LSST constraints on stellar streams

[jobovy]

How can spectroscopic follow-up help in constraining the subhalo mass function using LSST (and other) data?

cc @sazabi4

[jobovy]

Discussion between @segasai, @sazabi4, and @jobovy:

• Investigate how much the improved photometric precision of LSST will improve stream membership using a CMD filter; test with mock Pal 5 and GD-1 data? What density S/N can you get down to LSST nominal depth (r ~ 27).
• If you get 0.5 km/s precision on vlos for stars down to 20 mag, how good can you constrain the subhalo mass function? For Pal 5, how many stars does that get, or for GD-1?
• Is there a regime where we can find nearby substructure in LSST that Gaia cannot find: e.g., 50 Msun dwarf galaxy at 10 kpc?
• Can we detect streams and other diffuse structure by combining Gaia proper motions for the brightest stars (giants) and LSST photometry lower down.

[jobovy]

Main site of the hack: lsstdarkmatter/stream_gap_lsst.

[segasai]

I attach the figure that shows the alleged limit on the halo masses for streams of different surface brightnesses at different distances. We look for single stream gaps 0.5 Gyr after the interaction. We assume the photometric model of LSST.

[segasai]

The plot shows the halo mass limit when taking into account the filling of the gaps. I.e. very short gaps they would fill very quickly therefore we cannot afford waiting for 0.5Gyr.