Cosmological Standard Candles Research Articles

A model-independent tripartite test of cosmic distance relations

Cosmological distances are fundamental observables in cosmology. The luminosity (D L), angular diameter (D A) and gravitational wave (D GW) distances are all trivially related in General Relativity assuming no significant absorption of photons in the extragalactic medium, also known as cosmic opacity. Supernovae have long been the main cosmological standard candle, but bright standard sirens are now a proven alternative, with the advantage of not requiring calibration with other astrophysical sources. Moreover, they can also measure deviations from modified gravity through discrepancies between D L and D GW. However, both gravitational and cosmological parameters are degenerate in the Hubble diagram, making it hard to properly detect beyond standard model physics. Finally, recently a model-independent method named FreePower was proposed to infer angular diameter distances from large-scale structure which is independent of the knowledge of both early universe and dark energy physics. In this paper we propose a tripartite test of the ratios of these three distances with minimal amount of assumptions regarding cosmology, the early universe, cosmic opacity and modified gravity. We proceed to forecast this test with a combination of LSST and Roman supernovae, Einstein Telescope bright sirens and a joint DESI-like + Euclid-like galaxy survey. We find that even in this very model-independent approach we will be able to detect, in each of many redshift bins, percent-level deviations in these ratios of distances, allowing for very precise consistency checks of ΛCDM and standard physics. It can also result in sub-percent measurements of H 0.

Nebular-phase spectra of Type Ia supernovae from the Las Cumbres Observatory Global Supernova Project

ABSTRACT The observed diversity in Type Ia supernovae (SNe Ia) – the thermonuclear explosions of carbon–oxygen white dwarf stars used as cosmological standard candles – is currently met with a variety of explosion models and progenitor scenarios. To help improve our understanding of whether and how often different models contribute to the occurrence of SNe Ia and their assorted properties, we present a comprehensive analysis of seven nearby SNe Ia. We obtained one to two epochs of optical spectra with Gemini Observatory during the nebular phase (>200 d past peak) for each of these events, all of which had time series of photometry and spectroscopy at early times (the first ∼8 weeks after explosion). We use the combination of early- and late-time observations to assess the predictions of various models for the explosion (e.g. double-detonation, off-centre detonation, stellar collisions), progenitor star (e.g. ejecta mass, metallicity), and binary companion (e.g. another white dwarf or a non-degenerate star). Overall, we find general consistency in our observations with spherically symmetric models for SN Ia explosions, and with scenarios in which the binary companion is another degenerate star. We also present an in-depth analysis of SN 2017fzw, a member of the subgroup of SNe Ia which appear to be transitional between the subluminous ‘91bg-like’ events and normal SNe Ia, and for which nebular-phase spectra are rare.

The observable supernova rate in galaxy–galaxy lensing systems with the TESS satellite

ABSTRACT The Transiting Exoplanet Survey Satellite (TESS) is the latest observational effort to find exoplanets and map bright transient optical phenomena. Supernovae (SNe) are particularly interesting as cosmological standard candles for cosmological distance measures. The limiting magnitude of TESS strongly constrains SN detection to the very nearby Universe (m ∼ 19, z < 0.05). We explore the possibility that more distant SNe that are gravitationally lensed and magnified by a foreground galaxy can be detected by TESS, an opportunity to measure the time delay between light paths and constrain the Hubble constant independently. We estimate the rate of occurrence of such systems, assuming reasonable distributions of magnification, host dust attenuation, and redshift. There are approximately 16 Type Ia SNe (SNIa) and 43 core-collapse SNe (SNcc) expected to be observable with TESS each year, which translates to 18 and 43 per cent chance of detection per year, respectively. Monitoring the largest collections of known strong galaxy–galaxy lenses from Petrillo et al., this translates into 0.6 and 1.3 per cent chances of an SNIa and an SNcc per year. The TESS all-sky detection rates are lower than those of the Zwicky Transient Facility and Vera Rubin Observatory. However, on the ecliptic poles, TESS performs almost as well as its all-sky search, thanks to its continuous coverage: 2 and 4 per cent chance of an observed SN (Ia or cc) each year. These rates argue for timely processing of full-frame TESS imaging to facilitate follow-up and should motivate further searches for low-redshift lensing system.

New insights into the use of Ultra Long Period Cepheids as cosmological standard candles

ABSTRACT Ultra Long Period Cepheids (ULPs) are pulsating variable stars with a period longer than 80 d and have been hypothesized to be the extension of the Classical Cepheids (CCs) at higher masses and luminosities. If confirmed as standard candles, their intrinsic luminosities, ∼1 to ∼3 mag brighter than typical CCs, would allow to reach the Hubble flow and, in turn, to determine the Hubble constant, H0, in one step, avoiding the uncertainties associated with the calibration of primary and secondary indicators. To investigate the accuracy of ULPs as cosmological standard candles, we first collect all the ULPs known in the literature. The resulting sample includes 63 objects with a very large metallicity spread with 12 + log ([O/H]) ranging from 7.2 to 9.2 dex. The analysis of their properties in the VI period–Wesenheit plane and in the colour–magnitude diagram (CMD) supports the hypothesis that the ULPs are the extension of CCs at longer periods, higher masses and luminosities, even if, additional accurate and homogeneous data and a devoted theoretical scenario are needed to get firm conclusions. Finally, the three M31 ULPs, 8-0326, 8-1498, and H42, are investigated in more detail. For 8-1498 and H42, we cannot confirm their nature as ULPs, due to the inconsistency between their position in the CMD and the measured periods. For 8-0326, the light curve model fitting technique applied to the available time-series data allows us to constrain its intrinsic stellar parameters, distance, and reddening.

Studying Type II supernovae as cosmological standard candles using the Dark Energy Survey

ABSTRACT Despite vast improvements in the measurement of the cosmological parameters, the nature of dark energy and an accurate value of the Hubble constant (H0) in the Hubble–Lemaître law remain unknown. To break the current impasse, it is necessary to develop as many independent techniques as possible, such as the use of Type II supernovae (SNe II). The goal of this paper is to demonstrate the utility of SNe II for deriving accurate extragalactic distances, which will be an asset for the next generation of telescopes where more-distant SNe II will be discovered. More specifically, we present a sample from the Dark Energy Survey Supernova Program (DES-SN) consisting of 15 SNe II with photometric and spectroscopic information spanning a redshift range up to 0.35. Combining our DES SNe with publicly available samples, and using the standard candle method (SCM), we construct the largest available Hubble diagram with SNe II in the Hubble flow (70 SNe II) and find an observed dispersion of 0.27 mag. We demonstrate that adding a colour term to the SN II standardization does not reduce the scatter in the Hubble diagram. Although SNe II are viable as distance indicators, this work points out important issues for improving their utility as independent extragalactic beacons: find new correlations, define a more standard subclass of SNe II, construct new SN II templates, and dedicate more observing time to high-redshift SNe II. Finally, for the first time, we perform simulations to estimate the redshift-dependent distance-modulus bias due to selection effects.

Spectral Analysis of Fermi-LAT Gamma-Ray Bursts with Known Redshift and their Potential Use as Cosmological Standard Candles

Abstract Long duration gamma-ray bursts may serve as standard candles to constrain cosmological parameters by probing the Hubble diagram well beyond the range of redshift currently accessible using SNe Ia. The standardization of gamma-ray bursts (GRBs) is based on phenomenological relations between two or more parameters found from spectral modeling, one of which is strongly dependent on the cosmological model. The Amati relation links the source-frame energy at which the prompt gamma-ray spectral energy distribution νF ν peaks, and the isotropic-equivalent bolometric energy emitted during the prompt phase. We performed spectral analysis of 26 GRBs with known redshift that have been detected by the Fermi-Large Area Telescope (LAT) during its nine years of operations from 2008 July to 2017 September, thus extending the computation of E iso to the 100 MeV range. Multiple components are required to fit the spectra of a number of GRBs. We found that the Amati relation is satisfied by the 25 LGRBs, with best-fit parameters similar to previous studies that used data from different satellite experiments, while the only short GRB with known redshift is an outlier. Using the Amati relation, we extend the Hubble diagram to redshift 4.35 and constrain the Hubble constant and dark-energy density in the ΛCDM model, with Fermi-LAT GRBs alone and together with another sample of 94 GRBs and with the latest Supernovae type-Ia data. Our results are consistent with the currently acceptable ranges of those cosmological parameters within errors.

Machine learning and the future of supernova cosmology

Machine Learning methods will play a fundamental role in our ability to optimize the science output from the next generation of large scale surveys. Given the peculiarities of astronomical data, it is crucial that algorithms are adapted to the data situation at hand. In this comment, I review the recent efforts towards the development of automatic systems to identify and classify supernova with the goal of enabling their use as cosmological standard candles.

Spectral analysis of the binary nucleus of the planetary nebula Hen 2-428 – first results

Abstract Identifying progenitor systems for the double-degenerate scenario is crucial to check the reliability of type Ia supernovae as cosmological standard candles. Santander-Garcia et al. (2015) claimed that Hen 2-428 has a doubledegenerate core whose combined mass significantly exceeds the Chandrasekhar limit. Together with the short orbital period (4.2 hours), the authors concluded that the system should merge within a Hubble time triggering a type Ia supernova event. Garcia-Berro et al. (2016) explored alternative scenarios to explain the observational evidence, as the high mass conclusion is highly unlikely within predictions from stellar evolution theory. They conclude that the evidence supporting the supernova progenitor status of the system is premature. Here we present the first quantitative spectral analysis of Hen 2-428which allows us to derive the effective temperatures, surface gravities and helium abundance of the two CSPNe based on state-of-the-art, non-LTE model atmospheres. These results provide constrains for further studies of this particularly interesting system.

Quasars as Cosmological Standard Candles

We propose the use of quasars with accretion rate near to Eddington ratio (extreme quasars) as standard candles. The selection criteria is based on the Eigenvector 1 (E1) formalism. Our first sample is a selection of 334 optical quasar spectra from the SDSS DR7 database with a S/N \gt 20. Using the E1, we define primary and secondary selection criteria in the optical spectral range. We show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Our results are consistent with concordance cosmology but we need to work with other spectral ranges to take into account the quasar orientation, among other constrains.

Reddened, Redshifted, or Intrinsically Red? Understanding Near-ultraviolet Colors of Type Ia Supernovae

Abstract The intrinsic colors of Type Ia supernovae (SNe Ia) are important to understanding their use as cosmological standard candles. Understanding the effects of reddening and redshift on the observed colors are complicated and dependent on the intrinsic spectrum, the filter curves, and the wavelength dependence of reddening. We present ultraviolet and optical data of a growing sample of SNe Ia observed with the Ultraviolet/Optical Telescope on the Swift spacecraft and use this sample to re-examine the near-UV (NUV) colors of SNe Ia. We find that a small amount of reddening (E(B − V) = 0.2 mag) could account for the difference between groups designated as NUV-blue and NUV-red, and a moderate amount of reddening (E(B − V) = 0.5 mag) could account for the whole NUV-optical differences. The reddening scenario, however, is inconsistent with the mid-UV colors and color evolution. The effect of redshift alone only accounts for part of the variation. Using a spectral template of SN2011fe, we can forward model the effects of redshift and reddening and directly compare those with the observed colors. We find that some SNe are consistent with reddened versions of SN2011fe, but most SNe Ia are much redder in the uvw1 − v color than SN2011fe reddened to the same b − v color. The absolute magnitudes show that two out of five NUV-blue SNe Ia are blue because their near-UV luminosity is high, and the other three are optically fainter. We also show that SN 2011fe is not a “normal” SN Ia in the UV, but has colors placing it at the blue extreme of our sample.

A UNIFIED MODEL FOR GRB PROMPT EMISSION FROM OPTICAL TO γ-RAYS; EXPLORING GRBs AS STANDARD CANDLES

ABSTRACT The origin of prompt emission from gamma-ray bursts (GRBs) remains to be an open question. Correlated prompt optical and γ-ray emission observed in a handful of GRBs strongly suggests a common emission region, but failure to adequately fit the broadband GRB spectrum prompted the hypothesis of different emission mechanisms for the low- and high-energy radiations. We demonstrate that our multi-component model for GRB γ-ray prompt emission provides an excellent fit to GRB 110205A from optical to γ-ray energies. Our results show that the optical and highest γ-ray emissions have the same spatial and spectral origin, which is different from the bulk of the X- and softest γ-ray radiation. Finally, our accurate redshift estimate for GRB 110205A demonstrates promise for using GRBs as cosmological standard candles.

Induced gravitational collapse at extreme cosmological distances: the case of GRB 090423

CONTEXT: The induced gravitational collapse (IGC) scenario has been introduced in order to explain the most energetic gamma ray bursts (GRBs), Eiso=10^{52}-10^{54}erg, associated with type Ib/c supernovae (SNe). It has led to the concept of binary-driven hypernovae (BdHNe) originating in a tight binary system composed by a FeCO core on the verge of a SN explosion and a companion neutron star (NS). Their evolution is characterized by a rapid sequence of events: [...]. AIMS: We investigate whether GRB 090423, one of the farthest observed GRB at z=8.2, is a member of the BdHN family. METHODS: We compare and contrast the spectra, the luminosity evolution and the detectability in the observations by Swift of GRB 090423 with the corresponding ones of the best known BdHN case, GRB 090618. RESULTS: Identification of constant slope power-law behavior in the late X-ray emission of GRB 090423 and its overlapping with the corresponding one in GRB 090618, measured in a common rest frame, represents the main result of this article. This result represents a very significant step on the way to using the scaling law properties, proven in Episode 3 of this BdHN family, as a cosmological standard candle. CONCLUSIONS: Having identified GRB 090423 as a member of the BdHN family, we can conclude that SN events, leading to NS formation, can already occur already at z=8.2, namely at 650 Myr after the Big Bang. It is then possible that these BdHNe originate stem from 40-60 M_{\odot} binaries. They are probing the Population II stars after the completion and possible disappearance of Population III stars.

Type Ia supernova host galaxies as seen with IFU spectroscopy

(abridged) We used the wide-field IFU spectrograph PMAS/PPAK at the 3.5m telescope of Calar Alto Observatory to observe six nearby spiral galaxies that hosted SNe Ia. Spatially resolved 2D maps of the properties of the ionized gas and the stellar populations were derived. Five of the observed galaxies have an ongoing star formation rate of 1-5 M_sun/yr and mean stellar population ages ~5 Gyr. The sixth galaxy shows no star formation and has an about 12 Gyr old stellar population. All galaxies have stellar masses larger than 2E+10 M_sun and metallicities above solar. Four galaxies show negative radial metallicity gradients of the ionized gas up to -0.058 dex/kpc and one has nearly uniform metallicity with a possible shallow positive slope. The stellar components show shallower negative metallicity gradients up to -0.03 dex/kpc. We find no clear correlation between the properties of the galaxy and those of the supernovae, which may be because of the small ranges spanned by the galaxy parameters. However, we note that the Hubble residuals are on average positive while negative Hubble residuals are expected for SNe Ia in massive hosts such as the galaxies in our sample. In conclusion, IFU spectroscopy on 4-m telescopes is a viable technique for studying host galaxies of nearby SNe Ia. It allows one to correlate the supernova properties with the properties of their host galaxies at the projected positions of the supernovae. Our current sample of six galaxies is too small to draw conclusions about the SN Ia progenitors or correlations with the galaxy properties, but the ongoing CALIFA IFU survey will provide a solid basis to exploit this technique more and improve our understanding of SNe Ia as cosmological standard candles.

The possible impact of gamma-ray burst detector thresholds on cosmological standard candles

GRB satellites are relatively inefficient detectors of dim hard bursts because they trigger on photon counts, which are number-biased against hard photons. Therefore, for example, given two bursts of identical peak luminosity near the detection threshold, a dim soft burst will be preferentially detected over a dim hard burst. This detector bias can create or skew an apparent correlation where increasingly hard GRBs appear increasingly bright. Although such correlations may be obfuscated by a middle step where GRBs need to be bright enough to have their actual redshifts determined, it is found that the bias is generally pervasive. This result is derived here through simulations convolving a wide variety of possible GRB brightnesses and spectra with the BATSE Large Area Detectors (LAD) detection thresholds. The presented analyses indicate that the rest-frame $\nu F_{\nu}$ spectrum peak energy of long-duration GRBs, $\epi$, is not a good cosmological standard candle without significant corrections for selection effects. Therefore, the appearance of $\epi$ in seeming correlations such as the Amati ($E_{iso}-\epi$), Ghirlanda ($E_{\gamma}-\epi$), and $L_{iso}-\epi$ relations is statistically real but strongly influenced by so far uncalibrated GRB detector thresholds.

An asymmetric explosion as the origin of spectral evolution diversity in type Ia supernovae

Type Ia supernovae form an observationally uniform class of stellar explosions, in that more luminous objects have smaller decline-rates. This one-parameter behaviour allows type Ia supernovae to be calibrated as cosmological 'standard candles', and led to the discovery of an accelerating Universe. Recent investigations, however, have revealed that the true nature of type Ia supernovae is more complicated. Theoretically, it has been suggested that the initial thermonuclear sparks are ignited at an offset from the centre of the white-dwarf progenitor, possibly as a result of convection before the explosion. Observationally, the diversity seen in the spectral evolution of type Ia supernovae beyond the luminosity-decline-rate relation is an unresolved issue. Here we report that the spectral diversity is a consequence of random directions from which an asymmetric explosion is viewed. Our findings suggest that the spectral evolution diversity is no longer a concern when using type Ia supernovae as cosmological standard candles. Furthermore, this indicates that ignition at an offset from the centre is a generic feature of type Ia supernovae.

Reducing the weak lensing noise for the gravitational wave Hubble diagram using the non-Gaussianity of the magnification distribution

Gravitational wave sources are a promising cosmological standard candle because their intrinsic luminosities are determined by fundamental physics (and are insensitive to dust extinction). They are, however, affected by weak lensing magnification due to the gravitational lensing from structures along the line of sight. This lensing is a source of uncertainty in the distance determination, even in the limit of perfect standard candle measurements. It is commonly believed that the uncertainty in the distance to an ensemble of gravitational wave sources is limited by the standard deviation of the lensing magnification distribution divided by the square root of the number of sources. Here we show that by exploiting the non-Gaussian nature of the lensing magnification distribution, we can improve this distance determination, typically by a factor of 2--3; we provide a fitting formula for the effective distance accuracy as a function of redshift for sources where the lensing noise dominates.

Hubble diagram as a probe of minicharged particles

The luminosity-redshift relation of cosmological standard candles provides information about the relative energy composition of our Universe. In particular, the observation of type Ia supernovae up to a redshift of $z\ensuremath{\sim}2$ indicates a universe which is dominated today by dark matter and dark energy. The propagation distance of light from these sources is of the order of the Hubble radius and serves as a very sensitive probe of feeble inelastic photon interactions with background matter, radiation, or magnetic fields. In this paper we discuss the limits on minicharged particle models arising from a dimming effect in supernova surveys. We briefly speculate about a strong dimming effect as an alternative to dark energy.

Improving the calibration of Type Ia supernovae using late-time light curves

The use of Type la supernovae (SNe Ia) as cosmological standard candles is a key to solving the mystery of dark energy. Improving the calibration of SNe Ia increases their power as cosmological standard candles. We find tentative evidence for a correlation between the late-time light-curve slope and the peak luminosity of SNe Ia in the B band; brighter SNe Ia seem to have shallower light-curve slopes between 100 and 150 d from maximum light. Using a Markov Chain Monte Carlo (MCMC) analysis in calibrating SNe Ia, we are able to simultaneously take into consideration the effect of dust extinction, the luminosity and light-curve width correlation (parametrized by Δm 15 ), and the luminosity and late-time light-curve slope correlation. For the available sample of 11 SNe Ia with well-measured late-time light curves, we find that correcting for the correlation between luminosity and late-time light-curve slope of the SNe Ia leads to an intrinsic dispersion of 0.12 mag in the Hubble diagram. Our results have significant implications for future supernova surveys aimed to illuminate the nature of dark energy.

A Model-independent Photometric Redshift Estimator for Type Ia Supernovae

The use of Type Ia supernovae (SNe Ia) as cosmological standard candles is fundamental in modern observational cosmology. In this Letter, we derive a simple empirical photometric redshift estimator for SNe Ia using a training set of SNe Ia with multiband (griz) light curves and spectroscopic redshifts obtained by the Supernova Legacy Survey (SNLS). This estimator is analytical and model-independent; it does not use spectral templates. We use all the available SNe Ia from SNLS with near-maximum photometry in griz (a total of 40 SNe Ia) to train and test our photometric redshift estimator. The difference between the estimated redshifts zphot and the spectroscopic redshifts zspec, (zphot - zspec)/(1 + zspec), has rms dispersions of 0.031 for 20 SNe Ia used in the training set, and 0.050 for 20 SNe Ia not used in the training set. The dispersion is of the same order of magnitude as the flux uncertainties at peak brightness for the SNe Ia. There are no outliers. This photometric redshift estimator should significantly enhance the ability of observers to accurately target high-redshift SNe Ia for spectroscopy in ongoing surveys. It will also dramatically boost the cosmological impact of very large future supernova surveys, such as those planned for the Advanced Liquid-mirror Probe for Astrophysics, Cosmology, and Asteroids (ALPACA) and the Large Synoptic Survey Telescope (LSST).

Testing quintessence models with GRBs

Using the narrow clustering of the geometrically corrected gamma-ray energies released by Gamma-Ray Bursts (GRBs), we investigate the possibility of using these sources as cosmological standard candles to discriminate between different models for quintessence.