分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: This report is the result of a joint discussion between the Rubin and Euclid scientific communities. The work presented in this report was focused on designing and recommending an initial set of Derived Data products (DDPs) that could realize the science goals enabled by joint processing. All interested Rubin and Euclid data rights holders were invited to contribute via an online discussion forum and a series of virtual meetings. Strong interest in enhancing science with joint DDPs emerged from across a wide range of astrophysical domains: Solar System, the Galaxy, the Local Volume, from the nearby to the primaeval Universe, and cosmology.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report on the discovery of two low-luminosity, broad-line AGN at $z>5$ identified using JWST NIRSpec spectroscopy from the CEERS Survey. We detect broad H$\alpha$ emission from both sources, with FWHM of $2038\pm286$ and $1807\pm207$ km s$^{-1}$, resulting in black hole (BH) masses that are 1-2 dex below that of existing samples of luminous quasars at $z>5$. The first source, CEERS 1670 at $z=5.242$, is 2-3 dex fainter than known quasars at similar redshifts and was previously identified as a candidate low-luminosity AGN based on its rest-frame optical SED. We measure a BH mass of $M_{\rm BH}=1.3\pm0.4\times 10^{7}~M_{\odot}$, confirming that this AGN is powered by the least-massive BH known in the universe at the end of cosmic reionization. The second source, CEERS 3210 at $z=5.624$, is inferred to be a heavily obscured, broad-line AGN caught in a transition phase between a dust-obscured starburst and an unobscured quasar. We estimate its BH mass to be $M_{\rm BH}\simeq 0.9-4.7 \times 10^{7}~M_{\odot}$, depending on the level of dust obscuration assumed. We derive host stellar masses, $M_\star$, allowing us to place constraints on the BH-galaxy mass relationship in the lowest mass range yet probed in the early universe. The $M_{\rm BH}/M_\star$ ratio for CEERS 1670, in particular, is consistent with or higher than the empirical relationship seen in massive galaxies at $z=0$. We examine the emission-line ratios of both sources and find that their location on the BPT and OHNO diagrams is consistent with model predictions for low-metallicity AGN with $Z/Z_\odot \simeq 0.2-0.4$. The spectroscopic identification of low-luminosity, broad-line AGN at $z>5$ with $M_{\rm BH}\simeq 10^{7}~M_{\odot}$ demonstrates the capability of JWST to push BH masses closer to the range predicted for the BH seed population and provides a unique opportunity to study the early stages of BH-galaxy assembly.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy formation from z~0.5 to z>10 using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 sq. arcmin, to search for candidate galaxies at z>9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multi-band photometry across seven NIRCam broad and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z~9-16. These objects are compact with a median half-light radius of ~0.5 kpc. We present an early estimate of the z~11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M_UV ~ -20 appears to evolve very little from z~9 to z~11. We also find that the abundance (surface density [arcmin^-2]) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z>10 star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star-formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific samples of ultra-high-redshift galaxies with which to further explore these conclusions.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Lyman Break Galaxy (LBG) candidates at z>10 are rapidly being identified in JWST/NIRCam observations. Due to the (redshifted) break produced by neutral hydrogen absorption of rest-frame UV photons, these sources are expected to drop out in the bluer filters while being well detected in redder filters. However, here we show that dust-enshrouded star-forming galaxies at lower redshifts (z10 LBGs, representing potential contaminants in LBG candidate samples. First, we analyze CEERS-DSFG-1, a NIRCam dropout undetected in the F115W and F150W filters but detected at longer wavelengths. Combining the JWST data with (sub)millimeter constraints, including deep NOEMA interferometric observations, we show that this source is a dusty star-forming galaxy (DSFG) at z~5.1. We also present a tentative 2.6sigma SCUBA-2 detection at 850um around a recently identified z~16 LBG candidate in the same field and show that, if the emission is real and associated with this candidate, the available photometry is consistent with a z~5 dusty galaxy with strong nebular emission lines despite its blue near-IR colors. Further observations on this candidate are imperative to mitigate the low confidence of this tentative submillimeter emission and its positional uncertainty. Our analysis shows that robust (sub)millimeter detections of NIRCam dropout galaxies likely imply z=4-6 redshift solutions, where the observed near-IR break would be the result of a strong rest-frame optical Balmer break combined with high dust attenuation and strong nebular line emission, rather than the rest-frame UV Lyman break. This provides evidence that DSFGs may contaminate searches for ultra high-redshift LBG candidates from JWST observations.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a comprehensive analysis of the evolution of the morphological and structural properties of a large sample of galaxies at z=3-9 using early JWST CEERS NIRCam observations. Our sample consists of 850 galaxies at z>3 detected in both CANDELS HST imaging and JWST CEERS NIRCam images to enable a comparison of HST and JWST morphologies. Our team conducted a set of visual classifications, with each galaxy in the sample classified by three different individuals. We also measure quantitative morphologies using the publicly available codes across all seven NIRCam filters. Using these measurements, we present the fraction of galaxies of each morphological type as a function of redshift. Overall, we find that galaxies at z>3 have a wide diversity of morphologies. Galaxies with disks make up a total of 60\% of galaxies at z=3 and this fraction drops to ~30% at z=6-9, while galaxies with spheroids make up ~30-40% across the whole redshift range and pure spheroids with no evidence for disks or irregular features make up ~20%. The fraction of galaxies with irregular features is roughly constant at all redshifts (~40-50%), while those that are purely irregular increases from ~12% to ~20% at z>4.5. We note that these are apparent fractions as many selection effects impact the visibility of morphological features at high redshift. The distributions of S\'ersic index, size, and axis ratios show significant differences between the morphological groups. Spheroid Only galaxies have a higher S\'ersic index, smaller size, and higher axis ratio than Disk/Irregular galaxies. Across all redshifts, smaller spheroid and disk galaxies tend to be rounder. Overall, these trends suggest that galaxies with established disks and spheroids exist across the full redshift range of this study and further work with large samples at higher redshift is needed to quantify when these features first formed.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present results from the Cosmic Evolution Early Release Survey (CEERS) on
the stellar-population parameters for 28 galaxies with redshifts $4
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present the mid-IR (MIR) morphologies for 70 star-forming galaxies (SFGs) at $0.210^{9}~M_\odot}$ using JWST MIRI observations from the Cosmic Evolution Early Release Science survey (CEERS). The MIRI bands span the MIR (7.7--21 $\mu$m), enabling us to measure the effective radii ($R_{\mathrm{eff}}$) and S\'{e}rsic indexes of these SFGs at rest-frame 6.2 and 7.7 $\mu$m, which contains strong emission from Polycyclic aromatic hydrocarbon (PAH) features, a well-established tracer of star formation in galaxies. We compare the PAH-band morphologies to those in rest-frame Near-UV (NUV) using HST ACS/F435W or ACS/F606W and optical/near-IR using HST WFC3/F160W imaging from UVCANDELS and CANDELS, where the NUV-band and F160W trace the profile of (unobscured) massive stars and the stellar continuum, respectively. The $R_{\mathrm{eff}}$ of galaxies in the PAH-band are slightly smaller ($\sim$10) than those in F160W for more massive galaxies with $\mathrm{M_*\gtrsim10^{9.5}~M_\odot}$ at $z\leq1.2$ and with $\mathrm{M_*\gtrsim10^{10}~M_\odot}$ at $z\geq1.2$, but the PAH-band and F160W have a similar fractions of light within 1 kpc. In contrast, the $R_{\rm{eff}}$ of galaxies in the NUV-band are larger, with lower fractions of light within 1 kpc compared to the F160W for galaxies at $z\leq1.2$. Using the MIRI data to estimate the surface density of the IR-based SFR, we find the correlation between the IR-based SFR surface density and stellar mass has a steeper slope than that of the UV-based surface density and stellar mass, suggesting galaxies with higher stellar masses having increasing amounts of obscured fraction of star formation in their inner regions. This paper demonstrates how the high-angular resolution data from JWST/MIRI can reveal new information about the morphology of obscured-star formation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present CEERS JWST/NIRCam imaging of a massive galaxy group at z=1.85, to explore the early JWST view on massive group formation in the distant Universe. The group contains >16 members (including 6 spectros. confirmations) down to log10(Mstar/Msun)=8.5, including the Brightest Group Galaxy (BGG) in the process of actively assembling at this redshift. The BGG is comprised of multiple merging components extending ~3.6" (30kpc) across the sky. The BGG contributes 69% of the group's total galactic stellar mass, with one of the merging components containing 76% of the total mass of the BGG and a SFR>1810Msun/yr. Most importantly, we detect intra-halo light (IHL) in several HST and JWST/NIRCam bands, allowing us to construct a state-of-the-art rest-frame UV-NIR Spectral Energy Distribution of the IHL for the first time at this high redshift. This allows stellar population characterisation of both the IHL and member galaxies, as well as the morphology distribution of group galaxies vs. their star-formation activity when coupled with Herschel data. We create a stacked image of the IHL, giving us a sensitivity to extended emission of 28.5 mag/arcsec2 at rest-frame 1um. We find that the IHL is extremely dust poor (Av~0), containing an evolved stellar population of log10(t50/yr)=8.8, corresponding to a formation epoch for 50% of the stellar material 0.63Gyr before z=1.85. There is no evidence of ongoing star-formation in the IHL. The IHL in this group at z=1.85 contributes ~10% of the total stellar mass, comparable with what is observed in local clusters. This suggests that the evolution of the IHL fraction is more self-similar with redshift than predicted by some models, challenging our understanding of IHL formation during the assembly of high-redshift clusters. JWST is unveiling a new side of group formation at this redshift, which will evolve into Virgo-like structures in the local Universe.