Time Domain Astronomy in the 2020s: Developing a Follow-up Network R. Street Las Cumbres Observatory Workshop
Movies of the Sky Vary in depth, sky region, wavelengths, cadence Many will produce alerts Workshop
Time Domain Astronomy Pathfinders OGLE 25 year anniversary Catalina Sky Survey ASAS-SN SuperWASP Palomar Transient Factory/iPTF Part 2: SOAR's Role
Time domain surveys are growing in capabilities Data used to identify targets of interest alerts Additional observations may be needed to characterize targets Trade-offs in survey design constrain parameter space of alerts Hard to satisfy everyone all of the time! LSST evaluating the impact of different strategies by region of sky/galaxy by time (excluding short or long) by rarity/volume-limited sample
Survey Alerts Dominated by wide-field, deep and high-cadence surveys Extremely high alert rate [Ridgway+2014] Wide range of moving, transient and variable object science [E.g. LSST Science Book] Zwicky Transient Factory LSST
The Alert Rate Challenge From Ridgway+ 2014
The Alert Rate Challenge Based on LSST Science Book
The Alert Rate Challenge From Ridgway+ 2014
Many science goals will depend on follow-up Science Goal Observations Telescope aperture Milky Way halo spectroscopy formation, Dark Matter wide-field imaging halos IR imaging 8m+ 4m+ 8m+ Gravitational wave sources, SNe spectroscopy optical/nir imaging 3-30m <3m Stellar rotation, magnetic activity wide-field imaging MOS spectroscopy OIR spectroscopy <3-5m 5-8m >25m NEOs, asteroids, comets, TNOs Imaging/astrometry optical/nir imaging hi-speed imaging spectroscopy <3-5m 8m 8m 8m 8-25m Evolution of baryons, BH, cosmic structure spectroscopy wide-field imaging 8-30m 4-6.5m Cosmology spectroscopy AO imaging spectroscopy 4-8m 8-30m 8-30m Summarized from Najita, Willman et al. 2016, asxiv: 1610.01661.pdf
Alert Rate in Context To plan for 2020s, let's draw on experience with current surveys What alert rate do we see from current projects? How do existing follow-up programs handle these alerts? How many can we handle with the resources we have? What tools do we have for this? Are they enough for surveys in 2020s?
Examples of Current Follow-up Programs Supernovae Near-Earth Asteroids Observations Spectra, multiband imaging Short timeseries imaging Cadence ToO alert then Every 1-3d for >month Rapid-response short (<1hr) series, daily for 1-3d Microlensing Timeseries imaging Medium-high cadence continuous monitoring for weeks
Examples of Current Follow-up Programs Supernovae Total alerts/year New alerts/day Followed/day ~700 ~2 40-60 Near-Earth Asteroids ~5400 ~100 ~10 Already have more alerts than we can follow! Tools developed for target selection and observations Use existing programs as proving grounds for LSST Microlensing ~2100 ~8 ~10
Paradigm Shift in Resource Distribution/Allocation Fixed allocation at single telescope Observe whatever's visible Phenomena occur at specific time/interval Observe with whatever facility is suitable
Paradigm Shift in Resource Distribution/Allocation Instrumentation/aperture facilities needed at multiple locations Will often need to combine data gathered from multiple locations Similar instrumentation ideal for ease of calibration/analysis
Keeping track of alerts: Brokers Many projects require similar functionality... Subscribe to multiple alert feeds Track evolving status of lots of targets Cross-match catalogs Searchable Process updates......but highly configurable access & display Different data products Different display requirements Different selection filters Different collaborator access requirements
Target Selection Highly project-specific Algorithms constantly being developed Role for general-purpose classifiers common metrics Expect high traffic Targets evolve classification needs reevaluation Enable user-configurable filters Brokers can ingest user classifier metrics Handle high traffic of search queries More work needed on classifiers for a range of science purposes
So many targets, so little time... Multiple teams will follow-up subsets of the same targets, using the same finite telescope resources Need careful target selection Follow-up programs need to be smart and highly efficient Coordinate follow-up of targets efficiently wherever possible
Follow-up for Time Domain Targets Transients, periodic, aperiodic, outbursts, moving... Require follow-up for a variety of science goals Higher cadence timeseries for fast features Spectroscopic classification/evolution Orbital parameter determination... Require follow-up on a wide range of timescales 10 mins every week for 4 years 4 hours once every 3.4 days 1.5hr every 3 days for 2 months 5 mins every 15min for 4 days... Rapid (~mins) reaction capability needed Require observations from a range of instruments Require follow-up from both hemispheres Moving objects Around-the-clock monitoring Resource distribution...
Paradigm shift: Coordinated follow-up I do my thing and publish my few targets More candidate targets than resources, some false alarms Scarce target model Resource-limited model Time domain targets often need substantial telescope time Candidates + false alarms can overwhelm follow-up resources Projects want independence top-down uber-management doesn't work Flexible, coordinated response most efficient Sociological change against data/target protectionism Encourage data sharing for targets AND false positives Funding for public archiving of data products
Alert Triage Different science drivers suffer a range of false positives and rates Triage observations necessary Perform short obs to confirm classification, used to prioritize targets and decide subsequent follow-up strategy Rejected targets could be of interest to other projects! Encourage prompt data release Brokers can be data sharing platforms Encourage publication of false positives
Alert Triage Different science drivers suffer a range of false positives and rates Triage observations necessary Perform short obs to confirm classification, used to prioritize targets and decide subsequent follow-up strategy E.g. hi-res spectroscopy of transit planet candidates low-res spectroscopy for transient classification But...it's a thankless task - difficult to publish results - no support from TAC - punishing on early-career researchers Community-wide support necessary
Outline Follow-up Network Databases automatically query for new targets Submit requests for observations and keep track Get status info + data back
SOAR's Role Science Goal Observations Telescope aperture Milky Way halo spectroscopy formation, Dark Matter wide-field imaging halos IR imaging 8m+ 4m+ 8m+ Gravitational wave sources, SNe spectroscopy optical/nir imaging 3-30m <3m Stellar rotation, magnetic activity wide-field imaging MOS spectroscopy OIR spectroscopy <3-5m 5-8m >25m NEOs, asteroids, comets, TNOs Imaging/astrometry optical/nir imaging hi-speed imaging spectroscopy <3-5m 8m 8m 8m 8-25m Evolution of baryons, BH, cosmic structure spectroscopy wide-field imaging 8-30m 4-6.5m Cosmology spectroscopy AO imaging spectroscopy 4-8m 8-30m 8-30m Summarized from Najita, Willman et al. 2016, asxiv: 1610.01661.pdf
SOAR's Role 4m-class telescopes will be in demand for optical/nir imaging, spectroscopy Alert triage facility rapid-response to new discoveries Co-located with LSST Interim cadence observations of high-priority targets complementary pre-observations of selected targets Part 2: SOAR's Role
SOAR's Role Co-located with LSST Interim cadence observations of high-priority targets complementary pre-observations of selected targets potential for rapid response to survey discoveries Coordinate with other 4m-class facilities worldwide, esp. Blanco A one-off in a follow-up network single 4m-class facility unique instrumentation complementary aperture Part 2: SOAR's Role
Connecting SOAR with a Follow-up Network Control interfaces for manual, remote-access and/or full-robotic modes Complexity in supporting multiple instruments Focus on fewer, high-volume instruments Scheduling modes Queue- and rapid response-mode (~mins) Open ToO mode, similar to Swift? Part 2: SOAR's Role
Connecting SOAR with a Follow-up Network Time allocations Time-sharing agreements to gain access to similar facilities in complementary locations Allocate time for triage? Data access drives pipeline and archive development Investigate what data products users need Investigate on what timescale they need to access the data Automated data reduction takes concerted development effort Need API access to data archive with reduced products available in <hour Personnel to develop and support pipelines/archives Part 2: SOAR's Role
Pathfinder: WISE 1m integrated with LCO Network 1m telescope built in 1971 Previously manual LCO-Israel partnership: Will host new LCO NRES echelle spectrograph New software interface allows robotic observations to be requested through LCO network scheduler Tel Aviv University It's possible to link a diverse range of facilities into a coordinated follow-up network Part 2: SOAR's Role
SOAR in a Follow-up Network Follow-up engine for the 2020s Could be a rapid-reaction follow-up partner for LSST Development needed, esp. software Pave the way to integrate larger facilities in wider follow-up network Part 2: SOAR's Role