# The stream gap DF¶

class galpy.df.streamgapdf(*args, **kwargs)[source]

The DF of a gap in a tidal stream

__init__(*args, **kwargs)[source]

NAME:

__init__

PURPOSE:

Initialize the DF of a gap in a stellar stream

INPUT:

streamdf args and kwargs

Subhalo and impact parameters:

impactb= impact parameter (can be Quantity)

subhalovel= velocity of the subhalo shape=(3) (can be Quantity)

timpact time since impact (can be Quantity)

impact_angle= angle offset from progenitor at which the impact occurred (rad) (can be Quantity)

Subhalo: specify either 1( mass and size of Plummer sphere or 2( general spherical-potential object (kick is numerically computed)

1( GM= mass of the subhalo (can be Quantity)

rs= size parameter of the subhalo (can be Quantity)

2( subhalopot= galpy potential object or list thereof (should be spherical)

3( hernquist= (False) if True, use Hernquist kicks for GM/rs

deltaAngleTrackImpact= (None) angle to estimate the stream track over to determine the effect of the impact [similar to deltaAngleTrack] (rad)

nTrackChunksImpact= (floor(deltaAngleTrack/0.15)+1) number of chunks to divide the progenitor track in near the impact [similar to nTrackChunks]

nKickPoints= (30xnTrackChunksImpact) number of points along the stream to compute the kicks at (kicks are then interpolated); ‘30’ chosen such that higherorderTrack can be set to False and get calculations accurate to > 99%

nokicksetup= (False) if True, only run as far as setting up the coordinate transformation at the time of impact (useful when using this in streampepperdf)

spline_order= (3) order of the spline to interpolate the kicks with

higherorderTrack= (False) if True, calculate the track using higher-order terms

OUTPUT:

object

HISTORY:

2015-06-02 - Started - Bovy (IAS)