Following the discovery of SAGE0536AGN (\(z \sim\) 0.14), with the strongest 10-\(\mu\)m silicate emission ever observed for an Active Galactic Nucleus (AGN), we discovered SAGE0534AGN (\(z \sim\) ...1.01), a similar AGN but with less extreme silicate emission. Both were originally mistaken as evolved stars in the Magellanic Clouds. Lack of far-infrared emission, and therefore star-formation, implies we are seeing the central engine of the AGN without contribution from the host galaxy. They could be a key link in galaxy evolution. We used a dimensionality reduction algorithm, t-SNE (t-distributed Stochastic Neighbourhood Embedding) with multi-wavelength data from Gaia EDR3, VISTA survey of the Magellanic Clouds, AllWISE and the Australian SKA Pathfinder to find these two unusual AGN are grouped with 16 other objects separated from the rest, suggesting a rare class. Our spectroscopy at SAAO/SALT and literature data confirm at least 14 of these objects are extragalactic (\(0.13 < z < 1.23\)), all hosting AGN. Using spectral energy distribution fitter CIGALE we find that the majority of dust emission (\(> 70 \%\)) in these sources is due to the AGN. Host galaxies appear to be either in or transitioning into the green valley. There is a trend of a thinning torus, increasing X-ray luminosity and decreasing Eddington ratio as the AGN transition through the green valley, implying that as the accretion supply depletes, the torus depletes and the column density reduces. Also, the near-infrared variability amplitude of these sources correlates with attenuation by the torus, implying the torus plays a role in the variability.
In this letter, we report the discovery of the highest redshift, heavily obscured, radio-loud AGN candidate selected using JWST NIRCam/MIRI, mid-IR, sub-mm, and radio imaging in the COSMOS-Web field. ...Using multi-frequency radio observations and mid-IR photometry, we identify a powerful, radio-loud (RL), growing supermassive black hole (SMBH) with significant spectral steepening of the radio SED (\(f_{1.28 \mathrm{GHz}} \sim 2\) mJy, \(q_{24\mu m} = -1.1\), \(\alpha_{1.28-3\mathrm{GHz}}=-1.2\), \(\Delta \alpha = -0.4\)). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/NIR data and thus infer heavy amounts of obscuration (N\(_{\mathrm{H}} > 10^{23}\) cm\(^{-2}\)). Using the wealth of deep UV to sub-mm photometric data, we report a singular solution photo-z of \(z_\mathrm{phot}\) = 7.7\(^{+0.4}_{-0.3}\) and estimate an extremely massive host-galaxy (\(\log M_{\star} = 11.4 -12\,\mathrm{M}_{\odot}\)) hosting a powerful, growing SMBH (L\(_{\mathrm{Bol}} = 4-12 \times 10^{46}\) erg s\(^{-1}\)). This source represents the furthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs.
We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hour treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web is a ...contiguous 0.54 deg\(^2\) NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5\(\sigma\) point source depths ranging \(\sim\)27.5-28.2 magnitudes. In parallel, we will obtain 0.19 deg\(^2\) of MIRI imaging in one filter (F770W) reaching 5\(\sigma\) point source depths of \(\sim\)25.3-26.0 magnitudes. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization (\(6<z<11\)) and map reionization's spatial distribution, environments, and drivers on scales sufficiently large to mitigate cosmic variance, (2) to identify hundreds of rare quiescent galaxies at \(z>4\) and place constraints on the formation of the Universe's most massive galaxies (\(M_\star>10^{10}\)\,M\(_\odot\)), and (3) directly measure the evolution of the stellar mass to halo mass relation using weak gravitational lensing out to \(z\sim2.5\) and measure its variance with galaxies' star formation histories and morphologies. In addition, we anticipate COSMOS-Web's legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool sub-dwarf stars in the Galactic halo, and possibly the identification of \(z>10\) pair-instability supernovae. In this paper we provide an overview of the survey's key measurements, specifications, goals, and prospects for new discovery.
We present the results of a search for galaxy clusters and groups in the \(\sim2\) square degree of the COSMOS field using all available X-ray observations from the XMM-Newton and Chandra ...observatories. We reach an X-ray flux limit of \(3\times10^{-16}\;ergs\;cm^{-2}\;s^{-1}\) in 0.5--2 keV range, and identify 247 X-ray groups with \(M_{200c}=8\times10^{12}-3\times10^{14}\;M_{\odot}\) at a redshift range of \(0.08\leq z<1.53\), using the multiband photometric redshift and the master spectroscopic redshift catalogues of the COSMOS. The X-ray centres of groups are determined using high-resolution Chandra imaging. We investigate the relations between the offset of the brightest group galaxies (BGGs) from halo X-ray centre and group properties and compare with predictions from semi-analytic models and hydrodynamical simulations. We find that BGG offset decreases with both increasing halo mass and decreasing redshift with no strong dependence on the X-ray flux and SNR. We show that the BGG offset decreases as a function of increasing magnitude gap with no considerable redshift dependent trend. The stellar mass of BGGs in observations extends over a wider dynamic range compared to model predictions. At \(z<0.5\), the central dominant BGGs become more massive than those with large offsets by up to 0.3dex, in agreement with model prediction. The observed and predicted lognormal scatter in the stellar mass of both low- and large-offset BGGs at fixed halo mass is \(\sim0.3\)dex.
