Results from the Nearby Supernova Factory

Transcription

1 Results from the Nearby Supernova Factory R. C. Thomas for the SNfactory KITP: A/K/A (it s okay) Rollins Thomas Tom Rollins Roland Thomas

2 Collaboration LBL Yale LPNHE IPNL G. Aldering, PI C. Baltay P. Antilogus C. Buton S. Bailey N. Ellman J. Li Y. Copin S. Bongard D. Rabinowitz R. Pain E. Gangler M. Childress R. Scalzo R. Pereira G. Smadja S. Loken C. Wu P. Nugent U Chicago CRAL S. Perlmutter R. Kessler E. Pecontal R. C. Thomas G. Rigaudier B. Weaver Scientist/Faculty, Postdoc, Grad Student

3 SNfactory Science Goals Few hundred SN Ia light curves between 0.03 < z < 0.08 to reduce Dark Energy statistical uncertainty. like SNLS or ESSENCE JDEM with SNe Ia Linder 2006 SN Ia light curves and spectra in time series to study to enable the control of supernova systematic uncertainty. Analysis of the data set to improve our understanding of SN Ia physics and better calibrate them as standardized candles.

4 Motivation DETF For SN - detailed spectroscopic and photometric observations of 500 nearby supernovae to study the variety of peak explosion magnitudes and any associated observational signatures of effects of evolution, metallicity, or r e d d e n i n g, a s w e l l a s improvements in the system of photometric calibrations. Linder 2006

5 Motivation DETF For SN - detailed spectroscopic and photometric observations of 500 nearby supernovae to study the variety of peak explosion magnitudes and any associated observational signatures of effects of evolution, metallicity, or r e d d e n i n g, a s w e l l a s improvements in the system of photometric calibrations. BORING SNe Ia are also interesting physical phenomena! Linder 2006

6 Search Overview Palomar 1.2-m, QUEST-II camera (NEAT/QUEST surveys, piggybacked). Search pipeline at LBL for rapid (<24h) turnaround on large sky area. Processing/subtraction code from SCP with added infrastructure to scale up 100x or 1000x throughput. Reliance on distributed computing, distributed long term storage through NERSC facilities at LBL.

7 Sky Coverage Milky Way Followup Area Daytime NEAT Pointings Ecliptic Point+Track: sq deg/month. Drift-scan: sq deg/month.

8 Backseat Driver Search reference image new image subtraction reference image new image subtraction

9 Search Pipeline PALOMAR HPSS PDSF New Images Collected HPWREN Raw New Images Preprocessing Object Finding Astrometry Processed Images Reference Cache New/Ref Matching Less than 24 h turnaround is critical. Subtractions (50GB) images/night. Subtractions Generated, Events Scored Candidates Scanned by Humans

10 Machine Learning Classifiers Candidates live in ~20 dimensional Boosted decision trees, trained S/N > A score space. by fakes. yes no motion < B FWHM < C Hyperplane cuts yes no no retain too much FWHM < D Reject yes Reject garbage. yes no Supernova Reject Supernova ~ 1000 candidates requiring human scanning. Reduced human scanning load to 100 candidates/day. Bailey, et al (ApJ, submitted)

11 Machine Learning Classifiers Candidates live in ~20 dimensional score space. Boosted decision 10 0 trees, trained by fakes S/N > A Original Threshold Cuts Support Vector Machine Random Forest yes Boosted Tree no Hyperplane cuts retain too much garbage. False positive rate yes 10-4 Supernova yes FWHM < D motion < B no Reject FWHM < C no yes Reject Supernova no Reject ~ 1000 candidates requiring human scanning Reduced human scanning load to 100/day True positive rate (signal efficiency) Bailey, et al (ApJ, submitted)

12 Followup Overview LBL Subtractions Events (scored) IN2P3 (France) Postmortem Analysis Candidates (scanned, vetted) UH88/SNIFS Storage Resource Broker/Central SNIFS Processing 30% share of UH88 time 2-3 nights per week

13 C SNIFS Filter Wheel SuperNova Integral Field Spectrograph Spectroscopy channels Blue: nm Red: nm P B 2k x 4k 2k x 4k 2k x 4k MLA FOV 6 x6 Calibration unit arc lamps continuum lamps Photometric channel ~ 9 x 9 FOV R 2k x 4k Microlens Array (15x15) automated acquisition guiding extinction monitoring

14 SNIFS SuperNova Integral Field Spectrograph C Filter Wheel P 2k x 4k 2k x 4k B 2k x 4k R 2k x 4k Microlens Array (15x15) extinction monitoring guiding

15 nm nm Individual lenslet spectra mapped into datacubes. Quickie aperture extraction for realtime feedback.

16 Automated Spectroscopy Remote observe from anywhere via VNC. 2-3 day cadence, shifts done in France (daytime) UH observers have used SNIFS for comets, AGN and asteroids.

17 P Channel Acq Light Curves (also last chance to screen candidate) SNF s V-band acquisition images Flux (arbitrary units) (s SALT) useful cross-check or alternative calibration MJD ( )

18 SNIFS Productivity Spectroscopy vs Time 12th Sep 2006 Increase in slope at 19 May due to full night transition. 19th May st Jan 2006 LIPS incident, POP motor problem responsible for flat Total spectro portions. 1st Jan th Aug 2004 SNe Ia follow-up First 3 months of 2006 had the worst weather in decades on Mauna Kea.

19 SNIFS SN Ia Followup Historically we have supplemented our search with IAUC SNe. Total SNe followed by SNIFS 1st Sep st May st Jan 2006 Search productivity increase has reduced our time available for IAUC targets. 1st Jan 2005 SNe from others followed by SNIFS SNe from SNF followed by SNIFS

20 Screening and Followup SNIFS targets discovered by SNfactory SNIFS targets discovered by others

21 Time Series Coverage

22 Initial Phase Distribution SNe Ia discovered early receive most extensive followup 60 Number of SNe Ia ! 1 SNIFS epoch! 6 SNIFS epoch! 10 SNIFS epoch Initial phase estimated by spectral feature match age accurate to ± 2 d at max Initial Phase

23 Redshift Distribution SNfactory sample has good overlap with local Smooth Hubble Flow 30 Number of SNe Ia ! 1 SNIFS epoch! 6 SNIFS epoch! 10 SNIFS epoch Redshift estimated from spectral feature matches, accurate to ± Redshift

24 Synthetic Photometry S/N 10 4 Supernova Signal-to-Noise 10 3 S/N % 1% 3% 3% U (Mean = 198.2) B (Mean = 531.0) V (Mean = 404.7) R (Mean = ) I (Mean = 613.9) Phase (days)

25 Synthesized Light Curve

26 Since August spectra of individual supernovae. ~300 SNe with one spectrum or more. 2/3 from SNfactory search. 1/3 from other sources. TDC : Tête de cuvée Initial phase t < 0 Epochs SNe Ia Spectra Total TDC Total TDC 0.03 < z < since May

27 Current Challenges Increasing pre-maximum (t < -1 wk) purity. Rolling trigger search. Photometric screening aside from SNIFS. Increasing SNIFS throughput (12-14 per night). Not much room for operations improvements. Long-term schedule optimization SNIFS data pipeline -- primary issue is extraction. Host + Sky + Supernova -- blind source separation. Use of final reference subtraction.

28 SN 2005gj Relative F! + Const. SNIFS SNIFS Keck SNIFS Keck 11 d (Oct. 3.6) 64 d (Nov. 25.5) 71 d (Dec. 2.2) 71 d (Dec. 2.5) 133 d (Feb 2.2) Observer Frame Wavelength (Å) V-band flux (ergs/cm /s/hz) 2 2 i-band flux (ergs/cm /s/hz) x1e x1e Normal SN template 1991T-like template SN 2005gj SNIFS SN 2005gj NEAT/QUEST SN 2002ic Normal SN template 1991T-like template SN 2005gj SNIFS SN2005gj NEAT/QUEST SNIFS spectral decomposition Days since explosion Aldering, et al., 2006

29 Progenitor/Host Host is low metallicity, SN2005gj Host Model Z < 0.3 solar Starburst age is consistent with AB Magnitude Myr Starburst Red Template 3 solar mass progenitor Observed Wavelength (Å) 3 solar mass donor, loses 2 solar masses, WD already near Mch?

30 SN 2006D with SNIFS Thomas, et al. 2007

31 SN 2006D Acq LC Relative Flux s acq images provide preliminary V-band light curve stretch Lightcurve Phase

32 Comparisons

33 Synthetic Spectrum

34 How Sporadic is Carbon? Temperature/ionization? 17,000 km/s Explosion model parameters? Geometry? Small clumps of unburned material may always be present. Sparse distribution and small cross-section could account for sporadic observation. Polarization signature?

35 Arranged search/follow-up time to take the best 9 months of weather at both sites: April-December. Expect Palomar QUEST-II search to continue until at least Fall 2008 (end of Palomar+QUEST MOU). Expect UH88 SNIFS follow-up to be possible until at least Spring 2009 (UH88 demolition for PanSTARRS). Investigating additional imaging at Mt. Helmos 2.3-m. Investigating rolling trigger search at Palomar 1.2-m to reject old SNe, reduce SNIFS screening load, increase early-phase purity.

36 Want More Like This

37 2009 and Beyond? Sample size at end of 2008 ~ 200 SNe Ia. Move SNIFS to another telescope? Build a new SNIFS on another telescope? Use a different search camera? Use a different/additional search telescope? Partner with other searches coming online?

38 Conclusion The Nearby Supernova Factory has been discovering, and obtaining spectral time series of SNe Ia in the nearby smooth Hubble flow since late Writing some papers on interesting supernovae. We envision continuing operations until the end of We are investigating multiple options for continuing operations beyond that point. Look for light curves, spectra, and cosmology fits in the coming year.