1. Natalie RoeSNAP/SCP Journal Club “Identification of Type Ia Supernovae at Redshift 1.3 and Beyond with the Advanced Camera for Surveys on HST” Riess, Strolger, Tonry et al astro-ph/0308185

2. Natalie RoeSNAP/SCP Journal Club SN GO Piggyback Program subtraction within 6-18 hrs of GOODS repeat visit to identify candidates Keck and Magellan spectroscopy for most candidates with f850lp < 24 mag ACS (grism), NICMOS ToO follow-up if: –host galaxy photometric redshift > 1.2 –UV deficit at host redshift 43 total Sne candidates reported in IAU Circulars 15 Sne Ia identified via UV deficit

3. Natalie RoeSNAP/SCP Journal Club SNe Types Type I have no H2 Balmer lines near maximum –Ia show silicon line at 6150; white dwarf progenitor scattering of UV off iron group metals => “UV deficit” –Ib: no Si, but He 5876 (CC stripped of H) –Ic: no Si or He (CC stripped of H and He) Type II show emission and/or absorption at Balmer hydrogen energies near max –IIP plateau in intensity, magnitude varies widely –IIL decline in linear fashion, ~2.5 mag fainter than Ia –II-n have narrow features in spectrum All but Ia are core collapse of massive stars also have weak UV, but less common than II, and fainter

4. Natalie RoeSNAP/SCP Journal Club Typical Light Curves (Filippenko, AARA 1997)

5. Natalie RoeSNAP/SCP Journal Club Fig. 1: blue = SNII, green = SNII, red = SNIa Si(6150) Purity of Ia sample identified with UV deficit signature is estimated at 90% for z > 1

6. Natalie RoeSNAP/SCP Journal Club includes R=100 grism

7. Natalie RoeSNAP/SCP Journal Club f850lp f775w f660w obs = rest (1 + z) for z=1, Balmer lines have obs < 8000 angstroms

8. Natalie RoeSNAP/SCP Journal Club Fig. 3: SN Ia 2002fw (z=1.3) observed in ACS grism (red curve) and SNIa 1981B with hi-res spectroscopy CaII SiII(4120)

9. Natalie RoeSNAP/SCP Journal Club ACS Filters f850lp –used for image reference and discovery exposures –survey limit ~25.8 mag –8000 - 10000 A covers B band for z ~ 1 f775w –used for follow-up of lower redshift objects –7000 -8500 covers B band for z ~ 0.7 f606w –narrow band at 6000 A Colors are used to identify SN Ia for z > 1 –f775w-f850lp ( i - z) –f606w - f850lp (v - z)

10. Natalie RoeSNAP/SCP Journal Club Fig. 2: Colors of Ia and II vs redshift ( from SEDs of Fig 1) and observed colors of 15 confirmed Ia’s f775w - f850lp f660w - f850lp UV deficit ID spectroscopic conf

11. Natalie RoeSNAP/SCP Journal Club 0.2 < z< 1 –4 SNe spectroscopically confirmed on ground –3 SNe confirmed with ACS grism –but f606w bandpass is redward of 330 nm at z<1, so do not sample UV region and cannot use colors for Ia type identification

12. Natalie RoeSNAP/SCP Journal Club 1 < z < 1.5 5 candidates had colors and host photo-z’s consistent with Ia and inconsistent with II ACS bandpasses sample UV region 4 of 5 were spectroscopically confirmed

13. Natalie RoeSNAP/SCP Journal Club z > 1.5 2 candidates with colors and photo-z’s consistent with Ia –f775w-f850lp between 2 and 2.5 mag –absent in f606w to detection limit; f606w- f850lp > 3.2 mag

14. Natalie RoeSNAP/SCP Journal Club Conclusions of Paper UV deficit is a useful tool to discriminate SNeI from Sne II at z > 1. MC simulations indicate < 10% false ID; no details shown in this paper Can also calculate likelihood of mis-ID for each candidate; not included in this paper No colors shown for non-Ia SNe To obtain light curves (needed to constrain epoch of observations, determine extinction via color excess, and to calibrate peak magnitude) requires near-IR observations with NICMOS.