Galaxy formation and evolution

Abstract:

We obtain spatially resolved kinematics with the Keck Cosmic Web Imager (KCWI) integral-field spectrograph for a sample of 14 massive ( 11

Abstract:

The James Webb Space Telescope (JWST) discovered 79 transients out to z ∼ 4.8 through the JADES Transient Survey (JTS), but the JTS did not find any z > 5 transients. We present the first photometric evidence of a z > 5 transient/variable source with JWST. The source, AT 2023adya, resides in a zspec = 5.274 galaxy in GOODS-N, which dimmed from mF356W = 26.05 ± 0.02 mag to 26.24 ± 0.02 mag in the rest-frame optical over approximately 2 rest-frame months, producing a clear residual signal in the difference image (mF356W = 28.01 ± 0.17 mag; SNvar = 6.09) at the galaxy center. Shorter-wavelength bands (F090W/F115W) show no rest-frame UV brightness change. Based on its rest-frame V-band absolute magnitude (MV = −18.48 mag), AT 2023adya could be any core-collapse supernova (SN) subtype or an SN Ia. However, due to low SN Ia rates at high redshift, the SN Ia scenario is unlikely. Alternatively, AT 2023adya may be a variable active galactic nucleus (AGN). The NIRCam/Grism spectrum shows no broad Hα emission line (FWHM = 130 ± 26 km s−1), but we cannot exclude the existence of a faint broad line and therefore cannot exclude the AGN scenario. AT 2023adya is unlikely to be a tidal disruption event (TDE) because the TDE models matching the observed brightness changes have low event rates. Although it is not possible to determine AT 2023adya’s nature based on the two-epoch single-band photometry alone, this discovery pushes the transient/variable science frontier past z = 5 and toward the Epoch of Reionization.

Abstract:

The James Webb Space Telescope is revolutionising our ability to understand the host galaxies and local environments of high-z quasars. Here we obtain a comprehensive understanding of the host galaxy of the z=7.08 quasar by combining NIRSpec integral field spectroscopy with NIRCam photometry of the host continuum emission. Our emission-line maps reveal that this quasar host is undergoing a merger with a bright companion galaxy. The quasar host and the companion have similar dynamical masses of ∼10^ M_⊙, suggesting that this is a major galaxy interaction. Through detailed quasar subtraction and SED fitting using the NIRCam data, we obtained an estimate of the host stellar mass of M_*=(3.0^ with M_ for the companion galaxy. Using the Balmer line, we estimated a virial black hole mass of M_ BH M_⊙. Thus has an extreme black hole--stellar mass ratio of M_ BH /M_*=0.63^ which is ∼3 dex larger than expected by the local scaling relations between black hole and stellar mass. is powered by an overmassive black hole with the highest reported black hole--stellar mass ratio in a quasar host that is currently undergoing a major merger. These new insights highlight the power of JWST for measuring and understanding these extreme first quasars.

Abstract:

We present high angular resolution (0.19 arcsec or pc) Atacama Large Millimeter/submillimeter Array observations of the CO(3–2) line emission of the galaxy NGC 4751. The data provide evidence for the presence of a central supermassive black hole (SMBH). Assuming a constant mass-to-light ratio (), we infer a SMBH mass M and a F160W filter stellar M/L, where the first uncertainties are statistical and the second systematic. Assuming a linearly spatially varying , we infer M and , where R is the galactocentric radius. We also present SMBH mass estimates using the Jeans Anisotropic Modelling (JAM) method and Very Large Telescope Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) stellar kinematics. Assuming a cylindrically aligned velocity ellipsoid (JAM), we infer M, and while assuming a spherically aligned velocity ellipsoid (JAM), we infer M. The SMBH mass assuming a constant is statistically consistent with that of JAM, whereas the mass assuming a linearly varying is consistent with both JAM and JAM (within the uncertainties). Our derived masses are larger than (and inconsistent with) one previous stellar dynamical measurement using the Schwarzschild orbit-superposition method and the same SINFONI kinematics.