scholarly journals A possible distance bias for type Ia supernovae with different ejecta velocities

2020 ◽  
Vol 493 (4) ◽  
pp. 5713-5725 ◽  
Author(s):  
M R Siebert ◽  
R J Foley ◽  
D O Jones ◽  
K W Davis
Keyword(s):  
Cosmological Model ◽  
Light Curve ◽  
Spectral Feature ◽  
Type Ia Supernovae ◽  
Curve Shape ◽  
Composite Spectra ◽  
Type Ia ◽  
Measured Distance ◽  
Ia Supernovae ◽  
Intrinsic Scatter

ABSTRACT After correcting for their light-curve shape and colour, Type Ia supernovae (SNe Ia) are precise cosmological distance indicators. However, there remains a non-zero intrinsic scatter in the differences between measured distance and that inferred from a cosmological model (i.e. Hubble residuals or HRs), indicating that SN Ia distances can potentially be further improved. We use the open-source relational data base kaepora to generate composite spectra with desired average properties of phase, light-curve shape, and HR. At many phases, the composite spectra from two subsamples with positive and negative average HRs are significantly different. In particular, in all spectra from 9 d before to 15 d after peak brightness, we find that SNe with negative HRs have, on average, higher ejecta velocities (as seen in nearly every optical spectral feature) than SNe with positive HRs. At +4 d relative to B-band maximum, using a sample of 62 SNe Ia, we measure a 0.091 ± 0.035 mag (2.7σ) HR step between SNe with Si ii λ6355 line velocities ($v_{Si\, rm{\small II}}$) higher/lower than −11 000 km s−1 (the median velocity). After light-curve shape and colour correction, SNe with higher velocities tend to have underestimated distance moduli relative to a cosmological model. The intrinsic scatter in our sample reduces from 0.094 to 0.082 mag after making this correction. Using the Si ii λ6355 velocity evolution of 115 SNe Ia, we estimate that a velocity difference >500 km s−1 exists at each epoch between the positive-HR and negative-HR samples with 99.4 per cent confidence. Finally at epochs later than +37 d, we observe that negative-HR composite spectra tend to have weaker spectral features in comparison to positive-HR composite spectra.

scholarly journals Measuring the Hubble constant with Type Ia supernovae as near-infrared standard candles

2018 ◽  
Vol 609 ◽  
pp. A72 ◽  
Author(s):  
Suhail Dhawan ◽  
Saurabh W. Jha ◽  
Bruno Leibundgut
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Sample Selection ◽  
Hubble Constant ◽  
Type Ia Supernovae ◽  
Curve Shape ◽  
Data Set ◽  
Optical Photometry ◽  
Type Ia ◽  
Ia Supernovae

The most precise local measurements of H0 rely on observations of Type Ia supernovae (SNe Ia) coupled with Cepheid distances to SN Ia host galaxies. Recent results have shown tension comparing H0 to the value inferred from CMB observations assuming ΛCDM, making it important to check for potential systematic uncertainties in either approach. To date, precise local H0 measurements have used SN Ia distances based on optical photometry, with corrections for light curve shape and colour. Here, we analyse SNe Ia as standard candles in the near-infrared (NIR), where luminosity variations in the supernovae and extinction by dust are both reduced relative to the optical. From a combined fit to 9 nearby calibrator SNe with host Cepheid distances from Riess et al. (2016) and 27 SNe in the Hubble flow, we estimate the absolute peak J magnitude MJ = −18.524 ± 0.041 mag and H0 = 72.8 ± 1.6 (statistical) ±2.7 (systematic) km s-1 Mpc-1. The 2.2% statistical uncertainty demonstrates that the NIR provides a compelling avenue to measuring SN Ia distances, and for our sample the intrinsic (unmodeled) peak J magnitude scatter is just ~0.10 mag, even without light curve shape or colour corrections. Our results do not vary significantly with different sample selection criteria, though photometric calibration in the NIR may be a dominant systematic uncertainty. Our findings suggest that tension in the competing H0 distance ladders is likely not a result of supernova systematics that could be expected to vary between optical and NIR wavelengths, like dust extinction. We anticipate further improvements in H0 with a larger calibrator sample of SNe Ia with Cepheid distances, more Hubble flow SNe Ia with NIR light curves, and better use of the full NIR photometric data set beyond simply the peak J-band magnitude.

scholarly journals Significant luminosity differences of two twin Type Ia supernovae

2019 ◽  
Vol 491 (4) ◽  
pp. 5991-5999 ◽  
Author(s):  
Ryan J Foley ◽  
Samantha L Hoffmann ◽  
Lucas M Macri ◽  
Adam G Riess ◽  
Peter J Brown ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectral Energy Distribution ◽  
Cosmological Parameters ◽  
Spectral Energy ◽  
Type Ia Supernovae ◽  
Curve Shape ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae ◽  
Peak Luminosity

ABSTRACT The Type Ia supernovae (SNe Ia) 2011by, hosted in NGC 3972, and 2011fe, hosted in M101, are optical ‘twins,’ having almost identical optical light-curve shapes, colours, and near-maximum-brightness spectra. However, SN 2011fe had significantly more ultraviolet (UV; 1600 < λ < 2500 Å) flux than SN 2011by before and at peak luminosity. Several theoretical models predict that SNe Ia with higher progenitor metallicity should (1) have additional UV opacity and thus lower UV flux; (2) have an essentially unchanged optical spectral-energy distribution; (3) have a similar optical light-curve shape; and (4) because of the excess neutrons, produce more stable Fe-group elements at the expense of radioactive 56Ni and thus have a lower peak luminosity. Following these predictions, Foley and Kirshner suggested that the difference in UV flux between SNe 2011by and 2011fe was the result of their progenitors having significantly different metallicities. They also measured a large, but insignificant, difference between the peak absolute magnitudes of the SNe (ΔMV, peak = 0.60 ± 0.36 mag), with SN 2011fe being more luminous. We present a new Cepheid-based distance to NGC 3972, substantially improving the precision of the distance measurement for SN 2011by. With these new data, we determine that the SNe have significantly different peak luminosities (ΔMV, peak = 0.335 ± 0.069 mag). Consequently, SN 2011fe produced 38 per cent more 56Ni than SN 2011by, consistent with predictions for progenitor metallicity differences for these SNe, although alternative models may also explain this difference. We discuss how progenitor metallicity differences can contribute to the intrinsic scatter for light-curve-shape-corrected SN luminosities, the use of ‘twin’ SNe for measuring distances, and implications for using SNe Ia for constraining cosmological parameters.

scholarly journals Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening

2020 ◽  
Vol 493 (4) ◽  
pp. 5617-5624
Author(s):  
Doron Kushnir ◽  
Eli Waxman
Keyword(s):  
Light Curve ◽  
Weighted Average ◽  
Far Infrared ◽  
Average Density ◽  
Light Curves ◽  
Type Ia Supernovae ◽  
Late Time ◽  
Simple Method ◽  
Type Ia ◽  
Ia Supernovae

ABSTRACT The finite time, τdep, over which positrons from β+ decays of 56Co deposit energy in type Ia supernovae ejecta lead, in case the positrons are trapped, to a slower decay of the bolometric luminosity compared to an exponential decline. Significant light-curve flattening is obtained when the ejecta density drops below the value for which τdep equals the 56Co lifetime. We provide a simple method to accurately describe this ‘delayed deposition’ effect, which is straightforward to use for analysis of observed light curves. We find that the ejecta heating is dominated by delayed deposition typically from 600 to 1200 d, and only later by longer lived isotopes 57Co and 55Fe decay (assuming solar abundance). For the relatively narrow 56Ni velocity distributions of commonly studied explosion models, the modification of the light curve depends mainly on the 56Ni mass-weighted average density, 〈ρ〉t3. Accurate late-time bolometric light curves, which may be obtained with JWST far-infrared (far-IR) measurements, will thus enable to discriminate between explosion models by determining 〈ρ〉t3 (and the 57Co and 55Fe abundances). The flattening of light curves inferred from recent observations, which is uncertain due to the lack of far-IR data, is readily explained by delayed deposition in models with $\langle \rho \rangle t^{3} \approx 0.2\, \mathrm{M}_{\odot }\, (10^{4}\, \textrm{km}\, \textrm{s}^{-1})^{-3}$, and does not imply supersolar 57Co and 55Fe abundances.

scholarly journals Observations of Type Ia Supernovae and Challenges for Cosmology

2005 ◽  
Vol 192 ◽  
pp. 525-533
Author(s):  
Weidong Li ◽  
Alexei V. Filippenko
Keyword(s):  
Dark Energy ◽  
Light Curve ◽  
Rise Time ◽  
Accelerating Universe ◽  
Type Ia Supernovae ◽  
Hubble Diagram ◽  
High Quality ◽  
Type Ia ◽  
Secondary Parameter ◽  
Ia Supernovae

SummaryObservations of Type Ia supernovae (SNe Ia) reveal correlations between their luminosities and light-curve shapes, and between their spectral sequence and photometric sequence. Assuming SNe Ia do not evolve at different redshifts, the Hubble diagram of SNe Ia may indicate an accelerating Universe, the signature of a cosmological constant or other forms of dark energy. Several studies raise concerns about the evolution of SNe Ia (e.g., the peculiarity rate, the rise time, and the color of SNe Ia at different redshifts), but all these studies suffer from the difficulties of obtaining high-quality spectroscopy and photometry for SNe Ia at high redshifts. There are also some troubling cases of SNe Ia that provide counter examples to the observed correlations, suggesting that a secondary parameter is necessary to describe the whole SN Ia family. Understanding SNe Ia both observationally and theoretically will be the key to boosting confidence in the SN Ia cosmological results.

scholarly journals The dependence of Type Ia Supernovae salt2 light-curve parameters on host galaxy morphology

2020 ◽  
Vol 499 (4) ◽  
pp. 5121-5135
Author(s):  
M V Pruzhinskaya ◽  
A K Novinskaya ◽  
N Pauna ◽  
P Rosnet
Keyword(s):  
Light Curve ◽  
Host Galaxy ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Early Type ◽  
Late Type ◽  
Hubble Diagram ◽  
Type Ia ◽  
Ia Supernovae ◽  
Galaxy Morphology

ABSTRACT Type Ia Supernovae (SNe Ia) are widely used to measure distances in the Universe. Despite the recent progress achieved in SN Ia standardization, the Hubble diagram still shows some remaining intrinsic dispersion. The remaining scatter in supernova luminosity could be due to the environmental effects that are accounted for as mass step correction in the current cosmological analyses. In this work, we compare the local and global colour (U − V), the local star formation rate, and the host stellar mass to the host galaxy morphology. The observed trends suggest that the host galaxy morphology is a relevant parameter to characterize the SN Ia environment. Therefore, we study the influence of host galaxy morphology on light-curve parameters of SNe Ia from the pantheon cosmological supernova sample. We determine the Hubble morphological type of host galaxies for a subsample of 330 SNe Ia. We confirm that the salt2 stretch parameter x1 depends on the host morphology with the p-value ∼10−14. The supernovae with lower stretch value are hosted mainly by elliptical and lenticular galaxies. No correlation for the salt2 colour parameter c is found. We also examine Hubble diagram residuals for supernovae hosted by ‘early-type’ and ‘late-type’ morphological groups of galaxies. The analysis reveals that the mean distance modulus residual in early-type galaxies is smaller than the one in late-type galaxies, which means that early-type galaxies contain brighter supernovae after stretch and colour corrections. However, we do not observe any difference in the residual dispersion for these two morphological groups. The obtained results are in the line with other analyses showing environmental dependence of SN Ia light-curve parameters and luminosity. We confirm the importance of including a host galaxy parameter into the standardization procedure of SNe Ia for further cosmological studies.

scholarly journals Testing the isotropy of the Universe with Type Ia supernovae in a model-independent way

2017 ◽  
Vol 474 (3) ◽  
pp. 3516-3522 ◽  
Author(s):  
Yu-Yang Wang ◽  
F Y Wang
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Light Curve ◽  
Type Ia Supernovae ◽  
Anisotropic Universe ◽  
Preferred Direction ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe

Abstract In this paper, we study an anisotropic universe model with Bianchi-I metric using Joint light-curve analysis (JLA) sample of Type Ia supernovae (SNe Ia). Because light-curve parameters of SNe Ia vary with different cosmological models and SNe Ia samples, we fit the SNe Ia light-curve parameters and cosmological parameters simultaneously employing Markov chain Monte Carlo method. Therefore, the results on the amount of deviation from isotropy of the dark energy equation of state (δ), and the level of anisotropy of the large-scale geometry (Σ0) at present, are totally model-independent. The constraints on the skewness and cosmic shear are −0.101 < δ < 0.071 and −0.007 < Σ0 < 0.008. This result is consistent with a standard isotropic universe (δ = Σ0 = 0). However, a moderate level of anisotropy in the geometry of the Universe and the equation of state of dark energy, is allowed. Besides, there is no obvious evidence for a preferred direction of anisotropic axis in this model.

Time Dilation from Spectral Feature Age Measurements of Type IA Supernovae.

1997 ◽  
Vol 114 ◽  
pp. 722 ◽  
Author(s):  
A. G. Riess ◽  
A. V. Filippenko ◽  
D. C. Leonard ◽  
B. P. Schmidt ◽  
N. Suntzeff ◽  
...  
Keyword(s):  
Spectral Feature ◽  
Time Dilation ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae

scholarly journals Testing the distance–duality relation from strong gravitational lensing, type Ia supernovae and gamma-ray bursts data up to redshift z ∼ 3.6

2017 ◽  
Vol 26 (09) ◽  
pp. 1750097 ◽  
Author(s):  
Xiangyun Fu ◽  
Pengcheng Li
Keyword(s):  
Cosmological Model ◽  
Gravitational Lensing ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Type Ia Supernovae ◽  
Redshift Range ◽  
Strong Gravitational Lensing ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae

In this paper, we perform a cosmological model-independent test of the cosmic distance–duality relation (CDDR) in terms of the ratio of angular diameter distance (ADD) [Formula: see text] from strong gravitational lensing (SGL) and the ratio of luminosity distance (LD) [Formula: see text] obtained from the joint of type Ia supernovae (SNIa) Union2.1 compilation and the latest Gamma-Ray Bursts (GRBs) data, where the superscripts s and l correspond to the redshifts [Formula: see text] and [Formula: see text] at the source and lens from SGL samples. The purpose of combining GRB data with SNIa compilation is to test CDDR in a wider redshift range. The LD associated with the redshifts of the observed ADD is obtained through two cosmological model-independent methods, namely, method A: binning the SNIa+GRBs data, and method B: reconstructing the function of DL by combining the Crossing Statistic with the smoothing method. We find that CDDR is compatible with the observations at [Formula: see text] confidence level for the power law model which is assumed to describe the mass distribution of lensing systems with method B in a wider redshift range.

scholarly journals R-band light-curve properties of Type Ia supernovae from the (intermediate) Palomar Transient Factory

2018 ◽  
Vol 483 (4) ◽  
pp. 5045-5076 ◽  
Author(s):  
S Papadogiannakis ◽  
A Goobar ◽  
R Amanullah ◽  
M Bulla ◽  
S Dhawan ◽  
...  
Keyword(s):  
Light Curve ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae

scholarly journals ASASSN-18tb: a most unusual Type Ia supernova observed by TESS and SALT

2019 ◽  
Vol 487 (2) ◽  
pp. 2372-2384 ◽  
Author(s):  
P J Vallely ◽  
M Fausnaugh ◽  
S W Jha ◽  
M A Tucker ◽  
Y Eweis ◽  
...  
Keyword(s):  
Light Curve ◽  
Power Law ◽  
Type Ia Supernovae ◽  
Normal Type ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Early Rise ◽  
Ia Supernovae ◽  
Best Fit ◽  
Unusual Type

ABSTRACT We present photometric and spectroscopic observations of the unusual Type Ia supernova ASASSN-18tb, including a series of Southern African Large Telescope spectra obtained over the course of nearly six months and the first observations of a supernova by the Transiting Exoplanet Survey Satellite. We confirm a previous observation by Kollmeier et al. showing that ASASSN-18tb is the first relatively normal Type Ia supernova to exhibit clear broad (∼1000 km s−1) H α emission in its nebular-phase spectra. We find that this event is best explained as a sub-Chandrasekhar mass explosion producing $M_{\mathrm{ Ni}} \approx 0.3\,\, \rm {M}_\odot$. Despite the strong H α signature at late times, we find that the early rise of the supernova shows no evidence for deviations from a single-component power-law and is best fit with a moderately shallow power law of index 1.69 ± 0.04. We find that the H α luminosity remains approximately constant after its initial detection at phase +37 d, and that the H α velocity evolution does not trace that of the Fe iii λ4660 emission. These suggest that the H α emission arises from a circumstellar medium (CSM) rather than swept-up material from a non-degenerate companion. However, ASASSN-18tb is strikingly different from other known CSM-interacting Type Ia supernovae in a number of significant ways. Those objects typically show an H α luminosity two orders of magnitude higher than what is seen in ASASSN-18tb, pushing them away from the empirical light-curve relations that define ‘normal’ Type Ia supernovae. Conversely, ASASSN-18tb exhibits a fairly typical light curve and luminosity for an underluminous or transitional SN Ia, with MR ≈ −18.1 mag. Moreover, ASASSN-18tb is the only SN Ia showing H α from CSM interaction to be discovered in an early-type galaxy.

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