27 research outputs found
Using ContentDM in a Consortium
In this session, staff from CLIC will discuss the decision process to purchase ContentDM for our digital collections and how the consortia agreed to divide costs and collections. We will also discuss customization of the site and give examples of how workflow is set up at some institutions
DeWitt Wallace Library Annual Report 2014-2015
Summary of library and media services activities for 2014-201
CCD detector performance for NOAO's wide-field MOSAIC cameras
In July of 1998 the National Optical Astronomy Observatories (NOAO) successfully upgraded MOSAIC 1, an 8192 by 8192 pixel array using eight Scientific Imaging Technologies, Inc. (SITe) St-002A thinned backside 2k by 4k charge coupled devices (CCDs). In July of 1999 MOSAIC II, a clone of MOSAIC I was commissioned also using eight SITe ST-002A CCDs. Additionally in December of 1998 NOAO implemented Mini- MOSAIC a 4096 by 4096 pixel array using two SITe ST-002A thinned CCDs. This report will discuss the performance, characterization and capabilities of the three wide field imagers now in operation at NOAO's Kitt Peak Observatory, Cerro Tololo Inter-American Observatory and at the WIYN Consortium 3.5-Meter telescope on Kitt Peak
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
We present observations of 10 type Ia supernovae (SNe Ia) between 0.16 < z <
0.62. With previous data from our High-Z Supernova Search Team, this expanded
set of 16 high-redshift supernovae and 34 nearby supernovae are used to place
constraints on the Hubble constant (H_0), the mass density (Omega_M), the
cosmological constant (Omega_Lambda), the deceleration parameter (q_0), and the
dynamical age of the Universe (t_0). The distances of the high-redshift SNe Ia
are, on average, 10% to 15% farther than expected in a low mass density
(Omega_M=0.2) Universe without a cosmological constant. Different light curve
fitting methods, SN Ia subsamples, and prior constraints unanimously favor
eternally expanding models with positive cosmological constant (i.e.,
Omega_Lambda > 0) and a current acceleration of the expansion (i.e., q_0 < 0).
With no prior constraint on mass density other than Omega_M > 0, the
spectroscopically confirmed SNe Ia are consistent with q_0 <0 at the 2.8 sigma
and 3.9 sigma confidence levels, and with Omega_Lambda >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.Comment: 36 pages, 13 figures, 3 table files Accepted to the Astronomical
Journa
Supernova Limits on the Cosmic Equation of State
We use Type Ia supernovae studied by the High-Z Supernova Search Team to
constrain the properties of an energy component which may have contributed to
accelerating the cosmic expansion. We find that for a flat geometry the
equation of state parameter for the unknown component, alpha_x=P_x/rho_x, must
be less than -0.55 (95% confidence) for any value of Omega_m and is further
limited to alpha_x<-0.60 (95%) if Omega_m is assumed to be greater than 0.1 .
These values are inconsistent with the unknown component being topological
defects such as domain walls, strings, or textures. The supernova data are
consistent with a cosmological constant (alpha_x=-1) or a scalar field which
has had, on average, an equation of state parameter similar to the cosmological
constant value of -1 over the redshift range of z=1 to the present. Supernova
and cosmic microwave background observations give complementary constraints on
the densities of matter and the unknown component. If only matter and vacuum
energy are considered, then the current combined data sets provide direct
evidence for a spatially flat Universe with Omega_tot=Omega_m+Omega_Lambda =
0.94 +/- 0.26 (1-sigma).Comment: Accepted for publication in ApJ, 3 figure
Cosmological Results from High-z Supernovae
The High-z Supernova Search Team has discovered and observed 8 new supernovae
in the redshift interval z=0.3-1.2. These independent observations, confirm the
result of Riess et al. (1998a) and Perlmutter et al. (1999) that supernova
luminosity distances imply an accelerating universe. More importantly, they
extend the redshift range of consistently observed SN Ia to z~1, where the
signature of cosmological effects has the opposite sign of some plausible
systematic effects. Consequently, these measurements not only provide another
quantitative confirmation of the importance of dark energy, but also constitute
a powerful qualitative test for the cosmological origin of cosmic acceleration.
We find a rate for SN Ia of 1.4+/-0.5E-04 h^3/Mpc^3/yr at a mean redshift of
0.5. We present distances and host extinctions for 230 SN Ia. These place the
following constraints on cosmological quantities: if the equation of state
parameter of the dark energy is w=-1, then H0 t0 = 0.96+/-0.04, and O_l - 1.4
O_m = 0.35+/-0.14. Including the constraint of a flat Universe, we find O_m =
0.28+/-0.05, independent of any large-scale structure measurements. Adopting a
prior based on the 2dF redshift survey constraint on O_m and assuming a flat
universe, we find that the equation of state parameter of the dark energy lies
in the range -1.48-1,
we obtain w<-0.73 at 95% confidence. These constraints are similar in precision
and in value to recent results reported using the WMAP satellite, also in
combination with the 2dF redshift survey.Comment: 50 pages, AAS LateX, 15 figures, 15 tables. Accepted for publication
by Astrophysical Journa
DeWitt Wallace Library Annual Report 2017-2018
Summary of library and media services activities for 2017-201
Imaging and Demography of the Host Galaxies of High-Redshift Type Ia Supernovae
We present the results of a study of the host galaxies of high redshift Type
Ia supernovae (SNe Ia). We provide a catalog of 18 hosts of SNe Ia observed
with the Hubble Space Telescope (HST) by the High-z Supernova Search Team
(HZT), including images, scale-lengths, measurements of integrated (Hubble
equivalent) BVRIZ photometry in bands where the galaxies are brighter than m ~
25 mag, and galactocentric distances of the supernovae. We compare the
residuals of SN Ia distance measurements from cosmological fits to measurable
properties of the supernova host galaxies that might be expected to correlate
with variable properties of the progenitor population, such as host galaxy
color and position of the supernova. We find mostly null results; the current
data are generally consistent with no correlations of the distance residuals
with host galaxy properties in the redshift range 0.42 < z < 1.06. Although a
subsample of SN hosts shows a formally significant (3-sigma) correlation
between apparent V-R host color and distance residuals, the correlation is not
consistent with the null results from other host colors probed by our largest
samples. There is also evidence for the same correlations between SN Ia
properties and host type at low redshift and high redshift. These similarities
support the current practice of extrapolating properties of the nearby
population to high redshifts pending more robust detections of any correlations
between distance residuals from cosmological fits and host properties.Comment: 35 pages, 12 figures, 4 tables, accepted for publication in A
Tests of the Accelerating Universe with Near-Infrared Observations of a High-Redshift Type Ia Supernova
We have measured the rest-frame B,V, and I-band light curves of a
high-redshift type Ia supernova (SN Ia), SN 1999Q (z=0.46), using HST and
ground-based near-infrared detectors.
A goal of this study is the measurement of the color excess, E_{B-I}, which
is a sensitive indicator of interstellar or intergalactic dust which could
affect recent cosmological measurements from high-redshift SNe Ia. Our
observations disfavor a 30% opacity of SN Ia visual light by dust as an
alternative to an accelerating Universe. This statement applies to both
Galactic-type dust
(rejected at the 3.4 sigma confidence level) and greyer dust (grain size >
0.1 microns; rejected at the 2.3 to 2.6 sigma confidence level) as proposed by
Aguirre (1999). The rest-frame -band light cur ve shows the secondary
maximum a month after B maximum typical of nearby SNe Ia of normal luminosi ty,
providing no indication of evolution as a function of redshift out to z~0.5. A
n expanded set of similar observations could improve the constraints on any
contribution of extragalactic dust to the dimming of high-redshift SNe Ia.Comment: Accepted to the Astrophysical Journal, 12 pages, 2 figure
CCD detector performance for NOAO's wide-field MOSAIC cameras
In July of 1998 the National Optical Astronomy Observatories (NOAO) successfully upgraded MOSAIC 1, an 8192 by 8192 pixel array using eight Scientific Imaging Technologies, Inc. (SITe) St-002A thinned backside 2k by 4k charge coupled devices (CCDs). In July of 1999 MOSAIC II, a clone of MOSAIC I was commissioned also using eight SITe ST-002A CCDs. Additionally in December of 1998 NOAO implemented Mini- MOSAIC a 4096 by 4096 pixel array using two SITe ST-002A thinned CCDs. This report will discuss the performance, characterization and capabilities of the three wide field imagers now in operation at NOAO's Kitt Peak Observatory, Cerro Tololo Inter-American Observatory and at the WIYN Consortium 3.5-Meter telescope on Kitt Peak