The alignment of SDSS satellites with the VPOS: effects of the survey footprint shape

Understand

It is sometimes argued that the uneven sky coverage of the Sloan Digital Sky Survey (SDSS) biases the distribution of satellite galaxies discovered by it to align with the polar plane defined by the 11 brighter, classical Milky Way (MW) satellites.

• This might prevent the SDSS satellites from adding significance to the MW's Vast Polar Structure (VPOS).
• We investigate whether this argument is valid by comparing the observed situation with model satellite distributions confined to the exact SDSS footprint area.
• We find that the SDSS satellites indeed add to the significance of the VPOS and that the survey footprint rather biases away from a close alignment between the plane fitted to the SDSS satellites and the plane fitted to the 11 classical satellites.