44 research outputs found
Default Parallels: The Science Potential Of JWST Parallel Observations During TSO Primary Observations
The James Webb Space Telescope (JWST) will observe several stars for long
cumulative durations while pursuing exoplanets as primary science targets for
both Guaranteed Time Observations (GTO) and very likely General Observer (GO)
programs. Here we argue in favor of an automatic default parallels program to
observe e.g., using the F200W/F277W filters or grism of NIRCAM/NIRISS in order
to find high redshift (z >> 10) galaxies, cool red/brown dwarf-sub-stellar
objects, Solar System objects, and observations of serendipitous planetary
transits. We argue here the need for automated exploratory astrophysical
observations with unused JWST instruments during these long duration exoplanet
observations. Randomized fields that are observed in parallel mode reduce
errors due to cosmic variance more effectively than single continuous fields of
a typical wedding cake observing strategy (Trenti & Stiavelli 2008). Hence, we
argue that the proposed automated survey will explore a unique and rich
discovery space in high redshift Universe, Galactic structure, and Solar
System. We show that the GTO and highly-probable GO target list of exoplanets
covers the Galactic disk/halo and high redshift Universe, mostly well out of
the plane of the disk of the Milky Way. Exposure times are of the order of the
CEERS GTO medium deep survey in a single filter, comparable to CANDELS in HST's
surveys and deep fields. The area covered by NIRISS and NIRCam combined could
accumulate to a half square degree surveyed.Comment: 19 pages, 5 figures, 2 tables, accepted for publication by PAS
Default parallels: The science potential of JWST parallel observations during TSO primary observations
The James Webb Space Telescope (JWST) will observe several stars for long cumulative durations while pursuing exoplanets as primary science targets for both Guaranteed Time Observations (GTO) and very likely General Observer (GO) programs. Here we argue in favor of an automatic default parallel program to observe, e.g., using the F200W/F277W filters or grism of NIRCAM/NIRISS in order to find high redshift (z (Formula Presented) 10) galaxies, cool red/brown dwarf substellar objects, solar system objects, and observations of serendipitous planetary transits. We argue here the need for automated exploratory astrophysical observations with unused JWST instruments during these long-duration exoplanet observations. Randomized fields that are observed in parallel mode reduce errors due to cosmic variance more effectively than single continuous fields of a typical wedding cake observing strategy. Hence, we argue that the proposed automated survey will explore a unique and rich discovery space in the high-redshift universe, Galactic structure, and solar system. We show that the GTO and highly probable GO target list of exoplanets covers the Galactic disk/halo and high redshift universe, mostly well out of the plane of the disk of the Milky Way. Exposure times are of the order of the CEERS GTO medium-deep survey in a single filter, comparable to CANDELS in Hubble Space Telescopeʼs surveys and deep fields. The area covered by NIRISS and NIRCam combined could accumulate to a half square degree surveyed
Unbiased Cosmological Parameter Estimation from Emission Line Surveys with Interlopers
The galaxy catalogs generated from low-resolution emission line surveys often
contain both foreground and background interlopers due to line
misidentification, which can bias the cosmological parameter estimation. In
this paper, we present a method for correcting the interloper bias by using the
joint-analysis of auto- and cross-power spectra of the main and the interloper
samples. In particular, we can measure the interloper fractions from the
cross-correlation between the interlopers and survey galaxies, because the true
cross-correlation must be negligibly small. The estimated interloper fractions,
in turn, remove the interloper bias in the cosmological parameter estimation.
For example, in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
low-redshift () [O II] {\AA} emitters contaminate
high-redshift () Lyman- line emitters. We demonstrate that
the joint-analysis method yields a high signal-to-noise ratio measurement of
the interloper fractions while only marginally increasing the uncertainties in
the cosmological parameters relative to the case without interlopers. We also
show the same is true for the high-latitude spectroscopic survey of Wide-Field
Infrared Survey Telescope (WFIRST) mission where contamination occurs between
the Balmer- line emitters at lower redshifts () and Oxygen
([O III] {\AA}) line emitters at higher redshifts ().Comment: 36 pages, 26 figure
The Sizes of z ∼ 9-10 Galaxies Identified in the Brightest of Reionizing Galaxies (BoRG) Survey
Redshift z = 9-10 object selection is the effective limit of Hubble Space Telescope (HST) imaging capability, even when confirmed with Spitzer. If only a few photometry data points are available, it becomes attractive to add criteria based on their morphology in these J- and H-band images. One could do so through visual inspection, a size criterion, or alternate morphometrics. We explore a vetted sample of Brightest of Reionizing Galaxies (BoRG) z ∼ 9 and z ∼ 10 candidate galaxies and the object rejected by Morishita+ to explore the utility of a size criterion in z = 9-10 candidate selection. A stringent, point-spread function (PSF)-corrected effective radius criterion (re \u3c 0″.3) would result in the rejection of 65%-70% of the interlopers visually rejected by Morishita et al. It may also remove up to ∼20% of bona fide brightest (L ≫ L∗) z = 9 or 10 candidates from a BoRG selected sample based on the Mason et al. luminosity functions, assuming the Holwerda et al. z ∼ 9 size-luminosity relation. We argue that including a size constraint in lieu of a visual inspection may serve in wide-field searches for these objects in, e.g., Euclid or HST archival imaging with the understanding that some brightest (L ≫ L∗) candidates may be missed. The sizes of the candidates found by Morishita et al. follow the expected size distribution of z ∼ 9 for bright galaxies, consistent with the log normal in Shibuya et al. and single objects. Two candidates show high star formation surface density (ΣSFR \u3e 25M⊙ kpc-2) and all merit further investigation and follow-up observations
The Sizes of Galaxies Identified in the BoRG Survey
Redshift object selection is the effective limit of Hubble Space
Telescope imaging capability, even when confirmed with Spitzer. If only a few
photometry data points are available, it becomes attractive to add criteria
based on their morphology in these J- and H-band images.
One could do so through visual inspection, a size criterion, or alternate
morphometrics. We explore a vetted sample of BoRG and
candidate galaxies and the object rejected by Morishita+ (2018) to explore the
utility of a size criterion in z=9-10 candidate selection. A stringent,
PSF-corrected effective radius criterion (r_e<0\farcs3) would result in the
rejection of 65-70\% of the interlopers visually rejected by Morishita+. It may
also remove up to \% of bona-fide brightest () z=9 or 10
candidates from a BoRG selected sample based on the Mason+ (2015) luminosity
functions, assuming the Holwerda+ (2015) size-luminosity relation. We
argue that including a size constraint in lieu of a visual inspection may serve
in wide-field searches for these objects in e.g. EUCLID or HST archival imaging
with the understanding that some brightest () candidates may be missed.
The sizes of the candidates found by Morishita+ (2018) follow the expected
size distribution of for bright galaxies, consistent with the
lognormal in Shibuya+ (2015) and single objects. Two candidates show high
star-formation surface density () and all
merit further investigation and follow-up observations.Comment: 9 Figures, 1 table, 13 pages, accepted for publication in The
Astronomical Journa