ORCID Profile
0000-0001-8867-2693
Current Organisations
Kavli Institute for the Physics and Mathematics of the Universe
,
University of Amsterdam
,
San Francisco State University
,
Universiteit van Amsterdam
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Publications
The Andromeda gamma-ray excess: background systematics of the millisecond pulsars and dark matter interpretations
Publisher: Oxford University Press (OUP)
Date: 08-09-2022
Abstract: Since the discovery of an excess in gamma rays in the direction of M31, its cause has been unclear. Published interpretations focus on dark matter or stellar related origins. Studies of a similar excess in the Milky Way centre motivate a correlation of the spatial morphology of the signal with the distribution of stellar mass in M31. However, a robust determination of the best theory for the observed excess emission is challenging due to uncertainties in the astrophysical gamma-ray foreground model. We perform a spectro-morphological analysis of the M31 gamma-ray excess using state-of-the-art templates for the distribution of stellar mass in M31 and novel astrophysical foreground models for its sky region. We construct maps for the old stellar populations of M31 based on data from the PAndAS survey and carefully remove the foreground stars. We also produce improved astrophysical foreground models via novel image inpainting techniques based on machine learning methods. Our stellar maps, mimicking the location of a population of millisecond pulsars in the bulge of M31, reach a 5.4σ significance, making them as strongly favoured as the simple phenomenological models usually considered in the literature, e.g. disc-like templates. This detection is robust to generous variations of the astrophysical foreground model. Once the stellar templates are included in the astrophysical model, we show that the dark matter annihilation interpretation of the signal is unwarranted. We demonstrate that about one million unresolved millisecond pulsars naturally explain the observed gamma-ray luminosity per stellar mass, energy spectrum, and stellar bulge-to-disc flux ratio.
Detection of Gamma Ray Emission from the Sagittarius Dwarf Spheroidal Galaxy
Publisher: Research Square Platform LLC
Date: 28-10-2021
DOI: 10.21203/RS.3.RS-1025965/V1
Abstract: The Fermi Bubbles are giant, γ-ray emitting lobes emanating from the nucleus of the Milky Way [1, 2] discovered in ∼1-100 GeV data collected by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope [3]. Previous work [4] has revealed substructure within the Fermi Bubbles that has been interpreted as a signature of collimated outflows from the Galaxy’s super-massive black hole. Here we show that much of the γ-ray emission associated to the brightest region of substructure – the so-called cocoon – is actually due to the Sagittarius dwarf spheroidal (Sgr dSph) galaxy. This large Milky Way satellite is viewed through the Fermi Bubbles from the position of the Solar System. As a tidally and ram-pressure stripped remnant, the Sgr dSph has no on-going star formation, but we demonstrate that its γ-ray signal is naturally explained by inverse Compton scattering of cosmic microwave back-ground photons by high-energy electron-positron pairs injected by the dwarf’s millisecond pulsar (MSP) population, combined with these objects’ magnetospheric emission. This finding suggests that MSPs likely produce significant γ-ray emission amongst old stellar populations, potentially confounding indirect dark matter searches in regions such as the Galactic Centre, the Andromeda galaxy, and other massive Milky Way dwarf spheroidals.
Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess
Publisher: IOP Publishing
Date: 11-08-2017
Gamma-ray emission from the Sagittarius dwarf spheroidal galaxy due to millisecond pulsars
Publisher: Springer Science and Business Media LLC
Date: 05-09-2022
Measuring the smearing of the Galactic 511-keV signal: positron propagation or supernova kicks?
Publisher: Oxford University Press (OUP)
Date: 08-10-2021
Comparing the galactic bulge and galactic disk millisecond pulsars
Publisher: IOP Publishing
Date: 21-12-2020
Foreground mismodeling and the point source explanation of the Fermi Galactic Center excess
Publisher: American Physical Society (APS)
Date: 16-07-2020
Galactic bulge preferred over dark matter for the Galactic centre gamma-ray excess
Publisher: Springer Science and Business Media LLC
Date: 12-03-2018
Prospects for detecting heavy WIMP dark matter with the Cherenkov Telescope Array: The Wino and Higgsino
Publisher: American Physical Society (APS)
Date: 12-01-2021
Cosmic ray models of the ridge-like excess of gamma rays in the Galactic Centre
Publisher: Oxford University Press (OUP)
Date: 09-06-2015
Cherenkov Telescope Array sensitivity to the putative millisecond pulsar population responsible for the Galactic Centre excess
Publisher: Oxford University Press (OUP)
Date: 21-05-2021
Abstract: The leading explanation of the Fermi Galactic Centre γ-ray excess is the extended emission from an unresolved population of millisecond pulsars (MSPs) in the Galactic bulge. Such a population would, along with the prompt γ-rays, also inject large quantities of electrons ositrons (e±) into the interstellar medium. These e± could potentially inverse-Compton (IC) scatter ambient photons into γ-rays that fall within the sensitivity range of the upcoming Cherenkov Telescope Array (CTA). In this article, we examine the detection potential of CTA to this signature by making a realistic estimation of the systematic uncertainties on the Galactic diffuse emission model at TeV-scale γ-ray energies. We forecast that, in the event that e± injection spectra are harder than E−2, CTA has the potential to robustly discover the IC signature of a putative Galactic bulge MSP population sufficient to explain the Galactic Centre excess for e± injection efficiencies in the range of ≈2.9–74.1 per cent, or higher, depending on the level of mismodelling of the Galactic diffuse emission components. On the other hand, for spectra softer than E−2.5, a reliable CTA detection would require an unphysically large e± injection efficiency of ${\\gtrsim} 158{{\\ \\rm per\\ cent}}$. However, even this pessimistic conclusion may be avoided in the plausible event that MSP observational and/or modelling uncertainties can be reduced. We further find that, in the event that an IC signal were detected, CTA can successfully discriminate between an MSP and a dark matter origin for the radiating e±.
Donor Side Preference in Maxillary Reconstruction With the Free Fibula Flap
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-08-2022
Millisecond pulsars from accretion-induced collapse as the origin of the Galactic Centre gamma-ray excess signal
Publisher: Springer Science and Business Media LLC
Date: 28-04-2022
Strong evidence that the galactic bulge is shining in gamma rays
Publisher: IOP Publishing
Date: 20-09-2019
Related Organisations
Kavli Institute For The Physics And Mathematics Of The Universe
Location: Japan
Virginia Polytechnic Institute And State University
Location: United States of America
Related Funding Activities
No related grants have been discovered for Oscar Macias.