# Presentation: 090484

## SDSS-II Supernova Survey

- R. Kessler
- University of Chicago
- Presented at the “EDEN in Paris” Workshop
- Dec  9,  2005

## SDSS II Institutions and Supernova Collaboration

- SDSS II Supernova Survey Institutional Members:
- American Museum of Natural History, Astrophysical Institute Potsdam, Cambridge
- University, University of Chicago, Fermi National Accelerator Laboratory,
- Japan Participation Group, Johns Hopkins University, Joint Institute for Nuclear
- Astrophysics, Stanford KIPAC, Korean Scientist Group, LAMOST
- Los Alamos National Laboratory, Max- Planck Institute for Astrophysics/Garching
- New Mexico State University, Ohio State University, Princeton University
- US Naval Observatory, University of Washington.
- SDSS Supernova Program Includes Collaborators from:
- Apache Point  Observatory, Space Telescope Science Institute, Penn State,
- Rochester Institute of Technology, South African Astronomical Observatory,
- University of Portsmouth, University of Texas, University of Goettingen,
- University of Munich

## Science

- Explore Hubble diagram in sparsely populated redshift  region (<0.1 - 0.4);      goal is 200 well-measured SN1a lightcurves in 3 years.
- Complement deeper surveys.
- Study systematics of  dL from SN1a.              (with unique low-z to mid-z sample)
- u-band templates for z>1 surveys.
- Collect spectra to study K-corrections.
- Collect SN types Ib,Ic,II (and peculiar/rare).
- Measure SN rates vs. z.

## Science

- Explore Hubble diagram in sparsely populated redshift  region (<0.1 - 0.4);      goal is 200 well-measured SN1a lightcurves in 3 years.
- Complement deeper surveys.
- Study systematics of  dL from SN1a.              (with unique low-z to mid-z sample)
- u-band templates for z>1 surveys.
- Collect spectra to study K-corrections.
- Collect SN types Ib,Ic,II (and peculiar/rare).
- Measure SN rates vs. z.

## Overview of Survey

- Alternate each night between                 82N and 82S  (300 sq deg coverage)
- Image in drift-scan mode

- 1200 (20 hr < RA < 4 hr)

- 2.50

- (Sep 1 - Nov 30,  2005, 2006, 2007)

- 30 2k x 2k CCDs,
- 0.4’’ resolution

## Overview of Survey

- Alternate each night between                 82N and 82S  (300 sq deg coverage)
- Image in drift-scan mode

- 1200 (20 hr < RA < 4 hr)

- 2.50

- (Sep 1 - Nov 30,  2005, 2006, 2007)

- just finished 1st season
- => subject of this talk

## The SDSS 2.5m Telescope

- 2.5m primary
- ugriz filters
- ~ 1 minute exposures
- Location: Apache Point Observatory  in    New Mexico (3000 m altitude)
- DA was upgraded in summer 2005                                        (includes data  disk   instead of tape)
- Substantial non-SDSS resources              (later in talk)

## Data Reduction for Survey

- Data are reduced and image-subtracted
-    at APO using ten dual-CPU servers with        8 Tb disk space.
- Subtractions in g,r,i
- Full night processed in < 20 hrs
- Results copied to FNAL for human scanning
- u,z ‘forced photometry’ done next day  on SN candidates found in scanning gri
-    (apply u-g  cut to distiguish Type I, II)

## Scan Example

- To appear on scan-
- page requires the
- difference image for
- at least two filters
- to have  sig/noise > 3
- and to be within 0.6’’ .

## Lightcurve Fits

- Each SN scan-tag gets a mult-band lightcurve fit to Ia, Ibc, II:
- crucial for selecting objects
- for spectro follow up

- z = 0.045

## Lightcurve Fits

- Each SN scan-tag gets a mult-band lightcurve fit to Ia, Ibc, II:
- crucial for selecting objects
- for spectro follow up

- z = 0.12

- z = 0.41

## Follow-up 

- Follow-up
- spectra
- from
- HET,
- Subaru,
- WHT,
- ARC 3.5m,
- MDM,
- Keck

## 2005 Data Overview (no cuts)

| Objects scanned by humans | 165,000
(~4000 / night) |
| --- | --- |
| SN tags  (candidates) | 26,000 
(12,000) |
| reasonable SN lightcurve fit | ~ 300 |
| Spectrum taken | 190 objects |
| Confirmed SN Ia | 135  (117  with 
pre-max image) |
| Confirmed SN other | 3 Ib,  3 Ic, 10 II  |

## 2005 Imaging Overview

- 1370  SN1a  images with 2.5m             => ~10 epochs per SN lightcurve.
- ~200 SNe images with non-2.5m to cover bad weather, faint epochs     (mag >22) and post-season follow-up:                           UH88, NMSU 1m, MDM  and occasional  ARC3.5, VATT, LT, WIYN

## 2005 Spectra Overview

- ~ 200 total SN spectra:                         HET, Subaru, WHT, ARC 3.5m, MDM, Keck

## First imaging epoch vs. redshift

- First imaging epoch vs. redshift

- (2005 sample)

- No cuts

## Fakes

- Fake SNe are inserted into data to track efficiency of software pipelines and human scanning.
- Needed to measure SN rates.
- Keeps scanners alert.
- Still no spectrum requested for a fake !!!

## Efficiency for Fake Supernova

**... ****at least one**
**opportunity **
**to scan from **
**software**

**... ****at least**
**one SN tag**
**from human**

**... ****obtained **
**spectrum after **
**lightcurve**
**fit/selection**
**(in progress)**

## Potential for Combining SN Programs

**SNLS residuals**

## Potential for Combining SN Programs

**SNLS residuals**

## Potential for Combining SN Programs

**SNLS residuals**

- 30-40 low z
- (1 of 3 years)

- 45 non-SNLS
- SNe at low z

## Summary

- Encouraging SN1a yield in 1st year
- Next year plans include:
-     reduce human scanning
-     increased follow-up resources
-     in-situ measure of lightcurve selection eff
-     improve cross-calibration between
-        SDSS 2.5m and other
-        telescopes/programs