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The photo-astrometric vertical tracer density of the Milky Way - II. Results from Gaia

Everall, A, Belokurov, V, Evans, NW, Boubert, D and Grand, RJJ (2022) The photo-astrometric vertical tracer density of the Milky Way - II. Results from Gaia. Monthly Notices of the Royal Astronomical Society, 511 (3). pp. 3863-3880. ISSN 0035-8711

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Open Access URL: https://doi.org/10.1093/mnras/stac305 (Published version)


We use Gaia photometry and astrometry to estimate the vertical spatial structure of the Milky Way at the Solar radius, formally accounting for sample incompleteness (the selection function) and parallax measurement uncertainty. Our results show impressive precision demonstrating the power of the Gaia data. However, systematic errors dominate the parameter value uncertainties. We thoroughly test and quantify the impacts of all systematic uncertainties. The vertical tracer density is modelled as a sum of two exponential profiles for the thin and thick discs, together with a spherically symmetric power law for the stellar halo. We constrain the thin disc scale height as ${h_\mathrm{Tn}=260 \pm 3\, (\mathrm{stat}) \pm 26\, \mathrm{pc}\, (\mathrm{sys})}$ and thick disc ${h\mathrm{Tk}=693 \pm 7 \, (\mathrm{stat}) \pm 121\, \mathrm{pc}\, (\mathrm{sys})}$. For the halo, we obtain a power-law profile with \mathrm{H}=3.543\pm 0.023 \, (\mathrm{stat}) \pm 0.259\, (\mathrm{sys})$. We infer a local stellar mass density for non-compact object stars of ${\rho \mathrm{local}{} = 3.66\pm 0.03\, (\mathrm{stat})\pm 0.52 \times 10{-2}\, \mathrm{M}\odot \, \mathrm{pc}{-3}\, (\mathrm{sys})}$ and surface density of ${\Sigma \mathrm{local}{} = 23.17\pm 0.08\, (\mathrm{stat})\pm 2.43\, \mathrm{M}\odot \, \mathrm{pc}{-2}\, (\mathrm{sys})}$. We find asymmetries above and below the disc with longer disc scale heights in the north but a flatter halo in the south at the 10 per cent level.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press (OUP)
SWORD Depositor: A Symplectic
Date Deposited: 22 Mar 2023 13:10
Last Modified: 22 Mar 2023 13:10
DOI or ID number: 10.1093/mnras/stac305
URI: https://researchonline.ljmu.ac.uk/id/eprint/19154
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