We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous candidate
z
> 10 Lyman break galaxy in the GOODS-North field with
M
UV
= −21.5. We derive a redshift of
z
= 10.603 (lower ...than previous determinations) based on multiple emission lines in our low and medium resolution spectra over 0.7 − 5.3 μm. We significantly detect the continuum and measure a blue rest-UV spectral slope of
β
= −2.4. Remarkably, we see spatially extended Lyman-
α
in emission (despite the highly neutral intergalactic medium expected at this early epoch), offset 555 km s
−1
redwards of the systemic redshift. From our measurements of collisionally excited lines of both low and high ionisation (including O
II
λ
3727, Ne
III
λ
3869, and C
III
λ
1909), we infer a high ionisation parameter (log
U
∼ −2). We detect the rarely seen N
IV
λ
1486 and N
III
λ
1748 lines in both our low and medium resolution spectra, with other high ionisation lines seen in the low resolution spectrum, such as He
II
(blended with O
III
) and C
IV
(with a possible P-Cygni profile). Based on the observed rest-UV line ratios, we cannot conclusively rule out photoionisation from an active galactic nucleus (AGN), although the high C
III
/He
II
and N
III
/He
II
ratios are compatible with a star formation explanation. If the observed emission lines are powered by star formation, then the strong N
III
λ
1748 observed may imply an unusually high
N
/
O
abundance. Balmer emission lines (H
γ
, H
δ
) are also detected, and if powered by star formation rather than an AGN, we infer a star formation rate of ∼20 − 30
M
⊙
yr
−1
(depending on the initial mass function) and low dust attenuation. Our NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme properties seen 430 Myr after the Big Bang.
This article summarizes a workshop held on March, 2014, on the potential of the James Webb Space Telescope (JWST) to revolutionize our knowledge of the physical properties of exoplanets through ...transit observations. JWST's unique combination of high sensitivity and broad wavelength coverage will enable the accurate measurement of transits with high signal-to-noise ratio (S/N). Most importantly, JWST spectroscopy will investigate planetary atmospheres to determine atomic and molecular compositions, to probe vertical and horizontal structure, and to follow dynamical evolution, i.e., exoplanet weather. JWST will sample a diverse population of planets of varying masses and densities in a wide variety of environments characterized by a range of host star masses and metallicities, orbital semi-major axes, and eccentricities. A broad program of exoplanet science could use a substantial fraction of the overall JWST mission.
The James Webb Space Telescope (JWST) will enable the detection of optical emission lines in galaxies spanning a broad range of luminosities out to redshifts z 10. Measurements of key galaxy ...properties, such as star formation rate and metallicity, through these observations will provide unique insight into, e.g., the role of feedback from stars and active galactic nuclei (AGNs) in regulating galaxy evolution, the co-evolution of AGNs and host galaxies, the physical origin of the 'main sequence' of star-forming galaxies and the contribution by star-forming galaxies to cosmic reionization. We present an original framework to simulate and analyse observations performed with the Near Infrared Spectrograph (NIR-Spec) on board JWST. We use the beagle tool (BayEsian Analysis of GaLaxy sEds) to build a semi-empirical catalogue of galaxy spectra based on photometric spectral energy distributions (SEDs) of dropout galaxies in the Hubble Ultra Deep Field (HUDF). We demonstrate that the resulting catalogue of galaxy spectra satisfies different types of observational constraints on high redshift galaxies, and use it as input to simulate NIRSpec/prism (R ∼ 100) observations. We show that a single 'deep' (∼ 100 ks) NIRSpec/prism pointing in the HUDF will enable S/N > 3 detections of multiple optical emission lines in ∼ 30 (∼ 60) galaxies at z 6 (z ∼ 4-6) down to m F160W 30 AB mag. Such observations will allow measurements of galaxy star formation rates, ionization parameters and gas-phase metallicities within factors of 1.5, mass-to-light ratios within a factor of 2, galaxy ages within a factor of 3 and V-band attenuation optical depths with a precision of 0.3.
Abstract
We present 1–5
μ
m spectroscopy of the young planetary mass companion TWA 27B (2M1207B) performed with NIRSpec on board the James Webb Space Telescope. In these data, the fundamental band of ...CH
4
is absent, and the fundamental band of CO is weak. The nondetection of CH
4
reinforces a previously observed trend of weaker CH
4
with younger ages among L dwarfs, which has been attributed to enhanced nonequilibrium chemistry among young objects. The weakness of CO may reflect an additional atmospheric property that varies with age, such as the temperature gradient or cloud thickness. We are able to reproduce the broad shape of the spectrum with an
ATMO
cloudless model that has
T
eff
= 1300 K, nonequilibrium chemistry, and a temperature gradient reduction caused by fingering convection. However, the fundamental bands of CH
4
and CO are somewhat stronger in the model. In addition, the model temperature of 1300 K is higher than expected from evolutionary models given the luminosity and age of TWA 27B (
T
eff
= 1200 K). Previous models of young L-type objects suggest that the inclusion of clouds could potentially resolve these issues; it remains to be seen whether cloudy models can provide a good fit to the 1–5
μ
m data from NIRSpec. TWA 27B exhibits emission in Paschen transitions and the He I triplet at 1.083
μ
m, which are signatures of accretion that provide the first evidence of a circumstellar disk. We have used the NIRSpec data to estimate the bolometric luminosity of TWA 27B (log
L
/
L
⊙
= −4.466 ± 0.014), which implies a mass of 5–6
M
Jup
according to evolutionary models.
We analysed the gas-phase metallicity properties of a sample of low-stellar-mass (log M ⋆ / M ⊙ ≲ 9) galaxies at 3 < z < 10 observed with JWST/NIRSpec as part of the JADES programme in its deep ...GOODS-S tier. By combining this sample with more massive galaxies at similar redshifts from other programmes, we study the scaling relations between stellar mass ( M ⋆ ), oxygen abundance (O/H), and star-formation rate (SFR) for 146 galaxies spanning three orders of magnitude in stellar mass and out to the epoch of early galaxy assembly. We find evidence for a shallower slope at the low-mass end of the mass–metallicity relation (MZR), with 12+log(O/H) = (7.72 ± 0.02) + (0.17 ± 0.03) log( M ⋆ /10 8 M ⊙ ), in good agreement with the MZR probed by local analogues of high-redshift systems, such as the ‘Green Pea’ and ‘Blueberry’ galaxies. The inferred slope is well matched by models including ‘momentum-driven’ supernova (SN) winds, suggesting that feedback mechanisms in dwarf galaxies (and at high z ) might be different from those in place at higher masses. The evolution in the normalisation is observed to be relatively mild compared to previous determinations of the MZR at z ∼ 3 (∼0.1 − 0.2 dex across the explored mass regime). We observe a deviation from the local fundamental metallicity relation (FMR) for our sample at high redshift, especially at z > 6, with galaxies significantly less enriched than predicted given their M ⋆ and SFR (with a median offset in log(O/H) of ∼0.5 dex, significant at ∼5 σ ). These observations are consistent with an enhanced stochasticity in the gas accretion and star-formation history of high-redshift systems, prompting us to reconsider the nature of the relationship between M ⋆ , O/H, and SFR in the early Universe.
The focal plane of the Near Infrared Spectrograph (NIRSpec) instrument on board the James Webb Space Telescope (JWST) is equipped with two Teledyne H2RG near-IR detectors, state-of-the-art HgCdTe ...sensors with excellent noise performance. Once JWST is in space, however, the noise level in NIRSpec exposures will be affected by the cosmic ray (CR) fluence at the JWST orbit and our ability to detect CR hits and to mitigate their effect. We have simulated the effect of CRs on NIRSpec detectors by injecting realistic CR events onto dark exposures that were recently acquired during the JWST cryo-vacuum test campaign undertaken at Johnson Space Flight Center. Here we present the method we have implemented to detect the hits in the exposure integration cubes, to reject the affected data points within our ramp-to-slope processing pipeline (the prototype of the NIRSpec official pipeline), and assess the performance of this method for different choices of the algorithm parameters. Using the optimal parameter set to reject CR hits from the data, we estimate that, for an exposure length of 1000 s, the presence of CRs in space will lead to an increase of typically ∼7% in the detector noise level with respect to the on-ground performance, and the corresponding decrease in the limiting sensitivity of the instrument, for the medium and high-spectral resolution modes.
We investigate the incidence and properties of ionised gas outflows in a sample of 52 galaxies with stellar masses between 10 7 M ⊙ and 10 9 M ⊙ observed with ultra-deep JWST/NIRSpec MSA spectroscopy ...as part of the JWST Advanced Deep Extragalactic Survey (JADES). The high-spectral resolution (R2700) NIRSpec observations allowed us to identify for the first time the potential signature of outflows in the rest-frame optical nebular lines in low-mass galaxies at z > 4. The incidence fraction of ionised outflows, traced by broad components, is about 25–40%, depending on the intensity of the emission lines. The low incidence fraction might be due to both the sensitivity limit and the fact that outflows are not isotropic, but have a limited opening angle, which only results in detection when this is directed toward our line of sight. Evidence for outflows increases slightly with stellar mass and star formation rate. The median velocity and mass-loading factor (i.e. the ratio of the mass outflow rate and star formation rate) of the outflowing ionised gas are 350 km s −1 and η = 2.0 −1.5 +1.6 , respectively. These are 1.5 and 100 times higher than the typical values observed in local dwarf galaxies. Some of these high-redshift outflows can escape the gravitational potential of the galaxy and dark matter halo and enrich the circumgalactic medium and possibly even the intergalactic medium. Our results indicate that outflows can significantly impact the star formation activity in low-mass galaxies within the first 2 Gyr of the Universe.
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