Liverpool Telescope 2

Transcription

1 Liverpool Telescope 2 Chris Copperwheat Liverpool Telescope group: Robert Barnsley, Stuart Bates, Neil Clay, Chris Davis, Jon Marchant, Chris Mottram, Robert Smith, Iain Steele

2 Liverpool Telescope 2 The LT in its current state should continue to be a leading time domain facility for the next ~5 years The next generation of synoptic surveys (and other discovery facilities will both probe deeper and provide much of the follow-up photometry 'for free' Since Sept 2012 we have been conducting a feasibility study for a new 'Liverpool Telescope 2' facility, to come into operation ~2020 Feasibility study effectively came to an end this autumn with the results of our initial optical design studies and public release of our science white paper: arxiv: We are now constructing an internal business case for the university management as well as preparing funding applications with a view to beginning serious design work next year

3 Motivation: transient science Synoptic surveys such as PTF, Pan-STARRS, Skymapper provide large numbers of transients detected at early times LSST will probe the 'faint and fast' regime of this transient phase plot ~1e6 alerts per night! After accounting for NEOs and variable stars, still 1000s of targets for follow-up Huge need for low to intermediate R spectroscopic follow-up for classification and exploitation: PESSTO demonstrates this can be extremely productive Rapid reaction for features which evolve over the first day, shock breakout phase, etc. Figure adapted from LSST science book and Rau et al (2009)

4 Motivation: transient science SN 2011fe: Nugent et al. (2011) Synoptic surveys such as PTF, Pan-STARRS, Skymapper provide large numbers of transients detected at early times LSST will probe the 'faint and fast' regime of this transient phase plot ~1e6 alerts per night! After accounting for NEOs and variable stars, still 1000s of targets for follow-up Huge need for low to intermediate R spectroscopic follow-up for classification and exploitation: PESSTO demonstrates this can be extremely productive Rapid reaction for features which evolve over the first day, shock breakout phase, etc.

5 Motivation: GRBs and GWEM Fast fading afterglows means a fast slewing telescope can potentially collect more photons than a slower telescope of much larger aperture Plenty still to do in post-swift era: High z bursts for cosmological parameters, reionisation, etc. Mundell et al. (2013) Low to intermediate z bursts for GRB-supernova associations, short GRB progenitors, particle acceleration, radiation processes, internal shocks Gravitational wave counterparts aligo/avirgo full sensitivity by ~2022 NS/NS or NS/BH mergers Poor localisation, uncertain EM signature

6 Other time domain facilities in Transiting exoplanets: NGTS ( ), TESS (2017+) and PLATO (2022+) all targeting bright stars to maximise follow-up potential Gaia: final catalogue will be published in 2020 SKA: full science operations 2020 (phase 1), 2024 (phase 2) Limited photometry and very limited spectroscopy. Millions of variables and binaries. Statistically complete samples, rare subclasses... Pulsars, RRATs, AXPs, SGRs, NS-NS binaries, synchrotron emission from jets, coherent emission from flare stars, brown dwarfs and hot Jupiters... Cherenkov Telescope Array: begins construction ~2018 AGN, GRBs, pulsars, XRBs...

7 LT2 design requirements - summary A new, 4-metre class robotic Ritchey Chrétien telescope for rapid follow-up of astrophysical transients To be co-located with the LT on La Palma First light ~2020 to capitalise on the next generation of synoptic surveys, CTA, Advanced LIGO/Virgo, etc. Primary instrument will be a high-throughput, optical-infrared, intermediate resolution (R < 10,000) spectrograph Focal stations for the simultaneous mounting of at least 4 other instruments Extremely rapid reaction for fast-fading and fast-evolving objects. On target and taking data within ~30 seconds of receiving a trigger

8 Fast primary mirror for fast slewing Mechanical design more challenging than optics. Minimise moment of inertia for fast slewing Key issues are: weight of mirror, materials for structure, choice of focal stations for instruments... Our optical design studies advocate a RC design with an f/1 f/1.5 primary and an f/6.5 f/10 final focal ratio Faster primaries reduce primary -secondary distance However longer final focal length allows for a reduced secondary mass which can more than compensate for increased length

9 Segmented primary to reduce mass For fast slewing, the mass of the primary mirror is very important 4m thin meniscus primary has a mass ~5500kg 6 segment mirror, total mass 2700kg 18 segments, total mass 1400kg 36 segments, total mass 920kg

10 Angular resolution To phase or not to phase? Factor ~100 difference in alignment tolerances between simple co-alignment and optical phase coherence 6 segments for a ~4m effective aperture could have same dimensions as GTC segments (1.87m corner to corner)

11 Future of LT1 Two potential options: 1) For some of our optical layout concepts, LT2 will fit inside the existing enclosure. Upgrade LT1 to LT2? 2) Replace LT1 instrument suite with wide field, prime focus imager. 2x2 deg FoV, ugriz filters, low resolution spectrograph fibre. Run both telescopes as a combined rapid reaction robotic facility

12 Funding Cost of the project currently estimated at ~ 15M ( 20M) ~10% of that figure is the cost of the LT1 upgrade Internal feasibility study now at an end. Business case under development and will be presented to the university before the end of the calendar year We are pursuing a number of channels of European regional development funding Opportunities for contribution from Canary Islands regional government / Spanish national government Other partners

13 Timeline

14 Next steps We are currently finalising the optical design We are now looking into the issues of mechanical design: mirror support, mass balance, novel materials (SiC, carbon fibre?) Establish our first-light instrumental needs in more detail Opt-IR intermediate resolution spectroscopy What else? High cadence photometry? Polarimetry? Technologies for high time resolution. EMCCDs, CMOS, Kinetic Induction Detectors sec observation of Crab pulsar with ARCONS detector (O'Brien et al. 2012)

15 Summary We intend to build a new 4m class telescope to come into operation on La Palma at the beginning of the next decade Telescope will be fully robotic with all the versatility that entails Likely a six segment f/1.5 primary with final focal ratio ~ f/8 Time domain science with a focus on transients. Very rapid response for fast-fading objects Intermediate resolution spectroscopy, but provision for a diverse array of simultaneously mounted instrumention Future of LT: Replace current instrument suite with prime focus wide field (2x2 deg) camera? For more information: Science white paper: arxiv: LT2 website:

16 Summary We intend to build a new 4m class telescope to come into operation on La Palma at the beginning of the next decade Telescope will be fully robotic with all the versatility that entails Likely a six segment f/1.5 primary with final focal ratio ~ f/8 Time domain science with a focus on transients. Very rapid response for fast-fading objects Intermediate resolution spectroscopy, but provision for a diverse array of simultaneously mounted instrumention Future of LT: Replace current instrument suite with prime focus wide field (2x2 deg) camera? For more information: Science white paper: arxiv: LT2 website:

17 Segmented primary mirror? As well as reducing the total mirror mass, more segments makes operations much easier handling, re-coating etc. However, segment alignment becomes a more complicated issue Steep rise in the polishing and testing cost with number of segments is due to the increased number of family groups

18 Site Northern and southern sites both viable for our science: synoptic transient surveys in both hemispheres, targets from space facilities, GW detections over whole sky, etc. La Palma the ideal choice: a world class site which we know well, co-located with LT which simplifies logistics (and potentially provides some scientific benefits) La Palma (29 N) still provides excellent access to a large fraction of the LSST field From La Palma: Dec -30, 1.5h TOT at airmass < 2.0 Dec -20, 4h TOT at airmass < 2.0 1h TOT at airmass < 1.5 Dec -10, 6.5h TOT at airmass < 2.0 4h TOT at airmass < 1.5

19 Site Northern and southern sites both viable for our science: synoptic transient surveys in both hemispheres, targets from space facilities, GW detections over whole sky, etc. La Palma the ideal choice: a world class site which we know well, co-located with LT which simplifies logistics (and potentially provides some scientific benefits)

20 LT2 discussion: user requirements Effective wavelength range: Relative importance of optical vs. infrared? No AO: design requirement is that IQ is limited by La Palma seeing (typically 0.8 ) Field-of-view 300nm to 2.4 micron desirable Image quality: 350nm to 2.0 micron essential At least 15 arcmin diameter (wide field imaging from LT1) Elevation range ideally down to horizon to maximise capability to exploit Southern targets Acquisition time not limited by enclosure (clamshell design?) Excellent open loop tracking so autoguider not required for fast-fading transients

21 LT2 discussion: instrumentation Primary instrument R <10,000 Much lower R acceptable for SNe studies? R ~ 100 mode for classification? Wavelength range X-shooter like instrument covering entire range? Or optimised for a particular range? Long slit or IFU? Other instrumentation High cadence imaging (RISE/ULTRACAM/HyperCam) Simultaneous imaging in many bands for SED modelling (GROND) Polarimetry. Higher polarisation accuracy than is currently possible with RINGO3?

22 LT2 discussion: LT1 upgrade Prime focus imager would be the only LT instrument Significant fraction of time dedicated to NSO Cost ~ 1.5M (10% of LT2 budget) 6k x 6k CCDs. 0.5 /px Total on-sky area ~2.8 sq deg. griz and white light filters (considerably cheaper with fixed filters!)

23 Robotic time domain session at EWASS 2015 registration opens in Dec

24 LT2 discussion: LT1 upgrade Prime focus imager would be the only LT instrument Significant fraction of time dedicated to NSO Cost ~ 1.5M (10% of LT2 budget) 6k x 6k CCDs. 0.5 /px Total on-sky area ~2.8 sq deg. griz and white light filters (considerably cheaper with fixed filters!)