catac report - observer), greg fahlman (nrc, observer), roberto abraham (casca president, observer),

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    CATAC Report May 17, 2017

    1 Introduction 3

    1.1 Committee Members 3

    1.2 Background 3

    1.3 Scope and Modus Operandi 4

    2 The Canadian Context of a Very Large Optical Telescope (VLOT) 5

    2.1 Scientific Capabilities 5

    2.2 Share and governance 7

    3 Site Characteristics 8

    3.1 Image Quality 9

    3.1.1 Background Information 9

    3.1.2 Turbulence Profiles 9

    3.1.3 Ground-level seeing measurements 12 MK13N and Armazones 12 ORM 12

    3.1.4 Summary 16

    3.2 Clear Sky Fraction 16

    3.3 Extinction 18

    3.4 Precipitable Water Vapour, Temperature and Pressure 18

    3.5 Adaptive Optics Performance 19

    3.5.1 Background 19

    3.5.2 Site characteristics relevant to AO operation 21

    4 Science prospects and Competitiveness 23

    4.1 Point source sensitivity in the optical and NIR 23

    4.2 Thermal Infrared 24

    4.3 Predicted scientific performance with AO: The Example of Nearby Galaxies 25

    4.3.1 Limitations of AO 28

    4.4 Latitude and Site Synergies 29

    4.5 Timelines 30

    5 Communication with Canadian community 31

    5.1 International Science Development Teams 32

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    5.2 Points of Contact 33

    5.3 Information links 33

    6 Findings 34

    7 Recommendations 35

    8 Acknowledgements 36

    9 References 36

    10 List of Acronyms 36

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    1 Introduction

    1.1 Committee Members

    Michael Balogh (Chair, Waterloo), Sarah Gallagher (Vice-Chair, CASCA representative,

    Western), Ray Carlberg (CASCA representative, U Toronto, resigned April 19, 2017), David

    Lafrenière (CASCA representative, U Montréal), Stefi Baum (ACURA representative, U.

    Manitoba), Harvey Richer (ACURA representative, UBC), Christine Wilson (ACURA

    representative, McMaster University), Luc Simard (NRC, observer), Tim Davidge (NRC,

    Observer), Greg Fahlman (NRC, observer), Roberto Abraham (CASCA President, Observer),

    Don Brooks (ACURA Executive Director, Observer), Stan Metchev (TMT SAC, Western,

    Observer), Doug Welch (TIO Board, Observer)

    1.2 Background

    In April 2015, Canada committed funds to construct the Thirty Metre Telescope (TMT) on

    Mauna Kea (MK), Hawai’i. The $243.5M contribution included industrial contracts to build the

    enclosure and the adaptive optics system, NFIRAOS. This represented the realization of a

    long-held aspiration of the Canadian community, as expressed in the Long Range Plans of 2000

    and 2010, to be major players on the international scene of optical/infrared astronomy during

    the era of 30m-class telescopes.

    The tremendous excitement that accompanied this announcement was almost immediately

    tempered by protests in Hawai’i that led to a halt of construction and eventually a revocation of

    the construction permit. Since then the project has been delayed while we await the decision of

    the courts. The delay has been costly for the project, and with a need to move forward the TMT

    International Observatory (TIO) Board in 2016 began considering alternative sites for TMT,

    should MK no longer be possible. In advance of the October 2016 Board meeting, CASCA and

    ACURA struck a ‘Tiger Team’ to consult the community and advise on what the different site

    choices meant for Canada’s aspirations. This committee had two weeks to come up with their

    recommendation. Of the sites under consideration, the committee unanimously identified Cerro

    Honar, in Chile, as the superior site scientifically. At the Board meeting, the TIO selected ORM,

    La Palma as the alternative site. The Tiger team released a public summary of their report in

    which they identified a split in the community opinion regarding ORM, and strongly

    recommended further study to assess the degree to which this choice would satisfy Canadian


    That recommendation, together with a clear need for a better community advisory structure for

    the TMT, led to the formation of the CASCA-ACURA TMT Advisory Committee (CATAC), in

    January 2017. While CATAC has a broad mandate, at this critical time our efforts are focused

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    on evaluating the scientific capability of TMT sited on ORM, and in particular assessing how

    competitive it will be compared with the European Extremely Large Telescope (ELT) being built

    on Armazones, Chile and the Giant Magellan Telescope (GMT) being built at Las Campanas,

    Chile. A TIO Board decision on whether or not to move to ORM is expected sometime before

    the construction start date of April 2018, and our purpose is to make sure the implications of this

    choice are as well understood as possible, and communicated with the Canadian community.

    1.3 Scope and Modus Operandi

    The purpose of this report is to inform the community of professional Canadian astronomers

    (CASCA members and the Long Range Planning Implementation Committee [LRPIC]) and their

    university representatives (Association of Canadian Universities for Research in Astronomy

    [ACURA]) about the current status and future prospects of the TMT project. It represents the

    synthesis of independent review by all the committee members and observers, of existing

    reports and documents, consultation with experts currently working on TMT or potential future

    TMT instruments, and feedback from the community. The objective is to provide some

    guidance based on what we know at this point, and inform the community of the committee’s

    findings and opinions given this information. The committee will remain in place and will

    continue to follow developments and incorporate new information.

    CATAC has met approximately weekly by telecon since we formed. Between meetings there

    was also much discussion via email and Slack. In addition we opened four meetings to CASCA

    members, via Webex. These included presentations by Luc Simard (Instruments Group Leader,

    TMT), Matthias Schöck (TMT site testing team) and Chris Packham (PI for the MICHI

    instrument). Valuable unsolicited contributions from members of the community have also been

    received and discussed at length by the committee.

    The body of this report presents a summary of what we have learned about the expected

    performance of TMT at ORM, how this compares with our competitors, and how it compares

    with the expectations and needs of the Canadian community. From these facts and data we

    then present some preliminary findings and recommendations. These are restricted to

    describing how competitive TMT will be relative to other planned 30-m class telescopes, how to

    make the most of the opportunities TMT presents, and how to maximize the benefit to Canada.

    We focus on the long-term competitiveness that results from the telescope design and site

    selection. This report does not attempt to address the question of Canada’s future in the

    partnership or how involvement in TMT compares with other possible futures for Canadian

    astronomy. These broader questions are more appropriately discussed within LRPIC, and we

    hope this report is informative to those discussions.

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    2 The Canadian Context of a Very Large Optical

    Telescope (VLOT)

    2.1 Scientific Capabilities

    Engagement and leadership in a VLOT has consistently been a top priority for the Canadian

    community, as expressed in the Long Range Planning process, for more than 15 years. The

    main reason for this is the scientific capability such a facility would bring, allowing Canadians to

    remain at the forefront of astronomical discovery. An aperture of 30m provides an increase of a

    factor 10 in light collecting power and a factor of 3 in spatial resolution over the largest

    telescopes available today. For adaptive-optics imaging of point sources the two effects

    combine for an increase in sensitivity that scales as D4, or a factor ~100 relative to 10-m class

    telescopes. This enables new fields of research and promises transformative changes to our

    understanding of a wide range of astrophysics. The science capabilities of TMT are well

    described in the detailed science case (Skidmore et al. 2015); ELT and GMT also have detailed

    science cases available1. Some examples of core science goals include:

    ● New tests of General Relativity and cosmology

    ● Discovery and characterization of the first galaxies

    ● Proper motion measurements around supermassive black holes in nearby galaxies

    ● Discovery and mapping of the oldest stars in the Milky Way

    ● Direct detection and characterization of exoplanets

    ● Characterization of exoplanet atmospheres and a search for biomarkers

    ● Detection and spectral characterization of Kuiper Belt objects

    Canadians have interest and expertise in these and many other topics for which 30-m

    telescopes will have an enormous impact. It is worth pointing out that science cases flow down

    to technical capabilities; different aspects of VLOT technology will impact these cases

    differently. For our purposes it is useful to consider the following broad capabilities: