From: Kyle S Dawson (KDawson@lbl.gov)
Date: Wed Jun 28 2006 - 17:53:20 PDT
Hi All,
I also feel that I have not done a good job updating everyone with the
status of the SN search, so let me take this oppurtunity to do so. I'll
start with a simple laundry list of what we've found, and then summarize
our initial interpretations and some issues yet unresolved.
There are now 25 clusters in the program. Three of these were added in
Dec-Apr using free orbits from supernova-less clusters. All three of
these new clusters come from archival XMM data. Observations are
complete for 19 clusters. If I remember correctly, the search for SNe
in 5 of the remaining 6 clusters will end in late July, and the last
cluster search will end in late Aug. Those dates need to be double checked.
The full cluster list, images of SNe, etc can be found on the TWiki:
http://hstclustersn.lbl.gov:8081/twiki/bin/view/Supernovae/WebHome
usrname: TWikiGuest
passwd: hstclustersn
Current status:
Orbits used: 158 ACS, 21 NICMOS
Remaining UNscheduled orbits: 7 ACS, 9 NICMOS
***BEGIN LAUNDRY LIST*******
SNe discovered:
Active:
A-004: Awaiting spectroscopy using Subaru and VLT this week. Host is
red, possible early type, but SN is too bright to be associated with
z=1.4 cluster. SN color/mag, consistent with z~1.0-1.2.
Cluster E hosts:
O-000: z=1.01
K-000: z=1.41???Waiting better spectroscopy, hopefully tonight
H-005: z=1.23
Other cluster SNe
C-001: z=0.98, spectroscopically confirmed Ia, host faint and uncertain
SNe hosted by E type galaxies with no emission lines in background of
clusters:
O-006: z=1.31
C-000: z=1.09
G-004: z=1.35
low z field SNe (probably not useful for cosmology, maybe for rates)
N-010: z=0.203, type unknown
P-001: z=0.92, type unknown
P-009: z=0.821, Ia
X-027: z=0.4, type unknown (probably core collapse)
C-007: host uncertain, type unknown
G-003: z=0.963, type unknown
F-008: host uncertain, type unknown
H-003: z=0.851, Ia
Z-005: z=0.624, Ia
possible z>1.5 SNe (based on SNe color/mag, host color/mag):
X-018: one epoch, faint red host
X-026: two epochs, faint red host
T-001: one epoch, faint red host
undetermined redshift, discovered this week in reverse subtractions
(last epoch as ref, first epoch as search). Three have faint hosts that
appear spiral or irregular, with SNe and host consistent with z>1. We
hope to find emission lines in spectroscopic observations next spring.
E-012: faint host
F-012: faint host, SNe color, lightcurve consistent with z>1 Ia
K-018: possible cluster E, z=1.41, SN probably not useful for cosmology
due to poorly sampled lightcurve, very good for rates, spectroscopy of
host tonight, weather permitting
L-021: faint host
And finally, one mystery object:
F-006: galactic, extragalactic, z=0.54, quasar, SNIc, hypernova, pop
III SN, star??????? Nothing in the lightcurve or spectrum resembles
anything this group has seen before. The transient is hostless to a
limiting mag z'>26.5, i'>26.5. At max, the transient has z'=21.2 and
i'=21.1.
The lightcurve has a risetime of 100 days with no evolution in color.
The spectrum has features semi-consistent with a SNIc at z=0.54, but
lacks key Fe features. We posted an IAUC, or CBET as they are now
called, and have an article written about it here:
http://www.newscientistspace.com/article/dn9360-enigmatic-object-baffles-supernova-team.html
We got more data on this in poor conditions Sunday night at Keck and
last night at Subaru, there is clear continuum but the spectra are still
waiting to be reduced.
Unresolved issues: several SNe hosts have not been observed. We got
murdered with Mauna Kea weather this spring and lost almost all of our
time. We will try to pick up these redshifts in spring 2007.
*******END LAUNDRY LIST************
Now, as it stands we do have unscheduled orbits. If these orbits are
still free in Aug, we plan to return to the 5 RCS clusters in the 02-04
hr range for a second round of searching. We will have deep references
from the 2005 data for the search, and have Keck DEIMOS time scheduled
to coincide with these HST visits. We will use 5-10 orbits, depending
on how many are free. If a SN is found, we will follow the lightcurve
using the remaining unscheduled orbits. If no SN is found, we will
preserve those last orbits to use as ToO for a SN search using time
awarded to PRME et al in cycle 15 for observations of a new set of IRAC
clusters.
One thing that is very interesting to note is that we have a fairly high
rate of SNe with z>1 E hosts, but a low rate of late type hosts at this
redshift. This is very surprising and we do not have an answer for the
low rate of late type hosts. In terms of cosmology, the z>1 E hosts
should be extremely useful. The SN are often un-typed, but we plan to
obtain deep spectroscopy of the hosts in order to place constraints on
star forming and argue for Ia SNe. We believe these SNe should be
dust-free as well, but this clearly needs to be explored. These SNe are
also in the background of massive clusters, and are therefore subject to
magnification via lensing. In order to use these for cosmology, we will
need to remove this bias using estimates of cluster masses. We have two
students working on this, and I'd like them to explore different
techniques of measuring cluster mass. We may be asking for some help
with that. For the purposes of cosmology, a 2\sigma measurement of mass
through weak lensing is probably fine, but it will be very good for the
two students to learn the other methods as well.
And finally, we plan to perform a rates analysis. This is the best data
set of high z cluster SNe, and the measurement of rates in the cluster
environment should be a very good result. To do so, we will need to
come to some consensus on how to define the cluster environment. The
cluster sample is clearly inhomogeneous so this may require a bit of
work. Something to think about for this telecon Marc Postman suggests.
-Kyle
----- Original Message -----
From: Marc Postman <postman@stsci.edu>
Date: Wednesday, June 28, 2006 9:13 am
Subject: Cluster science status
> Saul, Mike, et al.,
>
> I am wondering if others feel as out of the loop as I on what's
> happening with the cluster science part of the program and who is
> doing what now. If I am not alone in this, it might be time for a
> telecon to at least get an update on progress and discussion of
> possible new ideas to pursue with the data.
>
> -Marc
>
> -----------------------------------------------------------------
> Marc Postman Email: postman@stsci.edu
> STScI - CMO Phone: +1-410-338-4340
> 3700 San Martin Drive Fax: +1-410-338-4796
> Baltimore, MD 21218 U.S.A. http://www.stsci.edu/~postman
>
>
>
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