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The dramatic first images with James Webb Space Telescope (JWST) demonstrated its power to provide unprecedented spatial detail for galaxies in the high-redshift universe. Here, we leverage the resolution and depth of the JWST Cosmic Evolution Early Release Science Survey (CEERS) data in the Extended Groth Strip (EGS) to perform pixel-level morphological classifications of galaxies in JWST F150W imaging using the Morpheus deep learning framework for astronomical image analysis. By cross-referencing with existing photometric redshift catalogs from the Hubble Space Telescope (HST) CANDELS survey, we show that JWST images indicate the emergence of disk morphologies before z~2 and with candidates appearing as early as z~5. By modeling the light profile of each object and accounting for the JWST point-spread function, we find the high-redshift disk candidates have exponential surface brightness profiles with an average Sersic (1968) index n=1.04 and >90% displaying "disky" profiles (n<2). Comparing with prior Morpheus classifications in CANDELS we find that a plurality of JWST disk galaxy candidates were previously classified as compact based on the shallower HST imagery, indicating that the improved optical quality and depth of the JWST helps to reveal disk morphologies that were hiding in the noise. We discuss the implications of these early disk candidates on theories for cosmological disk galaxy formation., Comment: Submitted to AAS Journals

We present spatially-resolved two-dimensional maps and radial trends of the stellar populations and kinematics for a sample of six compact elliptical galaxies (cE) using spectroscopy from the Keck Cosmic Web Imager (KCWI). We recover their star formation histories, finding that all except one of our cEs are old and metal rich, with both age and metallicity decreasing toward their outer radii. We also use the integrated values within one effective radius to study different scaling relations. Comparing our cEs with others from the literature and from simulations we reveal the formation channel that these galaxies might have followed. All our cEs are fast rotators, with relatively high rotation values given their low ellipticites. In general, the properties of our cEs are very similar to those seen in the cores of more massive galaxies, and in particular, to massive compact galaxies. Five out of our six cEs are the result of stripping a more massive (compact or extended) galaxy, and only one cE is compatible with having been formed intrinsically as the low-mass, compact object that we see today. These results further confirm that cEs are a mixed-bag of galaxies that can be formed following different formation channels, reporting for the first time an evolutionary link within the realm of compact galaxies (at all stellar masses)., Comment: Aceepted for publication in MNRAS. 19 pages, 13 figures

The dominant physical formation mechanism(s) for ultra-diffuse galaxies (UDGs) is still poorly understood. Here, we combine new, deep imaging from the Jeanne Rich Telescope with deep integral field spectroscopy from the Keck II telescope to investigate the formation of UDG1137+16 (dw1137+16). Our new analyses confirm both its environmental association with the low density UGC 6594 group, along with its large size of 3.3 kpc and status as a UDG. The new imaging reveals two distinct stellar components for UDG1137+16, indicating that a central stellar body is surrounded by an outer stellar envelope undergoing tidal interaction. Both the components have approximately similar stellar masses. From our integral field spectroscopy we measure a stellar velocity dispersion within the half-light radius (15 $\pm$ 4 $\mathrm{km\ s^{-1}}$) and find that UDG1137+16 is similar to some other UDGs in that it is likely dark matter dominated. Incorporating literature measurements, we also examine the current state of UDG observational kinematics. Placing these data on the central stellar velocity dispersion -- stellar mass relation, we suggest there is little evidence for UDG1137+16 being created through a strong tidal interaction. Finally, we investigate the constraining power current dynamical mass estimates (from stellar and globular cluster velocity dispersions) have on the total halo mass of UDGs. As most are measured within the half-light radius, they are unable to accurately constrain UDG total halo masses., Comment: Published in MNRAS: 15 pages, 8 figures, 1 appendix; Minor update to match published version

We present spatially resolved two-dimensional maps and radial trends of the stellar populations and kinematics for a sample of six compact elliptical galaxies (cE) using spectroscopy from the Keck Cosmic Web Imager (KCWI). We recover their star formation histories, finding that all except one of our cEs are old and metal rich, with both age and metallicity decreasing toward their outer radii. We also use the integrated values within one effective radius to study different scaling relations. Comparing our cEs with others from the literature and from simulations we reveal the formation channel that these galaxies might have followed. All our cEs are fast rotators, with relatively high rotation values given their low ellipticites. In general, the properties of our cEs are very similar to those seen in the cores of more massive galaxies, and in particular, to massive compact galaxies. Five out of our six cEs are the result of stripping a more massive (compact or extended) galaxy, and only one cE is compatible with having been formed intrinsically as the low-mass compact object that we see today. These results further confirm that cEs are a mixed-bag of galaxies that can be formed following different formation channels, reporting for the first time an evolutionary link within the realm of compact galaxies (at all stellar masses).

The dominant physical formation mechanism(s) for ultradiffuse galaxies (UDGs) is still poorly understood. Here, we combine new, deep imaging from the Jeanne Rich Telescope with deep integral field spectroscopy from the Keck II telescope to investigate the formation of UDG1137+16 (dw1137+16). Our new analyses confirm both its environmental association with the low density UGC 6594 group, along with its large size of 3.3 kpc and status as a UDG. The new imaging reveals two distinct stellar components for UDG1137+16, indicating that a central stellar body is surrounded by an outer stellar envelope undergoing tidal interaction. Both the components have approximately similar stellar masses. From our integral field spectroscopy, we measure a stellar velocity dispersion within the half-light radius (15 ± 4 km s−1) and find that UDG1137+16 is similar to some other UDGs in that it is likely dark matter dominated. Incorporating literature measurements, we also examine the current state of UDG observational kinematics. Placing these data on the central stellar velocity dispersion–stellar mass relation, we suggest there is little evidence for UDG1137+16 being created through a strong tidal interaction. Finally, we investigate the constraining power current dynamical mass estimates (from stellar and globular cluster velocity dispersions) have on the total halo mass of UDGs. As most are measured within the half-light radius, they are unable to accurately constrain UDG total halo masses. © 2021 The Author(s).

We present new spectra obtained using Keck/KCWI and perform kinematics and stellar population analyses of the shell galaxy NGC 474, from both the galaxy centre and a region from the outer shell. We show that both regions have similarly extended star formation histories although with different stellar population properties. The central region of NGC 474 is dominated by intermediate-aged stars (8.3 \pm 0.3 Gyr) with subsolar metallicity ([Z/H]= -0.24 \pm 0.07 dex) while the observed shell region, which hosts a substantial population of younger stars, has a mean luminosity-weighted age of 4.0 \pm 0.5 Gyr with solar metallicities ([Z/H]=-0.03 \pm 0.09 dex). Our results are consistent with a scenario in which NGC 474 experienced a major to intermediate merger with a log\((M_*/M_\odot)\sim10 \) mass satellite galaxy at least \sim 2 Gyr ago which produced its shell system. This work shows that the direct spectroscopic study of low-surface brightness stellar features, such as shells, is now feasible and opens up a new window to understanding galaxy formation and evolution., Comment: Accepted for publication in MNRAS, 6 pages, 5 figures

We present a catalogue of low surface brightness (LSB) galaxies in the Coma cluster obtained from deep Subaru/Suprime-Cam V and R-band imaging data within a region of $\sim$4 deg$^2$. We increase the number of LSB galaxies presented in Yagi et al. (2016) by a factor of $\sim$3 and report the discovery of 29 new ultra-diffuse galaxies (UDGs). We compile the largest sample of ultra-diffuse galaxies with colours and structural parameters in the Coma cluster. While most UDGs lie along the red-sequence relation of the colour-magnitude diagram, $\sim$5per cent are outside (bluer or redder) the red-sequence region of Coma cluster galaxies. Our analyses show that there is no special distinction in the basic photometric parameters between UDGs and other LSB galaxies. We investigate the clustercentric colour distribution and find a remarkable transition at a projected radius of $\sim$0.6 Mpc. Within this cluster core region, LSB galaxies are, on average, redder than co-spatial higher surface brightness galaxies, highlighting how vulnerable LSB galaxies are to the physical processes at play in the dense central region of the cluster. The position of the transition radius agrees with expectations from recent cosmological simulation of massive galaxy clusters within which ancient infalls are predicted to dominate the LSB galaxy population., Comment: Accepted for publication in MNRAS. The complete version of Table 2 is available online as supplementary material

Ultra diffuse galaxies (UDGs) reveal extreme properties. Here we compile the largest study to date of 85 globular cluster (GC) systems around UDGs in the Coma cluster, using new deep ground-based imaging of the known UDGs and existing imaging from the Hubble Space Telescope of their GC systems. We find that the richness of GC systems in UDGs generally exceeds that found in normal dwarf galaxies of the same stellar mass. These GC-rich UDGs imply halos more massive than expected from the standard stellar mass-halo mass relation. The presence of such overly massive halos presents a significant challenge to the latest simulations of UDGs in cluster environments. In some exceptional cases, the mass in the GC system is a significant fraction of the stellar content of the host galaxy. We find that rich GC systems tend to be hosted in UDGs of lower luminosity, smaller size and fainter surface brightness. Similar trends are seen for normal dwarf galaxies in the Coma cluster. A toy model is presented in which the GC-rich UDGs are assumed to be `failed' galaxies within massive halos that have largely old, metal-poor, alpha-element enhanced stellar populations. On the other hand, GC-poor UDGs are more akin to normal, low surface brightness dwarfs that occupy less massive dark matter halos. Additional data on the stellar populations of UDGs with GC systems will help to further refine and test this simplistic model., Comment: 11 pages, 11 figures, accepted for publication in MNRAS

The ultra-diffuse galaxy in the NGC 5846 group (NGC 5846_UDG1) was shown to have a large number of globular cluster (GC) candidates from deep imaging as part of the VEGAS survey. Recently, Muller et al. published a velocity dispersion, based on a dozen of its GCs. Within their quoted uncertainties, the resulting dynamical mass allowed for either a dark matter free or a dark matter dominated galaxy. Here we present spectra from KCWI which reconfirms membership of the NGC 5846 group and reveals a stellar velocity dispersion for UDG1 of $\sigma_{GC}$ = 17 $\pm$ 2 km/s. Our dynamical mass, with a reduced uncertainty, indicates a very high contribution of dark matter within the effective radius. We also derive an enclosed mass from the locations and motions of the GCs using the Tracer Mass Estimator, finding a similar mass inferred from our stellar velocity dispersion. We find no evidence that the galaxy is rotating and is thus likely pressure-supported. The number of confirmed GCs, and the total number inferred for the system ($\sim$45), suggest a total halo mass of $\sim2 \times 10^{11}$ M$_{\odot}$. A cored mass profile is favoured when compared to our dynamical mass. Given its stellar mass of 1.1$\times$10$^{8}$ M$_{\odot}$, NGC 5846_UDG1 appears to be an ultra-diffuse galaxy with a dwarf-like stellar mass and an overly massive halo., Comment: 6 pages, 5 figures, MNRAS

We present new spectra obtained using Keck/KCWI and perform kinematics and stellar population analyses of the shell galaxy NGC 474, from both the galaxy centre and a region from the outer shell. We show that both regions have similarly extended star formation histories although with different stellar population properties. The central region of NGC 474 is dominated by intermediate-aged stars (8.3 \pm 0.3 Gyr) with subsolar metallicity ([Z/H]= -0.24 \pm 0.07 dex) while the observed shell region, which hosts a substantial population of younger stars, has a mean luminosity-weighted age of 4.0 \pm 0.5 Gyr with solar metallicities ([Z/H]=-0.03 \pm 0.09 dex). Our results are consistent with a scenario in which NGC 474 experienced a major to intermediate merger with a log\((M_*/M_\odot)\sim10 \) mass satellite galaxy at least \sim 2 Gyr ago which produced its shell system. This work shows that the direct spectroscopic study of low-surface brightness stellar features, such as shells, is now feasible and opens up a new window to understanding galaxy formation and evolution., Comment: Accepted for publication in MNRAS, 6 pages, 5 figures

We present a catalogue of low surface brightness (LSB) galaxies in the Coma cluster obtained from deep Subaru/Suprime-Cam V and R-band imaging data within a region of $\sim$4 deg$^2$. We increase the number of LSB galaxies presented in Yagi et al. (2016) by a factor of $\sim$3 and report the discovery of 29 new ultra-diffuse galaxies (UDGs). We compile the largest sample of ultra-diffuse galaxies with colours and structural parameters in the Coma cluster. While most UDGs lie along the red-sequence relation of the colour-magnitude diagram, $\sim$5per cent are outside (bluer or redder) the red-sequence region of Coma cluster galaxies. Our analyses show that there is no special distinction in the basic photometric parameters between UDGs and other LSB galaxies. We investigate the clustercentric colour distribution and find a remarkable transition at a projected radius of $\sim$0.6 Mpc. Within this cluster core region, LSB galaxies are, on average, redder than co-spatial higher surface brightness galaxies, highlighting how vulnerable LSB galaxies are to the physical processes at play in the dense central region of the cluster. The position of the transition radius agrees with expectations from recent cosmological simulation of massive galaxy clusters within which ancient infalls are predicted to dominate the LSB galaxy population., Comment: Accepted for publication in MNRAS. The complete version of Table 2 is available online as supplementary material

Ultra diffuse galaxies (UDGs) reveal extreme properties. Here we compile the largest study to date of 85 globular cluster (GC) systems around UDGs in the Coma cluster, using new deep ground-based imaging of the known UDGs and existing imaging from the Hubble Space Telescope of their GC systems. We find that the richness of GC systems in UDGs generally exceeds that found in normal dwarf galaxies of the same stellar mass. These GC-rich UDGs imply halos more massive than expected from the standard stellar mass-halo mass relation. The presence of such overly massive halos presents a significant challenge to the latest simulations of UDGs in cluster environments. In some exceptional cases, the mass in the GC system is a significant fraction of the stellar content of the host galaxy. We find that rich GC systems tend to be hosted in UDGs of lower luminosity, smaller size and fainter surface brightness. Similar trends are seen for normal dwarf galaxies in the Coma cluster. A toy model is presented in which the GC-rich UDGs are assumed to be `failed' galaxies within massive halos that have largely old, metal-poor, alpha-element enhanced stellar populations. On the other hand, GC-poor UDGs are more akin to normal, low surface brightness dwarfs that occupy less massive dark matter halos. Additional data on the stellar populations of UDGs with GC systems will help to further refine and test this simplistic model., Comment: 11 pages, 11 figures, accepted for publication in MNRAS

We present new spectra obtained using Keck/KCWI and perform kinematics and stellar population analyses of the shell galaxy NGC 474, from both the galaxy centre and a region from the outer shell. We show that both regions have similarly extended star formation histories although with different stellar population properties. The central region of NGC 474 is dominated by intermediate-Aged stars (8.3 ± 0.3 Gyr) with subsolar metallicity ([Z/H] =-0.24 ± 0.07 dex) while the observed shell region, which hosts a substantial population of younger stars, has a mean luminosity-weighted age of 4.0 ± 0.5 Gyr with solar metallicities ([Z/H] =-0.03 ± 0.09 dex). Our results are consistent with a scenario in which NGC 474 experienced a major to intermediate merger with a log$(M_∗/\rm M_\odot) \sim 10$ mass satellite galaxy at least ${\sim}2$ Gyr ago which produced its shell system. This work shows that the direct spectroscopic study of low-surface brightness stellar features, such as shells, is now feasible and opens up a new window to understanding galaxy formation and evolution.

We study the globular clusters (GCs) in the spiral galaxy NGC~5907 well-known for its spectacular stellar stream -- to better understand its origin. Using wide-field Subaru/Suprime-Cam $gri$ images and deep Keck/DEIMOS multi-object spectroscopy, we identify and obtain the kinematics of several GCs superimposed on the stellar stream and the galaxy disk. We estimate the total number of globular clusters in NGC 5907 to be $154\pm44$, with a specific frequency of $0.73\pm0.21$. Our analysis also reveals a significant, new population of young star cluster candidates found mostly along the outskirts of the stellar disk. Using the properties of the stream GCs, we estimate that the disrupted galaxy has a stellar mass similar to the Sagittarius dwarf galaxy accreted by the Milky Way, i.e. $\sim10^8~M_\odot$., Comment: 9 pages, 9 figures, catalog of GCs is available in online version

The NGC 1052 group, and in particular the discovery of two ultra diffuse galaxies with very low internal velocity dispersions, has been the subject of much attention recently. Here we present radial velocities for a sample of 77 globular clusters associated with NGC 1052 obtained on the Keck telescope. Their mean velocity and velocity dispersion are consistent with that of the host galaxy. Using a simple tracer mass estimator, we infer the enclosed dynamical mass and dark matter fraction of NGC 1052. Extrapolating our measurements with an NFW mass profile we infer a total halo mass of 6.2 ($\pm$0.2) $\times$ 10$^{12}$ M$_{\odot}$. This mass is fully consistent with that expected from the stellar mass--halo mass relation, suggesting that NGC 1052 has a normal dark matter halo mass (i.e. it is not deficient in dark matter in contrast to two ultra diffuse galaxies in the group). We present a phase space diagram showing the galaxies that lie within the projected virial radius (390 kpc) of NGC 1052. Finally, we briefly discuss the two dark matter deficient galaxies (NGC 1052--DF and DF4) and consider whether MOND can account for their low observed internal velocity dispersions., Comment: 5 pages, 2 figures, 1 abridged Table, MNRAS accepted

Ultra diffuse galaxies are a population of extended galaxies but with relatively low luminosities. The origin of these objects remains unclear, largely due to the observational challenges of the low surface brightness Universe. We present here a detailed stellar population analysis of a relatively isolated UDG, DGSAT I, based on spectroscopic data from the Keck Cosmic Web Imager integral field unit. The star formation history of DGSAT I seems to be extended, with a mean luminosity-weighted age of ~3 Gyr, in agreement with previous photometric studies. However, we find a very high [Mg/Fe] abundance ratio, which is extreme even in the context of the highly alpha-enhanced massive ellipticals and ultra-faint dwarfs. The [Mg/Fe]-enhancement of DGSAT I appears to be 10 times higher than the most magnesium-enhanced stellar systems discovered to date, and suggests that the chemical enrichment of this object was dominated by core-collapse supernovae. Intriguingly, this breaks the canonical relation between [Mg/Fe] and star formation time-scale. With a measured velocity dispersion of 56 +/- 10 km/s, DGSAT I also shows a high mass-to-light ratio, which indicates that it is highly dark matter-dominated. The metal-poor conditions of DGSAT I may have enhanced the formation of massive stars, while at the same time, additional mechanisms are needed to prevent iron-rich yields from being recycled into stars. These results suggest that some ultra-diffuse galaxies could have experienced chemical enrichment episodes similar to the first building blocks of galaxies., Comment: 10 pages, 7 figures, MNRAS, accepted

Ultra diffuse galaxies are a population of extended galaxies but with relatively low luminosities. The origin of these objects remains unclear, largely due to the observational challenges of the low surface brightness Universe. We present here a detailed stellar population analysis of a relatively isolated UDG, DGSAT I, based on spectroscopic data from the Keck Cosmic Web Imager integral field unit. The star formation history of DGSAT I seems to be extended, with a mean luminosity-weighted age of ~3 Gyr, in agreement with previous photometric studies. However, we find a very high [Mg/Fe] abundance ratio, which is extreme even in the context of the highly alpha-enhanced massive ellipticals and ultra-faint dwarfs. The [Mg/Fe]-enhancement of DGSAT I appears to be 10 times higher than the most magnesium-enhanced stellar systems discovered to date, and suggests that the chemical enrichment of this object was dominated by core-collapse supernovae. Intriguingly, this breaks the canonical relation between [Mg/Fe] and star formation time-scale. With a measured velocity dispersion of 56 +/- 10 km/s, DGSAT I also shows a high mass-to-light ratio, which indicates that it is highly dark matter-dominated. The metal-poor conditions of DGSAT I may have enhanced the formation of massive stars, while at the same time, additional mechanisms are needed to prevent iron-rich yields from being recycled into stars. These results suggest that some ultra-diffuse galaxies could have experienced chemical enrichment episodes similar to the first building blocks of galaxies., Comment: 10 pages, 7 figures, MNRAS, accepted

We study the globular clusters (GCs) in the spiral galaxy NGC~5907 well-known for its spectacular stellar stream -- to better understand its origin. Using wide-field Subaru/Suprime-Cam $gri$ images and deep Keck/DEIMOS multi-object spectroscopy, we identify and obtain the kinematics of several GCs superimposed on the stellar stream and the galaxy disk. We estimate the total number of globular clusters in NGC 5907 to be $154\pm44$, with a specific frequency of $0.73\pm0.21$. Our analysis also reveals a significant, new population of young star cluster candidates found mostly along the outskirts of the stellar disk. Using the properties of the stream GCs, we estimate that the disrupted galaxy has a stellar mass similar to the Sagittarius dwarf galaxy accreted by the Milky Way, i.e. $\sim10^8~M_\odot$., Comment: 9 pages, 9 figures, catalog of GCs is available in online version

The NGC 1052 group, and in particular the discovery of two ultra diffuse galaxies with very low internal velocity dispersions, has been the subject of much attention recently. Here we present radial velocities for a sample of 77 globular clusters associated with NGC 1052 obtained on the Keck telescope. Their mean velocity and velocity dispersion are consistent with that of the host galaxy. Using a simple tracer mass estimator, we infer the enclosed dynamical mass and dark matter fraction of NGC 1052. Extrapolating our measurements with an NFW mass profile we infer a total halo mass of 6.2 ($\pm$0.2) $\times$ 10$^{12}$ M$_{\odot}$. This mass is fully consistent with that expected from the stellar mass--halo mass relation, suggesting that NGC 1052 has a normal dark matter halo mass (i.e. it is not deficient in dark matter in contrast to two ultra diffuse galaxies in the group). We present a phase space diagram showing the galaxies that lie within the projected virial radius (390 kpc) of NGC 1052. Finally, we briefly discuss the two dark matter deficient galaxies (NGC 1052--DF and DF4) and consider whether MOND can account for their low observed internal velocity dispersions., Comment: 5 pages, 2 figures, 1 abridged Table, MNRAS accepted

Using data from the WiFeS Atlas of Galactic Globular cluster Spectra we study the behaviour of the calcium triplet (CaT), a popular metallicity indicator in extragalactic stellar population studies. A major caveat of these studies is that the potential sensitivity to other stellar population parameters such as age, calcium abundance and the initial mass function has not yet been empirically evaluated. Here we present measurements of the strength of the CaT feature for 113 globular clusters in the Milky Way and its satellite galaxies. We derive empirical calibrations between the CaT index and both the iron abundance ([Fe/H]) and calcium abundance ([Ca/H]), finding a tighter relationship for [Ca/H] than for [Fe/H]. For stellar populations 3 Gyr and older the CaT can be used to reliably measure [Ca/H] at the 0.1 dex level but becomes less reliable for ages of $\sim 2$ Gyr and younger. We find that the CaT is relatively insensitive to the horizontal branch morphology. The stellar mass function however affects the CaT strengths significantly only at low metallicities. Using our newly derived empirical calibration, we convert our measured CaT indices into [Ca/H] values for the globular clusters in our sample., Comment: 33 pages, 27 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

Using globular cluster (GC) kinematics and photometry data, we calibrate the scaling relation between the total galaxy mass (M_TOT including dark matter) and total globular cluster system mass (M_GCS) in a sample of 30 early-type galaxies (ETG), confirming a nearly linear relationship between the two physical parameters. Using samples of 83 and 57 ETGs, we investigate this scaling relation in conjunction with the previously known relations between M_TOT and the ISM X-ray luminosity and temperature, respectively. We confirm that M_GCS can be effectively used as a proxy of M_TOT. We further find that the L_X,GAS - M_TOT relation is far tighter in the subsample of core ETGs, when compared to cusp ETGs. In core ETGs (old, passively evolving stellar systems) M_TOT is significantly larger than the total stellar mass M_STAR and the correlation with the hot gas properties is driven by their dark matter mass M_DM. Cusp ETGs have typically lower LX,GAS than core ETGs. In cusp ETGs, for a given M_DM, higher L_X,GAS is associated with higher M_STAR, suggesting stellar feedback as an important secondary factor for heating the ISM. Using the M_GCS- M_TOT scaling relations we compare 272 ETGs with previous estimates of the stellar-to-halo mass relation of galaxies. Our model-independent estimate of M_TOT results in a good agreement around halo masses of 10^12 Mo, but suggest higher star formation efficiency than usually assumed both at the low and at the high halo mass ends., Comment: 28 pages, 13 figures, accepted in MNRAS, added new correlations with T(GAS)

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy formation and evolution, since they present properties that can be found in both elliptical and spiral galaxies. In this work we study the kinematics of the globular cluster (GC) systems of three lenticular galaxies located in low density environments (NGC 2768, NGC 3115 and NGC 7457), and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768 we find that its red GCs display rotation preferentially at inner radii (Re<1). In the case of the GC system of NGC 3115 we find a group of GCs with similar kinematics that are not likely to belong to either its spheroid nor disc. For NGC 7457 we find that 70% of its GCs are likely to belong to the disc. Overall, our results suggest that these galaxies assembled into S0s through different evolutionary paths. Mergers seem to have been very important for NGC 2768 and NGC 3115 while NGC 7457 is more likely to have experienced secular evolution., Comment: 13 pages, 10 figures, Accepted for publication in MNRAS

We use Keck/DEIMOS spectroscopy to confirm the cluster membership of 16 ultra-diffuse galaxies (UDGs) in the Coma cluster, bringing the total number of spectroscopically con- firmed UDGs to 24. We also identify a new cluster background UDG. In this pilot study of Coma UDGs in velocity phase-space, we find evidence that most present-day Coma UDGs have a recent infall epoch while a few may be ancient infalls. These recent infall UDGs have higher absolute relative line-of-sight velocities, bluer optical colors, and are smaller in size, unlike the ancient infalls. The kinematics of the spectroscopically confirmed Coma UDG sample is similar to that of the cluster late-type galaxy population. Our velocity phase-space analysis suggests that present-day cluster UDGs have a predominantly accretion origin from the field, acquire velocities corresponding to the mass of the cluster at accretion as they are accelerated towards the cluster center, and become redder and bigger as they experience the various physical processes at work within the cluster., Comment: 9 Figures, 1 Table, submitted to MNRAS

In this second paper of the series, we study with new Keck/DEIMOS spectra the stellar populations of seven spectroscopically confirmed ultra-diffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (~ 7Gyr), low metallicities ([Z/H] ~ -0.7dex) and mostly super-solar abundance patterns ([Mg/Fe] ~ 0.13dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are most consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin. However, considering the scatter in the resulting properties and including other UDGs in Coma, together with the results from the velocity phase-space study of the Paper I in this series, a mixed-bag of origins is needed to explain the nature of all UDGs. Our results thus reinforce a scenario in which many UDGs are field dwarfs that become quenched through their later infall onto cluster environments, whereas some UDGs could be genuine primordial galaxies that failed to develop due to an early quenching phase. The unknown proportion of dwarf-like to primordial-like UDGs leaves the enigma of the nature of UDGs still open., Comment: Accepted for publication at MNRAS

We apply the Jeans Anisotropic MGE (JAM) dynamical modelling method to SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey data of early-type galaxies in the stellar mass range $10^{10}10^{10.7}{\rm M}_{\odot}$ in the Magneticum simulations, we identify a significant anticorrelation between total-mass density profile slopes and the fraction of stellar mass formed ex situ (i.e. accreted), whereas this anticorrelation is weaker for lower stellar masses, implying that the measured total mass density slopes for low-mass galaxies are less likely to be determined by merger activity., Comment: Published in MNRAS. ArXiv paper replaced to reflect updated total-mass density slope values for model 2, as described by the published erratum to the original paper

We use the IllustrisTNG (TNG) cosmological simulations to provide theoretical expectations for the dark matter mass fractions (DMFs) and circular velocity profiles of galaxies. TNG predicts flat circular velocity curves for $z = 0$ Milky Way (MW)-like galaxies beyond a few kpc from the galaxy centre, in better agreement with observational constraints than its predecessor, Illustris. TNG also predicts an enhancement of the dark matter mass within the 3D stellar half-mass radius ($r_\mathrm{half}$; $M_\mathrm{200c} = 10^{10}-10^{13}\mathrm{M}_{\odot}$, $z \le2$) compared to its dark matter only and Illustris counterparts. This enhancement leads TNG present-day galaxies to be dominated by dark matter within their inner regions, with $f_\mathrm{DM}(

Using globular cluster (GC) kinematics and photometry data, we calibrate the scaling relation between the total galaxy mass (M_TOT including dark matter) and total globular cluster system mass (M_GCS) in a sample of 30 early-type galaxies (ETG), confirming a nearly linear relationship between the two physical parameters. Using samples of 83 and 57 ETGs, we investigate this scaling relation in conjunction with the previously known relations between M_TOT and the ISM X-ray luminosity and temperature, respectively. We confirm that M_GCS can be effectively used as a proxy of M_TOT. We further find that the L_X,GAS - M_TOT relation is far tighter in the subsample of core ETGs, when compared to cusp ETGs. In core ETGs (old, passively evolving stellar systems) M_TOT is significantly larger than the total stellar mass M_STAR and the correlation with the hot gas properties is driven by their dark matter mass M_DM. Cusp ETGs have typically lower LX,GAS than core ETGs. In cusp ETGs, for a given M_DM, higher L_X,GAS is associated with higher M_STAR, suggesting stellar feedback as an important secondary factor for heating the ISM. Using the M_GCS- M_TOT scaling relations we compare 272 ETGs with previous estimates of the stellar-to-halo mass relation of galaxies. Our model-independent estimate of M_TOT results in a good agreement around halo masses of 10^12 Mo, but suggest higher star formation efficiency than usually assumed both at the low and at the high halo mass ends., Comment: 28 pages, 13 figures, accepted in MNRAS, added new correlations with T(GAS)

Using data from the WiFeS Atlas of Galactic Globular cluster Spectra we study the behaviour of the calcium triplet (CaT), a popular metallicity indicator in extragalactic stellar population studies. A major caveat of these studies is that the potential sensitivity to other stellar population parameters such as age, calcium abundance and the initial mass function has not yet been empirically evaluated. Here we present measurements of the strength of the CaT feature for 113 globular clusters in the Milky Way and its satellite galaxies. We derive empirical calibrations between the CaT index and both the iron abundance ([Fe/H]) and calcium abundance ([Ca/H]), finding a tighter relationship for [Ca/H] than for [Fe/H]. For stellar populations 3 Gyr and older the CaT can be used to reliably measure [Ca/H] at the 0.1 dex level but becomes less reliable for ages of $\sim 2$ Gyr and younger. We find that the CaT is relatively insensitive to the horizontal branch morphology. The stellar mass function however affects the CaT strengths significantly only at low metallicities. Using our newly derived empirical calibration, we convert our measured CaT indices into [Ca/H] values for the globular clusters in our sample., Comment: 33 pages, 27 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy formation and evolution, since they present properties that can be found in both elliptical and spiral galaxies. In this work we study the kinematics of the globular cluster (GC) systems of three lenticular galaxies located in low density environments (NGC 2768, NGC 3115 and NGC 7457), and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768 we find that its red GCs display rotation preferentially at inner radii (Re<1). In the case of the GC system of NGC 3115 we find a group of GCs with similar kinematics that are not likely to belong to either its spheroid nor disc. For NGC 7457 we find that 70% of its GCs are likely to belong to the disc. Overall, our results suggest that these galaxies assembled into S0s through different evolutionary paths. Mergers seem to have been very important for NGC 2768 and NGC 3115 while NGC 7457 is more likely to have experienced secular evolution., Comment: 13 pages, 10 figures, Accepted for publication in MNRAS

We apply the Jeans Anisotropic MGE (JAM) dynamical modelling method to SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey data of early-type galaxies in the stellar mass range $10^{10}10^{10.7}{\rm M}_{\odot}$ in the Magneticum simulations, we identify a significant anticorrelation between total-mass density profile slopes and the fraction of stellar mass formed ex situ (i.e. accreted), whereas this anticorrelation is weaker for lower stellar masses, implying that the measured total mass density slopes for low-mass galaxies are less likely to be determined by merger activity., Comment: Published in MNRAS. ArXiv paper replaced to reflect updated total-mass density slope values for model 2, as described by the published erratum to the original paper

In this second paper of the series, we study with new Keck/DEIMOS spectra the stellar populations of seven spectroscopically confirmed ultra-diffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (~ 7Gyr), low metallicities ([Z/H] ~ -0.7dex) and mostly super-solar abundance patterns ([Mg/Fe] ~ 0.13dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are most consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin. However, considering the scatter in the resulting properties and including other UDGs in Coma, together with the results from the velocity phase-space study of the Paper I in this series, a mixed-bag of origins is needed to explain the nature of all UDGs. Our results thus reinforce a scenario in which many UDGs are field dwarfs that become quenched through their later infall onto cluster environments, whereas some UDGs could be genuine primordial galaxies that failed to develop due to an early quenching phase. The unknown proportion of dwarf-like to primordial-like UDGs leaves the enigma of the nature of UDGs still open., Comment: Accepted for publication at MNRAS

We use Keck/DEIMOS spectroscopy to confirm the cluster membership of 16 ultra-diffuse galaxies (UDGs) in the Coma cluster, bringing the total number of spectroscopically con- firmed UDGs to 24. We also identify a new cluster background UDG. In this pilot study of Coma UDGs in velocity phase-space, we find evidence that most present-day Coma UDGs have a recent infall epoch while a few may be ancient infalls. These recent infall UDGs have higher absolute relative line-of-sight velocities, bluer optical colors, and are smaller in size, unlike the ancient infalls. The kinematics of the spectroscopically confirmed Coma UDG sample is similar to that of the cluster late-type galaxy population. Our velocity phase-space analysis suggests that present-day cluster UDGs have a predominantly accretion origin from the field, acquire velocities corresponding to the mass of the cluster at accretion as they are accelerated towards the cluster center, and become redder and bigger as they experience the various physical processes at work within the cluster., Comment: 9 Figures, 1 Table, submitted to MNRAS

We use the IllustrisTNG (TNG) cosmological simulations to provide theoretical expectations for the dark matter mass fractions (DMFs) and circular velocity profiles of galaxies. TNG predicts flat circular velocity curves for $z = 0$ Milky Way (MW)-like galaxies beyond a few kpc from the galaxy centre, in better agreement with observational constraints than its predecessor, Illustris. TNG also predicts an enhancement of the dark matter mass within the 3D stellar half-mass radius ($r_\mathrm{half}$; $M_\mathrm{200c} = 10^{10}-10^{13}\mathrm{M}_{\odot}$, $z \le2$) compared to its dark matter only and Illustris counterparts. This enhancement leads TNG present-day galaxies to be dominated by dark matter within their inner regions, with $f_\mathrm{DM}(

We investigate the dark matter density profile of the massive elliptical galaxy, NGC 1407, by constructing spherically symmetric Jeans models of its field star and globular cluster systems. Two major challenges in such models are the degeneracy between the stellar mass and the dark matter halo profiles, and the degeneracy between the orbital anisotropy of the tracer population and the total mass causing the observed motions. We address the first issue by using new measurements of the mass-to-light ratio profile from stellar population constraints that include a radially varying initial mass function. To deal with the mass--anisotropy degeneracy, we make use of multiple kinematic tracers, including two subpopulations of globular clusters in addition to the galaxy's field stars. We create a hierarchical Bayesian model that addresses several often neglected systematic uncertainties, such as the statistical weight given to various datasets and the adopted distance. After sampling the posterior probability distribution with a Markov Chain Monte Carlo method, we find evidence for a central cusp with a log-slope of $\gamma = 1.0^{+0.3}_{-0.4}$. This is lower than expected for dark matter halos that have undergone adiabatic contraction, supporting inferences from gravitational lensing that some process has suppressed the steepening of halos in massive galaxies. We also confirm radially-biased orbits for the metal-rich globular clusters and tangentially-biased orbits for the metal-poor globular clusters, which remains a puzzling finding for an accretion-dominated halo., Comment: 23 pages, 19 figures, submitted to ApJ

Without the interference of a number of events, galaxies may suffer in crowded environments (e.g., stripping, harassment, strangulation); isolated elliptical galaxies provide a control sample for the study of galaxy formation. We present the study of a sample of isolated ellipticals using imaging from a variety of telescopes, focusing on their globular cluster systems as tracers of their stellar halos. Our main findings are: (a) GC color bimodality is common even in the most isolated systems; (b) the specific frequency of GCs is fairly constant with galaxy mass, without showing an increase towards high-mass systems like in the case of cluster ellipticals; (c) on the other hand, the red fraction of GCs follows the same inverted V shape trend with mass as seen in cluster ellipticals; and (d) the stellar halos show low S\'ersic indices which are consistent with a major merger origin., Comment: 5 pages. Published in the special issue of Galaxies, "On the Origin (and Evolution) of Baryonic Galaxy Halos"

We present the WiFeS Atlas of Galactic Globular cluster Spectra, a library of integrated spectra of Milky Way and Local Group globular clusters. We used the WiFeS integral field spectrograph on the Australian National University 2.3 m telescope to observe the central regions of 64 Milky Way globular clusters and 22 globular clusters hosted by the Milky Way's low mass satellite galaxies. The spectra have wider wavelength coverage (3300 {\AA} to 9050 {\AA}) and higher spectral resolution (R = 6800) than existing spectral libraries of Milky Way globular clusters. By including Large and Small Magellanic Cloud star clusters, we extend the coverage of parameter space of existing libraries towards young and intermediate ages. While testing stellar population synthesis models and analysis techniques is the main aim of this library, the observations may also further our understanding of the stellar populations of Local Group globular clusters and make possible the direct comparison of extragalactic globular cluster integrated light observations with well understood globular clusters in the Milky Way. The integrated spectra are publicly available via the project website., Comment: 25 pages, 15 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society

Here we present positions and radial velocities for over 4000 globular clusters (GCs) in 27 nearby early-type galaxies from the SLUGGS survey. The SLUGGS survey is designed to be representative of elliptical and lenticular galaxies in the stellar mass range 10 $<$ log M$_{\ast}$/M$_{\odot}$ $<$ 11.7. The data have been obtained over many years, mostly using the very stable multi-object spectrograph DEIMOS on the Keck II 10m telescope. Radial velocities are measured using the calcium triplet lines with a velocity accuracy of $\pm$ 10-15 km/s. We use phase space diagrams (i.e. velocity--position diagrams) to identify contaminants such as foreground stars and background galaxies, and to show that the contribution of GCs from neighboring galaxies is generally insignificant. Likely ultra-compact dwarfs are tabulated separately. We find that the mean velocity of the GC system is close to that of the host galaxy systemic velocity, indicating that the GC system is in overall dynamical equilibrium within the galaxy potential. We also find that the GC system velocity dispersion scales with host galaxy stellar mass in a similar manner to the Faber-Jackson relation for the stellar velocity dispersion. Publication of these GC radial velocity catalogs should enable further studies in many areas, such as GC system substructure, kinematics, and host galaxy mass measurements., Comment: 16 pages, accepted for publication in the Astronomical Journal, online data files can be found at sluggs.swin.edu.au

We use globular cluster kinematics data, primarily from the SLUGGS survey, to measure the dark matter fraction ($f_{\rm DM}$) and the average dark matter density ($\left< \rho_{\rm DM} \right>$) within the inner 5 effective radii ($R_{\rm e}$) for 32 nearby early--type galaxies (ETGs) with stellar mass log $(M_*/\rm M_\odot)$ ranging from $10.1$ to $11.8$. We compare our results with a simple galaxy model based on scaling relations as well as with cosmological hydrodynamical simulations where the dark matter profile has been modified through various physical processes. We find a high $f_{\rm DM}$ ($\geq0.6$) within 5~$R_{\rm e}$ in most of our sample, which we interpret as a signature of a late mass assembly history that is largely devoid of gas-rich major mergers. However, around log $(M_*/M_\odot) \sim 11$, there is a wide range of $f_{\rm DM}$ which may be challenging to explain with any single cosmological model. We find tentative evidence that lenticulars (S0s), unlike ellipticals, have mass distributions that are similar to spiral galaxies, with decreasing $f_{\rm DM}$ within 5~$R_{\rm e}$ as galaxy luminosity increases. However, we do not find any difference between the $\left< \rho_{\rm DM} \right>$ of S0s and ellipticals in our sample, despite the differences in their stellar populations. We have also used $\left< \rho_{\rm DM} \right>$ to infer the epoch of halo assembly ($z{\sim}2-4$). By comparing the age of their central stars with the inferred epoch of halo formation, we are able to gain more insight into their mass assembly histories. Our results suggest a fundamental difference in the dominant late-phase mass assembly channel between lenticulars and elliptical galaxies., Comment: Accepted for publication in MNRAS, 10 figures. Figures 2 and 3 have been slightly modified from the previous version, with the introduction of a new simple galaxy model

We utilise the DEIMOS instrument on the Keck telescope to measure the wide-field stellar kinematics of early-type galaxies as part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey. In this paper, we focus on some of the lowest stellar mass lenticular galaxies within this survey, namely NGC 2549, NGC 4474, NGC 4459 and NGC 7457, performing detailed kinematic analyses out to large radial distances of $\sim 2-3$ effective radii. For NGC 2549, we present the first analysis of data taken with the SuperSKiMS (Stellar Kinematics from Multiple Slits) technique. To better probe kinematic variations in the outskirts of the SLUGGS galaxies, we have defined a local measure of stellar spin. We use this parameter and identify a clear separation in the radial behaviour of stellar spin between lenticular and elliptical galaxies, thereby reinforcing the physically meaningful nature of their morphological classifications. We compare the kinematic properties of our galaxies with those from various simulated galaxies to extract plausible formation scenarios. By doing this for multiple simulations, we assess the consistency of the theoretical results. Comparisons to binary merger simulations show that low-mass lenticular galaxies generally resemble the spiral progenitors more than the merger remnants themselves, an indication that these galaxies are not formed through merger events. We find, however, that recent mergers cannot be ruled out for some lenticular galaxies., Comment: 20 pages, 15 figures, accepted to MNRAS

We investigate the dark matter density profile of the massive elliptical galaxy, NGC 1407, by constructing spherically symmetric Jeans models of its field star and globular cluster systems. Two major challenges in such models are the degeneracy between the stellar mass and the dark matter halo profiles, and the degeneracy between the orbital anisotropy of the tracer population and the total mass causing the observed motions. We address the first issue by using new measurements of the mass-to-light ratio profile from stellar population constraints that include a radially varying initial mass function. To deal with the mass--anisotropy degeneracy, we make use of multiple kinematic tracers, including two subpopulations of globular clusters in addition to the galaxy's field stars. We create a hierarchical Bayesian model that addresses several often neglected systematic uncertainties, such as the statistical weight given to various datasets and the adopted distance. After sampling the posterior probability distribution with a Markov Chain Monte Carlo method, we find evidence for a central cusp with a log-slope of $\gamma = 1.0^{+0.3}_{-0.4}$. This is lower than expected for dark matter halos that have undergone adiabatic contraction, supporting inferences from gravitational lensing that some process has suppressed the steepening of halos in massive galaxies. We also confirm radially-biased orbits for the metal-rich globular clusters and tangentially-biased orbits for the metal-poor globular clusters, which remains a puzzling finding for an accretion-dominated halo., Comment: 23 pages, 19 figures, submitted to ApJ

Without the interference of a number of events, galaxies may suffer in crowded environments (e.g., stripping, harassment, strangulation); isolated elliptical galaxies provide a control sample for the study of galaxy formation. We present the study of a sample of isolated ellipticals using imaging from a variety of telescopes, focusing on their globular cluster systems as tracers of their stellar halos. Our main findings are: (a) GC color bimodality is common even in the most isolated systems; (b) the specific frequency of GCs is fairly constant with galaxy mass, without showing an increase towards high-mass systems like in the case of cluster ellipticals; (c) on the other hand, the red fraction of GCs follows the same inverted V shape trend with mass as seen in cluster ellipticals; and (d) the stellar halos show low S\'ersic indices which are consistent with a major merger origin., Comment: 5 pages. Published in the special issue of Galaxies, "On the Origin (and Evolution) of Baryonic Galaxy Halos"

We present the WiFeS Atlas of Galactic Globular cluster Spectra, a library of integrated spectra of Milky Way and Local Group globular clusters. We used the WiFeS integral field spectrograph on the Australian National University 2.3 m telescope to observe the central regions of 64 Milky Way globular clusters and 22 globular clusters hosted by the Milky Way's low mass satellite galaxies. The spectra have wider wavelength coverage (3300 {\AA} to 9050 {\AA}) and higher spectral resolution (R = 6800) than existing spectral libraries of Milky Way globular clusters. By including Large and Small Magellanic Cloud star clusters, we extend the coverage of parameter space of existing libraries towards young and intermediate ages. While testing stellar population synthesis models and analysis techniques is the main aim of this library, the observations may also further our understanding of the stellar populations of Local Group globular clusters and make possible the direct comparison of extragalactic globular cluster integrated light observations with well understood globular clusters in the Milky Way. The integrated spectra are publicly available via the project website., Comment: 25 pages, 15 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society

We utilise the DEIMOS instrument on the Keck telescope to measure the wide-field stellar kinematics of early-type galaxies as part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey. In this paper, we focus on some of the lowest stellar mass lenticular galaxies within this survey, namely NGC 2549, NGC 4474, NGC 4459 and NGC 7457, performing detailed kinematic analyses out to large radial distances of $\sim 2-3$ effective radii. For NGC 2549, we present the first analysis of data taken with the SuperSKiMS (Stellar Kinematics from Multiple Slits) technique. To better probe kinematic variations in the outskirts of the SLUGGS galaxies, we have defined a local measure of stellar spin. We use this parameter and identify a clear separation in the radial behaviour of stellar spin between lenticular and elliptical galaxies, thereby reinforcing the physically meaningful nature of their morphological classifications. We compare the kinematic properties of our galaxies with those from various simulated galaxies to extract plausible formation scenarios. By doing this for multiple simulations, we assess the consistency of the theoretical results. Comparisons to binary merger simulations show that low-mass lenticular galaxies generally resemble the spiral progenitors more than the merger remnants themselves, an indication that these galaxies are not formed through merger events. We find, however, that recent mergers cannot be ruled out for some lenticular galaxies., Comment: 20 pages, 15 figures, accepted to MNRAS

We use globular cluster kinematics data, primarily from the SLUGGS survey, to measure the dark matter fraction ($f_{\rm DM}$) and the average dark matter density ($\left< \rho_{\rm DM} \right>$) within the inner 5 effective radii ($R_{\rm e}$) for 32 nearby early--type galaxies (ETGs) with stellar mass log $(M_*/\rm M_\odot)$ ranging from $10.1$ to $11.8$. We compare our results with a simple galaxy model based on scaling relations as well as with cosmological hydrodynamical simulations where the dark matter profile has been modified through various physical processes. We find a high $f_{\rm DM}$ ($\geq0.6$) within 5~$R_{\rm e}$ in most of our sample, which we interpret as a signature of a late mass assembly history that is largely devoid of gas-rich major mergers. However, around log $(M_*/M_\odot) \sim 11$, there is a wide range of $f_{\rm DM}$ which may be challenging to explain with any single cosmological model. We find tentative evidence that lenticulars (S0s), unlike ellipticals, have mass distributions that are similar to spiral galaxies, with decreasing $f_{\rm DM}$ within 5~$R_{\rm e}$ as galaxy luminosity increases. However, we do not find any difference between the $\left< \rho_{\rm DM} \right>$ of S0s and ellipticals in our sample, despite the differences in their stellar populations. We have also used $\left< \rho_{\rm DM} \right>$ to infer the epoch of halo assembly ($z{\sim}2-4$). By comparing the age of their central stars with the inferred epoch of halo formation, we are able to gain more insight into their mass assembly histories. Our results suggest a fundamental difference in the dominant late-phase mass assembly channel between lenticulars and elliptical galaxies., Comment: Accepted for publication in MNRAS, 10 figures. Figures 2 and 3 have been slightly modified from the previous version, with the introduction of a new simple galaxy model

Here we present positions and radial velocities for over 4000 globular clusters (GCs) in 27 nearby early-type galaxies from the SLUGGS survey. The SLUGGS survey is designed to be representative of elliptical and lenticular galaxies in the stellar mass range 10 $<$ log M$_{\ast}$/M$_{\odot}$ $<$ 11.7. The data have been obtained over many years, mostly using the very stable multi-object spectrograph DEIMOS on the Keck II 10m telescope. Radial velocities are measured using the calcium triplet lines with a velocity accuracy of $\pm$ 10-15 km/s. We use phase space diagrams (i.e. velocity--position diagrams) to identify contaminants such as foreground stars and background galaxies, and to show that the contribution of GCs from neighboring galaxies is generally insignificant. Likely ultra-compact dwarfs are tabulated separately. We find that the mean velocity of the GC system is close to that of the host galaxy systemic velocity, indicating that the GC system is in overall dynamical equilibrium within the galaxy potential. We also find that the GC system velocity dispersion scales with host galaxy stellar mass in a similar manner to the Faber-Jackson relation for the stellar velocity dispersion. Publication of these GC radial velocity catalogs should enable further studies in many areas, such as GC system substructure, kinematics, and host galaxy mass measurements., Comment: 16 pages, accepted for publication in the Astronomical Journal, online data files can be found at sluggs.swin.edu.au

Integral field unit spectrographs allow the 2D exploration of the kinematics and stellar populations of galaxies, although they are generally restricted to small fields-of-view. Using the large field-of-view of the DEIMOS multislit spectrograph on Keck and our Stellar Kinematics using Multiple Slits (SKiMS) technique, we are able to extract sky-subtracted stellar light spectra to large galactocentric radii. Here we present a new DEIMOS mask design named SuperSKiMS that explores large spatial scales without sacrificing high spatial sampling. We simulate a set of observations with such a mask design on the nearby galaxy NGC 1023, showing that the kinematic and metallicity measurements can reach radii where the galaxy surface brightness is several orders of magnitude fainter than the sky. Such a technique is also able to reproduce the kinematic and metallicity 2D distributions obtained from literature integral field spectroscopy in the innermost galaxy regions. In particular, we use the simulated NGC 1023 kinematics to model its total mass distribution to large radii, obtaining comparable results with those from published integral field unit observation. Finally, from new spectra of NGC 1023 we obtain stellar 2D kinematics and metallicity distributions that show good agreement with integral field spectroscopy results in the overlapping regions. In particular, we do not find a significant offset between our SKiMS and the ATLAS$^\rm{3D}$ stellar velocity dispersion at the same spatial locations., Comment: 18 pages. 10 figures. Accepted for publication in PASA

Here we utilise recent measures of galaxy total dynamical mass and X-ray gas luminosities (L$_{X,Gas}$) for a sample of 29 massive early-type galaxies from the SLUGGS survey to probe L$_{X,Gas}$--mass scaling relations. In particular, we investigate scalings with stellar mass, dynamical mass within 5 effective radii (R$_e$) and total virial mass. We also compare these relations with predictions from $\Lambda$CDM simulations. We find a strong linear relationship between L$_{X,Gas}$ and galaxy dynamical mass within 5 R$_e$, which is consistent with the recent cosmological simulations of Choi et al. that incorporate mechanical heating from AGN. We conclude that the gas surrounding massive early-type galaxies was shock heated as it fell into collapsing dark matter halos so that L$_{X,Gas}$ is primarily driven by the depth of a galaxy's potential well. Heating by an AGN plays an important secondary role in determining L$_{X,Gas}$., Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letters

We study mass distributions within and beyond 5~effective radii ($R_{\rm e}$) in 23 early-type galaxies from the SLUGGS survey, using their globular cluster (GC) kinematic data. The data are obtained with Keck/DEIMOS spectrograph, and consist of line-of-sight velocities for ~$3500$ GCs, measured with a high precision of ~15 $\rm km\ s^{-1}$ per GC and extending out to $~13 R_{\rm e}$. We obtain the mass distribution in each galaxy using the tracer mass estimator of Watkins et al. and account for kinematic substructures, rotation of the GC systems and galaxy flattening in our mass estimates. The observed scatter between our mass estimates and results from the literature is less than 0.2 dex. The dark matter fraction within $5R_{\rm e}$ ($f_{\rm DM}$) increases from ~$0.6$ to ~$0.8$ for low- and high-mass galaxies, respectively, with some intermediate-mass galaxies ($M_*{\sim}10^{11}M_\odot$) having low $f_{\rm DM}\sim0.3$, which appears at odds with predictions from simple galaxy models. We show that these results are independent of the adopted orbital anisotropy, stellar mass-to-light ratio, and the assumed slope of the gravitational potential. However, the low $f_{\rm DM}$ in the ~$10^{11}M_\odot$ galaxies agrees with the cosmological simulations of Wu et al. where the pristine dark matter distribution has been modified by baryons during the galaxy assembly process. We find hints that these $M_*\sim10^{11}M_\odot$ galaxies with low $f_{\rm DM}$ have very diffuse dark matter haloes, implying that they assembled late. Beyond $5R_{\rm e}$, the $M/L$ gradients are steeper in the more massive galaxies and shallower in both low and intermediate mass galaxies., Comment: 24 pages, 13 figures, 9 tables - Accepted for publication in MNRAS