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19 April 2024 |
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Article overview
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The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae | | G. Iorio
; V. Belokurov
; D. Erkal
; S.E. Koposov
; C. Nipoti
; F. Fraternali
; | | Date: |
12 Jul 2017 | | Abstract: | We exploit the first gaia data release to study the properties of the
Galactic stellar halo as traced by RR Lyrae. We demonstrate that it is possible
to select a pure sample of RR Lyrae using only photometric information
available in the Gaia+2MASS catalogue. The final sample contains about 21600 RR
Lyrae covering an unprecedented fraction ($sim60\%$) of the volume of the
Galactic inner halo ($ ext{R}<28$ kpc). We study the morphology of the stellar
halo by analysing the RR Lyrae distribution with parametric and non-parametric
techniques. Taking advantage of the uniform all-sky coverage, we test halo
models more sophisticated than usually considered in the literature, such as
those with varying flattening, tilt and/or offset of the halo with respect to
the Galactic disc. A consistent picture emerges: the inner halo is well
reproduced by a smooth distribution of stars settled on triaxial ellipsoids.
The minor axis is perpendicular to the Milky Ways disc, while the major axis is
misaligned by $sim20^{circ}$ from the Galactic Y axis. The elongation along
the major axis is mild ($ ext{p}=1.27$), and the vertical flattening is shown
to evolve from a squashed state with $ ext{q}approx0.57$ in the centre to a
more spherical $ ext{q}approx0.75$ at the outer edge of our dataset. The
density slope is well approximated by a single power-law with exponent
$alpha=-2.96$. Within the range probed, we see no significant evidence for a
change of the radial density slope, out of the plane tilt or an offset of the
halo with respect to the Galaxy’s centre. | | Source: | arXiv, 1707.3833 | | Services: | Forum | Review | PDF | Favorites | |
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