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Journal Article•DOI•

Measurements of Omega and Lambda from 42 High-Redshift Supernovae

Saul Perlmutter1, Saul Perlmutter2, Greg Aldering1, Gerson Goldhaber2, Gerson Goldhaber1, R. A. Knop1, Peter Nugent1, P. G. Castro3, P. G. Castro1, Susana E. Deustua1, Sebastien Fabbro4, Sebastien Fabbro1, A. Goobar1, A. Goobar5, Donald E. Groom1, I. M. Hook6, I. M. Hook1, A. G. Kim2, A. G. Kim7, A. G. Kim1, M. Y. Kim1, Julia C. Lee8, Julia C. Lee1, Nelson J. Nunes1, Nelson J. Nunes3, Reynald Pain4, Reynald Pain1, C. R. Pennypacker2, C. R. Pennypacker1, Robert Quimby1, Christopher Lidman6, Richard S. Ellis8, Mike Irwin8, Richard G. McMahon8, Pilar Ruiz-Lapuente9, Nicholas A. Walton, Bradley E. Schaefer10, B. J. Boyle, Alexei V. Filippenko2, Thomas Matheson2, A. S. Fruchter11, Nino Panagia12, Nino Panagia11, Heidi Jo Newberg, Warrick J. Couch13 •
Lawrence Berkeley National Laboratory1, University of California, Berkeley2, Instituto Superior Técnico3, Pierre-and-Marie-Curie University4, Stockholm University5, European Southern Observatory6, Collège de France7, University of Cambridge8, University of Barcelona9, Yale University10, Space Telescope Science Institute11, European Space Agency12, University of New South Wales13
01 Jun 1999-The Astrophysical Journal (IOP Publishing)-Vol. 517, Iss: 2, pp 565-586
TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured using the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology project.
Abstract: We report measurements of the mass density, Omega_M, and cosmological-constant energy density, Omega_Lambda, of the universe based on the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these SNe, at redshifts between 0.18 and 0.83, are fit jointly with a set of SNe from the Calan/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All SN peak magnitudes are standardized using a SN Ia lightcurve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8 Omega_M - 0.6 Omega_Lambda ~= -0.2 +/- 0.1 in the region of interest (Omega_M <~ 1.5). For a flat (Omega_M + Omega_Lambda = 1) cosmology we find Omega_M = 0.28{+0.09,-0.08} (1 sigma statistical) {+0.05,-0.04} (identified systematics). The data are strongly inconsistent with a Lambda = 0 flat cosmology, the simplest inflationary universe model. An open, Lambda = 0 cosmology also does not fit the data well: the data indicate that the cosmological constant is non-zero and positive, with a confidence of P(Lambda > 0) = 99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t_0 = 14.9{+1.4,-1.1} (0.63/h) Gyr for a flat cosmology. The size of our sample allows us to perform a variety of statistical tests to check for possible systematic errors and biases. We find no significant differences in either the host reddening distribution or Malmquist bias between the low-redshift Calan/Tololo sample and our high-redshift sample. The conclusions are robust whether or not a width-luminosity relation is used to standardize the SN peak magnitudes.

Summary (2 min read)

Jump to: [1. INTRODUCTION] – [2. BASIC DATA AND PROCEDURES] – [5. RESULTS AND ERROR BUDGET] and [6. CONCLUSIONS AND DISCUSSION]

1. INTRODUCTION

  • Since the earliest studies of supernovae, it has been suggested that these luminous events might be used as standard candles for cosmological measurements (Baade 1938).
  • Even after an impressive multiyear e†ort by et al. (1989), it was only possible toNÔrgaard-Nielsen follow one SN Ia, at z\ 0.31, discovered 18 days past its peak brightness.
  • In particular, Goobar & Perlmutter (1995) showed the possibility of separating the relative contributions of the mass density, and the cosmological constant, ", to) M , changes in the expansion rate by studying supernovae at a range of redshifts.
  • Here the authors report on the complete analysis of 42 supernovae from the Supernova Cosmology Project, including the reanalysis of their previously reported supernovae with improved calibration data and improved photometric and spectroscopic SN Ia templates.

2. BASIC DATA AND PROCEDURES

  • The new supernovae in this sample of 42 were all dis- covered while still brightening, using the Cerro Tololo Inter-American Observatory (CTIO) 4 m telescope with the 20482 pixel prime-focus CCD camera or the 4] 20482 pixel Big Throughput Camera.10.
  • The conÐdence regions of Figure 5c and the ) M flat results in Table 3 show that the cosmological parameters found for Ðt H di†er by less than half of a standard deviation from those for Ðt C. 4.1.3.
  • Analysis with Reddening Correction of Individual Supernovae.
  • To be conservative the authors take the classical Malmquist bias of 0.04 mag for the low-redshift data set and the least biased value of 0.01 mag for the high-redshift data set, and they consider systematic uncertainty from this source to be the di†erence, 0.03 mag, in the direction of low-redshift supernovae more biased than high-redshift.
  • The results (Ðt D), as shown in Figure 5b and listed in Table 3, are in extremely close agreement with those of the light-curveÈwidth-corrected Ðt C.

5. RESULTS AND ERROR BUDGET

  • From Table 3 and Figure 5a, it is clear that the results of Ðts A, B, and C are quite close to each other, so the authors can conclude that their measurement is robust with respect to the choice of these supernova subsets.
  • The shaded contours (Ðt C) are the conÐdence regions Note that the statistical error in and aM Bare derived quantities from their four-parameter Ðts.
  • To characterize the e†ect of the identiÐed systematic uncertainties, the authors have reÐt the supernovae of Ðt C for the hypothetical case (Ðt J) in which each of the high-redshift supernovae were discovered to be 0.04 mag brighter than measured, or, equivalently, the low-redshift supernovae were discovered to be 0.04 mag fainter than measured.

6. CONCLUSIONS AND DISCUSSION

  • The conÐdence regions of Figure 7 and the residual plot of Figure 2b lead to several striking implications.
  • The best-Ðt model (the center of the shaded contours) indicates that the energy density in the cosmological constant is D0.5 more than that in the form of mass energy density.
  • Many of these residual concerns about the measurement can be addressed with new studies of low-redshift supernovae.

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Figures (14)

Content maybe subject to copyright    Report

THE ASTROPHYSICAL JOURNAL, 517 :565È586, 1999 June 1
1999. The American Astronomical Society. All rights reserved. Printed in U.S.A.(
MEASUREMENTS OF ) AND " FROM 42 HIGH-REDSHIFT SUPERNOVAE
S. PERLMUTTER,1 G. ALDERING,G.GOLDHABER,1 R. A. KNOP,P.NUGENT,P.G.CASTRO,2 S. DEUSTUA,S.FABBRO,3
A. GOOBAR,4 D. E. GROOM,I.M.HOOK,5 A. G. KIM,1,6 M. Y. KIM,J.C.LEE,7 N. J. NUNES,2 R. PAIN,3
C. R. PENNYPACKER,8 AND R. QUIMBY
Institute for Nuclear and Particle Astrophysics, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA 94720
C. LIDMAN
European Southern Observatory, La Silla, Chile
R. S. ELLIS,M.IRWIN, AND R. G. MCMAHON
Institute of Astronomy, Cambridge, England, UK
P. RUIZ-LAPUENTE
Department of Astronomy, University of Barcelona, Barcelona, Spain
N. WALTON
Isaac Newton Group, La Palma, Spain
B. SCHAEFER
Department of Astronomy, Yale University, New Haven, CT
B. J. BOYLE
Anglo-Australian Observatory, Sydney, Australia
A.VFILIPPENKO AND T. MATHESON
Department of Astronomy, University of California, Berkeley, CA
A. S. FRUCHTER AND N. PANAGIA9
Space Telescope Science Institute, Baltimore, MD
H. J. M. NEWBERG
Fermi National Laboratory, Batavia, IL
AND
W. J. COUCH
University of New South Wales, Sydney, Australia
(THE SUPERNOVA COSMOLOGY PROJECT)
Received 1998 September 8 ; accepted 1998 December 17
ABSTRACT
We report measurements of the mass density, and cosmological-constant energy density, of)
M
, )
"
,
the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology
Project. The magnitude-redshift data for these supernovae, at redshifts between 0.18 and 0.83, are Ðtted
jointly with a set of supernovae from the Supernova Survey, at redshifts below 0.1, to yieldCala
n/Tololo
values for the cosmological parameters. All supernova peak magnitudes are standardized using a SN Ia
light-curve width-luminosity relation. The measurement yields a joint probability distribution of the
cosmological parameters that is approximated by the relation in the region0.8)
M
[ 0.6)
"
B [0.2 ^ 0.1
of interest For a Ñat cosmology we Ðnd (1 p statistical)()
M
[ 1.5). ()
M
] )
"
\ 1) )
M
flat \ 0.28
~0.08
`0.09
~0.04
`0.05
(identiÐed systematics). The data are strongly inconsistent with a " \ 0 Ñat cosmology, the simplest
inÑationary universe model. An open, " \ 0 cosmology also does not Ðt the data well: the data indicate
that the cosmological constant is nonzero and positive, with a conÐdence of P("[0) \ 99%, including
the identiÐed systematic uncertainties. The best-Ðt age of the universe relative to the Hubble time is
Gyr for a Ñat cosmology. The size of our sample allows us to perform a variety oft
0
flat \ 14.9
~1.1
`1.4(0.63/h)
statistical tests to check for possible systematic errors and biases. We Ðnd no signiÐcant di†erences in
either the host reddening distribution or Malmquist bias between the low-redshift sampleCala
n/Tololo
and our high-redshift sample. Excluding those few supernovae that are outliers in color excess or Ðt
residual does not signiÐcantly change the results. The conclusions are also robust whether or not a
width-luminosity relation is used to standardize the supernova peak magnitudes. We discuss and con-
strain, where possible, hypothetical alternatives to a cosmological constant.
Subject headings: cosmology: observations È distance scale È supernovae: general
1 Center for Particle Astrophysics, University of California, Berkeley, California.
2 Instituto Superior Lisbon, Portugal.Te
cnico,
3 LPNHE, CNRS-IN2P3, and University of Paris VI and VII, Paris, France.
4 Department of Physics, University of Stockholm, Stockholm, Sweden.
5 European Southern Observatory, Munich, Germany.
6 PCC, CNRS-IN2P3, and de France, Paris, France.Colle
`
ge
7 Institute of Astronomy, Cambridge, England, UK.
8 Space Sciences Laboratory, University of California, Berkeley, California.
9 Space Sciences Department, European Space Agency.
565
566 PERLMUTTER ET AL. Vol. 517
1. INTRODUCTION
Since the earliest studies of supernovae, it has been sug-
gested that these luminous events might be used as standard
candles for cosmological measurements (Baade 1938). At
closer distances they could be used to measure the Hubble
constant if an absolute distance scale or magnitude scale
could be established, while at higher redshifts they could
determine the deceleration parameter (Tammann 1979;
Colgate 1979). The Hubble constant measurement became
a realistic possibility in the 1980s, when the more homoge-
neous subclass of type Ia supernovae (SNe Ia) was identiÐed
(see Branch 1998). Attempts to measure the deceleration
parameter, however, were stymied for lack of high-redshift
supernovae. Even after an impressive multiyear e†ort by
et al. (1989), it was only possible toNÔrgaard-Nielsen
follow one SN Ia, at z \ 0.31, discovered 18 days past its
peak brightness.
The Supernova Cosmology Project was started in 1988 to
address this problem. The primary goal of the project is the
determination of the cosmological parameters of the uni-
verse using the magnitude-redshift relation of type Ia super-
novae. In particular, Goobar & Perlmutter (1995) showed
the possibility of separating the relative contributions of the
mass density, and the cosmological constant, ",to)
M
,
changes in the expansion rate by studying supernovae at a
range of redshifts. The Project developed techniques,
including instrumentation, analysis, and observing stra-
tegies, that make it possible to systematically study high-
redshift supernovae (Perlmutter et al. 1995a). As of 1998
March, more than 75 type Ia supernovae at redshifts
z \ 0.18È0.86 have been discovered and studied by the
Supernova Cosmology Project (Perlmutter et al. 1995b,
1996, 1997a, 1997b, 1997c, 1997d, 1998a).
A Ðrst presentation of analysis techniques, identiÐcation
of possible sources of statistical and systematic errors, and
Ðrst results based on seven of these supernovae at redshifts
z D 0.4 were given in Perlmutter et al. (1997e; hereafter
referred to as P97). These Ðrst results yielded a conÐdence
region that was suggestive of a Ñat, " \ 0 universe but with
a large range of uncertainty. Perlmutter et al. (1998b) added
a z \ 0.83 SN Ia to this sample, with observations from the
Hubble Space Telescope (HST ) and Keck 10 m telescope,
providing the Ðrst demonstration of the method of separat-
ing and " contributions. This analysis o†ered prelimi-)
M
nary evidence for a lowÈmass-density universe with a
best-Ðt value of assuming " \ 0. Indepen-)
M
\ 0.2 ^ 0.4,
dent work by Garnavich et al. (1998a), based on three
supernovae at z D 0.5 and one at z \ 0.97, also suggested a
low mass density, with best-Ðt for " \ 0.)
M
\[0.1 ^ 0.5
Perlmutter et al. 1997f presented a preliminary analysis
of 33 additional high-redshift supernovae, which gave a
conÐdence region indicating an accelerating universe and
barely including a low-mass " \ 0 cosmology. Recent inde-
pendent work of Riess et al. (1998), based on 10 high-
redshift supernovae added to the Garnavich et al. (1998a)
set, reached the same conclusion. Here we report on the
complete analysis of 42 supernovae from the Supernova
Cosmology Project, including the reanalysis of our pre-
viously reported supernovae with improved calibration
data and improved photometric and spectroscopic SN Ia
templates.
2. BASIC DATA AND PROCEDURES
The new supernovae in this sample of 42 were all dis-
covered while still brightening, using the Cerro Tololo
Inter-American Observatory (CTIO) 4 m telescope with the
20482 pixel prime-focus CCD camera or the 4 ] 20482 pixel
Big Throughput Camera.10 The supernovae were followed
with photometry over the peak of their light curves and
approximately 2È3 months further (D40È60 days rest
frame) using the CTIO 4 m, Wisconsin-Indiana-Yale-
NOAO (WIYN) 3.6 m, ESO 3.6 m, Isaac Newton Telescope
(INT) 2.5 m, and the William Herschel Telescope (WHT) 4.2
m telescopes. (SN 1997ap and other 1998 supernovae have
also been followed with HST photometry.) The supernova
redshifts and spectral identiÐcations were obtained using
the Keck I and II 10 m telescopes with the Low-Resolution
Imaging Spectrograph (Oke et al. 1995) and the ESO 3.6 m
telescope. The photometry coverage was most complete in
Kron-Cousins R-band, with Kron-Cousins I-band photo-
metry coverage ranging from two or three points near peak
to relatively complete coverage paralleling the R-band
observations.
Almost all of the new supernovae were observed spectro-
scopically. The conÐdence of the type Ia classiÐcations
based on these spectra taken together with the observed
light curves, ranged from ““ deÐnite ÏÏ (when Si II features
were visible) to ““ likely ÏÏ (when the features were consistent
with type Ia and inconsistent with most other types). The
lower conÐdence identiÐcations were primarily due to host-
galaxy contamination of the spectra. Fewer than 10% of the
original sample of supernova candidates from which these
SNe Ia were selected were conÐrmed to be nonÈtype Ia, i.e.,
being active galactic nuclei or belonging to another SN
subclass; almost all of these nonÈSNe Ia could also have
been identiÐed by their light curves and/or position far from
the SN Ia Hubble line. Whenever possible, the redshifts
were measured from the narrow host-galaxy lines rather
than the broader supernova lines. The light curves and
several spectra are shown in Perlmutter et al. (1997e, 1997f,
1998b); complete catalogs and detailed discussions of the
photometry and spectroscopy for these supernovae will be
presented in forthcoming papers.
The photometric reduction and the analyses of the light
curves followed the procedures described in P97. The super-
novae were observed with the Kron-Cousins Ðlter that best
matched the rest-frame B and V Ðlters at the supernovaÏs
redshift, and any remaining mismatch of wavelength cover-
age was corrected by calculating the expected photometric
di†erenceÈthe ““ cross-Ðlter K-correction ÏÏÈusing template
SN Ia spectra as in Kim, Goobar, & Perlmutter (1996). We
have now recalculated these K-corrections (see Nugent et
al. 1998) using improved template spectra, based on an
extensive database of low-redshift SN Ia spectra recently
made available from the survey (Phillips et al.Cala
n/Tololo
1999). Where available, IUE and HST spectra (Cappellaro,
Turatto, & Fernley 1995; Kirshner et al. 1993) were also
added to the SN Ia spectra, including those published pre-
viously (1972E, 1981B, 1986G, 1990N, 1991T, 1992A, and
1994D: in Kirshner & Oke 1975; Branch et al. 1993; Phil-
lips et al. 1987; Je†ery et al. 1992; Meikle et al. 1996; Patat
et al. 1996). In Nugent et al. (1998) we show that the K-
corrections can be calculated accurately for a given day on
the supernova light curve and for a given supernova light-
10 Big Throughput Camera information is provided by G. Bernstein &
J. A. Tyson, 1998, at http://www.astro.lsa.umich.edu/btc/user.html.
No. 2, 1999 ) AND " FROM 42 HIGH-REDSHIFT SUPERNOVAE 567
curve width from the color of the supernova on that day.
(Such a calculation of K-correction based on supernova
color will also automatically account for any modiÐcation
of the K-correction due to reddening of the supernova; see
Nugent et al. 1998. In the case of insigniÐcant reddening the
SN Ia template color curves can be used.) We Ðnd that these
calculations are robust to mis-estimations of the light-curve
width or day on the light curve, giving results correct to
within 0.01 mag for light-curveÈwidth errors of ^25% or
light-curve phase errors of ^5 days even at redshifts where
Ðlter matching is the worst. Given small additional uncer-
tainties in the colors of supernovae, we take an overall sys-
tematic uncertainty of 0.02 mag for the K-correction.
The improved K-corrections have been recalculated for
all the supernovae used in this paper, including those pre-
viously analyzed and published. Several of the low-redshift
supernovae from the survey have relativelyCala
n/Tololo
large changes (as much as 0.1 mag) at times in their K-
corrected light curves. (These and other low-redshift super-
novae with new K-corrections are used by several
independent groups in constructing SN Ia light-curve tem-
plates, so the templates must be updated accordingly.) The
K-corrections for several of the high-redshift supernovae
analyzed in P97 have also changed by small amounts at the
light-curve peak mag] and somewhat[*K(t \ 0) [ 0.02
larger amounts by 20 days past peak [*K(t \ 20) [ 0.1
mag]; this primarily a†ects the measurement of the rest-
frame light-curve width. These K-correction changes
balance out among the P97 supernovae, so the Ðnal results
for these supernovae do not change signiÐcantly. (As we
discuss below, however, the much larger current data set
does a†ect the interpretation of these results.)
As in P97, the peak magnitudes have been corrected for
the light-curve width-luminosity relation of SNe Ia:
m
B
corr \ m
B
] *
corr
(s) , (1)
where the correction term is a simple monotonic func-*
corr
tion of the ““ stretch factor,ÏÏ s, that stretches or contracts the
time axis of a template SN Ia light curve to best Ðt the
observed light curve for each supernova (see P97; Perlmut-
ter et al. 1995a; Kim et al. 1999; Goldhaber et al. 1999; and
see Phillips 1993; Riess, Press, & Kirshner 1995, 1996
[hereafter RPK96]). A similar relation corrects the V -band
light curve, with the same stretch factor in both bands. For
the supernovae discussed in this paper, the template must
be time-dilated by a factor 1 ] z before Ðtting to the
observed light curves to account for the cosmological
lengthening of the supernova timescale (Goldhaber et al.
1995; Leibundgut et al. 1996a; Riess et al. 1997a). P97 cal-
culated by translating from s to (both describ-*
corr
(s) *m
15
ing the timescale of the supernova event) and then using the
relation between and luminosity as determined by*m
15
Hamuy et al. (1995). The light curves of the Cala
n/Tololo
supernovae have since been published, and we have directly
Ðtted each light curve with the stretched template method
to determine its stretch factor s. In this paper, for the light-
curve width-luminosity relation, we therefore directly use
the functional form
*
corr
(s) \ a(s [ 1) (2)
and determine a simultaneously with our determination of
the cosmological parameters. With this functional form, the
supernova peak apparent magnitudes are thus all
““ corrected ÏÏ as they would appear if the supernovae had the
light-curve width of the template, s \ 1.
We use analysis procedures that are designed to be as
similar as possible for the low- and high-redshift data sets.
Occasionally, this requires not using all of the data avail-
able at low redshift, when the corresponding data are not
accessible at high redshift. For example, the low-redshift
supernova light curves can often be followed with photo-
metry for many months with high signal-to-noise ratios,
whereas the high-redshift supernova observations are gen-
erally only practical for approximately 60 rest-frame days
past maximum light. This period is also the phase of the
low-redshift SN Ia light curves that is Ðtted best by the
stretched-template method and that best predicts the lumi-
nosity of the supernova at maximum. We therefore Ðtted
only this period for the light curves of the low-redshift
supernovae. Similarly, at high redshift the rest-frame
B-band photometry is usually much more densely sampled
in time than the rest-frame V -band data, so we use the
stretch factor that best Ðts the rest-frame B-band data for
both low- and high-redshift supernovae, even though at
low-redshift the V -band photometry is equally well
sampled.
Each supernova peak magnitude was also corrected for
Galactic extinction, using the extinction law of Cardelli,A
R
,
Clayton, & Mathis (1989), Ðrst using the color excess,
at the supernovaÏs Galactic coordinates pro-E(B[V )
SFÔD
,
vided by Schlegel, Finkbeiner, & Davis (1998) and thenÈ
for comparisonÈusing the value provided byE(B[V )
BÔH
D. Burstein & C. Heiles (1998, private communication; see
also Burstein & Heiles 1982). Galactic extinction, wasA
R
,
calculated from E(B[V ) using a value of the total-to-selec-
tive extinction ratio, speciÐc to eachR
R
4 A
R
/E(B[V ),
supernova. These were calculated using the appropriate
redshifted supernova spectrum as it would appear through
an R-band Ðlter. These values of range from 2.56 atR
R
z \ 0 to 4.88 at z \ 0.83. The observed supernova colors
were similarly corrected for Galactic extinction. Any extinc-
tion in the supernovaÏs host galaxy or between galaxies was
not corrected for at this stage but will be analyzed separa-
tely in ° 4.
All the same corrections for width-luminosity relation,
K-corrections, and extinction (but using wereR
B
\ 4.14)
applied to the photometry of 18 low-redshift SNe Ia
(z ¹ 0.1) from the supernova survey (HamuyCala
n/Tololo
et al. 1996) that were discovered earlier than 5 days after
peak. The light curves of these 18 supernovae have all been
reÐtted since P97, using the more recently available photo-
metry (Hamuy et al. 1996) and our K-corrections.
Figures 1 and 2a show the Hubble diagram of e†ective
rest-frame B magnitude corrected for the width-luminosity
relation,
m
B
eff \ m
R
] *
corr
[ K
BR
[ A
R
, (3)
as a function of redshift for the 42 Supernova Cosmology
Project high-redshift supernovae, along with the 18
low-redshift supernovae. (Here is theCala
n/Tololo K
BR
cross-Ðlter K-correction from observed R band to rest-
frame B band.) Tables 1 and 2 give the corresponding IAU
names, redshifts, magnitudes, corrected magnitudes, and
their respective uncertainties. As in P97, the inner error bars
in Figures 1 and 2 represent the photometric uncertainty,
while the outer error bars add in quadrature 0.17 mag of
intrinsic dispersion of SN Ia magnitudes that remain after
568 PERLMUTTER ET AL. Vol. 517
FIG. 1.ÈHubble diagram for 42 high-redshift type Ia supernovae from the Supernova Cosmology Project and 18 low-redshift type Ia supernovae from the
Supernova Survey after correcting both sets for the SN Ia light-curve width-luminosity relation. The inner error bars show the uncertainty dueCala
n/Tololo
to measurement errors, while the outer error bars show the total uncertainty when the intrinsic luminosity dispersion, 0.17 mag, of light-curveÈwidth-
corrected type Ia supernovae is added in quadrature. The unÐlled circles indicate supernovae not included in Ðt C. The horizontal error bars represent the
assigned peculiar velocity uncertainty of 300 km s~1. The solid curves are the theoretical for a range of cosmological models with zero cosmologicalm
B
eff(z)
constant: on top, (1, 0) in middle, and (2, 0) on bottom. The dashed curves are for a range of Ñat cosmological models: on()
M
, )
"
) \ (0, 0) ()
M
, )
"
) \ (0, 1)
top, (0.5, 0.5) second from top, (1, 0) third from top, and (1.5, [0.5) on bottom.
applying the width-luminosity correction. For these plots,
the slope of the width-brightness relation was taken to be
a \ 0.6, the best-Ðt value of Ðt C discussed below. (Since
both the low- and high-redshift supernova light-curve
widths are clustered rather closely around s \ 1, as shown
in Fig. 4, the exact choice of a does not change the Hubble
diagram signiÐcantly.) The theoretical curves for a universe
with no cosmological constant are shown as solid lines for a
range of mass density, 1, 2. The dashed lines)
M
\ 0,
represent alternative Ñat cosmologies, for which the total
mass energy density (where)
M
] )
"
\ 1 )
"
4 "/3H
0
2).
The range of models shown are for (0.5,()
M
, )
"
) \ (0, 1),
0.5), (1, 0), which is covered by the matching solid line, and
(1.5, [0.5).
3. FITS TO )
M
AND )
"
The combined low- and high-redshift supernova data sets
of Figure 1 are Ðtted to the Friedman-Robertson-Walker
(FRW) magnitude-redshift relation, expressed as in P97:
m
B
eff 4 m
R
] a(s [ 1) [ K
BR
[ A
R
\ M
B
] 5 log D
L
(z; )
M
, )
"
) , (4)
where is the ““ Hubble-constantÈfree ÏÏ lumi-D
L
4 H
0
d
L
nosity distance and log is theM
B
4 M
B
[ 5 H
0
] 25
““ Hubble-constantÈfree ÏÏ B-band absolute magnitude at
maximum of a SN Ia with width s \ 1. (These quantities
are, respectively, calculated from theory or Ðtted from
apparent magnitudes and redshifts, both without any need
for The cosmological-parameter results are thus alsoH
0
.
completely independent of The details of the ÐttingH
0
.)
procedure as presented in P97 were followed, except that
both the low- and high-redshift supernovae were Ðtted
simultaneously, so that and a, the slope of the width-M
B
luminosity relation, could also be Ðtted in addition to the
cosmological parameters and For most of the)
M
)
"
.
analyses in this paper, and a are statistical ““ nuisance ÏÏM
B
parameters; we calculate two-dimensional conÐdence
regions and single-parameter uncertainties for the cosmo-
logical parameters by integrating over these parameters, i.e.,
da.P()
M
, )
"
) \ // P()
M
, )
"
, M
B
, a)dM
B
As in P97, the small correlations between the photo-
metric uncertainties of the high-redshift supernovae, due to
shared calibration data, have been accounted for by Ðtting
with a correlation matrix of uncertainties.11 The low-
redshift supernova photometry is more likely to be uncor-
related in its calibration, since these supernovae were not
discovered in batches. However, we take a 0.01 mag system-
atic uncertainty in the comparison of the low-redshift
B-band photometry and the high-redshift R-band photo-
metry. The stretch-factor uncertainty is propagated with a
Ðxed width-luminosity slope (taken from the low-redshift
11 The data are available at http://www-supernova.lbl.gov.
No. 2, 1999 ) AND " FROM 42 HIGH-REDSHIFT SUPERNOVAE 569
FIG. 2.È(a) Hubble diagram for 42 high-redshift type Ia supernovae from the Supernova Cosmology Project and 18 low-redshift type Ia supernovae from
the Supernova Survey, plotted on a linear redshift scale to display details at high redshift. The symbols and curves are as in Fig. 1.Cala
n/Tololo
(b) Magnitude residuals from the best-Ðt Ñat cosmology for the Ðt C supernova subset, 0.72). The dashed curves are for a range of Ñat()
M
, )
"
) \ (0.28,
cosmological models: on top, (0.5, 0.5) third from bottom, (0.75, 0.25) second from bottom, and (1, 0) is the solid curve on bottom. The()
M
, )
"
) \ (0, 1)
middle solid curve is for Note that this plot is practically identical to the magnitude residual plot for the best-Ðt unconstrained cosmology()
M
, )
"
) \ (0, 0).
of Ðt C, with (c) Uncertainty-normalized residuals from the best-Ðt Ñat cosmology for the Ðt C supernova subset,()
M
, )
"
) \ (0.73, 1.32). ()
M
, )
"
) \
(0.28, 0.72).
supernovae; cf. P97) and checked for consistency after the
Ðt.
We have compared the results of Bayesian and classical,
““ frequentist,ÏÏ Ðtting procedures. For the Bayesian Ðts, we
have assumed a ““ prior ÏÏ probability distribution that has
zero probability for but otherwise has uniform)
M
\ 0
probability in the four parameters a, and For)
M
, )
"
, M
B
.
the frequentist Ðts, we have followed the classical statistical
procedures described by Feldman & Cousins (1998) to
guarantee frequentist coverage of our conÐdence regions in
the physically allowed part of parameter space. Note that
throughout the previous cosmology literature, completely
Citations
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Journal Article•DOI•
Planck 2018 results. VI. Cosmological parameters

[...]

Nabila Aghanim1, Yashar Akrami2, Yashar Akrami3, Yashar Akrami4  +229 more•Institutions (70)
01 Sep 2020-Astronomy and Astrophysics
TL;DR: In this article, the authors present cosmological parameter results from the full-mission Planck measurements of the cosmic microwave background (CMB) anisotropies, combining information from the temperature and polarization maps and the lensing reconstruction.
Abstract: We present cosmological parameter results from the final full-mission Planck measurements of the cosmic microwave background (CMB) anisotropies, combining information from the temperature and polarization maps and the lensing reconstruction Compared to the 2015 results, improved measurements of large-scale polarization allow the reionization optical depth to be measured with higher precision, leading to significant gains in the precision of other correlated parameters Improved modelling of the small-scale polarization leads to more robust constraints on manyparameters,withresidualmodellinguncertaintiesestimatedtoaffectthemonlyatthe05σlevelWefindgoodconsistencywiththestandard spatially-flat6-parameter ΛCDMcosmologyhavingapower-lawspectrumofadiabaticscalarperturbations(denoted“base ΛCDM”inthispaper), from polarization, temperature, and lensing, separately and in combination A combined analysis gives dark matter density Ωch2 = 0120±0001, baryon density Ωbh2 = 00224±00001, scalar spectral index ns = 0965±0004, and optical depth τ = 0054±0007 (in this abstract we quote 68% confidence regions on measured parameters and 95% on upper limits) The angular acoustic scale is measured to 003% precision, with 100θ∗ = 10411±00003Theseresultsareonlyweaklydependentonthecosmologicalmodelandremainstable,withsomewhatincreasederrors, in many commonly considered extensions Assuming the base-ΛCDM cosmology, the inferred (model-dependent) late-Universe parameters are: HubbleconstantH0 = (674±05)kms−1Mpc−1;matterdensityparameterΩm = 0315±0007;andmatterfluctuationamplitudeσ8 = 0811±0006 We find no compelling evidence for extensions to the base-ΛCDM model Combining with baryon acoustic oscillation (BAO) measurements (and consideringsingle-parameterextensions)weconstraintheeffectiveextrarelativisticdegreesoffreedomtobe Neff = 299±017,inagreementwith the Standard Model prediction Neff = 3046, and find that the neutrino mass is tightly constrained toPmν < 012 eV The CMB spectra continue to prefer higher lensing amplitudesthan predicted in base ΛCDM at over 2σ, which pulls some parameters that affect thelensing amplitude away from the ΛCDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAOdataThejointconstraintwithBAOmeasurementsonspatialcurvatureisconsistentwithaflatuniverse, ΩK = 0001±0002Alsocombining with Type Ia supernovae (SNe), the dark-energy equation of state parameter is measured to be w0 = −103±003, consistent with a cosmological constant We find no evidence for deviations from a purely power-law primordial spectrum, and combining with data from BAO, BICEP2, and Keck Array data, we place a limit on the tensor-to-scalar ratio r0002 < 006 Standard big-bang nucleosynthesis predictions for the helium and deuterium abundances for the base-ΛCDM cosmology are in excellent agreement with observations The Planck base-ΛCDM results are in good agreement with BAO, SNe, and some galaxy lensing observations, but in slight tension with the Dark Energy Survey’s combined-probe results including galaxy clustering (which prefers lower fluctuation amplitudes or matter density parameters), and in significant, 36σ, tension with local measurements of the Hubble constant (which prefer a higher value) Simple model extensions that can partially resolve these tensions are not favoured by the Planck data

4,688 citations

Journal Article•DOI•
Detection of the baryon acoustic peak in the large-scale correlation function of SDSS luminous red galaxies

[...]

Daniel J. Eisenstein1, Daniel J. Eisenstein2, Idit Zehavi2, David W. Hogg3, Roman Scoccimarro3, Michael R. Blanton3, Robert C. Nichol, Ryan Scranton4, Hee-Jong Seo2, Max Tegmark5, Max Tegmark6, Zheng Zheng7, Scott F. Anderson8, James Annis9, Neta A. Bahcall10, Jon Brinkmann11, Scott Burles5, Francisco J. Castander12, Andrew J. Connolly4, István Csabai13, Mamoru Doi14, Masataka Fukugita14, Joshua A. Frieman9, Joshua A. Frieman15, Karl Glazebrook16, James E. Gunn10, John S. Hendry9, Greg Hennessy, Zeljko Ivezic8, Stephen M. Kent9, Gillian R. Knapp10, Huan Lin9, Yeong Shang Loh17, Robert H. Lupton10, Bruce Margon18, Timothy A. McKay19, Avery Meiksin20, Jeffrey A. Munn, Adrian Pope16, Michael W. Richmond21, David J. Schlegel22, Donald P. Schneider23, Kazuhiro Shimasaku14, Chris Stoughton9, Michael A. Strauss10, Mark SubbaRao24, Mark SubbaRao15, Alexander S. Szalay16, István Szapudi25, Douglas L. Tucker9, Brian Yanny9, Donald G. York15 •
Sloan Fellows1, University of Arizona2, New York University3, University of Pittsburgh4, Massachusetts Institute of Technology5, University of Pennsylvania6, Institute for Advanced Study7, University of Washington8, Fermilab9, Princeton University10, Apache Corporation11, Spanish National Research Council12, Eötvös Loránd University13, University of Tokyo14, University of Chicago15, Johns Hopkins University16, University of Colorado Boulder17, Space Telescope Science Institute18, University of Michigan19, University of Edinburgh20, Rochester Institute of Technology21, Lawrence Berkeley National Laboratory22, Pennsylvania State University23, Adler Planetarium24, University of Hawaii25
10 Nov 2005-The Astrophysical Journal
TL;DR: In this paper, a large-scale correlation function measured from a spectroscopic sample of 46,748 luminous red galaxies from the Sloan Digital Sky Survey is presented, which demonstrates the linear growth of structure by gravitational instability between z ≈ 1000 and the present and confirms a firm prediction of the standard cosmological theory.
Abstract: We present the large-scale correlation function measured from a spectroscopic sample of 46,748 luminous red galaxies from the Sloan Digital Sky Survey. The survey region covers 0.72h −3 Gpc 3 over 3816 square degrees and 0.16 < z < 0.47, making it the best sample yet for the study of large-scale structure. We find a well-detected peak in the correlation function at 100h −1 Mpc separation that is an excellent match to the predicted shape and location of the imprint of the recombination-epoch acoustic oscillations on the low-redshift clustering of matter. This detection demonstrates the linear growth of structure by gravitational instability between z ≈ 1000 and the present and confirms a firm prediction of the standard cosmological theory. The acoustic peak provides a standard ruler by which we can measure the ratio of the distances to z = 0.35 and z = 1089 to 4% fractional accuracy and the absolute distance to z = 0.35 to 5% accuracy. From the overall shape of the correlation function, we measure the matter density mh 2 to 8% and find agreement with the value from cosmic microwave background (CMB) anisotropies. Independent of the constraints provided by the CMB acoustic scale, we find m = 0.273 ±0.025+0.123(1+ w0)+0.137K. Including the CMB acoustic scale, we find that the spatial curvature is K = −0.010 ± 0.009 if the dark energy is a cosmological constant. More generally, our results provide a measurement of cosmological distance, and hence an argument for dark energy, based on a geometric method with the same simple physics as the microwave background anisotropies. The standard cosmological model convincingly passes these new and robust tests of its fundamental properties. Subject headings: cosmology: observations — large-scale structure of the universe — distance scale — cosmological parameters — cosmic microwave background — galaxies: elliptical and lenticular, cD

4,428 citations

Journal Article•DOI•
Type Ia supernova discoveries at z > 1 from the Hubble Space Telescope: Evidence for past deceleration and constraints on dark energy evolution

[...]

Adam G. Riess1, Louis-Gregory Strolger1, John L. Tonry2, Stefano Casertano1, Henry C. Ferguson1, Bahram Mobasher1, Peter Challis3, Alexei V. Filippenko4, Saurabh Jha4, Weidong Li4, Ryan Chornock4, Robert P. Kirshner3, Bruno Leibundgut5, Mark Dickinson1, Mario Livio1, Mauro Giavalisco1, Charles C. Steidel6, Txitxo Benítez7, Zlatan Tsvetanov7 •
Space Telescope Science Institute1, University of Hawaii2, Harvard University3, University of California, Berkeley4, European Southern Observatory5, California Institute of Technology6, Johns Hopkins University7
01 Jun 2004-The Astrophysical Journal
TL;DR: For a flat universe with a cosmological constant, the transition between the two epochs is constrained to be at z = 0.46 ± 0.13 as mentioned in this paper, and w = -1.02 ± (and w < -0.76 at the 95% confidence level) for an assumed static equation of state of dark energy.
Abstract: We have discovered 16 Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to provide the first conclusive evidence for cosmic deceleration that preceded the current epoch of cosmic acceleration. These objects, discovered during the course of the GOODS ACS Treasury program, include 6 of the 7 highest redshift SNe Ia known, all at z > 1.25, and populate the Hubble diagram in unexplored territory. The luminosity distances to these objects and to 170 previously reported SNe Ia have been determined using empirical relations between light-curve shape and luminosity. A purely kinematic interpretation of the SN Ia sample provides evidence at the greater than 99% confidence level for a transition from deceleration to acceleration or, similarly, strong evidence for a cosmic jerk. Using a simple model of the expansion history, the transition between the two epochs is constrained to be at z = 0.46 ± 0.13. The data are consistent with the cosmic concordance model of ΩM ≈ 0.3, ΩΛ ≈ 0.7 (χ = 1.06) and are inconsistent with a simple model of evolution or dust as an alternative to dark energy. For a flat universe with a cosmological constant, we measure ΩM = 0.29 ± (equivalently, ΩΛ = 0.71). When combined with external flat-universe constraints, including the cosmic microwave background and large-scale structure, we find w = -1.02 ± (and w < -0.76 at the 95% confidence level) for an assumed static equation of state of dark energy, P = wρc2. Joint constraints on both the recent equation of state of dark energy, w0, and its time evolution, dw/dz, are a factor of ~8 more precise than the first estimates and twice as precise as those without the SNe Ia discovered with HST. Our constraints are consistent with the static nature of and value of w expected for a cosmological constant (i.e., w0 = -1.0, dw/dz = 0) and are inconsistent with very rapid evolution of dark energy. We address consequences of evolving dark energy for the fate of the universe.

4,236 citations

Journal Article•DOI•
Modified Gravity and Cosmology

[...]

Timothy Clifton1, Pedro G. Ferreira1, Antonio Padilla2, Constantinos Skordis2•
University of Oxford1, University of Nottingham2
01 Mar 2012-Physics Reports
TL;DR: A comprehensive survey of recent work on modified theories of gravity and their cosmological consequences can be found in this article, where the authors provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a selfcontained, comprehensive and up-to-date introduction to the subject as a whole.

3,674 citations

Journal Article•DOI•
Cosmological parameters from CMB and other data: A Monte Carlo approach

[...]

Antony Lewis, Sarah Bridle
25 Nov 2002-Physical Review D
TL;DR: In this paper, a fast Markov chain Monte Carlo exploration of cosmological parameter space is presented, which combines data from the CMB, HST Key Project, 2dF galaxy redshift survey, supernovae type Ia and big-bang nucleosynthesis.
Abstract: We present a fast Markov chain Monte Carlo exploration of cosmological parameter space. We perform a joint analysis of results from recent cosmic microwave background ~CMB! experiments and provide parameter constraints, including s 8, from the CMB independent of other data. We next combine data from the CMB, HST Key Project, 2dF galaxy redshift survey, supernovae type Ia and big-bang nucleosynthesis. The Monte Carlo method allows the rapid investigation of a large number of parameters, and we present results from 6 and 9 parameter analyses of flat models, and an 11 parameter analysis of non-flat models. Our results include constraints on the neutrino mass ( mn&0.3 eV), equation of state of the dark energy, and the tensor amplitude, as well as demonstrating the effect of additional parameters on the base parameter constraints. In a series of appendixes we describe the many uses of importance sampling, including computing results from new data and accuracy correction of results generated from an approximate method. We also discuss the different ways of converting parameter samples to parameter constraints, the effect of the prior, assess the goodness of fit and consistency, and describe the use of analytic marginalization over normalization parameters.

3,550 citations

References
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Journal Article•DOI•
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

[...]

Adam G. Riess1, Alexei V. Filippenko1, Peter Challis2, Alejandro Clocchiatti3, Alan H. Diercks4, Peter M. Garnavich2, R. L. Gilliland5, Craig J. Hogan4, Saurabh Jha2, Robert P. Kirshner2, Bruno Leibundgut6, Mark M. Phillips7, David J Reiss4, Brian P. Schmidt, R. A. Schommer7, R. Chris Smith7, R. Chris Smith8, Jason Spyromilio6, Christopher W. Stubbs4, Nicholas B. Suntzeff7, John L. Tonry9 •
University of California, Berkeley1, Harvard University2, Pontifical Catholic University of Chile3, University of Washington4, Space Telescope Science Institute5, European Southern Observatory6, Association of Universities for Research in Astronomy7, University of Michigan8, University of Hawaii9
01 Sep 1998-The Astronomical Journal
TL;DR: In this article, the authors used spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62.
Abstract: We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmo- logical parameters: the Hubble constant the mass density the cosmological constant (i.e., the (H 0 ), () M ), vacuum energy density, the deceleration parameter and the dynamical age of the universe ) " ), (q 0 ), ) M \ 1) methods. We estimate the dynamical age of the universe to be 14.2 ^ 1.7 Gyr including systematic uncer- tainties in the current Cepheid distance scale. We estimate the likely e†ect of several sources of system- atic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these e†ects appear to reconcile the data with and ) " \ 0 q 0 " 0.

16,674 citations

Journal Article•DOI•
Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds

[...]

David J. Schlegel1, Douglas P. Finkbeiner2, Marc Davis2•
Durham University1, University of California, Berkeley2
20 Jun 1998-The Astrophysical Journal
TL;DR: In this article, a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed, is presented.
Abstract: We present a full-sky 100 μm map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 μm data, we have constructed a map of the dust temperature so that the 100 μm map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of H2 in molecular clouds. In contrast, high-velocity H I clouds are deficient in dust emission, as expected. To generate the full-sky dust maps, we must first remove zodiacal light contamination, as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 μm DIRBE map against the Leiden-Dwingeloo map of H I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 μm flux. This procedure removes virtually all traces of the zodiacal foreground. For the 100 μm map no significant CIB is detected. At longer wavelengths, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 ± 13 nW m-2 sr-1 at 140 μm and of 17 ± 4 nW m-2 sr-1 at 240 μm (95% confidence). This integrated flux ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. To calibrate our maps, we assume a standard reddening law and use the colors of elliptical galaxies to measure the reddening per unit flux density of 100 μm emission. We find consistent calibration using the B-R color distribution of a sample of the 106 brightest cluster ellipticals, as well as a sample of 384 ellipticals with B-V and Mg line strength measurements. For the latter sample, we use the correlation of intrinsic B-V versus Mg2 index to tighten the power of the test greatly. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening. The maps are expected to be significantly more accurate in regions of high reddening. These dust maps will also be useful for estimating millimeter emission that contaminates cosmic microwave background radiation experiments and for estimating soft X-ray absorption. We describe how to access our maps readily for general use.

15,988 citations

Journal Article•DOI•
Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds

[...]

David J. Schlegel1, Douglas P. Finkbeiner2, Marc Davis2•
Durham University1, University of California, Berkeley2
28 Oct 1997-arXiv: Astrophysics
TL;DR: In this paper, the authors presented a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed.
Abstract: We present a full sky 100 micron map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 micron and 240 micron data, we have constructed a map of the dust temperature, so that the 100 micron map can be converted to a map proportional to dust column density. The result of these manipulations is a map with DIRBE-quality calibration and IRAS resolution. To generate the full sky dust maps, we must first remove zodiacal light contamination as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 micron DIRBE map against the Leiden- Dwingeloo map of H_I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 micron flux. For the 100 micron map, no significant CIB is detected. In the 140 micron and 240 micron maps, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 \pm 13 nW/m^2/sr at 140 micron, and 17 \pm 4 nW/m^2/sr at 240 micron (95% confidence). This integrated flux is ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles estimates in regions of low and moderate reddening. These dust maps will also be useful for estimating millimeter emission that contaminates CMBR experiments and for estimating soft X-ray absorption.

14,295 citations

Journal Article•DOI•
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

[...]

Adam G. Riess, Alexei V. Filippenko, Peter Challis, Alejandro Clocchiattia, Alan H. Diercks, Peter M. Garnavich, R. L. Gilliland, Craig J. Hogan, Saurabh Jha, Robert P. Kirshner, Bruno Leibundgut, Mark M. Phillips, David J Reiss, Brian P. Schmidt, Robert A. Schommer, R. Chris Smith, Jason Spyromilio, Christopher W. Stubbs, Nicholas B. Suntzeff, John L. Tonry 
15 May 1998-arXiv: Astrophysics
TL;DR: In this paper, the authors present observations of 10 type Ia supernovae (SNe Ia) between 0.16 0 and 4.0 sigma confidence levels, for two fitting methods respectively.
Abstract: We present observations of 10 type Ia supernovae (SNe Ia) between 0.16 0) and a current acceleration of the expansion (i.e., q_0 0, the spectroscopically confirmed SNe Ia are consistent with q_0 0 at the 3.0 sigma and 4.0 sigma confidence levels, for two fitting methods respectively. Fixing a ``minimal'' mass density, Omega_M=0.2, results in the weakest detection, Omega_Lambda>0 at the 3.0 sigma confidence level. For a flat-Universe prior (Omega_M+Omega_Lambda=1), the spectroscopically confirmed SNe Ia require Omega_Lambda >0 at 7 sigma and 9 sigma level for the two fitting methods. A Universe closed by ordinary matter (i.e., Omega_M=1) is ruled out at the 7 sigma to 8 sigma level. We estimate the size of systematic errors, including evolution, extinction, sample selection bias, local flows, gravitational lensing, and sample contamination. Presently, none of these effects reconciles the data with Omega_Lambda=0 and q_0 > 0.

14,295 citations

Journal Article•DOI•
The relationship between infrared, optical, and ultraviolet extinction

[...]

Jason A. Cardelli1, Geoffrey C. Clayton, John S. Mathis•
University of Wisconsin-Madison1
01 Oct 1989-The Astrophysical Journal
TL;DR: In this article, the average extinction law over the 3.5 micron to 0.125 wavelength range was derived for both diffuse and dense regions of the interstellar medium. And the validity of the law over a large wavelength interval suggests that the processes which modify the sizes and compositions of grains are stochastic in nature.
Abstract: The parameterized extinction data of Fitzpatrick and Massa (1986, 1988) for the ultraviolet and various sources for the optical and near-infrared are used to derive a meaningful average extinction law over the 3.5 micron to 0.125 wavelength range which is applicable to both diffuse and dense regions of the interstellar medium. The law depends on only one parameter R(V) = A(V)/E(B-V). An analytic formula is given for the mean extinction law which can be used to calculate color excesses or to deredden observations. The validity of the law over a large wavelength interval suggests that the processes which modify the sizes and compositions of grains are stochastic in nature and very efficient.

11,704 citations

Related Papers (5)
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

[...]

01 Sep 1998-The Astronomical Journal
Adam G. Riess, Alexei V. Filippenko, Peter Challis, Alejandro Clocchiatti, Alan H. Diercks, Peter M. Garnavich, R. L. Gilliland, Craig J. Hogan, Saurabh Jha, Robert P. Kirshner, Bruno Leibundgut, Mark M. Phillips, David J Reiss, Brian P. Schmidt, R. A. Schommer, R. Chris Smith, R. Chris Smith, Jason Spyromilio, Christopher W. Stubbs, Nicholas B. Suntzeff, John L. Tonry 
First year Wilkinson Microwave Anisotropy Probe (WMAP) observations: Determination of cosmological parameters

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01 Sep 2003-Astrophysical Journal Supplement Series
David N. Spergel, Licia Verde, Hiranya V. Peiris, Eiichiro Komatsu, M. R. Nolta, Charles L. Bennett, Mark Halpern, Gary Hinshaw, N. Jarosik, Alan J. Kogut, Michele Limon, Michele Limon, S. S. Meyer, Lyman A. Page, Gregory S. Tucker, Gregory S. Tucker, Gregory S. Tucker, Janet L. Weiland, Edward J. Wollack, Edward L. Wright 
Dynamics of dark energy

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08 Mar 2006-International Journal of Modern Physics D
Edmund J. Copeland, M. Sami, Shinji Tsujikawa
Type Ia supernova discoveries at z > 1 from the Hubble Space Telescope: Evidence for past deceleration and constraints on dark energy evolution

[...]

01 Jun 2004-The Astrophysical Journal
Adam G. Riess, Louis-Gregory Strolger, John L. Tonry, Stefano Casertano, Henry C. Ferguson, Bahram Mobasher, Peter Challis, Alexei V. Filippenko, Saurabh Jha, Weidong Li, Ryan Chornock, Robert P. Kirshner, Bruno Leibundgut, Mark Dickinson, Mario Livio, Mauro Giavalisco, Charles C. Steidel, Txitxo Benítez, Zlatan Tsvetanov 
The Cosmological Constant Problem

[...]

01 Jan 1989-Reviews of Modern Physics
Steven Weinberg
Frequently Asked Questions (11)
Q1. What are the contributions in this paper?

The authors report measurements of the mass density, and cosmological-constant energy density, of ) M, ) '', the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology Project. The authors discuss and constrain, where possible, hypothetical alternatives to a cosmological constant. The authors Ðnd no signiÐcant di†erences in either the host reddening distribution or Malmquist bias between the low-redshift sample Cala n/Tololo and their high-redshift sample. 

Thus the universe may be Ñat or there may be little or no cosmological constant, but the data are not consistent with both possibilities simultaneously. 2. presented here and future complementary data sets will allow us to explore these possibilities. For their purposes here the authors wish to distinguish between the true probability distribution, P ( A ), and its estimated or assumed distribution, often called the Bayesian prior, which they denote as P ( A ). Third, even if the universe is not Ñat, the conÐdence regions of Figure 7 suggest that the cosmological constant is a signiÐcant constituent of the energy density of the universe. 

Since there is evidence that dynamical estimates of depend on scale, the most appropriate measures to) Mcompare with their result are those obtained on large scales. 

The consistency of slopes in the light-curve widthluminosity relation for the low- and high-redshift supernovae can also constrain the possibility of a strong metallicity e†ect of the type that et al. 

due to small-scale clumping of mass as a separate analysis case rather than as a contributing systematic error in their primary analysis ; the total systematic uncertainty applies to this analysis as well. 

at high redshift the rest-frame B-band photometry is usually much more densely sampled in time than the rest-frame V -band data, so the authors use the stretch factor that best 

In brief, in this method the Gaussian extinction probability distribution implied by the measured colorexcess and its error is multiplied by an assumed a priori probability distribution (the Bayesian prior) for the intrinsic distribution of host extinctions. 

Since there is a small dependence of intrinsic color on the light-curve width, supernova colors can only be compared for the same stretch factor ; for a more convenient analysis, the authors subtract out the intrinsic colors so that the remaining color excesses can be compared simultaneously for all stretch factors. 

The best-Ðt mass-density in a Ñat universe for Ðt A is, within a fraction of the uncertainty, the same value as for Ðt B, (see Table 3). 

The best Ðts for the age of the universe for these analyses are H0 t0\\and To Ðrst order, the Reiss et0.90~0.05`0.07 H0 t0\\ 0.98~0.05`0.07.al. 

If in fact the universe has a dominant energy contribution from a cosmological constant, there are two coincidences that must be addressed in future cosmological theories.