Status of the Galactic Plane Survey with iPTF Eric Bellm, Frank Masci, Gandalf Saxe, Sumin Tang [Tom Prince] 27 Aug 2014

Galactic plane data is new BEFORE 2013 July 2nd

Galactic plane data is new 2014 August 20th AFTER

Motivation First wide & deep variability survey of the galactic plane in optical – Other galactic plane/bulge variability surveys: Optical, New Milky Way survey and ASAS: only go to th mag; Optical, OGLE: mostly bulge NIR: VVV (FOV 1.5sd), ZYJHK, ~500 sq deg mostly bulge, final goal is to get ~100 epochs by Some small scale surveys with DECam Provide a rich set of data for a wide variety of topics: galactic structure, RCBs, massive stars/clusters, compact binaries, microlensing Potential of finding new/rare types of variables, such as stellar mergers, YSO outbursts, born again stars, BH transients, and extreme M-star flares

Photometric Surveys in the Galactic Plane Great for photometric calibration and variable classification IPHAS: |b|<5 & l=[30, 215] R (21.8mag), I, and Halpha 4853 Hα emitting stars with r < 19.5 (Corradi et al. 2008)

Oct Nov July Aug Sep Dec Yellow |b|<5, most regions with A R <6 Jan Blue: 600 sq deg A R 5 June Intended Survey Regions: |b|<5, Marked in yellow and Blue A R <4

10 kpc 20 kpc 3 kpc

2013 Pilot Galactic Plane Survey Observed 90 Galactic plane fields  45 Chandra fields in RA=17-19 & |b|<4  45 fields with l= & |b|<4 (RA=20-23) Accumulated epochs per field Mixed cadence (depends on the varying galactic share in iPTF):  Two images every other night  One image every week  High cadence experiment with 3-5 images per night for short timescale variability

2014 Galactic Plane Survey Objective  Cover IPHAS fields (b≤5) + Chandra source fields at intermediate latitudes Accumulated ~10 observations per fields in July/Aug (see following slides) Analysis of data in progress  Characterize diversity of variable sources  Refine pipelines and database  Develop real-bogus techniques for Galactic Plane region

A typical plane image Dealing with this level of source density requires careful PSF (point spread function) image differencing. (PTFIDE – Frank Masci) However, many regions, especially intermediate latitudes, work fine with conventional IPTF processing – but take longer

BEFORE After Last Summer’s Pilot Project AFTER Coverage so far (as of late Aug) Status #1 Fields observed 2x’s per night in July, 4-5 x’s per night in Aug (Scale is exposures in top plot, exposures in bottom plot)

Currently available reference fields Coverage so far (late Aug) Status #2 Reference Fields

Recent Results Summer undergraduate research project of Galdalf Saxe with Eric Bellm (Mentor) 181 million detections in fields with reference images (~20 million individual sources) – 150 sources with minimum of 10 detections and magnitude range > 2 – 100 sources with minimum of 20 detections and variability of 1-2 magnitudes This work is just beginning – analogous to early days for transient studies with PTF in 2009.

Examples of variable sources Analysis is just starting! Work of Gandalf Saxe, Summer undergraduate from Denmark Declining SN1a RR Lyrae with Blazhko Modulation (PTFS1100be) Unidentified High-cadence PTF

ZTF GALACTIC PLANE SURVEY

ZTF Plane Survey 300 visits per year (for each of 3 years) of the Plane (δ > −30◦, |b| < 7◦; Δl = 240◦). Two 7 o x7 o fields on either side of b=0 About 15% of the ZTF mission lifetime One of two public surveys to be carried out by ZTF (the other is the Northern Sky Survey)

BACKUP

Motivation (II) An unprecedented variability survey: Galactic structure with periodic variable probes: RR Lyr, Mira, Cepheids A survey of massive stars: LBVs, WRs, RSGs, and new massive clusters Exotic stellar variables: Extreme M-star flares; FU Ori; Born-Again stars (final helium flash); Stellar mergers/Red novae (M=-6 to -10), planet-star mergers; RCBs (M=-4), expected number: a few dozen; double the current sample, and true distribution of RCBs in the galaxy. X-ray binaries Others: novae, CVs, microlensing Some numbers: 10 kpc: distance modulus = 15; 20kpc: 16.5 Extinction in l=[90, 230], b=0: A R =2 to 6 R=19, D=10kpc, A R =5

The northern Galactic plane is visible at Palomar June-Jan. Thin disk=300pc, thick disk=900pc (Juric+2008). At 3kpc (Perseus & Scutum-Centaurus arms), the thin disk is |b|<6 deg Summer is needed for inner Galactic Plane (at low declination) Oct-Jan is optimal: – RA 0-7 (l= ), 130x12=1560 sq deg ~ 225 fields

Young massive star cluster Great lab for studying evolution of massive stars; only ~13 known. Cluster identification is not an easy task in crowded fields. Many contain RSGs & LBVs, and also WRs, and thus can be identified by variability. Messineo et al A new massive cluster recently found at l=29, d=6kpc; containing 8 RSGs with i= mag (González-Fernández &Negueruela 2012)

Density of compact binaries is greatest in the plane Majority of X-ray sources in the Galactic plane are unidentified compact binaries PTF variability will identify binaries via outbursts or orbital modulation and enable mass determination with RV followup BAT 58 month Chandra

Why now? PTFIDE (by Frank Masci) is capable of handling crowded fields Analysis of a test field in the Galactic center show that PTFIDE is capable of detecting most (~90%) large amp (>0.5 mag) variables Forced-PSF photometry then derives better light curves OGLE variables in a Galactic center field

NO! I couldn’t tell the true shape of the Lu Shan mountain, because I was in the mountain. -- Su Shi (Poet in Song Dynasty) One might think it’s easy to know our own milky way, and thus everything has been done?

Even for the most luminous stars in the Milky Way: we only know the tip of the iceberg Messineo 2011

Photometric Surveys in the Galactic Plane Spitzer: GLIMPSEs, 2-3 deg width over the whole galactic plane Blue: GLIMPSE360