Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves Page: 2 of 102
101 pagesView a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
2
reddening. Current systematic errors can be reduced by improving SN Ia pho-
tometric accuracy, by including the CfA3 sample to retrain light-curve fitters,
by combining optical SN Ia photometry with near-infrared photometry to under-
stand host-galaxy extinction, and by determining if different environments give
rise to different intrinsic SN Ia luminosity after correction for light-curve shape
and color.
Subject headings: supernovae: general cosmology: dark energy
1. Introduction
One of the limitations of supernova cosmology has been the relatively low number of
cosmologically-useful nearby SN Ia. The paucity of nearby objects has caused the statistical
uncertainties in measurements of time-independent dark energy to be on the same order
as systematic uncertainties. For example, Kowalski et al. (2008) use 250 SN Ia at high
redshift but only 57 at low redshift. As part of their study, they add eight new nearby
SN Ia light curves and find that their inclusion helps reduce the statistical uncertainty in
the measurement of the cosmological constant. In this paper, we combine the latest sample
of nearby SN Ia optical photometry from the CfA SN Group (CfA3 sample) (Hicken et al.
2009, hereafter, H09) with samples from the literature and use multiple light-curve fitters to
calculate dark energy values. The CfA3 sample consists of 185 objects, compared with 29
from the Calan-Tololo survey (Hamuy et al. 1996a), 22 from the "CfA1" sample (Riess et al.
1999), and 44 from the "CfA2" sample Jha et al. (2006). As many as 133 are above z = 0.01
and are useful for dark energy calculations, depending on what cuts are made. This increases
the number of cosmologically-useful nearby SN Ia by a factor of roughly 2.6-2.9 and reduces
the statistical uncertainties of time-independent dark energy to the point where the largest
uncertainties that remain are systematic. Because of these systematic uncertainties, we do
not claim than any of our dark energy values is the "right" one. However, as the systematic
errors (some of which are identified and addressed in this paper) are reduced in future studies,
the promise of constraining cosmology from SN Ia with high precision will become more real.
The task of solving the systematic problems that limit SN cosmology will be challenging but
it is the most important area to focus on.
There are two main sources of known systematic uncertainty in SN cosmology. One is
in the photometry itself. For example, good nearby light curves only have a typical accuracy
of 0.03 mag (as opposed to a precision of 0.015 mag) (see H09) and different groups' nearby
samples disagree in their mean Hubble residuals by about 0.03 mag (see 3.12 herein). The
second is the method of SN Ia distance estimation, typically involving corrections for light-
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Hicken, Malcolm; U., /Harvard-Smithsonian Ctr. Astrophys. /Harvard; Wood-Vasey, W.Michael; U., /Pittsburgh; Blondin, Stephane; Observ., /European Southern et al. Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves, article, April 6, 2012; United States. (https://digital.library.unt.edu/ark:/67531/metadc836308/m1/2/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.