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cmateu / galstreams

Milky Way Streams Footprint Library and Toolkit for Python
BSD 3-Clause "New" or "Revised" License
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Spatial and Kinematic masks for a stream #43

Open DebajyotiS opened 2 weeks ago

DebajyotiS commented 2 weeks ago

Hi, I have the GDR3 catalogue (divided in ~153 patches) downloaded on my disk, and I was wondering if I could use the galstream library to filter out the known streams in them. I see there's a polygon mask method get_mask_in_poly_footprint. Would it be possible to do this with the proper motions, as well as ra/dec of the sources?

Would something like make sense to add?

catalogue = ac.SkyCoord(ra=data[:,0]*u.deg, dec=data[:,1]*u.deg, pm_ra_cosdec=data[:,3]*u.mas/u.yr, pm_dec=data[:,4]*u.mas/u.yr, frame='icrs')
stream_catalogue = ac.SkyCoord(ra=mws[track_name].track.ra, dec=mws[track_name].track.dec, pm_ra_cosdec=mws[track_name].track.pm_ra_cosdec, pm_dec=mws[track_name].track.pm_dec, frame='icrs')

dx, d2d, d3d = ac.match_coordinates_sky(catalogue, stream_catalogue)
matches = d3d < 0.0001 # adjustable threshold, choosing 1E-4
matched_stars = catalogue[matches]

Regards, Deb

cmateu commented 1 week ago

Dear Debajyoti,

Right now that functionality is not included. On a separate project we are working on some functionality that would allow for this, but its not yet publicly available.

About the widths, not really, this depends on each individual stream. I have been working on this and a functionality with the apparent widths reported for the available streams will be included in the next release (in a about a month or so).

Best,

Cecilia

On Jun 18, 2024, at 6:04 AM, Debajyoti Sengupta @.***> wrote:

Hi, I have the GDR3 catalogue (divided in ~153 patches) downloaded on my disk, and I was wondering if I could use the galstream library to filter out the known streams in them. I see there's a polygon mask method get_mask_in_poly_footprint. Would it be possible to do this with the proper motions, as well as ra/dec of the sources?

Additionally, is there a principled way to infer what the 'width' threshold should be for a given stream? I refer to width and phi2_offset in mws[st].create_sky_polygon_footprint_from_track(width=1.u.deg, phi2_offset=3.5u.deg) from the same tutorial.

Regards, Deb

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