We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from the Cosmic Evolution Early Release Science Survey (CEERS) NIRCam imaging with photometric redshifts z_phot>8. We measure ...emission line redshifts of z=7.65 and 8.64 for two galaxies, and z=9.77(+0.37,-0.29) and 10.01(+0.14,-0.19) for two others via the detection of continuum breaks consistent with Lyman-alpha opacity from a mostly neutral intergalactic medium. The presence (absense) of strong breaks (strong emission lines) give high confidence that these two galaxies are at z>9.6, but the break-derived redshifts have large uncertainties given the low spectral resolution and relatively low signal-to-noise of the CEERS NIRSpec prism data. The two z~10 sources are relatively luminous (M_UV<-20), with blue continua (-2.3<beta<-1.9) and low dust attenuation (A_V=0.15(+0.3,-0.1)); and at least one of them has high stellar mass for a galaxy at that redshift (log(M_*/M_sol)=9.3(+0.2,-0.3)). 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 (8.3%). Ten out of 34 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 uncertainties) with the spectroscopic values. However, the photometric redshifts tend to be slightly overestimated (average Delta(z)=0.50+/-0.12), suggesting that current templates do not fully describe the spectra of very high-z sources. Overall, our results solidifies photometric evidence for a high space 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.
We present results from the Cosmic Evolution Early Release Survey (CEERS) on the stellar-population parameters for 28 galaxies with redshifts \(4<z<9\) using imaging data from the James Webb Space ...Telescope (JWST) Mid-Infrared Instrument (MIRI) combined with data from the Hubble Space Telescope and the Spitzer Space Telescope. The JWST/MIRI 5.6 and 7.7 \(\mu\)m data extend the coverage of the rest-frame spectral-energy distribution (SED) to nearly 1 micron for galaxies in this redshift range. By modeling the galaxies' SEDs the MIRI data show that the galaxies have, on average, rest-frame UV (1600 Å) \(-\) \(I\)-band colors 0.4 mag bluer than derived when using photometry that lacks MIRI. Therefore, the galaxies have lower (stellar)-mass-to-light ratios. The MIRI data reduce the stellar masses by \(\langle \Delta\log M_\ast\rangle=0.25\) dex at \(4<z<6\) (a factor of 1.8) and 0.37 dex at \(6<z<9\) (a factor of 2.3). This also reduces the star-formation rates (SFRs) by \(\langle \Delta\log\mathrm{SFR} \rangle=0.14\) dex at \(4<z<6\) and 0.27 dex at \(6<z<9\). The MIRI data also improve constraints on the allowable stellar mass formed in early star-formation. We model this using a star-formation history that includes both a "burst' at \(z_f=100\) and a slowly varying ("delayed-\(\tau\)") model. The MIRI data reduce the allowable stellar mass by 0.6 dex at \(4<z< 6\) and by \(\approx\)1 dex at \(6<z<9\). Applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early universe (\(z\approx9\)). Therefore, observations of rest-frame \(\gtrsim\)1 \(\mu\)m are paramount for constraining the stellar-mass build-up in galaxies at very high-redshifts.
We present the results of a systematic search for Lyman-alpha emitters (LAEs) at \(6 \lesssim z \lesssim 7.6\) using the HST WFC3 Infrared Spectroscopic Parallel (WISP) Survey. Our total volume over ...this redshift range is \(\sim 8 \times10^5\) Mpc\(^3\), comparable to many of the narrowband surveys despite their larger area coverage. We find two LAEs at \(z=6.38\) and \(6.44\) with line luminosities of L\(_{\mathrm{Ly}\alpha} \sim 4.7 \times 10^{43}\) erg s\(^{-1}\), putting them among the brightest LAEs discovered at these redshifts. Taking advantage of the broad spectral coverage of WISP, we are able to rule out almost all lower-redshift contaminants. The WISP LAEs have a high number density of \(7.7\times10^{-6}\) Mpc\(^{-3}\). We argue that the LAEs reside in Mpc-scale ionized bubbles that allow the Lyman-alpha photons to redshift out of resonance before encountering the neutral IGM. We discuss possible ionizing sources and conclude that the observed LAEs alone are not sufficient to ionize the bubbles.
Abstract
The most luminous quasars at
z
> 6 are suspected to be both highly clustered and to reside in the most massive dark matter halos in the early universe, making them prime targets to search ...for galaxy overdensities and/or protoclusters. We search for Lyman-break dropout-selected galaxies using HST WFC3/ACS broadband imaging in the fields of three 6 <
z
< 7 quasars, as well as for their simultaneously observed coordinated parallel fields, and constrain their photometric redshifts using EAZY. One field, J0305-3150, shows a volume density 10× higher than the blank-field UV luminosity function (UVLF) at
M
UV
< −20, with tentative evidence of a 3
σ
overdensity in its parallel field located 15 cMpc away. Another field, J2054–0005, shows an angular overdensity within 500 ckpc from the quasar, but this is still consistent with UVLF predictions within 3
σ
, while the last field, J2348–3054, shows no enhancement. We discuss methods for reducing uncertainty in overdensity measurements when using photometric selection and show that we can robustly select Lyman-break galaxies (LBGs) consistent with being physically associated with the quasar, corroborated by existing JWST/NIRCam WFSS data in the J0305 field. Even accounting for incompleteness, the overdensities in J0305 and J2054 are higher for brighter galaxies at short angular separations, suggesting preferential enhancement of more massive galaxies in the quasar’s immediate vicinity. Finally, we compare the population of LBGs with previously identified C
ii
and millimeter-continuum companions. The LBG overdensities are not accompanied by an enhanced number of dusty galaxies, suggesting that the overdense quasar fields are not in the bursty star-forming phase sometimes seen in high-redshift protoclusters.
An N-body hybrid simulation, integrating both massive and tracer particles, of a Galactic disk is used to study the stellar phase space distribution or velocity distributions in different local ...neighborhoods. Pattern speeds identified in Fourier spectrograms suggest that two-armed and three-armed spiral density waves, a bar and a lopsided motion are coupled in this simulation, with resonances of one pattern lying near resonances of other patterns. We construct radial and tangential (uv) velocity distributions from particles in different local neighborhoods. More than one clump is common in these local velocity distributions regardless of the position in the disk. Features in the velocity distribution observed at one galactic radius are also seen in nearby neighborhoods (at larger and smaller radii) but with shifted mean v values. This is expected if the v velocity component of a clump sets the mean orbital galactic radius of its stars. We find that gaps in the velocity distribution are associated with the radii of kinks or discontinuities in the spiral arms. These gaps also seem to be associated with Lindblad resonances with spiral density waves and so denote boundaries between different dominant patterns in the disk. We discuss implications for interpretations of the Milky Way disk based on local velocity distributions. Velocity distributions created from regions just outside the bar's Outer Lindblad resonance and with the bar oriented at 45 degrees from the Sun-Galactic center line more closely resemble that seen in the solar neighborhood (triangular in shape at lower uv and with a Hercules like stream) when there is a strong nearby spiral arm, consistent with the observed Centaurus Arm tangent, just interior to the solar neighborhood.
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
Low-mass (sub)stellar objects represent the low end of the initial mass function, the transition to free-floating planets and a prominent interloper population in the search for ...high-redshift galaxies. To what accuracy can photometry only classify these? JWST/NIRCam has several advantages over Hubble Space Telescope (HST)/WFC3 near-infrared (NIR): more filters, a greater wavelength range, and greater spatial resolution. Here, we present a catalogue of (sub)stellar dwarfs identified in the cosmic evolution early release science survey (CEERS). We identify 518 stellar objects down to mF200W 28 using half-light radius, a full three magnitudes deeper than typical HST/WFC3 images. A k-means nearest neighbour (kNN) algorithm identifies and types these sources, using four HST/WFC3 and four NIRCam filters, trained on IRTF/spex spectra of nearby brown dwarfs. The kNN with four neighbours classifies well within two subtypes: e.g. M2±2, achieving ∼95 per cent precision and recall. In CEERS, we find 9 M8±2, 2 L6±2, 1 T4±2, and 15 T8±2. We compare the observed long wavelength NIRCam colours – not used in the kNN – to those expected for brown dwarf atmospheric models. The NIRCam F356W−F444W and F410M−F444W colours are redder by a magnitude for the type assigned by the kNN, hinting at a wider variety of atmospheres for these objects. We find a 300–350 pc scale height for M6±2 dwarfs plus a second structural component and a 150–200 pc scale height for T6±2 type dwarfs, consistent with literature values. A single M8±2 dwarf is spectroscopically confirmed at 4 kpc distance.
The most luminous quasars at $z > 6$ are suspected to be both highly
clustered and reside in the most massive dark matter halos in the early
Universe, making them prime targets to search for galaxy ...overdensities and/or
protoclusters. We search for Lyman-break dropout-selected galaxies using HST
WFC3/ACS broadband imaging in the fields of three $6 < z < 7$ quasars, as well
as their simultaneously observed coordinated-parallel fields, and constrain
their photometric redshifts using EAZY. One field, J0305-3150, shows a volume
density 10$\times$ higher than the blank-field UV luminosity function (UVLF) at
M$_{UV} < -20$, with tentative evidence of a 3$\sigma$ overdensity in its
parallel field located 15 cMpc away. Another field, J2054-0005, shows an
angular overdensity within 500 ckpc from the quasar but still consistent with
UVLF predictions within 3$\sigma$, while the last field, J2348-3054, shows no
enhancement. We discuss methods for reducing uncertainty in overdensity
measurements when using photometric selection and show that we can robustly
select LBGs consistent with being physically associated with the quasar,
corroborated by existing JWST/NIRCam WFSS data in the J0305 field. Even
accounting for incompleteness, the overdensities in J0305 and J2054 are higher
for brighter galaxies at short angular separations, suggesting preferential
enhancement of more massive galaxies in the immediate vicinity of the quasar.
Finally, we compare the LBG population with previously-identified CII and
mm-continuum companions; the LBG overdensities are not accompanied by an
enhanced number of dusty galaxies, suggesting that the overdense quasar fields
are not in the bursty star-forming phase sometimes seen in high-redshift
protoclusters.
Low mass (sub)stellar objects represent the low end of the initial mass function, the transition to free-floating planets and a prominent interloper population in the search for high-redshift ...galaxies. Without proper motions or spectroscopy, can one identify these objects photometrically? JWST/NIRCam has several advantages over HST/WFC3 NIR: more filters, a greater wavelength range, and greater spatial resolution. Here, we present a catalogue of (sub)stellar dwarfs identified in the Cosmic Evolution Early Release Science Survey (CEERS). We identify 518 stellar objects down to \(m_F200W \sim 28\) using half-light radius, a full three magnitudes deeper than typical HST/WFC3 images. A kNN nearest neighbour algorithm identifies and types these sources, using four HST/WFC3 and four NIRCam filters, trained on SpeX spectra of nearby brown dwarfs. The kNN with four neighbors classifies well within two subtypes: e.g M2\(\pm\)2 or T4\(\pm\)2, achieving \(\sim\)95% precision and recall. More granular typing results in worse metrics. In CEERS, we find 9 M8\(\pm\)2, 2 L6\(\pm\)2, 1 T4\(\pm\)2, and 15 T8\(\pm\)2. We compare the observed long wavelength NIRCam colours -- not used in the kNN -- to those expected for brown dwarf atmospheric models. The NIRCam F356W-F444W and F410M-F444W colours are redder by a magnitude for the type assigned by the kNN, hinting at a wider variety of atmospheres for these objects. We find a 300-350pc scale-height for M6\(\pm\)2 dwarfs plus a second structural component and a 150-200pc scale-height for T6\(\pm\)2 type dwarfs, consistent with literature values.
We report the discovery of an accreting supermassive black hole at z=8.679, in CEERS_1019, a galaxy previously discovered via a Ly\(\alpha\)-break by Hubble and with a Ly\(\alpha\) redshift from ...Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we observed this source with JWST/NIRSpec spectroscopy, MIRI and NIRCam imaging, and NIRCam/WFSS slitless spectroscopy. The NIRSpec spectra uncover many emission lines, and the strong O III emission line confirms the ground-based Ly\(\alpha\) redshift. We detect a significant broad (FWHM~1200 km/s) component in the H\(\beta\) emission line, which we conclude originates in the broad-line region of an active galactic nucleus (AGN), as the lack of a broad component in the forbidden lines rejects an outflow origin. This hypothesis is supported by the presence of high-ionization lines, as well as a spatial point-source component embedded within a smoother surface brightness profile. The mass of the black hole is log(\(M_{BH}/M_{\odot})=6.95{\pm}0.37\), and we estimate that it is accreting at 1.2 (\(\pm\)0.5) x the Eddington limit. The 1-8 \(\mu\)m photometric spectral energy distribution (SED) from NIRCam and MIRI shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M\(_{\odot}\)~9.5) and highly star-forming (SFR~30 M\(_{\odot}\) yr\(^{-1}\)). Ratios of the strong emission lines show that the gas in this galaxy is metal-poor (Z/Z\(_{\odot}\)~0.1), dense (n\(_{e}\)~10\(^{3}\) cm\(^{-3}\)), and highly ionized (log U~-2.1), consistent with the general galaxy population observed with JWST at high redshifts. We use this presently highest-redshift AGN discovery to place constraints on black hole seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from massive black hole seeds is required to form this object by the observed epoch.
