4251. Searching for lensed supernovae behind galaxy clusters with upcoming telescopesTanja Petrushevska, published scientific conference contribution abstract Abstract: Aims. Strong lensing by massive galaxy clusters can provide magnification of the flux and even multiple images of the galaxies that lie behind them. This phenomenon allows one to observe high-redshift supernovae (SNe), that otherwise would remain undetected. Type Ia supernovae (SNe Ia) detections are of particular interest because of their standard brightness, since they can be used to improve either cluster lensing models or cosmological parameter measurements.
Methods. We present a ground-based, near-infrared search for lensed SNe behind the galaxy cluster Abell 370. Our survey was based on 15 epochs of J-band observations with the HAWK-I instrument on the Very Large Telescope (VLT). We use Hubble Space Telescope (HST) photometry to infer the global properties of the multiply-imaged galaxies. Using a recently published lensing model of Abell 370, we also present the predicted magnifications and the time-delays between the images.
Results. In our survey, we did not discover any live SNe from the 13 lensed galaxies with 47 multiple images behind Abell 370. This is consistent with the expectation of 0.09 ± 0.02 SNe calculated based on the measured star formation rate. We compare the expectations of discovering strongly lensed SNe in our survey and that performed with HST during the Hubble Frontier Fields (HFF) program. We also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST). We show that NIRCam instrument aboard the JWST will be sensitive to most SN multiple images in the strongly-lensed galaxies and thus able to measure their time-delays if observations are scheduled accordingly.
Keywords: JWST, WFIRST, lensed supernovae, transient search
Published in RUNG: 29.01.2018; Views: 3057; Downloads: 0
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4253. Destination: RymdenTanja Petrushevska, 2017, review, book review, critique Abstract: Destination: Rymden är en nyligen översatt bildbok av astronomi, publicerad av Rabén & Sjögren. Boken är inbunden med hårt omslag och bredare än A4-format, fylld med illustrationer och teckningar som är lämpliga för små barn. Det finns inga faktiska bilder från astronomiska objekt i boken. Det finns en tvåsidig affisch i storformat i slutet, med Pillars of Creation Nebula i ena änden och himmelkartan av norra och sydliga halvklotet på den andra.
Det finns lite text i boken. Enligt bokförlagets hemsida, riktar sig boken till läsålder 3-6, så det föreslås som den första astronomiboken för barn. Illustrationerna är ganska lämpliga för detta ändamål, men texten kanske inte är. Även om språket är ganska enkelt, använder författaren termer som knappast kan fångas av de yngsta barnen (till exempel neutronstjärna eller stora tal som 1,3 miljarder grader). Förklaringarna är emellertid koncisa med intuitiva exempel.
Bokens koncept är att lära sig genom en resa genom rymden, som börjar i början av universum, Den Stora Smällen. Läsaren är inbjuden att följ med fem ungdomar som reser genom rymdens underverk. Detta format påminner mig om Carl Sagans rymdskepp av fantasi från Cosmos-serien (Ship of the Imagination), som framgångsrikt inspirerade mig att älska astronomi när jag var ung. Boken täcker många grundläggande moderna begrepp som vi har om vårt universum, solsystem, rymdutforskning och till och med liv på andra planeter. Därför anser jag att det är ganska komplett för 38 sidor bildbok.
Författaren är en forskare i partikelfysik. Jag märkte detta från det sätt han pratar om partiklar och kärnreaktioner i solen, till exempel. Jag, som astrofysiker, skulle lägga till en del om natthimlen och konstellationerna, också för att det finns en himmelkarta med konstellationerna i slutet av boken.
Sammanfattningsvis rekommenderar jag den här boken till de föräldrar/lärare som är villiga att komplettera boken med lämpligare språk för de allra små barnen. Äldre barn (som kan läsa boken själva) skulle kanske tycka att ritningarna är lite barnsliga och kanske vill ha riktiga bilder tagna med teleskop och skulle ha en bok med mer text, fakta och förklaringar.
Keywords: review of an astronomy book for children
Published in RUNG: 26.01.2018; Views: 3185; Downloads: 0
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4254. Supernovae seen through gravitational telescopesTanja Petrushevska, invited lecture at foreign university Abstract: Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes, and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems. I will also report our discovery of the first resolved multiply-imaged gravitationally lensed supernova Type Ia.
Keywords: supernovae
Published in RUNG: 26.01.2018; Views: 2865; Downloads: 0
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4255. High redshift supernova rates measured with a gravitational telescopeTanja Petrushevska, 2015, published scientific conference contribution abstract Abstract: Supernovae (SNe) are one the most energetic phenomena in the Universe and have been extensively used for astrophysical and cosmological applications. For example, type Ia SNe as distance indicators tools have revealed the accelerating expansion of the universe, while core-collapse (CC) being directly related to the death of massive stars, they trace the star formation history. One of the challenges of SN research is the measurements of the SN rates, particularly at high-z where not many measurements exist. Possible approach to this problem is to use the magnification power of gravitational telescopes such as galaxy clusters. I will present our ground based near-infrared/optical search for gravitationally magnified supernovae behind the galaxy cluster A1689. Our search resulted in the discovery of five highly magnified candidates at high-z classified as CC SNe. We measure the first volumetric CC SN rates.
Keywords: supernova rates, gravitational telescopes, galaxy clusters
Published in RUNG: 26.01.2018; Views: 3276; Downloads: 0
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4260. High-redshift supernova rates measured with the gravitational telescope A1689Tanja Petrushevska, 2016, published scientific conference contribution abstract Abstract: Aims. We present a ground-based, near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z = 0.18, which is one of the most powerful gravitational telescopes that nature provides.
Methods. Our survey was based on multi-epoch J-band observations with the HAWK-I instrument on VLT, with supporting optical data from the Nordic Optical Telescope.
Results. Our search resulted in the discovery of five photometrically classified, core-collapse supernovae with high redshifts of
0.671 < z < 1.703 and magnifications in the range ∆m = −0.31 to −1.58 mag, as calculated from lensing models in the literature.
Owing to the power of the lensing cluster, the survey had the sensitivity to detect supernovae up to very high redshifts, z ∼ 3,
albeit for a limited region of space. We present a study of the core-collapse supernova rates for 0.4 ≤ z < 2.9, and find good
agreement with previous estimates and predictions from star formation history. During our survey, we also discovered two Type Ia
supernovae in A 1689 cluster members, which allowed us to determine the cluster Ia rate to be 0.14+0.19 ± 0.01 SNuB h2 (SNuB ≡ −0.09
10−12 SNe L−1 yr−1 ), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate ⊙,B
normalized by the stellar mass is 0.10+0.13 ± 0.02 in SNuM h2 (SNuM ≡ 10−12 SNe M−1 yr−1). Furthermore, we explore the optimal −0.06 ⊙
future survey for improving the core-collapse supernova rate measurements at z 2 using gravitational telescopes, and for detections with multiply lensed images, and we find that the planned WFIRST space mission has excellent prospects.
Conclusions. Massive clusters can be used as gravitational telescopes to significantly expand the survey range of supernova searches, with important implications for the study of the high-z transient Universe.
Keywords: supernova, gravitational telescope, galaxy clusters, Abell 1689, strong lensing
Published in RUNG: 26.01.2018; Views: 3336; Downloads: 0
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