Hotwiring the Transient Universe Understanding and Annotating LIGO-Virgo Probability Maps Roy...
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Hotwiring the Transient Universe
Understanding and Annotating LIGO-Virgo Probability Maps
Roy WilliamsLIGO Lab - Caltech
Hotwiring the Transient Universe
How to get your Nobel Prize for the GW-EM counterpart
• Apply to join the MOU group here– When approved register here
• Ask GCN to allow your IP-address to connect– send email to Scott and Teresa (section 1 here)
• Login to event database (Gracedb) here– and get a password (section 2 here)
• When VOEvent / GCN-Notice arrives, get the skymap– using your password– View it with Skymap Viewer – or process it with healpy– or with pygcn
• If you observe, share footprints at Gracedb
May 15, 2015 G1500607
Hotwiring the Transient Universe
How is LIGO followup different?
The Skymap
• Not a position. A probability distribution• represented with FITS/Healpix
• healpix.jpl.nasa.gov• sudo pip install healpy• EA in HEALPIX means all pixels on the sphere have
equal area• sample code and tech info here
• Should I observe?• If so, where?
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Hotwiring the Transient Universe
Next ....• Skymap Viewer
• Here is the open version with 1600 mock skymaps• Here for MOU partners• direct link from Gracedb
• And sharing footprints• like the minor planet center• don't observe what is already covered• we want to ask for the image itself if we need to
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Hotwiring the Transient Universe
Skymap Viewer
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N
S
EW
moon
view from Tasmania
Observations so far
Hotwiring the Transient Universe
Image and Catalog
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Click on the Layers icon
WHAT OTHER
CATALOGS HERE?
Hotwiring the Transient UniverseMay 15, 2015 G1500607
size of square is ~galaxy mass *
skymap
click the center to get Simbad and NED
70 Mpc
Hotwiring the Transient Universe
Zoom and drilldown
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• set image = DSS colored• keep zooming in ESO336-016• click the marker then NED link• much more data (eg 2MASS image)
zoom control
Hotwiring the Transient Universe
Gracedb: the LIGO event database• Communication: Click, Curl, or Code?
• clicking allows reading, experiment, understanding• a curl command is automatable and transparent• a code library integrates well with other code
– try pygcn
• Curl example
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curl --insecure --netrc https://gracedb.ligo.org/gracedb/apibasic/events/M137112/files/bayestar.fits.gz > M137112_bayestar.fits.gz
Hotwiring the Transient Universe
Reading a Skymap• Reading a skymap file
• Healpix/FITS– Process with healpy– View with Skymap Viewer (convert to json and load)
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map,header = healpy.read_map(filename, h=True)# map is a long vector of floats# header is dictionary of FITS header
# interpolate# th is codeclination (radians), ph is RA (radians)probability = healpy.pixelfunc.get_interp_val(map, th, ph)
# handle every pixelnside = healpy.get_nside(map)(th, ph) = healpy.pix2ang(nside, i)probability = map[i]
Hotwiring the Transient Universe
Using Gracedb for Sharing• EM followup
• Shared messages from LV-EM partners• GCN Circulars
• EM Observations • Footprints (required by MOU)• Candidates• Visualizing shared effort
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From the MOU
Hotwiring the Transient Universe
Using Gracedb for Sharing
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gracedb.ligo.orgcollapse the Event Log Messagesopen the "EM followup" and "EM Observations"
Like GCN Circulars (includes them)
observation footprints
Hotwiring the Transient Universe
Sharing observation footprints
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comma-separatedRA, Dec lists RAwidth, Decwidth can be list
You don't need to click a web form you can• build a curl command• use pygcn
click,
curl,
or code
Hotwiring the Transient Universe
Footprints in Skymap Viewer
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Open the "Sky Localization" tab
Click the gray button
Hotwiring the Transient Universe
Footprints in Skymap Viewer
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Hotwiring the Transient Universe
Helping the follow-uppers• Nearby galaxy catalogs
• To ~200 Mpc• Got any more?
• Galaxy cluster catalogs• Suggestions welcome• But most galaxies not in clusters
• Light curves• has this object been variable before• forced photometry services from surveys?
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Hotwiring the Transient Universe
Helping the follow-uppers• Most likely galaxies
• Catalog with rate prior (eg galaxy luminosity)• Multiply by skymap probability
• Ordered list of your fields• Sky tesselated into YOUR rectangular fields
– which have most dark sky + probability?
• Personal alarm for GW events• When YOUR telescope has a chance
– dark sky + probability > X steradians
May 15, 2015 G1500607