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https://olympias.lib.uoi.gr/jspui/handle/123456789/40566Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor.author | Psarra, Theodora | en |
| dc.date.accessioned | 2026-11-12T08:51:38Z | - |
| dc.date.available | 2026-11-12T08:51:38Z | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/40566 | - |
| dc.identifier.uri | http://dx.doi.org/10.26268/heal.uoi.20204 | - |
| dc.rights | Default License | - |
| dc.subject | Dark Matter | en |
| dc.subject | Theoretical Physics | en |
| dc.subject | Cosmology | en |
| dc.subject | Astrophysics | en |
| dc.subject | Astroparticle Physics | en |
| dc.title | Constraining the Milky Way’s Distinctive Dark Matter Distribution with Astrophysical and Cosmological Data | en |
| dc.type | masterThesis | en |
| heal.type | masterThesis | el |
| heal.type.en | Master thesis | en |
| heal.type.el | Μεταπτυχιακή εργασία | el |
| heal.dateAvailable | 2026-11-12T08:52:39Z | - |
| heal.language | en | el |
| heal.access | free | el |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών | el |
| heal.recordProvider | University of Ioannina. Department of Physics | en |
| heal.publicationDate | 2026-10-16 | - |
| heal.abstract | The declining Milky Way rotation curve inferred from Gaia DR3 has raised the possibility that our Galaxy possesses an unusually compact and low-mass dark-matter halo. In this work, we investigate what such a halo would imply for the Galactic dark-matter distribution and whether its properties can be reconciled with independent astrophysical and cosmological constraints. We analyse the published Gaia DR3-based rotation curve over $9.5$--$26.5\,\mathrm{kpc}$, adopting the fixed B2 baryonic model and a spherical Einasto dark-matter halo. After reproducing the reference circular-velocity decomposition, we constrain the halo parameters through a $\chi^2$ exploration and Bayesian inference using the \texttt{emcee} ensemble sampler, with independently initialized ensembles providing an additional robustness check. Within the adopted B2--Einasto framework, we obtain a dark-matter-only virial mass of $M_{\mathrm{vir}}=1.433^{+0.080}_{-0.059}\times10^{11}\,M_\odot$, with Einasto parameters $M_0=3.68^{+0.46}_{-0.75}\times10^{11}\,M_\odot$, $h=11.42^{+1.18}_{-1.71}\,\mathrm{kpc}$, and $n=0.431^{+0.132}_{-0.092}$. The inferred local dark-matter density is $\rho_\odot=0.4587^{+0.0135}_{-0.0143}\,\mathrm{GeV\,cm^{-3}}$, consistent with commonly adopted estimates despite the low total halo mass. The fitted Einasto shape, however, is unusual compared with typical dark-matter-only $\Lambda$CDM haloes, with $\alpha=1/n\simeq2.32$, and produces a broad, slowly varying inner density distribution when extrapolated toward the Galactic Center. This inner structure has important consequences for indirect dark-matter searches. For a $15^\circ$ cone centred on the Galactic Center, we obtain an annihilation factor of $\overline{\mathcal{J}}=2.333^{+0.694}_{-0.426}\times10^{22}\,\mathrm{GeV^2\,cm^{-5}}$ and a decay factor of $\overline{\mathcal{D}}=3.933^{+0.442}_{-0.323}\times10^{22}\,\mathrm{GeV\,cm^{-2}}$. These are approximately $3$--$5$ and $1.5$--$1.9$ times smaller, respectively, than the corresponding predictions from the comparison Einasto profiles. However, approximately $95\%$ of the annihilation factor and $87\%$ of the decay factor originate within $9.5\,\mathrm{kpc}$, beyond the region directly constrained by our fit, making these predictions strongly dependent on the assumed inner density profile. The outward extrapolation presents a different challenge. Including the baryonic contribution gives a total halo mass of approximately $2.05\times10^{11}\,M_\odot$ and a baryon fraction of $f_{\mathrm{bar}}=0.301^{+0.009}_{-0.011}$, nearly twice the cosmic mean. The inferred mass also falls substantially below abundance-matching expectations and independent estimates from outer-halo dynamical tracers. These comparisons suggest that the steep outer decline of the fitted Einasto profile may underestimate the dark-matter contribution at larger Galactocentric radii. Our results therefore reveal a tension between the successful reproduction of the declining Gaia rotation curve and the broader astrophysical and cosmological evidence concerning the Milky Way's dark-matter halo. These discrepancies do not necessarily invalidate the observed decline or establish that the Galaxy is intrinsically unusual. Thus, our analysis cannot decisively favour one interpretation over the other, but it highlights the relatively recent and ongoing debate: is the Milky Way exceptional, or is our view of it? | en |
| heal.advisorName | Perivolaropoulos, Leandros | en |
| heal.committeeMemberName | Kanti, Panagiota | en |
| heal.committeeMemberName | Καντή, Παναγιώτα | el |
| heal.committeeMemberName | Leontaris, Georgios | en |
| heal.committeeMemberName | Λεοντάρης, Γεώργιος | el |
| heal.committeeMemberName | Περιβολαρόπουλος, Λέανδρος | el |
| heal.academicPublisher | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Φυσικής | el |
| heal.academicPublisherID | uoi | el |
| heal.numberOfPages | 125 | el |
| heal.fullTextAvailability | true | - |
| Appears in Collections: | Διατριβές Μεταπτυχιακής Έρευνας (Masters) - ΦΥΣ | |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| Constraining the Milky Way's Distinctive Dark Matter Distribution with Astrophysical and Cosmological Data.pdf | 13.71 MB | Adobe PDF | View/Open |
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