72 research outputs found
Propagating Uncertainties in the SALT3 Model Training Process to Cosmological Constraints
Type Ia supernovae (SNe Ia) are standardizable candles that must be modeled
empirically to yield cosmological constraints. To understand the robustness of
this modeling to variations in the model training procedure, we build an
end-to-end pipeline to test the recently developed SALT3 model. We explore the
consequences of removing pre-2000s low- or poorly calibrated -band data,
adjusting the amount and fidelity of SN Ia spectra, and using a
model-independent framework to simulate the training data. We find the SALT3
model surfaces are improved by having additional spectra and -band data, and
can be shifted by if host galaxy contamination is not sufficiently
removed from SN spectra. We find that resulting measurements of are
consistent to within for all training variants explored in this work,
with the largest shifts coming from variants that add color-dependent
calibration offsets or host galaxy contamination to the training spectra, and
those that remove pre-2000s low- data. These results demonstrate that the
SALT3 model training procedure is largely robust to reasonable variations in
the training data, but that additional attention must be paid to the treatment
of spectroscopic data in the training process. We also find that the training
procedure is sensitive to the color distributions of the input data; the
resulting measurement can be biased by if the color distribution
is not sufficiently wide. Future low- data, particularly -band
observations and high signal-to-noise ratio SN Ia spectra, will help to
significantly improve SN Ia modeling in the coming years.Comment: 16 pages, 10 figure
D/H Ratios on Saturn and Jupiter from Cassini CIRS
We present new measurements of the deuterium abundance on Jupiter and Saturn, showing evidence that Saturn's atmosphere contains less deuterium than Jupiter's. We analyzed far-infrared spectra from the Cassini Composite Infrared Spectrometer to measure the abundance of HD on both giant planets. Our estimate of the Jovian D/H = (2.95 ± 0.55) × 10−5 is in agreement with previous measurements by ISO/SWS: (2.25 ± 0.35) × 10−5, and the Galileo probe: (2.6 ± 0.7) × 10−5. In contrast, our estimate of the Saturn value of (2.10 ± 0.13) × 10−5 is somewhat lower than on Jupiter (by a factor of ), contrary to model predictions of a higher ratio: Saturn/Jupiter = 1.05–1.20. The Saturn D/H value is consistent with estimates for hydrogen in the protosolar nebula (2.1 ± 0.5) × 10−5, but its apparent divergence from the Jovian value suggests that our understanding of planetary formation and evolution is incomplete, which is in agreement with previous work.The US-based authors: J.E.D.P., C.A.N., G.L.B., R.K.A., B.E.H., and F.M.F. were supported by the NASA Cassini Mission during the period when this research was conducted. L.N.F. was supported by a Royal Society Research Fellowship at the University of Leicester. P.G.J.I. was supported by the United Kingdom Science and Technology Facilities Council.Peer-reviewedPublisher Versio
Evolution of the Mass-Metallicity Relation from Redshift to the Local Universe
A tight positive correlation between the stellar mass and the gas-phase
metallicity of galaxies has been observed at low redshifts. The redshift
evolution of this correlation can strongly constrain theories of galaxy
evolution. The advent of JWST allows probing the mass-metallicity relation at
redshifts far beyond what was previously accessible. Here we report the
discovery of two emission-line galaxies at redshifts 8.15 and 8.16 in JWST
NIRCam imaging and NIRSpec spectroscopy of targets gravitationally lensed by
the cluster RXJ2129.40005. We measure their metallicities and stellar masses
along with nine additional galaxies at to report the
first quantitative statistical inference of the mass-metallicity relation at
. We measure dex evolution in the normalization of the
mass-metallicity relation from to the local Universe; at fixed
stellar mass, galaxies are 8 times less metal enriched at
compared to the present day. Our inferred normalization is in agreement with
the predictions of the FIRE simulations. Our inferred slope of the
mass-metallicity relation is similar to or slightly shallower than that
predicted by FIRE or observed at lower redshifts. We compare the
galaxies to extremely low metallicity analog candidates in the local Universe,
finding that they are generally distinct from extreme emission-line galaxies or
"green peas" but are similar in strong emission-line ratios and metallicities
to "blueberry galaxies". Despite this similarity, at fixed stellar mass, the galaxies have systematically lower metallicities compared to
blueberry galaxies.Comment: Published in Ap
A search for transients in the Reionization Lensing Cluster Survey (RELICS): Three new supernovae
The Reionization Cluster Survey (RELICS) imaged 41 galaxy clusters with the
Hubble Space Telescope (HST), in order to detect lensed and high-redshift
galaxies. Each cluster was imaged to about 26.5 AB mag in three optical and
four near-infrared bands, taken in two distinct visits separated by varying
time intervals. We make use of the multiple near-infrared epochs to search for
transient sources in the cluster fields, with the primary motivation of
building statistics for bright caustic crossing events in gravitational arcs.
Over the whole sample, we do not find any significant ()
caustic crossing events, in line with expectations from semi-analytic
calculations but in contrast to what may be naively expected from previous
detections of some bright events, or from deeper transient surveys that do find
high rates of such events. Nevertheless, we find six prominent supernova (SN)
candidates over the 41 fields: three of them were previously reported and three
are new ones reported here for the first time. Out of the six candidates, four
are likely core-collapse (CC) SNe -- three in cluster galaxies, and among which
only one was known before, and one slightly behind the cluster at
. The other two are likely Ia -- both of them previously known,
one probably in a cluster galaxy, and one behind it at . Our study
supplies empirical bounds for the rate of caustic crossing events in galaxy
cluster fields to typical HST magnitudes, and lays the groundwork for a future
SN rate study.Comment: Accepted for publication in MNRAS. 10 pages, 3 figure
Spectroscopy from Lyman alpha to [O III] 5007 of a Triply Imaged Magnified Galaxy at Redshift z = 9.5
Given their extremely faint apparent brightness, the nature of the first
galaxies and how they reionized the Universe's gas are not yet understood. Here
we report the discovery, in James Webb Space Telescope (JWST) imaging, of a
highly magnified, low-mass (log(M_*/M_sol)=7.70^{+0.11}_{-0.09}) galaxy visible
when the Universe was only 510 Myr old, and follow-up prism spectroscopy of the
galaxy extending from Lyman alpha to [O III] 5007 in its rest frame. Our JWST
spectrum provides [O III] 5007 and H beta detections with a respective
signal-to-noise ratio (S/N) of 40 and 13, as well as six additional lines with
S/N > 3. These emission lines yield a redshift of z=9.51 and star-formation
rate of 2.12 +- 0.53 solar masses per year. The galaxy's large inferred value
of [O III]/[O II] = 16 +- 6 suggests that this galaxy has an escape fraction of
ionizing radiation larger than 10%, indicating that a population of similar
objects could contribute substantially to the reionization budget. Using
multiple techniques, we infer a gas oxygen abundance of 12 + log(O/H) = 7.48 +-
0.05 dex, consistent within 2 sigma of the mass-metallicity relation observed
for dwarf galaxies in the local Universe
The DEHVILS Survey Overview and Initial Data Release: High-Quality Near-Infrared Type Ia Supernova Light Curves at Low Redshift
While the sample of optical Type Ia Supernova (SN Ia) light curves (LCs)
usable for cosmological parameter measurements surpasses 2000, the sample of
published, cosmologically viable near-infrared (NIR) SN Ia LCs, which have been
shown to be good "standard candles," is still 200. Here, we present
high-quality NIR LCs for 83 SNe Ia ranging from as a part of
the Dark Energy, H, and peculiar Velocities using Infrared Light from
Supernovae (DEHVILS) survey. Observations are taken using UKIRT's WFCAM, where
the median depth of the images is 20.7, 20.1, and 19.3 mag (Vega) for , ,
and -bands, respectively. The median number of epochs per SN Ia is 18 for
all three bands () combined and 6 for each band individually. We fit 47 SN
Ia LCs that pass strict quality cuts using three LC models, SALT3, SNooPy, and
BayeSN and find scatter on the Hubble diagram to be comparable to or better
than scatter from optical-only fits in the literature. Fitting NIR-only LCs, we
obtain standard deviations ranging from 0.128-0.135 mag. Additionally, we
present a refined calibration method for transforming 2MASS magnitudes to WFCAM
magnitudes using HST CALSPEC stars that results in a 0.03 mag shift in the
WFCAM -band magnitudes.Comment: 24 pages, 9 figures. Accepted by MNRA
Models and simulations for the photometric lsst astronomical time series classification challenge (Plasticc)
We describe the simulated data sample for the "Photometric LSST Astronomical Time Series Classification Challenge" (PLAsTiCC), a publicly available challenge to classify transient and variable events that will be observed by the Large Synoptic Survey Telescope (LSST), a new facility expected to start in the early 2020s. The challenge was hosted by Kaggle, ran from 2018 September 28 to 2018 December 17, and included 1,094 teams competing for prizes. Here we provide details of the 18 transient and variable source models, which were not revealed until after the challenge, and release the model libraries at this https URL. We describe the LSST Operations Simulator used to predict realistic observing conditions, and we describe the publicly available SNANA simulation code used to transform the models into observed fluxes and uncertainties in the LSST passbands (ugrizy). Although PLAsTiCC has finished, the publicly available models and simulation tools are being used within the astronomy community to further improve classification, and to study contamination in photometrically identified samples of type Ia supernova used to measure properties of dark energy. Our simulation framework will continue serving as a platform to improve the PLAsTiCC models, and to develop new models
LensWatch: I. Resolved HST Observations and Constraints on the Strongly-Lensed Type Ia Supernova 2022qmx ("SN Zwicky")
Supernovae (SNe) that have been multiply-imaged by gravitational lensing are
rare and powerful probes for cosmology. Each detection is an opportunity to
develop the critical tools and methodologies needed as the sample of lensed SNe
increases by orders of magnitude with the upcoming Vera C. Rubin Observatory
and Nancy Grace Roman Space Telescope. The latest such discovery is of the
quadruply-imaged Type Ia SN 2022qmx (aka, "SN Zwicky"; Goobar et al. 2022) at z
= 0.3544. SN Zwicky was discovered by the Zwicky Transient Facility (ZTF) in
spatially unresolved data. Here we present follow-up Hubble Space Telescope
observations of SN Zwicky, the first from the multi-cycle "LensWatch" program
(www.lenswatch.org). We measure photometry for each of the four images of SN
Zwicky, which are resolved in three WFC3/UVIS filters (F475W, F625W, F814W) but
unresolved with WFC3/IR F160W, and produce an analysis of the lensing system
using a variety of independent lens modeling methods. We find consistency
between time delays estimated with the single epoch of HST photometry and the
lens model predictions constrained through the multiple image positions, with
both inferring time delays of <1 day. Our lens models converge to an Einstein
radius of (0.168+0.009-0.005)", the smallest yet seen in a lensed SN. The
"standard candle" nature of SN Zwicky provides magnification estimates
independent of the lens modeling that are brighter by ~1.5 mag and ~0.8 mag for
two of the four images, suggesting significant microlensing and/or additional
substructure beyond the flexibility of our image-position mass models
Spectroscopy of the Supernova H0pe Host Galaxy at Redshift 1.78
Supernova (SN) H0pe was discovered as a new transient in James Webb Space
Telescope (JWST) NIRCam images of the galaxy cluster PLCK G165.7+67.0 taken as
part of the "Prime Extragalactic Areas for Reionization and Lensing Science"
(PEARLS) JWST GTO program (# 1176) on 2023 March 30 (AstroNote 2023-96; Frye et
al. 2023). The transient is a compact source associated with a background
galaxy that is stretched and triply-imaged by the cluster's strong
gravitational lensing. This paper reports spectra in the 950-1370 nm observer
frame of two of the galaxy's images obtained with Large Binocular Telescope
(LBT) Utility Camera in the Infrared (LUCI) in longslit mode two weeks after
the \JWST\ observations. The individual average spectra show the [OII] doublet
and the Balmer and 4000 Angstrom breaks at redshift z=1.783+/-0.002. The CIGALE
best-fit model of the spectral energy distribution indicates that SN H0pe's
host galaxy is massive (Mstar~6x10^10 Msun after correcting for a magnification
factor ~7) with a predominant intermediate age (~2 Gyr) stellar population,
moderate extinction, and a magnification-corrected star formation rate ~13
Msun/yr, consistent with being below the main sequence of star formation. These
properties suggest that H0pe might be a type Ia SN. Additional observations of
SN H0pe and its host recently carried out with JWST (JWST-DD-4446; PI: B. Frye)
will be able to both determine the SN classification and confirm its
association with the galaxy analyzed in this work.Comment: 6 pages, 4 figures, Letter accepted for publication in Astronomy &
Astrophysic
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