Query : 2014A&A...567A.106L

2014A&A...567A.106L - Astronomy and Astrophysics, volume 567A, 106-106 (2014/7-1)

Flare in the Galactic stellar outer disc detected in SDSS-SEGUE data.


Abstract (from CDS):

We explore the outer Galactic disc up to a Galactocentric distance of ≃30kpc to derive its parameters and measure the magnitude of its flare. We obtained the 3D density of stars of type F8V-G5V with a colour selection from extinction-corrected photometric data of the Sloan Digital Sky Survey - Sloan Extension for Galactic Understanding and Exploration (SDSS-SEGUE) over 1400 deg2 in off-plane low Galactic latitude regions and fitted it to a model of flared thin+thick disc. The best-fit parameters are a thin-disc scale length of 2.0kpc, a thin-disc scale height at solar Galactocentric distance of 0.24kpc, a thick-disc scale length of 2.5kpc, and a thick-disc scale height at solar Galactocentric distance of 0.71kpc. We derive a flaring in both discs that causes the scale height of the average disc to be multiplied with respect to the solar neighbourhood value by a factor of 3.3+2.2–1.6 at R=15kpc and by a factor of 12+20–7 at R=25kpc. The flare is quite prominent at large R and its presence explains the apparent depletion of in-plane stars that are often confused with a cut-off at R>15kpc. Indeed, our Galactic disc does not present a truncation or abrupt fall-off there, but the stars are spread in off-plane regions, even at z of several kpc for R>20kpc. Moreover, the smoothness of the observed stellar distribution also suggests that there is a continuous structure and not a combination of a Galactic disc plus some other substructure or extragalactic component: the hypothesis to interpret the Monoceros ring in terms of a tidal stream of a putative accreted dwarf galaxy is not only unnecessary because the observed flare explains the overdensity in the Monoceros ring observed in SDSS fields, but it appears to be inappropriate.

Abstract Copyright:

Journal keyword(s): Galaxy: structure - Galaxy: disk - Galaxy: stellar content

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13084 0
2 NAME Monoceros Stream St* ~ ~           ~ 337 0

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