Abstract
Studies of the rest-frame ultraviolet (UV) luminosity functions (LFs) typically treat star-forming galaxies and active galactic nuclei (AGNs) separately. However, modern ground-based surveys ...now probe volumes large enough to discover AGNs at depths sensitive enough for fainter galaxies, bridging these two populations. Using these observations as constraints, we present a methodology to empirically jointly model the evolution of the rest-UV LFs at
z
= 3–9. Our critical assumptions are that both populations have LFs well described by double power laws modified to allow for a flattening at the faint-end, and that all LF parameters evolve smoothly with redshift. This methodology provides a good fit to the observations and makes predictions to volume densities not yet observed, finding that the volume density of bright (
M
UV
= −28) AGNs rises by ∼10
5
from
z
= 9 to
z
= 3, while bright (
M
UV
= −21) star-forming galaxies rise by only ∼10
2
across the same epoch. The observed bright-end flattening of the
z
= 9 LF is unlikely to be due to AGN activity, and rather is due to a shallowing of the bright-end slope, implying a reduction of feedback in bright galaxies at early times. The intrinsic ionizing emissivity is dominated by star-forming galaxies at
z
> 3, even after applying a notional escape fraction. We find decent agreement between our AGN LFs and predictions based on different black hole seeding models, though all models underpredict the observed abundance of bright AGNs. We show that the wide-area surveys of the upcoming Euclid and Roman observatories should be capable of discovering AGNs to
z
∼ 8.
ABSTRACT
In anticipation of the new era of high-redshift exploration marked by the commissioning of the James Webb Space Telescope (JWST), we present two sets of galaxy catalogues that are designed ...to aid the planning and interpretation of observing programs. We provide a set of 40 wide-field light-cones with footprints spanning approximately ∼1000 arcmin2 containing galaxies up to z = 10, and a new set of eight ultradeep light-cones with 132 arcmin2 footprints, containing galaxies up to z ∼ 12 down to the magnitudes expected to be reached in the deepest JWST surveys. These mock light-cones are extracted from dissipationless N-body simulations and populated with galaxies using the well-established, computationally efficient Santa Cruz semi-analytic model for galaxy formation. We provide a wide range of predicted physical properties, and simulated photometry from Near-Infrared Camera (NIRCam) and many other instruments. We explore the predicted counts and luminosity functions and angular two-point correlation functions for galaxies in these simulated light-cones. We also explore the predicted field-to-field variance using multiple light-cone realizations. We find that these light-cones reproduce the available measurements of observed clustering from 0.2 ≲ z ≲ 7.5 very well. We provide predictions for galaxy clustering at high redshift that may be obtained from future JWST observations. All of the light-cones presented here are made available through a web-based interactive data release portal.
Looking for bright galaxies born in the early universe is fundamental to investigating the Epoch of Reionization, the era when the first stars and galaxies ionized the intergalactic medium. We ...utilize Hubble Space Telescope pure-parallel imaging to select galaxy candidates at a time 500-650 million years after the Big Bang, which corresponds to redshifts z ∼ 8-10. These data come from the Brightest of Reionizing Galaxies Survey (BoRG) Cycle 22 data set, which consists of pure-parallel imaging in ∼90 different lines of sight that sum up to an area of ∼420 arcmin2. This survey uses five filters and has the advantage (compared to the Cycle 21 BoRG program) of including imaging in the JH140 band, covering continuous wavelengths from the visible to near-infrared (λ = 0.35-1.7 m). This allows us to perform a reliable selection of galaxies at z ≥ 8 using the photometric-redshift technique. We use these galaxy candidates to constrain the bright end of the rest-frame ultraviolet luminosity function in this epoch. These candidates are excellent targets for follow-up observations, particularly with the James Webb Space Telescope.
Abstract
We present a catalog of about 25,000 images of massive (
M
⋆
≥ 10
9
M
⊙
) galaxies at redshifts 3 ≤
z
≤ 6 from the TNG50 cosmological simulation, tailored for observations at multiple ...wavelengths carried out with JWST. The synthetic images were created with the SKIRT radiative transfer code, including the effects of dust attenuation and scattering. The noiseless images were processed with the
mirage
simulator to mimic the Near Infrared Camera (NIRCam) observational strategy (e.g., noise, dithering pattern, etc.) of the Cosmic Evolution Early Release Science (CEERS) survey. In this paper, we analyse the predictions of the TNG50 simulation for the size evolution of galaxies at 3 ≤
z
≤ 6 and the expectations for CEERS to probe that evolution. In particular, we investigate how sizes depend on the wavelength, redshift, mass, and angular resolution of the images. We find that the effective radius accurately describes the three-dimensional half-mass–radius of the TNG50 galaxies. Sizes observed at 2
μ
m are consistent with those measured at 3.56
μ
m at all redshifts and masses. At all masses, the population of higher-
z
galaxies is more compact than their lower-
z
counterparts. However, the intrinsic sizes are smaller than the mock observed sizes for the most massive galaxies, especially at
z
≲ 4. This discrepancy between the mass and light distributions may point to a transition in the galaxy morphology at
z
= 4–5, where massive compact systems start to develop more extended stellar structures.
22
22
Data publicly released at
https://www.tng-project.org/costantin22
.
Abstract
The abundance of bright galaxies at
z
> 8 can provide key constraints on models of galaxy formation and evolution, as the predicted abundance varies greatly when different physical ...prescriptions for gas cooling and star formation are implemented. We present the results of a search for bright
z
∼ 9–10 galaxies selected from pure parallel Hubble Space Telescope (HST) imaging programs. We include 132 fields observed as part of the Brightest of Reionizing Galaxies survey, the Hubble Infrared Pure Parallel Imaging Extragalactic Survey, and the WFC3 Infrared Spectroscopic Parallel survey. These observations cover a total of 620 arcmin
2
, about 70% of which is also covered with Spitzer Space Telescope infrared imaging. We identify 13 candidate galaxies in the range 8.3 <
z
< 11 with 24.5 <
m
H
< 26.5 (−22.9 <
M
UV
< −21.2), 11 of which constitute new discoveries. This sample capitalizes on the uncorrelated nature of pure parallel observations to overcome cosmic variance and leverages a full multiwavelength selection process to minimize contamination without sacrificing completeness. We perform detailed completeness and contamination analyses, and present measurements of the bright end of the UV luminosity function using a pseudobinning technique. We find a number density consistent with results from Finkelstein et al. and other searches in HST parallel fields. These bright candidates likely reside in overdensities, potentially representing some of the earliest sites of cosmic reionization. These new candidates are excellent targets for follow up with JWST, and four of them will be observed with the NIRSpec prism in Cycle 1.
Abstract We present the data release and data reduction process for the Epoch 1 NIRCam observations for the Cosmic Evolution Early Release Science Survey (CEERS). These data consist of NIRCam imaging ...in six broadband filters (F115W, F150W, F200W, F277W, F356W and F444W) and one medium-band filter (F410M) over four pointings, obtained in parallel with primary CEERS MIRI observations. We reduced the NIRCam imaging with the JWST Calibration Pipeline, with custom modifications and reduction steps designed to address additional features and challenges with the data. Here we provide a detailed description of each step in our reduction and a discussion of future expected improvements. Our reduction process includes corrections for known prelaunch issues such as 1/ f noise, as well as in-flight issues including snowballs, wisps, and astrometric alignment. Many of our custom reduction processes were first developed with prelaunch simulated NIRCam imaging over the full 10 CEERS NIRCam pointings. We present a description of the creation and reduction of this simulated data set in the Appendix. We provide mosaics of the real images in a public release, as well as our reduction scripts with detailed explanations to allow users to reproduce our final data products. These represent one of the first official public data sets released from the Directors Discretionary Early Release Science (DD-ERS) program.
COSMOS-Web: An Overview of the JWST Cosmic Origins Survey Casey, Caitlin M.; Kartaltepe, Jeyhan S.; Drakos, Nicole E. ...
Astrophysical journal/The Astrophysical journal,
09/2023, Volume:
954, Issue:
1
Journal Article, Web Resource
Peer reviewed
Open access
Abstract
We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hr treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web ...is a contiguous 0.54 deg
2
NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5
σ
point-source depths ranging ∼27.5–28.2 mag. In parallel, we will obtain 0.19 deg
2
of MIRI imaging in one filter (F770W) reaching 5
σ
point-source depths of ∼25.3–26.0 mag. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization (6 ≲
z
≲ 11) and map reionization’s spatial distribution, environments, and drivers on scales sufficiently large to mitigate cosmic variance, (2) to identify hundreds of rare quiescent galaxies at
z
> 4 and place constraints on the formation of the universe’s most-massive galaxies (
M
⋆
> 10
10
M
⊙
), and (3) directly measure the evolution of the stellar-mass-to-halo-mass relation using weak gravitational lensing out to
z
∼ 2.5 and measure its variance with galaxies’ star formation histories and morphologies. In addition, we anticipate COSMOS-Web’s legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool subdwarf stars in the Galactic halo, and possibly the identification of
z
> 10 pair-instability supernovae. In this paper we provide an overview of the survey’s key measurements, specifications, goals, and prospects for new discovery.
Abstract We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from Cosmic Evolution Early Release Science (CEERS) survey NIRCam imaging with photometric redshifts z phot > 8. We ...measure emission line redshifts of z = 7.65 and 8.64 for two galaxies. For two other sources without securely detected emission lines we measure z = 9.77 − 0.29 + 0.37 and 10.01 − 0.19 + 0.14 by fitting model spectral templates to the prism data, from which we detect continuum breaks consistent with Ly α opacity from a mostly neutral intergalactic medium. The presence of strong breaks and the absence of strong emission lines give high confidence that these two galaxies have redshifts z > 9.6, but the redshift values derived from the breaks alone have large uncertainties given the low spectral resolution and relatively low S/N of the CEERS NIRSpec prism data. The two z ∼ 10 sources observed are relatively luminous ( M UV < −20), with blue continua (−2.3 ≲ β ≲ −1.9) and low dust attenuation ( A V ≃ 0.15 − 0.1 + 0.3 ); and at least one of them has a high stellar mass for a galaxy at that redshift ( log ( M ⋆ / M ⊙ ) ≃ 9.3 − 0.3 + 0.2 ). Considered together with spectroscopic observations of other CEERS NIRCam-selected high- z galaxy candidates in the literature, we find a high rate of redshift confirmation and low rate of confirmed interlopers (8%). Ten out of 35 z > 8 candidates with CEERS NIRSpec spectroscopy do not have secure redshifts, but the absence of emission lines in their spectra is consistent with redshifts z > 9.6. We find that z > 8 photometric redshifts are generally in agreement (within their uncertainties) with the spectroscopic values, but also that the photometric redshifts tend to be slightly overestimated (〈Δ z 〉 = 0.45 ± 0.11), suggesting that current templates do not fully describe the spectra of very-high- z sources. Overall, the spectroscopy solidifies photometric redshift evidence for a high spatial density of bright galaxies at z > 8 compared to theoretical model predictions, and further disfavors an accelerated decline in the integrated UV luminosity density at z > 8.
Abstract
Identifying merging galaxies is an important—but difficult—step in galaxy evolution studies. We present random forest (RF) classifications of galaxy mergers from simulated JWST images based ...on various standard morphological parameters. We describe (a) constructing the simulated images from IllustrisTNG and the Santa Cruz SAM and modifying them to mimic future CEERS observations and nearly noiseless observations, (b) measuring morphological parameters from these images, and (c) constructing and training the RFs using the merger history information for the simulated galaxies available from IllustrisTNG. The RFs correctly classify ∼60% of non-merging and merging galaxies across 0.5 <
z
< 4.0. Rest-frame asymmetry parameters appear more important for lower-redshift merger classifications, while rest-frame bulge and clump parameters appear more important for higher-redshift classifications. Adjusting the classification probability threshold does not improve the performance of the forests. Finally, the shape and slope of the resulting merger fraction and merger rate derived from the RF classifications match with theoretical Illustris predictions but are underestimated by a factor of ∼0.5.
Abstract We present JWST NIRSpec spectroscopy for 11 galaxy candidates with photometric redshifts of z ≃ 9 − 13 and M UV ∈ −21, −18 newly identified in NIRCam images in the Cosmic Evolution Early ...Release Science Survey. We confirm emission line redshifts for 7 galaxies at z = 7.762–8.998 using spectra at ∼1–5 μ m either with the NIRSpec prism or its three medium-resolution ( R ∼ 1000) gratings. For z ≃ 9 photometric candidates, we achieve a high confirmation rate of ≃90%, which validates the classical dropout selection from NIRCam photometry. No robust emission lines are identified in three galaxy candidates at z > 10, where the strong O iii and H β lines would be redshifted beyond the wavelength range observed by NIRSpec, and the Ly α continuum break is not detected with the sensitivity of the current data. Compared with Hubble Space Telescope-selected bright galaxies ( M UV ≃ −22) that are similarly spectroscopically confirmed at z ≃ 8 − 9, these NIRCam-selected galaxies are characterized by lower star formation rates (SFRs; SFR ≃ 4 M ⊙ yr −1 ) and lower stellar masses (≃10 8 M ⊙ ), but with higher specific SFR (≃40 Gyr −1 ), higher O iii +H β equivalent widths (≃1100 Å), and elevated production efficiency of ionizing photons ( log ( ξ ion / Hz erg − 1 ) ≃ 25.8 ) induced by young stellar populations (<10 Myr) accounting for ≃20% of the galaxy mass, highlighting the key contribution of faint galaxies to cosmic reionization. Taking advantage of the homogeneous selection and sensitivity, we also investigate metallicity and ISM conditions with empirical calibrations using the O iii 5008 /H β ratio. We find that galaxies at z ≃ 8 − 9 have higher SFRs and lower metallicities than galaxies at similar stellar masses at z ≃ 2 − 6, which is generally consistent with the current galaxy formation and evolution models.
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