Andrew Bunker

Abstract:

The JWST Advanced Deep Extragalactic Survey (JADES) is a multicycle JWST program that has taken among the deepest near- and mid-infrared images to date (down to ∼30 AB mag) over ∼25 arcmin2 in the GOODS-S field in two sets of observations with 1 yr of separation. This presented the first opportunity to systematically search for transients, mostly supernovae (SNe), out to z > 2. We found 79 SNe: 38 at z < 2, 23 at 2 < z < 3, 8 at 3 < z < 4, 7 at 4 < z < 5, and 3 with undetermined redshifts, where the redshifts are predominantly based on spectroscopic or highly reliable JADES photometric redshifts of the host galaxies. At this depth, the detection rate is ∼1–2 arcmin–2 yr–1, demonstrating the power of JWST as an SN discovery machine. We also conducted multiband follow-up NIRCam observations of a subset of the SNe to better constrain their light curves and classify their types. Here, we present the survey, sample, search parameters, spectral energy distributions, light curves, and classifications. Even at z ≥ 2, the NIRCam data quality is high enough to allow SN classification via multiepoch light-curve fitting with confidence. The multiepoch SN sample includes a Type Ia SN at z spec = 2.90, a Type IIP SN at z spec = 3.61, and a Type Ic-BL SN at z spec = 2.83. We also found that two z ∼ 16 galaxy candidates from the first imaging epoch were actually transients that faded in the second epoch, illustrating the possibility that moderate/high-redshift SNe could mimic high-redshift dropout galaxies.

Abstract:

Recently, a large number of compact sources at z > 4 with blue UV slopes and extremely red rest-frame optical slopes have been found in James Webb Space Telescope (JWST) extragalactic surveys. As a subsample of these sources, commonly called “little red dots” (LRDs), have been spectroscopically observed to host a broad-line active galactic nucleus (AGN), they have been the focus of multiple recent studies in an attempt to understand the origin of their UV and optical emission. Here, we assemble a sample of 123 LRDs from the literature along with spectroscopic and photometric JWST-identified samples of AGNs to compare their colors and spectral slopes. We find that while obscured AGNs at z < 6 have highly dissimilar colors to LRDs, unobscured AGNs at z < 6 span a wide range of colors, with only a subsample showing colors similar to LRDs. At z > 6, the majority of the unobscured AGNs that have been found in these samples are LRDs, but this may be related to the fact that these sources are at large bolometric luminosities. Because LRDs occupy a unique position in galaxy color space, they are more straightforward to target, and the large number of broad-line AGNs that do not have LRD colors and slopes are therefore underrepresented in many spectroscopic surveys because they are more difficult to preselect. Current LRD selection techniques return a large and disparate population, including many sources having 2–5 μm colors impacted by emission-line flux boosting in individual filters.