THE E-ELT SCIENCE WORKING GROUP

MEETINGS

The Science Working Group has met on the following occasions (the agendas include links to presentations):

CONCLUSIONS & RECOMMENDATIONS

The following is a list of conclusions and recommendations distilled from the SWG's various meetings.

• The SWG notes the resignation of Marijn Franx from the SWG and thanks him for his contribution as Chair since December 2005.
• The SWG takes note of the revised terms of reference.
• The SWG notes the draft instrument selection criteria presented by the Project. Recognising that some of those criteria are outside the remit of this group, we nevertheless feel that the science criteria could be somewhat expanded. In order to help the process in particular towards selection of the first light instruments, we aim to evaluate science-based criteria based on the following:
  • high impact science in first year
  • complementarity with JWST, etc.
  • flexibility
  • specific capabilities
  • safe science
  • useability in non-optimal conditions
  We aim to develop these criteria at our next meeting with a goal of applying them after the completed instrument Phase-A studies and in time for the proposal for construction.

• The ELT-SWG is impressed that 10 instrument design studies are ongoing or starting within a month from now. This involves a big effort both from ESO and the community. The SWG was particularly impressed with the strong response on the call for open concepts. This demonstrates the strong interest of the community for the ELT.

• The ELT-SWG has taken notice of the new plan for site characterization and site selection. We are happy that the measurements will deliver homogeneous datasets starting on a short timescale. We notice that the interim reports on the characterization will be communicated to the SWG. The SWG requests the list of site characterization parameters be defined and communicated in the coming month. This will be crucial to construct functions of merit appropriate for different science cases.
• The ELT-SWG notes that good progress has been made on the instrumentation studies. The ELT-SWG expects to be involved in the prioritization of the open concept studies if a selection needs to be made. The ELT-SWG will send representatives to the instrument mid-term reviews, in order stay up-to-date, identify possible divergence from the DRM, and keep informed on the development of the science case prepared by the instrument teams.

• The SWG is impressed by the progress that ESO has made on the development of the ELT programme.
• The SWG thanks S. D'Odorico for sending draft calls for proposals to the SWG for comments, and requests that future drafts are also sent to the SWG for comments. The SWG noticed that one earlier call which had not been sent to the SWG is missing a capability.
• The SWG welcomes the call for the spectrograph (WFWBS), and stresses the importance of the optical arm. The SWG notices that there are strong science cases requiring R up to 20000 in the optical. The SWG notices that these science cases do not require that the full spectrum is covered at high resolution, in contrast to the requirement in the call.
• The SWG welcomes the call for the CODEX spectrograph, and notices that there are science cases requiring UV capability (down to 3130 Å). The SWG requests that UV capability down to 3130 Å is listed as a goal.
• The SWG will make the DRM proposals available to the instrument teams performing the studies.
• The SWG is concerned that the current instrument plan does not include a multi-object spectrograph in the visible (4000-7000 Å). The SWG notes that JWST will have no capability in this domain.
• The SWG notes that high resolution near-IR spectroscopy is complementary to JWST and is not covered in the instrument plan.
• Reccommendation: The SWG emphasizes the very strong science case for an instrument which provides multi-object spectroscopy from the r band to the H band, with a multiplex of at least 100. It is not required to give spatially resolved information. The field of view is of order 10 arcmin. The spectral resolution would be 3000, or more, subject to a trade-off. A goal would be to extend the spectral range further into the blue, and the red. Another goal would be to include R=5000-10000. The SWG would strongly encourage that an instrument like this is studied, for example as one of the studies for new instrument concepts.

• The SWG recommends that the project office studies the design of a 42-m diameter telescope. The spatial resolution is a critical parameter for 2 of the 3 primary science cases. Compared to a 30-m, the 42-m telescope will provide increased discovery space for the future and unique capabilities in many science areas, most notably exo-solar planets and stellar populations. As an example, the 42-m can observe 3 times more stars to search for exo-planets. We note that the relative speed of a 42-m telescope is 4 times higher than that of a 30-m telescope for these cases. Telescope diameter cannot be upgraded later. A choice for a 42-m diameter will give ESO the best telecope in the world.
• We recommend that ESO proceeds with the launch of the studies of the instruments proposed. We look forward to advising on the study requirements on a short timescale.
• We are pleased to see the opportunity for studies of new instrument concepts, which might include a relatively simple, near-IR multi-object spectrograph which will work in the early years of the E-ELT.

• The SWG endorses the overall phase B plan presented by the project office, and we will provide the feedback as requested by the project office. We look forward to a further update in April.
• The SWG is delighted with the DRM simulations being performed, and we look forward to further work and iterations. We request continuing ETC upgrades along with these simulations.
• The SWG recommends that a study is done for an instrument that can provide AO assisted multiplexing spectroscopy in the very early years of operation. This instrument will provide modest AO compared to the very complex instruments studied already. Such an instrument could have an upgrade path, but this is not required.
• The SWG is concerned about possible low sky coverage for certain AO modes, and recommends that a study is done to see whether such instruments can also work in simpler AO modes.
• The SWG recommends that the instrument suite can handle most observing conditions, including seeing, transparency, moon phase.
• The SWG foresees the need for a spectrograph, possibly single object / small field, which can provide intermediate resolution spectroscopy in the optical, to complement the near-IR spectrograph. We recommend a study on such an instrument.

• Recommendation 1: The Science Working Group recommends that the following 3 demonstrator science cases be used for further technical appraisal by ESO. We note, however, that they do not span the full range of capabilities required for the ELT, and we stress that they should not be used at the exclusion of other cases for downselection or optimization. The DRM being developed by the SWG is the proper tool for that purpose. The 3 demonstrator science cases will show several unique capabilities of E-ELT and will be analyzed so that their feasibility can be established.
  Demonstrator science cases:
  1. "Exoplanets": direct planet detection using an extreme AO planet finder instrument.
  2. "Physics of Galaxies": spatially resolved spectroscopy at z=3-6, out to z=10?
  3. "Stellar Populations": high resolution imaging of crowded stellar fields (λ > 800 nm).
• Recommendation 2: The SWG recommends that the following grouping of cases be used for public outreach activities:
  • exoplanets (XAO + spectroscopy + thermal), including formation of planetary systems, disks
  • galaxy formation, high-z/low-z stellar pops, including black holes in galaxies
  • frontiers of physics, fundamental constants, cosmological parameters (e.g. CODEX, supernovae), relativity and black holes

The SWG was asked by the E-ELT Science and Engineering Working Group (ESE) to answer the following questions:

1. How important is synergy with ALMA and/or VLT?
   The Science Working Group judges that the synergy with ALMA and/or VLT is extremely important. As discussed in the science document, the efficiency of many studies is hampered if E-ELT would have a latitude very different from ALMA; and many other science cases would be severely limited if no observations can be done with both ALMA and E-ELT.
2. What are the relative weights of science cases?
   See the list of prominent science cases discussed under 1). On a longer timescale, the Science Working Group will expand the prominent science cases, and build the equivalent of a "Design Reference Mission". This will require the full outlining of science observations, based on realistic instrument performance. This work is likely to start at the end of the year.
3. How do we value telescope size and timescale for building?
   The Science Working Group supports the goal expressed by council to have the E-ELT within 2 years or better of competing projects. The group notices that the performance of the available instruments at first light will have a large impact on the overall performance. The choice of "first science" instruments is therefore very important.
4. How important is the UV?
   The Science Working Group finds that the prominent science cases do not require capability below 4000 Å. Hence that should not be a driver at this stage. However, prominent science cases (CODEX, high resolution spectroscopy of high mass stars, abundances of main sequence and young stars) require spectroscopy between 4000 and 4500 Å.
5. How important is sub-mm capability?
   The Science Working Group recommends that sub-mm capability should not drive the telescope or site choice.
6. How important is thermal-IR capabillity?
   One of our prominent science cases requires capability in the Thermal IR (beyond 2.5 μm). Hence thermal-IR capability is ranked important.