Dust Extinction toward Type Ia Supernovae

Ia型超新星（SNe Ia）是强大的宇宙学“可测量的蜡烛”，也是距离遥远星系最精确的指示器。 这使得它们对于测量宇宙的膨胀率至关重要。然而，它们在精确宇宙学中的应用的一个限制因素在于我们校正由于干涉尘埃而导致的SNe光变暗的能力，这种现象被称为“尘埃消光”。“密苏里州-哥伦比亚大学的天文学家将通过系统地探索由空间和地面望远镜在从紫外线到光学到近红外线的广泛波长范围内观测到的大约60个超新星Ia来研究超新星Ia的尘埃消光。通过将每个超新星Ia的观测光度学（光谱和光强度）与未消光的原始模板超新星Ia进行比较，研究人员将确定消光量及其波长依赖性（即，消光曲线）。 导出的消光曲线将与理论模型进行比较，使科学家能够探索每个Ia超新星的尘埃大小和成分。最后，研究人员将探索尘埃和灭绝特性是否以及如何随着超新星Ia的内在特性以及其宿主星系的相关特性而系统地变化。 这项研究将对培养研究生和发展密苏里州大学的本科天文学项目产生积极的影响，并通过一个积极的社区外展计划教育非科学专业和公众。在分析超新星Ia光变曲线的一个长期存在的难题是它们明显的颜色和亮度变化的性质。在宇宙学的Ia超新星分析中广泛使用的“红-暗”色-光度关系掩盖了它有两个独立的物理起源的事实：（i）内在的相关性，这是由爆炸的白色矮星的物理学引起的;（ii）由于宿主星系中的星际尘埃而明显变暗和变红。研究人员将探索尘埃和消光特性是否以及如何随着SNe Ia的内在特性而系统地变化（例如，固有颜色、光度、光变曲线形状、衰减率、光谱特性和膨胀速度）以及它们的宿主星系的特性（例如，形态类型、金属丰度）。 这项工作将有助于天文学家了解从SNe Ia确定宇宙学参数的主导系统效应，SNe固有颜色的知识和由于宿主星系的灭绝而变暗。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Type Ia supernovae (SNe Ia) are powerful cosmological "standardizable candles" and the most precise indicators of the distance to faraway galaxies. This makes them critical for measuring the expansion rate of the universe. However, a limiting factor in their use for precision cosmology rests on our ability to correct for the dimming of SNe light due to intervening dust, a phenomenon known as "dust extinction." Astronomers at the University of Missouri - Columbia will study the dust extinction toward SNe Ia through a systematic exploration of about 60 SNe Ia observed by space-borne and ground-based telescopes over a broad wavelength range spanning from the ultraviolet through the optical to the near infrared. By comparing the observed photometry (spectrum and intensity of light) of each SN Ia with that of a pristine template SN Ia without extinction, the researchers will determine the extinction quantity and its wavelength dependence (i.e., extinction curve). The derived extinction curve will be compared to theoretical models, enabling the scientists to explore the dust size and composition for each SN Ia. Finally, the researchers will explore whether and how the dust and extinction properties vary systematically with the intrinsic properties of SNe Ia as well as with relevant properties of their host galaxies. This research will have a positive impact on training graduate students and on developing an undergraduate astronomy program at the University of Missouri, as well as educating non-science majors and the general public, through a vigorous program of community outreach.A longstanding puzzle in the analysis of SN Ia light curves is the nature of their apparent color and brightness variations. The "redder-dimmer'' color-luminosity relation widely used in cosmological SN Ia analyses masks the fact that it has two separate physical origins: (i) an intrinsic correlation, which arises from the physics of exploding white dwarfs and (ii) an apparent dimming and reddening due to interstellar dust in the host galaxy. The researchers will explore whether and how the dust and extinction properties vary systematically with the intrinsic properties of SNe Ia (e.g., intrinsic color, luminosity, light-curve shape, decline rate, spectroscopic properties, and expansion velocity) as well as the properties of their host galaxies (e.g., morphological type, metallicity). The work will help astronomers to understand the dominant systematic effects for the determination of cosmological parameters from SNe Ia, knowledge of SNe intrinsic colors and dimming due to extinction by host galaxy. It could thus impact both supernova cosmology and the knowledge of extragalactic extinction.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.