Semester: 2004A		Partner reference: Not Available		PI time requested: 10.0 hours
Gemini reference: Not Available		Partner ranking: Not Available		PI minimum time requested: 10.0 hours
Instruments(s): GMOS North		NTAC recommended time: 0.0 nights		PI future time requested: 120.0 hours
Observing mode: queue		NTAC minimum recommended: 0.0 nights		PI total from all partners: 60.0 hours (joint proposals)
Time awarded: Not Available		Proposal submitted to: United States
		...also submitted to...United Kingdom, Canada (joint proposals)

This proposal falls under the new QR (quick response) category, for which the triggers are supernova discoveries from the CFHT Legacy Survey. The approximate trigger dates and coordinates are known months in advance. This proposal is for GMOS-N time.

Science Justification

Our goal is to distinguish between these physically-motivated models using direct geometric distance measurements of supernovae. To do this requires a concerted program to find ~1000 SNeIa at 0.2<z<1 (more than 10x the current sample), and obtain multi-colour (g'r'i'z') light curves with excellent (2-3d) sampling. (The multicolour observations improve reddening determinations; the time sampling is essential for measuring maximum light and determining the light curve "scale factor", which correlates with maximum light brightness.)

THE CFHT LEGACY SURVEY

The CFHT Legacy Survey (CFHTLS) is tailor-made for this purpose (202 nights of telescope time over 5 years, more than 500 epochs on four 1 sq deg fields, typical photometric sampling every ~2 days rest-frame, g'r'i'z' filters plus some u*, and almost real-time SN triggers - see http://www.cfht.hawaii.edu/Science/CFHTLS for more information). This unsurpassed "rolling search" strategy is possible thanks both to queue scheduling of CFHT, and to an enormous commitment of telescope time; it leads to improved efficiency for spectroscopic followup because: (1) it allows us to monitor the rise of the object and trigger spectroscopy at maximum light; (2) the flux of the target is well known since it is measured one or two days before max; this allows us an improved estimate of exposure time; (3) the detection of objects uses a lightcurve rather than a single flux difference.

The CFHTLS SN team is now routinely delivering SN detections and photometry within 24 hr of data being taken. The reader is referred to the Technical Justification for more information, to Fig. 1 for some representative light curves from engineering time in 2003A, and to http://legacy.astro.utoronto.ca/ for "up-to-the-minute" information on SN discoveries.

THIS PROPOSAL

This application is to enable the vital spectroscopic classification of the candidate SNeIa from the CFHTLS imaging survey. Spectroscopy also provides an accurate estimate of the redshift of the SNeIa. The confirmed sample of SNeIa will be used to obtain a precise measurement of the cosmological parameters (Omega_mass,Omega_Lambda) and a measurement of the equation of state of the dark energy w with a precision of better than +-0.10 (1000 SNe) when combined with other constraints on Omega_M - see Fig. 3. The goal for this semester is to obtain spectroscopy for 40 SNeIa candidates (z<~0.9) at Gemini.

This proposal is part of a well-organized international collaboration aimed at a precise measurement of cosmological parameters using the CFHTLS. The collaboration involves astronomers in Canada and France, as the lead agencies of the the CFHTLS; it also comprises groups in the USA, UK, and Europe. Spectroscopic followup time has been committed at the VLT; time is being applied for at Keck (PI Perlmutter) and Magellan (PI Carlberg, with additional observations by Magellan staff). Gemini plays a key role by allowing queue scheduled observations in the North. More details of the spectroscopic followup strategy appear below.

DISCUSSION

Supernova observations can be subjected to many straightforward tests to check for systematic effects. The CFHTLS u*g'r'i'z' data can be used to measure SN colours and hence test for reddening by comparison with colours for nearby SNe. (We have other collaborative plans to use IR data to extend colour measurements to the highest redshift objects in our sample at z~0.9.). In addition we will have a large enough sample to be able to study subsets divided by host galaxy type (derived from the host galaxy spectra or high resolution imaging), or galactocentric radius - this allows us to check for effects associated with changes in the underlying host galaxy population (metallicity, extinction, age), similar to the study of Sullivan et al (2003 MNRAS 340, 1057). The SN spectra themselves can be stacked to obtain a high S/N mean spectrum for different host galaxy types or z ranges; these can be compared against local SN spectra to check for subtle evolutionary effects.

This project is the first step in measuring w: it will assume constant w, and test the possibility that the dark energy is just the cosmological constant, i.e. the zero-point energy of the vacuum -- perhaps the simplest, best known dark energy model. Although the primary goal is to study SNeIa, some objects will turn out to be core collapse SNe. These are of interest in their own right (for measuring star formation rate as a function of z, and for studying the recently-discovered [Hamuy etal, astro-ph/0309122] relation between max brightness and envelope expansion velocity).

Attachments:

Technical Justification

We propose to use the GMOS spectrographs on Gemini N to obtain types and redshifts of supernovae with roughly 0.6<z<0.9 (given the overheads with Gemini, it is most efficient to use GMOS on these higher redshift, hence fainter objects). Based on our early results from 2003B, these SNe will have I=23-24; GMOS exposures of up to 1.5hrs will be needed, although in some cases 1hr will be sufficient. Assuming overheads of 1500s per object, we request 60hr (total from our US + UK + Canadian proposals) in order to observe approximately 40 SN candidates in 2004A. With experience, it may be possible to reduce overheads below 1500s.

All observations will use a 0.75" slit, the R400_G5305 grating, and OG515 order sorting filter. The slit PA is chosen to pass through both SN and host galaxy. Our experience shows that the dispersion of the R400 grating (~2A/pix) gives excellent sky subtraction, and we can rebin the data ~10x afterwards for redshifts and SN typing. We use Nod & Shuffle for the faintest targets - we have successfully demonstrated the use of Nod & Shuffle to confirm and classify an i'=24 candidate as a Type Ia SN at z=0.93 (see Fig 2).

Guide stars: The coordinates quoted here are the coordinates for the main search fields. The exact coordinates of targets and associated guide stars will be entered into the Phase II file when known - based on previous experience we do not expect any difficulty in finding guide stars.

SN types and redshifts from Gemini will be made public within a month of the observations being received from the Gemini Project Office.

PROGRESS SINCE THE LAST PROPOSAL

The Legacy Survey is now delivering SN detections (in the numbers expected), and photometry, on a regular basis; even though 2003A was considered as engineering pre-survey time at CFHT, there now exist 124 reliable SN detections, of which 40 have spectroscopic followup (at Keck, VLT, or Gemini). We are now obtaining 3-4 epochs in 4 filters on 2 fields in each lunation, and the number of epochs will increase to 5 or more per run as engineering time tails off. A typical CFHTLS queue run yields more than 20 high z SNe in 2 fields. See http://legacy.astro.utoronto.ca/ for the latest SN discoveries.

Our Gemini observing started 1 month ago; to date we have spectra of 7 targets from 7.8 hours of open-shutter time (12.5 hrs with overheads), giving 4 SNIa's, 1 SNII, and 2 unknowns. An example of 2 SNe and their spectra (from Gemini) are shown in Fig. 2. Nod and Shuffle is working well (7 min overhead for 30 min obs). We are testing blind offsets to cut down acquisition overheads, possibly by a few minutes per object. Given the short time between SN discovery and spectroscopic observation, it is unfortunately not yet possible to design masks for multislit observations; we are working with Gemini this semester to implement a means of designing masks directly from astrometry (without GMOS pre-imaging). When this is working (goal is 2004A), it should be possible to fabricate a multislit mask for a particular SN and its environs, and have it on the telescope within ~48 hr. This will open the remainder of the focal plane to simultaneous observations of CFHTLS-related science programs.

SCHEDULING AND LOGISTICS

SNeIa will be discovered, and reach maximum light, throughout the semester. Thus observing time should be spread through the entire semester. We will obtain SN ID's in almost real time at CFHT (~24 hr turnaround), and will constantly update our Phase 2 proposal.

Jim Rich is in charge of managing the distribution of SN ID's to the various telescopes involved in spectroscopy. In preparation for a given night, he will check the results of previous nights of spectroscopy, make a prioritized candidate list, and dispatch objects on this list to various telescopes. Gemini observations coordinator will be Isobel Hook (our contact for Phase 2 purposes).

INTERNATIONAL COLLABORATION

Spectroscopy on 8m class telescopes is essential for this project to succeed; the total amount of 8m time needed is well beyond the reach of any one group or nation. Our strategy for spectroscopic followup has progressed rapidly over the past few months, and at present is as follows:

o Gemini (this proposal) - We are applying for 60 hrs per semester (30 hrs Canada, 20hrs UK, 10 hrs US). We have a preference for GMOS-N because of the lower fringing of the GMOS-N detectors, and because much of our observing this semester is in the Groth strip (accessible only from Hawaii). Hence we are applying for 45 hr GMOS-N and 15 hr GMOS-S (all partners). The US request is for 10 hours of GMOS-N (divided between two of the total three target sky regions listed in the proposals being sent to all three TACs).

o ESO VLT - FORS1 time has been allocated over the next 2 years (60 hrs in 2003A, 60hrs in 2003B, 60 hr in 2004A). The PI is R. Pain; this group consists of UK, French and other European collaborators.

o Keck - Perlmutter et al. has applied for 4 nights of Keck time in Semester A. (The need for extra semester A time is discussed below.)

o Magellan - We will apply for 2-3 nights of Canadian time on Magellan. Carnegie scientists have also agreed to an informal arrangement in which they take spectra of z<~0.6 SNe in exchange for use of these SNe ID's for their own program of IR followup.

The following should be noted:

(1) The ratio of 10 hr US to 20 hr UK to 30 hr Canadian Gemini nights recognizes the fact that our US collaborators are contributing 4 nights of Keck time, and UK is also contributing ESO time.

(2) Gemini time plays a key role in our observations. The time is essential for observations of the Groth strip (1419+52 - not observable from Chile) in semester A; it is essential for SN coverage in May-July, when the weather is less reliable in Chile. Finally, Gemini is queue-scheduled, a fact that makes the time enormously useful for observations of transient objects, compared to block-scheduled telescopes such as Keck.

(3) The DEEP survey team (S. Faber PI) has agreed in principle to coordinating our observations with DEEP survey observations; this potentially optimizes or increases our Keck allocation. Since March 2003 R. Ellis and collaborators have been providing SN spectra and types in CFHTLS fields; in exchange we provide Ellis etal with ID's and photometry to complement their high resolution followup.

(4) Allowing for overheads, and for time lost to weather and misidentifications (e.g. AGN's, SNeII), the total time to be allocated will allow the followup of roughly 200 SNeIa per year.

Space does not allow for a complete list of the collaboration members. The Co-I's on this proposal represent the core group; see www.astro.uvic.ca/~pritchet/SN/03Bco-i.html for a complete list.

FUTURE TIME

Though the CFHTLS is a 5 year program, the first two years of the spectroscopy (~240 hr total) are critical: observations over this period will enable a first estimate of w with reasonable errors (see Fig. 3). We will also submit proposals with time requests like this one in 04B and 05A. A detailed analysis of the photometric properties of SNe may provide an alternative to spectroscopic typing in the future.

Observation Details

Resources

• Gemini North
  • GMOS-N (GMOS North)
    • Focal Plane Unit
      • Nod and Shuffle 0.75 arcsec
      • Longslit 0.75 arcsec
    • Disperser
      • R400_G5305
    • Filter
      • OG515_G0306

Observing Conditions

Name	Image Quality	Sky Background	Water Vapor	Cloud Cover
SN spec	70%	50%	Any	50%

Scheduling Information:

Synchronous dates:

Optimal dates:

Impossible dates:

Additional Information

Keywords: Cosmological distance scale, Dark matter, Survey

Publications:

• CFHTLS SN Collaboration (2003), "SUPERNOVAE 2003gy, 2003gz, 2003ha, 2003hb", IAUC 8178
• CFHTLS SN Collaboration (2003), "SUPERNOVAE 2003fr-2003gb", IAUC 8149
• CFHTLS SN Collaboration (2003), "SUPERNOVAE IAUC 81482003fl, 2003fm, 2003fn, 2003fo, 2003fp, 2003fq", IAUC 8148
• CFHTLS SN Collaboration (2003),"SUPERNOVAE 2003fe, 2003ff, 2003fg, 2003fh, 2003fi, 2003fj, 2003fk", IAUC 8147
• R.Knop, et al, (2003), New Constraints on Omega_M, Omega_Lambda, and w an Independent Set of Eleven High-Redshift Supernovae Observed with HST, ApJ, in press (astro-ph/0309368)
• Sullivan, M. et al. (2003), "Hubble Diagram of Type Ia Supernovae and Galaxy Morphology", MNRAS, 340, 1057
• Kasen, D. et al. (includes Howell) (2003), "... Flux and Polarization Spectra of the Type Ia Supernova SN 2001el ...", ApJ, 593, 788
• Garnavich et al (includes R. Carlberg) (2003), "Afterglow of GRB 011121 and Its Progenitor SN2001ke", ApJ, 582, 924
• Perlmutter, S., and Schmidt, B. (2003), "Measuring Cosmology with Supernovae". In Supernovae & Gamma Ray Bursts, astro-ph/0303428
• Wang, L., Goldhaber, G., Aldering, G., and Perlmutter, S. (2003), "Multi-Color Light Curves of Type Ia Supernovae on the Color-Magnitude Diagram: a Novel Step Torward More Precise Distance and Extinction Estimates", ApJ, 590, 944
• Stadel, Babul, et al (2003), "Amplification Bias of Supernovae from Gravitational Lensing", in prep.
• Hoekstra et al, (2002), "Constraints on Omega and sigma8 from weak lensing in RCS fields", ApJ, 577, 604
• Hoekstra et al, (2002), "Weak Lensing Study of Galaxy Biasing", ApJ, 577, 595
• Simard et al. (2002), "DEEP Groth Strip Survey. II. HST Structural Parameters of Galaxies in Groth Strip", ApJS, 142, 1
• van den Bergh et al (2002), "Classifications of the Host Galaxies of Supernovae", PASP, 114, xxx, 2002
• Hook, I. et al. (2002), "The Gemini North Multi-Object Spectrograph: Integration, Tests, and Commissioning", SPIE, 4841.
• Howell, D.A. (2001), "Progenitors of Subluminous Type Ia SNe", ApJL, 554, 193
• Stetson and Gibson (2001), "The distance to Supernova 1998aq in NGC3982", MNRAS, 328, L1-L4
• McCarthy, Carlberg, et al (2001), "Las Campanas IR Survey: Early Type Galaxies ...", ApJ, 560, L131
• Gibson, B., and Stetson, P.B. (2001), "Supernova 1991T and Ho", ApJ, 547, L103
• Howell, D. A., Hoeflich, P. Wang, L., and Wheeler, J. C. (2001), "Evidence for Asphericity in a Subluminous Type Ia Supernova: Spectropolarimetry of SN 1999by", ApJ, 556, 302
• Pain R. et al (2001) : "The Distant Type Ia SN rate" 2002, ApJ, 577, 120
• G. Goldhaber, et al, (2001), Timescale Stretch Parameterization of Type Ia Supernova B-Band Light Curves, Astrophysical Journal, 558, 359
• Gibson, Stetson, et al (2000), "... Cepheid Distances to Type IA Supernovae and the Value of Ho,'' ApJ, 529, 723
• Iwamoto et al (includes D.Balam) (2000), "Peculiar Type Ic Supernova 1997EF: Another Hypernova", ApJ 534, 660
• Stetson, P.B. (2000), "Homogeneous Photometry ... I. Photometric Standard Stars". PASP, 112, 925
• Clocchiatti et al (includes Stetson) (2000), "The Luminous Type IC Supernova 1992AR at z=0.145",ApJ, 529, 661-674
• Howell, D. A., Wang, L., Wheeler, J. C. (2000) "The Distribution of High- and Low-Redshift Type Ia Supernovae", ApJ, 530, 166
• Aldering G, Knop R., Nugent P. (2000) "The rise times of High- and Low- redshift Type Ia Supernovae are consistent", AJ, 119, 2110
• A. Goobar et al, (2000), The acceleration of the Universe: measurement of cosmological parameters from Type Ia supernovae, Physica Scripta, T85, 47.
• Perlmutter S. et al (1999) "Measurements of Omega and Lambda from 42 High-z Supernovae", ApJ, 517, 565
• Perlmutter S. et al, (1998) "Discovery of a supernova explosion at half the age of the Universe and its cosmological implications", Nature 391, 51.
• Perlmutter S. et al (1997) "Measurement of the cosmological parameters Omega and Lambda from the first 7 supernovae at z>0.35", ApJ, 483, 565
• R. Pain, I. Hook, S. Perlmutter, et al., (1996) , The Type Ia supernova rate at z~0.4, Astrophysical Journal, 473, 356

Allocations:

Reference	Time	% Useful	Comment
ESO VLT 2004A	60.0 hours		French + other European collaborators time on FORS1 (VLT) for CFHTLS SN followup; 60 hr allocated in 2003B, 60 hr 2004A, plus more time guaranteed in 2004B. The PI is R. Pain.
GN-2003B-Q-9	45.0 hours		Followup spectroscopy for CFHTLS supernovae.
GS-2003B-Q-8	15.0 hours		Followup spectroscopy for CFHTLS supernovae.
GN-2003A-Q-1	60.0 hours	100	"Gemini Deep Deep Survey" (Abraham, McCarthy, Carlberg et al)
GN-2002B-Q-30	10.3 hours	100	Joint proposal with U.S. (Knop et al) for NIRI and GMOS follow up of SNeIa. Only GMOS time was awarded by the UK TAC, and all this was used.
GN2002B-Q-36	23.0 hours	0	Simard PI - HDF N disk kinematics. No data taken due to heavy schedule of telescope shutdowns and instrument commissioning.
Gemini 02A/B	10.0 nights	95	"Gemini Deep Deep Survey" (Abraham, McCarthy, Carlberg et al) [includes ~5 nights science verification]
Magellan	12.0 nights	90	"Spectroscopy of Las Campanas Survey IR Galaxies" (McCarthy, Carlberg et al)
Gemini 02A	14.0 hours	75	"Star formation around High z QSO's" (Pritchet, Hartwick, Carlberg et al). Paper in preparation.
CFHT-02A-C14	10.0 nights	70	Stetson PI - Search for Planetary Transits in NGC6791. Data reduction in progress.
GN2002A-Q-30	12.0 hours		Hook PI. This was a joint proposal with GN2002A-Q18 (submitted to U.S. TAC) for GMOS observations of distant supernovae. Some data was acquired and a paper is in preparation.
GN2002A-Q-31	12.0 hours		Hook PI. This was a joint proposal with GN2002A-Q37 (submitted to U.S. TAC) for NIRI observations of distant supernovae. Some data obtained. Paper in preparation
GN2002A-Q-75	6.5 hours		Hook PI. This was a joint proposal with GN2002A-Q9 (submitted to Candian TAC) for GMOS spectroscopy of z>5 QSO candidates. Program completed and paper in preparation.
GN2001A-Q-10	12.0 hours	50	This was a joint proposal with GN2001A-Q-16 (submitted to the U.S. TAC) to observe distant supernovae with NIRI. Both were ranked highly and the full amount of requested time (35hrs) was awarded by the respective TACs. Because of cancellation of the queue this program was not carried out in queue mode. However it was used as a test program for NIRI SV (broadband imaging mode with the f/6 camera). About 12 hours of useful data were obtained, approximately half of our original request (when overheads are taken into account). We intend to obtain a final reference image for this SN with NIRI in semester 02B.

Proposal Contents