Добірка наукової літератури з теми "Supernovae Ia distance scale"

Statistical verification of the “extraordinary” evidence of “acceleration of the expansion of the Universe” due to the “cosmic push” at the redshift interval and at based on data on supernovae of type SN Ia, for which photometric distances were determined, was carried out. The transition from “deceleration” to “acceleration” is considered as a “breakdown” – a change in the structure and parameters of the model of the cosmological distance scale. It is shown that data from different sources do not form a compositionally homogeneous set. The scale model's “misalignment” (discord) was revealed for from a sample of 10 SN Ia obtained in the interval by the High-Z Supernovae Search Team, and for from a sample of 42 SN Ia obtained in the interval by the Supernovae Cosmology Project group. The reason for these “discrepancies” may be an unbalanced and random distribution of SN Ia over the observed range of redshifts with a clearly expressed non-metric character of the scale.

The zero-point of the extragalactic distance scale, defined by about two dozens of nearby, late-type galaxies, has remained nearly unchanged for the last decade, in spite of the advent of new techniques and great efforts. The distances are essentially tied to trigonometric parallax stars and hence independent of the Hyades modulus; they are consistent with RR Lyr stars. The mean zero-point is therefore probably secure to better than 10%.All known secondary distance indicators are still affected by zero-point errors, by problems in the definition of their relation between distance indicator and absolute magnitude (or linear size), and/or by selection bias. The effect of the very important selection bias (Malmquist effect), which causes a seemingly non-linear expansion field, is illustrated by two examples. To test for any true deviations from a linear expansion the Hubble diagram of nearly bias-free first-ranked cluster galaxies and supernovae Ia is shown; this imposes stringent limits on any non-linearity of the Hubble flow within v<5000 km s−1.After freeing the available distances of field galaxies from selection bias and after reducing them to a common zero-point, one finds HO=55–65. Several distance indicators require a best Virgo cluster modulus of (m-M)=31.60, which implies for the Coma cluster (m-M)=35.38 and, with v(Coma)=7217 km s−1, HO=60. Supernovae Ia and first-ranked cluster galaxies out to large distances give HO (global)=53. Thus the evidence from clusters and field galaxies is best satisfied by HO=55; the assigned mean error of ±7 is to indicate a 3σ range of 35<HO<75.Purely physical methods to determine extragalactic distances have modest weight yet; they will contribute eventually much to the determination of HO.If HO were as large as 100, several paradoxa would arise. The Milky Way would have a very high supernova frequency, our Galaxy and M31 would be oversized, the baryon density would fall short to bind clusters, and Friedman universes were excluded.Because all systematic errors have conspired and probably still conspire to measure HO too high, the true value could well be 40. Until new, decisive evidence becomes available, it is suggested for all practical purposes to use HO=50.

AbstractAllan Sandage returned to the distance scale and the calibration of the Hubble constant again and again during his active life, experimenting with different distance indicators. In 1952 his proof of the high luminosity of Cepheids confirmed Baade's revision of the distance scale (H0 ~ 250 km s−1 Mpc−1). During the next 25 years, he lowered the value to 75 and 55. Upon the arrival of the Hubble Space Telescope, he observed Cepheids to calibrate the mean luminosity of nearby Type Ia supernovae (SNe Ia) which, used as standard candles, led to the cosmic value of H0 = 62.3 ± 1.3 ± 5.0 km s−1 Mpc−1. Eventually he turned to the tip of the red giant branch (TRGB) as a very powerful distance indicator. A compilation of 176 TRGB distances yielded a mean, very local value of H0 = 62.9 ± 1.6 km s−1 Mpc−1 and shed light on the streaming velocities in the Local Supercluster. Moreover, TRGB distances are now available for six SNe Ia; if their mean luminosity is applied to distant SNe Ia, one obtains H0 = 64.6 ± 1.6 ± 2.0 km s−1 Mpc−1. The weighted mean of the two independent large-scale calibrations yields H0 = 64.1 km s−1 Mpc−1 within 3.6%.

AbstractType Ia supernovae are very good tools for measuring distances on a cosmic scale. The consensus view is that mass transfer onto a white dwarf in a close binary system leads to a thermonuclear explosion, though the nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star. In the double-degenerate model it is another white dwarf. We study the velocity structure of absorbing material along the line of sight to 35 Type Ia supernovae and find a statistical preference for blueshifted structures, likely arising in gas outflows from the supernova progenitor systems, consistent with a single-degenerate progenitor for a substantial fraction of Type Ia supernovae in nearby spiral galaxies.

ABSTRACT We present a measurement of the Hubble constant (H0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analysed blindly with respect to the cosmological parameters. In a flat Λ cold dark matter (ΛCDM) cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}~\mathrm{km~s^{-1}~Mpc^{-1}}$, a $2.4{{\ \rm per\ cent}}$ precision measurement, in agreement with local measurements of H0 from type Ia supernovae calibrated by the distance ladder, but in 3.1σ tension with Planck observations of the cosmic microwave background (CMB). This method is completely independent of both the supernovae and CMB analyses. A combination of time-delay cosmography and the distance ladder results is in 5.3σ tension with Planck CMB determinations of H0 in flat ΛCDM. We compute Bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. We explore extensions to flat ΛCDM using constraints from time-delay cosmography alone, as well as combinations with other cosmological probes, including CMB observations from Planck, baryon acoustic oscillations, and type Ia supernovae. Time-delay cosmography improves the precision of the other probes, demonstrating the strong complementarity. Allowing for spatial curvature does not resolve the tension with Planck. Using the distance constraints from time-delay cosmography to anchor the type Ia supernova distance scale, we reduce the sensitivity of our H0 inference to cosmological model assumptions. For six different cosmological models, our combined inference on H0 ranges from ∼73 to 78 km s−1 Mpc−1, which is consistent with the local distance ladder constraints.

A linearity test shows H0 to decrease by 7% out to 18 000 km s–1. The value at 10 000 km s–1 is a good approximation to the mean value of H0 over very large scales. The construction of the extragalactic distance scale is discussed. Field galaxies, cluster distances relative to Virgo, and blue supernovae of type Ia yield H0 (cosmic) with increasing weight; they give consistently H0 = 57 ± 7 (external error). This value is supported by purely physical distance determinations (SZ effect, gravitational lenses, MWB fluctuations). Arguments for H0 > 70 are discussed and shown to be flawed.

The Hubble diagram (HD) is a plot that contains a luminous distance modulus presented with respect to the redshift. The distance modulus–redshift relation of the most well-known “standard candles”, the type Ia supernovae (SN), is a crucial tool in cosmological model testing. In this work, we use the SN Ia data from the Pantheon catalogue to calibrate the Swift long gamma-ray bursts (LGRBs) as “standard candles” via the Amati relation. Thus, we expand the HD from supernovae to the area of the Swift LGRBs up to z∼8. To improve the quality of estimation of the parameters and their errors, we implement the Monte-Carlo uncertainty propagation method. We also compare the results of estimation of the Amati parameters calibrated by the SN Ia, and by the standard ΛCDM model and find no statistically significant distinction between them. Although the size of our LGRB sample is relatively small and the errors are high, we find this approach of expanding the cosmological distance scale promising for future cosmological tests.

AbstractThe nature and timescales behind the growth of the white dwarf toward the Chandrasekhar mass are not known. The two leading competing scenarios for Type Ia supernovae (SNe Ia) are accretion from a companion [single degenerate (SD)] or merger with another white dwarf [double degenerate (DD)]. Measurement of the SNe Ia delay time distribution could distinguish between these scenarios. Possibly both channels operate, on short (SD) and long (DD) time scales. A supernova search in parallel with our Cluster Lensing And Supernova survey with Hubble extends the Hubble diagram of SNe Ia to z > 1.5, probing progenitor evolution and testing the constancy of dark energy (DE) with time. We use HST ACS to detect SNe Ia at 1 < z < 1.5 and WFC3 to find SNe Ia at 1.5 < z < 2.5, thus providing constraints for the variation in the DE equation of state. This redshift epoch provides the unique chance to test SNe Ia distance measurements for the deleterious effects of evolution independent of our ignorance of dark energy. Our program provides the first measurement of the SNe Ia rate at z ~ 2.

This thesis studies the relationship between type Ia supernovae (SNe Ia) and their host galaxies. The sample consists of 527 SNe Ia with redshift z<0.09 discovered by the Palomar Transient Factory (PTF). We obtained high-quality photometric and spectroscopic data of the host galaxies and determined their stellar mass M_stellar, star formation rate (SFR), gas-phase/stellar metallicity, stellar age and SN offset. In the first part of the analysis, we compare the SN Ia photometric properties to the host parameters. Strong correlations between the SN Ia light-curve width (stretch) and the host age/mass/metallicity are found: fainter, faster-declining events tend to be hosted by older/massive/metal-rich galaxies. There is also some evidence that redder SNe Ia explode in higher metallicity galaxies. SNe Ia in higher-mass/metallicity galaxies also appear brighter after stretch/colour corrections than their counterparts in lower mass hosts, and the stronger correlation is with gas-phase metallicity suggesting this may be the more important variable. We also compare the host stellar mass distribution to that in galaxy targeted SN surveys and the high-redshift untargeted Supernova Legacy Survey (SNLS). The difference between each stellar mass distribution can be explained by an evolution in the galaxy stellar mass function, coupled with a SN delay-time distribution proportional to t^-1. Finally, we found no significant difference in the mass-metallicity relation of our SN Ia hosts compared to field galaxies, suggesting any metallicity effect on the SN Ia rate is small. In the second part of the analysis, we compare the SN spectral features to the host parameters. We find that SNe Ia with higher Si ii λ6355 velocities tend to explode in more massive galaxies. We study the strength of the high-velocity component of the Ca ii NIR absorption, and find that SNe Ia with a stronger high-velocity component are preferentially hosted by galaxies with a low M_stellar, a blue colour, and a high SFR, and are therefore likely to arise from the youngest progenitor systems. When combined with other studies, our results support the scenario that these high-velocity features are related to an interaction between the SN ejecta and a circumstellar medium (CSM) local to the SN.

Advancements in the field of cosmology over the past decades have dramatically increased our knowledge of the origin and evolution of the Universe, with increasing precision on measured cosmological parameters. The best model describing the evolution of our Universe is the Lambda Cold Dark Matter ($Lambda$CDM) model. While this model fits numerous observations, some tensions with respect to it have been highlighted. One of the most intriguing is the Hubble tension: a disagreement of $sim 5 sigma$ between the $H_0$ values measured at early- and late-time Universe. It is yet unclear whether this tension arises from subtle systematic uncertainties, or we are observing interesting new physics. Furthermore, the force behind the accelerated expansion of the Universe, called as Dark energy (DE), remains almost a mystery with little to no understanding about its nature and evolution. This thesis aims at using different types of astrophysical transients as cosmological probes. I work on advancing the standardization techniques of three types of transients currently detectable at different redshift scales -- supernovae Type Ia (SNe Ia, $z lesssim 1.2$), superluminous supernovae (SLSN, $z lesssim 4$), and kilonovae (KNe, $z lesssim 0.1$). I use these transients to estimate the Hubble constant and investigate the possibility to standardise their luminosities. The new methodologies developed here are particularly promising to address the Hubble tension problem and to constrain the DE evolution in the next decade with the advent of new instruments, such as the Vera Rubin Observatory, Roman Space Telescope, and the James Webb Space Telescope. For SNe Ia, I develop an innovative method to calibrate their distance scale based on the surface brightness fluctuations (SBF) distances of their host galaxies. I calibrate SN luminosity using a sample of 24 anchor SNe Ia hosted in galaxies with SBF distance measurements. With a Hubble flow sample of $sim 100$ SNe Ia, I estimate $H_0 = 70.50 pm 2.37 (stat) pm 3.38 (sys)$,si{km.s^{-1}.Mpc^{-1}}. This value sits midway in the range defined by the Hubble tension, and is consistent with early and the late Universe $H_0$ measurements within the errors. This work also examines the dependence of SNe Ia luminosity on its host galaxy properties in a comparative study involving different types of host galaxies. Our results point to possible intrinsic differences among the luminosity of SNe hosted in distinct types of environments. This dependence is particularly interesting for estimating the cosmological parameters, and to unveil the nature and environment of SN Ia explosion, which remains largely unknown. Additionally, I explore the use of SLSNe type I as a cosmological probe for the very high redshift Universe. These sources can be detected in their rest frame ultraviolet (UV) up to $z sim 7$ using optical and infrared telescopes. I evaluate their peak magnitude correlations with the light curve properties in the rest frame UV using a sample of 22 high redshift ($ 1 lesssim z lesssim 3.2$) SLSNe-I observed to date. I find a linear correlation between the UV peak absolute magnitudes and rise time, having an intrinsic scatter ($sigma_{int}$) of 0.29. Interestingly, this correlation is further tightened ($sigma_{int} approx 0.2$) eliminating those SLSNe which show a pre-peak bump. This result hints at the possibility that the ``Bumpy" SLSNe could belong to a different population. I also observe weak correlations between the peak luminosity and color indices of SLSNe light curves. No relationship is found between peak magnitudes in the UV band and the decline rate ($Delta M_{15}$) of the light curves in contrast to what is typically found in optical band. The correlations found here are promising and encourage further exploration into the use of SLSNe as high redshift cosmological probes. Finally, I contribute to the investigation of the use of Kilonovae as distance indicators in the local Universe. KNe enable to make an independent measurement of the $H_0$. I apply techniques similar to SNe Ia standardisation with two different sets of KNe properties; measured quantities (decline rate and color) and inferred ejecta quantities (mass, velocity and composition). Considering the only confirmed kilonova, AT2017gfo, associated with GW170817, I standardize it correlating its luminosity with the measured and the inferred quantities. We evaluate $H_0 = SI[parse-numbers = false, number-math-rm = ensuremath]{109^{+49}_{-35}}{km.s^{-1}.Mpc^{-1}}$ for the measured analysis, and $H_0 = SI[parse-numbers = false, number-math-rm = ensuremath]{85^{+22}_{-17}}{km.s^{-1}.Mpc^{-1}}$ and $H_0 = SI[parse-numbers = false, number-math-rm = ensuremath]{79^{+23}_{-15}}{km.s^{-1}.Mpc^{-1}}$ for the two inferred analyses. While waiting for larger samples, this work provides a proof-of-concept for a valuable method to obtain an independent constraint on $H_0$. In summary, my work gives new methodologies to constrain the cosmological parameters and understand astrophysical systematics using different types of transients. The analysis of multi-filter observations at different redshift scales enable us to evaluate the $H_0$ with a complementary set of astrophysical transients. For SN Ia, I demonstrate the potential of the use of SBF measurements to calibrate SN luminosity relations. My results point to an interesting astrophysical difference among SN Ia in different type of galaxies, which could reduce the $H_0$ tension and give information about the progenitor/environment of SN Ia. For SLSNe and KNe, my work inserts in the pioneering works exploring these sources as possible standard candles, with the former at high redshift to constrain dark energy evolution, and the latter as a new independent local probe for $H_0$. The transients explored here have the potential to probe local to $z gtrsim 10$ Universe, back to first generations of stars and well into the deceleration epoch. This work lays the framework for powerful cosmological tools in the upcoming years when larger data samples and larger distances will be accessible with the advent of new instruments.

La misura delle distanze in astrofisica è una materia complessa ma essenziale per la comprensione dei fenomeni astronomici. Nei secoli gli astronomi hanno ideato diversi metodi per ottenere questa importante misura. Nel loro insieme questi metodi formano una scala delle distanze, dove ogni gradino della scala è calibrato a partire dal gradino precedente. I metodi per misurare le distanze in astrofisica sono raggruppati in tre categorie: i metodi geometrici, basati sul concetto di parallasse, che possono essere usati solo all'interno della Via Lattea; gli indicatori primari, i quali sono basati sul concetto di candele standard, ovvero oggetti di cui si conosce a priori la magnitudine assoluta, utili per determinare distanze fino a 300 Mpc; infine, gli indicatori secondari, calibrati a partire dagli indicatori primari, che sono usati per ottenere le distanze di oggetti fino ai confini dell'Universo conosciuto. In questa tesi di laurea vengono presi in esame i diversi metodi: la parallasse stellare annua, il fit di sequenza principale, le candele standard e in particolare le Cefeidi, le stelle RR Lyrae e le supernovae Ia, il piano fondamentale, la legge di Tully-Fisher, la legge di Hubble. Infine, dopo aver parlato delle galassie più lontane osservate dal telescopio spaziale Hubble, una breve sezione è dedicata a cenni riguardo al problema delle distanze in cosmologia.

In questo elaborato vengono descritti i principali metodi per il calcolo delle distanze in astrofisica. Viene trattato il fenomeno della parallasse, il funzionamento e alcuni tipi di stelle variabili oltre alle supernove di tipo thermonuclear. Infine sono brevemente discussi alcuni indicatori secondari: le relazioni di Faber-Jackson, Tully-Fisher e la legge di Hubble.

Con i vari metodi utilizzati per calcolare le distanze dei corpi celesti è stata creata una vera e propria scala delle distanze astrofisiche, in cui ogni gradino funge da calibro per quello successivo. Infatti, a partire dalla misura delle distanze all'interno del sistema solare e delle stelle vicine, è stato possibile calcolare le distanze delle galassie vicine e successivamente di quelle più lontane, potendo, infine, determinare il valore della costante di Hubble per la stima delle dimensioni dell'Universo.

In astrofisica la determinazione delle distanze ha sempre assunto un ruolo molto importante, poiché essa consente una più accurata comprensione della struttura e dell’evoluzione dell’universo in cui ci troviamo. Ci sono molti metodi che possono essere seguiti, a seconda degli oggetti di studio e dello scopo della ricerca. I metodi diretti (geometrici), utilizzabili solo nei dintorni del Sistema Solare, permettono di calibrare quelli indiretti (indicatori primari e secondari), i quali sono utilizzabili a distanze molto maggiori. Ogni metodo consente di accurare il successivo, creando così un meccanismo di misura chiamato scala delle distanze cosmiche, la quale ha come fine ultimo la calibrazione della legge di Hubble, di fondamentale importanza in cosmologia.

On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-141p just similar to 2 days after first light using a global array of 14 cm diameter telescopes. ASASSN-141p went on to become a bright supernova (V = 11.94 mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-141p for more than 100 days. We find that ASASSN-141p had a broad light curve (Delta m(15) (B) = 0.80 +/- 0.05), a B-band maximum at 2457015.82 +/- 0.03, a rise time of 16.941(-0.10)(+0.11) days, and moderate host-galaxy extinction (E (B - V)host = 0.33 +/- 0.06). Using ASASSN-141p, we derive a distance modulus for NGC 4666 of mu = 30.8 +/- 0.2, corresponding to a distance of 14.7 +/- 1.5 Mpc. However, adding ASASSN-141p to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34 RG(circle dot).

Aquesta tesi engloba el treball fet durant els ultims quatre anys com a estudiant de doctorat a l’Institut de Física d’Altes Energies (IFAE), emmarcat dins de la col·labaració Sloan Digital Sky Survey II Supernova (SDSS-II/SNe) Survey. Al primer capítol (§1) s’introdueixen els principals conceptes del Model Estàndar de Cosmologia, presentant els seus orígens, les propietats dels seus continguts, i les mesures de distància i brillantor. També es reconstrueix l’història de l’univers des del Big Bang i es resumeixen alguns dels descobriments més excitants que han confirmat les prediccions del Model Estàndar. Seguidament (§2), es dona una explicació detallada de les supernoves (SNe), incloenthi el mecanisme físic que dóna lloc a les explosions, les diferències entre els diferents tipus, i la seva classificació espectral. També es descriuen les propietats fotomètriques i espectroscòpiques de les supernoves de tipus Ia. Tot seguit, es resumeixen les mesures del ritme d’explosions, les propietats de les gal·làxies on resideixen les supernoves, i el seu ús en Cosmologia a través del diagrama de Hubble. Al següent capítol, (§3) es descriu la col·laboració SDSS-II/SNe Survey, una extensió de tres anys (2005-2007) del projecte Sloan (SDSS) que ha detectat i mesurat corbes de llum de centenars de supernoves tot escanejant el cel en repetides ocasions. Vam contribuir al seguiment espectroscòpic de les supernoves de SDSS-II/SNe, obtenint 23 espectres de supernoves durant 4 nits d’Octubre i Novembre (5-6 Oct. i 4-5 Nov.) del 2007, utilitzant el Telescopio Nazionale Galileo (TNG) situat a l’Observatorio del Roque de Los Muchachos (ORM) a l’illa de La Palma. Al capítol §4 es descriu tot el procés de reducció de les dades, des de l’adquisició de les imatges fins als espectres calibrats en flux i longitud d’ona. A continuació de la reducció dels espectres, al capítol §5, s’analitza una de les supernoves de tipus Ia menys lluminoses mai conegudes, la peculiar 2007qd, per la qual vam mesurar el primer espectre. Les propietats observades de la 2007qd la situen a la subclasse anomenada 2002cx, com a membre intermig entre la 2002cx i la 2008ha, enllaçant aquetes. Es presenten les observacions espectroscòpiques i fotomètriques de la supernova 2007qd i es comparen les seves propietats peculiars amb un ventall d’altres supernoves. Aquest anàlisi va ser publicat a McClelland et al. (2010). Al capítol §6, s’utilitzen les supernoves Ia descobertes pel SDSS-II/SNe Survey durant els tres anys d’activitat, per buscar dependències entre les propietats fotomètriques de les supernoves Ia i la projecció de la distància fins al centre de la gal·làxia on resideixen, utilitzant la distància com a aproximació a les propietats locals de les gal·làxies (ritme de creació d’estrelles, metalicitat local, etc.). Trobem que l’excés de color de les supernoves, parametritzat per AV a MLCS2k2 i per c a SALT2 decreix amb la distància projectada, en particular per les gal·làxies espirals. A més, amb menys significància, també es troba que l’amplada de la corba de llum, obtinguda amb MLCS2k2, està correlacionada amb la separació entre la supernova i el centre de la gal·làxia per les el·líptiques, així les supernoves amb corbes de llum més estretes, per tant menys lluminoses, s’observen més aviat a més distància del centre gal·làctic. Aquest anàlisi va ser presentat a la conferència Supernovae and their Host Galaxies que es va fer al Juny del 2011 a Sydney, i serà publicat a Galbany et al. (2011). Finalment, al capítol §7, es resumeix i es donen les conclusions d’aquesta tesi.<br>Esta tesis engloba el trabajo realizado durante los últimos cuatro años como estudiante de doctorado en el Institut de Física d’Altes Energies (IFAE), enmarcardo en la colabaración Sloan Digital Sky Survey II Supernova (SDSS-II/SNe) Survey. En el primer capítulo (§1) se introducen los principales conceptos del Modelo Estándar de Cosmología, presentando sus orígenes, las propiedades de sus contenidos, y las medidas de distancia y brillo. También se reconstruyen la historia del universo desde el Big Bang y se resumen algunos de los descubrimientos más excitantes que han confirmado las predicciones del Modelo Estándar. Seguidamente (§2), se da una explicación detallada de las supernovas (SNe), incluyendo el mecanismo físico que da lugar a las explosiones, las diferencias entre los diferentes tipos, y su clasificación espectral. También se describen las propiedades fotomètricas y espectroscópicas de las supernovas de tipo Ia. A continuación, se resumen las medidas del ritmo de explosión, las propiedades de las galaxias donde residen las supernovas, y su uso en Cosmología a través del diagrama de Hubble. En el siguiente capítulo, (§3) se describe SDSS-II/SNe Survey, una extensión de tres años (2005-2007) del proyecto Sloan (SDSS) que ha detectado y medido curvas de luz para centenares de supernovas a través de escanear el cielo en repetidas ocasiones. Como parte del seguimiento espectroscópico de las supernova de SDSS-II/SNe, contribuímos obteniendo 23 espectros de supernovas durante 4 noches de Octubre y Noviembre (5-6 Oct. y 4-5 Nov.) del 2007, utilizando el Telescopio Nazionale Galileo (TNG) situado en el Observatorio del Roque de Los Muchachos (ORM) en La Palma. En el capítulo §4 se describe toda la reducción de datos, desde la adquisición de las imágenes hasta los espectros calibrados en flujo y longitud de onda. Siguiendo la reducción de los espectros, en el capítulo §5, se describe una de las supernovas de tipo Ia menos luminosa jamàs conocida, la peculiar 2007qd, para la cual medimos el primer espectro. Las propiedades observadas de la 2007qd la sitúan en la subclase llamada 2002cx, como miembro intermedio entre las supernovas 2002cx y 2008ha, enlazándolas. Se presentan las observaciones espectroscópicas y fotométricas de la supernova 2007qd y se comparan su propiedades con un conjunto de otras supernovas. Éste análisis fue publicado en McClelland et al. (2010). En el capítulo §6, se utilizan las supernovas Ia descubiertas por SDSS-II/SNe Survey durante los tres años de actividad, para buscar dependencias entre las propiedades fotométricas de las supernovas Ia y la proyección de la distancia hasta el centro de la galaxia donde residen, utilizando la distancia como aproximación a las propiedades locales de las galaxias (ritmo de creación de estrellas, metalicidad local, etc.). Encontramos que el exceso de color de las supernovas, parametrizado por AV en MLCS2k2 y por c en SALT2 decrece con la distancia, en particular para las galaxias espirales. Además, y con menos significancia, también se encuentra que la amplitud de la curva de luz, obtenida con MLCS2k2, está correlacionada con la separación entre la supernova y el centro de la galaxia para las galaxias elípticas, así las supernovas con curvas de luz más estrechas, y menos luminosas, se observan a más distancia del centro galactico. Este análisis fue presentado en la conferencia Supernovae and their Host Galaxies que tuvo lugar en Junio del 2011 en Sydney, y serà publicado en Galbany et al. (2011). Finalmente, en §7, se resume y se presentan las conclusiones de esta tesis.<br>This thesis comprises the work I have been doing during the last four years at Institut de Física d’Altes Energies (IFAE) as a PhD student, and has to be understood within the context of the Sloan Digital Sky Survey II Supernova (SDSS-II/SNe) survey. The content of this thesis is ordered as follows. In the next Chapter (§1) I introduce the main concepts of the Standard Model of Cosmology, presenting the origins, the properties of its contents, and the distance and the brightness measurements. I also reconstruct the history of universe since the Big Bang and summarize some of the most exciting discoveries that have confirmed the Standard Model predictions. In §2, a detailed explanation of supernovae (SNe) is given, including the physical mechanism that accounts for their explosions, the differences among the several types of SNe, and their spectral classification. We also describe the spectroscopic and photometric properties of Type-Ia SNe. After that, we review the SNe rate of the explosion measurements, the properties of their host galaxies, and their use in Cosmology through the Hubble diagram. After that, in §3, I describe the SDSS-II/SNe survey, a three-year (2005-2007) extension of SDSS of which I am an external collaborator, which has detected and measured light-curves for several hundred supernovae through repeat scans of the sky. As a part of the spectroscopic follow-up of the SDSS-II/SNe candidates, we contributed to the project taking spectra of 23 SNe during four nights in October and November (5-6 Oct. and 4-5 Nov.) of 2007 using the Telescopio Nazionale Galileo (TNG) located at the Observatorio del Roque de Los Muchachos (ORM) in La Palma. In §4, the whole reduction procedure, from the acquisition of the raw data by the telescope camera to the final flux-calibrated spectra, is described. Following the spectra reduction, in §5, I describe one of the most subluminous type-Ia events known, the peculiar 2007qd supernova, for which we took the first spectrum. The observed properties of 2007qd place it in the 2002cx subclass of supernovae, specifically as a member intermediate to 2002cx and 2008ha, linking these objects. We present the photometric and spectroscopic observations of 2007qd and compare its unique properties with a range of other SNe. This work was compiled and published in McClelland et al. (2010). Then, in §6, the three-year sample of Type Ia supernovae (SNe Ia) discovered by the SDSS-II/SNe Survey is used to look for dependencies between photometric 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.). We find that the excess color of the SN, parametrized by AV in MLCS2k2 and by c in SALT2 decreases with the projected distance, in particular for spiral galaxies. At a lower significance we find that the light-curve width, as obtained from MLCS2k2 , is correlated with the SN-galaxy separation for elliptical hosts, so that SNe Ia with narrower light-curves, hence dimmer, are more commonly observed at large distances from the host galaxy core. This analysis was presented in the Supernovae and their Host Galaxies conference which was held at Sydney, Australia in June 2011, and will be published in Galbany et al. (2011). Finally, in §7 we give a summary and the conclusions of this thesis.

À la fin des années 90, deux équipes indépendantes ont montré l’expansion accélérée de notre Univers, à partir des mesures de distances de supernovas de type Ia (SNIa). Depuis, une des priorités de la cosmologie moderne est de caractériser ce phénomène et d’en comprendre ses fondements. L’amélioration des mesures de distance réalisées à partir des SNIa est une technique majeure permettant de mieux caractériser l’accélération et donc de déterminer la nature physique de ce phénomène. Ce document développe un nouveau modèle de distribution spectrale en énergie de SNIa nommé le Supernova Useful Generator And Reconstructor (SUGAR) permettant d’améliorer les mesures des distances. Ce modèle est construit à partir des propriétés spectrales des SNIa et des données spectrophotométriques de la collaboration The Nearby Supernova Factory. L’avancée principale, proposée dans SUGAR, réside dans l’ajout de deux paramètres supplémentaires pour caractériser la variabilité des SNIa. Le premier dépend des propriétés des vitesses des éjectas des SNIa, le deuxième dépend de leurs raies du calcium. L’ajout de ces paramètres, ainsi que la grande qualité des données de la collaboration the Nearby Supernova Factory font de SUGAR le meilleur modèle qui existe pour décrire la distribution spectrale en énergie des SNIa et améliore les mesures des distances de l’ordre de 15% par rapport à la méthode usuelle. Les performances de ce modèle en font un excellent candidat pour préparer les expériences futures comme LSST ou WFIRST. Par ailleurs, ce document présente une analyse sur l’effet de l’appartenance d’une SNIa à un amas de galaxies sur sa mesure de distance. Les galaxies d’un amas possèdent une vitesse propre largement supérieure à la valeur supposée lors de la mesure des distances avec les SNIa. Ceci a pour conséquence d’introduire une source d’erreur systématique sur la mesure de distance. Le fait de ne pas prendre en compte cet effet peut dégrader la mesure de distance de l’ordre de 2,5% pour les SNIa appartenant à un amas. Cette analyse à été réalisée en utilisant les données de la collaboration the Nearby Supernova Factory et des catalogues public d’amas de galaxies<br>At the end of the 90s, two independent teams showed, based on distance measurements of type Ia supernovæ (SNIa), that expansion of our Universe is accelerating. Since then, one of the priorities of modern cosmology is to characterize this phenomenon and to understand its nature. The improvement of distance measurements of SNIa is one technique to improve the constraints on acceleration and to determine the physical nature of it. This document develops a new SNIa spectral energy distribution model, called the Supernova Useful Generator and Reconstructor (SUGAR), which improves distance measurement. This model is constructed from SNIa spectral properties and spectrophotometric data from The Nearby Supernova Factory collaboration. The main advancement proposed in SUGAR is the addition of two additional parameters to characterize the SNIa variability. The first depends on the properties of SNIa ejecta velocity, the second depends on their calcium lines. The addition of these parameters as well as the high quality of the data of The Nearby Supernova Factory collaboration make SUGAR the best model available to describe the spectral energy distribution of SNIa and improves distances measurements of the order of 15 % relative to the usual method. The performance of this model makes it an excellent candidate for preparing future experiments like LSST or WFIRST. In addition, this document presents an analysis of the effect of SNIa belonging to a galaxy cluster on its distance measurement. Galaxies of a cluster have a peculiar velocity much higher than the assumed value when measuring distances with SNIa. This has the effect of introducing a systematic error into the distance measurement. Failure to take into account this effect may degrade the distance measurement by 2.5% for SNIa belonging to a cluster. This analysis was carried out using data from the collaboration of the Nearby Supernova Factory and public catalogs of galaxy cluster

The field of physical cosmology has advanced greatly in the last few decades. In this time, a holistic `concordance' model of our Universe has been pieced together: an isotropic and homogeneous Universe which started very small, went through a brief inflationary period, and obeys General Relativity. Approximately a third of its energy content can be attributed to matter (mostly cold dark matter, with some baryonic), and the remainder to `dark' energy, which appears to be a cosmological constant, tied to spacetime itself. Together, these components are referred to as the LambdaCDM model. Type Ia supernovae (SNe Ia) have been instrumental in reaching this understanding, playing a pivotal role in the late 1990s by signalling the Universe's accelerated expansion. Since then, SNe Ia and the other probes (baryon acoustic oscillations, weak lensing, and clustering) have been employed to improve constraints on the quantities that parametrise LambdaCDM, and the equation-of-state parameter w for dark energy. These efforts have converged in the Dark Energy Survey (2013-2018), which coordinates these probes. The paradigm for cosmology now is to diminish systematic errors to obtain precise measurements of cosmological parameters through observations far into the distant past. More locally, the Hubble constant H_0 determines the expansion rate of the Universe at present; this normalises its distance scale. In the past several years, the precise value of H_0 has come into contention, with a significant discrepancy between results determined from a local distance ladder (with SNe Ia at the top), and those inferred from observations of the early Universe assuming the cosmological models that drive its expansion history. Taken at face value, this discrepancy could signal systematic errors in either measurement, or inaccurate assumptions about the model. The efforts in this thesis use SNe Ia to address questions at both ends of the Universe's expansion history - the Hubble constant locally, and dark energy at higher redshifts - using the current best methods to account for the statistical and systematic terms which affect supernovae. These methods, were developed by the Supernova Legacy Survey (SNLS) and subsequent Joint Lightcurve Analysis (JLA), rely on covariance matrices to encapsulate correlated uncertainties in all lightcurve parameters, which are then propagated through probabilistic Bayesian parameter estimation methods to uncertainties in cosmological parameters. In the works contained within this thesis, I have developed a framework for performing precise cosmological analysis of SNe Ia samples, including using covariance matrices to quantify systematic terms. I have applied to the aforementioned pertinent questions: the value of the Hubble constant and the nature of dark energy, using the datasets in SH0ES (Riess et al. 2011) and intermediate Dark Energy Survey supernova data.

As we take a longer-term view of our future, a host of astrophysical processes are waiting to unfold as the Earth, the Sun, the Galaxy, and the Universe grow increasingly older. The basic astronomical parameters that describe our universe have now been measured with compelling precision. Recent observations of the cosmic microwave background radiation show that the spatial geometry of our universe is flat (Spergel et al., 2003). Independent measurements of the red-shift versus distance relation using Type Ia supernovae indicate that the universe is accelerating and apparently contains a substantial component of dark vacuum energy (Garnavich et al., 1998; Perlmutter et al., 1999; Riess et al., 1998). This newly consolidated cosmological model represents an important milestone in our understanding of the cosmos. With the cosmological parameters relatively well known, the future evolution of our universe can now be predicted with some degree of confidence (Adams and Laughlin, 1997). Our best astronomical data imply that our universe will expand forever or at least live long enough for a diverse collection of astronomical events to play themselves out. Other chapters in this book have discussed some sources of cosmic intervention that can affect life on our planet, including asteroid and comet impacts (Chapter 11, this volume) and nearby supernova explosions with their accompanying gamma-rays (Chapter 12, this volume). In the longerterm future, the chances of these types of catastrophic events will increase. In addition, taking an even longer-term view, we find that even more fantastic events could happen in our cosmological future. This chapter outlines some of the astrophysical events that can affect life, on our planet and perhaps elsewhere, over extremely long time scales, including those that vastly exceed the current age of the universe. These projections are based on our current understanding of astronomy and the laws of physics, which offer a firm and developing framework for understanding the future of the physical universe (this topic is sometimes called Physical Eschatology – see the review of ćirković, 2003). Notice that as we delve deeper into the future, the uncertainties of our projections must necessarily grow.

The study of the accelerating expansion of the Universe is possible because of the standardization procedure of Type IaSupernovae (SNe). However, we still observe the residual dispersion on the Hubble diagram that could be related toenvironmental effects and unknown peculiar velocities of SNe Ia. In this analysis, we continue to study the peculiar velocitiesof SNe inside galaxy clusters and their influence on distance modulus measurements. We perform the fit for a low redshiftz ≤ 0.15 sample with a fixed value of Ω m for C11 and G10 models and calculate wRM S value to estimate the impactof peculiar velocity effect. We get the wRM S = 0.1643 for the C11 sample with SNe Ia in clusters if we use the galaxycluster z cl instead of the host galaxy z host , wRM S = 0.1696 in the original data (for G10 wRM S = 0.1617 and wRM S =0.1643, respectively). The results show the decreasing of residual dispersion on the Hubble diagram. Therefore, this effectis considerable for supernovae in clusters and should be taken into account in future cosmological analyses.