Linking Optical and Infrared Observations with Gravitational Wave Sources.

1. Linking Optical and Infrared Observations with Gravitational Wave Sources. • Christopher Stubbs • Department of Physics • Department of Astronomy • Harvard University • stubbs@physics.harvard.edu

2. Some assertions More celestial events have been seen at optical and IR wavelengths than have been detected in gravity waves. Next generation surveys will detect essentially all celestially variable sources, to 22nd magnitude, with variability that lasts more than a few days, across entire sky*: Supernovae, Quasars/AGN… things that go bump in the night… (*except for ones hiding behind Galactic disk) Science would benefit from better coordination between gravity wave and optical variability community.

3. Some questions What is the relationship between emission of gravity waves, and optical/infrared (OIR) radiation? What OIR variability accompanies GW emission? How can optical/IR observations be used in conjunction with GW data (either detections or upper limits) to add to our understanding?

4. Linking OIR and GW data Tough, due to OIR source confusion Optical view of the sky We’re pretty good at this Gravity wave view of the sky This link makes the most sense to me Optical variability

5. Image Subtraction (High-z Supernova Team)

6. Variability is helpful for GW optical too • Pointing accuracy for eventual GW detections is ~ 1 degree • Optical/IR source density is high • If we limit attention to variable sources, candidate list is 2-3 orders of magnitude smaller.

7. Core collapse Supernovae as an illustrative example 25 solar mass progenitor at 10 kpc SNR~100 at 10 kpc So LIGO might see collapse of higher mass objects out to 1 Mpc (i.e. M31)? A New Mechanism for Gravitational Wave Emission in Core-Collapse Supernovae. Ott, C. et al., PRL 96, 1102 (2006)

8. A super-dupernova from a 100 solar mass progenitor? Most luminous SN ever seen, 75 Mpc away. Went off during LIGO’s S5 run! Optical signature is huge, what GW signal? We think we may have detected another example at z~0.8 in ESSENCE survey N. Smith et al., astro-ph/0612617

9. One estimate of optical counterparts to merging NS-NS binaries PanSTARRS Sylvestre, J, ApJ 591, 1152 (2003)

10. Optical/IR search options Look at specific galaxies KAIT survey Look at galaxy clusters Mt. Stromlo cluster search Wise observatory search 3. Look at the whole sky* Killer asteroid surveys: (Spacewatch, NEAT, LINEAR, LONEOS…) GRB afterglow surveys: ROTSE, WASP… Next generation: PanSTARRS, Skymapper, LSST… All-sky cameras, both optical and IR

11. System: Collecting Area Field of View Efficiency Survey Figure of Merit Source flux, signal to noise Site: sky brightness, seeing For a given site the system’s effectiveness scales as the A-Omega product, times the fraction of time allotted to the survey. Sensitivity to faint sources depends on aperture, not field of view. Note this simple A-Omega product neglects issues of pixel sampling, site sky brightness, etc. Dynamic range per image is typically ~6 magnitudes. Can extend dynamic range to ~10 magnitudes using different exposure times.

12. better

13. Some OIR Survey Systems Tradeoff between revisit cadence and sensitivity

14. What about the Infrared? • Wavelength dependence of extinction favors an IR variability survey of the Galactic plane. • IR does better for attenuation around merging binary pairs too. • Wavelengths beyond 2 microns are really tough from the ground, due to blackbody emission from the atmosphere. • UKIDSS survey has recent paper on single epoch Galactic plane survey, but I don’t know of any plans to do IR all-sky. • Absolute magnitude of type II in K band is K ~ -18. • A type II behind 100 magnitudes of V band extinction would be readily detectable with ~1 m class telescope.

15. Existing surveys already enable “optically triggered” science Can use optical detections to run constrained “burst” search in GW data. Known distances means can set SI unit limits on rate of change of quadrupole moments. Great recent example of looking for GW signature from external trigger is: LIGO team & Hurley, Implications for the Origin of GRB 070201 from LIGO Observations, (arXiv:0711.1163)

16. SNe that coincided with S5

17. Some are of potential interest… 762 supernovae during S5 411 core collapse (spectral confirm.) 89 in named galaxies

18. Went to “virtual observatory”

19. Closest Few

20. One potential search scheme Locations known to subarcsec accuracy, plus redshifts. This implies arrival time differences at different GW antennas are known to dt ~ d * L/c ~ (5E-6)*(1000 km)/c ~ tens of nanosec. Delay between optical peak flux and GW transient is unknown. So do fixed-delay autocorrelation analysis, sliding over plausible window in arrival time. This amounts to blending the burst detection algorithms with known-source analysis. Could also imagine a stacking scheme, that averages over multiple optical trigger events (Bence Kocsis).

21. Imminent (~12 mo) PS 1 on Haleakala • PanSTARRS 1 • 1.8 m aperture • 7 square degree field • 1.4 Gpix imager • Deep depletion detectors • Latitude +20 • Skymapper • 1.35 m aperture • 5.7 sq degrees • Bands optimized for stellar astronomy • Latitude 30

22. PanSTARRS first light image of M31, Andromeda galaxy. PS-1 should detect anything of interest in M31, in its microlensing survey data set, from 2009-2011.

23. PanSTARRS-1: 200 supernovae/month! 1.8m telescope, 7 square degree FOV Telescope now in shakedown 1.4 Gpix camera, first light in Sept 2007 Image processing pipeline runs end-to-end Operations likely to begin late 2008 Expect ~ 1 orphan afterglow visible at any time

24. In the Planning/Design phase • Dark Energy Survey • Equip CTIO 4m with 3 sq deg camera • 1/3 of the time, 5 year survey • Cluster photo-z’s, SNe, Weak Lensing, LSS • PanSTARRS 4 • Four 1.8m telescopes, PS-1 is prototype • Large Synoptic Survey Telescope • 8.4m aperture • 9.6 sq degree field

25. Large Synoptic Survey Telescope Highly ranked in Decadal Survey Optimized for time domain scan mode deep mode 10 square degree field 6.5m effective aperture 24th mag in 20 sec >20 Tbyte/night Real-time analysis Simultaneous multiple science goals

26. LSST Merges 3 Enabling Technologies • Large Aperture Optics • Computing and Data Storage • High Efficiency Detectors

27. One blind spot = The Milky Way Spans large solid angle on the sky, Galactic center is at 18 degrees South. LSST might not even observe at low galactic latitude, due to high stellar densities (!). Disk of Galaxy has high extinction in the optical due to “dust”. This produces the “zone of avoidance” in galaxy catalogs, etc. But the MW sources we’re seeking (from the GW context) are going to be really bright transients in the optical/IR. These considerations motivate an on going modest-aperture wide angle IR survey that includes the plane of MW.

28. Another blind spot: Really bright things! A type II SN in M31 would peak at about m = 19  24.3 = 5th magnitude. This is really bright! LSST will saturate on objects 105 X fainter! At present we do not have a well-thought-out strategy to hand off objects across the system of telescopes of different apertures, as they rise and fall in brightness. There are calibration challenges due to mis-matched filters and detector efficiencies vs. wavelength.

29. All-sky cameras exist already ConCam project R. Nemiroff, MTU http://nightskylive.net/index.php Is anyone mining this open-access data set to search for bright (nearby) transients?

30. Some Opportunities Undertake “pointed” GW analysis to look for transient signals associated with known SNe. Maybe even co-add? Ensure optical coverage of all local group galaxies, especially our own, to detect bright transients. Although rare, let’s not miss it! Undertake frame subtraction processing of ConCam data set, and other similar all-sky imagers, taking care to not suppress saturation-level sources. Consider in more detail the likely OIR signatures of inspiraling GW sources, and coordinate with large-aperture surveys (PanSTARRS, LSST…).

31. Some Open Questions Won’t most detectable GW sources have accompanying OIR variability? How detectable is this? Is there merit in establishing coordination and data reduction pipeline for existing all-sky survey programs? Drawing a lesson from GRB science, where xray and optical data did better jointly than separately, how can we best merge xray, OIR, neutrino and gravity wave data?

32. Summary Optically triggered GW analysis will deliver real science from upper limits, and eventually linking detections to optical counterparts will aid interpretation: Characterize astrophysics of sources Independent determination of both redshift and distance Optical all-sky surveys (down to faint flux levels) will soon be in operation. We should be able to correlate optical variability with inspiraling compact object pairs, assuming OIR emission, even if variability is subtle. We are less well instrumented/organized for early detection of bright SNe in the local group of galaxies. SN 1987A in LMC was found by eye! Two decades later, this would likely again be the case.