131. Probing gas and dust in the tidal tail of NGC 5221 with the type Ia supernova iPTF16abcRaphael Ferretti, Rahman Amanullah, Ariel Goobar, Tanja Petrushevska, 2017, original scientific article Abstract: Context. Type Ia supernovae (SNe Ia) can be used to address numerous questions in astrophysics and cosmology. Due to their well
known spectral and photometric properties, SNe Ia are well suited to study gas and dust along the lines-of-sight to the explosions.
For example, narrow Na I D and Ca II H&K absorption lines can be studied easily, because of the well-defined spectral continuum of
SNe Ia around these features.
Aims. We aim to study the gas and dust along the line-of-sight to iPTF16abc, which occurred in an unusual location, in a tidal arm,
80 kpc from centre of the galaxy NGC 5221.
Methods. Using a time-series of high-resolution spectra, we have examined narrow Na I D and Ca II H&K absorption features for
variations in time, which would be indicative for circumstellar (CS) matter. Furthermore, we have taken advantage of the well known
photometric properties of SNe Ia to determine reddening due to dust along the line-of-sight.
Results. From the lack of variations in Na I D and Ca II H&K, we determine that none of the detected absorption features originate
from the CS medium of iPTF16abc. While the Na I D and Ca II H&K absorption is found to be optically thick, a negligible amount
of reddening points to a small column of interstellar dust.
Conclusions. We find that the gas along the line-of-sight to iPTF16abc is typical of what might be found in the interstellar medium
(ISM) within a galaxy. It suggests that we are observing gas that has been tidally stripped during an interaction of NGC 5221 with
one of its neighbouring galaxies in the past ∼109 yr. In the future, the gas clouds could become the locations of star formation. On
a longer time scale, the clouds might diffuse, enriching the circum-galactic medium (CGM) with metals. The gas profile along the
line-of-sight should be useful for future studies of the dynamics of the galaxy group containing NGC 5221. Keywords: supernovae: individual: iPTF16abc – galaxies: individual: NGC 5221 – galaxies: ISM – galaxies Published in RUNG: 23.01.2018; Views: 3075; Downloads: 0 This document has many files! More... |
132. Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at z = 1.4Tanja Petrushevska, Rahman Amanullah, Mattia Bulla, Markus Kromer, Raphael Ferretti, Ariel Goobar, Semeli Papadogiannakis, 2017, original scientific article Abstract: Context. The light from distant supernovae (SNe ) can be magnified through gravitational lensing when a foreground galaxy is
located along the line of sight. This line-up allows for detailed studies of SNe at high redshift that otherwise would not be possible.
Spectroscopic observations of lensed high-redshift Type Ia supernovae (SNe Ia) are of particular interest since they can be used
to test for evolution of their intrinsic properties. The use of SNe Ia for probing the cosmic expansion history has proven to be an
extremely powerful method for measuring cosmological parameters. However, if systematic redshift-dependent properties are found,
their usefulness for future surveys could be challenged.
Aims. We investigate whether the spectroscopic properties of the strongly lensed and very distant SN Ia PS1-10afx at z = 1.4, deviates
from the well-studied populations of normal SNe Ia at nearby or intermediate distance.
Methods. We created median spectra from nearby and intermediate-redshift spectroscopically normal SNe Ia from the literature at
−5 and +1 days from light-curve maximum. We then compared these median spectra to those of PS1-10afx.
Results. We do not find signs of spectral evolution in PS1-10afx. The observed deviation between PS1-10afx and the median templates
are within what is found for SNe at low and intermediate redshift. There is a noticeable broad feature centred at λ ∼ 3500 Å, which is
present only to a lesser extent in individual low- and intermediate-redshift SN Ia spectra. From a comparison with a recently developed
explosion model, we find this feature to be dominated by iron peak elements, in particular, singly ionized cobalt and chromium. Keywords: supernovae: individual: PS1-10afx – gravitational lensing: strong – supernovae: general Published in RUNG: 23.01.2018; Views: 3676; Downloads: 0 This document has many files! More... |
133. iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernovaAriel Goobar, Rahman Amanullah, S.R. Kulkarni, Tanja Petrushevska, 2017, original scientific article Abstract: We report the discovery of a multiply-imaged gravitationally lensed Type Ia supernova, iPTF16geu, at redshift z = 0.409. This phenomenon could be iden- tified because the light from the stellar explosion was magnified more than fifty times by the curvature of space around matter in an intervening galaxy.
We used high spatial resolution observations to resolve four images of the lensed supernova, approximately 0.300 from the center of the foreground galaxy. The observations probe a physical scale of ⇠1 kiloparsec, smaller than what is typical in other studies of extragalactic gravitational lensing. The large mag- nification and symmetric image configuration implies close alignment between the line-of-sight to the supernova and the lens. The relative magnifications of the four images provide evidence for sub-structures in the lensing galaxy. Keywords: lensed supernova, strong lensing, galaxy lens, multiply-lensed supernova Published in RUNG: 23.01.2018; Views: 3345; Downloads: 0 This document has many files! More... |
134. High-redshift supernova rates measured with the gravitational telescope A 1689Tanja Petrushevska, R. Amanullah, Ariel Goobar, S. Fabbro, Joel Johansson, Tor Kjellsson, Chris Lidman, K. Paech, Johan Richard, H. Dahle, Raphael Ferretti, J.P. Kneib, M. Limousin, Jakob Nordin, V. Stanishev, 2016, original scientific article 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 −0.09 ± 0.01 SNuB h 2 (SNuB ≡ 10−12 SNe L −1 ,B yr−1), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10+0.13 −0.06 ± 0.02 in SNuM h 2 (SNuM ≡ 10−12 SNe M−1 yr−1). Furthermore, we explore the optimal 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: supernovae: general – gravitational lensing: strong – galaxies: star formation – galaxies: clusters: individual: A 1689 –
techniques: photometric Published in RUNG: 23.01.2018; Views: 3695; Downloads: 0 This document has many files! More... |
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136. VizieR Online Data Catalog: Photometry of SN 2013gh and iPTF13dge (Ferretti+, 2016)Raphael Ferretti, Tanja Petrushevska, complete scientific database of research data Abstract: Measured photometry of type Ia supernovae 2013gh and iPTF13dge are presented. Furthermore, the effective light-curve-width-corrected phase and the natural magnitude in specified filters have been computed. Thereby, the corresponding Galactic absorption (Ax_MW) and the filter corrections (Kx) to the corresponding rest-frame filter for SN 2011fe as described by Amanullah et al. (2015MNRAS.453.3300A) are presented. The corrected magnitude can be obtained as X-AXMW-KX. All corrections have been calculated after the SN 2011fe template has been reddened with the best-fit Fitzpatrick (1999PASP..111...63F) law, for each SN. Furthermore, the V magnitude and corrections for each phase phase are included. The V magnitude was either measured (M) or calculated (D) using the SNooPy model. The V magnitude is only shown for data points used in the colour analysis, with phases between -10 and +35-days. The corrected colour can be obtained as (X-AXMW-KX)-(V-AVMW-KV) and can be compared with the corresponding colour of SN 2011fe in order to study the reddening laws of the SNe. Keywords: Supernovae, Photometry: UBV, Photometry: ugriz, Photometry: ultraviolet Published in RUNG: 23.01.2018; Views: 3708; Downloads: 0 This document has many files! More... |
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138. Time-varying sodium absorption in the Type Ia supernova 2013ghRaphael Ferretti, R. Amanullah, Ariel Goobar, Joel Johansson, Tanja Petrushevska, 2016, original scientific article Abstract: Context. Temporal variability of narrow absorption lines in high-resolution spectra of Type Ia supernovae (SNe Ia) is studied to
search for circumstellar matter. Time series which resolve the profiles of absorption lines such as Na I D or Ca II H&K are expected
to reveal variations due to photoionisation and subsequent recombination of the gases. The presence, composition, and geometry of
circumstellar matter may hint at the elusive progenitor system of SNe Ia and could also affect the observed reddening law.
Aims. To date, there are few known cases of time-varying Na I D absorption in SNe Ia, all of which occurred during relatively late
phases of the supernova (SN) evolution. Photoionisation, however, is predicted to occur during the early phases of SNe Ia, when the
supernovae peak in the ultraviolet. We attempt, therefore, to observe early-time absorption-line variations by obtaining high-resolution
spectra of SNe before maximum light.
Methods. We have obtained photometry and high-resolution spectroscopy of SNe Ia 2013gh and iPTF 13dge, to search for absorptionline
variations. Furthermore, we study interstellar absorption features in relation to the observed photometric colours of the SNe.
Results. Both SNe display deep Na I D and Ca II H&K absorption features. Furthermore, small but significant variations are detected
in a feature of the Na I D profile of SN 2013gh. The variations are consistent with either geometric effects of rapidly moving or patchy
gas clouds or photoionisation of Na I gas at R ≈ 1019 cm from the explosion.
Conclusions. Our analysis indicates that it is necessary to focus on early phases to detect photoionisation effects of gases in the
circumstellar medium of SNe Ia. Different absorbers such as Na I and Ca II can be used to probe for matter at different distances from
the SNe. The nondetection of variations during early phases makes it possible to put limits on the abundance of the species at those
distances. Keywords: supernovae: general – supernovae: individual: SN 2013gh – dust, extinction – circumstellar matter –
supernovae: individual: iPTF 13dge Published in RUNG: 23.01.2018; Views: 3539; Downloads: 0 This document has many files! More... |
139. Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 μmRahman Amanullah, Tanja Petrushevska, 2015, original scientific article Abstract: We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2–2 μm. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B − V) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction RV. In particular, we note that for the two SNe with E(B − V) ≳ 1 mag, for which the colour excess is dominated by dust extinction, we find RV = 1.4 ± 0.1 and RV = 2.8 ± 0.1. Adding UV photometry reduces the uncertainty of fitted RV by ∼50 per cent allowing us to also measure RV of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe. Keywords: circumstellar matter, supernovae: general, supernovae: individual: SNe 2012cg, supernovae: individual: 2012cu, dust, extinction Published in RUNG: 23.01.2018; Views: 3506; Downloads: 0 This document has many files! More... |
140. Supernova spectra below strong circumstellar interactionGiorgos Leloudas, E.Y. Hsiao, Joel Johansson, Keichi Maeda, T.J. Moriya, Jakob Nordin, Tanja Petrushevska, J. M. Silverman, Jesper Sollerman, M.D. Stritzinger, Francesco Taddia, D. Xu, 2015, original scientific article Abstract: We construct spectra of supernovae (SNe) interacting strongly with a circumstellar medium (CSM) by adding SN templates, a blackbody
continuum, and an emission-line spectrum. In a Monte Carlo simulation we vary a large number of parameters, such as the SN
type, brightness and phase, the strength of the CSM interaction, the extinction, and the signal to noise ratio (S/N) of the observed
spectrum. We generate more than 800 spectra, distribute them to ten different human classifiers, and study how the different simulation
parameters affect the appearance of the spectra and their classification. The SNe IIn showing some structure over the continuum were
characterized as “SNe IInS” to allow for a better quantification. We demonstrate that the flux ratio of the underlying SN to the
continuum fV is the single most important parameter determining whether a spectrum can be classified correctly. Other parameters,
such as extinction, S/N, and the width and strength of the emission lines, do not play a significant role. Thermonuclear SNe get
progressively classified as Ia-CSM, IInS, and IIn as fV decreases. The transition between Ia-CSM and IInS occurs at fV ∼ 0.2−0.3. It
is therefore possible to determine that SNe Ia-CSM are found at the (un-extincted) magnitude range −19.5 > M > −21.6, in very good
agreement with observations, and that the faintest SN IIn that can hide a SN Ia has M = −20.1. The literature sample of SNe Ia-CSM
shows an association with 91T-like SNe Ia. Our experiment does not support that this association can be attributed to a luminosity bias
(91T-like being brighter than normal events). We therefore conclude that this association has real physical origins and we propose that
91T-like explosions result from single degenerate progenitors that are responsible for the CSM. Despite the spectroscopic similarities
between SNe Ibc and SNe Ia, the number of misclassifications between these types was very small in our simulation and mostly at low
S/N. Combined with the SN luminosity function needed to reproduce the observed SN Ia-CSM luminosities, it is unlikely that SNe Ibc
constitute an important contaminant within this sample. We show how Type II spectra transition to IIn and how the Hα profiles vary
with fV . SNe IIn fainter than M = −17.2 are unable to mask SNe IIP brighter than M = −15. A more advanced simulation, including
radiative transfer, shows that our simplified model is a good first order approximation. The spectra obtained are in good agreement
with real data. Keywords: supernovae Published in RUNG: 22.01.2018; Views: 3582; Downloads: 0 This document has many files! More... |