Dr Aayush Saxena

Abstract:

The James Webb Space Telescope (JWST) has spectroscopically confirmed numerous galaxies at z > 10. While weak rest-frame ultraviolet emission lines have only been seen in a handful of sources, the stronger rest-frame optical emission lines are highly diagnostic and accessible at mid-infrared wavelengths with the Mid-Infrared Instrument (MIRI) of JWST. We report the photometric detection of the distant spectroscopically confirmed galaxy JADES-GS-z14-0 at z=14.32−0.20+0.08 with MIRI at 7.7 μm. The most plausible solution for the stellar-population properties is that this galaxy contains half a billion solar masses in stars with a strong burst of star formation in the most recent few million years. For this model, at least one-third of the flux at 7.7 μm originates from the rest-frame optical emission lines Hβ and/or [O iii]λλ4959, 5007. The inferred properties of JADES-GS-z14-0 suggest rapid mass assembly and metal enrichment during the earliest phases of galaxy formation. This work demonstrates the unique power of mid-infrared observations in understanding galaxies at the redshift frontier.

Abstract:

We present the third data release of the JWST Advanced Deep Extragalactic Survey (JADES), providing both imaging and spectroscopy in the two GOODS fields. Spectroscopy consists of medium-depth and deep NIRSpec/microshutter assembly spectra of 4000 targets, covering the spectral range 0.6–5.3 μm and observed with both the low-dispersion prism (R = 30–300) and all three medium-resolution gratings (R = 500–1500). We describe the observations, data reduction, sample selection, and target allocation. We measured 2375 redshifts (2053 from multiple emission lines); our targets span the range from z = 0.5 up to z = 13, including 404 at z > 5. The data release includes 2D and 1D fully reduced spectra, with slit-loss corrections and background subtraction optimized for point sources. We also provide redshifts and signal-to-noise ratio > 5 emission-line flux catalogs for the prism and grating spectra, and concise guidelines on how to use these data products. Alongside spectroscopy, we are also publishing fully calibrated NIRCam imaging, which enables studying the JADES sample with the combined power of imaging and spectroscopy. Together, these data provide the largest statistical sample to date to characterize the properties of galaxy populations in the first billion years after the Big Bang.

Abstract:

We present the discovery of a large extended radio jet associated with the extremely radio-loud quasar J1601+3102 at z ∼​​​​​ 5 from subarcsecond resolution imaging at 144 MHz with the International LOFAR Telescope. These large radio lobes have been argued to remain elusive at z > 4 due to energy losses in the synchrotron emitting plasma as a result of scattering of the strong cosmic microwave background at these high redshifts. Nonetheless, the 0 .′′ 3 resolution radio image of J1601+3102 reveals a northern and a southern radio lobe located at 9 and 57 kpc from the optical quasar, respectively. The measured jet size of 66 kpc makes J1601+3102 the largest extended radio jet at z > 4 to date. However, it is expected to have an even larger physical size in reality due to projection effects brought about by the viewing angle. Furthermore, we observe the rest-frame UV spectrum of J1601+3102 with Gemini/GNIRS to examine its black hole properties, which results in a mass of 4.5 × 108 M⊙ with an Eddington luminosity ratio of 0.45. The black hole mass is relatively low compared to the known high-z quasar population, which suggests that a high black hole mass is not strictly necessary to generate a powerful jet. This discovery of the first ∼​​​​​100 kpc radio jet at z > 4 shows that these objects exist despite energy losses from inverse Compton scattering and can put invaluable constraints on the formation of the first radio-loud sources in the early Universe.