SCP Meeting Notes, 1997 October 15


Jabier and other visitors

Jabier is visiting, PhD student of Pilar is visiting. He's working for the INT group of telescopes. He's working as librarian and such; claims that he has experience with IRAF. He's here this week, hopefully to learn how to do things in our group, e.g. Tracker, dealing with our IDL. There is also thought that he might work with Isobel on the spectra, or perhaps on cleaning with Nick Wolton.

In the immediate future, there is some thought of trying to add up the n 100s INT I-band images on 9784 which individually had too low S/N to be useful, but which might be useful if the images were all added together.

Other visitors: Reynald gets here this Sunday, stays the whole following week. The Two Richards were talking about coming on the 25th or 26th, and staying for perhaps just the weekend. Pilar will be here through the end of next week.

This Friday, Patricia, the first of our Portugese students will be showing up at the airport. Jeanne is arranging an apartment, theoretically. Sebastian and Alex are planning on corrupting the new student straight off the bat.... They may even meet her at the airport.


Good-Bye Alex

Alex is leaving; we're going to have a good-bye dinner for him on Wednesday of next week.

Where?


The Great HST Ream

Saul says he's been screaming gently at HST. The deal is that they up and scheduled the NIC3 campaign during the time when our January SNe will be hot, and we can just be damned.

Current status of HST: they are so excited about their bloody NIC3 run from Jan 12-Feb 2, that there is probably no hope. The only light, however, is that they are putting in a new proposal for the HDF which may take less time, so there may be a couple of days at the beginning and end of this period in which there may be a chance that Saul can talk them into letting us do what we want. They won't talk again until the end of November.

Currently baseline plan is to observe Jan 5, the day before they start their run, 3 weeks later right after they end their run, and one time after that. This means 3-week gap observer frame, which is 10-14 day gap rest frame. If the NIC3 time doesn't get extended, perhaps we can live with it.

What Saul wants to see is some lightcurves where we sampled with a 3-week gap, and how good/bad they were.

There is also a question of getting into the queue for the Jan 5 point. Right now, we'd have to tell them immediately after our December 30 Keck night (which would require that night to be good...). There is a chance that Glen Miller (whom Saul talked to at HST) will be able to give us a day of leeway....

There is some thought to trying to move the Keck run up a night to December 29. (This is scary because it would mean that at least one observer would have to leave before our first theoretical CTIO search run on December 27.)


Status of the Nature Paper

Saul spoke to Leslie Sage at Nature. We're hosed, because we're under embargo at Nature, and here the other team got an LANL that Science magazine is now writing about. (We lose so big its a little scary.) He talked to Laura Garwin [sp?], who said she'd call Leslie. Leslie left voice mail for Saul who said that, well, if the other team has spilled, then there's no need to embargo, so Saul can talk to Science to say that we have a submitted a paper ahead of time and establish priority.

Saul wants four or five points to make. One point is that it is a tribute to our method of finding SNe on schedule that you can follow them with HST. Another point is that we have an awesome spectrum of a very high redshift supernova. Bring up that common to both papers is the question of extinction, which we mention in our paper, and that we hope to answer some of that with the upcoming HST run. Gerson says that we might mention that we've got another 38 SNe in the hopper.


More Scary K-correction Corrections

Peter: K-corrections. Calculated K-corrections we should have used vs. the ones we did use for 5 of the first 7 SNe. The difference is considering the K-correction evolution variations with stretch. ("Color effects on stretch.") For a stretch 1.1 SN at z=0.374, it gets 0.08 mag fainter at 15 days. The delta m15 then goes up, mbcorr goes down, gotta iterate... result is probably somewhere halfway between here and there. The stretch correction was 0.16 magnitudes, Peter estimates that this correction changes by half that, making the mbcorr 0.08 dimmer. [Dimmer? Nobody was consistent about this. PETER? Which way does it go?]. This brings it more inline with our more recent SNe.

the z=0.372 guy (SN5) had a delta_m15=1.39, which Peter thinks will go down to 1.26, which will change the corretion from -0.25 to -0.12, making the mbcorr dimmer. SN7 had a big difference; the delta correction probably goes from -0.47 to -0.2something. Adding in the B&H reddinign also changes the color at all of the epochs, but that is an additive 0.02. This one also gets fainter. Peter says that all but one of the five SNe got dimmer with this additional correction.

At z=0.45, there was no difference at all... Peter also didn't quite know how to swallow the stretch of 1.45. With a SN at z=0.354.... look, I'm gonna stop trying to keep up with all the details.

This effet is caused by color as a function of time for SNe of different stretches at certain redshifts. To deal with all of this, we should put the subroutine in which gives K(t,stretch,z) into SNMinuit so that the K correction is done right during the fit. (Before, all K corrections were done using the K corrections found for a stretc=1 supernova.)

Next question is the effects of this on the Hamuy set out at z=0.1, which also have to be corrected.

So it's all in flux (so to speak).

-G. Goldhaber

Peter says it is still safe to wait until the end, figure out extinction from reddeining, and put the correction in in a 1-step process. (I.e., the idea is that there is no interation necessary for extinction corrections, or so Peter believes.)

Much sadness.

Saul and Gerson tried making a histogram of Omega_M using only the SNe at z~0.46, where the K-correction effects should be minimal. First, though, Gerson showed us the histogram Omega_M (Lambda=0) for all our SNe, first as measured, then corrected. Correcting does tighten things up.

Plotting just the ones between 0.43 and 0.49, the distribution looks similar, except that they are trying to make the claim that they are knocking off the tails. (Small number statistics?) They say that they also get rid of a second, higher-Omega_M, lower number count, peak in the 'bimodal' distribution.