分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the discovery of an extreme galaxy overdensity at $z = 5.4$ in the GOODS-S field using JWST/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam wide field slitless spectroscopy from FRESCO. We identified potential members of the overdensity using HST+JWST photometry spanning $\lambda = 0.4-5.0\ \mu\mathrm{m}$. These data provide accurate and well-constrained photometric redshifts down to $m \approx 29-30\,\mathrm{mag}$. We subsequently confirmed $N = 96$ potential members of the overdensity using JWST slitless spectroscopy over $\lambda = 3.9-5.0\ \mu\mathrm{m}$ through a targeted line search for $\mathrm{H} \alpha$ around the best-fit photometric redshift. We verified that $N = 53$ galaxies reside in the field at $z = 5.2-5.5$ while $N = 43$ galaxies reside in an overdensity at $z = 5.4$ around $\sim 10-12$ times that of a random volume. Stellar populations for these galaxies were inferred from the photometry and used to construct the star-forming main sequence, where protocluster members appeared more massive and exhibited earlier star formation (and thus older stellar populations) when compared to their field galaxy counterparts. We estimate the total halo mass of this large-scale structure to be $13.0 \lesssim \mathrm{log}_{10} \left( M_{\mathrm{halo}}/M_{\odot} \right) \lesssim 13.5$ using an empirical stellar mass to halo mass relation, although this is likely an underestimate as a result of incompleteness. Our discovery demonstrates the power of JWST at constraining dark matter halo assembly and galaxy formation at very early cosmic times.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present JWST NIRCam 9-band near-infrared imaging of the luminous $z=10.6$ galaxy GN-z11 from the JWST Advanced Deep Extragalactic Survey (JADES) of the GOODS-N field. We find a spectral energy distribution (SED) entirely consistent with the expected form of a high-redshift galaxy: a clear blue continuum from 1.5 to 4 microns with a complete dropout in F115W. The core of GN-z11 is extremely compact in JWST imaging. We analyze the image with a two-component model, using a point source and a S\'{e}rsic profile that fits to a half-light radius of 200 pc and an index $n=0.9$. We find a low-surface brightness haze about $0.4''$ to the northeast of the galaxy, which is most likely a foreground object but might be a more extended component of GN-z11. At a spectroscopic redshift of 10.60 (Bunker et al. 2023), the comparison of the NIRCam F410M and F444W images spans the Balmer jump. From population synthesis modeling, here assuming no light from an active galactic nucleus, we reproduce the SED of GN-z11, finding a stellar mass of $\sim$$10^{9}~M_{\odot}$, a star-formation rate of $\sim$$20~M_{\odot}~\mathrm{yr}^{-1}$ and a young stellar age of $\sim$$20~\mathrm{Myr}$. As massive galaxies at high redshift are likely to be highly clustered, we search for faint neighbors of GN-z11, finding 9 galaxies out to $\sim$5 comoving Mpc transverse with photometric redshifts consistent with $z=10.6$, and a 10$^{\rm th}$ more tentative dropout only $3''$ away.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Finding and characterising the first galaxies that illuminated the early
Universe at cosmic dawn is pivotal to understand the physical conditions and
the processes that led to the formation of the first stars. In the first few
months of operations, imaging from the James Webb Space Telescope (JWST) have
been used to identify tens of candidates of galaxies at redshift (z) greater
than 10, less than 450 million years after the Big Bang. However, none of these
candidates has yet been confirmed spectroscopically, leaving open the
possibility that they are actually low-redshift interlopers. Here we present
spectroscopic confirmation and analysis of four galaxies unambiguously detected
at redshift 10.3