Space Telescope Research Articles

JWST Photometric Time-delay and Magnification Measurements for the Triply Imaged Type Ia “SN H0pe” at z = 1.78

Supernova (SN) SN H0pe is a gravitationally lensed, triply imaged, Type Ia SN (SN Ia) discovered in James Webb Space Telescope imaging of the PLCK G165.7+67.0 cluster of galaxies. Well-observed multiply imaged SNe provide a rare opportunity to constrain the Hubble constant (H 0), by measuring the relative time delay between the images and modeling the foreground mass distribution. SN H0pe is located at z = 1.783 and is the first SN Ia with sufficient light-curve sampling and long enough time delays for an H 0 inference. Here we present photometric time-delay measurements and SN properties of SN H0pe. Using JWST/NIRCam photometry, we measure time delays of Δt ab = −116.6−9.3+10.8 observer-frame days and Δt cb = −48.6−4.0+3.6 observer-frame days relative to the last image to arrive (image 2b; all uncertainties are 1σ), which corresponds to a ∼5.6% uncertainty contribution for H 0 assuming 70 km s−1 Mpc−1. We also constrain the absolute magnification of each image to μ a = 4.3−1.8+1.6 , μ b = 7.6−2.6+3.6 , μ c = 6.4−1.5+1.6 by comparing the observed peak near-IR magnitude of SN H0pe to the nonlensed population of SNe Ia.

Mid-infrared Fine Structure Lines from the Galactic Warm Ionized Medium

The Warm Ionized Medium (WIM) hosts most of the ionized gas in the Galaxy and occupies perhaps a quarter of the volume of the Galactic disk. Decoding the spectrum of the Galactic diffuse ionizing field is of fundamental interest. This can be done via direct measurements of ionization fractions of various elements. Based on current physical models for the WIM we predicted that mid-IR fine structure lines of Ne, Ar and S would be within the grasp of the Mid-Infrared Imager-Medium Resolution Spectrometer (MIRI-MRS), an Integral Field Unit (IFU) spectrograph, aboard the James Webb Space Telescope (JWST). Motivated thus we analyzed a pair of commissioning data sets and detected [Ne ii] 12.81 μm, [S iii] 18.71 μm and possibly [S iv] 10.51 μm. The inferred emission measure for these detections is about 10 cm−6 pc, typical of the WIM. These detections are broadly consistent with expectations of physical models for the WIM. The current detections are limited by uncorrected fringing (and to a lesser extent by baseline variations). In due course, we expect, as with other IFUs, the calibration pipeline to deliver photon-noise-limited spectra. The detections reported here bode well for the study of the WIM. Along most lines-of-sight hour-long MIRI-MRS observations should detect line emission from the WIM. When combined with optical observations by modern IFUs with high spectral resolution on large ground-based telescopes, the ionization fraction and temperature of neon and sulfur can be robustly inferred. Separately, the ionization of helium in the WIM can be probed by NIRspec. Finally, joint JWST and optical IFU studies will open up a new cottage industry of studying the WIM on arcsecond scales.

Deep Hubble Space Telescope Photometry of Large Magellanic Cloud and Milky Way Ultrafaint Dwarfs: A Careful Look into the Magnitude–Size Relation

We present deep Hubble Space Telescope photometry of 10 targets from Treasury Program GO-14734, including six confirmed ultrafaint dwarf (UFD) galaxies, three UFD candidates, and one likely globular cluster. Six of these targets are satellites of, or have interacted with, the Large Magellanic Cloud (LMC). We determine their structural parameters using a maximum-likelihood technique. Using our newly derived half-light radius (r h ) and V-band magnitude (M V ) values in addition to literature values for other UFDs, we find that UFDs associated with the LMC do not show any systematic differences from Milky Way UFDs in the magnitude–size plane. Additionally, we convert simulated UFD properties from the literature into the M V –r h observational space to examine the abilities of current dark matter (DM) and baryonic simulations to reproduce observed UFDs. Some of these simulations adopt alternative DM models, thus allowing us to also explore whether the M V –r h plane could be used to constrain the nature of DM. We find no differences in the magnitude–size plane between UFDs simulated with cold, warm, and self-interacting DM, but note that the sample of UFDs simulated with alternative DM models is quite limited at present. As more deep, wide-field survey data become available, we will have further opportunities to discover and characterize these ultrafaint stellar systems and the greater low surface-brightness universe.

A proposal for a fast infrared bursts detector

The gravitational wave GW170817 from a binary neutron star merger and the simultaneous electromagnetic detection of the GRB170717A by Fermi Gamma-Ray Space Telescope, opened a new era in the multi-messenger astronomy. Furthermore, the GRBs (Gamma-Ray Bursts) and the mysterious FRBs (Fast Radio Bursts) have sparked interest in the development of new detectors and telescopes dedicated to the time-domain astronomy across the electromagnetic spectrum. Time-domain astronomy aims to acquire fast astronomical bursts in temporal range between a few seconds down to 1 ns. Fast InfraRed Bursts (FIRB's) have been relatively understudied, often due to the lack of appropriate tools for observation and analysis. In this scientific scenario, the present contribution proposes a new detection system for ground-based reflecting telescopes working in the mid-infrared (mid-IR) range to search for astronomical FIRB's. Experience developed in the diagnostics for lepton circular accelerators can be used to design temporal devices for astronomy. Longitudinal diagnostic instruments acquire bunch-by-bunch particle shifts in the direction of flight, that is equivalent to temporal. Transverse device integrates the beam signal in the horizontal and vertical coordinates, as standard telescopes. The proposed instrument aims to work in temporal mode. Feasibility study tests have been carried out at SINBAD, the infrared beam line of DAFNE, the e+e- collider of INFN. SINBAD releases pulsed infrared synchrotron light with 2.7 ns separation. The front-end detector system has been evaluated to detect temporal fast infrared signals with 2–12 μm wavelengths and 1 ns rise times. The present contribute aims to be a step toward a feasibility study report.

Forecasts for Galaxy Formation and Dark Matter Constraints from Dwarf Galaxy Surveys

The abundance of faint dwarf galaxies is determined by the underlying population of low-mass dark matter (DM) halos and the efficiency of galaxy formation in these systems. Here, we quantify potential galaxy formation and DM constraints from future dwarf satellite galaxy surveys. We generate satellite populations using a suite of Milky Way (MW)–mass cosmological zoom-in simulations and an empirical galaxy–halo connection model, and assess sensitivity to galaxy formation and DM signals when marginalizing over galaxy–halo connection uncertainties. We find that a survey of all satellites around one MW-mass host can constrain a galaxy formation cutoff at peak virial masses of M50=108M⊙ at the 1σ level; however, a tail toward low M50 prevents a 2σ measurement. In this scenario, combining hosts with differing bright satellite abundances significantly reduces uncertainties on M50 at the 1σ level, but the 2σ tail toward low M50 persists. We project that observations of one (two) complete satellite populations can constrain warm DM models with m WDM ≈ 10 keV (20 keV). Subhalo mass function (SHMF) suppression can be constrained to ≈70%, 60%, and 50% that in cold dark matter (CDM) at peak virial masses of 108, 109, and 1010 M ⊙, respectively; SHMF enhancement constraints are weaker (≈20, 4, and 2 times that in CDM, respectively) due to galaxy–halo connection degeneracies. These results motivate searches for faint dwarf galaxies beyond the MW and indicate that ongoing missions like Euclid and upcoming facilities including the Vera C. Rubin Observatory and Nancy Grace Roman Space Telescope will probe new galaxy formation and DM physics.

HST Survey of the Orion Nebula Cluster in ACS/Visible and WFC3/IR Bands. IV. A Bayesian Multiwavelength Study of Stellar Parameters in the Orion Nebula Cluster

We have performed a comprehensive study of the Orion Nebula Cluster (ONC) combining the photometric data obtained by the two Hubble Space Telescope Treasury programs that targeted this region. To consistently analyze the rich data set obtained in a wide variety of filters, we adopted a Bayesian approach to fit the spectral energy distribution of the sources, deriving mass, age, extinction, distance, and accretion for each source in the region. The three-dimensional study of mass distribution for bona fide cluster members shows that mass segregation in the ONC extends to subsolar masses, while the age distribution strongly supports the idea that star formation in the ONC is best described by a major episode of star formation that happened ∼1 Myr ago. For masses ≳0.1 M ⊙, our derived empirical initial mass function (IMF) is in good agreement with a Chabrier system IMF. Both the accretion luminosity (L acc) and mass accretion rates ( Ṁacc ) are best described by broken power-law relations. This suggests that for the majority of young circumstellar disks in this cluster the excess emission may be dominated by X-ray-driven photoevaporation by the central star rather than external photoevaporation. If this is the case, the slopes of the power-law relations may be largely determined by the initial conditions set at the onset of the star formation process, which may be quite similar between regions that eventually form clusters of different sizes.

JWST Observations of Starbursts: Polycyclic Aromatic Hydrocarbon Emission at the Base of the M82 Galactic Wind

We present new observations of the central 1 kpc of the M82 starburst obtained with the James Webb Space Telescope near-infrared camera instrument at a resolution θ ∼ 0.″05–0.″1 (∼1–2 pc). The data comprises images in three mostly continuum filters (F140M, F250M, and F360M), and filters that contain [Fe ii] (F164N), H2 v = 1 → 0 (F212N), and the 3.3 μm polycyclic aromatic hydrocarbon (PAH) feature (F335M). We find prominent plumes of PAH emission extending outward from the central starburst region, together with a network of complex filamentary substructures and edge-brightened bubble-like features. The structure of the PAH emission closely resembles that of the ionized gas, as revealed in Paschen α and free–free radio emission. We discuss the origin of the structure, and suggest the PAHs are embedded in a combination of neutral, molecular, and photoionized gas.

Impact of Planetary Parameters on Water Clouds Microphysics

Potentially habitable exoplanets are targets of great interest for the James Webb Space Telescope and upcoming mission concepts such as the Habitable Worlds Observatory. Clouds strongly affect climate and habitability, but predicting their properties is difficult. In Global Climate Models (GCMs), especially those aiming at simulating Earth, cloud microphysics is often crudely approximated by assuming that all cloud particles have a single, constant size or a prescribed size distribution and that all clouds in a grid cell are identical. For exoplanets that range over a large phase space of planetary properties, this method could result in large errors. In this work, our goal is to determine how cloud microphysics on terrestrial exoplanets, whose condensable is mainly water vapor, depend on aerosol properties and planetary parameters such as surface pressure, surface gravity, and incident stellar radiation. We use the Community Aerosol and Radiation Model for Atmospheres as a 1D microphysical model to simulate the formation and evolution of clouds including the processes of nucleation, condensation, evaporation, coagulation, and vertical transfer. In these 1D idealized experiments, we find that the parameters that determine the macrophysical thermal structure of the atmospheres, including surface pressure and stellar flux, impact cloud radiative effect (CRE) most significantly. Parameters such as gravity and number density of aerosols working as cloud condensation nuclei affect the microphysical processes of cloud formation, including activation and vertical transfer. They also have a significant, though weaker effect on CRE. This work motivates the development of more accurate GCM cloud schemes and should aid in the interpretation of future observations.

Detecting Population III Stars through Tidal Disruption Events in the Era of JWST and Roman

The first-generation metal-free stars, referred to as Population III (Pop III) stars, are believed to be the first objects to form out of the pristine gas in the very early Universe. Pop III stars have different structures from the current generation of stars and are important for generating heavy elements and shaping subsequent star formation. However, it is very challenging to directly detect Pop III stars given their high redshifts and short lifetimes. In this Letter, we propose a novel method for detecting Pop III stars through their tidal disruption events (TDEs) by massive black holes. We model the emission properties and calculate the expected rates for these unique TDEs in the early Universe at z ∼ 10. We find that Pop III star TDEs have much higher mass fallback rates and longer evolution timescales compared to solar-type star TDEs in the local Universe, which enhances the feasibility of their detection, although a good survey strategy will be needed for categorizing these sources as transients. We further demonstrate that a large fraction of the flare emissions are redshifted to infrared wavelengths, which can be detected by the JWST and the Nancy Grace Roman Space Telescope (Roman). Last but not least, we find a promising Pop III star TDE detection rate of up to a few tens per year using Roman, based on our current understanding of the black hole mass function in the early Universe.

Galaxy morphology from z ∼ 6 through the lens of JWST

Context. The James Webb Space Telescope’s (JWST’s) unprecedented combination of sensitivity, spatial resolution, and infrared coverage has enabled a new era of galaxy morphology exploration across most of cosmic history. Aims. We analyze the near-infrared (NIR ∼ 0.8 − 1 μm) rest-frame morphologies of galaxies with log M*/M⊙ > 9 in the redshift range of 0 < z < 6, compare with previous HST-based results and release the first JWST-based morphological catalog of ∼20 000 galaxies in the CEERS survey. Methods. We classified the galaxies in our sample into four main broad classes: spheroid, disk+spheroid, disk, and disturbed, based on imaging with four filters: F150W, F200W, F356W, and F444W. We used convolutional neural networks (CNNs) trained on HST/WFC3 labeled images and domain-adapted to JWST/NIRCam. Results. We find that ∼90% and ∼75% of galaxies at z < 3 have the same early and late and regular and irregular classification, respectively, in JWST and HST imaging when considering similar wavelengths. For small (large) and faint objects, JWST-based classifications tend to systematically present less bulge-dominated systems (peculiar galaxies) than HST-based ones, but the impact on the reported evolution of morphological fractions is less than ∼10%. Using JWST-based morphologies at the same rest-frame wavelength (∼0.8 − 1 μm), we confirm an increase in peculiar galaxies and a decrease in bulge-dominated galaxies with redshift, as reported in previous HST-based works, suggesting that the stellar mass distribution, in addition to light distribution, is more disturbed in the early Universe. However, we find that undisturbed disk-like systems already dominate the high-mass end of the late-type galaxy population (log M*/M⊙ > 10.5) at z ∼ 5, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies ∼1 Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at z > 3, with massive quiescent galaxies (log M*/M⊙ > 10.5) being predominantly bulge-dominated.

Constraints on the narrow-line region of the X-ray quasi-periodic eruption source GSN 069

ABSTRACT The origins of quasi-periodic eruptions (QPEs) are poorly understood, although most theoretical explanations invoke an accretion disc around a supermassive black hole. The gas and stellar environments in the galactic nuclei of these sources are also poorly constrained. In this paper, we present an analysis of archival Hubble Space Telescope (HST) images to study the narrow-line [O iii] emission in the QPE source GSN 069. We find strong evidence for a compact nuclear [O iii] emission region of size ≲ 35 pc, overlaid on top of extended [O iii] emission up to 1 kpc away from the nucleus. The age of the accretion system is estimated to be between 10 and 100 yr. The [O iii] luminosity of the compact region was measured to be $(2.1 \pm 0.3) \times 10^{40}\, \rm erg\, s^{-1}$. Based on cloudy simulations, we constrain that the [O iii] emitting gas has a hydrogen number density in the range $2 \times 10^{3} \lt n_{\rm H} \lesssim 10^{8}\, \rm cm^{-3}$ and volume filling factor fV < 4 × 10−3. We suggest that the dense gas in the nuclear region of GSN 069 originates from molecular clouds (with total mass $\gtrsim 3 \times 10^{3}\, {\rm M}_{\odot }$), which are freshly ionized by the soft X-ray photons from the accretion disc. We predict possible evolution of the compact narrow-line region on emission-line diagnostic diagrams, and hence future HST or integral-field unit observations can be used to further pin down the age of this puzzling system.

Overmassive Black Holes at Cosmic Noon: Linking the Local and the High-redshift Universe

We report for the first time a sample of 12 supermassive black holes (SMBHs) hosted by low-mass galaxies at cosmic noon, i.e., in a redshift range consistent with the peak of star formation history: z ∼ 1–3. These black holes are 2 orders of magnitude too massive for the stellar content of their hosts when compared with the local relation for active galaxies. These overmassive systems at cosmic noon share similar properties with the high-z sources found ubiquitously in recent James Webb Space Telescope (JWST) surveys (same range of black-hole-to-stellar-mass ratio, bolometric luminosity, and Eddington ratio). We argue that black hole feedback processes, for which there is possible evidence in five of the sources, and the differing environments in galactic nuclei at these respective epochs play a key role in these overmassive systems. These findings contribute to our understanding of the growth and coevolution of SMBHs and their host galaxies across cosmic time, offering a link between the early Universe (z > 4) observed by JWST and observations of the present-day Universe (z ≲ 1).

Infrared Properties of Carbon Stars in Our Galaxy

We explore the characteristics of carbon stars within our Galaxy through a comprehensive analysis of observational data spanning visual and infrared (IR) bands. Leveraging data sets from IRAS, the Infrared Space Observatory, Akari, the Midcourse Space Experiment, the Two Micron All Sky Survey, the Wide-field Infrared Survey Explorer (WISE), Gaia DR3, AAVSO, and the SIMBAD object database, we conduct a detailed comparison between the observational data and theoretical models. To facilitate this comparison, we introduce various IR two-color diagrams (2CDs), IR color–magnitude diagrams (CMDs), and spectral energy distributions (SEDs). We find that the CMDs, which utilize the latest distance and extinction data from Gaia DR3 for a substantial number of carbon stars, are very useful for distinguishing carbon-rich asymptotic giant branch (CAGB) stars from extrinsic carbon stars that are not in the AGB phase. To enhance the accuracy of our analysis, we employ theoretical radiative transfer models for dust shells around CAGB stars. These theoretical dust shell models demonstrate a commendable ability to approximate the observations of CAGB stars across various SEDs, 2CDs, and CMDs. We present the infrared properties of known pulsating variables and explore the infrared variability of the sample stars by analyzing WISE photometric data spanning the last 14 years. Additionally, we present a novel catalog of CAGB stars, offering enhanced reliability and a wealth of additional information.

Efficient ultra-broadband low-resolution astrophotonic spectrographs

Broadband low-resolution near-infrared spectrographs in a compact form are crucial for ground- and space-based astronomy and other fields of sensing. Astronomical spectroscopy poses stringent requirements including high efficiency, broad band operation (> 300 nm), and in some cases, polarization insensitivity. We present and compare experimental results from the design, fabrication, and characterization of broadband (1200 - 1650 nm) arrayed waveguide grating (AWG) spectrographs built using the two most promising low-loss platforms - Si3N4 (rectangular waveguides) and doped-SiO2 (square waveguides). These AWGs have a resolving power (λ/Δλ) of ∼200, free spectral range of ∼ 200-350 nm, and a small footprint of ∼ 50-100 mm2. The peak overall (fiber-chip-fiber) efficiency of the doped-SiO2 AWG was ∼ 79% (1 dB), and it exhibited a negligible polarization-dependent shift compared to the channel spacing. For Si3N4 AWGs, the peak overall efficiency in TE mode was ∼ 50% (3 dB), and the main loss component was found to be fiber-to-chip coupling losses. These broadband AWGs are key to enabling compact integrations such as multi-object spectrographs or dispersion back-ends for other astrophotonic devices such as photonic lanterns or nulling interferometers.

Gas-dynamical Mass Measurements of the Supermassive Black Holes in the Early-type Galaxies NGC 4786 and NGC 5193 from ALMA and HST Observations* *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated

We present molecular gas-dynamical mass measurements of the central black holes in the giant elliptical galaxies NGC 4786 and NGC 5193, based on CO (2−1) observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and Hubble Space Telescope near-infrared imaging. The central region in each galaxy contains a circumnuclear disk that exhibits orderly rotation with projected line-of-sight velocities of ∼270 km s−1. We build gas-dynamical models for the rotating disk in each galaxy and fit them directly to the ALMA data cubes. At 0.″31 resolution, the ALMA observations do not fully resolve the black hole sphere of influence (SOI), and neither galaxy exhibits a central rise in rotation speed, indicating that emission from deep within the SOI is not detected. As a result, our models do not tightly constrain the central black hole mass in either galaxy, but they prefer the presence of a central massive object in both galaxies. We measure the black hole mass to be (MBH/108M⊙)=5.0±0.2[1σstatistical]−1.3+1.4[systematic] in NGC 4786 and (MBH/108M⊙)=1.4±0.03[1σstatistical]−0.1+1.5[systematic] in NGC 5193. The largest component of each measurement’s error budget is from the systematic uncertainty associated with the extinction correction in the host galaxy models. This underscores the importance of assessing the impact of dust attenuation on the inferred M BH.

Search for Chirality in Hydrogenated Magnesium Nanosilicates: A DFT and TD-DFT Investigation.

The formation of silicate grains in the interstellar medium (ISM), especially those containing chiral surfaces such as clinopyroxenes, is poorly understood. Moreover, silicate interactions with various forms of hydrogen-proton (H+), neutral H (HI), and molecular hydrogen (H2) are of high importance as hydrogen comprises >90% of the ISM gas budget, and these species play important roles in the formation of new molecules in space. Furthermore, silicate surfaces catalyze the formation of H2 in the interstellar medium formed on dust grain surfaces by H-H association. The technical difficulty of in situ laboratory investigations of nanosilicate nucleation using astrophysically relevant environmental conditions makes computational chemistry a useful tool for studying potential nanosilicate structures. Furthermore, chiral surfaces interacting with chiral organic molecules could serve as templates that lead to the enantiomeric excess of l-amino acids and d-polyols detected in carbonaceous meteorites. However, in order for this effect to take place, an excess of one chiral form of a mineral is required to break the symmetry. This symmetry-breaking event could have been due to the asymmetric absorption of circularly polarized light by the nanosilicate as it traverses star-forming regions. We investigate this possibility using a metastable chiral form of an enstatite dimer as an input for density functional theory (DFT) and time-dependent (TD)-DFT calculations to obtain various properties and circular dichroism spectra. All in all, twenty-six magnesium nanosilicate structures were studied using varying degrees of hydrogenation: none, with HI, with H+, and with H2. The HSE06/aug-cc-pVQZ level of theory was used for the DFT calculations. TD-DFT calculations utilized the CAM-B3LYP/cc-pVQZ and ωB97X-D3/cc-pVQZ functional and basic set pairings. Results show that (1) all twenty-six structures have absorption bands that fall within the 0.6-28.3 μm range available with the newly launched James Webb Space Telescope and (2) there is a small enantioselective effect by UV-CPL on the eight chiral enstatite dimers (predicted g-values of up to 0.007). While the observed effect is small, it opens up the possibility that it is the inorganic material that becomes enantiomerically biased by UV-CPL, driving chiral enhancements in meteoric organic molecules.

Constraints on the z ∼ 5 Star-forming Galaxy Luminosity Function From Hubble Space Telescope Imaging of an Unbiased and Complete Sample of Long Gamma-Ray Burst Host Galaxies

We present rest-frame UV Hubble Space Telescope imaging of the largest and most complete sample of 23 long-duration gamma-ray burst (GRB) host galaxies between redshifts 4 and 6. Of these 23, we present new WFC3/F110W imaging for 19 of the hosts, which we combine with archival WFC3/F110W and WFC3/F140W imaging for the remaining four. We use the photometry of the host galaxies from this sample to characterize both the rest-frame UV luminosity function (LF) and the size–luminosity relation of the sample. We find that when assuming the standard Schechter-function parameterization for the UV LF, the GRB host sample is best fit with α=−1.30−0.25+0.30 and M*=−20.33−0.54+0.44 mag, which are consistent with results based on z ∼ 5 Lyman-break galaxies. We find that ∼68% of our size–luminosity measurements fall within or below the same relation for Lyman-break galaxies at z ∼ 4. This study observationally confirms expectations that at z ∼ 5 Lyman-break and GRB host galaxies should trace the same population and demonstrates the utility of GRBs as probes of hidden star formation in the high-redshift Universe. Under the assumption that GRBs unbiasedly trace star formation at this redshift, our nondetection fraction of 7/23 is consistent at the 95% confidence level with 13%–53% of star formation at redshift z ∼ 5 occurring in galaxies fainter than our detection limit of M 1600Å ≈ −18.3 mag.

SMART: Spectral energy distributions Markov chain Analysis with Radiative Transfer models

Abstract In this paper we present the publicly available open-source spectral energy distribution (SED) fitting code SMART (Spectral energy distributions Markov chain Analysis with Radiative Transfer models). Implementing a Bayesian Markov chain Monte Carlo (MCMC) method, SMART fits the ultraviolet to millimetre SEDs of galaxies exclusively with radiative transfer models that currently constitute four types of pre-computed libraries, which describe the starburst, active galactic nucleus (AGN) torus, host galaxy and polar dust components. An important novelty of SMART is that, although it fits SEDs exclusively with radiative transfer models, it takes comparable time to popular energy balance methods to run. Here we describe the key features of SMART and test it by fitting the multi-wavelength SEDs of the 42 local ultraluminous infrared galaxies (ULIRGs) that constitute the HERschel Ultraluminous Infrared Galaxy Survey (HERUS) sample. The Spitzer spectroscopy data of the HERUS ULIRGs are included in the fitting at a spectral resolution, which is matched to that of the radiative transfer models. We also present other results that highlight the performance and versatility of SMART. SMART promises to be a useful tool for studying galaxy evolution in the James Webb Space Telescope (JWST) era. SMART is developed in Python and is available at https://github.com/ch-var/SMART.git.

Stellar Mapping Using Quadratic Limb-Darkening

Abstract In this thesis, I create useful visualizations of stars empirically from transit observations and theoretically from stellar parameters. Transit photometry has been a popular method to find exoplanets and information about star and planet systems many light-years away. Since most stars are too far away to be seen directly, creating stellar visualizations is an important tool for modeling stars. When creating visualizations, limb-darkening must be considered. Limb-darkening is the visual darkening along the outside, or limbs, of a star. This effect is more dramatic at shorter wavelengths, such as visible light, making it easier to see the darkening of limbs. A recent transit of WASP-39 captured from the James Webb Space Telescope is used to create stellar models for this star, using fitted empirical limb-darkening coefficients. Theoretical models for WASP-39 will also be created using theoretically determined coefficients. While complicated, generating empirical and theoretical limb-darkening profiles is a useful way of modeling stars too far away to observe. Lay summary We can locate brand new exoplanets, many light years away, without ever actually seeing them. Better yet, we can classify and learn vital information about the star and planet system from the exoplanet detection methods. One commonly used detection method is the transit method. The transit method captures the slight dimming of a star’s light as a planet crosses in front of it. This decrease in brightness is temporary and regular. Transits provide information about the composition and properties of stars. One such phenomenon is limb-darkening where the brightness of the star appears darker around its edges. Limb-darkening coefficients are calculated using a quadratic relationship between the intensity at a certain point of the star to the intensity at the center of the star. As the coefficients increase, the “limbs” or edges of the star appear darker. The wavelength in which we are measuring the transit also impacts the limb-darkening. At lower wavelengths, the darkening effect is more dramatic. Using these coefficients at different wavelengths we can create theoretical models to show what stars should look like without being able to see them. The James Webb Telescope (JWST) is capturing numerous exoplanets through the transit method. Launched in December 2021, the JWST contains instruments capable of measuring the slightest changes in the brightness of distant stars. The transit data, collected from the JWST, are fit to infer the best limb-darkening coefficients. We also calculate theoretical coefficients using known physical properties of the star. One particular star captured by the JWST is WASP-39, located 700 light years away. WASP-39 is a dwarf star slightly smaller than our Sun. Models of WASP-39 are created using the empirical and theoretical coefficients. These stellar movies show the appearance of the star at various wavelengths and their corresponding limb-darkening coefficients. The appearances are compared to show how different actual data presents from theoretical models. Providing visual models for stars is an easy way to quantify differences, rather than numerical data. To see the complete thesis, please visit https://scholar.colorado.edu/concern/undergraduate_honors_theses/5m60qt492

GausSN: Bayesian time-delay estimation for strongly lensed supernovae

ABSTRACT We present gausSN, a Bayesian semiparametric Gaussian Process (GP) model for time-delay estimation with resolved systems of gravitationally lensed supernovae (glSNe). gausSN models the underlying light curve non-parametrically using a GP. Without assuming a template light curve for each SN type, gausSN fits for the time delays of all images using data in any number of wavelength filters simultaneously. We also introduce a novel time-varying magnification model to capture the effects of microlensing alongside time-delay estimation. In this analysis, we model the time-varying relative magnification as a sigmoid function, as well as a constant for comparison to existing time-delay estimation approaches. We demonstrate that gausSN provides robust time-delay estimates for simulations of glSNe from the Nancy Grace Roman Space Telescope and the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (Rubin-LSST). We find that up to 43.6 per cent of time-delay estimates from Roman and 52.9 per cent from Rubin-LSST have fractional errors of less than 5 per cent. We then apply gausSN to SN Refsdal and find the time delay for the fifth image is consistent with the original analysis, regardless of microlensing treatment. Therefore, gausSN maintains the level of precision and accuracy achieved by existing time-delay extraction methods with fewer assumptions about the underlying shape of the light curve than template-based approaches, while incorporating microlensing into the statistical error budget. gausSN is scalable for time-delay cosmography analyses given current projections of glSNe discovery rates from Rubin-LSST and Roman.