ABSTRACT
We report ALMA Band 9 continuum observations of the normal, dusty star-forming galaxy A1689-zD1 at z = 7.13, resulting in a ∼4.6 σ detection at 702 GHz. For the first time, these ...observations probe the far-infrared spectrum shortward of the emission peak of a galaxy in the Epoch of Reionization (EoR). Together with ancillary data from earlier works, we derive the dust temperature, Td, and mass, Md, of A1689-zD1 using both traditional modified blackbody spectral energy density fitting, and a new method that relies only on the C ii 158 μm line and underlying continuum data. The two methods give $T_{\rm d} = (42^{+13}_{-7}, 40^{+13}_{-7}$) K, and $M_{\rm d} = (1.7^{+1.3}_{-0.7}, 2.0^{+1.8}_{-1.0})\, \times {}\, 10^{7} \, \mathrm{ M}_{\odot }$. Band 9 observations improve the accuracy of the dust temperature (mass) estimate by ∼50 per cent (6 times). The derived temperatures confirm the reported increasing Td-redshift trend between z = 0 and 8; the dust mass is consistent with a supernova origin. Although A1689-zD1 is a normal UV-selected galaxy, our results, implying that ∼85 per cent of its star-formation rate is obscured, underline the non-negligible effects of dust in EoR galaxies.
ABSTRACT We present statistics of 133 faint 1.2 mm continuum sources detected in about 120 deep Atacama Large Millimeter/submillimeter Array (ALMA) pointing data that include all the archival deep ...data available by 2015 June. We derive number counts of 1.2 mm continuum sources down to 0.02 mJy partly with the assistance of gravitational lensing, and find that the total integrated 1.2 mm flux of the securely identified sources is Jy deg−2 which corresponds to of the extragalactic background light (EBL) measured by Cosmic Background Explorer observations. These results suggest that the major 1.2 mm EBL contributors are sources with 0.02 mJy, and that very faint 1.2 mm sources with 0.02 mJy contribute negligibly to the EBL with the possible flattening and/or truncation of number counts in this very faint flux regime. To understand the physical origin of our faint ALMA sources, we measure the galaxy bias bg by the counts-in-cells technique, and place a stringent upper limit of bg < 3.5 that is not similar to bg values of massive distant red galaxies and submillimeter galaxies but comparable to those of UV-bright, star-forming BzK galaxies (sBzKs) and Lyman break galaxies (LBGs). Moreover, in the optical and near-infrared (NIR) deep fields, we identify optical-NIR counterparts for 59% of our faint ALMA sources, the majority of which have luminosities, colors, and the IRX-β relation the same as sBzKs and LBGs. We thus conclude that about a half of our faint ALMA sources are dust-poor, high-z galaxies as known as sBzKs and LBGs in optical studies, and that these faint ALMA sources are not miniature (U)LIRGs simply scaled down with the infrared brightness.
Gravitational lensing sometimes dominates the observed properties of apparently very bright objects. We present morphological properties in the high-resolution (FWHM ∼ 0 15) Atacama Large ...Millimeter/submillimeter Array (ALMA) 1 mm map for an ultraluminous quasar at z = 6.30, SDSS J010013.02+280225.8 (hereafter J0100+2802), whose black hole (BH) mass MBH is the most massive (∼1.2 × 1010M ) at z > 6 ever known. We find that the continuum emission of J0100+2802 is resolved into a quadruple system within a radius of 0 2, which can be interpreted as either multiple dusty star-forming regions in the host galaxy or multiple images due to strong gravitational lensing. The Mg ii absorption and the potential Ly line features have been identified at z = 2.33 in the near-infrared spectroscopy toward J0100+2802, and a simple mass model fitting well reproduces the positions and flux densities of the quadruple system, both of which are consistent with the latter interpretation. Although a high-resolution map taken in the Advanced Camera for Survey on board Hubble Space Telescope (HST) shows a morphology with an apparently single component, in our fiducial lens mass model it can simply be explained by a ∼50 pc scale offset between the ALMA and HST emission regions. In this case, the magnification factor for the observed HST emission is obtained to ∼450, reducing the intrinsic MBH estimate to below 109 M . The confirmation or the rejection of the gravitational lensing scenario is important for our understanding of the supermassive BHs in the early universe.
Abstract We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy ...formation from z ∼ 0.5 to >10 using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 arcmin 2 , to search for candidate galaxies at z > 9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multiband photometry across seven NIRCam broad- and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z ∼ 9–16. These objects are compact with a median half-light radius of ∼0.5 kpc. We present an early estimate of the z ∼ 11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M UV ∼ −20 appears to evolve very little from z ∼ 9 to 11. We also find that the abundance (surface density arcmin −2 ) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z > 10, star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific samples of ultrahigh-redshift galaxies with which to further explore these conclusions.
Abstract
We report the discovery of an accreting supermassive black hole at
z
= 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Ly
α
-break galaxy by Hubble with a Ly
α
...redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The H
β
line is best fit by a narrow plus a broad component, where the latter is measured at 2.5
σ
with an FWHM ∼1200 km s
−1
. We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV, and C III), as well as a spatial point-source component. The implied mass of the black hole (BH) is log (
M
BH
/
M
⊙
) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1–8
μ
m photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M
⊙
∼9.5) and highly star-forming (star formation rate, or SFR ∼ 30 M
⊙
yr
−1
; log sSFR ∼ − 7.9 yr
−1
). The line ratios show that the gas is metal-poor (
Z
/
Z
⊙
∼ 0.1), dense (
n
e
∼ 10
3
cm
−3
), and highly ionized (log
U
∼ − 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object.
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 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.
Abstract We report on the discovery of two low-luminosity, broad-line active galactic nuclei (AGNs) at z > 5 identified using JWST NIRSpec spectroscopy from the Cosmic Evolution Early Release Science ...(CEERS) survey. We detect broad H α emission in the spectra of both sources, with FWHM of 2060 ± 290 km s −1 and 1800 ± 200 km s −1 , resulting in virial black hole (BH) masses that are 1–2 dex below those of existing samples of luminous quasars at z > 5. The first source, CEERS 2782 at z = 5.242, is 2–3 dex fainter than known quasars at similar redshifts and was previously identified as a candidate low-luminosity AGN based on its morphology and rest-frame optical spectral energy distribution (SED). We measure a BH mass of M BH = (1.3 ± 0.4) × 10 7 M ⊙ , confirming that this AGN is powered by the least massive BH known in the Universe at the end of cosmic reionization. The second source, CEERS 746 at z = 5.624, is inferred to be a heavily obscured, broad-line AGN caught in a transition phase between a dust-obscured starburst and an unobscured quasar. We estimate its BH mass to be in the range of M BH ≃ (0.9–4.7) × 10 7 M ⊙ , depending on the level of dust obscuration assumed. We perform SED fitting to derive host stellar masses, M ⋆ , allowing us to place constraints on the BH–galaxy mass relationship in the lowest mass range yet probed in the early Universe. The M BH / M ⋆ ratio for CEERS 2782, in particular, is consistent with or higher than the empirical relationship seen in massive galaxies at z = 0. We examine the narrow emission line ratios of both sources and find that their location on the BPT and OHNO diagrams is consistent with model predictions for moderately low metallicity AGNs with Z / Z ⊙ ≃ 0.2–0.4. The spectroscopic identification of low-luminosity, broad-line AGNs at z > 5 with M BH ≃ 10 7 M ⊙ demonstrates the capability of JWST to push BH masses closer to the range predicted for the BH seed population and provides a unique opportunity to study the early stages of BH–galaxy assembly.
Abstract We present the results of a systematic search for candidate quiescent galaxies in the distant universe in 11 JWST fields with publicly available observations collected during the first 3 ...months of operations and covering an effective sky area of ∼145 arcmin 2 . We homogeneously reduce the new JWST data and combine them with existing observations from the Hubble Space Telescope. We select a robust sample of ∼80 candidate quiescent and quenching galaxies at 3 < z < 5 using two methods: (1) based on their rest-frame UVJ colors, and (2) a novel quantitative approach based on Gaussian mixture modeling of the near-UV − U , U − V , and V − J rest-frame color space, which is more sensitive to recently quenched objects. We measure comoving number densities of massive ( M ⋆ ≥ 10 10.6 M ⊙ ) quiescent galaxies consistent with previous estimates relying on ground-based observations, after homogenizing the results in the literature with our mass and redshift intervals. However, we find significant field-to-field variations of the number densities up to a factor of 2–3, highlighting the effect of cosmic variance and suggesting the presence of overdensities of red quiescent galaxies at z > 3, as could be expected for highly clustered massive systems. Importantly, JWST enables the robust identification of quenching/quiescent galaxy candidates at lower masses and higher redshifts than before, challenging standard formation scenarios. All data products, including the literature compilation, are made publicly available.
Abstract We present the first spatially resolved measurements of galaxy properties in the JWST ERO SMACS 0723 field. We perform a comprehensive analysis of five 5 < z < 9 galaxies with spectroscopic ...redshifts from NIRSpec observations. We perform spatially resolved spectral energy distribution fitting with Bagpipes , using six NIRCam imaging bands spanning the wavelength range 0.8–5 μ m. This approach allows us to study the internal structure and assembly of the first generations of galaxies. We find clear gradients both in the empirical color maps and in most of the estimated physical parameters. We find regions of considerably different specific star formation rates across each galaxy, which points to very bursty star formation happening on small scales, not galaxy-wide. The integrated light is dominated by these bursty regions, which exhibit strong line emission, with the equivalent width of O iii +H β reaching up to ∼3000–4000 Å rest frame. Studying these galaxies in an integrated approach yields extremely young inferred ages of the stellar population (<10 Myr), which outshine older stellar populations that are only distinguishable in the spatially resolved maps. This leads to inferring ∼0.5–1 dex lower stellar masses by using single-aperture photometry, when compared to resolved analyses. Such systematics would have strong implications in the shape and evolution of the stellar mass function at these early times, particularly while samples are limited to small numbers of the brightest candidates. Furthermore, the evolved stellar populations revealed in this study imply an extended process of early galaxy formation that could otherwise be hidden behind the light of the most recently formed stars.
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