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151. Revised redshifts of the Pantheon supernovae Ia
ID:
ivo://CDS.VizieR/J/ApJ/902/14
Title:
Revised redshifts of the Pantheon supernovae Ia
Short Name:
J/ApJ/902/14
Date:
17 Mar 2022 14:41:40
Publisher:
CDS
Description:
Redshifts used in current cosmological supernova samples are measured using two primary techniques, one based on well-measured host galaxy spectral lines and the other based on supernova-dominated spectra. Here, we construct an updated Pantheon catalog with revised redshifts, redshift sources, and estimated uncertainties for the entire sample to investigate whether these two techniques yield consistent results. The best-fit cosmological parameters using these two measurement techniques disagree, with a supernova-only sample producing {Omega}_m_ 3.2{sigma} higher and H_0_ 2.5{sigma} lower than a hostz-only sample, and we explore several possible sources of bias that could result from using the lower-precision supernova-dominated redshifts. In a pilot study, we show that using a host redshift-only subsample will generically produce lower {Omega}_m_ and matter density {Omega}_m_h^2^ and slightly higher H_0_ than previous analysis which, for the Pantheon data set, could result in supernova and cosmic microwave background measurements agreeing on {Omega}_m_h^2^ despite tension in H_0_. To obtain rigorous results, though, the Pantheon catalog should be improved by obtaining host spectra for supernovae that have faded, and future surveys should be designed to use host galaxy redshifts rather than lower-precision methods.
152. SALT2 parameters and distances for SNe
ID:
ivo://CDS.VizieR/J/MNRAS/433/2240
Title:
SALT2 parameters and distances for SNe
Short Name:
J/MNRAS/433/2240
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a cosmological analysis of the Lick Observatory Supernova Search (LOSS) Type Ia supernova (SN Ia) photometry sample introduced by Ganeshalingam et al. (2010ApJS..190..418G, Cat. J/ApJS/190/418). These supernovae (SNe) provide an effective anchor point to estimate cosmological parameters when combined with data sets at higher redshift. The data presented by Ganeshalingam et al. have been rereduced in the natural system of the Katzman Automatic Imaging Telescope (KAIT) and Nickel telescopes to minimize systematic uncertainties. We have run the light-curve-fitting software SALT2 on our natural-system light curves to measure light-curve parameters for LOSS light curves and available SN Ia data sets in the literature. We present a Hubble diagram of 586 SNe in the redshift range z=0.01-1.4 with a residual scatter of 0.176mag. Of the 226 low-z SNe Ia in our sample, 91 objects are from LOSS, including 45 without previously published distances. Assuming a flat Universe, we find that the best fit for the dark energy equation-of-state parameter w=-0.86^+0.13^_-0.16_(stat)+/-0.11(sys) from SNe alone, consistent with a cosmological constant. Our data prefer a Universe with an accelerating rate of expansion with 99.999% confidence. When looking at Hubble residuals as a function of host-galaxy morphology, we do not see evidence for a significant trend, although we find a somewhat reduced scatter in Hubble residuals from SNe residing within a projected distance <10kpc of the host-galaxy nucleus ({sigma}=0.156mag). Similar to the results of Blondin, Mandel and Kirshner and Silverman et al. (2012AJ....143..126B, Cat. J/AJ/143/126), we find that Hubble residuals do not correlate with the expansion velocity of SiII{lambda}6355 measured in optical spectra near maximum light. Our data are consistent with no presence of a local "Hubble bubble". Improvements in cosmological analyses within low-z samples can be achieved by better constraining calibration uncertainties in the zero-points of photometric systems.
153. Sample of 141 SNe Ia
ID:
ivo://CDS.VizieR/J/A+A/644/A176
Title:
Sample of 141 SNe Ia
Short Name:
J/A+A/644/A176
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of an on-going effort to identify, understand and correct for astrophysics biases in the standardization of Type Ia supernovae (SN Ia) for cosmology, we have statistically classified a large sample of nearby SNe Ia into those that are located in predominantly younger or older environments. This classification is based on the specific star formation rate measured within a projected distance of 1kpc from each SN location (LsSFR). This is an important refinement compared to using the local star formation rate directly, as it provides a normalization for relative numbers of available SN progenitors and is more robust against extinction by dust. We find that the SNe Ia in predominantly younger environments are {DELTA}Y=0.163+/-0.029mag (5.7{sigma}) fainter than those in predominantly older environments after conventional light-curve standardization. This is the strongest standardized SN Ia brightness systematic connected to the host-galaxy environment measured to date. The well-established step in standardized brightnesses between SNe Ia in hosts with lower or higher total stellar masses is smaller, at {DELTA}M=0.119+/-0.032mag (4.5{sigma}), for the same set of SNe Ia. When fit simultaneously, the environment-age offset remains very significant, with {DELTA}Y=0.129+/-0.032mag (4.0{sigma}), while the global stellar mass step is reduced to {DELTA}M=0.064+/-0.029mag (2.2{sigma}). Thus, approximately 70% of the variance from the stellar mass step is due to an underlying dependence on environment-based progenitor age. Also, we verify that using the local star formation rate alone is not as powerful as LsSFR at sorting SNe Ia into brighter and fainter subsets. Standardization that only uses the SNe Ia in younger environments reduces the total dispersion from 0.142+/-0.008mag to 0.120+/-0.010mag. We show that as environment-ages evolve with redshift, a strong bias, especially on the measurement of the derivative of the dark energy equation of state, can develop. Fortunately, data that measure and correct for this effect using our local specific star formation rate indicator, are likely to be available for many next-generation SN Ia cosmology experiments.
154. Sample of SNe Ia with z<0.25 from SDSS
ID:
ivo://CDS.VizieR/J/ApJ/755/125
Title:
Sample of SNe Ia with z<0.25 from SDSS
Short Name:
J/ApJ/755/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use Type Ia supernovae (SNe Ia) discovered by the Sloan Digital Sky Survey-II SN Survey to search for dependencies between SN Ia properties and the projected distance to the host-galaxy center, using the distance as a proxy for local galaxy properties (local star formation rate, local metallicity, etc.). The sample consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at redshifts below 0.25. The sample is split into two groups depending on the morphology of the host galaxy. We fit light curves using both MLCS2K2 and SALT2, and determine color (A_V_, c) and light-curve shape ({Delta}, x_1_) parameters for each SN Ia, as well as its residual in the Hubble diagram. We then correlate these parameters with both the physical and the normalized distances to the center of the host galaxy and look for trends in the mean values and scatters of these parameters with increasing distance. The most significant (at the 4{sigma} level) finding is that the average fitted A_V_ from MLCS2K2 and c from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies. We also find indications that supernovae (SNe) in elliptical galaxies tend to have narrower light curves if they explode at larger distances, although this may be due to selection effects in our sample. We do not find strong correlations between the residuals of the distance moduli with respect to the Hubble flow and the galactocentric distances, which indicates a limited correlation between SN magnitudes after standardization and local host metallicity.
155. SDSS and CSP ugri photometry of 9 type Ia supernova
ID:
ivo://CDS.VizieR/J/AJ/144/17
Title:
SDSS and CSP ugri photometry of 9 type Ia supernova
Short Name:
J/AJ/144/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
Consistency between Carnegie Supernova Project (CSP) and SDSS-II Supernova Survey ugri measurements has been evaluated by comparing Sloan Digital Sky Survey (SDSS) and CSP photometry for nine spectroscopically confirmed Type Ia supernova observed contemporaneously by both programs. The CSP data were transformed into the SDSS photometric system. Sources of systematic uncertainty have been identified, quantified, and shown to be at or below the 0.023mag level in all bands. When all photometry for a given band is combined, we find average magnitude differences of equal to or less than 0.011mag in ugri, with rms scatter ranging from 0.043 to 0.077mag. The u-band agreement is promising, with the caveat that only four of the nine supernovae are well observed in u and these four exhibit an 0.038mag supernova-to-supernova scatter in this filter.
156. SDSS-II SNe survey: search and follow-up
ID:
ivo://CDS.VizieR/J/AJ/135/348
Title:
SDSS-II SNe survey: search and follow-up
Short Name:
J/AJ/135/348
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Sloan Digital Sky Survey-II Supernova Survey has identified a large number of new transient sources in a 300deg^2^ region along the celestial equator during its first two seasons of a three-season campaign. Multi-band (ugriz) light curves were measured for most of the sources, which include solar system objects, galactic variable stars, active galactic nuclei, supernovae (SNe), and other astronomical transients. The imaging survey is augmented by an extensive spectroscopic follow-up program to identify SNe, measure their redshifts, and study the physical conditions of the explosions and their environment through spectroscopic diagnostics. During the survey, light curves are rapidly evaluated to provide an initial photometric type of the SNe, and a selected sample of sources are targeted for spectroscopic observations. In the first two seasons, 476 sources were selected for spectroscopic observations, of which 403 were identified as SNe. For the type Ia SNe, the main driver for the survey, our photometric typing and targeting efficiency is 90%. Only 6% of the photometric SN Ia candidates were spectroscopically classified as non-SN Ia instead, and the remaining 4% resulted in low signal-to-noise, unclassified spectra.
157. SDSS-II SN Survey: host-galaxy spectral data
ID:
ivo://CDS.VizieR/J/ApJ/821/115
Title:
SDSS-II SN Survey: host-galaxy spectral data
Short Name:
J/ApJ/821/115
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HRs). Our sample consists of 345 photometrically classified or spectroscopically confirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric host-galaxy properties from the SDSS-SNS data release such as host stellar mass and star formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6{sigma} significance of a nonzero linear slope. We also recover correlations between HR and host-galaxy gas-phase metallicity and specific star formation rate as they are reported in the literature. With our large data set, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically confirmed and photometrically classified SNe Ia and comment on the significance of similar combined data sets for future surveys.
158. SDSS-II SN Survey: SNe II-P standardization
ID:
ivo://CDS.VizieR/J/ApJ/708/661
Title:
SDSS-II SN Survey: SNe II-P standardization
Short Name:
J/ApJ/708/661
Date:
21 Oct 2021
Publisher:
CDS
Description:
We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discovered over the three season run of the Sloan Digital Sky Survey-II Supernova Survey. The redshifts of these SNe - 0.027<z<0.144 - cover a range hitherto sparsely sampled in the literature; in particular, our SNe II-P sample contains nearly as many SNe in the Hubble flow (z>0.01) as all of the current literature on the SCM combined. We find that the SDSS SNe have a very small intrinsic I-band dispersion (0.22mag), which can be attributed to selection effects. When the SCM is applied to the combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29mag, larger than the scatter for either set of SNe separately. We show that the standardization cannot be further improved by eliminating SNe with positive plateau decline rates, as proposed in Poznanski et al. (2009ApJ...694.1067P). We thoroughly examine all potential systematic effects and conclude that for the SCM to be useful for cosmology, the methods currently used to determine the FeII velocity at day 50 must be improved, and spectral templates able to encompass the intrinsic variations of Type II-P SNe will be needed.
159. SDSS-II supernovae Ia cosmological analysis
ID:
ivo://CDS.VizieR/J/ApJ/763/88
Title:
SDSS-II supernovae Ia cosmological analysis
Short Name:
J/ApJ/763/88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the cosmological analysis of 752 photometrically classified Type Ia Supernovae (SNe Ia) obtained from the full Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey, supplemented with host-galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey. Our photometric-classification method is based on the SN classification technique of Sako et al. (2011, Cat. J/ApJ/738/162), aided by host-galaxy redshifts (0.05<z<0.55). SuperNova ANAlysis simulations of our methodology estimate that we have an SN Ia classification efficiency of 70.8%, with only 3.9% contamination from core-collapse (non-Ia) SNe. We demonstrate that this level of contamination has no effect on our cosmological constraints. We quantify and correct for our selection effects (e.g., Malmquist bias) using simulations. When fitting to a flat {Lambda}CDM cosmological model, we find that our photometric sample alone gives {Omega}_m_=0.24^+0.07^_-0.05_ (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint statistical constraints on {Omega}_m_ and {Omega}_{Lambda}_, comparable to those derived from the spectroscopically confirmed Three-year Supernova Legacy Survey (SNLS3). Using only our data, the statistics-only result favors an accelerating universe at 99.96% confidence. Assuming a constant wCDM cosmological model, and combining with H_0_, cosmic microwave background, and luminous red galaxy data, we obtain w=-0.96^+0.10^_-0.10_, {Omega}_m_=0.29^+0.02^_-0.02_, and {Omega}_k_=0.00^+0.03^_-0.02_ (statistical errors only), which is competitive with similar spectroscopically confirmed SNe Ia analyses. Overall this comparison is reassuring, considering the lower redshift leverage of the SDSS-II SN sample (z<0.55) and the lack of spectroscopic confirmation used herein. These results demonstrate the potential of photometrically classified SN Ia samples in improving cosmological constraints.
160. SDSS-II supernovae NTT and NOT spectroscopy
ID:
ivo://CDS.VizieR/J/A+A/526/A28
Title:
SDSS-II supernovae NTT and NOT spectroscopy
Short Name:
J/A+A/526/A28
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Sloan Digital Sky Survey II (SDSS-II) Supernova Survey, conducted between 2005 and 2007, was designed to detect a large number of type Ia supernovae around z~0.2, the redshift "gap" between low-z and high-z supernova searches. The survey has provided multi-band (ugriz) photometric lightcurves for variable targets, and supernova candidates were scheduled for spectroscopic observations, primarily to provide supernova classification and accurate redshifts. We present supernova spectra obtained in 2006 and 2007 using the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT). We provide an atlas of supernova spectra in the range z=0.03-0.32 that complements the well-sampled lightcurves from SDSS-II in the forthcoming three-year SDSS supernova cosmology analysis. The sample can, for example, be used for spectral studies of type Ia supernovae, which are critical for understanding potential systematic effects when supernovae are used to determine cosmological distances. The spectra were reduced in a uniform manner, and special care was taken in estimating the uncertainties for the different processing steps. Host-galaxy light was subtracted when possible and the supernova type fitted using the SuperNova IDentification code (SNID). We also present comparisons between spectral and photometric dating using SALT lightcurve fits to the photometry from SDSS-II, as well as the global distribution of our sample in terms of the lightcurve parameters: stretch and colour.

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