Welcome to the LSST Dark Energy Science Collaboration

Bhuv Jain, Steve Kahn, Tony Tyson

Logistics for the Penn meeting

• People who can help you: Mike Reilly, Jean O’Boyle & Joseph Clampitt, Vinu Vikram, Tim Eifler, Masao Sako, Gary Bernstein

• Drinks this evening: 6pm at World Music Café

• Dinner tonight: you’re on your own. I recommend going across the river into Center City: – $$$: Continental Midtown, Parc, Alma de Cuba– $$: Fuji Mountain, Dmitri’s, Pietro’s pizza

• Tuesday morning: Coffee at 8:30, 1st talk at 8:45!

• WiFi information: on the back of your name tag

What is LSST?

• LSST is an ~8m telescope with a 3 Gigapixel camera and a ~10 square degree field of view.

• It will carry out a 10-year survey of 20,000 square degrees of the southern sky in 6 filters.

• It will image each patch of sky several hundred times in each filter. It will obtain stacked images of galaxies out to z~2-3 and time-varying phenomena such as Supernovae.

• A “Gold Sample” of 3 billion galaxies with shapes and photometric redshifts.

• It aims to carry out cosmological studies, with the nature of dark energy as a primary focus. Techniques: Weak Lensing, Large Scale Structure, Supernovae, and others.

• LSST is being built via a partnership between DOE and NSF. It has passed CD1 and other reviews; the next big milestone would be approval by the National Science Board in July.

• It aims for first light around 2019.

Planning the dark energy analysis for LSST: guiding principles

• Identify a set of systematics that could dominate the error budget for dark energy (at the statistical level that LSST will achieve). Collaborate with the LSST team.

– Two categories: 1. systematics that will need to be controlled significantly better than for Stage III surveys, 2. those that Stage III surveys have not addressed at all.

– Develop a science risk reduction plan focused on likely sources of error: LSST camera/telescope, photometric and photo-z calibration, observing strategy, astrophysical uncertainties, and analysis algorithms themselves.

• Identify simulation and computational needs (ImSim and cosmological) to include relevant physics, test measurement algorithms and develop methodology for controlling systematics.

• Stage III surveys aim to make order of magnitude advances on the techniques LSST will use. So develop a plan of work that is synergistic and relies on interactions with precursor surveys that are mutually beneficial.

Planning the dark energy analysis for LSST: what makes sense for a Task List?

In the first phase of work, we are not aiming to be comprehensive. A carefully chosen set of “interesting” tasks across the science areas will be chosen.

We hope the young cosmologists in the audience will lead the selection and implementation of the work plan!

See discussion in 3:30 session today.

Planning the dark energy analysis for LSST: challenges

• Why Dark Energy?

• Why Now?

• Why Us?

Planning the dark energy analysis for LSST: challenges in implementation

• How does DESC connect with the project, especially Data Management and Science Collaborations, leveraging ongoing systematics work?

• What kind of connections to precursor or corollary surveys are feasible?• How do we keep track of the evolving state of the field

– What does “dark energy” cover?• Connections to funding agencies?• How do we find individuals with expertise and FTEs in this era of multiple Stage

III surveys?• How should Computing, Simulation & Software efforts interface with Analysis?

What if NRO already has an 8m, wide-field telescope? Or 4?

For answers to all these and other questions: Steve Kahn and Tony Tyson!

What do we hope to achieve in this meeting?

• First, we must “establish” this collaboration, ie come up with reasonable definitions of:– What the collaboration is (clear statement of goals).– Who is part of it (initial membership and rules for adding members).– How it will function (governance model).

• Second, we must agree on the outline of a “white paper” that describes the above, and maps out a clear plan of research for the next three years.– “Near final” draft of the completed white paper will be due by mid-August.– We probably need to get initial writing assignments settled at this meeting.

• Third, we need to come to some understanding of “who will do what” (both institutionally and individually) over the next three years.– Ideally, the white paper will contain a matrix, showing institution against task.– Clearly, we want to encourage cooperation and collaboration, but we need to avoid

redundancy.– This is NOT “mind control”. We are not trying to adopt only one way of doing things.

But we need to understand how different approaches will be pursued in parallel, and how we will intercompare them and bring them together at the appropriate time.

Primary purpose of this meeting is discussion, not presentation• There will be plenty of time later to lecture to one another. Let’s use the time here

effectively to air major differences in point of view, and ensure that we leave here all on the same page as to where we are heading.

• However, let’s avoid long philosophical debates if we can. Some issues (publication policy, details of the membership policy, etc.) may not converge quickly. We can table some of these, and appoint a committee to come back later with a draft plan. We do not have to resolve all of these by the time of the white paper submission.

• This should be an “action-oriented” meeting. We will keep a running list of actions, with assignments, which we can review collectively at the end of each day.