Producing Science with the Palomar Transient Factory Branimir Sesar (MPIA, formerly Caltech)
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Transcript of Producing Science with the Palomar Transient Factory Branimir Sesar (MPIA, formerly Caltech)
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Producing Science with the Palomar
Transient Factory
Branimir Sesar (MPIA, formerly Caltech)
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Producing Science with the Palomar
Transient Factory
Branimir Sesar (MPIA, formerly Caltech)
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Survey Goals & Key Projects(Law et al. 2009, Rau et al. 2009)
• Goal: to study the transient and variable sky
• Extragalactic
• Transients in nearby galaxies, CC SNe, TDE, Hα Sky Survey, search for eLIGO/EM counterparts
• Galactic
• AM CVn systems (H + He WD), CVs, RR Lyrae stars to map the Milky Way structure and dynamics
• Solar System: KBOs, small NEAs/PHAs (prospect for growth → asteroid retrieval mission)
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P48 wide-field imager →Discovery engine P200
Spec. followup
P60Photo. followup
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P48 wide-field imager →Discovery engine
P200Spec. followup
P60Photo. followup
Fast spectroscopic typing with SED Machine (R~100, PI: Nick Konidaris, Caltech)
R~100 spectra of various transients and variables→ important spectral features are still discernibleR~100 spectra of various transients and variables→ important spectral features are still discernible
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P48 Overview
• 7.26 deg2 field-of-view → will be upgraded to 47 deg2 for ZTF (2015-2016)
• 1” / pixel resolution → barely sampled at median 2” seeing → PSF photometry possible
• Robotic telescope & scheduler → automatic selection of fields → time & money saver
• g', R, and 2 Hα filters
• ~250 images / night
CFHT12k camera(well-defined cosmetics)
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PTF Image Differencing Engine (PTFIDE; Frank Masci, IPAC)
Real-time Pipeline (transients)
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Real-time Pipeline (transients)
Time from exposure to alert: 20 – 40 min
0.3% contamination, 0.7% of real transients missed
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IPAC Pipeline (variables & light curves)
• Repeatability of < 0.01 mag
• R-band 5σ limit @ 20.6 mag (aperture), 20.9 mag (PSF)
• 12,000 deg2 with >30 epochs
• 1st PTF/iPTF data release (M81, M44, M42, Cas A, Kepler) http://www.ptf.caltech.edu/page/first_data_release
• Public release of PTF, iPTF and ZTF data (w/ NSF funding)
coverage of the Galactic plane (|b| < 5 deg)
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Science
• 2,254 spectroscopically confirmed SNe
• 88 publications (5 in Nature)
• Finding dSphs with PTF SN Ia in M101 (PTF11kly; Nugent et al. 2011, Li et al. 2011)
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Hundreds of low-luminosity dSph galaxies orbiting the MW?
Low-luminositydSph
Tollerud et al. (2008)
Estimated number of observable faint MW satellites
• LSST should be able to observe ~300 low-luminosity dSphs
• About 50 low-luminosity dSphs in ~10,000 sq. deg and between 60 - 100 kpc
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Segue I (MV = -1.5, D = 23 kpc, r
h = 30 pc)
MSTO
RR LyraeBHB
Only 6 RGB stars!
Seg RGB → orangeSeg MS → blue
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“Segue I”-like dSph at 60 kpc (MV = -1.5)
dSph RGB → orangeforeground → white
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Segue I (MV = -1.5, D = 23 kpc, r
h = 30 pc)
MSTO
RR LyraeBHB
Only 6 RGB stars!
Seg RGB → orangeSeg MS → blue
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Table 4 of Boettcher, Willman et al. (2013)
Boo III 1 -2.0 (Sesar, submitted to ApJ)Boo II 1? ? (within 1.5' of Boo II @ 33 kpc)
Almost every dSph has at least one RR Lyrae star → use distant RR Lyrae stars as tracers of low-luminosity dSphs
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~180 RRab stars between 60 and 100 kpc
Orange – Sgr?
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“Segue I”-like dSph at 60 kpc
dSph is still invisible in the color-magnitude diagram
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Pick a distant RR Lyrae star
D = 60 kpc
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Select stars that may be at the distance of the RR Lyrae star
M92 isochrone at 60 kpc
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Plot angular coordinates with respect to the coordinates of the RR Lyrae star
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Convert angular to projected distances
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Repeat for a different RR Lyrae star (i.e., sightline) and add onto the same plot
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Repeat for a different RR Lyrae star (i.e., sightline) and add onto the same plot
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Overdensity of sources when fdSph
= 1.0 ...
Note: This is just for visualization
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...when fdSph
= 0.2
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… when f = 0 (i.e., just the background)
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Sensitivity of the detection method
Black pixels: parameter space where detection is possible at 3-sigma level
19
27
37
49
74
98
123
Minimum number of dSphs needed for a detection
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What is observed in SDSS
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Constraining the luminosity function of dSph galaxies
rh = 120 pc
rh = 30 pc
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PanSTARRS1
S82 light curve PS1 light curve
PS1 is deeper than PTF, and covers more area → repeat search
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RR Lyrae Stars
• Old, evolved stars (> 9 Gyr) → trace old populations of stars
• Standard candles → identify them → know their distance (with ~6% uncertainty)
• Bright (V ~ 21 at 110 kpc)
• Variable stars (P ~ 0.6 day) with distinct light curves ( ~1 mag amplitude) → easily identifiable
• Repeated observations (~30 or more) are needed
Light curve of an RR Lyrae type ab
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Death throes - An outburst from a massive star 40 days before a supernova explosion (Ofek+ 2013)
No detection @ -60 & -50 days
Outburst!
Explosion!
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Localization of an optical afterglow in 71 deg2 (Singer et al. 2013)
ZTF will cover this area with ~2 images
Optical afterglow
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GRB 130702A to iPTF13bxl Timeline
• 00:05 Fermi GMB trigger (UT July 2nd)
• 01:05 position refined by human (GBM group)
• 03:08 Sun sets at Palomar
• 04:17 PTF starts observations (10 fields, 2x60-s per field; 72 square degrees)
• 4214 "candidates": 44 were known asteroids, 1744 were coincident with stars (r<21) → 43 viable candidates
• Human inspection reduced this to 6 excellent candidates
• iPTF13bxh core of a bright galaxy, iPTF13bxr known quasar, iPTF13bxt was close to a star in SDSS
• Remaining candidates: iPTFbxl(RB2=0.86), iPTFbxk (RB2=0.83) and iPTFbxj (RB2=0.49)
• Sunrise in California
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GRB 130702A to iPTF13bxl Timeline
• 00:50 Swift observations for iPTF13bxl requested (UT July 3rd) → X-ray source detected
• 04:10 Robotic observations of these candidates at P60 → iPTFbxl showed decline relative to first P48 observation (!)
• 04:24 Spectral observations on the Palomar 200-inch → spectrum is featureless (!!)
• 08:24 Announced iPTF13bxl as afterglow (ATEL, GCN)
• 17:34 LAT localization (3.2 square degrees)
• 19:03 IPN announces annulus of width 0.9 degrees
• 23:17 Magellan observations led to z=0.145
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Small, but potentially hazardous asteroids
Adam Waszczak (grad student @ Caltech)
NEA 2014 JG55 (diameter: 10 m, closest approach: ¼ Earth-Moon distance)
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RR Lyrae stars in SDSS Stripe 82 (Sesar, Ivezić+ 2010)
“Smooth” inner halo ends at 30 kpc → only streams and dSphs beyond 30 kpc?
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Be Aware of the Contamination
• Sesar et al. (2007):
• Smaller number of epochs in SDSS Stripe 82
• Could not properly remove non-RR Lyrae stars
• ~30% contamination in our RR Lyrae sample
• Detection of false halo substructures
Psc
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