Statistical issues in astrophysical searches for particle dark matter

Conrad, J.

doi:10.1016/j.astropartphys.2014.09.003

Cited by 41 publications

(39 citation statements)

References 76 publications

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“…We found a detection for the 0.5-8 keV image of SDSS J0813 + 3508 with p = 0.0108, which becomes less significant (the p-value increases to p = 0.0832) after taking into account the number of tests we have performed (e.g. Conrad 2015). We then compared the radio and X-ray images of SDSS J0813 + 3508, and did not find extended Xray structure that corresponds to the radio jet, as shown in Fig.…”

Section: Future Workmentioning

confidence: 78%

Investigating the X-ray enhancements of highly radio-loud quasars at z > 4

Zhu

Brandt

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We have investigated the jet-linked X-ray emission from highly radio-loud quasars (HRLQs; log R > 2.5) at high redshift. We studied the X-ray properties of 15 HRLQs at z > 4, using new Chandra observations for six objects and archival XMM-Newton and Swift observations for the other nine. We focused on testing the apparent enhancement of jet-linked X-ray emission from HRLQs at z > 4. Utilizing an enlarged (24 objects) optically flux-limited sample with complete X-ray coverage, we confirmed that HRLQs at z > 4 have enhanced X-ray emission relative to that of HRLQs at z ≈ 1-2 with matched UV/optical and radio luminosity, at a 4.0-4.6 σ level; the X-ray enhancements are confirmed considering both two-point spectral indices and inspection of broad-band spectral energy distributions. The typical factor of enhancement is revised to 1.9 +0.5 −0.4 , which is smaller than but consistent with previous results. A fractional IC/CMB model can still explain our results at high redshift, which puts tighter constraints on the fraction of IC/CMB X-rays at lower redshifts, assuming the physical properties of quasar jets do not have a strong redshift dependence. A dominant IC/CMB model is inconsistent with our data.

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Section: Future Workmentioning

confidence: 78%

Investigating the X-ray enhancements of highly radio-loud quasars at z > 4

Zhu

Brandt

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…This suggests fundamental limitations to the spherical Jeans modeling which is common in the field (although see [32] for Jfactors computed using axisymmetric Jeans modeling). In particular, increasingly sophisticated statistical techniques [70,71] will fail to include an inherent uncertainty if the assumption of a spherical stellar density profiles in a spherical dark halo breaks down. The uncertainties, which are different for different dSphs, must be accounted for joint analyses of multiple dSphs.…”

Section: Discussionmentioning

confidence: 99%

Indirect dark matter detection for flattened dwarf galaxies

et al. 2016

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Gamma-ray experiments seeking to detect evidence of dark matter annihilation in dwarf spheroidal galaxies require knowledge of the distribution of dark matter within these systems. We analyze the effects of flattening on the annihilation (J) and decay (D) factors of dwarf spheroidal galaxies with both analytic and numerical methods. Flattening has two consequences: first, there is a geometric effect as the squeezing (or stretching) of the dark matter distribution enhances (or diminishes) the J-factor; second, the line of sight velocity dispersion of stars must hold up the flattened baryonic component in the flattened dark matter halo. We provide analytic formulae and a simple numerical approach to estimate the correction to the J-and D-factors required over simple spherical modeling. The formulae are validated with a series of equilibrium models of flattened stellar distributions embedded in flattened dark-matter distributions. We compute corrections to the J-and D-factors for the Milky Way dwarf spheroidal galaxies under the assumption that they are all prolate or all oblate and find that the hierarchy of J-factors for the dwarf spheroidals is slightly altered (typical correction factors for an ellipticity of 0.4 are 0.75 for the oblate case and 1.6 for the prolate case). We demonstrate that spherical estimates of the D-factors are very insensitive to the flattening and introduce uncertainties significantly less than the uncertainties in the D-factors from the other observables for all the dwarf spheroidals (for example, +10 per cent −3 per cent for a typical ellipticity of 0.4). We conclude by investigating the spread in correction factors produced by triaxial figures and provide uncertainties in the J-factors for the dwarf spheroidals using different physically-motivated assumptions for their intrinsic shape and axis alignments. We find that the uncertainty in the J-factors due to triaxiality increases with the observed ellipticity and, in general, introduces uncertainties of a factor of 2 in the J-factors. We discuss our results in light of the reported gamma-ray signal from the highly-flattened ultrafaint Reticulum II. Tables of the J-and D-factors for the Milky Way dwarf spheroidal galaxies are provided (assuming an oblate or prolate structure) along with a table of the uncertainty on these factors arising from the unknown triaxiality. PACS numbers: 95.35.+d, 95.55.Ka, 12.60.-i, 98.52.Wz * Electronic address: jls@ast.cam.ac.uk † Electronic address: nwe@ast.cam.ac.uk ‡ Electronic address: alexgs@cmu.edu § Electronic address: wd11@leicester.ac.ukjor Cherenkov telescope collaborations continue to invest significant time on pointed observations of Milky Way dSphs. The resulting upper limits are two to three orders of magnitude from the relic cross section [6-10], but the situation bodes well for the future CTA project [e.g. 11].An exciting development in this field is the recent and ongoing discovery of large numbers of new Milky Way satellites made possible by wide-area photometric surveys [e.g. 12-15]. Since ...

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“…with x max/min = (D/r0) cos θ ± (rt/r0) 2 − (D/r0) 2 sin 2 θ; rt is the cutoff radius of the system, usually assumed to the the tidal radius (Binney & Tremaine 2008 where Θ represents the nuisance parameters array. The final point results in the profile likelihood curve of J, with which the statistical inference can be performed (Conrad 2014). Specifically, the maximum likelihood estimate (MLE) of J and its uncertainty can be determined.…”

Section: Methodsmentioning

confidence: 99%

Dwarf spheroidal J-factor likelihoods for generalized NFW profiles

Chiappo

Cohen-Tanugi

Conrad

et al. 2019

Monthly Notices of the Royal Astronomical Society

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ABSTRACT Indirect detection strategies of particle dark matter (DM) in Dwarf spheroidal satellite galaxies (dSphs) typically entail searching for annihilation signals above the astrophysical background. To robustly compare model predictions with the observed fluxes of product particles, most analyses of astrophysical data – which are generally frequentist – rely on estimating the abundance of DM by calculating the so-called J factor. This quantity is usually inferred from the kinematic properties of the stellar population of a dSph using the Jeans equation, commonly by means of Bayesian techniques that entail the presence (and additional systematic uncertainty) of prior choice. Here, extending earlier work, we develop a scheme to derive the profile likelihood for J factors of dwarf spheroidals for models with five or more free parameters. We validate our method on a publicly available simulation suite, released by the Gaia Challenge, finding satisfactory statistical properties for bias and probability coverage. We present the profile likelihood function and maximum likelihood estimates for the J-factor of 10 dSphs. As an illustration, we apply these profile likelihoods to recently published analyses of γ-ray data with the Fermi Large Area Telescope to derive new, consistent upper limits on the DM annihilation cross-section. We do this for a subset of systems, generally referred to as classical dwarfs. The implications of these findings for DM searches are discussed, together with future improvements and extensions of this technique.

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Statistical issues in astrophysical searches for particle dark matter

Cited by 41 publications

References 76 publications

Investigating the X-ray enhancements of highly radio-loud quasars at z > 4

Investigating the X-ray enhancements of highly radio-loud quasars at z > 4

Indirect dark matter detection for flattened dwarf galaxies

Dwarf spheroidal J-factor likelihoods for generalized NFW profiles

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