SL2S Workshop at SLAC (Jan 15-16)


Kaushala Bandara (UVic), Roger Blandford (Stanford), Rémi Cabanac (OMP), David Crampton (HIA), Raphaël Gavazzi (UCSB), Stephanie Jouvel (OAMP), Jean-Paul Kneib (OAMP), Alexie Leauthaud (OAMP), Phil Marshall (UCSB), Luc Simard (HIA), Sherry Suyu (Caltech), Karun Thanjavur (UVic), Tommaso Treu (UCSB)

Preliminary agenda

SL2S collaboration meeting
Kavli building, SLAC
January 15-16 2007

Monday 15th January

0800Breakfast2nd floor interaction area
0855Welcome (Blandford)2nd floor interaction area
0900-1045HST campaign status report (Kneib)Room 222
Lens modelling (Marshall/Suyu)
1045-1115Coffee2nd floor interaction area
1115-1300CFHLS status report (Cabanac)Room 222
New targets for HST follow-up (Cabanac/Gavazzi)Room 222
1300-1400Lunch2nd floor interaction area
1400-1545Spectro. follow-up campaign status
and Future strategy (Thanjavur/ Crampton)
Room 222
1545-1615Tea2nd floor interaction area
1615-1800Further follow-up observations, and SL2S' bearing on SNAP and LSSTRoom 222
EveningDinner at Gordon Biersch, Palo Alto(see below for directions)


Tuesday 16th January

0800Breakfast2nd floor interaction area
0900-1030 The scheduled telecom with French absentees was cancelled, we moved to Stanford Campus
Dpt. of Physics, Stanford
1100-1200Seminar by A. Leauthaud on weak lensing and COSMOSDpt. of Physics, Stanford
1200-1330LunchStanford Student union
1115-1300HST proposal (All) Room 222
1400-1545Modeling plan (Marshall)Dpt. of Physics, New building
1545-1615Tea Dpt. of Physics, New building
1615-1800Science interest and commitments (Cabanac)
End of meeting - dinner in Palo Alto for those remaining (Rangoon, Burmese Restaurant, excellent!)


- Convert Bernard's notes (analyses.txt) into a coherent plan with all work accounted for by team members
- Produce a plan, and hopefully a draft, of the HST proposal due on the 26th
- Produce a plan for the other follow-up observations in the foreseeable future
- On Monday: 1) produce agenda for the telecon (cancelled)
2) adapt Tuesday's schedule



- The names on the agenda are people leading discussions: if they have slides to show we can have them up, otherwise they can use the blackboards or lead a round-table chat. It is of course completely flexible - do swap in and out as appropriate.
- We will attempt a telecon on Tuesday morning via the polycom in room 222. I will circulate details of how to dial into this on Monday. For the Monday sessions, outsiders can call in and join in the discussion using the following number:

+1 650 926 5538

If there are slides shown during Monday, I (or better, Remi) will put them on the web, hopefully in advance so that the outsiders can follow.

- Dinner on Sunday night is not yet organised - downtown Palo Alto has a wide range of eateries though, and parking is easy and well-marked. I can recommend: Rangoon (Burmese); Osteria (Italian); Andale (fast Mexican); Thaiphoon (Thai). Here's a map of SLAC to downtown PA, and a link to a good restaurant finder:
google maps:

The Canadians will be out and about by around 8pm I think - if you'd like to join them for dinner, call David on +1 250 415 6250

- Gordon Biersch is a microbrewery in Palo Alto that serves nice (although not French) food. We'll meet there for dinner on Monday evening, Ill make a booking for 7:30pm for all of us (unless I hear otherwise).
- Due to the Martin Luther King day public holiday on Monday, the cafeteria will be closed. We'll be ordering pizza instead.

- The meeting will be held in the Fred Kavli building (building 51). This is the new building facing you as you drive through the gate. When you arrive at SLAC, say you are 1) staying at the guesthouse and 2) attending the SL2S meeting at KIPAC, in building 51, and be prepared to show the security man at th egate your photo ID (passport/driving licence) as you enter. The door facing th egate gets you into the lobby outside the auditorium: go through the red door marked "stair" to go up to the 2nd (US) floor where the interaction area will be obvious. I plan to be in there from 8am each day. There is free wireless throughout the building, and it is quite secure.
- All visitors to SLAC need to fill in the SLAC visitors form: Martha will collect these on Tuesday. You can download one from


Report on HST observations (J-P Kneib): sl2s_hst_slac_jan2007.pdf

Report on CFHTLS (R Cabanac): SL2S_cfhtls_slac.pdf

Report on Modeling (P Marshall/S Suyu): 07-01-15_lensModel.pdf

Report on Spectro follow-up and projects (Thanjavur): SLAC0107_v1.pdf

Outline of the HST Proposal - January 16, 2007

Snapshot C16

Science Justification:
Recycle the previous one C15 + new observations [Jp]

How many targets? [Remi]
3x area increase = 3x more targets

Models, Figures: all 5 HST observed in C15 so far shown with caustic lines N C15
+redshifts [jp]
1D spectra (Keck) [Remi]
evolution? maybe

Observing strategy: Same as before

Based on suggestion from Tommaso Treu, perhaps try requesting for shorter exposure times for more snapshots being taken. NB: Check the efficiency of snapshot vs expo time in previous proposals.

Plot suggestions:
plot of the redshifts of the sources as a function of the group mass? Occupational number of the groups (with mass from strong lensing)
Morphological mix:
what is the ratio of early type galaxy as a function of halo mass for the nearby galaxies (If halo mass is too large, the galaxies nearby move around too fast to be able to merge)

Science interests

Rémi stated that the purpose of this section was to give everyone the opportunity to express their interests in the science goals of SL2S, but also insisted on the fact that giving one's name in a given topic also meant a clear commitment to participate actively.
Phil added that the most important was to keep everyone in the loop and communicate between us.

1- Study of individual lenses

a - detailed modelling of each case, giving a reference list of all lense parameters (zl, zsi, type: galaxy, multipolar or fossil group/clusters) with all possible structural parameters (tbd) describing the light and DM distribution (all people, publication policy ?). Color and/or spectroscopic redshifts of galaxy (group members) in the field (Suyu et al., Marshall et al., Kneib et al., Fort et al., Thanjavur, Bandara).

b- Source Image reconstructions (Suyu et al., Marshall et al., Gavazzi et al.)

c - 2D dynamical studies of a selected sample of highly magnified and bright distant galaxies (Thanjavur, Crampton, Cabanac, Swinbank)

d- coupling the SL modeling with the K light distribution of galaxies (a la Lin et al 2004)(Soucail)

e- dynamics through spectroscopic follow-ups (Treu galaxies, Thanjavur groups, Gavazzi, Marshall, Cabanac)

f - gravitational telescope detection of faint galaxies (Crampton et al., Pello, Richard, Cabanac, Kneib)

2 - SL2S Statistical ananalysis

a - statistical analysis of structural parameters (splitting angles and sigma, M/L, ellipticity (triaxiallity), PA, occupational number, environmentals, effects, etc. etc....). (all of the above a + Simard: galaxy properties morphology colours vs lensing mass)

b- Here, I would like to look at the correlation between the stellar concentration parameter (C1/3 ~ m SMBH) and the lens velocity dispersion for various lens masses from rings to giant arc in clusters (Fort et al.)

c - strong lensing study of cut-off radius for galaxy members of groups (Kneib, Hong, Limousin, ...) and study of rings in clusters and groups at several Re from the center to put constraints on the main DM profiles and also on cutoff radius on galaxy members (Fort, Sygnet,...)

d - extention of SLACS studies for (ring) lenses at larger redshifts (Gavazzi, Marshall, Treu + SLACS group, Suyu, Cabanac,).

d - Understanding the selection function, comparison of simulated lensing events by groups and distant clusters with observations (Alard et al., Thanjavur, Oguri?, Gavazzi)

e- Group WL (whenever possible) up to Rvir (Soucail, Leauthaud, Marshall, Bradac maybe, Gavazzi, Motta et al.), tests of the universal DM profile. aperture mass detection (after staking similar lenses) to study C200 (M,z). (Soucail,..)

f - investigation of cosmological tests with rings (Gavazzi et al., Marshall , Suyu et al., Fort, Kneib)

g -statistic of arcs and comparison with predictions on large fields (cf Oguri 2006). comparison between SL2S ring density vs field. (Marshall, Gavazzi, Fort, Kneib)

3 - improvement of automated procedure in the SNAP/LSST perspective

a - arcs (Alard, Thanjavur, Cabanac)

b - rings (Gavazzi, Marshall, Simard, Cabanac), possible extension to the search of SL events by massive edge-on spirals (Fort)

c- improve efficiency of selection (visual, automated motors, etc.) (Cabanac, Fort).

4 - Observational follow-up and data reduction

a - HST (Kneib, Marshall, Cabanac, et al.)

b - VLT/GEMINI NS/Chilean telescopes/Keck Spectroscopy of SL2S arcs (Soucail, Cabanac, Thanjavur, Richard, Motta, Swinbank) and rings (Gavazzi et al., Richard, Treu)

c - Gemini/ESO/Keck IR imagery of SL2S lens fields (Fort et al., Thanjavur) will have a possibility to make a test with Hawki during its VLT 2007 commissioning time, Soucail, Cabanac can re-apply at CFHT)

d - X-Ray follow-ups (mass vs effective radius) proposals (Belsole, Soucail, Limousin, Mammon)

e - observation of rings with AO (Treu, Marshall, Bandara, Gavazzi et al.)

f - data reductions (PIs take care of the work)

g - Archive searches (Marshall et al., Simard, Cabanac)

5- lens modeling techniques: cf. Reports