From: Amara Graps (amara@amara.com)
Date: Wed Feb 19 2003 - 03:03:43 MST
http://xxx.lanl.gov/pdf/astro-ph/0301067
Astrophysics, abstract
astro-ph/0301067
From: Rodrigo Ibata <ibata@newb6.u-strasbg.fr>
Date (v1): Mon, 6 Jan 2003 16:28:45 GMT (602kb)
Date (revised v2): Tue, 18 Feb 2003 14:26:07 GMT (624kb)
One Ring to Encompass them All: A giant stellar structure that surrounds the
Galaxy
Authors: R. A. Ibata, M. J. Irwin, G. F. Lewis, A. M. N. Ferguson, N. Tanvir
Comments: 8 pages, 10 (compressed) figures, accepted by MNRAS
We present evidence that the curious stellar population found by
the Sloan Digital Sky Survey in the Galactic anticentre direction
extends to other distant fields that skirt the plane of the Milky
Way. New data, taken with the INT Wide Field Camera show a similar
population, narrowly aligned along the line of sight, but with a
Galactocentric distance that changes from ~15 kpc to \~20 kpc
(over ~100 degrees on the sky). Despite being narrowly
concentrated along the line of sight, the structure is fairly
extended vertically out of the plane of the Disk, with a vertical
scale height of 0.75+/-0.04 kpc. This finding suggests that the
outer rim of the Galaxy ends in a low-surface brightness stellar
ring. Presently available data do not allow us to ascertain the
origin of the structure. One possibility is that it is the wraith
of a satellite galaxy devoured long-ago by the Milky Way, though
our favoured interpretation is that it is a perturbation of the
disk, possibly the result of ancient warps. Assuming that the Ring
is smooth and axisymmetric, the total stellar mass in the
structure may amount to 2x10^8 up to 10^9 Solar masses.
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-- Amara Graps, PhD Istituto di Fisica delle Spazio Interplanetario (IFSI) Consiglio Nazionale delle Ricerche (CNR), Roma, ITALIA Amara.Graps@ifsi.rm.cnr.it
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