Comment on “Characterizing the population of pulsars in the Galactic bulge with the Fermi large area telescope” [arXiv:1705.00009v1]

Journal Article · Tue Apr 24 00:00:00 EDT 2018 · Physics of the Dark Universe

DOI:https://doi.org/10.1016/j.dark.2018.04.004· OSTI ID:1596596

Bartels, Richard ^[1]; Hooper, Dan ^[2]; Linden, Tim ^[3]; Mishra-Sharma, Siddharth ^[4]; Rodd, Nicholas L. ^[5]; Safdi, Benjamin R. ^[6]; Slatyer, Tracy R.  ^[5]

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1. Univ. of Amsterdam, Amsterdam (The Netherlands)
2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
3. The Ohio State Univ., Columbus, OH (United States)
4. Princeton Univ., Princeton, NJ (United States)
5. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
6. Univ. of Michigan, Ann Arbor, MI (United States)

Here, the $$\textit{Fermi}$$-LAT Collaboration recently presented a new catalog of gamma-ray sources located within the $$40^{\circ} \times 40^{\circ}$$ region around the Galactic Center~(Ajello et al. 2017) -- the Second Fermi Inner Galaxy (2FIG) catalog. Utilizing this catalog, they analyzed models for the spatial distribution and luminosity function of sources with a pulsar-like gamma-ray spectrum. Ajello et al. 2017 v1 also claimed to detect, in addition to a disk-like population of pulsar-like sources, an approximately 7$$\sigma$$ preference for an additional centrally concentrated population of pulsar-like sources, which they referred to as a "Galactic Bulge" population. Such a population would be of great interest, as it would support a pulsar interpretation of the gamma-ray excess that has long been observed in this region. In an effort to further explore the implications of this new source catalog, we attempted to reproduce the results presented by the $$\textit{Fermi}$$-LAT Collaboration, but failed to do so. Mimicking as closely as possible the analysis techniques undertaken in Ajello et al. 2017, we instead find that our likelihood analysis favors a very different spatial distribution and luminosity function for these sources. Most notably, our results do not exhibit a strong preference for a "Galactic Bulge" population of pulsars. Furthermore, we find that masking the regions immediately surrounding each of the 2FIG pulsar candidates does $$\textit{not}$$ significantly impact the spectrum or intensity of the Galactic Center gamma-ray excess. Although these results refute the claim of strong evidence for a centrally concentrated pulsar population presented in Ajello et al. 2017, they neither rule out nor provide support for the possibility that the Galactic Center excess is generated by a population of low-luminosity and currently largely unobserved pulsars.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: SC0013999; AC02-07CH11359; SC00012567
• OSTI ID: 1596596
• Alternate ID(s): OSTI ID: 1439047; OSTI ID: 1548454
• Report Number(s): MIT-CTP-4945; PUPT-2538; MCTP-17-20; FERMILAB-PUB-17-427-A; arXiv:1710.10266; arXiv:1710.10266; TRN: US1900536
• Journal Information: Physics of the Dark Universe, Vol. 20, Issue C; Related Information: https://github.com/bsafdi/GCE-2FIG; ISSN 2212-6864
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Galactic center
Dark matter
Millisecond pulsar
Gamma-ray astronomy