Summary day 1

Graham – state of the survey

Full sky coverage in g, r. First DR on May 1. MSIP data.

References: complete in g and r for “grid 1”, building i. At least 15 images.

Thinking about completing also grid 2 for LIGO (avoid chip gap loss for LIGO triggers).

Alerts: approaching 100 Million. Gaps in October (coolant leak) and Dec.-Jan. (weather).

Brokers: 3(4) online (LCO, Lasair, Antares, Alerce coming soon). ZTF is LSST pathfinder, community impact is visible.

Supernovae: 1323 on Marshal, large impact on TNS, 8 TDEs, 7 CLAGN, Asteroids (AQ3)

AAS 233 January: splinter session packed. Many posters and presentations.

Publications: Focus PASP issue. Science papers: SNe, TDEs, Asteroids. Nature paper (submitted) on the 7min eclipsing binary WD, strongest LISA source, LISA calibrators. 5 more in process.

Weather is bad in winter. Long spells of bad weather.

Andrew Drake joins as DQ lead.

Report on development completeness review. Also operation cost review. Need to build contingency. There is a funding shortfall. Currently can run only till Jan. 2020. Board and PI working to address.

Riddle: review ZTF robotization. Call for suggesting new observing modes via Matthew.

Masci: review of ZTF pipelines.

Jan van Roestel: Galactic science WG summary. Overview. Data from all sky as well as deep drilling in galactic plane, both alerts and LC analysis. Projects: CVs from alerts (Szkody), expecting thousands of new CVs (so far 257 detected, 66% new). YSO eruptions (Hillenbrand) – alerts. External project from UT Austin (Vanderbosch) – eruptions from WDs using public stream. Bellm (UW) searching for new X-ray binaries. Kupfer: new type of pulsators (sdB-BLAPS) from LC analysis in the GP survey. Follow-up with RV from Keck. Radial pulsations from a compact object see with combinations of L(t), v(t) and T(t) plots. Exact nature of star is not clear, has to be compact, low mass He WDs rather than sdBs as

Initially thought. Studies of high-cadence photometry of double WDs (see above) using Chimera and KP 84inch. Need help with observing! Looking for student volunteers. Detected orbital period decay due to GW losses combining PTF and ZTF. There are other examples of eclipsing WDs.

Sjort van Velzen: review for the BH WG. Variable AGNs. CLAGN, TDEs, unusual AGN variability. Lots of follow-up including space (XMM etc). TDE: GoT naming. “no candidate left behind”. Search for nuclear flares with astrometry. Reject false positives (SN Ia, AGN). Reject SNe Ia by fade time and rate of color change (cool fast). Can select candidates efficiently. Desi will clean up the AGN background (Nugent). 8 TDEs, based mostly on MSIP. Host galaxies are red. There are also CLAGNs. Turning on AGN are outliers on the OIII vs Halpha line plot. Recoiling binary SMBHs: look for AGN-like sources offset from host galaxy center.

Uli Feindt: SN Ia cosmology WG review: missed most of this due to other commitment – apologies. Bottom line: for cosmology there are 177 SNe Ia with good LCs in g+r+I and 347 with good LCs in g+r, will improve in year 2 due to i-band templates being in place.

Steve Schulze: SN WG review. Very happy with ZTF survey. Study SNe in new ways and great quality and quantity. Infant SNe Ia: very high early LC using forced photometry (Miller group). Up to -20d before max. Young SNe II – multiple projects led by Weizmann looking at early spectroscopy and early LCs. SN2018gep – picture-book infant SN, project led by Anna Ho. Precursor identified in stacking analysis by Danny Goldstein. Fantastic. Review of AT2018cow, very unusual fast transient. Papers by Perley and Ho. Fast and red transient: work by De and Andreoni. Igor Andreoni is working also on even faster transients (min timescales) from DECAM and Catalina. Would like to apply to ZTF and look for FRB/GRB counterparts. Spectropolarimetry (Yi Yang) of infant SNe. For SN Ia – early time series of data. CC SNe – still waiting for target. 18evt – SN Ia-CSM, very strong signal. Result of one of external WG MOUs. Robotic trigger for infant SN (Nordin). On the slower timescale front: ILOT in M51, led by Jacob Jencsen (2019abn). Rich archival data set. SESN led by OKC – sample study by M.Sc student Moquist. Emir working on single object paper on 18bcc – fast rising Ibn. Double-peaked SN IIb study by Christoffer Fremling. Indications for more massive extended envelope than for, say, 2011dh. ZTF18abcfdzu – SN Ic-BL that is transforming to a IIn (interacting) – work by Leonardo Tartaglia. Superluninous Supernovae: sample studies, paper by Ragnhild Lunnan. Slow event 2018ibb work led by Steve Schulze.

Peter Nugent: ZTF and SNe Ia progenitors. Work of Abi Polin. Sub-chandra models. Recalculate models with large He shells – makes Ti and Cr at outer ejecta, inducing opacity (UV suppression). Found an object which fit models in ZTF (SN2018byg). This population of events is intrinsically redder. Rethink dust correction. Show structure in MB vs Si velocity plot (“clump” + “strip” – strip fits these sub-chandra models).

Mikael Rigault: Type Ia SN hosts work (impromptu short talk): Disentangling Ho from SN Ia cosmology. SHOEs analysis (Riess) uses Cepheids, and in contradiction (marginal) with Planck. (H=72 vs 67). “4 sigma” tension. Claim: likely systematic error. Key is host analysis – in context of progenitors – are they all the same in Elliptical/spiral galaxies (or blue/red) the same or not. With SNIFS an analysis of the local SFR environment of SNe Ia was done (Rigault 2013). New analysis (2018) shows SNe in young environments are fainter (6 sigma effect, 0.16mag). Seen in spectroscopic data from SNIFS and confirmed with photometry from SDSS and SNLS. This has impact on cosmology. Ratio of young/old is 50/50 today which means 90/10 in favor of young in past. This is the dominant error in SN Ia cosmology. What is the impact on Ho? Sure, because SNe Ia in galaxies that have Cepheids are always young since Cepheids are young stars. When correcting for this bias the Riess result moves to H=70 and the problem with Plank goes away. ZTF sample of Ia can be very important for host analysis.

-- Thomas Kupfer - 2019-03-17

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