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Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?
Ackermann M. - ไม่ระบุหน่วยงาน
ชื่อเรื่อง (EN): Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?
ผู้แต่ง / หัวหน้าโครงการ (EN): Ackermann M.
บทคัดย่อ (EN): The Fermi Large Area Telescope (LAT) has opened the way for comparative studies of cosmic rays (CRs) and high-energy objects in the Milky Way (MW) and in other, external, star-forming galaxies. Using 2 yr of observations with the Fermi LAT, Local Group galaxy M31 was detected as a marginally extended gamma-ray source, while only an upper limit has been derived for the other nearby galaxy M33. We revisited the gamma-ray emission in the direction of M31 and M33 using more than 7 yr of LAT Pass 8 data in the energy range , presenting detailed morphological and spectral analyses. M33 remains undetected, and we computed an upper limit of 2.0 × 10-12 erg cm-2 s-1 on the 0.1-100 GeV energy flux (95% confidence level). This revised upper limit remains consistent with the observed correlation between gamma-ray luminosity and star formation rate tracers and implies an average CR density in M33 that is at most half of that of the MW. M31 is detected with a significance of nearly 10σ. Its spectrum is consistent with a power law with photon index Γ = 2.4 ± 0.1stat+syst and a 0.1-100 GeV energy flux of (5.6 × 0.6stat+syst) × 10-12erg cm-2s-1. M31 is detected to be extended with a 4σ significance. The spatial distribution of the emission is consistent with a uniform-brightness disk with a radius of 0.°4 and no offset from the center of the galaxy, but nonuniform intensity distributions cannot be excluded. The flux from M31 appears confined to the inner regions of the galaxy and does not fill the disk of the galaxy or extend far from it. The gamma-ray signal is not correlated with regions rich in gas or star formation activity, which suggests that the emission is not interstellar in origin, unless the energetic particles radiating in gamma rays do not originate in recent star formation. Alternative and nonexclusive interpretations are that the emission results from a population of millisecond pulsars dispersed in the bulge and disk of M31 by disrupted globular clusters or from the decay or annihilation of dark matter particles, similar to what has been proposed to account for the so-called Galactic center excess found in Fermi-LAT observations of the MW. © 2017. The American Astronomical Society. All rights reserved.
บทคัดย่อ: ไม่พบข้อมูลจากหน่วยงานต้นทาง
ภาษา (EN): en
เอกสารแนบ (EN): https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014315519&doi=10.3847%2f1538-4357%2faa5c3d&partnerID=40&md5=3bc0dd944bb50acc49d127b0e5f8c359
เผยแพร่โดย (EN): มหาวิทยาลัยมหิดล
คำสำคัญ (EN): Local Group
เจ้าของลิขสิทธิ์ (EN): มหาวิทยาลัยมหิดล
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Ackermann M.. "Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?". ไม่ระบุหน่วยงาน. ม.ป.ป.

Ackermann M.. "Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?". ไม่ระบุหน่วยงาน. ม.ป.ป.. Print.



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Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?
Ackermann M.
มหาวิทยาลัยมหิดล
ไม่ระบุวันที่เผยแพร่
The Fermi Galactic Center GeV Excess and Implications for Dark Matter FERMI-LAT OBSERVATIONS of HIGH-ENERGY γ-RAY EMISSION TOWARD the GALACTIC CENTER Search for Extended Sources in the Galactic Plane Using Six Years of Fermi-Large Area Telescope Pass 8 Data above 10 GeV Fermi large area telescope detection of extended gamma-ray emission from the radio galaxy Fornax A Search for Gamma-Ray Emission from Local Primordial Black Holes with the Fermi Large Area Telescope MMS observations of large guide field symmetric reconnection between colliding reconnection jets at the center of a magnetic flux rope at the magnetopause Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares VERITAS and Fermi-LAT Observations of TeV Gamma-Ray Sources Discovered by HAWC in the 2HWC Catalog Test KIT Center Innovative Approach towards Treatment of Powdery Skim in Centrifuge Factories and Management of Replanting large area-HML experience
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