telescopes at energies E > 100 GeV. In order to narrow the origin of these enigmatic sources, we look for their possible counterparts in other wavelengths including X-ray, radio, and optical spectroscopy. We find that the synergy between Fermi and Cherenkov telescopes, along with multiwavelength observations, could play a key role in indirect searches for dark matter.