arXiv subjects

Anton M. Koekemoer

Publications and source records attributed to Anton M. Koekemoer.

At least 343 records · Page 19Linked to original sources

arXiv2022

Morphology & Environment's Role on the Star Formation Rate -- Stellar Mass Relation in COSMOS from 0 < z < 3.5

We investigate the relationship between environment, morphology, and the star formation rate -- stellar mass relation derived from a sample of star-forming galaxies (commonly referred to as the `star formation main sequence') in the COSMOS field from 0 < z < 3.5. We constructed and fit the FUV--FIR SEDs of our stellar mass-selected sample of 111,537 galaxies with stellar and dust emission models using the public packages MAGPHYS and SED3FIT. From the best fit parameter estimates, we construct the star formation rate -- stellar mass relation as a function of redshift, local environment, NUVrJ color diagnostics, and morphology. We find that the shape of the main sequence derived from our color-color and sSFR-selected star forming galaxy population, including the turnover at high stellar mass, does not exhibit an environmental dependence at any redshift from 0 < z < 3.5. We investigate the role of morphology in the high mass end of the SFMS to determine whether bulge growth is driving the high mass turnover. We find that star-forming galaxies experience this turnover independent of bulge-to-total ratio, strengthening the case that the turnover is due to the disk component's specific star formation rate evolving with stellar mass rather than bulge growth.

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arXiv2022

ALMA Lensing Cluster Survey: $HST$ and $Spitzer$ Photometry of 33 Lensed Fields Built with CHArGE

We present a set of multi-wavelength mosaics and photometric catalogs in the ALMA lensing cluster survey (ALCS) fields. The catalogs were built by reprocessing of archival data from the CHArGE compilation, taken by the $\textit{Hubble Space Telescope}$ ($\textit{HST}$) in the RELICS, CLASH and Hubble Frontier Fields. Additionally we have reconstructed the $\textit{Spitzer}$ IRAC 3.6 and 4.5 $μ$m mosaics, by utilising all the available archival IRSA/SHA exposures. To alleviate the effect of blending in such a crowded region, we have modelled the $\textit{Spitzer}$ photometry by convolving the $\textit{HST}$ detection image with the $\textit{Spitzer}$ PSF using the novel $\texttt{golfir}$ software. The final catalogs contain 218,000 sources, covering a combined area of 690 arcmin$^2$. These catalogs will serve as an important tool in aiding the search of the sub-mm galaxies in future ALMA surveys, as well as follow ups of the $\textit{HST}$ dark - IRAC sources. Coupled with the available $\textit{HST}$ photometry the addition of the 3.6 and 4.5 $μ$m bands will allow us to place a better constraint on photometric redshifts and stellar masses of these objects, thus giving us an opportunity to identify high-redshift candidates for spectroscopic follow ups and answer the important questions regarding the epoch of reionization and formation of first galaxies.

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arXiv2022

Emission Line Galaxies in the SHARDS Hubble Frontier Fields II: Limits on Lyman-Continuum Escape Fractions of Lensed Emission Line Galaxies at Redshifts 2 < z < 3.5

We present an investigation on escape fractions of UV photons from a unique sample of lensed low-mass emission line selected galaxies at z < 3.5 found in the SHARDS Hubble Frontier Fields medium-band survey. We have used this deep imaging survey to locate 42 relatively low-mass galaxies, down to $log(M_{*}/M_{\odot}) = 7$, between redshifts 2.4 < z < 3.5 which are candidate line emitters. Using deep multi-band Hubble UVIS imaging we investigate the flux of escaping ionizing photons from these systems, obtaining 1$σ$ upper limits of $f^{rel}_{esc}$ ~7% for individual galaxies, and < 2% for stacked data. We measure potential escaping Lyman-continuum flux for two low-mass line emitters with values at $f^{\rm rel}_{\rm esc} = 0.032^{+0.081}_{-0.009}$ and $f^{\rm rel}_{\rm esc} = 0.021^{+0.101}_{-0.006}$, both detected at the ~3.2$σ$ level. A detailed analysis of possible contamination reveals a < 0.1% probability that these detections result from line-of-sight contamination. The relatively low Lyman-continuum escape fraction limit, and the low fraction of systems detected, is an indication that low-mass line emitting galaxies may not be as important a source of reionization as hoped if these are analogs of reionization sources. We also investigate the structures of our galaxy sample, finding no evidence for a correlation of escape fraction with asymmetric structure.

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arXiv2022

A Transient "Changing-look'' Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data

We report the discovery of a new ``changing-look'' active galactic nucleus (CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z=0.2603, identified through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V). Optical photometry taken during 2020--2021 shows a dramatic dimming of $Δ$g${\approx}$1 mag, followed by a rapid recovery on a timescale of several months, with the ${\lesssim}$2 month period of rebrightening captured in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the fastest CLAGN transitions observed to date. Archival observations suggest that the object experienced a much more gradual dimming over the period of 2011--2013. Our spectroscopy shows that the photometric changes were accompanied by dramatic variations in the quasar-like continuum and broad-line emission. The excellent agreement between the pre- and postdip photometric and spectroscopic appearances of the source, as well as the fact that the dimmest spectra can be reproduced by applying a single extinction law to the brighter spectral states, favor a variable line-of-sight obscuration as the driver of the observed transitions. Such an interpretation faces several theoretical challenges, and thus an alternative accretion-driven scenario cannot be excluded. The recent events observed in this quasar highlight the importance of spectroscopic monitoring of large active galactic nucleus samples on weeks-to-months timescales, which the SDSS-V is designed to achieve.

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arXiv2022

CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results

We present the data release and data reduction process for the Epoch 1 NIRCam observations for the Cosmic Evolution Early Release Science Survey (CEERS). These data consist of NIRCam imaging in six broadband filters (F115W, F150W, F200W, F277W, F356W and F444W) and one medium band filter (F410M) over four pointings, obtained in parallel with primary CEERS MIRI observations (Yang et al. in prep). We reduced the NIRCam imaging with the JWST Calibration Pipeline, with custom modifications and reduction steps designed to address additional features and challenges with the data. Here we provide a detailed description of each step in our reduction and a discussion of future expected improvements. Our reduction process includes corrections for known pre-launch issues such as 1/f noise, as well as in-flight issues including snowballs, wisps, and astrometric alignment. Many of our custom reduction processes were first developed with pre-launch simulated NIRCam imaging over the full 10 CEERS NIRCam pointings. We present a description of the creation and reduction of this simulated dataset in the Appendix. We provide mosaics of the real images in a public release, as well as our reduction scripts with detailed explanations to allow users to reproduce our final data products. These represent one of the first official public datasets released from the Directors Discretionary Early Release Science (DD-ERS) program.

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arXiv2022

Constraints on Cosmological Parameters with a Sample of Type Ia Supernovae from JWST

We investigate the potential of using a sample of very high-redshift ($2\lesssim z \lesssim6$) (VHZ) Type Ia supernovae (SNe~Ia) attainable by the James Webb Space Telescope (JWST) on constraining cosmological parameters. At such high redshifts, the age of the universe is young enough that the VHZ SNIa sample comprises the very first SNe~Ia of the universe, with progenitors among the very first generation of low mass stars that the universe has made. We show that the VHZ SNe~Ia can be used to disentangle systematic effects due to the luminosity distance evolution with redshifts intrinsic to SNIa standardization. Assuming that the systematic evolution can be described by a linear or logarithmic formula, we found that the coefficients of this dependence can be determined accurately and decoupled from cosmological models. Systematic evolution as large as 0.15 mag and 0.45 mag out to $z=5$ can be robustly separated from popular cosmological models for the linear and logarithmic evolution, respectively. The VHZ SNe~Ia will lay the foundation for quantifying the systematic redshift evolution of SNIa luminosity distance scales. When combined with SNIa surveys at comparatively lower redshifts, the VHZ SNe~Ia allow for a precise measurement of the history of the expansion of the universe from $z\sim 0$ to the epoch approaching reionization.

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arXiv2022

COSMOS2020: Identification of High-z Protocluster Candidates in COSMOS

We conduct a systematic search for protocluster candidates at $z \geq 6$ in the COSMOS field using the recently released COSMOS2020 source catalog. We select galaxies using a number of selection criteria to obtain a sample of galaxies that have a high probability of being inside a given redshift bin. We then apply overdensity analysis to the bins using two density estimators, a Weighted Adaptive Kernel Estimator and a Weighted Voronoi Tessellation Estimator. We have found 15 significant ($>4σ$) candidate galaxy overdensities across the redshift range $6\le z\le7.7$. The majority of the galaxies appear to be on the galaxy main sequence at their respective epochs. We use multiple stellar-mass-to-halo-mass conversion methods to obtain a range of dark matter halo mass estimates for the overdensities in the range of $\sim10^{11-13}\,M_{\rm \odot}$, at the respective redshifts of the overdensities. The number and the masses of the halos associated with our protocluster candidates are consistent with what is expected from the area of a COSMOS-like survey in a standard $Λ$CDM cosmology. Through comparison with simulation, we expect that all the overdensities at $z\simeq6$ will evolve into a Virgo-/Coma-like clusters at present (i.e., with masses $\sim 10^{14}-10^{15}\,M_{\rm \odot}$). Compared to other overdensities identified at $z \geq 6$ via narrow-band selection techniques, the overdensities presented appear to have $\sim10\times$ higher stellar masses and star-formation rates. We compare the evolution in the total star-formation rate and stellar mass content of the protocluster candidates across the redshift range $6\le z\le7.7$ and find agreement with the total average star-formation rate from simulations.

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arXiv2022

SKYSURF-3: Testing Crowded Object Catalogs in the Hubble eXtreme Deep Field Mosaics to Study Sample Incompleteness from an Extragalactic Background Light Perspective

Extragalactic Background Light (EBL) studies have revealed a significant discrepancy between direct measurements -- via instruments measuring "bare" sky from which Zodiacal and Galactic light models are subtracted -- and measurements of the Integrated Galaxy Light (IGL). This discrepancy could lie in either method, whether it be an incomplete Zodiacal model or missed faint galaxies in the IGL calculations. It has been proposed that the discrepancy is due to deep galaxy surveys, such as those with the Hubble Space Telescope (HST), missing up to half of the faint galaxies with $24 \le m_{AB} \le 29$ mag. We address this possibility by simulating higher number densities of galaxies, and so assess incompleteness due to object overlap, with three replications of the Hubble UltraDeep Field (HUDF). SourceExtractor is used to compare the recovered counts and photometry to the original HUDF, allowing us to assess how many galaxies may have been missed due to confusion, i.e., due to blending with neighboring faint galaxies. This exercise reveals that, while up to 50% of faint galaxies with $28 \le m_{AB} \le 29$ mag were missed or blended with neighboring objects in certain filters, not enough were missed to account for the EBL discrepancy alone in any of the replications.

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arXiv2022

JWST's PEARLS: a new lens model for ACT-CL J0102$-$4915, "EL Gordo'', and the first red supergiant star at cosmological distances discovered by JWST

The first JWST data on the massive colliding cluster El Gordo confirm 23 known families of multiply lensed images and identify 8 new members of these families. Based on these families, which have been confirmed spectroscopically by MUSE, we derived an initial lens model. This model guided the identification of 37 additional families of multiply lensed galaxies, among which 28 are entirely new systems, and 9 were previously known. The initial lens model determined geometric redshifts for the 37 new systems. The geometric redshifts agree reasonably well with spectroscopic or photometric redshifts when those are available. The geometric redshifts enable two additional models that include all 60 families of multiply lensed galaxies spanning a redshift range $2 0.8$ and has an estimated virial mass close the maximum mass allowed by standard cosmological models. The JWST images also reveal the presence of small-mass perturbers that produce small lensing distortions. The smallest of these is consistent with being a dwarf galaxy at $z=0.87$ and has an estimated mass of $3.8\times10^9$~\Msol, making it the smallest substructure found at $z>0.5$. The JWST images also show several candidate caustic-crossing events. One of them is detected at high significance at the expected position of the critical curve and is likely a red supergiant star at $z=2.1878$. This would be the first red supergiant found at cosmological distances. The cluster lensing should magnify background objects at $z>6$, making more of them visible than in blank fields of similar size, but there appears to be a deficiency of such objects.

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arXiv2022

Investigating the Effect of Galaxy Interactions on Star Formation at 0.5<z<3.0

Observations and simulations of interacting galaxies and mergers in the local universe have shown that interactions can significantly enhance the star formation rates (SFR) and fueling of Active Galactic Nuclei (AGN). However, at higher redshift, some simulations suggest that the level of star formation enhancement induced by interactions is lower due to the higher gas fractions and already increased SFRs in these galaxies. To test this, we measure the SFR enhancement in a total of 2351 (1327) massive ($M_*>10^{10}M_\odot$) major ($1<M_1/M_2<4$) spectroscopic galaxy pairs at 0.5<z<3.0 with $ΔV <5000$ km s$^{-1}$ (1000 km s$^{-1}$) and projected separation <150 kpc selected from the extensive spectroscopic coverage in the COSMOS and CANDELS fields. We find that the highest level of SFR enhancement is a factor of 1.23$^{+0.08}_{-0.09}$ in the closest projected separation bin (<25 kpc) relative to a stellar mass-, redshift-, and environment-matched control sample of isolated galaxies. We find that the level of SFR enhancement is a factor of $\sim1.5$ higher at 0.5<z<1 than at 1<z<3 in the closest projected separation bin. Among a sample of visually identified mergers, we find an enhancement of a factor of 1.86$^{+0.29}_{-0.18}$ for coalesced systems. For this visually identified sample, we see a clear trend of increased SFR enhancement with decreasing projected separation (2.40$^{+0.62}_{-0.37}$ vs.\ 1.58$^{+0.29}_{-0.20}$ for 0.5<z<1.6 and 1.6<z<3.0, respectively). The SFR enhancement seen in our interactions and mergers are all lower than the level seen in local samples at the same separation, suggesting that the level of interaction-induced star formation evolves significantly over this time period.

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arXiv2022

Lack of influence of the environment in the earliest stages of massive galaxy formation

We investigate how the environment affects the assembly history of massive galaxies. For that purpose, we make use of SHARDS and HST spectro-photometric data, whose depth, spectral resolution, and wavelength coverage allow to perform a detailed analysis of the stellar emission as well as obtaining unprecedentedly accurate photometric redshifts. This expedites a sufficiently accurate estimate of the local environment and a robust derivation of the star formation histories of a complete sample of 332 massive galaxies ($\mathrm{>10^{10}M_{\odot}}$) at redshift $1\leq z \leq 1.5$ in the GOODS-N field. We find that massive galaxies in this redshift range avoid the lowest density environments. Moreover, we observed that the oldest galaxies in our sample with with mass-weighted formation redshift $\mathrm{\overline{z}_{M-w} \geq 2.5}$, avoid the highest density regions, preferring intermediate environments. Younger galaxies, including those with active star formation, tend to live in denser environments ($Σ= \mathrm{5.0_{1.1}^{24.8}\times 10^{10}M_{\odot}Mpc^{-2}}$). This behavior could be expected if those massive galaxies starting their formation first would merge with neighbors and sweep their environment earlier. On the other hand, galaxies formed more recently ($\overline{z}_{M-w} < 2.5$) are accreted into large scale structures at later times and we are observing them before sweeping their environment or, alternatively, they are less likely to affect their environment. However, given that both number and mass surface densities of neighbor galaxies is relatively low for the oldest galaxies, our results reveal a very weak correlation between environment and the first formation stages of the earliest massive galaxies.

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arXiv2022

The JWST Early Release Observations

The James Webb Space Telescope (JWST) Early Release Observations (EROs) is a set of public outreach products created to mark the end of commissioning and the beginning of science operations for JWST. Colloquially known as the "Webb First Images and Spectra", these products were intended to demonstrate to the worldwide public that JWST is ready for science, and is capable of producing spectacular results. The package was released on July 12, 2022, and included images and spectra of the galaxy cluster SMACS~J0723.3-7327 and distant lensed galaxies, the interacting galaxy group Stephan's Quintet, NGC 3324 in the Carina star-forming complex, the Southern Ring planetary nebula NGC 3132, and the transiting hot Jupiter WASP 96b. This paper describes the ERO technical design, observations, and scientific processing of data underlying the colorful outreach products.

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arXiv2022

A Long Time Ago in a Galaxy Far, Far Away: A Candidate z ~ 12 Galaxy in Early JWST CEERS Imaging

We report the discovery of a candidate galaxy with a photo-z of z~12 in the first epoch of the JWST Cosmic Evolution Early Release Science (CEERS) Survey. Following conservative selection criteria we identify a source with a robust z_phot = 11.8^+0.3_-0.2 (1-sigma uncertainty) with m_F200W=27.3, and >7-sigma detections in five filters. The source is not detected at lambda < 1.4um in deep imaging from both HST and JWST, and has faint ~3-sigma detections in JWST F150W and HST F160W, which signal a Ly-alpha break near the red edge of both filters, implying z~12. This object (Maisie's Galaxy) exhibits F115W-F200W > 1.9 mag (2-sigma lower limit) with a blue continuum slope, resulting in 99.6% of the photo-z PDF favoring z > 11. All data quality images show no artifacts at the candidate's position, and independent analyses consistently find a strong preference for z > 11. Its colors are inconsistent with Galactic stars, and it is resolved (r_h = 340 +/- 14 pc). Maisie's Galaxy has log M*/Msol ~ 8.5 and is highly star-forming (log sSFR ~ -8.2 yr^-1), with a blue rest-UV color (beta ~ -2.5) indicating little dust though not extremely low metallicity. While the presence of this source is in tension with most predictions, it agrees with empirical extrapolations assuming UV luminosity functions which smoothly decline with increasing redshift. Should followup spectroscopy validate this redshift, our Universe was already aglow with galaxies less than 400 Myr after the Big Bang.

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arXiv2022

A Machine Learning Approach to Predict Missing Flux Densities in Multi-band Galaxy Surveys

We present a new method based on information theory to find the optimal number of bands required to measure the physical properties of galaxies with a desired accuracy. As a proof of concept, using the recently updated COSMOS catalog (COSMOS2020), we identify the most relevant wavebands for measuring the physical properties of galaxies in a Hawaii Two-0 (H20)- and UVISTA-like survey for a sample of $i<25$ AB mag galaxies. We find that with available $i$-band fluxes, $r$, $u$, IRAC/$ch2$ and $z$ bands provide most of the information regarding the redshift with importance decreasing from $r$-band to $z$-band. We also find that for the same sample, IRAC/$ch2$, $Y$, $r$ and $u$ bands are the most relevant bands in stellar mass measurements with decreasing order of importance. Investigating the inter-correlation between the bands, we train a model to predict UVISTA observations in near-IR from H20-like observations. We find that magnitudes in $YJH$ bands can be simulated/predicted with an accuracy of $1σ$ mag scatter $\lesssim 0.2$ for galaxies brighter than 24 AB mag in near-IR bands. One should note that these conclusions depend on the selection criteria of the sample. For any new sample of galaxies with a different selection, these results should be remeasured. Our results suggest that in the presence of a limited number of bands, a machine learning model trained over the population of observed galaxies with extensive spectral coverage outperforms template-fitting. Such a machine learning model maximally comprises the information acquired over available extensive surveys and breaks degeneracies in the parameter space of template-fitting inevitable in the presence of a few bands.

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arXiv2022

Deep Large Binocular Camera r-band Observations of the GOODS-N Field

We obtained 838 Sloan r-band images (~28 hrs) of the GOODS-North field with the Large Binocular Camera (LBC) on the Large Binocular Telescope in order to study the presence of extended, low surface brightness features in galaxies and investigate the trade-off between image depth and resolution. The individual images were sorted by effective seeing, which allowed for optimal resolution and optimal depth mosaics to be created with all images with seeing FWHM < 0.9" and FWHM < 2.0", respectively. Examining bright galaxies and their substructure as well as accurately deblending overlapping objects requires the optimal resolution mosaic, while detecting the faintest objects possible (to a limiting magnitude of $m_{AB}$ ~ 29.2 mag) requires the optimal depth mosaic. The better surface brightness sensitivity resulting from the larger LBC pixels, compared to those of extant WFC3/UVIS and ACS/WFC cameras aboard the Hubble Space Telescope (HST) allows for unambiguous detection of both diffuse flux and very faint tidal tails. We created azimuthally-averaged radial surface brightness profiles for the 360 brightest galaxies in the mosaics. We find little difference in the majority of the light profiles from the optimal resolution and optimal depth mosaics. However, $\lesssim$ 15% of the profiles show excess flux in the galaxy outskirts down to surface brightness levels of $μ^{AB}_{r} $ $\simeq$ 31 mag arcsec $^{-2}$. This is relevant to Extragalactic Background Light (EBL) studies as diffuse light in the outer regions of galaxies are thought to be a major contribution to the EBL. While some additional diffuse light exists in the optimal depth profiles compared to the shallower, optimal resolution profiles, we find that diffuse light in galaxy outskirts is a minor contribution to the EBL overall in the r-band.

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arXiv2022

CEERS Key Paper III: The Resolved Host Properties of AGN at 3 < z < 5 with JWST

We report on the host properties of five X-ray luminous Active Galactic Nuclei (AGN) identified at $3 < z < 5$ in the first epoch of imaging from the Cosmic Evolution Early Release Science Survey (CEERS). Each galaxy has been imaged with the \textit{James Webb Space Telescope} (\jwst) Near-Infrared Camera (NIRCam), which provides spatially resolved, rest-frame optical morphologies at these redshifts. We also derive stellar masses and star formation rates for each host galaxy by fitting its spectral energy distribution using a combination of galaxy and AGN templates. The AGN hosts have an average stellar mass of ${\rm log}(M_{*}/{\rm M_{\odot}} )= 11.0$, making them among the most massive galaxies detected at this redshift range in the current CEERS pointings, even after accounting for nuclear light from the AGN. We find that three of the AGN hosts have spheroidal morphologies, one is a bulge-dominated disk and one host is dominated by point-like emission. None are found to show strong morphological disturbances that might indicate a recent interaction or merger event. Notably, all four of the resolved hosts have rest-frame optical colors consistent with a quenched or post-starburst stellar population. The presence of AGN in passively evolving galaxies at $z>3$ is significant because a rapid feedback mechanism is required in most semi-analytic models and cosmological simulations to explain the growing population of massive quiescent galaxies observed at these redshifts. Our findings are in general agreement with this picture and show that AGN can continue to inject energy into these systems after their star formation is curtailed, possibly helping to maintain their quiescent state.

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arXiv2022

First Peek with JWST/NIRCam Wide-Field Slitless Spectroscopy: Serendipitous Discovery of a Strong [O III]/H$α$ Emitter at $z=6.11$

We report the serendipitous discovery of an [O III] $λλ$4959/5007 and H$α$ line emitter in the Epoch of Reionization (EoR) with the JWST commissioning data taken in the NIRCam wide field slitless spectroscopy (WFSS) mode. Located $\sim$55" away from the flux calibrator P330-E, this galaxy exhibits bright [O III] $λλ$4959/5007 and H$α$ lines detected at 3.7, 9.9 and 5.7$σ$, respectively, with a spectroscopic redshift of $z=6.112\pm0.001$. The total H$β$+[O III] equivalent width is 664$\pm$98 Å (454$\pm$78 Å from the [O III] $λ$5007 line). This provides direct spectroscopic evidence for the presence of strong rest-frame optical lines (H$β$+[O III] and H$α$) in EoR galaxies as inferred previously from the analyses of Spitzer/IRAC spectral energy distributions. Two spatial and velocity components are identified in this source, possibly indicating that this system is undergoing a major merger, which might have triggered the ongoing starburst with strong nebular emission lines over a timescale of $\sim$2 Myr as our SED modeling suggests. The tentative detection of He II $λ$4686 line ($1.9σ$), if real, may indicate the existence of very young and metal-poor star-forming regions with a hard UV radiation field. Finally, this discovery demonstrates the power and readiness of the JWST/NIRCam WFSS mode, and marks the beginning of a new era for extragalactic astronomy, in which EoR galaxies can be routinely discovered via blind slitless spectroscopy through the detection of rest-frame optical emission lines.

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arXiv2022

Identifying Galaxy Mergers in Simulated CEERS NIRCam Images using Random Forests

Identifying merging galaxies is an important - but difficult - step in galaxy evolution studies. We present random forest classifications of galaxy mergers from simulated JWST images based on various standard morphological parameters. We describe (a) constructing the simulated images from IllustrisTNG and the Santa Cruz SAM, and modifying them to mimic future CEERS observations as well as nearly noiseless observations, (b) measuring morphological parameters from these images, and (c) constructing and training the random forests using the merger history information for the simulated galaxies available from IllustrisTNG. The random forests correctly classify $\sim60\%$ of non-merging and merging galaxies across $0.5 < z < 4.0$. Rest-frame asymmetry parameters appear more important for lower redshift merger classifications, while rest-frame bulge and clump parameters appear more important for higher redshift classifications. Adjusting the classification probability threshold does not improve the performance of the forests. Finally, the shape and slope of the resulting merger fraction and merger rate derived from the random forest classifications match with theoretical Illustris predictions, but are underestimated by a factor of $\sim 0.5$.

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