Fig 2 - uploaded by Rolf Jansen
Content may be subject to copyright.
— Examples of the sub-classifications assigned to the merging galaxies in our sample. Each of the the B-filter VATT images measures 3.0 ′ × 2.4 ′ . Top left: NGC4644 (the galaxy on the right) is in strong interaction with its neighbor NGC4644B (PGC42725), and is classified as a pre-merger (pM). Top right: NGC3445 appears to be accreting a smaller companion, PGC32784, and is classified as a minor merger (mM). Bottom left: UGC10279 represents a major merger event (M) between two galaxies of similar mass, Holmberg 734A and B. Bottom right: in NGC2623 the properties of the galaxies that merged are no longer exactly discernible, so it is classified as a merger remnant (MR, early stage).
Source publication
We present a quantitative analysis of the morphologies for 199 nearby
galaxies as parameterized with measurements of the concentration, asymmetry,
and clumpiness (CAS) parameters at wavelengths from 0.15-0.85 micrometers. We
find that these CAS parameters depend on both galaxy type and the wavelength of
observation. As such, we use them to obtain a...
Similar publications
Lenticular galaxies (S0s) are more likely to host antitruncated (Type-III)
stellar discs than galaxies of later Hubble types. Major mergers are popularly
considered too violent mechanisms to form these breaks. We have investigated
whether major mergers can result into S0-like remnants with realistic
antitruncated stellar discs or not. We have analy...
Citations
... The impact of varying rest-frame wavelengths on these morphological indicators is significant and has been extensively studied (e.g., Taylor-Mager et al. 2007;Baes et al. 2020;Yao et al. 2023). Lotz et al. (2004) observed that longer rest-frame wavelengths reveal more extended structures, which they attribute to the predominant presence of older stellar populations. ...
The measurements of morphological indicators of galaxies are often influenced by a series of observational effects. In this study, we utilize a sample of 832 TNG50 simulated galaxies with log( M * / M ⊙ )> 9 at 0.5 < z < 3 to investigate the differences in nonparametric morphological indicators ( C , A , Gini , M 20 , A O , and D O ) derived from noise-free and high-resolution TNG50 images and mock images simulated to have the same observational conditions as JWST/NIRCam. We quantify the relationship between intrinsic and observed values of the morphological indicators and accordingly apply this calibration to 4733 galaxies in the same stellar mass and redshift ranges observed in JWST CEERS and JADES surveys. We find a significant evolution of morphological indicators with rest-frame wavelength ( λ rf ) at λ rf < 1 μ m, while essentially no obvious variations occur at λ rf > 1 μ m. The morphological indicators of star-forming galaxies (SFGs) and quiescent galaxies (QGs) are significantly different. The morphologies of QGs exhibit a higher sensitivity to rest-frame wavelength than SFGs. After analyzing the evolution of morphological indicators in the rest-frame V band (0.5–0.7 μ m) and rest-frame J band (1.1–1.4 μ m), we find that the morphologies of QGs evolve substantially with both redshift and stellar mass. For SFGs, the C , Gini , and M 20 show a rapid evolution with stellar mass at log( M * / M ⊙ ) ≥ 10.5, while the A O , D O , and A evolve with both redshift and stellar mass. Our comparison shows that TNG50 simulations effectively reproduce the morphological indicators we measured from JWST observations when the impact of dust attenuation is considered.
... GALFIT in a least-squaresfitting algorithm that finds the best-fitting model by minimizing the reduced chi-squared statistic ( 2 ). We choose filters that closely match the rest-frame optical wavelength of the sources to minimize the morphological -correction effect (Taylor-Mager et al. 2007). Extreme cases are filtered out based on the criteria that the half-light radius should be within 0.01 < (pixels) < 100 and the fitted Sersic index lies within the range 0.05 < < 10. ...
In this paper we describe our search for galaxy protocluster candidates at $4.5< z < 10$ and explore the environmental and physical properties of their member galaxies identified through JWST wide-field surveys within the CEERS, JADES, and PEARLS NEP-TDF fields. Combining with HST data, we identify 2948 robust $z>4.5$ candidates within an area of 185.4 arcmin$^2$. We determine nearest neighbour statistics and galaxy environments. We find that high-$z$ galaxies in overdense environments exhibit higher star formation activity compared to those in underdense regions. Galaxies in dense environments have a slightly increased SFR at a given mass compared with galaxies in the lower density environments. At the high mass end we also find a gradual flattening of the $M_{\star}$-SFR slope. We find that galaxies in high-density regions often have redder UV slopes than those in low-density regions, suggesting more dust extinction, weaker Lyman-alpha emission and / or a higher damped Lyman-alpha absorption. We also find that the mass-size relation remains consistent and statistically similar across all environments. Furthermore, we quantitatively assess the probability of a galaxy belonging to a protocluster candidate. In total, we identified 26 overdensities at $z=5-7$ and estimate their dark matter halo masses. We find that all protocluster candidates could evolve into clusters with $M_{\rm halo} > 10^{14}M_{\odot}$ at $z = 0$, thereby supporting the theoretical and simulation predictions of cluster formation. Notably, this marks an early search for protocluster candidates in JWST wide field based on photometric data, providing valuable candidates to study cosmic structure formation at the early stages.
... After that, the galaxies with the lowest asymmetries are dwarf and massive ETGs, while those with the highest asymmetries are late-type systems (consistent with what is seen in other work, e.g. Bershady et al. 2000 ;Taylor-Mager et al. 2007 ). ...
We use a complete, unbiased sample of 257 dwarf (108 M⊙ < M⋆ < 109.5 M⊙) galaxies at z < 0.08, to study the morphological mix of the dwarf population in low-density environments. Visual inspection of extremely deep optical images and their unsharp-masked counterparts reveals three principal dwarf morphological classes. 43 and 45 per cent of dwarfs exhibit the traditional ‘early-type’ (elliptical/S0) and ‘late-type’ (spiral) morphologies respectively. However, 10 per cent populate a ‘featureless’ class, that lacks both the central light concentration seen in early-types and any spiral structure - this class is missing in the massive-galaxy regime. 14, 27, 19 per cent of early-type, late-type and featureless dwarfs respectively show evidence for interactions, which drive around 20 per cent of the overall star formation activity in the dwarf population. Compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions, are significantly less concentrated and share similar rest-frame colours as dwarf late-types. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes. The lack of large groups or clusters in COSMOS at z < 0.08, and the fact that our dwarf morphological classes show similar local density, suggests that featureless dwarfs in low-density environments are created via internal baryonic feedback, rather than by environmental processes. Finally, while interacting dwarfs can be identified using the asymmetry parameter, it is challenging to cleanly separate early and late-type dwarfs using traditional morphological parameters, such as ‘CAS’, M20 and the Gini coefficient (unlike in the massive-galaxy regime).
... As the appearance of a galaxy changes with the redshift as a result of cosmological surface brightness dimming and image resolution (e.g., Giavalisco et al. 1996;Hibbard & Vacca 1997;Conselice 2003;Barden et al. 2008;Vika et al. 2013;Davari et al. 2016), we design realistic mock experiments to quantify the contribution of these effects to the final error budget. Lastly, galaxy morphology and structure depend on wavelength, as a consequence of internal variations in stellar population and dust attenuation (Windhorst et al. 2002;Taylor-Mager et al. 2007;Kelvin et al. 2012;Häußler et al. 2013;Vika et al. 2013). It is important to take this into consideration when measuring the structural parameters of galaxies across different bands, as is the case for the seven-band images of CEERS. ...
We analyze 347 galaxies at redshift 4 < z < 9.5 using JWST observations from the Cosmic Evolution Early Release Science (CEERS) program by simultaneously fitting a two-dimensional parametric model to the seven-filter Near Infrared Camera images to measure the overall structural parameters and quantify the global properties of the galaxies in the rest-frame optical band. Particular attention is devoted to deriving robust uncertainties that include, among other factors, the influence of cosmological surface brightness dimming and resolution effects. Using the global Sérsic index ( n < 1.5) and observed axial ratio ( q < 0.6) as a guide, we place a conservative lower limit of ∼45% on the incidence of galactic disks. Galaxies follow a relation between the rest-frame optical luminosity and effective radius in the redshift range 4 < z < 9.5, as well as separately over the intervals 4 < z < 5 and 5 ≤ z < 9.5, with a very similar slope but a marginally lower zero-point in the higher-redshift bin ( R e = 0.69 ± 0.05 kpc) compared to the lower-redshift bin ( R e = 0.91 ± 0.04 kpc). Within the limitations of the current sample size, we find no significant redshift evolution of n or R e at these early epochs.
... As seen in equation 1 , GALFIT requires a data image from which the galaxy surface brightness is measured, f data ( x , y ) and a sigma image, σ ( x , y ), gi ving the relati ve error at each position within the image, which are then used to calculate the model image, We run GALFIT for all available filters, but only report results here for the filters that best match the rest-frame optical wavelength of the source. This minimizes, or even eliminates, the effect of morphological k -correction, as the qualitative and quantitative structure of galaxies changes as a function of wa velength (Taylor - Mager et al. 2007 ), which can result in significant structural changes between rest-frame UV and rest-frame optical images. This also enables us to limit the CMOD effect (Papaderos, Ö stlin & Breda 2023 ), by probing rest-frame optical wavelengths, which is possible up to z ∼ 8 with JWST . ...
... The changes in a galaxy's appearance and size as a function of wav elength can pro vide man y clues to the formation history and stellar populations of modern galaxies (e.g. Windhorst et al. 2002 ;Taylor-Mager et al. 2007 ;Mager et al. 2018 ;Suess et al. 2022 ). An example of this is that if a galaxy forms inside-out, with the older stellar populations in the centre of the galaxy, then most likely these systems would appear larger at shorter wavelengths, and vice versa if formation occurred via outside-in. ...
We present the results of a size and structural analysis of 1395 galaxies at 0.5 ≤ z ≲ 8 with stellar masses log (M*/M⊙)> 9.5 within the JWST Public CEERS field that overlaps with the HST CANDELS EGS observations. We use GALFIT to fit single Sérsic models to the rest-frame optical profile of our galaxies, which is a mass-selected sample complete to our redshift and mass limit. Our primary result is that at fixed rest-frame wavelength and stellar mass, galaxies get progressively smaller, evolving as ∼(1 + z)−0.71 ± 0.19 up to z ∼ 8. We discover that the vast majority of massive galaxies at high redshifts have low Sérsic indices, thus do not contain steep, concentrated light profiles. Additionally, we explore the evolution of the size-stellar mass relationship, finding a correlation such that more massive systems are larger up to z ∼ 3. This relationship breaks down at z > 3, where we find that galaxies are of similar sizes, regardless of their star formation rates and Sérsic index, varying little with mass. We show that galaxies are more compact at redder wavelengths, independent of sSFR or stellar mass up to z ∼ 3. We demonstrate the size evolution of galaxies continues up to z ∼ 8, showing that the process or causes for this evolution is active at early times. We discuss these results in terms of ideas behind galaxy formation and evolution at early epochs, such as their importance in tracing processes driving size evolution, including minor mergers and AGN activity.
... We run GALFIT for all available filters, but only report results here for the filters that best match the rest-frame optical wavelength of the source. This minimises, or even eliminates, the effect of morphological k-correction, as the qualitative and quantitative structure of galaxies changes as a function of wavelength (Taylor- Mager et al. 2007), which can result in significant structural changes between rest-frame UV and rest-frame optical images. The band selected at a given redshift is shown in Figure 1. ...
... The changes in a galaxy's appearance and size as a function of wavelength can provide many clues to the formation history and stellar populations of modern galaxies (e.g., Windhorst et al. 2002;Taylor-Mager et al. 2007;Mager et al. 2018;Suess et al. 2022). An example of this is that if a galaxy forms inside-out, with the older stellar populations in the centre of the galaxy, then most likely these systems would appear larger at shorter wavelengths, and vice-versa if formation occurred via outside-in. ...
We present the results of a size and structural analysis of 1395 galaxies at 0.5 ≤ ≲ 8 with stellar masses log (* / ⊙)> 9.5 within the JWST Public CEERS field that overlaps with the HST CANDELS EGS observations. We use GALFIT to fit single Sérsic models to the rest-frame optical profile of our galaxies, which is a mass-selected sample complete to our redshift and mass limit. Our primary result is that at fixed rest-frame wavelength and stellar mass, galaxies get progressively smaller, evolving as ∼ (1 +) −0.71±0.19 up to ∼ 8. We discover that the vast majority of massive galaxies at high redshifts have low Sérsic indices, thus do not contain steep, concentrated light profiles. Additionally, we explore the evolution of the size-stellar mass relationship, finding a correlation such that more massive systems are larger up to ∼ 3. This relationship breaks down at > 3, where we find that galaxies are of similar sizes, regardless of their star formation rates and Sérsic index, varying little with mass. We show that galaxies are more compact at redder wavelengths, independent of sSFR or stellar mass up to ∼ 3. We demonstrate the size evolution of galaxies continues up to ∼ 8, showing that the process or causes for this evolution is active at early times. We discuss these results in terms of ideas behind galaxy formation and evolution at early epochs, such as their importance in tracing processes driving size evolution, including minor mergers and AGN activity.
... We run GALFIT for all available filters, but only report results here for the filters that best match the rest-frame optical wavelength of the source. This minimises, or even eliminates, the effect of morphological k-correction, as the qualitative and quantitative structure of galaxies changes as a function of wavelength (Taylor- Mager et al. 2007), which can result in significant structural changes between rest-frame UV and rest-frame optical images. The band selected at a given redshift is shown in Figure 1. ...
... The changes in a galaxy's appearance and size as a function of wavelength can provide many clues to the formation history and stellar populations of modern galaxies (e.g., Windhorst et al. 2002;Taylor-Mager et al. 2007;Mager et al. 2018;Suess et al. 2022). An example of this is that if a galaxy forms inside-out, with the older stellar populations in the centre of the galaxy, then most likely these systems would appear larger at shorter wavelengths, and vice-versa if formation occurred via outside-in. ...
We present the results of a size and structural analysis of 1395 galaxies at $0.5 \leq z \lesssim 8$ with stellar masses $\log \left(M_* / M_{\odot}\right)$ $>$ 9.5 within the JWST Public CEERS field that overlaps with the HST CANDELS EGS observations. We use GALFIT to fit single S\'ersic models to the rest-frame optical profile of our galaxies, which is a mass-selected sample complete to our redshift and mass limit. Our primary result is that at fixed rest-frame wavelength and stellar mass, galaxies get progressively smaller, evolving as $\sim (1+z)^{-0.71\pm0.19}$ up to $z \sim 8$. We discover that the vast majority of massive galaxies at high redshifts have low S\'ersic indices, thus do not contain steep, concentrated light profiles. Additionally, we explore the evolution of the size-stellar mass relationship, finding a correlation such that more massive systems are larger up to $z \sim 3$. This relationship breaks down at $z > 3$, where we find that galaxies are of similar sizes, regardless of their star formation rates and S\'ersic index, varying little with mass. We show that galaxies are more compact at redder wavelengths, independent of sSFR or stellar mass up to $z \sim 3$. We demonstrate the size evolution of galaxies continues up to $z \sim 8$, showing that the process or causes for this evolution is active at early times. We discuss these results in terms of ideas behind galaxy formation and evolution at early epochs, such as their importance in tracing processes driving size evolution, including minor mergers and AGN activity.
... We run GALFIT for all available filters but only report results for the filters that best match the rest-frame optical wavelength of the source. This minimizes the effect of morphological k-correction, as the qualitative and quantitative structure of galaxies changes as a function of wavelength (Taylor-Mager et al. 2007), which can result in significant structural changes between rest-frame UV and rest-frame optical images. In this case, all results reported are in the F444W band. ...
We present an early analysis on the search for high-redshift galaxies using the deepest public JWST imaging to date, the NGDEEP field. These data consist of six-band NIRCam imaging on the Hubble Ultra Deep Field Parallel 2 (HUDF-Par2), covering a total area of 6.3 arcmin ² . Based on our initial reduction of the first half of this survey, we reach 5 σ depths up to mag = 29.5–29.9 between 1 and 5 μ m. Such depths present an unprecedented opportunity to begin exploring the very early universe with JWST. As such, we find high-redshift galaxies by examining the spectral energy distribution of all F444W detections and present 16 new z > 8.5 galaxies identified using two different photometric redshift codes: LePhare and EAZY combined with other significance criteria. The highest-redshift object in our sample is at z = 15.6 − 0.3 + 0.4 , which has a blue β = − 3.02 − 0.46 + 0.42 and a very low inferred stellar mass of M * = 10 7.4 M ⊙ . We also discover a series of faint, low-mass dwarf galaxies with M * < 10 8.5 M ⊙ at z ∼ 9 that have blue colors, flat surface brightness profiles, and small sizes <1 kpc. Comparing to previous work in the HUDF-Par2, we find 21 6 < z < 9 candidates including two z = 8 major mergers. One of these merger candidates has an additional two z = 8 sources within 30″, indicating that it may form part of an overdensity. We also compare our results to theory, finding no significant disagreement with a few cold-dark-matter-based models. The discovery of these objects demonstrates the critical need for deeper, or similar depth but wider-area, JWST surveys to explore the early universe.
... Rest-frame ultraviolet (UV) images of galaxies trace their SFR over a timescale of ∼100 Myr associated with the continuum from massive, short-lived O-and B-type stars (Calzetti 2013). Thus, clumps can be detected in highresolution imaging of field or lensed galaxies in rest-frame UV or optical (e.g., Conselice et al. 2004;Elmegreen & Elmegreen 2005;Elmegreen et al. 2007;Taylor-Mager et al. 2007;Elmegreen et al. 2009;Förster Schreiber et al. 2011;Guo et al. 2012;Murata et al. 2014;Tadaki et al. 2014;Guo et al. 2015;Shibuya et al. 2016;Soto et al. 2017;Cava et al. 2018;Dessauges-Zavadsky & Adamo 2018;Guo et al. 2018;Mager et al. 2018;Messa et al. 2019;Vanzella et al. 2021;Meštrić et al. 2022;Sok et al. 2022). There are, however, other studies that have identified clumps in Hα emission-line maps of galaxies (e.g., Genzel et al. 2008Genzel et al. , 2011Livermore et al. 2012;Mieda et al. 2016;Fisher et al. 2017;Zanella et al. 2019;Sharma et al. 2021) or in CO observations of lensed galaxies (e.g., Jones et al. 2010;Swinbank et al. 2010). ...
High-resolution imaging of galaxies in rest-frame UV has revealed the existence of giant star-forming clumps prevalent in high-redshift galaxies. Studying these substructures provides important information about their formation and evolution and informs theoretical galaxy evolution models. We present a new method to identify clumps in galaxies’ high-resolution rest-frame UV images. Using imaging data from CANDELS and UVCANDELS, we identify star-forming clumps in an HST/F160W ≤ 25 AB mag sample of 6767 galaxies at 0.5 ≤ z ≤ 3 in four fields, GOODS-N, GOODS-S, EGS, and COSMOS. We use a low-passband filter in Fourier space to reconstruct the background image of a galaxy and detect small-scale features (clumps) on the background-subtracted image. Clumpy galaxies are defined as those having at least one off-center clump that contributes a minimum of 10% of the galaxy’s total rest-frame UV flux. We measure the fraction of clumpy galaxies ( f clumpy ) as a function of stellar mass, redshift, and galaxy environment. Our results indicate that f clumpy increases with redshift, reaching ∼65% at z ∼ 1.5. We also find that f clumpy in low-mass galaxies ( 9.5 ≤ log ( M * / M ⊙ ) ≤ 10 ) is 10% higher compared to that of their high-mass counterparts ( log ( M * / M ⊙ ) > 10.5 ). Moreover, we find no evidence of significant environmental dependence of f clumpy for galaxies at the redshift range of this study. Our results suggest that the fragmentation of gas clouds under violent disk instability remains the primary driving mechanism for clump formation, and incidents common in dense environments, such as mergers, are not the dominant processes.
... This leads to large uncertainties in photometric redshifts. The other difficulty is the morphological K-correction (Taylor-Mager et al. 2007). Neither the stellar population nor the extinction has to be uniform, and therefore galaxies can show different morphologies in different bands. ...
Four ultraluminous infrared galaxies (ULIRGs) observed with JWST/NIRcam in the Cosmos Evolution Early Release Science program offer an unbiased preview of the z ∼ 2 ULIRG population. The objects were originally selected at 24 μ m and have strong polycyclic aromatic hydrocarbon emission features observed with Spitzer/Infrared Spectrometer. The four objects have similar stellar masses of ∼10 ¹¹ M ⊙ but otherwise are quite diverse. One is an isolated disk galaxy, but it has an active nucleus as shown by X-ray observations and by a bright point-source nucleus. Two others are merging pairs with mass ratios of 6–7:1. One has active nuclei in both components, while the other has only one active nucleus: the one in the less-massive neighbor, not the ULIRG. The fourth object is clumpy and irregular and is probably a merger, but there is no sign of an active nucleus. The intrinsic spectral energy distributions for the four active galactic nuclei in these systems are typical of type-2 QSOs. This study is consistent with the idea that even if internal processes can produce large luminosities at z ∼ 2, galaxy merging may still be necessary for the most luminous objects. The diversity of these four initial examples suggests that large samples will be needed to understand the z ∼ 2 ULIRG population.
