Download or read book The Host Galaxies of Type Ia Supernovae and the Future of Spectroscopic Type Ia Cosmology written by Elizabeth Samantha Swann and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Improving Type Ia Supernova Standard Candle Cosmology Measurements Using Observations of Early Type Host Galaxies written by Joshua Evan Meyers and published by . This book was released on 2012 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: Type Ia supernovae (SNe Ia) are the current standard-bearers for dark energy but face several hurdles for their continued success in future large surveys. For example, spectroscopic classification of the myriad SNe soon to be discovered will not be possible, and systematics from uncertainties in dust corrections and the evolution of SN demographics and/or empirical calibrations used to standardize SNe Ia must be studied. Through the identification of low-dust host galaxies and through increased understanding of both the SN -- progenitor connections and empirical calibrations, host galaxy information may offer opportunities to improve the cosmological utility of SNe Ia. The first half of this thesis analyzes the sample of SNe~Ia discovered by the Hubble Space Telescope (HST) Cluster Supernova Survey augmented with {\it HST}-observed SNe~Ia in the Great Observatories Origins Deep Survey (GOODS) fields. Correlations between properties of SNe and their host galaxies are examined at high redshift. Using galaxy color and quantitative morphology to determine the red sequence in 25 clusters, a model is developed to distinguish passively evolving early-type galaxies from star-forming galaxies in both clusters and the field. With this approach, 6 early-type cluster member hosts and 11 SN~Ia early-type field hosts are identified. For the first time at z>0.9, the correlation between host galaxy type and the rise and fall time of SN~Ia light curves is confirmed. The relatively simple spectral energy distributions of early-type galaxies also enables stellar mass measurements for these hosts. In combination with literature host mass measurements, these measurements are used to show, at z>0.9, a hint of the correlation between host mass and Hubble residuals reported at lower redshift. By simultaneously fitting cluster galaxy formation histories and dust content to the scatter of the cluster red sequences, it is shown that dust reddening of early-type cluster SN hosts is likely less than E(B-V)
Download or read book Thermonuclear Supernovae written by P. Ruiz-Lapuente and published by Springer Science & Business Media. This book was released on 1997 with total page 920 pages. Available in PDF, EPUB and Kindle. Book excerpt: All theoretical and observational topics relevant to the understanding of the thermonuclear (Type Ia) supernova phenomenon are thoroughly and consistently reviewed by a panel including the foremost experts in the field. The book covers all aspects, ranging from the observations of SNe Ia at all stages and all wavelengths to the 2D and 3D modelling of thermonuclear flames in very dense plasmas. Scenarios for close binary evolution leading to SNe Ia are discussed. Particular emphasis is placed on the homogeneity vs. diversity of SNe Ia and on their use as standard candles to measure cosmological parameters. The book reflects the recent and very significant progress made in both the modelling of the explosions and in the observational field.
Download or read book A Quantitative Spectroscopic Comparison of Distant and Nearby Type Ia Supernovae Tests for Homogeneity and Implications for Cosmology written by and published by . This book was released on 2006 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents quantitative analysis of spectra from 130 high-redshift (Zmedian = 0.63) Type Ia supernovae. This extensive set of distant SNe is comprised of a primary set of objects observed at the Gemini telescopes for the ongoing Supernova Legacy Survey (SNLS), a secondary set observed at the Very Large Telescope for the SNLS, and a tertiary set of high-z spectra from the literature. All work on the reduction and identification of the spectra in the primary data set (including spectra from a total of 124 SNe candidates observed between August 2003 and May 2006) was completed by the author. Rest-frame equivalent width and Call H & K ejection velocity measurements are made on these distant SNe Ia spectra, with methods tailored to the specific considerations of high-z data. The results from this analysis were compared to corresponding measurements from a set of 167 SNe Ia spectra from 24 nearby objects from the literature to investigate the homogeneity of SNe Ia across a wide range of redshifts (0.001 less than or equal z less than or equal 1.0). This comparison provides a quantitative indicator for possible evolutionary effects in the population of high-z SNe surveyed for cosmology. A statistical comparison of the spectroscopic features of the high-z SNe and the trends exhibited in the nearby objects finds a less than 2 sigma difference for all of the measurements considered here. These results also indicate that there are no systematic changes due to redshift in this SNe sample. The dependence of SNe Ia spectroscopic properties on host galaxy type is also investigated and found to be similar for nearby and distant objects. These results are discussed briefly in the context of the physical understanding and cosmological implications of SNe Ia. A new correlation between SNe Ia peak magnitude and the strength of a specific SiII absorption feature (near 4000 A, measured within +/- 7 days of maximum light) is also presented.
Download or read book Verifying the Cosmological Utility of Type Ia Supernovae written by and published by . This book was released on 2008 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: We analyze the mean rest-frame ultraviolet (UV) spectrum of Type Ia Supernovae (SNe) and its dispersion using high signal-to-noise ratio Keck-I/LRIS-B spectroscopy for a sample of 36 events at intermediate redshift (z=0.5) discovered by the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). We introduce a new method for removing host galaxy contamination in our spectra, exploiting the comprehensive photometric coverage of the SNLS SNe and their host galaxies, thereby providing the first quantitative view of the UV spectral properties of a large sample of distant SNe Ia. Although the mean SN Ia spectrum has not evolved significantly over the past 40percent of cosmic history, precise evolutionary constraints are limited by the absence of a comparable sample of high-quality local spectra. The mean UV spectrum of our z~;;=0.5 SNe Ia and its dispersion is tabulated for use in future applications. Within the high-redshift sample, we discover significant UV spectral variations and exclude dust extinction as the primary cause by examining trends with the optical SN color. Although progenitor metallicity may drive some of these trends, the variations we see are much larger than predicted in recent models and do not follow expected patterns. An interesting new result is a variation seen in the wavelength of selected UV features with phase. We also demonstrate systematic differences in the SN Ia spectral features with SN light curve width in both the UV and the optical. We show that these intrinsic variations could represent a statistical limitation in the future use of high-redshift SNe Ia for precision cosmology. We conclude that further detailed studies are needed, both locally and at moderate redshift where the rest-frame UV can be studied precisely, in order that future missions can confidently be planned to fully exploit SNe Ia as cosmological probes.
Download or read book Host Galaxies of Type Ia Supernovae from the Nearby Supernova Factory written by Michael Joseph Childress and published by . This book was released on 2011 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Type Ia Supernovae (SNe Ia) are excellent distance indicators, yet the full details of the underlying physical mechanism giving rise to these dramatic stellar deaths remain unclear. As large samples of cosmological SNe Ia continue to be collected, the scatter in brightnesses of these events is equally affected by systematic errors as statistical. Thus we need to understand the physics of SNe Ia better, and in particular we must know more about the progenitors of these SNe so that we can derive better estimates for their true intrinsic brightnesses. The host galaxies of SNe Ia provide important indirect clues as to the nature of SN Ia progenitors. In this Thesis we utilize the host galaxies of SNe Ia discovered by the Nearby Supernova Factory (SNfactory) to pursue several key investigations into the nature of SN Ia progenitors and their effects on SN Ia brightnesses. We first examine the host galaxy of SN 2007if, an important member of the subclass of SNe Ia whose extreme brightnesses indicate a progenitor that exceeded the canonical Chandrasekhar-mass value presumed for normal SNe Ia, and show that the host galaxy of this SN is composed of very young stars and has extremely low metallicity, providing important constraints on progenitor scenarios for this SN. We then utilize the full sample of SNfactory host galaxy masses (measured from photometry) and metallicities (derived from optical spectroscopy) to examine several global properties of SN Ia progenitors: (i) we show that SN Ia hosts show tight agreement with the normal galaxy mass-metallicity relation; (ii) comparing the observed distribution of SN Ia host galaxy masses to a theoretical model that couples galaxy physics to the SN Ia delay time distribution (DTD), we show the power of the SN Ia host mass distribution in constraining the SN Ia DTD; and (iii) we show that the lack of ultra-low metallicities in the SNfactory SN Ia host sample gives provisional support for the theorized low-metallicity inhibition of SNe Ia. Finally we revisit recent studies which found that the corrected brightnesses of SNe Ia (after application of the standard light curve width and color corrections) correlate with the masses of their host galaxies. We confirm this trend with host mass using SNfactory data, and for the first time confirm that an analogous trend exists with host metallicity. We then apply a spectroscopic standardization technique developed by SNfactory and show that this method significantly reduces the observed bias. In this Thesis we show that SN Ia host galaxies continue to provide key insight into SN Ia progenitors, and also illuminate possible biases in SN Ia brightness standardization techniques.
Download or read book Improving the Precision of Type I A Supernova Cosmology written by Jing Lu and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Type Ia supernovae (SNe Ia) mark the beginning and the end of stellar evolution. They are one of the most powerful cosmological probes in our universe thanks to their high intrinsic luminosities and standardizable properties. In the 1990s, the observation of SNe Ia led to the discovery of the accelerating cosmic expansion that was awarded the Nobel Prize in 2011. Despite decades of advancements, the exact details of progenitor systems (id est what exploded), explosion mechanisms (id est, how they exploded), and evolution effect (id est are the nearby population the same as those in the early universe?) are still not fully understood yet. With more advanced observation surveys forthcoming in the near future, such as those on board the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope, the systematic uncertainties of SNe Ia observations will continue to dominate the error budget of their distance measurements. This dissertation is motivated to improve the precision of SN~Ia cosmology by understanding the physics and diversity and SNe Ia, as well as improving the astronomical tools needed for cosmological purposes. Photometric and spectroscopic observational studies of the first homogenous sample of the peculiar 03fg-like SNe Ia obtained by the Carnegie Supernovae Project (CSP) are conducted to investigate the physics of SNe Ia. 03fg-like events are usually more luminous than the normal SNe Ia and exhibit peculiar light-curve shapes in the redder filters, such as the weak or missing secondary maxima and the delayed peak time in iYJH bands. Spectroscopically, 03fg-like SN Ia show peculiar features in both optical and near-infrared (NIR) regions, such as the stronger C, slower Si, and the lack of the H-band break. One of the most extreme objects within this subgroup, ASASSN-15hy, is used for the case study of an envelope model that could potentially explain all 03fg-like SNe~Ia. It is found that a core degenerate scenario, an explosion of a degenerate white dwarf core inside a nondegenerate envelope, with a transition from deflagration to detonation can explain the observed peculiar properties. In the case of ASASSN-15hy, the low metallicity of the progenitor is a key aspect of the model explanation. In fact, a low-metallicity host environment is a shared preference among these 03fg-like SNe~Ia. Such host environment is more common in the early universe, which brings up the concern that 03fg-like SNe~Ia may be a problem for high-redshift SN~Ia cosmology due to detection bias and potential evolution preference. Therefore, more detailed observational and theoretical studies of these events are strongly recommended. Another main focus of this dissertation is on the development of a new NIR spectral template of SNe Ia that captures the feature variations that are correlated with the light-curve shapes. Compared to optical observations, NIR observations of SN Ia are less sensitive to dust and have more uniform peak luminosities, which are beneficial for cosmological purposes. A spectral template is usually needed to fit the light curves of SNe Ia accurately in order to estimate the distance. However, the NIR part of the existing spectral templates lacks an accurate description of the intrinsic spectral variations. Using the largest and most homogeneous collection of NIR spectra of SNe Ia to date collected by CSP-II, we are able to explore the NIR spectral diversity of SNe Ia and build a new NIR spectra template. Principal component analysis and Gaussian process regression are used for the template construction, which reduces data dimensionality and models the parameter dependence, respectively. Using the new template reduces the systematic uncertainties in K-corrections by ~90% compared to those from the Hsiao template. Furthermore, this template can serve as the baseline spectral energy distribution for various light-curve fitters and can identify peculiar spectral features that might point to compelling physics. The NIR spectra data and template presented in this work will substantially improve future SN Ia cosmological experiments, for both nearby and distant samples.
Download or read book Type Ia Supernovae written by Jens C. Niemeyer and published by Cambridge University Press. This book was released on 2000-05 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: A unique and wide-ranging review of one of the most dramatic research results in astronomy in recent decades.
Download or read book Spectral Observations and Analyses of Low Redshift Type Ia Supernovae written by Jeffrey Michael Silverman and published by . This book was released on 2011 with total page 798 pages. Available in PDF, EPUB and Kindle. Book excerpt: The explosive deaths of stars, known as a supernovae (SNe), have been critical to our understanding of the Universe for centuries. From the first evidence of a changing Universe beyond the Moon (Brahe1573) to the first evidence of the accelerating expansion of the Universe (Riess et al. 1998; Perlmutter et al. 1999), SNe - and often a specific subclass of SNe called Type Ia SNe (SNe Ia) - have been integral to astronomical research. An introduction to SNe, their importance in astronomy, and how we observe them is given in Chapter 1. How SNe Ia explode, what progenitor systems give rise to them, and how different initial conditions affect the observed outcomes of these objects are understood only at a relatively basic level. In other words, a detailed understanding of the physics behind SNe Ia is still lacking. One way astronomers can begin to solve these problems, and others involving SNe Ia, is to obtain and analyze a large, self-consistent dataset of SN Ia observations. This is the goal of the Berkeley SN Ia Program (BSNIP) which comprises the majority of this Thesis. In the second Chapter, I present the full BSNIP sample which consists of 1298 low-redshift (z greater than or equal to 0.2) optical spectra of 582 SNe Ia observed from 1989 through the end of 2008. Many of the SNe have well-calibrated light curves with measured distances as well as spectra which have been corrected for host-galaxy contamination. Most of the data were obtained using the Kast double spectrograph mounted on the Shane 3 m telescope at Lick Observatory with typical wavelength coverage of 3300-10400 A, which is significantly larger than that of most previously published SN Ia spectral datasets. I also present the BSNIP observing and reduction procedures used during the two decades over which the data were collected. In addition, I describe our spectral classification scheme (using the SuperNova IDentification code, SNID; Blondin & Tonry 2007), utilizing my newly constructed set of SNID spectral templates. These templates allow me to accurately spectroscopically classify the entire BSNIP dataset, and by doing so I am able to reclassify a handful of objects as bona fide SNe Ia and a few other objects as members of some of the peculiar SN Ia subtypes. In fact, the BSNIP dataset includes spectra of nearly 90 spectroscopically peculiar SNe Ia. I also present spectroscopic host-galaxy redshifts of some SNe Ia where these values were previously unknown. The sheer size of the BSNIP dataset and the consistency of the observation and reduction methods makes this sample unique among all other published SN Ia datasets and is complementary in many ways to the large, low-redshift SN Ia spectra presented by Matheson et al. 2008 and Blondin et al. 2011. I present measurements of spectral features of 432 low-redshift (z z x1 and c) and spectral measurements to calculate distance moduli. The residuals from these models is then compared to the standard model which only uses light-curve stretch and color. The pEW of Si II lamda 4000 is found to be a good indicator of light-curve width and the pEWs of the Mg II and Fe II complexes are relatively good proxies for color. However, a distance model only using these spectroscopic measurements performs worse than the standard model which uses only light-curve parameters. When using a distance model which combines the ratio of fluxes near 3̃600 A and 4̃300 A with both x1 and c, the Hubble residuals are decreased by 12%, which is found to be significant at the 2.4 omega level. The weighted root-mean square of the residuals using this model is 0.130 plus or minus 0.019 mag (as compared to 0.146 plus or minus 0.019 mag when using the same sample with the standard model). This Hubble diagram fit has one of the smallest scatters ever published and at the highest significance ever seen in such a study. Finally, these results are discussed with regard to how they can improve the cosmological accuracy of future, large-scale SN Ia surveys. Finally, I conclude this Thesis with an in-depth study of a quite peculiar SN Ia, not included in the BSNIP sample. Chapter 5 presents and analyzes optical photometry and spectra of the extremely luminous and slowly evolving Type Ia SN 2009dc, and offers evidence that it is a super-Chandrasekhar mass (SC) SN Ia and thus had a SC white dwarf (WD) progenitor. Optical spectra of SN 2007if, a similar object, are also shown. SN 2009dc had one of the most slowly evolving light curves ever observed for a SN Ia, with a rise time of 2̃3 d and delta m15(B) = 0.72 mag. I calculate a lower limit to the peak bolometric luminosity of 2̃.4x1043 erg s-1, though the actual value is likely almost 40% larger. Optical spectra of SNe 2009dc and 2007if obtained near maximum brightness exhibit strong C II features (indicative of a significant amount of unburned material), and the post-maximum spectra are dominated by iron-group elements. All of the spectra of SNe 2009dc and 2007if also show low expansion velocities. However, I see no strong evidence in SN 2009dc for a velocity "plateau" near maximum light like the one seen in SN 2007if (Scalzo et al. 2010). The high luminosity and low expansion velocities of SN 2009dc lead to a derived WD progenitor mass of more than 2 MSun and a 56Ni mass of about 1.4-1.7 MSun. I propose that the host galaxy of SN 2009dc underwent a gravitational interaction with a neighboring galaxy in the relatively recent past. This may have led to a sudden burst of star formation which could have produced the SC WD progenitor of SN 2009dc and likely turned the neighboring galaxy into a "post-starburst galaxy." No published model seems to match the extreme values observed in SN 2009dc, but simulations do show that such massive progenitors can exist (likely as a result of the merger of two WDs) and can possibly explode as SC SNe Ia.
Download or read book Outskirts of Galaxies written by Johan H. Knapen and published by Springer. This book was released on 2017-07-09 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and accretion as observed through deep imaging and spectroscopy, and guide the reader through the various formation and evolution scenarios for galaxies. The reviews focus on the major open questions in the field, and explore how they can be tackled in the future. This book provides a unique entry point into the field for graduate students and non-specialists, and serves as a reference work for researchers in this exciting new field.
Download or read book Spectroscopic Properties of Star Forming Host Galaxies and Type Ia Supernova Hubble Residuals in a Nearly Unbiased Sample written by and published by . This book was released on 2011 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: We examine the correlation between supernova host galaxy properties and their residuals on the Hubble diagram. We use supernovae discovered during the Sloan Digital Sky Survey II - Supernova Survey, and focus on objects at a redshift of z 0.15, where the selection effects of the survey are known to yield a complete Type Ia supernova sample. To minimize the bias in our analysis with respect to measured host-galaxy properties, spectra were obtained for nearly all hosts, spanning a range in magnitude of -23
Download or read book The Effect of Host Galaxies on Type Ia Supernovae in the SDSS II Supernova Survey written by and published by . This book was released on 2010 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Type Ia Supernova Evolution and Dark Energy written by Ryan Joseph Foley and published by . This book was released on 2008 with total page 714 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Worlds New Horizons in Astronomy and Astrophysics written by National Research Council and published by National Academies Press. This book was released on 2011-02-04 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Driven by discoveries, and enabled by leaps in technology and imagination, our understanding of the universe has changed dramatically during the course of the last few decades. The fields of astronomy and astrophysics are making new connections to physics, chemistry, biology, and computer science. Based on a broad and comprehensive survey of scientific opportunities, infrastructure, and organization in a national and international context, New Worlds, New Horizons in Astronomy and Astrophysics outlines a plan for ground- and space- based astronomy and astrophysics for the decade of the 2010's. Realizing these scientific opportunities is contingent upon maintaining and strengthening the foundations of the research enterprise including technological development, theory, computation and data handling, laboratory experiments, and human resources. New Worlds, New Horizons in Astronomy and Astrophysics proposes enhancing innovative but moderate-cost programs in space and on the ground that will enable the community to respond rapidly and flexibly to new scientific discoveries. The book recommends beginning construction on survey telescopes in space and on the ground to investigate the nature of dark energy, as well as the next generation of large ground-based giant optical telescopes and a new class of space-based gravitational observatory to observe the merging of distant black holes and precisely test theories of gravity. New Worlds, New Horizons in Astronomy and Astrophysics recommends a balanced and executable program that will support research surrounding the most profound questions about the cosmos. The discoveries ahead will facilitate the search for habitable planets, shed light on dark energy and dark matter, and aid our understanding of the history of the universe and how the earliest stars and galaxies formed. The book is a useful resource for agencies supporting the field of astronomy and astrophysics, the Congressional committees with jurisdiction over those agencies, the scientific community, and the public.
Download or read book Spectroscopic Determination of the Low Redshift Type Ia Supernova Rate from the Sloan Digital Sky Survey written by and published by . This book was released on 2011 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supernova rates are directly coupled to high mass stellar birth and evolution. As such, they are one of the few direct measures of the history of cosmic stellar evolution. In this paper we describe an probabilistic technique for identifying supernovae within spectroscopic samples of galaxies. We present a study of 52 type Ia supernovae ranging in age from -14 days to +40 days extracted from a parent sample of \simeq 50,000 spectra from the SDSS DR5. We find a Supernova Rate (SNR) of 0.472{̂+0.048}_{-0.039}(Systematic){̂+0.081}_{-0.071}(Statistical)SNu at a redshift of = 0.1. This value is higher than other values at low redshift at the 1{\sigma}, but is consistent at the 3{\sigma} level. The 52 supernova candidates used in this study comprise the third largest sample of supernovae used in a type Ia rate determination to date. In this paper we demonstrate the potential for the described approach for detecting supernovae in future spectroscopic surveys.
Download or read book Supernova Cosmology and How to Talk about It written by Rachel Cane Wolf and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery of the accelerating expansion of the Universe launched a new chapter in modern cosmology. Evidence for this accelerating expansion was first observed using Type Ia supernovae, which are brilliant, standardizable explosions that can be detected at large distances and used to infer cosmological parameters. New surveys are being designed to detect thousands of Type Ia supernovae, ushering in an era where parameter inference is no longer limited by statistics, but by systematic uncertainties. One of these systematics which is not well understood is the progenitor and progenitor environment, which can be investigated by studying properties of the supernova host galaxy. In this dissertation, I use the three-year sample of photometrically-classified and spectroscopically-confirmed Type Ia supernovae from Sloan Digital Sky Survey-II Supernova Survey to explore correlations between supernova luminosity and host-galaxy mass, metallicity, and star-formation rate. Observations suggest that such correlations should be incorporated to improve the standardization of Type Ia supernova luminosities. As such, new techniques for parameter inference will need to accommodate increasingly large samples of supernovae and a variety of standardization models. In this dissertation, I also introduce the BAyesian hierarchical Modeling with BIased Simulations (BAMBIS) algorithm, a novel approach to parameter inference using Type Ia supernovae which can, in principle, include systematics such as host-galaxy correlations in a robust statistical framework.In addition to offering new scientific research opportunities, the quest to understand the evolution of the cosmos brings excellent opportunities for astronomers to engage in science education and public outreach (EPO). I present an analysis of the Dark Energy Survey EPO program, a unique large-scale astronomy EPO initiative organized and led entirely by professional astronomers. In this analysis, I detail the development of the EPO program as well as analyze the strengths and weaknesses of a subset of specific initiatives. I also discuss scientists' reported methods of communicating science with the public.
Download or read book Nature Versus Nurture written by Melissa Lynn Graham and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Supernovae of Type Ia, SNe Ia, are currently the most powerful tool of modern cosmology, but their progenitor scenario is not yet well constrained. Recent studies of SN Ia rates in radio-loud early-type galaxies, and members of rich clusters, suggest a possible influence on SN Ia explosions outside of the established correlation with the age of the parent galaxy's stellar population (via the current specific star formation rate, sSFR). These rates were used to show that the characteristics of SN Ia progenitor systems may be inconsistent with theoretical expectations of the most popular scenarios. The astrophysical question of this thesis is: do parent galaxy and environment influence the rates and properties of Type Ia supernovae, and, if so, how?Towards this end, we combine the database of Type Ia supernovae from the Canada-France-Hawaii Telescope's Supernova Legacy Survey with publicly available catalogs including: galaxy photometric and spectroscopic redshifts, radio and infrared sources, and members of galaxy groups and clusters. This is the most comprehensive set of multi-wavelength host properties and environment parameters for intermediate redshift Type Ia supernovae yet compiled. We present the SNLS SN Ia rate per unit mass in a variety of parent galaxy and environment samples. We also statistically assess the probability of discrepancies between our rates, those of previous works at low redshift, rates in the general population of galaxies, and predictions of established empirical SN Ia rate models. In general, we do not find statistically significant evidence for SN Ia rate enhancements over the general population in galaxies which are radio-loud, infrared-bright, or associated with galaxy groups and clusters. In cases where we do find a suggestive rate enhancement, it is always with less than 2-sigma confidence. These rates agree with established empirical rate models, which in turn are consistent with theoretical expectations of the most plausible progenitor scenarios. Furthermore, we find the properties of SNLS SNe Ia in these types of hosts and environments are consistent with the predictions of these scenarios. We conclude that, aside from the established correlation with host sSFR, no conclusive evidence is observed with SNLS data for strictly environmental effects on SN Ia rates. This supports their continued status as cosmological standard candles.
