Understanding type Ia supernovae through their U-band spectra

Context. Observations of type Ia supernovae (SNe Ia) can be used to derive accurate cosmological distances through empirical standardization techniques. Despite this success neither the progenitors of SNe Ia nor the explosion process are fully understood. The U-band region has been less well observed for nearby SNe, due to technical challenges, but is the most readily accessible band for high-redshift SNe. Aims. Using spectrophotometry from the Nearby Supernova Factory, we study the origin and extent of U-band spectroscopic variations in SNe Ia and explore consequences for their standardization and the potential for providing new insights into the explosion process. Methods. We divide the U-band spectrum into four wavelength regions λ(uNi), λ(uTi), λ(uSi) and λ(uCa). Two of these span the Ca H&K λλ 3934, 3969 complex. We employ spectral synthesis using SYNAPPS to associate the two bluer regions with Ni/Co and Ti. Results. The flux of the uTi feature is an extremely sensitive temperature/luminosity indicator, standardizing the SN peak luminosity to 0.116 ± 0.011 mag root mean square (RMS). A traditional SALT2.4 fit on the same sample yields a 0.135 mag RMS. Standardization using uTi also reduces the difference in corrected magnitude between SNe originating from different host galaxy environments. Early U-band spectra can be used to probe the Ni+Co distribution in the ejecta, thus offering a rare window into the source of light curve power. The uCa flux further improves standardization, yielding a 0.086 ± 0.010 mag RMS without the need to include an additional intrinsic dispersion to reach χ2∕dof ~ 1. This reduction in RMS is partially driven by an improved standardization of Shallow Silicon and 91T-like SNe.

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THE RELATION BETWEEN EJECTA VELOCITY, INTRINSIC COLOR, AND HOST-GALAXY MASS FOR HIGH-REDSHIFT TYPE Ia SUPERNOVAE

The Astrophysical Journal ◽

10.1088/0004-637x/748/2/127 ◽

2012 ◽

Vol 748 (2) ◽

pp. 127 ◽

Cited By ~ 31

Author(s):

Ryan J. Foley

Keyword(s):

High Redshift ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Type Ia ◽

Ia Supernovae

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An Efficient Approach to Obtaining Large Numbers of Distant Supernova Host Galaxy Redshifts

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2012.001 ◽

2013 ◽

Vol 30 ◽

Cited By ~ 9

Author(s):

C. Lidman ◽

V. Ruhlmann-Kleider ◽

M. Sullivan ◽

J. Myzska ◽

P. Dobbie ◽

...

Keyword(s):

High Redshift ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Wide Field ◽

Host Galaxies ◽

Dark Energy Survey ◽

Large Numbers ◽

Type Ia ◽

Ia Supernovae ◽

Energy Survey

AbstractWe use the wide-field capabilities of the 2 degree field fibre positioner and the AAOmega spectrograph on the Anglo-Australian Telescope (AAT) to obtain redshifts of galaxies that hosted supernovae during the first 3 years of the Supernova Legacy Survey (SNLS). With exposure times ranging from 10 to 60 ks per galaxy, we were able to obtain redshifts for 400 host galaxies in two SNLS fields, thereby substantially increasing the total number of SNLS supernovae with host galaxy redshifts. The median redshift of the galaxies in our sample that hosted photometrically classified Type Ia supernovae (SNe Ia) is z ~ 0.77, which is 25% higher than the median redshift of spectroscopically confirmed SNe Ia in the 3-year sample of the SNLS. Our results demonstrate that one can use wide-field fibre-fed multi-object spectrographs on 4-m telescopes to efficiently obtain redshifts for large numbers of supernova host galaxies over the large areas of the sky that will be covered by future high-redshift supernova surveys, such as the Dark Energy Survey.

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The Host Galaxies of High-Redshift Type Ia Supernovae

International Astronomical Union Colloquium ◽

10.1017/s0252921100009659 ◽

2005 ◽

Vol 192 ◽

pp. 555-560

Author(s):

Mark Sullivan ◽

Richard Ellis ◽

Keyword(s):

Cosmological Constant ◽

High Redshift ◽

Cosmological Parameters ◽

Type Systems ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Early Type ◽

Late Type ◽

Type Ia ◽

Ia Supernovae

SummaryWe present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies support earlier claims for a cosmological constant, which we demonstrate at ≃ 5σ significance, and the internal extinction implied is small even for late-type systems (AB < 0.2). Furthermore, the scatter observed in the SNe Ia Hubble diagrams correlates closely with host galaxy morphology. We find this scatter is smallest for SNe Ia occurring in early-type hosts and largest for those in late-type galaxies. Moreover, SNe residing in late-type hosts appear fainter in their light-curve-width-corrected luminosity than those in early-type hosts, as expected if a modest amount of dust extinction is a contributing factor. Thus, our data demonstrate that host galaxy extinction is unlikely to systematically dim distant SNe Ia in a manner that would produce a spurious cosmological constant.

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The Foundation Supernova Survey: Photospheric Velocity Correlations in Type Ia Supernovae

The Astrophysical Journal ◽

10.3847/1538-4357/ac2ee5 ◽

2021 ◽

Vol 923 (2) ◽

pp. 267

Author(s):

Kyle G. Dettman ◽

Saurabh W. Jha ◽

Mi Dai ◽

Ryan J. Foley ◽

Armin Rest ◽

...

Keyword(s):

High Velocity ◽

High Redshift ◽

Cosmic Time ◽

Stellar Mass ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Significant Difference ◽

Type Ia ◽

Show Evidence ◽

Ia Supernovae

Abstract The ejecta velocities of Type Ia supernovae (SNe Ia), as measured by the Si ii λ6355 line, have been shown to correlate with other supernova properties, including color and standardized luminosity. We investigate these results using the Foundation Supernova Survey, with a spectroscopic data release presented here, and photometry analyzed with the SALT2 light-curve fitter. We find that the Foundation data do not show significant evidence for an offset in color between SNe Ia with high and normal photospheric velocities, with Δc = 0.004 ± 0.015. Our SALT2 analysis does show evidence for redder high-velocity SNe Ia in other samples, including objects from the Carnegie Supernova Project, with a combined sample yielding Δc = 0.018 ± 0.008. When split on velocity, the Foundation SNe Ia also do not show a significant difference in Hubble diagram residual, ΔHR = 0.015 ± 0.049 mag. Intriguingly, we find that SN Ia ejecta velocity information may be gleaned from photometry, particularly in redder optical bands. For high-redshift SNe Ia, these rest-frame red wavelengths will be observed by the Nancy Grace Roman Space Telescope. Our results are in line with previous work that suggests SN Ia host-galaxy stellar mass is correlated with ejecta velocity: high-velocity SNe Ia are found nearly exclusively in high-stellar-mass hosts. However, host-galaxy properties alone do not explain velocity-dependent differences in supernova colors and luminosities across samples. Measuring and understanding the connection between intrinsic explosion properties and supernova environments, across cosmic time, will be important for precision cosmology with SNe Ia.

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Spectra of High-Redshift Type Ia Supernovae and a Comparison with Their Low-Redshift Counterparts

The Astronomical Journal ◽

10.1086/497635 ◽

2005 ◽

Vol 130 (6) ◽

pp. 2788-2803 ◽

Cited By ~ 44

Author(s):

I. M. Hook ◽

D. A. Howell ◽

G. Aldering ◽

R. Amanullah ◽

M. S. Burns ◽

...

Keyword(s):

High Redshift ◽

Type Ia Supernovae ◽

Type Ia ◽

Ia Supernovae

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Model-independent cosmic acceleration and redshift-dependent intrinsic luminosity in type-Ia supernovae

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833032 ◽

2019 ◽

Vol 625 ◽

pp. A15 ◽

Cited By ~ 8

Author(s):

I. Tutusaus ◽

B. Lamine ◽

A. Blanchard

Keyword(s):

Spline Interpolation ◽

High Redshift ◽

Cosmic Acceleration ◽

Expansion Rate ◽

Type Ia Supernovae ◽

Type Ia ◽

Model Independent ◽

Ia Supernovae ◽

The Universe ◽

Intrinsic Luminosity

Context. The cosmological concordance model (ΛCDM) is the current standard model in cosmology thanks to its ability to reproduce the observations. The first observational evidence for this model appeared roughly 20 years ago from the type-Ia supernovae (SNIa) Hubble diagram from two different groups. However, there has been some debate in the literature concerning the statistical treatment of SNIa, and their stature as proof of cosmic acceleration. Aims. In this paper we relax the standard assumption that SNIa intrinsic luminosity is independent of redshift, and examine whether it may have an impact on our cosmological knowledge and more precisely on the accelerated nature of the expansion of the universe. Methods. To maximise the scope of this study, we do not specify a given cosmological model, but we reconstruct the expansion rate of the universe through a cubic spline interpolation fitting the observations of the different cosmological probes: SNIa, baryon acoustic oscillations (BAO), and the high-redshift information from the cosmic microwave background (CMB). Results. We show that when SNIa intrinsic luminosity is not allowed to vary as a function of redshift, cosmic acceleration is definitely proven in a model-independent approach. However, allowing for redshift dependence, a nonaccelerated reconstruction of the expansion rate is able to fit, at the same level of ΛCDM, the combination of SNIa and BAO data, both treating the BAO standard ruler rd as a free parameter (not entering on the physics governing the BAO), and adding the recently published prior from CMB observations. We further extend the analysis by including the CMB data. In this case we also consider a third way to combine the different probes by explicitly computing rd from the physics of the early universe, and we show that a nonaccelerated reconstruction is able to nicely fit this combination of low- and high-redshift data. We also check that this reconstruction is compatible with the latest measurements of the growth rate of matter perturbations. We finally show that the value of the Hubble constant (H0) predicted by this reconstruction is in tension with model-independent measurements. Conclusions. We present a model-independent reconstruction of a nonaccelerated expansion rate of the universe that is able to fit all the main background cosmological probes nicely. However, the predicted value of H0 is in tension with recent direct measurements. Our analysis points out that a final reliable and consensual value for H0 is critical to definitively prove cosmic acceleration in a model-independent way.

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Uniformity of (V−Near‐Infrared) Color Evolution of Type Ia Supernovae and Implications for Host Galaxy Extinction Determination

The Astrophysical Journal ◽

10.1086/309263 ◽

2000 ◽

Vol 539 (2) ◽

pp. 658-674 ◽

Cited By ~ 89

Author(s):

Kevin Krisciunas ◽

N. C. Hastings ◽

Karen Loomis ◽

Russet McMillan ◽

Armin Rest ◽

...

Keyword(s):

Near Infrared ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Color Evolution ◽

Type Ia ◽

Ia Supernovae

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Binary Paths to Type Ia Supernovae Explosions: the Highlights

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312015347 ◽

2011 ◽

Vol 7 (S281) ◽

pp. 341-350

Author(s):

Lilia Ferrario

Keyword(s):

Binary System ◽

Main Channel ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Definitive Answer ◽

Type Ia ◽

Nuclear Burning ◽

External Galaxies ◽

Pass Through ◽

Ia Supernovae

AbstractThis symposium was focused on the hunt for the progenitors of Type Ia supernovae (SNe Ia). Is there a main channel for the production of SNe Ia? If so, are these elusive progenitors single degenerate or double degenerate systems? Although most participants seemed to favor the single degenerate channel, there was no general agreement on the type of binary system at play. An observational puzzle that was highlighted was the apparent paucity of supersoft sources in our Galaxy and also in external galaxies. The single degenerate channel (and as it was pointed out, quite possibly also the double degenerate channel) requires the binary system to pass through a phase of steady nuclear burning. However, the observed number of supersoft sources falls short by a factor of up to 100 in explaining the estimated birth rates of SNe Ia. Thus, are these supersoft sources somehow hidden away and radiating at different wavelengths, or are we missing some important pieces of this puzzle that may lead to the elimination of a certain class of progenitor? Another unanswered question concerns the dependence of SNe Ia luminosities on the age of their host galaxy. Several hypotheses were put forward, but none was singled out as the most likely explanation.It is fair to say that at the end of the symposium the definitive answer to the vexed progenitor question remained well and truly wide open.

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