Collaboration Meeting in Paris

Saturday, 1998 May 30


A Lame Excuse

(First 1/2 hour of notes were missed as the laptop was not yet present. I scrawled some notes by hand, but I don't have them with me at the moment. If you nag me enough, I may eventually transcribe them here. --Rob.)

Some Sort of Overview of What We Do

So far, we think we have enough SNe at z=0.4-0.7 that we aren't going to focus on that with CTIO searches any more. We're talking about going to two new sorts of searches. One is to get supernovae at z>0.1, the other is to get low-redshift supernovae. The Keck distant stuff has some pilot time later this year. The idea was Keck search, Keck spectrocopy, Keck followup.

For the low redshift, there are three searches. CTIO group with the 0.9m at Kitt Peak, one on the ESO 2.2m, and then EROS. All of these will hopefully be turning out spuernovae at the same time, and followup will be coordinated between the Portugese, the Yale 1m service at CTIO, and... ? Followup spectroscopy will be at CTIO, Lick, WHT, Kitt Peak, DuPont, etc.

Finally, there is Reyanld's CFHT stuff, which will ideally be around z~0.9.

The INT mid-z Search

INT stuff (jumping back a couple of paragraphs) is INT 2.5m, using the four-shooter camera. There is a wide field project which covers many areas of science, and the supernova stuff is a part of it. (So, as such, we can't really decide when the nights are.) There is a web page (see Richard's handout). The program is approved for 21 nights between August and January, and 28 nights between January and July. There will be a review, and if that is succesful there will be a second year. Right now, the arrangement is for runs in 3 1-week periods starting in mid august and going through to mid november.

There are two fields 3x3 degrees (one at 2h, one at 10h, though Richard suspects this might change, but no more than 4 big fields), with mosaic pointings (other aspects of the program need a contiguous area). They would be done in the Sloane (Gunn) filters (g and i). 300s in g, a second epoch 2-3 weeks later in g and i, and a repeat of that 3 nights later. The calculation is that in the first year this would find ~18 supernovae at z=0.2-0.4. This could be in principle a self-contained project, but there still needs to be some strategy for follow-up. (Doing the whole thing at La Palma would be unwise in terms of weather.)

One issue is that we'd like shorter exposures and more coverage, but a 2.5m telescope with this sort of camera isn't optimum for that. Richard and Saul muttered about using bad seeing time with faster read-out binned.

It would be good to try to coordinate these fields with other equatorial nearby searches we are doing, for reasons of efficiency. (It doesn't seem reasoanble to try to coordinate this with Reynald's CFHT, since INT is shallow, and CHFT is deep.)

CFHT and Keck (etc.) High-Z Stuff

Back to the CFHT, which is searching at the end of November. There are 2 followup CFHT nights, but that's it, except for what we can squeeze out of the WIYN queue. Reynald says mostly that he needs a proof of concept. The CFHT will not be coordinated with Keck, and the best is to get what we can out of each of these sundry searches.

Back to INT, what can we get to followup the INT stuff. Well, maybe CFHT could do overkill followup if the fields match. Pilar might get some WHT spectroscopy for this run. This is an issue. There seems to be some public opinion for following mostly the brighter, 0.2-0.3 supernovae from INT, i.e. those which could be followed at the 2.5m.

How are we going to get ready for all of these runs? Even without followup, we have to show we know how to find SNe at INT, know how to find SNe at Keck, know how to find SNe at CFHT.

Who's going to be where doing what to find all of these various things? Reynald asserts that he's installed the LBL search software in France and that it's all working. So, theoretically, they ought to be able to run the CFHT search completely here in Paris.

Who will do the searching with the INT data? It sounds like that could be subtracted and run here in Paris. In Berkeley, we'd have to get things working for Keck.

Sebastien is the individual who will make sure that searching runs from CFHT and INT. If he can't do it himself, he will scream for help from others. INT searches is August/September/October, but the last one might slip to November. It'd be nice to get some separated, jogged images in August to give Sebastien something to practise with. The Berkeley group will be trying to "tune" our stuff for the Keck search.

For the observing, the INT won't be done by us... we will have to come to some arrangement for the transfer of the data. Pilar notes that Javier is going to be at La Palma half of the year.

Saul mentioned that Nick Kaiser has some subtraction software, apparently, which works on the CFHT and deals with all sorts of seeing variations.

Back to the issue of using the Keck to get references for CFHT, and one Keck night to do spectroscopy for the CFHT. It seems that if we do this, we have to sacrifice the fantasy of using the residual NICMOS time for anything. However, it might be good to try to coordinate the fields, so that Keck could be used for lightcurve references for the CHFT incidentially. The Keck region should match where the CFHT goes deep. Reynald says that the fields are already picked (22h, 0 dec, or some such). Peter wants Reynald to send him the exact coordinates, so that Peter can check them against HST.

Back to WHT. Pilar says that one can do either more imaging, or more spectra. So, it could be spectra for the brighter INT ones, or for the CFHT?, or something else.

The Massive Low-z Effort

New Topic: Low-z coordinated projects. Greg will hopefully give us a rough overall plan, and each player will then give their individual plans.

Greg says that he put some of the notes on the web at The idea is to get low redshift supernovae to get better template, especially before maximum, for our distant supernovae, and also to make sure that we understand the luminosity/stretch relationship. The idea is that we get 30 supernovae followed photometrically every day, and spectroscopically about once a week. For photometry, everything between U through I (for template applications).

First off, how do you get 30 nearby supernovae. Taking a rate of supernovae within z<0.1, you have to cover 100 square degrees of sky to get one supernova... this is a hard project to do with CCD cameras. We've tried to talk to a number of people who have these arrays -- most of which are new and therefore have uncertain performance characteristics -- to get search. Two searches will be run out of LBL, one at the ESO 2.2m, which Chris Lidman is in charge of. There is supposed to be an array, one name for which is ELVIS, which has a 1/3 square degree field of view. Then there is the INT camera, which perhaps we have some guaranteed time on, which is also about a 1/3 of a square degree. These two will be coordinated tightly out of LBL.

Looser collaborations include Phillips, Sunsetzff, etc. out of CTIO using the Mosaic camera on the 0.9m at Kitt Peak, which has a FoV about 1 square degree, and then there is the EROS. If all goes well and the rates are what we expect, we might find 40-50 supernovae.

Most of this will go on in the coming spring semester, so we will have to apply in the fall -- except for off-season things like ESO, where we've applied already.

We limit ourselves to z<0.1, since while they're hard to find, they're easier to follow. In addition to all the Ia's, we will probably also find some II's and other Type I's. There might be 60-100 supernovae which might have to be looked at spectroscopically to decide if they belong to this sample.

YALO 1m at CTIO for U-I band photometry. Combination of various 4m class telescopes, and some 2m class (NOT, DuPont), should be able to get nice et of followup spectroscopy.

There is a rough schedule ont he web which shows the time periods and telescope combinations we are talking about. Most of this is set for next semester. We've already applied for a lot of the ESO search and spectroscopic followup. The CTIO group is doing a test run at the KPNO 0.9m this fall (November/December). Rough baseline plan is reference runs in January 1999, search runs in Feb and Mar of 1999, follow through May 1999.

Reynald is asking if we are coordinating with other projects. Greg says that these proposals are being written as supernova search campaigns. The reason is that we want to be able to taylor stuff to what we need. In particular, becaues we're only going to z=0.1, we want to do fairly shallow sorts of deals. Greg asserts that although the overall campaign is huge, it's spread widely enough between people and telescopes that the request at any given scope isn't out of hand.

The hardest part is going to be the search; there will be a lot of data coming in. There will be questions of transferring the data to some location where it can be reduced. There will be the issues of getting the scopes to work efficiently. There will be an issue of coordinating followup between all of the telescopes. The coordination is going to be amazingly scary.

Greg says that it's more efficient if you don't target galaxies.

Reynald questions why z=0.1, not z=0.15. Greg says that the time goes as z^4 if you are sky limited... to go to z=0.15, you have a lot harder time getting spectroscopy. There are also issues of good host galaxy spectroscopy, host morphology. It makes the search hard, but it makes everything else a lot easier. For the 2m telescopes, it's an inefficinent way to use the telescope, but it's still good science and it's the most efficient way ultimately to get the information that we need. (Some telescopes, e.g. Mosaic at KPNO and EROS, they're already optimised for the sort of thing w want.)

Greg says that we will generate about 10GB of data an hour... there is an issue whether we will keep all of that. E.g. for discover, we chould threshold the pixels and only keep those pixels that have enough photons that we care about them... let the sky pixels fall to the ground.

Are we going to have to do the subtraction at the telescope? We're gonna back up the KPNO search this fall... it sounds like, although there is a CTIO grad student working on this, the Berkeley people are going to be doing a fair amount of working getting this done.

EROS search, Delphine and Alex. Use a 1 square degree 8 CCD camrea looking for SNe at z->0.2. 2x5min exposures, 5-10 square degree per night. They find one supernova per ~10 square degrees (together with about 100 false alarms). Everything is subtracted and searched at the telescope itself, and it's fully automated. It's all done using software written by Delphine. Searches aren't done for full nights... only for a couple of hours in the night. (That gets the 10 square degrees.)

Alex notes that there is some Danish followup spectroscopy and photometry time for the whole nearby candidate.

Saul says, talking to Jim Rich, that EROS might concentrate their effort during the period to coordinate with the rest of the searches and have followup. Perhaps a little more time, or more exposure with shorter exposure time. Greg says, as an example calculation, we're expecting from EROS, two searches in Febrary and March, using half of seven nights, 16 supernovae. This may require a sanity check to make sure that this makes sense. 8 at z<0.1 sounds like it might be at the bounds of reality. This is based on the assumption of 50 square degrees in one night... 2 minute exposures with 1 minute of readout. 3 hours per supernova.

INT low-z search: this is in addition to the stuff R. Ellis was talking about above. Greg says we were thinking two searches, 8 half-nights, would yeild about 20 supernovae. The idea of the half-nights is that it will be queue scheduled, and we can take less than prime time.

Backup plan: anything between 0.02 and 0.1 given in the IAUC's. Why not just use this? Peter says that there is probably 1/month which are pre-max. For followup, we need lots active all at once to get clasically scheduled followup time (spectra).

Another spectre has just raised it's head again. Why do we insist on getting so many z<0.1 supernovae? Are the 0.1-0.3 supernovae enough? It gets really hard to get lots of spectra of supernovae that way. Peter says that our biggest problem right now is that we don't know the relationship between color and stretch of the supernovae. He wants 1-2% UBV photometry on these, and we want at least a many as the current Hamuy set of 25, so we aim for 30.

Another efficiency issue is that it's inefficient to look for supernovae on lots of different telescopes.... The problem with trying to do it all at one telescope is that it gets really hard to find enough at once, but you need lots at once in order to be able to schedule spectroscopy folllowup time.

Now that Alex has moved the clock forward 2 hours, it's dinner time.

Alex says that he suggested concentrating the EROS search into a few months, but that the idea got nixed.

The issue Richard wants to bring up is, is it feasable that over 2 years, one facility targeted for 2-3 months, could get 30 nicely followed supernovae, rather than lots and lots of people working on many nearby searches all at once.

(We just took a coffee break.)

Greg will continue on the other searches that we might do.

CTIO people are slightly decoupled. They are doing a test run in November/December. They're doing a reference run in January and a search in February. We're expecting about ten supernovae from them. They're applying for their own followup, including CTIO 4m, and anywhere else they have connections. We're going to duplicate some of their stuff. The idea is to coordiante with them and not in fact duplicate, and we'll exchange data with them. There will be a grad student of theirs who will come to work with us... their view is that it's the project of the graduate student. (They don't want to form a lot of entangling alliances.)

The ESO search... Chris Lidman is the contact person, and has been writing the proposals. We're hoping to get 20 supernovae out of that search, but there are a lot of uncertainties as to how fast the camera can be pushed. It can readout the 8k x 8k array in 12 seconds, but it takes longer than that to get it on to a computer disk. Greg and Isobel thinks that the bandwidth might be improved. Isobel says also that it goes into some buffer, and you can start observing right away.

INT, 2 searches of 8 1/2 nights each, using grey time, hoping for about 20 SNe.

For the ESO search, Chris will do the observing... INT, Q scheduled? No, Richard says. Richard says the logical thing that it gets packed in with this survey he was talking about. He says that there's no hope of getting this search in through any way other than the guaranteed time. For both the ESO and INT search, we're talking about doing the searches in Berkeley... that might require some satellite link support, because we're talking a huge amount of data going over the internet.

Greg thinks that the chances of the CTIO people getting their time is good, as they are NOAO insiders and experts in this field. For ESO, Greg doesn't have a good read of the possibilities, but Chris apparently is more optimistic than we are.

Peter's also talking about getting shifted filters to do rest-frame (say) U-band photometry. The more fundamental issue, perhaps, is getting the same filters at every telescope.

Alex notes that our followup seems to be contingent on good weather in Chile. The CTIO people are getting YALO and other Chile time. EROS asks for Danish time. Berkeley asks for YALO and INT time. There are other places one might ask for time, such as Lick and Kitt Peak. There's also a hope of the HOU/Nearsearch 1m being online at Chew's Ridge, which we might be able to mooch off of. Greg also budgeted in 13 night of Portugese time (UBVRI) on the YALO telescope in the period February through May. Ana seems to think that this might possibly be plausible.

YALO = Yale, AURA, Lisbon and Ohio State, used to be the Yale 1m, at CTIO. It is being outfitted with the CCD camera, ultimately an infrared camera. It will be operated in a Queue mode. Hopefully, Brad Schaefer at Yale will be able to put in some Yale time.

For spectroscopy, we're thinking of asking for 4 nights. ESO 3.6m, 8 nights over 2 semesters. WHT, 4 nights. KP4m, 4 nights. Lick, 5 nights. NOT, 6 nights. (Ariel notes that this will be the first time NOT is dealing with us scheduling these sorts of things... also, since NOT is the first one scheduled, the other scopes may have to tailor to all of these.)

Peter has a question regarding manpower for all this observing. Greg thinks that there are going to be people down in Chile for quite a while. He doesn't think it's much more in terms of total number of people than we commit to the current search run. Isobel says that there's a lot more data reduction than we do nowadays.

In terms of who could do the oberving, Pilar says that Nick Wolton and her grad student Javier can do a lot of oberving (both for this and for the stuff associated with the project R. Ellis mentioned). Pilar also says that it's not too difficult to fly people in for observing. Then there are lots of other people who can oberve... perhaps it really isn't so out of hand as all that.

Proposal Writing With Random Discussion Mixed In

Proposal writing... which proposals are going to hit when? The first is the Portugese YALO one, which is already in discussion. We have to get the INT guaranteed time planned early enough so that we know how it's going before the other proposals are due. Unclear what the issues associated with this guaranteed time is-- are proposals necessary, etc. ESO will have the proposal for the second half of all of this due at the end of October. There are probably others due at the end of September...?

CFHT proposal will go in, Reynald says, to do a high-z search. We have to decide what to do with Keck, as well, since we're talking about proposals. Are we going to go nuts and try to do a z>1 search at Keck at the same time? Reynald would like the Keck nights for spectroscopy of the CFHT supernovae. Reynald is talking about trying to get the CFHT search in April or May to avoid conflicting with the low-z stuff. It sounds like VLT might be a good way to try to get spectra. Reyanld, or somebody, would probably try to get a proposal in on this.

When are the next HST proposals due? Saul thought September, Richard thought it had slipped. (Or, maybe the deadline is the same, but the cycle has slipped thanks to the NICMOS freak-out.) Richard wants to get images of all the retrospective supernova hosts, for morphology. (There is some thought of doing the HST snashot mode for this, but Richard thinks that that mode doesn't go deep enough.) Richard is thinking everything beyond z~0.4, i.e. the morphology of the objects we can't do from the ground. Peter is thinking maybe 20 are going to be ones we want to do. Richard asserts that an orbit is enough.

How about another HST proposal to follow up live supernovae? Yes. How do we differentiate it from what we've done before. Saul is talking z~1.5 supernoave found at Keck. The problem for this is, what instrument? (Greg thinks that there may be a chance that NIRSPEC on Keck could get us a photometry point on this.) Peter asserts that without JHK photometry, HST is useless for z~1.3 supernovae. Reyand says how about the z~0.9-1 supernoave from CFHT. Peter says even there you aren't going to get a color, and you're extrapolating U-band so that you are extremely sensitive to environment.... Peter says that 0.83 (maybe 0.9) is the limit of what you can do, for the sake of getting any colors and comparisons.

If the only think we can do is more 0.8 objects, is it worth piling up more observations at that redshift? The problem with HST is lack of infrared capability.

We're getting into discussions about how to operate at redshifts beyond 1, that perhaps we shouldn't be thinking we're just going to operate in the same mode. For instance, B-band photometry of z~0.3 supernovae might be necessary for comparative processes, although the magnitudes really drop and it gets really hard. How about space UV on low redshift supernoave? STIS spectra for UV spectra for low-redshift supernoave, to compare to the Keck spectra we'll get on z~1.3 spectra. Greg suggests that we can apply to the target of opportunity mode. Peter says that 1 orbit is way overkill for these sorts of things.

Richard suggests that for z>1 we should be concentrating on a ground based strategy.

Alex notes that the 0.8 supernovae we have at HST are our most distant ones -- are they malmquist biased, and are we going to have to pitched them? One thought is to get a better pool at 0.8-0.9, based on deeper searches so we know that these aren't biased. This might be worth putting in to HST saying you finished, and that we are using ground based stuff to fill in the NICMOS area. Richard thinks that we can't go into HST without a new idea, given that the other group is going to.

We're going in circles. The clear thing is that we still need to think more to figure out what we can put into HST that is "sexy" and new enough to get us time, but is useful enough to get us good science, and is practical.

This obviously calls for further brainstorming

Saul Perlmutter

There is talk of trying to do a search in HST... which Mark Phillips did, and got overwhelmed with Type II SNe. We all seem to be interested in anything that would find any number of very high-z Type Ia's.

Right-o, back to the topic at hand (which is now several paragraphs old). How many more proposals do we need to write for the fall? WHT could be done by somebody not in Berkeley. Ariel's already done one NOT proposal. ESO, which Chris Lidman seems to have in hand. For the Berkeley folks, that leaves CTIO, Lick, Kitt Peak, and DuPont (Wendy Freedman could do this latter one). There is also an issue at the WIYN telescope -- are we still going to be able to get followup of z=0.5-0.8 supernoave from CHFT? Some are doubtful that WIYN is going to want to keep doing this. So, the whole issue of followup for CFHT is still an issue.

Do we still need some calibration for many of the high redshift ones?

Re: dealing with old data, are we going to have to come up with fancy ways of calibrating HST data to ground based data?

Those are the main proposals... with some other discussion mixed in.

Re: the proposals, Greg has a template Lick proposal he gave to Chris for ESO and Ariel for NOT... if we get time basd on that approach, perhaps we can keep using it. All of this sort of thing can be found on Greg's web page at

Richard will take the lead on morphology HST proposal, and he will talk to Peter (and Greg) about this. (Patricia has been working on ground based morphology.) We also already have colors of host galaxies from the ground.

We Have a Plan!

Tomorrow morning we meet 9:30 AM.


Reynald introduces the FROGS (FRench Observing Group of Supernovae). It includes Reynald and Sebastien, as well as 3 physicists at Cern currently working on neutrino observations. There will be two more new observers as well, some of whom we met but whose names are flying by too fast for me to immortalize... and others. Bug Reynald for names.