We describe the software package ESpRESSO - [E]xtragalactic [Sp]ectroscopic [R]oman [E]mulator and [S]imulator of [S]ynthetic [O]bjects, created to emulate the slitless spectroscopic observing modes of the Nancy Grace Roman Space Telescope (Roman) Wide Field Instrument (WFI). We combine archival Hubble Space Telescope (HST) imaging data of comparable spatial resolution with model spectral energy distributions to create a data-cube of flux density as a function of position and wavelength. ESpRESSO is designed to generate grism simulations for any Roman WFI SCA using detector-specific optical solutions; in this paper, the simulations are limited by the sky area of the deepest available input imaging and therefore focus primarily on SCA5, with a foreground scene spanning approximately two SCAs. We also demonstrate the ability to inject custom sources using the described tools and pipelines. In addition, we show that spectral features such as emission line pairs are unlikely to be mistaken as off order contaminating features and vice versa. These simulated scenes can be used in developing future spectral data analysis tools.

Since the launch of JWST, the sample size of reionization-era Ly alpha emitters (LAEs) has been steadily growing; yet inferences about the neutral hydrogen fraction in the intergalactic medium exhibit increasing variance at redshift z approximate to 7, possibly indicating significant field-to-field fluctuations in the progression of cosmic reionization. In this paper, we present new JWST/NIRSpec and Keck/LRIS spectra of nine LAEs in the redshift z similar to 7 protocluster LAGER-z7OD1. Measurements of Ly alpha transmission and Ly alpha velocity offset along multiple sight lines map the Ly alpha damping wing optical depth across the galaxy overdensity. In the standard context of inside-out ionization, we estimate the radii of ionized bubbles, Rimin=0.07- 0.69 Mpc (physical), based on the distance from each LAE to the first neutral patch along the sight line. The resulting 3D topology reveals three distinct subclusters where the ionized bubbles are approaching overlap. Five of the nine LAEs plausibly ionized their bubbles, where a few bursts of star formation and a modest escape fraction are sufficient. We demonstrate, however, that the actual ionized volumes are likely larger, at least Riism = 0.42-1.29 Mpc (physical), based on an empirical model for interstellar attenuation of Ly alpha. Modeling galactic attenuation of Ly alpha significantly increases the inferred intergalactic transmission (thus enlarging the ionized path length). The error bars on the reddening correction allow fully overlapping bubbles, and our results are consistent with accelerated reionization in the protocluster.

Strong emission from doubly ionized oxygen is a beacon for some of the most intensely star-forming galaxies. JWST enables the search for this beacon in the early Universe with unprecedented sensitivity. Using UNCOVER DR1 JWST/NIRCam and Hubble Space Telescope (HST) imaging data of A2744, we identify strong (rest-frame EW > 500 & Aring;) [O iii]5008 emitters at z similar to 7 based on excess F410M flux. We find N = 68 z similar to 7 [O iii] candidates, including N = 33 with deep HST coverage required to rule out lower-redshift interlopers (13.68 arcmin2 with F814W 5 sigma depth >28 AB). Such strong emission lines can produce very red colors often misinterpreted as evidence for old, massive stellar populations, but are shown to be emission lines where we have spectra. Using this deep HST sample, we derive a new [O iii] luminosity function (LF) spanning 41.1log10(L/ergs(-1))>42.4 . Combining both data sets, we construct an LF spanning 2 dex in luminosity, with a best-fit Schechter function: alpha=-2.13-0.16+0.15 , log(10)(phi*/Mpc(-3))=-4.17(-1.39)(+0.49) , and log(10)(L*/ erg s -1)=43.06(+0.90)(-0.29) . There is little evolution between this LF and published [O iii] LFs at 3 < z < 8, and no evidence of a turnover at faint luminosities. The sizes of these extreme [O iii] emitters are similar to their low redshift counterparts, the Green Peas. The z similar to 7 [O iii] LF aligns with the Ly alpha LF at the bright end, suggesting many of these galaxies are also Ly alpha emitters.

We searched the Chandra and XMM archives for 900 Green Pea galaxies to identify signs of active galactic nuclei (AGN). Green peas are low-mass, emission-line galaxies that resemble high-redshift dwarf galaxies. From 29 observations, we detected X-rays in nine galaxies with signal-to-noise ratio > 3. These X-ray sources also show He ii and broad H α emissions, suggesting winds, though the weak correlation between their line widths implies that the He ii emission is not from super-Eddington accretors. The ratio of X-ray luminosity to star formation rate aligns with an anticorrelation with metallicity for most detected sources, pointing to ultraluminous X-ray sources as likely contributors. The X-ray emission exceeds what stellar processes can produce, supporting the existence of low-luminosity AGN. Using the broad H α emission lines, we infer black hole masses ranging from 10 ^4 to 10 ^6 M _⊙ in these sources. Since Green Peas are significant Lyman continuum leakers, these AGN may have played a role in cosmic reionization.

The Roman Space Telescope (Roman) is a three-mirror anastigmat design with a 2.4-m primary mirror. It will be based in the L2 orbit optimized for observations of cosmic expansion using the Wide-Field Instrument (WFI) and exoplanet discovery using the coronagraph instrument (CGI). The WFI features a 300-megapixel near-infrared detector array providing a field of view >100 times larger than that of the Hubble Space Telescope. To enable a low-resolution spectroscopy functionality for Roman, a compact Prism Assembly was added and installed in a slot in WFI's element wheel. The Prism Assembly has a 0.76 to 1.8 mu m passband enabling a survey of Supernova Type 1a redshifts in the range of 0.2 to 1.7. It achieves a spectral resolving power of 170>R>70 across the field. The Prism Assembly had restrictions on size, mass, and geometry, and a challenging schedule due to being a late addition to Roman. Despite this, the Prism Assembly is a compact high-performance spectrographic element, implemented as a refractive, all-spherical surfaces, two-element optical design using S-TIH1 glass and CaF2. We describe the Prism Assembly from design and implementation through alignment, optical performance test, and calibration to delivery for installation in the WFI instrument. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.Distribution or reproduction of this work in whole or in part requires full attribution of the originalpublication, including its DOI.

Recently, the James Webb Space Telescope has revealed a new class of high-redshift (high- z , z > 4) compact galaxies that are red in the rest-frame optical and blue in the rest-frame UV with V-shaped spectral energy distributions (SEDs), referred to as “little red dots” (LRDs). It is very likely that LRDs host obscured broad-line active galactic nuclei (AGNs). In the meanwhile, Green Pea galaxies (GPs), which are compact dwarf galaxies at low redshift, share various similar properties with high-redshift star-forming galaxies. Here, we aim to find the connection between the LRDs and GPs hosting broad-line AGNs (BLGPs). With a sample of 19 BLGPs obtained from our previous work, we further identify seven GPs with V-shaped rest-frame UV-to-optical SEDs that are likely local analogs to LRDs. These V-shaped BLGPs exhibit faint UV absolute magnitudes and sub-Eddington rates similar to those of LRDs. Three of them occupy a similar region to LRDs in the Baldwin–Philips–Terlevich diagram, suggesting they have similar ionization conditions and gas-phase metallicities to LRDs. These similarities suggest that V-shaped BLGPs can be taken as local analogs of high-redshift LRDs. In addition, most (16/19) BLGPs, including six V-shaped BLGPs, host overmassive black holes (BHs) above the local M BH – M * relation, making it the first sample of galaxies hosting overmassive BHs at z < 0.4. These findings will help us learn more about the formation and coevolution of early galaxies and BHs.

This paper gives an overview of TEMPLATES, a JWST Early Release Science program that targeted four extremely bright, gravitationally lensed galaxies: two extremely dusty, two with low attenuation, as templates for galaxy evolution studies with JWST. TEMPLATES obtains a common set of spectral diagnostics for these 1.3 < z < 4.2 galaxies, in particular H alpha, Paschen alpha, and the rest-frame optical and near-infrared continua. In addition, two of the four targets have JWST coverage of [O III] 5007 Angstrom and H beta; the other two targets have have JWST coverage of PAH 3.3 micron and complementary ALMA data covering the [C II] 158 micron emission line. The science goals of TEMPLATES are to demonstrate attenuation-robust diagnostics of star formation, map the distribution of star formation, compare the young and old stellar populations, and measure the physical conditions of star formation and their spatial variation across the galaxies. In addition, TEMPLATES has technical goals to establish best practices for the Integral Field Units (IFU) within the NIRSpec and MIRI instruments, both in terms of observing strategy and in terms of data reduction. The paper describes TEMPLATES's observing program, scientific and technical goals, data reduction methods, and deliverables, including high-level data products and data reduction cookbooks.

The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is scheduled to be launched to geostationary orbit in 2027. It will carry a telescope with an unprecedentedly large field of view (204 deg ^2 ) and near-ultraviolet (NUV; 230–290 nm) sensitivity (22.5 mag, 5 σ , at 900 s). ULTRASAT will conduct the first wide-field survey of transient and variable NUV sources and will revolutionize our ability to study the hot transient Universe. It will explore a new parameter space in energy and timescale (months-long light curves with minutes cadence), with an extragalactic volume accessible for the discovery of transient sources that is >300 times larger than that of the Galaxy Evolution Explorer (GALEX) and comparable to that of the Vera Rubin Observatory’s Legacy Survey of Space and Time. ULTRASAT data will be transmitted to the ground in real time, and transient alerts will be distributed to the community in <15 minutes, enabling vigorous ground-based follow up of ULTRASAT sources. ULTRASAT will also provide an all-sky NUV image to >23.5 AB mag, over 10 times deeper than the GALEX map. Two key science goals of ULTRASAT are the study of mergers of binaries involving neutron stars, and supernovae. With a large fraction (>50%) of the sky instantaneously accessible, fast (minutes) slewing capability, and a field of view that covers the error ellipses expected from gravitational-wave (GW) detectors beyond 2026, ULTRASAT will rapidly detect the electromagnetic emission following binary neutron star/neutron star–black hole mergers identified by GW detectors, and will provide continuous NUV light curves of the events. ULTRASAT will provide early (hour) detection and continuous high-cadence (minutes) NUV light curves for hundreds of core-collapse supernovae, including for rarer supernova progenitor types.

High-redshift quasars are thought to live in the densest regions of space, which should be made evident by an overdensity of galaxies around them. However, campaigns to identify these overdensities by searching for Lyman-break galaxies (LBGs) and Lyman alpha emitters (LAEs) have had mixed results. These may be explained by either the small field of view of some of the experiments, the broad redshift ranges targeted by LBG searches, and the inherently high uncertainty of quasar redshifts estimated from ultraviolet emission lines, which makes it difficult to place the Ly-alpha emission line within a narrowband filter. Here, we present a 3 square degree search (similar to 1000 pMpc(2)) for LAEs around the z = 6.9 quasar VIK J2348-3054 using the Dark Energy CAMera (DECam) housed on the 4m Blanco telescope, finding 38 LAEs. The systemic redshift of VIK J2348-3054 is known from ALMA [CII] observations and places the Ly-alpha emission line of companions within the NB964 narrowband of DECam. This is the largest field-of-view LAE search around a z > 6 quasar conducted to date. We find that this field is similar to ten times more overdense than Chandra Deep-Field South, observed previously with the same instrumental setup as well as several combined blank fields. This is strong evidence that VIK J2348-3054 resides in an overdensity of LAEs over several Mpc. Surprisingly, we find a lack of LAEs within 5 physical Mpc of the quasar and take this to most likely be evidence of quasar-suppressing star formation in its immediate vicinity. This result highlights the importance of performing overdensity searches over large areas to properly assess the density of those regions of the Universe.

Past studies have investigated the evolution in specific star formation rate (sSFR) and its observational proxy (H alpha equivalent width; EW) up to z similar to 6; however, such measurements may overestimate the typical sSFR/EW at a given redshift due to selection effects. We investigate the 'intrinsic' (selection and observational effects corrected) H alpha EW distributions of z similar to 0.4-2.2 narrowband-selected H alpha samples from High-z Emission Line Survey (HiZELS) and Deep and Wide Narrowband survey (DAWN) using a forward modelling approach where we assume an 'intrinsic' exponential EW distribution, apply selection and filter effects, and compare with observed H alpha EW distributions. We find an 'intrinsic' EW-stellar mass anticorrelation, EW0 proportional to M gamma, with steepening slopes gamma=-0.18 +/- 0.03 to -0.24(-0.08)(+0.06 )at z similar to 0.4 and z similar to 2.2, respectively. At 1010 M-circle dot, we find EW0 proportional to(1+z)1.78(-0.23)(+0.22) and a steeper evolution with decreasing stellar mass highlighting the high EW nature of low-mass, high-z systems. We model this redshift evolving EW-stellar mass anticorrelation, W0(M,z), and find it produces H alpha luminosity and SFR functions strongly consistent with observations. Our W0(M,z) model suggests EW0>200 & Aring; emitters contribute similar to 40 per cent to overall cosmic SF at z similar to 1.5(-2), consistent with sSFR >10(-8.5) yr(-1) (makes up similar to 45-55 per cent of cosmic SF at z similar to 2) and highlights the importance of high EW systems at high-z. Our W0(M,z) model also reproduces the cosmic sSFR evolution found in both simulations and observations (including selection limits), such that selection effects in observations may explain the disagreement. Lastly, we forecast Roman and Euclid grism surveys using our W-0(M,z) model including limiting resolution and observational efficiency effects. We predict similar to 24000 and similar to 300000.55x10(-17 )erg s(-1) cm(-2) including 107.2-8 M-circle dot galaxies at z>1 with EW0>1000 & Aring;. Both Roman and Euclid will observe some of the most bursty/high EW, low-mass star-forming galaxies near cosmic noon in unprecedented detail.

Context. The epoch of reionization is a landmark in structure formation and galaxy evolution. How it happened is still not clear, especially regarding which population of objects was responsible for contributing the bulk of ionizing photons to this process. Doubly peaked Lyman-alpha profiles in this epoch are of particular interest since they hold information about the escape of ionizing radiation and the environment surrounding the source.Aims. We wish to understand the escape mechanisms of ionizing radiation in Ly alpha emitters during this time and the origin of a doubly peaked Lyman-alpha profile. We also wish to estimate the size of a potential ionized bubble.Methods. Using radiative transfer models, we fit the line profile of a bright Ly alpha emitter at z similar to 6.9 using various gas geometries. The line modeling reveals significant radiation escape from this system.Results. The studied source shows significant escape (fesc(Ly alpha) similar to 0.8, as predicted by the best fitting radiative transfer model) and appears to inhabit an ionized bubble of radius Rb approximate to 0.8-0.3+0.5 pMpc(tage/108)1/3 R b approximate to 0 . 8 - 0.3 + 0.5 pMpc t age 10 8 1 3 $ R_{b}\approx 0.8<^>{+0.5}_{-0.3}\,\mathrm{pMpc}\left(\frac{t_{\mathrm{age}}}{10<^>{8}}\right)<^>{\frac{1}{3}} $ . Radiative transfer modeling predicts the line to be completely redward of the systemic redshift. We suggest the line morphology is produced by inflows, by multiple components emitting Ly alpha, or by an absorbing component in the red wing.Conclusions. We propose that CDFS-1's profile has two red peaks produced by winds within the system. Its high fesc(Ly alpha) and the low-velocity offset from the systemic redshift suggest that the source is an active ionizing agent. Future observations will reveal whether a peak is present blueward of the systemic redshift or if multiple components produce the profile.

Surveys in space and time are key to answering outstanding questions in astrophysics. The power to study very large numbers of stars, galaxies, and transient events over large portions of the sky and different time scales has repeatedly led to new breakthroughs. The Nancy Grace Roman Space Telescope (Roman), NASA's next Astrophysics Flagship mission, elevates wide field and time domain survey observations to previously inaccessible scales. Roman carries the Wide Field Instrument (WFI), which provides visible to near-infrared imaging and spectroscopy with an unprecedented combination of field-of-view, spatial resolution, and sensitivity. When combined with a highly stable observatory and efficient operations, the WFI allows surveys never before possible. These observations will lead to new discoveries in cosmology, exoplanets, and a very wide array of other astrophysics topics ranging from high redshift galaxies to small bodies in the solar system. This paper provides an overview of Roman survey science, connects this science to the design of the WFI, and provides a status update on WFI hardware build and test.

We present the first results of the Hubble Deep Hydrogen Alpha (HDH α ) project, which analyzes the space-borne deep H α narrowband imaging data in the GOODS-S region. The HDH α data comprises 72 orbits’ images taken with the Hubble Space Telescope (HST) Advanced Camera for Surveys/Wide Field Channel F658N filter. The exposure time varies across a total area of ∼76.1 arcmin ^2 , adding up to a total exposure time of 195.7 ks, among which 68.8 ks are spent in the deepest region. These images are aligned, reprojected, and combined to have the same pixel grid as the Hubble Legacy Fields. The scientific goals of the HDH α include establishing a sample of emission-line galaxies (ELGs) including [O iii ] emitters at z ∼ 0.3, [O ii ] emitters at z ∼ 0.8, and Ly α emitters (LAEs) at z ∼ 4.4, studying the line morphology of ELGs with high resolution imaging data, and statistically analyzing the line luminosity functions and line equivalent-width distributions of ELGs selected with HST. Furthermore, the HDH α project enhances the legacy value of the GOODS-S field by contributing the first HST-based narrowband image to the existing data sets, which includes the HST broadband data and other ancillary data from X-ray to radio taken by other facilities. In this paper, we describe the data reduction process of the HDH α , select ELGs based on HST's F658N and broadband data, validate the redshifts of the selected candidates by crossmatching with the public spectroscopic catalogs in the GOODS-S, and present a final catalog of the confirmed [O iii ] emitters at z ∼ 0.3, [O ii ] emitters at z ∼ 0.8, and LAEs at z ∼ 4.4.

ULTRASAT is a near-ultraviolet imaging satellite with a wide field of view (200 square degrees) and a planned launch in late 2027. It is an international partnership led by Israel (Israel Space Agency and Weizmann Institute of Science) in partnership with the United States (NASA) and Germany (DESY). ULTRASAT will provide high cadence observations and rapid target-of-opportunity response, providing a powerful capability for time-domain and multimessenger astrophysics (TDAMM), and will have scientific applications from solar system studies to cosmology. This proceedings paper includes the content of a poster presented at the 2024 SPIE Astronomical Telescopes and Instruments meeting, describing briefly the ULTRASAT science drivers and capabilities; NASA's roles in the ULTRASAT project; and how ULTRASAT fits with NASA scientific priorities. It also includes an expanded summary of the United States Participating Scientist Program for ULTRASAT.

The slitless grism on the Nancy Grace Roman Space Telescope will enable deep near-infrared spectroscopy over a wide field of view. We demonstrate Roman's capability to detect Ly α galaxies at z > 7 using a multiple position angle (PA) observational strategy. We simulate Roman grism data using a realistic foreground scene from the COSMOS field. We also input fake Ly α galaxies spanning redshift z = 7.5–10.5 and a line-flux range of interest. We show how a novel data-cube search technique—CUBGRISM—originally developed for the Galaxy Evolution Explorer can be applied to Roman grism data to produce a Ly α flux-limited sample without the need for continuum detections. We investigate the impact of altering the number of independent PAs and exposure time. A deep Roman grism survey with 25 PAs and a total exposure time of 70 hr can achieve Ly α line depths comparable to the deepest z = 7 narrowband surveys ( L _Ly _α ≳ 10 ^43 erg s ^−1 ). Assuming a null result, where the opacity of the intergalactic medium (IGM) remains unchanged from z ∼ 7, this level of sensitivity will detect ∼400 deg ^−2 Ly α emitters from z = 7.25 to 8.75. A decline from this expected number density is the signature of an increasing neutral hydrogen fraction and the onset of reionization. Our simulations indicate that a deep Roman grism survey has the ability to measure the timing and magnitude of this decline, allowing us to infer the ionization state of the IGM and helping us to distinguish between models of reionization.

The James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-domain Field (TDF) is a >14' diameter field optimized for multiwavelength time-domain science with JWST. It has been observed across the electromagnetic spectrum both from the ground and from space, including with the Hubble Space Telescope (HST). As part of HST observations over three cycles (the "TREASUREHUNT" program), deep images were obtained with the Wide Field Camera on the Advanced Camera for Surveys in F435W and F606W that cover almost the entire JWST NEP TDF. Many of the individual pointings of these programs partially overlap, allowing an initial assessment of the potential of this field for time-domain science with HST and JWST. The cumulative area of overlapping pointings is similar to 88 arcmin(2), with time intervals between individual epochs that range between 1 day and 4+ yr. To a depth of m(AB) similar or equal to 29.5 mag (F606W), we present the discovery of 12 transients and 190 variable candidates. For the variable candidates, we demonstrate that Gaussian statistics are applicable and estimate that similar to 80 are false positives. The majority of the transients will be supernovae, although at least two are likely quasars. Most variable candidates are active galactic nuclei (AGNs), where we find 0.42% of the general z less than or similar to 6 field galaxy population to vary at the similar to 3 sigma level. Based on a 5 yr time frame, this translates into a random supernova areal density of up to similar to 0.07 transients arcmin(-2) (similar to 245 deg(-2)) per epoch and a variable AGN areal density of similar to 1.25 variables arcmin(-2) (similar to 4500 deg(-2)) to these depths.

We searched the Chandra and XMM archives for observations of 900 green pea galaxies to find AGN signatures. Green peas are low-mass galaxies with prominent emission lines, similar in size and star formation rate to high-redshift dwarf galaxies. Of the 29 observations found, 9 show X-ray detections with S/N>3. The 2-10 keV X-ray luminosity for these 9 sources exceeds 10^40 erg s^-1, with 2 sources exceeding 10^41 erg s^-1, suggesting the presence of intermediate-mass black holes (IMBH) or low-luminosity AGN (LLAGN) with BH masses between 100-10^6M_⊙. All X-ray detected sources (plus 6 additional sources) show He IIλ4686 emission and a broad component of the Hα emission line, indicating winds. The line widths of the broad Hα and He IIλ4686 emitting gas clouds are weakly correlated (R^2=0.15), suggesting He IIλ4686 emission is inconsistent with winds from super-Eddington accretors. However, the ratio of X-ray luminosity to star formation rate shows an anti-correlation with metallicity in 5 out of 9 X-ray detected sources, implying ultraluminous X-ray sources are key contributors to the observed X-ray luminosity. This could be due to super-Eddington accretors or IMBH. The X-ray emission is much higher than that produced by Wolf-Rayet stars and supernovae-driven winds. Thus, the X-ray luminosity in these 9 sources can only be explained by black holes with masses over 100 M_⊙. Our findings suggest the presence of LLAGN in these galaxies, with broad Hα line widths implying BH masses of 10^4-10^6M_⊙. Given Green Peas' role as significant Lyman Continuum leakers, LLAGN in these galaxies could have contributed significantly to cosmic reionization.

We describe our technical approach to developing a space observatory to survey the large-scale distribution of neutral and ionized intergalactic gas during cosmological reionization (the landmark event of "Cosmic Dawn") from 400 to 800 million years after the Big Bang. To look this far back in time at the large-scale distributions of ionized gases, we use wide-field, narrow-passband surveys for Lyman alpha light from individual galaxies red-shifted to the near-infrared. Wherever this light can be seen, it implies the presence of ionized gas. We are developing a large FOV (0.5-to-1.0-degree) instrument with plate scale on the order of 0.3"/pixel to obtain a comprehensive view of the reionization process over a representative volume of the early universe. To maximize science return, the Reionization Explorer (REX) will be placed in a high orbit. Through disciplined application of design-for-cost principles and a thorough searching for existing designs that can achieve our science objectives, we have developed what could be a game changing approach at advancing our understanding of the formation of the universe on a limited Small Explorer (SMEX) budget by leveraging existing telescope, instrument, and spacecraft designs.