We present an analysis of the ultraviolet luminosity function (UV LF) and star formation rate density of distant galaxies (\(7.5 < z < 13.5\)) in the `blank' fields of the Prime Extragalactic Areas ...for Reionization Science (PEARLS) survey combined with Early Release Science (ERS) data from the CEERS, GLASS, NGDEEP surveys/fields and the first data release of JADES. We use strict quality cuts on EAZY photometric redshifts to obtain a reliable selection and characterisation of high-redshift (\(z>6.5\)) galaxies from a consistently processed set of deep, near-infrared imaging. Within an area of 180 arcmin\(^{2}\), we identify 1046 candidate galaxies at redshifts \(z>6.5\) and we use this sample to study the ultraviolet luminosity function (UV LF) in four redshift bins between \(7.5<z<13.5\). The measured number density of galaxies at \(z=8\) and \(z=9\) match those of past observations undertaken by the {\em Hubble Space Telescope} (HST). Our \(z=10.5\) measurements lie between early JWST results and past HST results, indicating cosmic variance may be the cause of previous high density measurements. However, number densities of UV luminous galaxies at \(z=12.5\) are high compared to predictions from simulations. When examining the star formation rate density of galaxies at this time period, our observations are still largely consistent with a constant star formation efficiency, are slightly lower than previous early estimations using JWST and support galaxy driven reionization at \(z\leq8\).
We present a detailed analysis of a large sample of spectroscopically
confirmed ultra-massive quiescent galaxies
(${\rm{log}}(M_{\ast}/M_{\odot})\sim11.5$) at $z\gtrsim2$. This sample
comprises 15 ...galaxies selected in the COSMOS and UDS fields by their bright
K-band magnitudes and followed up with VLT/X-shooter spectroscopy and HST/WFC3
$H_{F160W}$ imaging. These observations allow us to unambiguously confirm their
redshifts ascertain their quiescent nature and stellar ages, and to reliably
assess their internal kinematics and effective radii. We find that these
galaxies are compact, consistent with the high mass end of the mass-size
relation for quiescent galaxies at $z=2$. Moreover, the distribution of the
measured stellar velocity dispersions of the sample is consistent with the most
massive local early-type galaxies from the MASSIVE Survey showing that
evolution in these galaxies, is dominated by changes in size. The HST images
reveal, as surprisingly high, that $40\ \%$ of the sample have tidal features
suggestive of mergers and companions in close proximity, including three
galaxies experiencing ongoing major mergers. The absence of velocity dispersion
evolution from $z=2$ to $0$, coupled with a doubling of the stellar mass, with
a factor of four size increase and the observed disturbed stellar morphologies
support dry minor mergers as the primary drivers of the evolution of the
massive quiescent galaxies over the last 10 billion years.
Thesis (Ph. D.)--University of Wisconsin--Madison, 2001.
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JWST spectroscopy has revolutionized our understanding of galaxies in the early universe. Covering wavelengths up to \(5.3\,{\rm \mu m}\), NIRSpec can detect rest-frame optical emission lines ...H\(\alpha\) out to \(z = 7\) and O III to \(z = 9.5\). Observing these lines in more distant galaxies requires longer wavelength spectroscopy with MIRI. Here we present MIRI MRS IFU observations of the lensed galaxy merger MACS0647\(-\)JD at \(z = 10.165\). With exposure times of 4.2 hours in each of two bands, we detect H\(\alpha\) at \(9\sigma\), O III\(\,\lambda5008\) at \(11\sigma\), and O III\(\,\lambda4960\) at \(3\sigma\). Combined with previously reported NIRSpec spectroscopy that yields seven emission lines including the auroral line O III\(\,\lambda4363\), we present the first direct metallicity measurement of a \(z > 10\) galaxy: \(12+{\rm log(O/H)}= 7.79\pm0.09\), or \(0.13^{+0.02}_{-0.03}\,Z_{\odot}\). This is similar to galaxies at \(z \sim 4 - 9\) with direct metallicity measurements, though higher than expected given the high specific star formation rate \({\rm log(sSFR / yr^{-1})} = -7.4 \pm 0.3\). We further constrain the ionization parameter \({\rm log}(U)\) = \(-1.9 \pm 0.1\), ionizing photon production efficiency \({\rm log}(\xi_{\rm ion})\) = \(25.3\pm0.1\), and star formation rate \(5.0\pm0.6\,M_{\odot}/{\rm yr}\) within the past \(10\,{\rm Myr}\). These observations demonstrate the combined power of JWST NIRSpec and MIRI for studying galaxies in the first \(500\) million years.
Merging is potentially the dominate process in galaxy formation, yet there is still debate about its history over cosmic time. To address this we classify major mergers and measure galaxy merger ...rates up to z \(\sim\) 3 in all five CANDELS fields (UDS, EGS, GOODS-S, GOODS-N, COSMOS) using deep learning convolutional neural networks (CNNs) trained with simulated galaxies from the IllustrisTNG cosmological simulation. The deep learning architecture used is objectively selected by a Bayesian Optmization process over the range of possible hyperparameters. We show that our model can achieve 90% accuracy when classifying mergers from the simulation, and has the additional feature of separating mergers before the infall of stellar masses from post mergers. We compare our machine learning classifications on CANDELS galaxies and compare with visual merger classifications from Kartaltepe et al. (2015), and show that they are broadly consistent. We finish by demonstrating that our model is capable of measuring galaxy merger rates, \(\mathcal{R}\), that are consistent with results found for CANDELS galaxies using close pairs statistics, with \(\mathcal{R}(z) = 0.02 \pm 0.004 \times (1 +z) ^ {2.76 \pm 0.21}\). This is the first general agreement between major mergers measured using pairs and structure at z < 3.
We present a new parametric lens model for the G165.7+67.0 galaxy cluster, which was discovered with \(Planck\) through its bright submillimeter flux, originating from a pair of extraordinary dusty ...star-forming galaxies (DSFGs) at \(z\approx 2.2\). Using JWST and interferometric mm/radio observations, we characterize the intrinsic physical properties of the DSFGs, which are separated by only \(\sim 1^{\prime\prime}\) (8 kpc) and a velocity difference \(\Delta V \lesssim 600~{\rm km}~{\rm s}^{-1}\) in the source plane, and thus likely undergoing a major merger. Boasting intrinsic star formation rates \({\rm SFR}_{\rm IR} = 320 \pm 70\) and \(400 \pm 80~ M_\odot~{\rm yr}^{-1}\), stellar masses \({\rm log}M_\star/M_\odot = 10.2 \pm 0.1\) and \(10.3 \pm 0.1\), and dust attenuations \(A_V = 1.5 \pm 0.3\) and \(1.2 \pm 0.3\), they are remarkably similar objects. We perform spatially-resolved pixel-by-pixel SED fitting using rest-frame near-UV to near-IR imaging from JWST/NIRCam for both galaxies, resolving some stellar structures down to 100 pc scales. Based on their resolved specific SFRs and \(UVJ\) colors, both DSFGs are experiencing significant galaxy-scale star formation events. If they are indeed interacting gravitationally, this strong starburst could be the hallmark of gas that has been disrupted by an initial close passage. In contrast, the host galaxy of the recently discovered triply-imaged SN H0pe has a much lower SFR than the DSFGs, and we present evidence for the onset of inside-out quenching and large column densities of dust even in regions of low specific SFR. Based on the intrinsic SFRs of the DSFGs inferred from UV through FIR SED modeling, this pair of objects alone is predicted to yield an observable \(1.1 \pm 0.2~{\rm CCSNe~yr}^{-1}\), making this cluster field ripe for continued monitoring.
Observing massive galaxies at various redshifts is one of the most straightforward and direct approaches towards understanding galaxy formation. There is now largely a consensus that the massive ...galaxy (M_* > 10^11 M_0) population is fully formed by z~1, based on mass and luminosity functions. However, we argue that the latest data can only rule out number and mass density evolution of a factor of > 2-3 at z < 1.5. We furthermore show that the star formation history of M_* > 10^11 M_0 galaxies reveals that 40+/-5% of galaxies with M_* > 10^11 M_0 at z~1 are undergoing star formation that effectively doubles their stellar mass between z = 0.4 - 1.4. These massive galaxies also undergo 0.9^+0.7_-0.5 major mergers during this same time period.
We present JWST/NIRSpec prism spectroscopy of MACS0647-JD, the triply-lensed \(z \sim 11\) candidate discovered in HST imaging and spatially resolved by JWST imaging into two components A and B. ...Spectroscopy of component A yields a spectroscopic redshift \(z=10.17\) based on 7 detected emission lines: CIII \(\lambda\lambda\)1907,1909, OII \(\lambda\)3727, NeIII \(\lambda\)3869, NeIII \(\lambda\)3968, H\(\delta\) \(\lambda\)4101, H\(\gamma\) \(\lambda\)4340, and OIII \(\lambda\)4363. These are the second-most distant detections of these emission lines to date, in a galaxy observed just 460 million years after the Big Bang. Based on observed and extrapolated line flux ratios we derive a gas-phase metallicity \(Z =\) log(O/H) = \(7.5 - 8.0\), or \((0.06 - 0.2)\) \(Z_\odot\), ionization parameter log(\(U\)) \(\sim -1.9\pm0.2\), and an ionizing photon production efficiency \({\rm log}(\xi_{\rm ion})=25.2\pm0.2\,\)erg\(^{-1}\) Hz. The spectrum has a softened Lyman-\(\alpha\) break, evidence for a strong Ly\(\alpha\) damping wing, suggesting that MACS0647-JD was unable to ionize its surroundings beyond its immediate vicinity (\(R_{\text{HII}} \ll 1\) pMpc). The Ly\(\alpha\) damping wing also suppresses the F150W photometry, explaining the slightly overestimated photometric redshift \(z = 10.6 \pm 0.3\). MACS0647-JD has a stellar mass log(\(M/M_\odot\)) = \(8.1 \pm 0.3\), including \(\sim\) 6\(\times 10^7 M_\odot\) in component A, most of which formed recently (within \(\sim\) 20 Myr) with a star formation rate \(2\pm1 M_\odot\) / yr, all within an effective radius \(70\pm24\,\)pc. The smaller component B (\(r \sim 20\)) pc is likely older (\(\sim\)100 Myr) with more dust (\(A_V \sim 0.1\) mag), as found previously. Spectroscopy of a fainter companion galaxy C separated by a distance of \about\ 3\(\,\)kpc reveals a Lyman break consistent with \(z = 10.17\). MACS0647-JD is likely the most distant galaxy merger known.
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