ABSTRACT We present Atacama Large Millimeter Array (ALMA) detections of atomic carbon line and dust continuum emission in two UV-luminous galaxies at redshift 6. The far-infrared (far-IR) ...luminosities of these galaxies are substantially lower than similar starbursts at later cosmic epochs, indicating an evolution in the dust properties with redshift, in agreement with the evolution seen in ultraviolet (UV) attenuation by dust. The C ii to FIR ratios are found to be higher than at low redshift showing that C ii should be readily detectable by ALMA within the reionization epoch. One of the two galaxies shows a complex merger nature with the less massive component dominating the UV emission and the more massive component dominating the FIR line and continuum. Using the interstellar atomic carbon line to derive the systemic redshifts we investigate the velocity of Ly emission emerging from high-z galaxies. In contrast to previous work, we find no evidence for decreasing Ly velocity shifts at high-redshift. We observe an increase in velocity shifts from to , consistent with the effects of increased intergalactic medium absorption.
Abstract
We present JWST Extragalactic Medium-band Survey, the first public medium-band imaging survey carried out using JWST/NIRCam and NIRISS. These observations use ∼2 and ∼4
μ
m medium-band ...filters (NIRCam F182M, F210M, F430M, F460M, F480M; and NIRISS F430M and F480M in parallel) over 15.6 arcmin
2
in the Hubble Ultra Deep Field (UDF), thereby building on the deepest multiwavelength public data sets available anywhere on the sky. We describe our science goals, survey design, NIRCam and NIRISS image reduction methods, and describe our first data release of the science-ready mosaics, which reach 5
σ
point-source limits (AB mag) of ∼29.3–29.4 in 2
μ
m filters and ∼28.2–28.7 at 4
μ
m. Our chosen filters create a JWST imaging survey in the UDF that enables novel analysis of a range of spectral features potentially across the redshift range of 0.3 <
z
< 20, including Paschen-
α
, H
α
+N
ii
, and O
iii
+H
β
emission at high spatial resolution. We find that our JWST medium-band imaging efficiently identifies strong line emitters (medium-band colors >1 mag) across redshifts 1.5 <
z
< 9.3, most prominently H
α
+N
ii
and O
iii
+H
β
. We present our first data release including science-ready mosaics of each medium-band image available to the community, adding to the legacy value of past and future surveys in the UDF. This survey demonstrates the power of medium-band imaging with JWST, informing future extragalactic survey strategies using JWST observations.
Abstract
Broad-line regions (BLRs) in high-redshift quasars provide crucial information on chemical enrichment in the early universe. Here we present a study of BLR metallicities in 33 quasars at ...redshift 5.7 <
z
< 6.4. Using the near-IR spectra of the quasars obtained from the Gemini telescope, we measure their rest-frame UV emission-line flux and calculate flux ratios. We then estimate BLR metallicities with empirical calibrations based on photoionization models. The inferred median metallicity of our sample is a few times the solar value, indicating that the BLR gas had been highly metal enriched at
z
∼ 6. We compare our sample with a low-redshift quasar sample with similar luminosities and find no evidence of redshift evolution in quasar BLR metallicities. This is consistent with previous studies. The Fe
ii
/Mg
ii
flux ratio, a proxy for the Fe/
α
element abundance ratio, shows no redshift evolution as well, further supporting rapid nuclear star formation at
z
∼ 6. We also find that the black hole mass–BLR metallicity relation at
z
∼ 6 is consistent with the relation measured at 2 <
z
< 5, suggesting that our results are not biased by a selection effect due to this relation.
We present the discovery of one or two extremely faint z ~ 6 quasars in 6.5 degsup 2 utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The color selection can ...effectively isolate quasars at z ~ 6 from M/L/T dwarfs without the J-band photometry down to zsubR < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We derive the quasar luminosity function at z ~ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. This was found to still be insufficient for the required photon budget of re-ionization at z ~ 6.
We present discovery imaging and spectroscopy for nine new z ~ 6 quasars found in the Canada-France High-z Quasar Survey (CFHQS) bringing the total number of CFHQS quasars to 19. By combining the ...CFHQS with the more luminous Sloan Digital Sky Survey sample, we are able to derive the quasar luminosity function from a sample of 40 quasars at redshifts 5.74 < z < 6.42. Our binned luminosity function shows a slightly lower normalization and flatter slope than found in previous work. The binned data also suggest a break in the luminosity function at M 1450 --25. A double power-law maximum likelihood fit to the data is consistent with the binned results. The luminosity function is strongly constrained (1 Delta *s uncertainty <0.1 dex) over the range --27.5 < M 1450 < --24.7. The best-fit parameters are Delta *Q(M*1450) = 1.14 X 10--8 Mpc--3 mag--1, break magnitude M*1450 = --25.13, and bright end slope Delta *b = --2.81. However, the covariance between Delta *b and M*1450 prevents strong constraints being placed on either parameter. For a break magnitude in the range --26 < M*1450 < --24, we find --3.8 < Delta *b < --2.3 at 95% confidence. We calculate the z = 6 quasar intergalactic ionizing flux and show it is between 20 and 100 times lower than that necessary for reionization. Finally, we use the luminosity function to predict how many higher redshift quasars may be discovered in future near-IR imaging surveys.
Abstract
We present new measurements of rest-UV luminosity functions and angular correlation functions from 4,100,221 galaxies at
z
∼ 2–7 identified in the Subaru/Hyper Suprime-Cam survey and CFHT ...Large Area
U
-band Survey. The obtained luminosity functions at
z
∼ 4–7 cover a very wide UV luminosity range of ∼
0.002
–
2000
L
UV
*
combined with previous studies, confirming that the dropout luminosity function is a superposition of the active galactic nucleus (AGN) luminosity function dominant at
M
UV
≲ −24 mag and the galaxy luminosity function dominant at
M
UV
≳ −22 mag, consistent with galaxy fractions based on 1037 spectroscopically identified sources. Galaxy luminosity functions estimated from the spectroscopic galaxy fractions show the bright-end excess beyond the Schechter function at ≳2
σ
levels, possibly made by inefficient mass quenching, low dust obscuration, and/or hidden AGN activity. By analyzing the correlation functions at
z
∼ 2–6 with HOD models, we find a weak redshift evolution (within 0.3 dex) of the ratio of the star formation rate (SFR) to the dark matter accretion rate,
SFR
/
M
̇
h
, indicating the almost constant star formation efficiency at
z
∼ 2–6, as suggested by our earlier work at
z
∼ 4–7. Meanwhile, the ratio gradually increases with decreasing redshift at
z
< 5 within 0.3 dex, which quantitatively reproduces the cosmic SFR density evolution, suggesting that the redshift evolution is primarily driven by the increase of the halo number density due to the structure formation, and the decrease of the accretion rate due to the cosmic expansion. Extrapolating this calculation to higher redshifts assuming the constant efficiency suggests a rapid decrease of the SFR density at
z
> 10 with ∝ 10
−0.5(1+
z
)
, which will be directly tested with the James Webb Space Telescope.
Abstract
Using data from JWST, we analyse the compact sources (“sparkles”) located around a remarkable
z
spec
= 1.378 galaxy (the ‘Sparkler) that is strongly gravitationally lensed by the
z
= 0.39 ...galaxy cluster SMACS J0723.3-7327. Several of these compact sources can be cross-identified in multiple images, making it clear that they are associated with the host galaxy. Combining data from JWSTs Near-Infrared Camera (NIRCam) with archival data from the Hubble Space Telescope (HST), we perform 0.4–4.4
μ
m photometry on these objects, finding several of them to be very red and consistent with the colors of quenched, old stellar systems. Morphological fits confirm that these red sources are spatially unresolved even in the strongly magnified JWST/NIRCam images, while the JWST/NIRISS spectra show O
iii
λ
5007 emission in the body of the Sparkler but no indication of star formation in the red compact sparkles. The most natural interpretation of these compact red companions to the Sparkler is that they are evolved globular clusters seen at
z
= 1.378. Applying
Dense Basis
spectral energy distribution fitting to the sample, we infer formation redshifts of
z
form
∼ 7–11 for these globular cluster candidates, corresponding to ages of ∼3.9–4.1 Gyr at the epoch of observation and a formation time just ∼0.5 Gyr after the Big Bang. If confirmed with additional spectroscopy, these red, compact sparkles represent the first evolved globular clusters found at high redshift, which could be among the earliest observed objects to have quenched their star formation in the universe, and may open a new window into understanding globular cluster formation. Data and code to reproduce our results will be made available at
http://canucs-jwst.com/sparkler.html
.
We present an original phenomenological model to describe the evolution of galaxy number counts, morphologies, and spectral energy distributions across a wide range of redshifts ( ) and stellar ...masses . Our model follows observed mass and luminosity functions of both star-forming and quiescent galaxies, and reproduces the redshift evolution of colors, sizes, star formation, and chemical properties of the observed galaxy population. Unlike other existing approaches, our model includes a self-consistent treatment of stellar and photoionized gas emission and dust attenuation based on the beagle tool. The mock galaxy catalogs generated with our new model can be used to simulate and optimize extragalactic surveys with future facilities such as the James Webb Space Telescope (JWST), and to enable critical assessments of analysis procedures, interpretation tools, and measurement systematics for both photometric and spectroscopic data. As a first application of this work, we make predictions for the upcoming JWST Advanced Deep Extragalactic Survey (JADES), a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations teams. We show that JADES will detect, with NIRCam imaging, 1000s of galaxies at z 6, and 10s at z 10 at (5 ) within the 236 arcmin2 of the survey. The JADES data will enable accurate constraints on the evolution of the UV luminosity function at z > 8, and resolve the current debate about the rate of evolution of galaxies at z 8. Ready-to-use mock catalogs and software to generate new realizations are publicly available as the JAdes extraGalactic Ultradeep Artificial Realizations (JAGUAR) package.
ABSTRACT
We measure the colour evolution and quenching time-scales of z = 1.0–1.8 galaxies across the green valley. We derive rest-frame NUVrK colours and select blue-cloud, green-valley, and ...red-sequence galaxies from the spectral energy distribution modelling of CANDELS GOODS-South and UDS multiband photometry. Separately, we constrain the star-formation history (SFH) parameters (ages, τ) of these galaxies by fitting their deep archival HST grism spectroscopy. We derive the galaxy colour–age relation and show that only rapidly evolving galaxies with characteristic delayed-τ SFH time-scales of <0.5 Gyr reach the red sequence at these redshifts, after a period of accelerated colour evolution across the green valley. These results indicate that the stellar mass build-up of these galaxies stays minimal after leaving the blue cloud and entering the green valley (i.e. it may represent $\lesssim 5{{\ \rm per\ cent}}$ of the galaxies’ final, quiescent masses). Visual inspection of age-sensitive features in the stacked spectra also supports the view that these galaxies follow a quenching sequence along the blue-cloud → green-valley → red-sequence track. For this rapidly evolving population, we measure a green-valley crossing time-scale of $0.99^{+0.42}_{-0.25}$ Gyr and a crossing rate at the bottom of the green valley of $0.82^{+0.27}_{-0.25}$ mag Gyr−1. Based on these time-scales, we estimate that the number density of massive (M⋆ > 1010M⊙) red-sequence galaxies doubles every Gyr at these redshifts, in remarkable agreement with the evolution of the quiescent galaxy stellar mass function. These results offer a new approach to measuring galaxy quenching over time and represent a pathfinder study for future JWST, Euclid, and Roman Space Telescope programs.
Abstract Theoretical models predict that z ≳ 6 quasars are hosted in the most massive halos of the underlying dark matter distribution and thus would be immersed in protoclusters of galaxies. ...However, observations report inconclusive results. We investigate the 1.1 proper-Mpc 2 environment of the z = 7.54 luminous quasar ULAS J1342+0928. We search for Lyman-break galaxy (LBG) candidates using deep imaging from the Hubble Space Telescope (HST) in the Advanced Camera for Surveys (ACS)/F814W, Wide Field Camera 3 (WFC3)/F105W/F125W bands, and Spitzer/Infrared Array Camera at 3.6 and 4.5 μ m. We report a z phot = 7.69 − 0.23 + 0.33 LBG with mag F125W = 26.41 at 223 projected proper kpc (pkpc) from the quasar. We find no HST counterpart to one C ii emitter previously found with the Atacama Large millimeter/submillimeter Array (ALMA) at 27 projected pkpc and z C II =7.5341 ± 0.0009 (Venemans et al. 2020). We estimate the completeness of our LBG candidates using results from Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey/GOODS deep blank field searches sharing a similar filter setup. We find that >50% of the z ∼ 7.5 Lyman-break galaxies (LBGs) with mag F125W > 25.5 are missed due to the absence of a filter redward of the Lyman break in F105W, hindering the UV color accuracy of the candidates. We conduct a QSO-LBG clustering analysis revealing a low LBG excess of 0.46 − 0.08 + 1.52 in this quasar field, consistent with an average or low-density field. Consequently, this result does not present strong evidence of an LBG overdensity around ULAS J1342+0928. Furthermore, we identify two LBG candidates with a z phot matching a confirmed z = 6.84 absorber along the line of sight to the quasar. All these galaxy candidates are excellent targets for follow-up observations with JWST and/or ALMA to confirm their redshift and physical properties.
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