19 research outputs found
A Spitzer Five-Band Analysis of the Jupiter-Sized Planet TrES-1
With an equilibrium temperature of 1200 K, TrES-1 is one of the coolest hot
Jupiters observed by {\Spitzer}. It was also the first planet discovered by any
transit survey and one of the first exoplanets from which thermal emission was
directly observed. We analyzed all {\Spitzer} eclipse and transit data for
TrES-1 and obtained its eclipse depths and brightness temperatures in the 3.6
{\micron} (0.083 % {\pm} 0.024 %, 1270 {\pm} 110 K), 4.5 {\micron} (0.094 %
{\pm} 0.024 %, 1126 {\pm} 90 K), 5.8 {\micron} (0.162 % {\pm} 0.042 %, 1205
{\pm} 130 K), 8.0 {\micron} (0.213 % {\pm} 0.042 %, 1190 {\pm} 130 K), and 16
{\micron} (0.33 % {\pm} 0.12 %, 1270 {\pm} 310 K) bands. The eclipse depths can
be explained, within 1 errors, by a standard atmospheric model with
solar abundance composition in chemical equilibrium, with or without a thermal
inversion. The combined analysis of the transit, eclipse, and radial-velocity
ephemerides gives an eccentricity , consistent
with a circular orbit. Since TrES-1's eclipses have low signal-to-noise ratios,
we implemented optimal photometry and differential-evolution Markov-chain Monte
Carlo (MCMC) algorithms in our Photometry for Orbits, Eclipses, and Transits
(POET) pipeline. Benefits include higher photometric precision and \sim10 times
faster MCMC convergence, with better exploration of the phase space and no
manual parameter tuning.Comment: 17 pages, Accepted for publication in Ap
Tidal Features at 0.05<z<0.45 in the Hyper Suprime-Cam Subaru Strategic Program: Properties and Formation Channels
We present 1,201 galaxies at that host tidal features, detected
from the first deg of imaging from the Hyper Suprime-Cam
Subaru Strategic Program (HSC-SSP). All galaxies in the present sample have
spectroscopic observations from the Sloan Digital Sky Survey (SDSS)
spectroscopic campaigns, generating a sample of 21208 galaxies. Of these
galaxies, we identify 214 shell systems and 987 stream systems. For 575 of
these systems, we are additionally able to measure the colors of the
tidal features. We find evidence for star formation in a subset of the streams,
with the exception of streams around massive ellipticals, and find that stream
host galaxies span the full range of stellar masses in our sample. Galaxies
which host shells are predominantly red and massive: we find that observable
shells form more frequently around ellipticals than around disc galaxies of the
same stellar mass. Although the majority of the shells in our sample are
consistent with being formed by minor mergers, of shell host
galaxies have colors as red as their host galaxy, consistent with being
formed by major mergers. These "red shells" are additionally preferentially
aligned with the major axis of the host galaxy, as previously predicted from
simulations. We suggest that although the bulk of the observable shell
population originates from fairly minor mergers, which preferentially form
shells that are not aligned with the major axis of the galaxy, major mergers
produce a significant number of observable shells.Comment: 24 pages, 14 figures. Submitted to Ap
Possible thermochemical disequilibrium in the atmosphere of the exoplanet GJ 436b
The nearby extrasolar planet GJ 436b--which has been labelled as a 'hot
Neptune'--reveals itself by the dimming of light as it crosses in front of and
behind its parent star as seen from Earth. Respectively known as the primary
transit and secondary eclipse, the former constrains the planet's radius and
mass, and the latter constrains the planet's temperature and, with measurements
at multiple wavelengths, its atmospheric composition. Previous work using
transmission spectroscopy failed to detect the 1.4-\mu m water vapour band,
leaving the planet's atmospheric composition poorly constrained. Here we report
the detection of planetary thermal emission from the dayside of GJ 436b at
multiple infrared wavelengths during the secondary eclipse. The best-fit
compositional models contain a high CO abundance and a substantial methane
(CH4) deficiency relative to thermochemical equilibrium models for the
predicted hydrogen-dominated atmosphere. Moreover, we report the presence of
some H2O and traces of CO2. Because CH4 is expected to be the dominant
carbon-bearing species, disequilibrium processes such as vertical mixing and
polymerization of methane into substances such as ethylene may be required to
explain the hot Neptune's small CH4-to-CO ratio, which is at least 10^5 times
smaller than predicted
The Hyper Suprime-Cam Software Pipeline
In this paper, we describe the optical imaging data processing pipeline
developed for the Subaru Telescope's Hyper Suprime-Cam (HSC) instrument. The
HSC Pipeline builds on the prototype pipeline being developed by the Large
Synoptic Survey Telescope's Data Management system, adding customizations for
HSC, large-scale processing capabilities, and novel algorithms that have since
been reincorporated into the LSST codebase. While designed primarily to reduce
HSC Subaru Strategic Program (SSP) data, it is also the recommended pipeline
for reducing general-observer HSC data. The HSC pipeline includes high level
processing steps that generate coadded images and science-ready catalogs as
well as low-level detrending and image characterizations.Comment: 39 pages, 21 figures, 2 tables. Submitted to Publications of the
Astronomical Society of Japa
Two nearby sub-Earth-sized exoplanet candidates in the GJ 436 system
We report the detection of UCF-1.01, a strong exoplanet candidate with a
radius 0.66 +/- 0.04 times that of Earth (R_{\oplus}). This sub-Earth-sized
planet transits the nearby M-dwarf star GJ 436 with a period of 1.365862 +/-
8x10^{-6} days. We also report evidence of a 0.65 +/- 0.06 R_{\oplus} exoplanet
candidate (labeled UCF-1.02) orbiting the same star with an undetermined
period. Using the Spitzer Space Telescope, we measure the dimming of light as
the planets pass in front of their parent star to assess their sizes and
orbital parameters. If confirmed, UCF-1.01 and UCF-1.02 would be called GJ 436c
and GJ 436d, respectively, and would be part of the first
multiple-transiting-planet system outside of the Kepler field. Assuming
Earth-like densities of 5.515 g/cm^3, we predict both candidates to have
similar masses (~0.28 Earth-masses, M_{\oplus}, 2.6 Mars-masses) and surface
gravities of ~0.65 g (where g is the gravity on Earth). UCF-1.01's equilibrium
temperature (T_{eq}, where emitted and absorbed radiation balance for an
equivalent blackbody) is 860 K, making the planet unlikely to harbor life as on
Earth. Its weak gravitational field and close proximity to its host star imply
that UCF-1.01 is unlikely to have retained its original atmosphere; however, a
transient atmosphere is possible if recent impacts or tidal heating were to
supply volatiles to the surface. We also present additional observations of GJ
436b during secondary eclipse. The 3.6-micron light curve shows indications of
stellar activity, making a reliable secondary eclipse measurement impossible. A
second non-detection at 4.5 microns supports our previous work in which we find
a methane-deficient and carbon monoxide-rich dayside atmosphere.Comment: Accepted for publication with Ap
High C/O Chemistry and Weak Thermal Inversion in the Extremely Irradiated Atmosphere of Exoplanet WASP-12b
The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior as opposed to the silicate-dominated composition as found on Earth; the solar C/O is 0.54. Theory, shows that high C/O leads to a diversity of carbon-rich planets that can have very different interiors and atmospheres from those in the solar system. Here we report the detection of C/O greater than or equal to 1 in a planetary atmosphere. The transiting hot Jupiter WASP-12b has a dayside atmosphere depleted in water vapour and enhanced in methane by over two orders of magnitude compared to a solar-abundance chemical equilibrium model at the expected temperatures. The observed concentrations of the prominent molecules CO, CH4, and H2O are consistent with theoretical expectations for an atmosphere with the observed C/O = 1. The C/O ratios are not known for giant planets in the solar system, although they are expected to equal the solar value. If high C/O ratios are common, then extrasolar planets are likely very different in interior composition, and formed very differently, from expectations based on solar composition, potentially explaining the large diversity in observed radii. We also find that the extremely irradiated atmosphere (greater than 2500 K) of WASP-12b lacks a prominent thermal inversion, or a stratosphere, and has very efficient day-night energy circulation. The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres
Hyper Suprime-Cam Year 3 Results: Cosmology from Cosmic Shear Two-point Correlation Functions
We perform a blinded cosmology analysis with cosmic shear two-point
correlation functions (2PCFs) measured from more than 25 million galaxies in
the Hyper Suprime-Cam three-year shear catalog in four tomographic redshift
bins ranging from 0.3 to 1.5. After conservative masking and galaxy selection,
the survey covers 416 deg of the northern sky with an effective galaxy
number density of 15 arcmin over the four redshift bins. The 2PCFs
adopted for cosmology analysis are measured in the angular range: for and
for , with a total signal-to-noise ratio of 26.6. We apply a
conservative, wide, flat prior on the photometric redshift errors on the last
two tomographic bins, and the relative magnitudes of the cosmic shear amplitude
across four redshift bins allow us to calibrate the photometric redshift
errors. With this flat prior on redshift errors, we find and (both 68\% CI) for a flat cold dark
matter cosmology. We find, after unblinding, that our constraint on is
consistent with the Fourier space cosmic shear and the 32pt analyses on
the same HSC dataset. We carefully study the potential systematics from
astrophysical and systematic model uncertainties in our fiducial analysis using
synthetic data, and report no biases (including projection bias in the
posterior space) greater than in the estimation of . Our
analysis hints that the mean redshifts of the two highest tomographic bins are
higher than initially estimated. In addition, a number of consistency tests are
conducted to assess the robustness of our analysis. Comparing our result with
Planck-2018 cosmic microwave background observations, we find a ~
tension for the CDM model.Comment: 38 pages, 32 figures, 4 tables (PRD in press.
Hyper Suprime-Cam Year 3 results: cosmology from cosmic shear power spectra
We measure weak lensing cosmic shear power spectra from the 3-year galaxy shear catalog of the Hyper Suprime-Cam (HSC) Subaru Strategic Program imaging survey. The shear catalog covers 416 deg2 of the northern sky, with a mean i-band seeing of 0.59 arcsec and an effective galaxy number density of 15 arcmin−2 within our adopted redshift range. With an i-band magnitude limit of 24.5 mag, and four tomographic redshift bins spanning 0.3≤zph≤1.5 based on photometric redshifts, we obtain a high-significance measurement of the cosmic shear power spectra, with a signal-to-noise ratio of approximately 26.4 in the multipole range 300<ℓ<1800. The accuracy of our power spectrum measurement is tested against realistic mock shear catalogs, and we use these catalogs to get a reliable measurement of the covariance of the power spectrum measurements. We use a robust blinding procedure to avoid confirmation bias, and model various uncertainties and sources of bias in our analysis, including point spread function systematics, redshift distribution uncertainties, the intrinsic alignment of galaxies and the modeling of the matter power spectrum. For a flat ΛCDM model, we find S8≡σ8(Ωm/0.3)0.5=0.776+0.032−0.033, which is in excellent agreement with the constraints from the other HSC Year 3 cosmology analyses, as well as those from a number of other cosmic shear experiments. This result implies a ∼2σ-level tension with the Planck 2018 cosmology. We study the effect that various systematic errors and modeling choices could have on this value, and find that they can shift the best-fit value of S8 by no more than ∼0.5σ, indicating that our result is robust to such systematics