179 research outputs found
A Large Catalog of Accurate Distances to Molecular Clouds from PS1 Photometry
Distance measurements to molecular clouds are important but are often made separately for each cloud of interest, employing very different data and techniques. We present a large, homogeneous catalog of distances to molecular clouds, most of which are of unprecedented accuracy. We determine distances using optical photometry of stars along lines of sight toward these clouds, obtained from PanSTARRS-1. We simultaneously infer the reddenings and distances to these stars, tracking the full probability distribution function using a technique presented in Green et al. We fit these star-by-star measurements using a simple dust screen model to find the distance to each cloud. We thus estimate the distances to almost all of the clouds in the Magnani et al. catalog, as well as many other well-studied clouds, including Orion, Perseus, Taurus, Cepheus, Polaris, California, and Monoceros R2, avoiding only the inner Galaxy. Typical statistical uncertainties in the distances are 5%, though the systematic uncertainty stemming from the quality of our stellar models is about 10%. The resulting catalog is the largest catalog of accurate, directly measured distances to molecular clouds. Our distance estimates are generally consistent with available distance estimates from the literature, though in some cases the literature estimates are off by a factor of more than two
Cosmological Constraints from Measurements of Type Ia Supernovae discovered during the first 1.5 years of the Pan-STARRS1 Survey
We present griz light curves of 146 spectroscopically confirmed Type Ia
Supernovae () discovered during the first 1.5 years of the
Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is
determined by a combination of on-site measurements of the instrument response
function and observations of spectrophotometric standard stars. We find that
the systematic uncertainties in the photometric system are currently 1.2\%
without accounting for the uncertainty in the HST Calspec definition of the AB
system. A Hubble diagram is constructed with a subset of 113 out of 146 SNe Ia
that pass our light curve quality cuts. The cosmological fit to 310 SNe Ia (113
PS1 SNe Ia + 222 light curves from 197 low-z SNe Ia), using only SNe and
assuming a constant dark energy equation of state and flatness, yields
.
When combined with BAO+CMB(Planck)+, the analysis yields and including all
identified systematics (see also Scolnic et al. 2014). The value of is
inconsistent with the cosmological constant value of at the 2.3
level. Tension endures after removing either the BAO or the constraint,
though it is strongest when including the constraint. If we include WMAP9
CMB constraints instead of those from Planck, we find
, which diminishes the discord to . We
cannot conclude whether the tension with flat CDM is a feature of dark
energy, new physics, or a combination of chance and systematic errors. The full
Pan-STARRS1 supernova sample with 3 times as many SNe should provide
more conclusive results.Comment: 38 pages, 16 figures, 14 tables, ApJ in pres
Systematic Uncertainties Associated with the Cosmological Analysis of the First Pan-STARRS1 Type Ia Supernova Sample
We probe the systematic uncertainties from 113 Type Ia supernovae (SNIa) in
the Pan-STARRS1 (PS1) sample along with 197 SN Ia from a combination of
low-redshift surveys. The companion paper by Rest et al. (2013) describes the
photometric measurements and cosmological inferences from the PS1 sample. The
largest systematic uncertainty stems from the photometric calibration of the
PS1 and low-z samples. We increase the sample of observed Calspec standards
from 7 to 10 used to define the PS1 calibration system. The PS1 and SDSS-II
calibration systems are compared and discrepancies up to ~0.02 mag are
recovered. We find uncertainties in the proper way to treat intrinsic colors
and reddening produce differences in the recovered value of w up to 3%. We
estimate masses of host galaxies of PS1 supernovae and detect an insignificant
difference in distance residuals of the full sample of 0.037\pm0.031 mag for
host galaxies with high and low masses. Assuming flatness in our analysis of
only SNe measurements, we find . With additional constraints from BAO,
CMB(Planck) and H0 measurements, we find and
(statistical and systematic errors added in
quadrature). Significance of the inconsistency with depends on whether
we use Planck or WMAP measurements of the CMB:
.Comment: 24 pages, 20 figures. Accepted by Ap
- β¦