Minutes of Belfast PESSTO Meeting, 16/09/11

Science goals (Stephen Smartt (SJS) talking):

There was some discussion of the scheduling. SJS made point that scheduling is balance between science goals and logistics. There was a consensus that we want three runs per lunation, but the precise timing of these runs, and the mix of dark and bright time was debated.

Brian Schmidt (BS) - Could we take dark, first quarter and third quarter to avoid bright time? Massimo Turatto (MT) - Shift scheduled nights forward by three nights? SJS - This need to be decided by Monday. BS - Getting optical spectra within two days of full moon is hard. Stefano Benetti (SB) - We may not get precisely (to plus or minus a couple of days) what we ask for, especially if there are visitor instruments on the NTT.

It was agreed that the schedule (as it stands) would be shifted 3 days earlier - giving three nights of partial dark time, as opposed to two full dark and one bright. SJS changed this in the submitted Survey Management Plan (SMP)

The overlap between PESSTO and the Benetti Large Programme was discussed. SJS suggested that Benetti time should be included in a Pessto-like schedule, SB and SJS are to discuss this further and agree a plan. To be done when ESO review PESSTO SMP and schedule for Period 89 is due

It was agreed not to specify which nights we will use EFOSC and SOFI in proposal - as we wish to keep maximum flexibility.

There were no objections to the 9 months on / 3 months off schedule.

SJS will circulate "allocation of resources" table. People from individual institutes are complete this table to supply info to SJS on personnel they will provide. DONE

Michel Dennefeld (MD) - Should we put 12 hr data reduction guarantee to ESO in plan? MD suggested keeping this as an internal goal, but giving a more conservative commitment of data reduction within 24 hr in the ESO management plan. DONE


Feeder surveys (Skymapper, LaSilla Quest and CHASE)

BS gave an overview of Skymapper. 6-colours, 3 day cadence, and a coverage of ~1250 sq deg per night for finding SNe.

  1. 200 SNe Ia per year ; ~20 SNe Ia per month
  2. 30 type II per yr (z~0.04) ; 30 type Ibc per yr (z~0.06)

Charlie Baltay (CB) gave an overview of the LaSilla quest. Only one filter (broad optical), but good cadence and depth, and the survey is already finding large numbers of variables (RR Lyrae stars)

CB is open to suggestions from PESSTO as the survey strategy which LSQ will adopt. The coverage on sky can be optimized for SN search. At present LSQ is planning to cover +25 to -25. SJS - Go further south to find targets. SB - Hard to follow stuff above +30 with NTT

Joe Anderson (JA) gave an overview of CHASE overview. At present, CHASE is using the PROMPT telescopes, but these are failing and they do not have priority. Hence, CHASE are building their own 0.5m telescope for a dedicated survey. They are looking for very young SNe, and so are interested in the possibility of triggering in real time if there is a NTT run ongoing on the same night as they discover a SN candidate.

There was then some discussion as to the general philosophy of SN followup Andrea Pastorello (AP) - Do we need to follow objects with as frequent spectra and lightcurves as those obtained by CHASE for eg 08bk? It is a lot of work which gives an impressive figure, but does not add much scientifically over a less frequently sampled lightcurve. BS - PIs do get more spectra than they need - no need for daily spectra after the very earliest times. But a PI will always try to get as much data as possible for their SNe. Nancy Elias-Rosa (NER) - But we do not know how new SN types and peculiar objects will evolve - hence we need frequent spectra and densely sampled lightcurves.


Target and alert team (TAT) -AP

Any collaboration member can propose a target. But TAT has final choice. TAT to be split into two groups - one comprised of representatives of feeder surveys, and one of people who are not in surveys. We also need to monitor discoveries from amateurs and other surveys. The TAT needs to know the current magnitude and evolution of SNe we are following.

WH - Why can't we have PIs for different groups of transients (eg. a PI for broad-line Ic's etc). They would then advise the TAT to help decide the strategy for individual objects we are following. SJS - If we decide to set up science groups/PIs within the collaboration, we can reconstitute the TAT with new members (eg. Survey liasons, AP's team and science PIs)

What is the maximum amount of time per target? Or time/targets per transient sub-group/node? SJS - The policy should be developed at Board level. The TAT can then focus on operations and implementing the policies.

There was then some discussion as to whether the TAT decides which targets are to be classified.

  • Kate Maguire (KM) - most targets are going to be discovered less than 3 days before run.
  • Stefano Valenti (SV) - Should leave decision on what to classify solely to observer.
  • BS - Should establish criteria as to what priority targets are assigned. The potential classification targets can then be ranked, and the observer can decide what to classify, but with clear guidelines.
  • AP - If the observer has too much freedom, then they may not observe some of the targets we are following.

What ever scheme we decide on the TAT will review the decisions and choices of observers (especially with regard to ToOs) a posteriori. The TAT can then try and compensate people who did not get observations of their target.

SJS - AP and TAT will come up with procedures and criteria - what we want to classify, what we want to follow and how we prioritize. These policies can then be put to the board.



How do we run the survey (scientifically)? How do we select objects? How do we do science within the consortium ? Who writes papers, and on which objects? (SJS)

Sensible to have leaders in each of the science areas (eg. PISNe, faint core-collapse...)

MD - Should we write a consortium paper, describing the survey, pipeline and database? MT - ESO messenger will probably do something on PESSTO.

CB - We should assign key projects on a merit basis CB - key project leadership could change, 5 years (the length of the PESSTO survey) is a long time

There was some discussion as to how to allocate who gets what SNe. The general consensus was that we should try and avoid internal competition between collaboration members.

MT - At a minimum there should be information as to who is working on what BS - We should keep things decided in a friendly way within the collaboration. We can have a system where people can lay claim to an SN, but then they go to the bottom of the list for future SNe. SJS - We need to decide a way of avoiding internal competition, protecting students etc. Wolfgang Hillebrandt (WH) - External people may take data from the ESO archive (as it is public) and publish quickly In response to WH's point, many people stated that we will just have to be faster. We also have a lot of resources and personnel, and the advantage of knowing when a target will be observed. SJS - Each group should write to board, state what they offer (personnel etc), and what they want to do, then the board can divide project coordination roles. Collaboration would be encouraged, but coordinated by key project leads. Rubina Kotak - favored BS scheme.


Pipeline and data-reduction

What set-up do we use? People agreed that we should try to limit the number of configurations, Gr13 (broad grism) seemed to be an acceptable option for classification (although possibly too low resolution for narrow lines?)

The PESSTO pipeline was introduced by SV. The pipeline is based on standard IRAF tasks and Python modules, and has been developed from the pipeline used by individuals within the NTT collaboration for data reduction. There was agreement that pipeline should be used, but there was some discussion as to the practicalities of where the pipeline would run, and how individuals would use it.

VNC connection from LaSilla could be slow, and make reductions frustrating. A dedicated machine could be left at NTT, with the pipeline installed for quick reductions.

Proper version control to be used for pipeline, with stable and dev branches. Should decide a version and architecture where the pipeline works. One solution could be a specified virtual machine (run locally).

MT- We should keep track of things like response curves, etc. We have the data to make our own calibration and performance plots.

What is quality control? What are the requirements of ESO in this regard? SV would like a liaison at ESO for this.

Do we want to take spectra at PA in all cases? BS - Yes, as we can subtract the galaxy if it falls in the slit.

SJS summary - pipeline to be available in three ways: supported for local install on a specified (and limited) machine setup, it will be available on laptop at NTT, and available via a VNC connection to Padova.


Overview of WISEASS system (Ofer Yaron (OY))

OY introduced the WISEASS system, and invited PESSTO members to try out the system. Data can be archived, and also analysed via a web interface.

SJS - What do we do long term? Will there be a WISEASS mirror at ESO?

BS - Can you link to external data? (eg. photometric datapoints)? OY - Yes, we can link to other data.

Can 2D spectra go into WISEASS? SV - Feels that everything should go into one PESSTO database


Final discussion

Lightcurves and photometry:

SJS - Whether it is worth taking photometry will depend on how efficient we are at finding young objects. AP - No use for 90 per cent of objects, the ones we will not follow BS - Readout time for EFOSC, if a few minutes, could be 10 per cent of time spent on each object

AP and alert group to calculate extra time which EFOSC photometry would require, and the effect on survey efficiency

Do we need extra photometry? Options Swope 1m (via La Silla Quest) Small telescope in Catalunya (NER) Faulkes REM and others? SkyMapper CHASE for followup of some SNe Liverpool Telescope To explore: 1.5 m Danish Telescope (now being run by Czechs) TAROT telescope (suggested MB)

SJS - If we have EFOSC plus another telescope, do we want the hassle of calibrating data from a lot of other sources? AP - Is REM is only support for NIR? SJS - Those who have science needs for NIR should explore other options JA - Guiliano may have access to a NIR 1.5m?


The differnet classification programs (Gelato and SNID) were discussed. Seb Bongard? (SB) - We need a couple of programs if we are targeting weird events. Stefan Taubenberger (ST) - All programs have flaws Also need experienced classifiers Most objects will be normal IIP/Ia - can ask wider collaboration for unusual SNe.

MT - Do we submit circulars? BS - Should submit asap so other people do not waste time trying to classify SNe AP - Team supporting observations can write ATEL etc with observers

Agreed that support and observing team should submit classification circulars and submit ATELs/CBET. Can ask for help around consortium if needed.

MT - ATEL or CBET? MD - CBETs are good publicity. MD - GAIA alerts will be coming by the time we are running PESSTO

Do we need a workshop to discuss the pipeline? Attach an afternoon to the next meeting for this? SJS - Encourage people to start regular telecons within groups MT - We can test PESSTO pipeline on data from next NTT run (with Benetti large programme)

SV to make a movie showing pipeline

There was also some discussion of the logistics of servicing a run, and there was particular concern from some of the smaller groups.

ST - Restriction that people come from same group makes things harder, as it's tough to get four people free at same time in one group. AP - But we know about runs in advance SJS - Can be flexible and arrange deals / swaps between groups

Next meeting to be held before March, a preliminary date of the end of January was suggested. Offers to host the meeting came from MD (Paris) and WH (Garching). A date will be decided by Doodle poll.


Minutes taken by M. Fraser