29 research outputs found
SKYSURF-4: Panchromatic HST All-Sky Surface-Brightness Measurement Methods and Results
The diffuse, unresolved sky provides most of the photons that the Hubble
Space Telescope (HST) receives, yet remains poorly understood. HST Archival
Legacy program SKYSURF aims to measure the 0.2-1.6 m sky surface
brightness (sky-SB) from over 140,000 HST images. We describe a sky-SB
measurement algorithm designed for SKYSURF that is able to recover the input
sky-SB from simulated images to within 1% uncertainty. We present our sky-SB
measurements estimated using this algorithm on the entire SKYSURF database.
Comparing our sky-SB spectral energy distribution (SED) to measurements from
the literature shows general agreements. Our SKYSURF SED also reveals a
possible dependence on Sun angle, indicating either non-isotropic scattering of
solar photons off interplanetary dust or an additional component to Zodiacal
Light. Finally, we update Diffuse Light limits in the near-IR based on the
methods from Carleton et al. (2022), with values of 0.009 MJy sr (22 nW
m sr) at 1.25 m, 0.015 MJy sr (32 nW m
sr) at 1.4 m, and 0.013 MJy sr (25 nW m sr) at
1.6 m. These estimates provide the most stringent all-sky constraints to
date in this wavelength range. SKYSURF sky-SB measurements are made public on
the official SKYSURF website and will be used to constrain Diffuse Light in
future papers.Comment: Revised based on helpful comments from the reviewer, and accepted to
AJ on April 12th, 2023. Main paper: 18 pages, 9 figures, 4 tables.
Appendices: 16 pages, 10 figures, 1 table. Main results shown in Figure 7 and
Table
SKYSURF: Constraints on Zodiacal Light and Extragalactic Background Light through Panchromatic HST All-Sky Surface-Brightness Measurements: I. Survey Overview and Methods
We give an overview and describe the rationale, methods, and testing of the
Hubble Space Telescope (HST) Archival Legacy project "SKYSURF." SKYSURF uses
HST's unique capability as an absolute photometer to measure the ~0.2-1.7
m sky surface brightness (SB) from 249,861 WFPC2, ACS, and WFC3 exposures
in ~1400 independent HST fields. SKYSURF's panchromatic dataset is designed to
constrain the discrete and diffuse UV to near-IR sky components: Zodiacal Light
(ZL; inner Solar System), Kuiper Belt Objects (KBOs; outer Solar System),
Diffuse Galactic Light (DGL), and the discrete plus diffuse Extragalactic
Background Light (EBL). We outline SKYSURF's methods to: (1) measure sky-SB
levels between its detected objects; (2) measure the integrated discrete EBL,
most of which comes from AB17-22 mag galaxies; and (3) estimate how
much diffuse light may exist in addition to the extrapolated discrete galaxy
counts. Simulations of HST WFC3/IR images with known sky-values and gradients,
realistic cosmic ray (CR) distributions, and star plus galaxy counts were
processed with nine different algorithms to measure the "Lowest Estimated
Sky-SB" (LES) in each image between the discrete objects. The best algorithms
recover the inserted LES values within 0.2% when there are no image gradients,
and within 0.2-0.4% when there are 5-10% gradients. SKYSURF requires
non-standard re-processing of these HST images that includes restoring the
lowest sky-level from each visit into each drizzled image. We provide a proof
of concept of our methods from the WFC3/IR F125W images, where any residual
diffuse light that HST sees in excess of the Kelsall et al. (1998) Zodiacal
model prediction does not depend on the total object flux that each image
contains. This enables us to present our first SKYSURF results on diffuse light
in Carleton et al. (2022).Comment: Accepted to AJ; see accompanying paper Carleton et al. 2022:
arXiv:2205.06347. Comments welcome
A Retrospective Investigation of Sex Differences in Cognition in Children and Young Adults
The present study is a retrospective analysis to determine whether sex differences in cognition exist in children and young adults (i.e., those between 4 and 18 years of age) and to further identify when these differences emerge across cognitive development. A cross-sectional research design was used to analyze data previously collected by a third-party collaborator. Data (N = 8,184) was collected using the Cambridge Brain Science cognitive test battery, followed by a demographic questionnaire completed by participants’ parents or guardians. Data were analyzed using factorial analysis of variance with age and gender as fixed factors. The results demonstrate that females score higher in verbal and reasoning domains as well as in tasks measuring deductive reasoning and attention. Males score higher in the short-term memory domain and in tasks measuring their spatial short-term memory. The emergence of sex differences in cognition varied across tasks, either appearing at the elementary (4 to 9 years), middle (10 to 13 years), or high school (14 to 18 years) levels. The effect of sex was absent when controlling for cofounding variables. The findings demonstrate that females and males are more similar than different from a cognitive perspective
SKYSURF-4: Panchromatic Hubble Space Telescope All-Sky Surface-brightness Measurement Methods and Results
The diffuse, unresolved sky provides most of the photons that the Hubble Space Telescope (HST) receives, yet remains poorly understood. The HST Archival Legacy program SKYSURF aims to measure the 0.2–1.6 μ m sky surface brightness (sky-SB) from over 140,000 HST images. We describe a sky-SB measurement algorithm designed for SKYSURF that is able to recover the input sky-SB from simulated images to within 1% uncertainty. We present our sky-SB measurements estimated using this algorithm on the entire SKYSURF database. Comparing our sky-SB spectral energy distribution (SED) to measurements from the literature shows general agreements. Our SKYSURF SED also reveals a possible dependence on the Sun angle, indicating either nonisotropic scattering of solar photons off interplanetary dust or an additional component to zodiacal light. Finally, we update the diffuse light limits in the near-IR based on the methods from Carleton et al., with values of 0.009 MJy sr ^−1 (22 nW m ^−2 sr ^−1 ) at 1.25 μ m, 0.015 MJy sr ^−1 (32 nW m ^−2 sr ^−1 ) at 1.4 μ m, and 0.013 MJy sr ^−1 (25 nW m ^−2 sr ^−1 ) at 1.6 μ m. These estimates provide the most stringent all-sky constraints to date in this wavelength range. SKYSURF sky-SB measurements are made public on the official SKYSURF website and will be used to constrain diffuse light in future papers