We examine stellar population gradients in ~100 massive early type galaxies spanning 180 < sigma* < 370 km/s and M_K of -22.5 to -26.5 mag, observed as part of the MASSIVE survey (Ma et al. 2014). Using integral-field spectroscopy from the Mitchell Spectrograph on the 2.7m telescope at McDonald Observatory, we create stacked spectra as a function of radius for galaxies binned by their stellar velocity dispersion, stellar mass, and group richness. With excellent sampling at the highest stellar mass, we examine radial trends in stellar population properties extending to beyond twice the effective radius (~2.5 R_e). Specifically, we examine trends in age, metallicity, and abundance ratios of Mg, C, N, and Ca, and discuss the implications for star formation histories and elemental yields. At a fixed physical radius of 3-6 kpc (the likely size of the galaxy cores formed at high redshift) stellar age and [alpha/Fe] increase with increasing sigma* and depend only weakly on stellar mass, as we might expect if denser galaxies form their central cores earlier and faster. If we instead focus on 1-1.5 R_e, the trends in abundance and abundance ratio are washed out, as might be expected if the stars at large radius were accreted by smaller galaxies. Finally, we show that when controlling for \sigmastar, there are only very subtle differences in stellar population properties or gradients as a function of group richness; even at large radius internal properties matter more than environment in determining star formation history.
We model the dynamics of dwarf early-type galaxies in the Virgo cluster when subject to a variety of environmental processes. We focus on how these processes imprint trends in dynamical state (rotational vs. pressure support as measured by the $λ^*_{\rm Re/2}$ statistic) with projected distance from the cluster center, and compare these results to observational estimates. We find a large scatter in the gradient of $λ^*_{\rm Re/2}$ with projected radius. A statistical analysis shows that models with no environmental effects produce gradients as steep as those observed in none of the 100 cluster…
In this second paper of T$h$e role of $E$nvironment in shaping $L$ow-mass $E$arly-type $N$earby g$a$laxies (hELENa) series we study [Mg/Fe] abundance distribution trends of early-type galaxies observed with the SAURON integral field unit, spanning a wide range in mass and local environment densities: 20 low-mass early-types (dEs) of Sybilska et al. (2017) and 258 massive early types (ETGs) of the $ATLAS^{3D}$ project, all homogeneously reduced and analyzed. We show that the [Mg/Fe] ratios scale with velocity dispersion ($σ$) at fixed [Fe/H] and that they evolve with [Fe/H] along similar paths …
A strong correlation between atmospheric pressure and molecular gas mass is found in central cluster galaxies and early-type galaxies. This trend and a similar trend with atmospheric gas density would naturally arise if the molecular clouds condensed from hot atmospheres. Limits on the ratio of molecular to atomic hydrogen in these systems exceed unity. The data are consistent with ambient pressure being a significant factor in the rapid conversion of atomic hydrogen into molecules as found in normal spiral galaxies.
We study trends in the slope of the total mass profiles and dark matter fractions within the central half-light radius of 258 early-type galaxies, using data from the volume-limited ATLAS$^{\mathrm{3D}}$ survey. We use three distinct sets of dynamical models, which vary in their assumptions and also allow for spatial variations in the stellar mass-to-light ratio, to test the robustness of our results. We confirm that the slopes of the total mass profiles are approximately isothermal, and investigate how the total-mass slope depends on various galactic properties. The most statistically-signifi…
We apply a spectral stacking technique to Westerbork Synthesis Radio Telescope observations to measure the neutral atomic hydrogen content (HI) of nearby galaxies in and around galaxy groups at $z < 0.11$. Our sample includes 577 optically-selected galaxies (120 isolated galaxies and 457 satellites) covering stellar masses between 10$^{10}$ and 10$^{11.5}$ M$_{\odot}$, cross-matched with Yang's group catalogue, with angular and redshift positions from the Sloan Digital Sky Survey. We find that the satellites in the centres of groups have lower HI masses at fixed stellar mass and morphology (ch…
It has been shown that galaxy properties depend strongly on their host environment. In order to understand the relevant physical processes driving galaxy evolution it is important to study the observed properties of galaxies in different environments. Mass segregation in bound galaxy structures is an important indicator of evolutionary history and dynamical friction timescales. Using group catalogues derived from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) we investigate mass segregation trends in galaxy groups at low redshift. We investigate average galaxy stellar mass as a functio…
The gas metallicity distributions across individual galaxies and across galaxy samples can teach us much about how galaxies evolve. Massive galaxies typically possess negative metallicity gradients, and mass and metallicity are tightly correlated on local scales over wide range of galaxy masses; however, the precise origins of such trends remain elusive. Here, we employ data from SDSS-IV MaNGA to explore how gas metallicity depends on local stellar mass density and on galactocentric radius within individual galaxies. We also consider how the strengths of these dependencies vary across the gala…
Recent observations have probed the formation histories of nearby elliptical galaxies by tracking correlations between the stellar population parameters, age and metallicity, and the structural parameters that enter the Fundamental Plane, radius and velocity dispersion sigma. These studies have found intriguing correlations between these four parameters. In this work, we make use of a semi-analytic model, based on halo merger trees extracted from the Bolshoi cosmological simulation, that predicts the structural properties of spheroid-dominated galaxies based on an analytic model that has been …
Context. This is the third study of a series dedicated to the observed parallelism of properties between Galaxy Clusters and Groups(GCGs) and early-type galaxies (ETGs). Aims. Here we investigate the physical origin of the Mass-Radius Relation (MRR). Methods. Having collected literature data on masses and radii for objects going from Globular Clusters (GCs) to ETGs and GCGs, we set up the MR-plane and compare the observed distribution with the MRR predicted by theoretical models both for the monolithic and hierarchical scenarios. Results. We argue that the distributions of stellar systems in t…
I review our understanding of classic dynamical scaling relations, relating luminosity, size and kinematics of early-type galaxies. Using unbiased determinations of galaxy mass profiles from stellar dynamical models, a simple picture has emerged in which scaling relations are driven by virial equilibrium, accompanied by a trend in the stellar mass-to-light ratio (M/L). This picture confirms the earliest insights. The trend is mainly due to the combined variation of age, metallicity and the stellar initial mass function (IMF). The systematic variations best correlate with the galaxy velocity di…
Due to longer dynamical timescales, the outskirts of early-type galaxies retain the footprint of their formation and assembly. Under the popular two-phase galaxy formation scenario, an initial in-situ phase of star formation is followed by minor merging and accretion of ex-situ stars leading to the expectation of observable transitions in the kinematics and stellar populations on large scales. However, observing the faint galactic outskirts is challenging, often leaving the transition unexplored. The large scale, spatially-resolved stellar kinematic data from the SAGES Legacy Unifying Galaxies…
The formation and growth of globular cluster systems (GCSs) is closely related to the evolutionary processes experienced by their host galaxies. In particular, their radial distributions scale with several properties of the galaxies and their halos. We performed a photometric study, by means of HST/ACS archival data of several intermediate luminosity galaxies located in low density environments. It was supplemented with available photometric data of GCSs from the Virgo and Fornax clusters, resulting in a sample of almost 30 GCSs for which we fitted their radial profiles. The resulting overall …
Simpson's paradox, or Yule-Simpson effect, arises when a trend appears in different subsets of data but disappears or reverses when these subsets are combined. We describe here seven cases of this phenomenon for chemo-kinematical relations believed to constrain the Milky Way disk formation and evolution. We show that interpreting trends in relations, such as the radial and vertical chemical abundance gradients, the age-metallicity relation, and the metallicity-rotational velocity relation (MVR), can lead to conflicting conclusions about the Galaxy past if analyses marginalize over stellar age …
We study the evolutionary trend of the total density profile of early-type galaxies (ETGs) in IllustrisTNG. To this end, we trace ETGs from $z=0$ to $z=4$ and measure the power-law slope $γ^{\prime}$ of the total density profile for their main progenitors. We find that their $γ^{\prime}$ steepen on average during $z\sim4-2$, then becoming shallower until $z=1$, after which they remain almost constant, aside from a residual trend of becoming shallower towards $z=0$. We also compare to a statistical sample of ETGs at different redshifts, selected based on their luminosity profiles and stellar ma…
Samples of early-type galaxies show a correlation between stellar velocity dispersion and the stellar initial mass function (IMF) as inferred from gravity-sensitive absorption lines in the galaxies' central regions. To search for spatial variations in the IMF, we have observed two early-type galaxies with Keck/LRIS and measured radial gradients in the strengths of absorption features from 4000-5500 Å$\,$ and 8000-10,000 Å. We present spatially resolved measurements of the dwarf-sensitive spectral indices NaI (8190 Å) and Wing-Ford FeH (9915 Å), as well as indices for species of H, C$_2$, CN, M…
This paper is based on the multi-band (ugri) Fornax Deep Survey (FDS) with the VLT Survey Telescope (VST). We study bright early-type galaxies (m_B<15 mag) in the 9 square degrees around the core of the Fornax cluster, which covers the virial radius. The main goal of the present work is to provide the analysis of the light distribution for all galaxies out to unprecedented limits (in radius and surface brightness) and to release the main products resulting from this analysis in all FDS bands. From the isophote fit, we derive the azimuthally averaged surface brightness profiles, the position an…
The heavyweight stellar initial mass function (IMF) observed in the cores of massive early-type galaxies (ETGs) has been linked to formation of their cores in an initial swiftly-quenched rapid starburst. However, the outskirts of ETGs are thought to be assembled via the slow accumulation of smaller systems in which the star formation is less extreme; this suggests the form of the IMF should exhibit a radial trend in ETGs. Here we report radial stellar population gradients out to the half-light radii of a sample of eight nearby ETGs. Spatially resolved spectroscopy at 0.8-1.35μm from the VLT's …
Galaxy mergers are instrumental in dictating the final mass, structure, stellar populations, and kinematics of galaxies. Cosmological galaxy simulations indicate that the most massive galaxies at z=0 are dominated by high fractions of `ex-situ' stars, which formed first in distinct independent galaxies, and then subsequently merged into the host galaxy. Using spatially resolved MUSE spectroscopy we quantify and map the ex-situ stars in thirteen massive Early Type galaxies. We use full spectral fitting together with semi-analytic galaxy evolution models to isolate the signatures in the galaxies…
On dwarf galaxy scales, the different shapes of the galaxy stellar mass function and the dark halo mass function require a star-formation efficiency (SFE) in these systems that is currently more than 1 dex lower than that of Milky Way-size halos. Here, we argue that this trend may actually be reversed at high redshift. Specifically, by combining the resolved star-formation histories of nearby isolated dwarfs with the simulated mass-growth rates of dark matter halos, we show that the assembly of these systems occurs in two phases: (1) an early, fast halo accretion phase with a rapidly deepening…
In the quest to understand high-mass star formation, it is necessary to understand that from which the high-mass stars will form -- the dense molecular gas clouds and clumps. The Herschel infrared GALactic plane survey (Hi-GAL) is a comprehensive survey of thermal dust emission that can be used to characterize the properties and Galactic distribution of molecular gas. We have analyzed the survey maps within the Galactic longitude range $10^\circ < \ell < 56^\circ$ and have transformed these 2D maps into a 3D dense gas map of the Galactic plane using distance probability density functions. This…
The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted CCDs with little or no fringing it has recently become possible to obtain accurate measurements of these features. Here we present spectra covering the wavelength ranges 0.35 - 0.55 micron and 0.72 - 1.03 micron for the bulge of M31 and 34 early-type galaxies from the SAURON sample, obtained with the Low Resolution Imaging Spectrometer on Keck. The signal-t…
We detail an innovative new technique for measuring the 2-D velocity moments (rotation velocity, velocity dispersion and Gauss-Hermite coefficients h$_3$ and h$_4$) of the stellar populations of galaxy halos using spectra from Keck DEIMOS multi-object spectroscopic observations. The data are used to reconstruct 2-D rotation velocity maps. Here we present data for five nearby early-type galaxies to ~3 effective radii. We provide significant insights into the global kinematic structure of these galaxies, and challenge the accepted morphological classification in several cases. We show that betwe…
Based on 58 SLACS strong-lens early-type galaxies with direct total-mass and stellar-velocity dispersion measurements, we find that inside one effective radius massive elliptical galaxies with M_eff >= 3x10^10 M_sun are well-approximated by a power-law ellipsoid with an average logaritmic density slope of <gamma'_LD> = -dlog(rho_tot)/dlog(r)=2.085^{+0.025}_{-0.018} (random error on mean) for isotropic orbits with beta_r=0, +-0.1 (syst.) and sigma_gamma' <= 0.20^{+0.04}_{-0.02} intrinsic scatter (all errors indicate the 68 percent CL). We find no correlation of gamma'_LD with galaxy mass (M_eff…
The iron composition of globular clusters (GCs) is homogeneous in all but a few massive clusters, despite the presence of multiple stellar populations. Hence, most if not all the supernovae (SN) ejecta was not used to form stars. Here by means of semi-analytic and numerical studies we address this issue considering both stellar winds and supernovae feedback during the early evolution of proto-globular clusters. We calculate the ability of stellar winds to form a global wind that removes the gas left over from star formation. The innermost radius from which such a global wind can be formed, the…
We study the internal radial gradients of the stellar populations in a sample comprising 522 early-type galaxies (ETGs) from the SAMI (Sydney- AAO Multi-object Integral field spectrograph) Galaxy Survey. We stack the spectra of individual spaxels in radial bins, and derive basic stellar population properties: total metallicity ([Z/H]), [Mg/Fe], [C/Fe] and age. The radial gradient ($\nabla$) and central value of the fits (evaluated at R$_e$/4) are compared against a set of six possible drivers of the trends. We find that velocity dispersion ($σ$) - or, equivalently gravitational potential - is …
In this second paper of a series, we explore the B-V, U-B, and FUV-NUV radial color trends from a multi-wavelength sample of 141 dwarf disk galaxies. Like spirals, dwarf galaxies have three types of radial surface brightness profiles: (I) single exponential throughout the observed extent (the minority), (II) down-bending (the majority), and (III) up-bending. We find that colors of (1) Type I dwarfs generally become redder with increasing radius unlike spirals that have a blueing trend that flattens beyond ~1.5 disk scale lengths, (2) Type II dwarfs come in six different "flavors," one of which…
Stellar population parameters correlate with a range of galaxy properties, but it is unclear which relations are causal and which are the result of another underlying trend. In this series, we quantitatively compare trends between stellar population properties and galaxy structural parameters in order to determine which relations are intrinsically tighter, and are therefore more likely to reflect a causal relation. Specifically, we focus on the galaxy structural parameters of mass $M$, gravitational potential $Φ\sim M/R_e$, and surface mass density $Σ\sim M/R_e^2$. In Barone et al. (2018) we f…
We report a tight linear relation between the HI circular velocity measured at 6 $R_{\rm e}$ and the stellar velocity dispersion measured within 1 $R_{\rm e}$ for a sample of 16 early-type galaxies with stellar mass between $10^{10}$ and $10^{11}$ $\mathrm{M}_\odot$. The key difference from previous studies is that we only use spatially resolved $v_\mathrm{circ}$(HI) measurements obtained at large radius for a sizeable sample of objects. We can therefore link a kinematical tracer of the gravitational potential in the dark-matter dominated outer regions of galaxies with one in the inner regions…
We present analysis of 63 nearby ($<$ 44 Mpc) early-type galaxies hosting nuclear star clusters using the recently discovered parameter Central Intensity Ratio (CIR$_I$) determined from near-infra-red (3.6 $μ$m) observations with the Infra-red-array-camera of \emph{Spitzer} space telescope. The CIR$_I$, when combined with filters involving age and $B-K$ colour of host galaxies, helps identify two distinct classes of galaxies hosting nuclear star clusters. This is independently verified using Gaussian Mixture Model. CIR shows a positive trend with faint, low mass, and blue galaxies in the sampl…
We investigate mass segregation in group and cluster environments by identifying galaxy analogues in high-resolution dark matter simulations. Subhalos identified by the AHF and ROCKSTAR halo finders have similar mass functions, independent of resolution, but different radial distributions due to significantly different subhalo hierarchies. We propose a simple way to classify subhalos as galaxy analogues. The radial distributions of galaxy analogues agree well at large halo-centric radii for both AHF and ROCKSTAR but disagree near parent halo centres where the phase-space information used by RO…
The formation of protoplanetary discs during the collapse of molecular dense cores is significantly influenced by angular momentum transport, notably by the magnetic torque. In turn, the evolution of the magnetic field is determined by dynamical processes and non-ideal MHD effects such as ambipolar diffusion. Considering simple relations between various timescales characteristic of the magnetized collapse, we derive an expression for the early disc radius, $ r \simeq 18 \, {\rm AU} \, \left({η_{\rm AD} / 0.1 \, {\rm s}} \right)^{2/9} \left({B_z / 0.1\, {\rm G}} \right) ^{-4/9} \left({M / 0.1 \…
We study the distribution of projected ellipticity n(epsilon) for galaxies in a sample of 20 rich (Richness >= 2) nearby (z < 0.1) clusters of galaxies. We find no evidence of differences in n(epsilon), although the nearest cluster in the sample (the Coma Cluster) is the largest outlier (P(same) < 0.05). We then study n(epsilon) within the clusters, and find that epsilon increases with projected cluster-centric radius R (hereafter the epsilon-R relation). This trend is preserved at fixed magnitude, showing that this relation exists over and above the trend of more luminous galaxies to be both …
We have analyzed the parallelism between the properties of galaxy clusters and early-type galaxies (ETGs) by looking at the similarity between their light profiles. We find that the equivalent luminosity profiles of all these systems in the \vfilt\ band, once normalized to the effective radius \re\ and shifted in surface brightness, can be fitted by the Sérsic's law \Sers\ and superposed with a small scatter ($\le0.3$ mag). By grouping objects in different classes of luminosity, the average profile of each class slightly deviates from the other only in the inner and outer regions (outside $0.1…
The well-established correlations between the mass of a galaxy and the properties of its stars are considered evidence for mass driving the evolution of the stellar population. However, for early-type galaxies (ETGs), we find that $g-i$ color and stellar metallicity [Z/H] correlate more strongly with gravitational potential $Φ$ than with mass $M$, whereas stellar population age correlates best with surface density $Σ$. Specifically, for our sample of 625 ETGs with integral-field spectroscopy from the SAMI Galaxy Survey, compared to correlations with mass, the color--$Φ$, [Z/H]--$Φ$, and age--$…
We have derived high-spatial-resolution metallicity maps covering $\sim$105~deg$^2$ across the Large Magellanic Cloud (LMC) using near-infrared passbands from the VISTA Survey of the Magellanic Clouds. We attempt to understand the metallicity distribution and gradients of the LMC up to a radius of $\sim$ 6~kpc. We identify red giant branch (RGB) stars in spatially distinct $Y, (Y-K_{\rm s})$ colour-magnitude diagrams. In any of our selected subregions, the RGB slope is used as an indicator of the average metallicity, based on calibration to metallicity using spectroscopic data. The mean LMC me…
We use color gradients to explore the evolution of early-type galaxies in the core of the massive galaxy cluster MACS J1206.2-0847 at z = 0.44. We used data from the CLASH and CLASH-VLT surveys to perform multiwavelength optimized model fitting using Galapagos-2 from the MegaMorph project to measure their photometric parameters. We derive color gradients for $g_{475} - I_{814}$, $r_{625} - Y_{105}$, $I_{814} - H_{160}$ , and $Y_{105} - H_{160}$ at radii ranging between 0.1 - 2 $r_e$ for 79 early-type cluster galaxies. From synthetic spectral models that use simple star formation recipes, we in…
The central dark-matter fraction of galaxies is sensitive to feedback processes during galaxy formation. Strong gravitational lensing has been effective in the precise measurement of the dark-matter fraction inside massive early-type galaxies. Here, we compare the projected dark-matter fraction of early-type galaxies inferred from the SLACS strong-lens survey, with those obtained from the EAGLE, Illustris, and IllustrisTNG hydro-dynamical simulations. Previous comparisons with some simulations revealed a large discrepancy, with considerably higher inferred dark-matter fractions -- by factors 2…
We present radial gas-phase metallicity profiles, gradients, and break radii at redshift $z = 0 - 3$ from the TNG50-1 star-forming galaxy population. These metallicity profiles are characterized by an emphasis on identifying the steep inner gradient and flat outer gradient. From this, the break radius, $r_{\rm Break}$, is defined as the region where the transition occurs. We observe the break radius having a positive trend with mass that weakens with redshift. When normalized by the stellar half-mass radius, the break radius has a weaker relation with both mass and redshift. To test if our res…
It is not well understood whether the growth of early-type cluster galaxies proceeds inside-out, outside-in, or at the same pace at all radii. In this work we measured the galaxy size, defined by the radius including 80\% of the galaxy light, non-parametrically. We also determined a non-parametric estimate of galaxy light concentration, which measures the curvature of the surface brightness profile in the galaxy outskirts. We used an almost random sampling of a mass-limited sample formed by 128 morphologically early-type galaxies in clusters with $\log M/M_{\odot} \ga 10.7$ spanning the wide r…
The globular cluster systems of galaxies are well-known to extend to large galactocentric radii. Here we quantify the size of GC systems using the half number radius of 22 GC systems around early-type galaxies from the literature. We compare GC system sizes to the sizes and masses of their host galaxies. We find that GC systems typically extend to 4$\times$ that of the host galaxy size, however this factor varies with galaxy stellar mass from about 3$\times$ for M$^{\ast}$ galaxies to 5$\times$ for the most massive galaxies in the universe. The size of a GC system scales approximately linearly…
We present evidence from cosmological hydrodynamical simulations for a co-evolution of the slope of the total (dark and stellar) mass density profile, gamma_tot, and the dark matter fraction within the half-mass radius, f_DM, in early-type galaxies. The relation can be described as gamma_tot = A f_DM + B for all systems at all redshifts. The trend is set by the decreasing importance of gas dissipation towards lower redshifts and for more massive systems. Early-type galaxies are smaller, more concentrated, have lower f_DM and steeper gamma_tot at high redshifts and at lower masses for a given r…
The stellar velocity dispersion as a function of the galactocentric radius of an early-type galaxy can generally be well approximated by a power law $σ\propto r^β$. However, some observed dispersion profiles show a deviation from this fit at intermediate radii, usually between one and three $R_{\mathrm{eff}}$, where the velocity dispersion remains constant with radius, showing a bump-like behavior, which we term the "$σ$-"bump. To understand the origin of this $σ$-bump, we study a set of simulated early-type galaxies formed in major mergers. We find the $σ$-bump in all of our simulated early-t…
We present the first complete CO J=3-2 map of the nearby grand-design spiral galaxy M51 (NGC 5194), at a spatial resolution of ~600 pc, obtained with the HARP-B instrument on the James Clerk Maxwell Telescope. The map covers the entire optical galaxy disk and out to the companion NGC 5195, with CO J=3-2 emission detected over an area of ~9'x6' (~21x14 kpc). We describe the CO J=3-2 integrated intensity map and combine our results with maps of CO J=2-1, CO J=1-0 and other data from the literature to investigate the variation of the molecular gas, atomic gas and polycyclic aromatic hydrocarbon (…
Here we present the colours of individual globular clusters (GCs) around the massive elliptical galaxy NGC 1407 out to a projected galactocentric radius of 140 kpc or 17 galaxy effective radii (R$_e$). Such data are a proxy for the halo metallicity. We find steep, and similar, metallicity gradients of ~ -0.4 dex per dex for both the blue (metal-poor) and red (metal-rich) GC subpopulations within 5-8.5 R_e (40-70 kpc). At larger radii the mean GC colours (metallicity) are constant. A similar behaviour is seen in a wide-field study of M87's GC system, and in our own Galaxy. We interpret these ra…
We explore the variation in stellar population ages for Coma cluster galaxies as a function of projected cluster-centric distance, using a sample of 362 red-sequence galaxies with high signal-to-noise spectroscopy. The sample spans a wide range in luminosity (0.02-4 L*) and extends from the cluster core to near the virial radius. We find a clear distinction in the observed trends of the giant and dwarf galaxies. The ages of red-sequence giants are primarily determined by galaxy mass, with only weak modulation by environment, in the sense that galaxies at larger cluster-centric distance are sli…
High resolution 2D hydrodynamical simulations describing the evolution of the hot ISM in axisymmetric two-component models of early-type galaxies well reproduced the observed trends of the X-ray luminosity ($L_\mathrm{x}$) and temperature ($T_\mathrm{x}$) with galaxy shape and rotation, however they also revealed the formation of an exceedingly massive cooled gas disc in rotating systems. In a follow-up of this study, here we investigate the effects of star formation in the disc, including the consequent injection of mass, momentum and energy in the pre-existing interstellar medium. It is foun…
Sizes of galaxies are an important diagnostic for galaxy formation models. In this study I use the abundance matching ansatz, which has proven to be successful in reproducing galaxy clustering and other statistics, to derive estimates of the virial radius, R200, for galaxies of different morphological types and wide range of stellar mass. I show that over eight of orders of magnitude in stellar mass galaxies of all morphological types follow an approximately linear relation between 3D half-mass radius of their stellar distribution, rhalf and virial radius, rhalf~0.015R200 with a scatter of ~0.…
The hypothesis of a universal initial mass function (IMF) -- motivated by observations in nearby stellar systems -- has been recently challenged by the discovery of a systematic variation of the IMF with the central velocity dispersion, σ, of early-type galaxies (ETGs), towards an excess of low-mass stars in high-σ galaxies. This trend has been derived so far from integrated spectra, and remains unexplained at present. To test whether such trend depends on the local properties within a galaxy, we have obtained new, extremely deep, spectroscopic data, for three nearby ETGs, two galaxies with hi…
We analyze $Chandra$ observations of the hot atmospheres of 40 early spiral and elliptical galaxies. Using new temperature, density, cooling time, and mass profiles, we explore relationships between their hot atmospheres and cold molecular gas. Molecular gas mass correlates with atmospheric gas mass and density over four decades from central galaxies in clusters to normal giant ellipticals and early spirals. The mass and density relations follow power laws: $M_{\rm mol} \propto M_{\rm X}^{1.4\pm0.1}$ and $M_{\rm mol} \propto n_{\rm e}^{1.8\pm0.3}$, respectively, at 10 kpc. The ratio of molecul…
We have run direct N-body simulations to investigate the impact of stellar evolution and dynamics on the structural properties of young massive (3x10^4 solar masses) star clusters (SCs) with different metallicities (Z=1, 0.1, 0.01 solar metallicity). Metallicity drives the mass loss by stellar winds and supernovae (SNe), with SCs losing more mass at high metallicity. We have simulated three sets of initial conditions, with different initial relaxation timescale. We find that the evolution of the half-mass radius of SCs depends on how fast two-body relaxation is with respect to the lifetime of …
