The Zwicky Transient Facility (ZTF) survey generates real-time alerts for optical transients, variables, and moving objects discovered in its wide-field survey. We describe the ZTF alert stream ...distribution and processing (filtering) system. The system uses existing open-source technologies developed in industry: Kafka, a real-time streaming platform, and Avro, a binary serialization format. The technologies used in this system provide a number of advantages for the ZTF use case, including (1) built-in replication, scalability, and stream rewind for the distribution mechanism; (2) structured messages with strictly enforced schemas and dynamic typing for fast parsing; and (3) a Python-based stream processing interface that is similar to batch for a familiar and user-friendly plug-in filter system, all in a modular, primarily containerized system. The production deployment has successfully supported streaming up to 1.2 million alerts or roughly 70 GB of data per night, with each alert available to a consumer within about 10 s of alert candidate production. Data transfer rates of about 80,000 alerts/minute have been observed. In this paper, we discuss this alert distribution and processing system, the design motivations for the technology choices for the framework, performance in production, and how this system may be generally suitable for other alert stream use cases, including the upcoming Large Synoptic Survey Telescope.
A New Class of Changing-look LINERs Frederick, Sara; Gezari, Suvi; Graham, Matthew J. ...
The Astrophysical journal,
09/2019, Letnik:
883, Številka:
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We report the discovery of six active galactic nuclei (AGNs) caught "turning on" during the first nine months of the Zwicky Transient Facility (ZTF) survey. The host galaxies were classified as ...low-ionization nuclear emission-line region galaxies (LINERs) by weak narrow forbidden line emission in their archival SDSS spectra, and detected by ZTF as nuclear transients. In five of the cases, we found via follow-up spectroscopy that they had transformed into broad-line AGNs, reminiscent of the changing-look LINER iPTF16bco. In one case, ZTF18aajupnt/AT2018dyk, follow-up Hubble Space Telescope ultraviolet and ground-based optical spectra revealed the transformation into a narrow-line Seyfert 1 with strong Fe vii, x, xiv and He ii λ 4686 coronal lines. Swift monitoring observations of this source reveal bright UV emission that tracks the optical flare, accompanied by a luminous soft X-ray flare that peaks ∼60 days later. Spitzer follow-up observations also detect a luminous mid-infrared flare, implying a large covering fraction of dust. Archival light curves of the entire sample from CRTS, ATLAS, and ASAS-SN constrain the onset of the optical nuclear flaring from a prolonged quiescent state. Here we present the systematic selection and follow-up of this new class of changing-look LINERs, compare their properties to previously reported changing-look Seyfert galaxies, and conclude that they are a unique class of transients well-suited to test the uncertain physical processes associated with the LINER accretion state.
In this paper we present in situ transmission electron microscopy of synthetic polymeric nanoparticles with emphasis on capturing motion in a solvated, aqueous state. The nanoparticles studied were ...obtained from the direct polymerization of a Pt(II)-containing monomer. The resulting structures provided sufficient contrast for facile imaging in situ. We contend that this technique will quickly become essential in the characterization of analogous systems, especially where dynamics are of interest in the solvated state. We describe the preparation of the synthetic micellar nanoparticles together with their characterization and motion in liquid water with comparison to conventional electron microscopy analyses.
The detonation of a helium shell on a white dwarf (WD) has been proposed as a possible explosion triggering mechanism for SNe Ia. Here, we report ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq), a peculiar ...Type I supernova, consistent with being a helium-shell double-detonation. With a rise time of 18 days from explosion, the transient reached a peak absolute magnitude of MR −18.2 mag, exhibiting a light curve akin to sub-luminous SN 1991bg-like SNe Ia, albeit with an unusually steep increase in brightness within a week from explosion. Spectra taken near peak light exhibit prominent Si absorption features together with an unusually red color (g − r 2 mag) arising from nearly complete line blanketing of flux blueward of 5000 . This behavior is unlike any previously observed thermonuclear transient. Nebular phase spectra taken at and after 30 days from peak light reveal evidence of a thermonuclear detonation event dominated by Fe-group nucleosynthesis. We show that the peculiar properties of ZTF 18aaqeasu are consistent with the detonation of a massive ( 0.15 ) helium shell on a sub-Chandrasekhar mass ( 0.75 ) WD after including mixing of 0.2 of material in the outer ejecta. These observations provide evidence of a likely rare class of thermonuclear supernovae arising from detonations of massive helium shells.
Using selection criteria based on amplitude, time, and color, we have identified 329 objects as known or candidate cataclysmic variables (CVs) during the first year of testing and operation of the ...Zwicky Transient Facility. Of these, 90 are previously confirmed CVs, 218 are strong candidates based on the shape and color of their light curves obtained during 3-562 days of observation, and the remaining 21 are possible CVs but with too few data points to be listed as good candidates. Almost half of the strong candidates are within 10 deg of the galactic plane, in contrast to most other large surveys that have avoided crowded fields. The available Gaia parallaxes are consistent with sampling the low mass transfer CVs, as predicted by population models. Our follow-up spectra have confirmed Balmer/helium emission lines in 27 objects, with four showing high-excitation He ii emission, including candidates for an AM CVn, a polar, and an intermediate polar. Our results demonstrate that a complete survey of the Galactic plane is needed to accomplish an accurate determination of the number of CVs existing in the Milky Way.
There is significant interest in the models for production of short gamma-ray bursts (GRBs). Until now, the number of known short GRBs with multi-wavelength afterglows has been small. While the Fermi ...GRB Monitor detects many GRBs relative to the Neil Gehrels Swift Observatory, the large localization regions makes the search for counterparts difficult. With the Zwicky Transient Facility (ZTF) recently achieving first light, it is now fruitful to use its combination of depth (mAB ∼ 20.6), field of view ( 47 square degrees), and survey cadence (every ∼3 days) to perform Target of Opportunity observations. We demonstrate this capability on GRB 180523B, which was recently announced by the Fermi GRB Monitor as a short GRB. ZTF imaged 2900 square degrees of the localization region, resulting in the coverage of 61.6% of the enclosed probability over two nights to a depth of mAB ∼ 20.5. We characterized 14 previously unidentified transients, and none were found to be consistent with a short GRB counterpart. This search with the ZTF shows it is an efficient camera for searching for coarsely localized short GRB and gravitational-wave counterparts, allowing for a sensitive search with minimal interruption to its nominal cadence.
Direct polymerization of an oxaliplatin analogue was used to reproducibly generate amphiphiles in one pot, which consistently and spontaneously self-assemble into well-defined nanoparticles (NPs). ...Despite inefficient drug leakage in cell-free assays, the NPs were observed to be as cytotoxic as free oxaliplatin in cell culture experiments. We investigated this phenomenon by super-resolution fluorescence structured illumination microscopy (SIM) and nanoscale secondary ion mass spectrometry (NanoSIMS). In combination, these techniques revealed NPs are taken up via endocytic pathways before intracellular release of their cytotoxic cargo. As with other drug-carrying nanomaterials, these systems have potential as cellular delivery vehicles. However, high-resolution methods to track nanocarriers and their cargo at the micro- and nanoscale have been underutilized in general, limiting our understanding of their interactions with cells and tissues. We contend this type of combined optical and isotopic imaging strategy represents a powerful and potentially generalizable methodology for cellular tracking of nanocarriers and their cargo.
We use new deep 21 cm H i observations of the moderately inclined galaxy NGC 4559 in the HALOGAS survey to investigate the properties of extraplanar gas. We use TiRiFiC to construct simulated data ...cubes to match the H i observations. We find that a thick-disk component of scale height ∼2 kpc, characterized by a negative vertical gradient in its rotation velocity (lag) of ∼13 5 km s−1 kpc−1 is an adequate fit to extraplanar gas features. The tilted ring models also present evidence for a decrease in the magnitude of the lag outside R25, and a radial inflow of ∼10 km s−1. We extracted lagging extraplanar gas through Gaussian velocity profile fitting. From both the 3D models and extraction analyses we conclude that ∼10%-20% of the total H i mass is extraplanar. Most of the extraplanar gas is spatially coincident with regions of star formation in spiral arms, as traced by H and GALEX FUV images, so it is likely due to star formation processes driving a galactic fountain. We also find the signature of a filament of a kinematically "forbidden" H i feature, containing ∼1.4 × 106 M of H i, and discuss its potential relationship to a nearby H i hole. We discover a previously undetected dwarf galaxy in H i located ∼0 4 (∼58 kpc) from the center of NGC 4559, containing ∼4 × 105 M . This dwarf has counterpart sources in SDSS with spectra typical of H ii regions, and we conclude that it is two merging blue compact dwarf galaxies.
Abstract Aims To validate the Spanish version of the University of California Performance Skills Assessment (UPSA) in patients with severe mental disorders. Methods Naturalistic, 6 month follow-up, ...multicentre, validation study. 139 patients with schizophrenia, 57 bipolar patients and 31 controls were evaluated using the following scales: Spanish UPSA (Sp-UPSA), Clinical Global Impression, Severity (CGI-S), Global Assessment of Functioning (GAF), and Personal and Social Performance (PSP). Results Reliability: Internal consistency (Cronbach's alpha ) was 0.81 in schizophrenia and 0.58 in bipolar patients. Test–retest was 0.74 and 0.65 ( p < 0.0001) respectively. Construct validity: Pearson correlation coefficients between Sp-UPSA and PSP total scores were 0.42 ( p < 0.0001) for schizophrenia and 0.44 ( p = 0.001) for bipolar patients. For Sp-UPSA and GAF scores correlation coefficients were 0.43 and 0.52 ( p < 0.0001) respectively. Discriminant validity: The Sp-UPSA discriminated between patients and controls. In schizophrenia patients it also discriminated among different levels of illness severity according to CGI-S scores. In control versus patients with schizophrenia contrasts, the area under the curve was 0.89 and a cut-off point of 85 provided a sensitivity of 82.7% and a specificity of 77.4%. In bipolar patients, the area under the curve was 0.85 and a cut-off point of 90 provided a sensitivity of 82.5% and a specificity of 64.5%. Conclusion The Spanish UPSA is a reliable and valid instrument for assessing functional capacity in severe mentally ill patients. It seems to be appropriate for use in clinical trials and in everyday clinical practice as a means of monitoring functional outcomes.
An oxygen abundance gradient into the outer disc of M81 Patterson, Maria T; Walterbos, Rene A. M; Kennicutt, Robert C ...
Monthly notices of the Royal Astronomical Society,
20/May , Letnik:
422, Številka:
1
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The extended H i disc and tidal tails of M81 present an interesting environment to study the effects of galaxy interaction on star formation and chemical evolution of the outer disc of a large spiral ...galaxy. We present Hα imaging of the outer disc of M81 and luminosities for 40 H ii regions out to ∼3 R
25. We have also obtained MMT spectra for 21 H ii regions out to more than twice R
25. We derive strong-line oxygen abundances for all H ii regions using R
23-based and N ii/O ii-based calibrations and electron temperature abundances for seven regions spanning a galactocentric distance between 5.7 and 32 kpc. We also comment on the abundances of H ii regions near KDG 61 and the 'tidal dwarf' candidate HoIX. Our results constitute the most radially extended metallicity study for M81 to date. With this extended data set, we find an overall oxygen abundance gradient of Δ(log (O/H))/ΔR
G∼−0.013 dex kpc−1 over the entire radial range. This is significantly flatter than what has been found in previous studies, which were limited to the optical disc. From our temperature-based abundances, we find Δ(log (O/H))/ΔR
G∼−0.020 dex kpc−1 and present the possibility of a broken gradient from these data, but note the need to obtain more temperature-based abundances at intermediate galactocentric distances (∼10-20 kpc) to verify whether or not this may be the case. We discuss our main result of a rather flat gradient for M81 in the context of simulations and observations of abundance gradients in other galaxies. We find that the shallow abundance gradient of M81 is likely a result of the interaction history of this galaxy.
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