A Spatial Characterization of the Sagittarius Dwarf Galaxy Tidal Tails

TL;DR

This study maps the spatial density of Sagittarius dwarf galaxy's tidal tails using SDSS data, providing detailed parameters that align with some halo models and exploring the complex structure of the streams.

Contribution

It offers a comprehensive spatial characterization of the Sagittarius tidal streams, including a star density catalog and analysis of stream widths and halo shape, advancing understanding of galactic interactions.

Findings

The leading (North) tidal tail width matches recent halo model simulations.

The stellar halo in the North is oblate with q=0.53 and scale length 6.73 kpc.

Southern data do not fully match North model fits, indicating complex halo structure.

Abstract

We measure the spatial density of F turnoff stars in the Sagittarius dwarf tidal stream, from Sloan Digital Sky Survey (SDSS) data, using statistical photometric parallax. We find a set of continuous, consistent parameters that describe the leading Sgr stream's position, direction, and width for 15 stripes in the North Galactic Cap, and 3 stripes in the South Galactic Cap. We produce a catalog of stars that has the density characteristics of the dominant leading Sgr tidal stream that can be compared with simulations. We find that the width of the leading (North) tidal tail is consistent with recent triaxial and axisymmetric halo model simulations. The density along the stream is roughly consistent common disruption models in the North, but possibly not in the South. We explore the possibility that one or more of the dominant Sgr streams has been mis-identified, and that one or more of the `bifurcated' pieces is the real Sgr tidal tail, but we do not reach definite conclusions. If two dwarf progenitors are assumed, fits to the planes of the dominant and `bifurcated' tidal tails favor an association of the Sgr dwarf spheroidal galaxy with the dominant Southern stream and the `bifurcated' stream in the North. In the North Galactic Cap, the best fit Hernquist density profile for the smooth component of the stellar halo is oblate, with a flattening parameter q = 0.53, and a scale length of r_0 = 6.73. The Southern data for both the tidal debris and the smooth component of the stellar halo do not match the model fits to the North, although the stellar halo is still overwhelmingly oblate. Finally, we verify that we can reproduce the parameter fits on the asynchronous Milkyway@home volunteer computing platform.