producing science with the palomar transient factory branimir sesar (mpia, formerly caltech)

Producing Science with the Palomar

Transient Factory

Branimir Sesar (MPIA, formerly Caltech)

Producing Science with the Palomar

Transient Factory

Branimir Sesar (MPIA, formerly Caltech)

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)

P48 wide-field imager →Discovery engine P200

Spec. followup

P60Photo. followup

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

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)

PTF Image Differencing Engine (PTFIDE; Frank Masci, IPAC)

Real-time Pipeline (transients)

Real-time Pipeline (transients)

Time from exposure to alert: 20 – 40 min

0.3% contamination, 0.7% of real transients missed

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)

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)

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

Segue I (MV = -1.5, D = 23 kpc, r

h = 30 pc)

MSTO

RR LyraeBHB

Only 6 RGB stars!

Seg RGB → orangeSeg MS → blue

“Segue I”-like dSph at 60 kpc (MV = -1.5)

dSph RGB → orangeforeground → white

Segue I (MV = -1.5, D = 23 kpc, r

h = 30 pc)

MSTO

RR LyraeBHB

Only 6 RGB stars!

Seg RGB → orangeSeg MS → blue

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

~180 RRab stars between 60 and 100 kpc

Orange – Sgr?

“Segue I”-like dSph at 60 kpc

dSph is still invisible in the color-magnitude diagram

Pick a distant RR Lyrae star

D = 60 kpc

Select stars that may be at the distance of the RR Lyrae star

M92 isochrone at 60 kpc

Plot angular coordinates with respect to the coordinates of the RR Lyrae star

Convert angular to projected distances

Repeat for a different RR Lyrae star (i.e., sightline) and add onto the same plot

Repeat for a different RR Lyrae star (i.e., sightline) and add onto the same plot

Overdensity of sources when fdSph

= 1.0 ...

Note: This is just for visualization

...when fdSph

= 0.2

… when f = 0 (i.e., just the background)

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

What is observed in SDSS

Constraining the luminosity function of dSph galaxies

rh = 120 pc

rh = 30 pc

PanSTARRS1

S82 light curve PS1 light curve

PS1 is deeper than PTF, and covers more area → repeat search

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

Death throes - An outburst from a massive star 40 days before a supernova explosion (Ofek+ 2013)

No detection @ -60 & -50 days

Outburst!

Explosion!

Localization of an optical afterglow in 71 deg2 (Singer et al. 2013)

ZTF will cover this area with ~2 images

Optical afterglow

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

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

Small, but potentially hazardous asteroids

Adam Waszczak (grad student @ Caltech)

NEA 2014 JG55 (diameter: 10 m, closest approach: ¼ Earth-Moon distance)

RR Lyrae stars in SDSS Stripe 82 (Sesar, Ivezić+ 2010)

“Smooth” inner halo ends at 30 kpc → only streams and dSphs beyond 30 kpc?

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