We investigate the origin of the evolution of the population-averaged size of quenched galaxies (QGs) through a spectroscopic analysis of their stellar ages. The two most favoured scenarios for this evolution are either the size growth of individual galaxies through a sequence of dry minor merger events, or the addition of larger, newly quenched galaxies to the pre-existing population (i.e., a progenitor bias effect). We use the 20k zCOSMOS-bright spectroscopic survey to select bona fide quiescent galaxies at 0.2<z<0.8. We stack their spectra in bins of redshift, stellar mass and size to compute stellar population parameters in these bins through fits to the rest-frame optical spectra and through Lick spectral indices. We confirm a change of behaviour in the size-age relation below and above the ~10^11 MSun stellar mass scale: In our 10.5 < log M*/MSun < 11 mass bin, over the entire redshift window, the stellar populations of the largest galaxies are systematically younger than those of the smaller counterparts, pointing at progenitor bias as the main driver of the observed average size evolution at sub-10^11 MSun masses. In contrast, at higher masses, there is no clear trend in age as a function of galaxy size, supporting a substantial role of dry mergers in increasing the sizes of these most massive QGs with cosmic time. Within the errors, the [alpha/Fe] abundance ratios of QGs are (i) above-solar over the entire redshift range of our analysis, hinting at universally short timescales for the buildup of the stellar populations of QGs, and (ii) similar at all masses and sizes, suggesting similar (short) timescales for the whole QG population and strengthening the role of mergers in the buildup of the most massive QGs in the Universe.
We analyze scaling relations and evolution histories of galaxy sizes in TNG100, part of the IllustrisTNG simulation suite. Observational qualitative trends of size with stellar mass, star-formation rate and redshift are reproduced, and a quantitative comparison of projected r-band sizes at 0~<z<~2 shows agreement to much better than 0.25dex. We follow populations of z=0 galaxies with a range of masses backwards in time along their main progenitor branches, distinguishing between main-sequence and quenched galaxies. Our main findings are as follows. (i) At M_{*,z=0}>~10^{9.5}Msun, the evolution…
We determine the ages of the young, resolved stellar populations at the locations of 237 optically-identified supernova remnants in M83. These age distributions put constraints on the progenitor masses of the supernovae that produced 199 of the remnants. The other 38 show no evidence for having a young progenitor and are therefore good Type Ia SNR candidates. Starting from Hubble Space Telescope broadband imaging, we measured resolved stellar photometry of seven archival WFC3/UVIS fields in F336W, F438W, and F814W. We generate color-magnitude diagrams of the stars within 50 pc of each SNR and …
In this Letter, using classified 197 supernovae (SNe) Ia, we perform an analyses of their height distributions from the disc in edge-on spirals and investigate their light-curve (LC) decline rates $(Δm_{15})$. We demonstrate, for the first time, that 91T- and 91bg-like subclasses of SNe Ia are distributed differently toward the plane of their host disc. The average height from the disc and its comparison with scales of thin/thick disc components gives a possibility to roughly estimate the SNe Ia progenitor ages: 91T-like events, being at the smallest heights, originate from relatively younger …
We address the nature and origin of Super Star Clusters (SSCs) discovered by Holtzman et al. (1992) within a radius of $\sim$$5\,\rm kpc$ from the center of NGC 1275, the giant elliptical galaxy at the center of the Perseus Cluster. We show that, in contrast with the much more numerous population of SSCs subsequently discovered up to $\sim$$30\,\rm kpc$ from the center of this galaxy, the central SSC population have maximal masses an order of magnitude higher and a mass function with a shallower power-law slope. Furthermore, whereas the outer SSC population have ages spanning a few $\rm Myr$ t…
We investigate the stellar population properties of a sample of 24 massive quenched galaxies at $1.25<z_\mathrm{spec}<2.09$ identified in the COSMOS field with our Subaru/MOIRCS near-IR spectroscopic observations. Tracing the stellar population properties as close to their major formation epoch as possible, we try to put constraints on the star formation history, post-quenching evolution, and possible progenitor star-forming populations for such massive quenched galaxies. By using a set of Lick absorption line indices on a rest-frame optical composite spectrum, the average age, metallicity [Z/…
We exploit the [Mg/Mn]-[Al/Fe] chemical abundance plane to help identify nearby halo stars in the 14th data release from the APOGEE survey that have been accreted on to the Milky Way. Applying a Gaussian Mixture Model, we find a `blob' of 856 likely accreted stars, with a low disc contamination rate of ~7%. Cross-matching the sample with the second data release from Gaia gives us access to parallaxes and apparent magnitudes, which place constraints on distances and intrinsic luminosities. Using a Bayesian isochrone pipeline, this enables us to estimate new ages for the accreted stars, with typ…
Using light curves and host galaxy spectra of 101 Type Ia supernovae (SNe Ia) with redshift $z \lesssim 0.3$ from the SDSS Supernova Survey (SDSS-SN), we derive the SN Ia rate as a function of progenitor age (the delay time distribution, or DTD). We use the VESPA stellar population synthesis algorithm to analyze the SDSS spectra of all galaxies in the field searched by SDSS-SN, giving us a reference sample of 77,000 galaxies for our SN Ia hosts. Our method does not assume any a priori shape for the DTD and therefore is minimally parametric. We present the DTD in physical units for high stretch…
Most massive passive galaxies are compact at high redshifts, but similarly compact massive galaxies are rare in the local universe. The most common interpretation of this phenomenon is that massive galaxies have grown in size by a factor of about five since redshift z=2. An alternative explanation is that recently quenched massive galaxies are larger (a "progenitor bias"). In this paper we explore the importance of progenitor bias by looking for systematic differences in the stellar populations of compact early-type galaxies in the DEEP2 survey as a function of size. Our analysis is based on a…
We age-date the stellar populations associated with 12 historic nearby core-collapse supernovae (CCSNe) and 2 supernova impostors, and from these ages, we infer their initial masses and associated uncertainties. To do this, we have obtained new HST imaging covering these CCSNe. Using these images, we measure resolved stellar photometry for the stars surrounding the locations of the SNe. We then fit the color-magnitude distributions of this photometry with stellar evolution models to determine the ages of any young existing populations present. From these age distributions, we infer the most li…
Massive stars are the main objects that illuminate H II regions and they evolve quickly to end their lives in core-collapse supernovae (CCSNe). Thus it is important to investigate the association between CCSNe and H II regions. In this paper, we present emission line diagnostics of the stellar populations around nearby CCSNe, that include their host H II regions, from the PMAS/PPAK Integral-field Supernova hosts COmpilation (PISCO). We then use BPASS stellar population models to determine the age, metallicity and gas parameters for H II regions associated with CCSNe, contrasting models that co…
We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters and in the field at 1<z<1.5 from the Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) survey. We determine the SFHs of individual galaxies by simultaneously fitting rest-frame optical spectroscopy and broadband photometry to stellar population models. We confirm that the SFHs are consistent with more massive galaxies having on average earlier formation times. Comparing galaxies found in massive clusters with those in the field, we find galaxies wi…
The Connection between Dusty Star-Forming Galaxies and the First Massive Quenched Galaxies
Cosmic Dawn Center (DAWN)（宇宙黎明中心）；DTU Space, Technical University of Denmark（丹麦技术大学空间科学部）；Departamento de Astronomia, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo（圣保罗大学天文学、地球物理学和大气科学研究所天文学系）；Jodrell Bank Centre for Astrophysics, University of Manchester（曼彻斯特大学乔德雷克银行天体物理学中心）；Centre for Astrophysics Research, University of Hertfordshire（赫特福德大学天体物理研究中心）；J.P. Morgan Securities LLC（摩根大通证券有限责任公司）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）
We analyze the stellar populations of a sample of 62 massive (log Mstar/Msun > 10.7) galaxies in the redshift range 1 < z < 1.6, with the main goal of investigating the role of recent quenching in the size growth of quiescent galaxies. We demonstrate that our sample is not biased toward bright, compact, or young galaxies, and thus is representative of the overall quiescent population. Our high signal-to-noise ratio Keck LRIS spectra probe the rest-frame Balmer break region which contains important absorption line diagnostics of recent star formation activity. We obtain improved measures of the…
We derive empirical models for galaxy mass assembly histories, and convolve these with theoretical delay time distribution (DTD) models for Type Ia supernovae (SNe Ia) to derive the distribution of progenitor ages for all SNe Ia occurring at a given epoch of cosmic time. In actively star-forming galaxies, the progression of the star formation rate is shallower than a $t^{-1}$ SN Ia DTD, so mean SN Ia ages peak at the DTD peak in all star-forming galaxies at all epochs of cosmic history. In passive galaxies which have ceased star formation through some quenching process, the SN Ia age distribut…
The study of cluster post starburst galaxies gives useful insights on the physical processes quenching the star formation in the most massive environments. Exploiting the MUSE data of the GAs Stripping Phenomena in galaxies (GASP) project, we characterise the quenching history of 8 local cluster galaxies that were selected for not showing emission lines in their fiber spectra. We inspect the integrated colors, the Hb rest frame equivalent widths (EW), star formation histories (SFHs) and luminosity-weighted age (LWA) maps finding no signs of current star formation throughout the disks of these …
We present an analysis of the galactocentric distributions of the "normal" and peculiar "91bg-like" subclasses of 109 supernovae (SNe) Ia, and study the global parameters of their elliptical hosts. The galactocentric distributions of the SN subclasses are consistent with each other, and with the radial light distribution of host stellar populations, when excluding bias against central SNe. Among the global parameters, only the distributions of u-r colours and ages are inconsistent significantly between the ellipticals of different SN Ia subclasses: the normal SN hosts are on average bluer/youn…
We report the serendipitous identification of a low mass ($M_* \sim 2\times 10^6 \, \mathrm{M}_\odot$), isolated, likely quenched dwarf galaxy in the "foreground" of the COSMOS-CANDELS field. From deep Hubble Space Telescope (HST) imaging we infer a surface brightness fluctuation distance for COSMOS-dw1 of $D_{\mathrm{SBF}} = 22 \pm 3$ Mpc, which is consistent with its radial velocity of $cz = 1222 \pm 64$ km s$^{-1}$ via Keck/LRIS. At this distance, the galaxy is 1.4 Mpc in projection from its nearest massive neighbor. We do not detect significant H$α$ emission (EW(H$α$)$ = -0.4 \pm 0.5$ angs…
SN1991bg-like supernovae are a distinct subclass of thermonuclear supernovae (SNe Ia). Their spectral and photometric peculiarities indicate their progenitors and explosion mechanism differ from `normal' SNe Ia. One method of determining information about supernova progenitors we cannot directly observe is to observe the stellar population adjacent to the apparent supernova explosion site to infer the distribution of stellar population ages and metallicities. We obtain integral field observations and analyse the spectra extracted from regions of projected radius $\sim\,\mathrm{kpc}$ about the …
Quenched galaxies at z>2 are nearly all very compact relative to z~0, suggesting a physical connection between high stellar density and efficient, rapid cessation of star-formation. We present restframe UV spectra of Lyman-break galaxies (LBGs) at z~3 selected to be candidate progenitors of quenched galaxies at z~2 based on their compact restframe optical sizes and high surface density of star-formation. We compare their UV properties to those of more extended LBGs of similar mass and star formation rate (non-candidates). We find that candidate progenitors have faster ISM gas velocities and hi…
The ages and metallicities of globular clusters (GCs) are known to be powerful tracers of the properties of their progenitor galaxies, enabling their use in determining the merger histories of galaxies. However, while useful in separating GCs into individual accretion events, the orbits of GC groups themselves have received less attention as probes of their progenitor galaxy properties. In this work, we use simulations of galaxies and their GC systems from the E-MOSAICS project to explore how the present-day orbital properties of GCs are related to the properties of their progenitor galaxies. …
We present an analysis of the light curve (LC) decline rates $(Δm_{15})$ of 407 normal and peculiar supernovae (SNe) Ia and global parameters of their host galaxies. As previously known, there is a significant correlation between the $Δm_{15}$ of normal SNe Ia and global ages (morphologies, colours, masses) of their hosts. On average, those normal SNe Ia that are in galaxies from the Red Sequence (early-type, massive, old hosts) have faster declining LCs in comparison with those from the Blue Cloud (late-type, less massive, younger hosts) of the colour-mass diagram. The observed correlations b…
We report on the detection of a small contribution (around and below 1% in mass) from young stellar components with ages $\leq$20 Myr in low-mass galaxies purposely selected from the MaNGA survey to be already-quenched systems. Among the sample of 28 galaxies, eight of them show signatures of having suffered a very recent burst of star formation. The detection has been done through the analysis of line-strength indices in the red spectral range [5700,8800] Å. The increasing contribution of red supergiants to this red regime is responsible for a deviation of the index measurements with respect …
The massive star origins for Type IIP supernovae (SNe) have been established through direct detection of their red supergiants progenitors in pre-explosion observations; however, there has been limited success in the detection of the progenitors of H-deficient SNe. The final fate of more massive stars, capable of undergoing a Wolf-Rayet phase, and the origins of Type Ibc SNe remains debated, including the relative importance of single massive star progenitors or lower mass stars stripped in binaries. We present an analysis of the ages and spatial distributions of massive stars around the sites…
Knowledge of ages for stars formed over a galaxy's lifetime is fundamental to understand its formation and evolution. However, stellar ages are difficult to obtain since they cannot be measured from observations, being comparison with stellar models (Soderblom 2010) required. Alternatively, age distributions can be derived applying the robust technique of colour-magnitude diagram fitting (Gallart et al. 2005), till now mainly employed to study nearby galaxies. The new distances to individual Milky Way stars from the Gaia mission (Brown et al. 2018) have allowed us to use this technique to deri…
We study the stellar content in the tidal tails of three nearby merging galaxies, NGC 520, NGC 2623, and NGC 3256, using BVI imaging taken with the Advanced Camera for Surveys on board the Hubble Space Telescope. The tidal tails in all three systems contain compact and fairly massive young star clusters, embedded in a sea of diffuse, unresolved stellar light. We compare the measured colors and luminosities with predictions from population synthesis models to estimate cluster ages and find that clusters began forming in tidal tails during or shortly after the formation of the tails themselves. …
We analyze the colors and sizes of 32 quiescent (UVJ-selected) galaxies with strong Balmer absorption ($\mbox{EW}(Hδ) \geq 4$Å) at $z\sim0.8$ drawn from DR2 of the LEGA-C survey to test the hypothesis that these galaxies experienced compact, central starbursts before quenching. These recently quenched galaxies, usually referred to as post-starburst galaxies, span a wide range of colors and we find a clear correlation between color and half-light radius, such that bluer galaxies are smaller. We build simple toy models to explain this correlation: a normal star-forming disk plus a central, compa…
We investigated the prospects for systematic searches of white dwarfs at low Galactic latitudes, using the VLT Survey Telescope (VST) H$α$ Photometric Survey of the Galactic plane and Bulge (VPHAS+). We targeted 17 white dwarf candidates along sightlines of known open clusters, aiming to identify potential cluster members. We confirmed all the 17 white dwarf candidates from blue/optical spectroscopy, and we suggest five of them to be likely cluster members. We estimated progenitor ages and masses for the candidate cluster members, and compared our findings to those for other cluster white dwar…
We directly compare predictions of dwarf galaxy properties in a semi-analytic model (SAM) with those extracted from a high-resolution hydrodynamic simulation. We focus on galaxies with halo masses of 1e9<Mvir/Msol<1e11 at high redshift ($z\ge5$). We find that, with the modifications previously proposed in Qin et al. (2018), including to suppress the halo mass and baryon fraction, as well as to modulate gas cooling and star formation efficiencies, the SAM can reproduce the cosmic evolution of galaxy properties predicted by the hydrodynamic simulation. These include the galaxy stellar mass funct…
Cluster Ages to Reconstruct the Milky Way Assembly (CARMA). V. The chronological merger tree of the Milky Way
Universidade de Vigo（维戈大学）；Universidad de La Laguna（拉古纳大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；Università degli Studi di Bologna（博洛尼亚大学）；INAF – Osservatorio Astronomico di Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）；INFN - Sezione di Pisa, Universitá di Pisa（意大利国家核物理研究所比萨分部，比萨大学）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）
Identifying stars found in the Milky Way as having formed in situ or accreted can be a complex and uncertain undertaking. We use Gaia kinematics and APOGEE elemental abundances to select stars belonging to the Gaia-Sausage-Enceladus (GSE) and Sequoia accretion events. These samples are used to characterize the GSE and Sequoia population metallicity distribution functions, elemental abundance patterns, age distributions, and progenitor masses. We find that the GSE population has a mean [Fe/H] $\sim -1.15$ and a mean age of $10-12$ Gyr. GSE has a single sequence in [Mg/Fe] vs [Fe/H] consistent w…
We search the Sloan Digital Sky Survey and the Baryon Oscillation Sky Survey to identify ~5500 massive compact quiescent galaxy candidates at 0.2<z<0.8. We robustly classify a subsample of 438 E+A galaxies based on their spectral properties and make this catalog publicly available. We examine sizes, stellar population ages and kinematics of galaxies in the sample and show that the physical properties of compact E+A galaxies suggest that they are a progenitor of massive compact quiescent galaxies. Thus, two classes of objects-compact E+A and compact quiescent galaxies-may be linked by a common …
Using observed stellar mass functions out to $z=5$, we measure the main progenitor stellar mass growth of descendant galaxies with masses of $\log{M_{*}/M_{\odot}}=11.5,11.0,10.5,10.0$ at $z\sim0.1$ using an evolving cumulative number density selection. From these mass growth histories, we are able to measure the time at which half the total stellar mass of the descendant galaxy was assembled, $t_{a}$, which, in order of decreasing mass corresponds to redshifts of $z_{a}=1.28, 0.92, 0.60$ and $0.51$. We compare this to the median light-weighted stellar age $t_{*}$ ($z_{*} = 2.08, 1.49, 0.82$ a…
We report the detection of morphology dependent stellar age in massive quenched galaxies (QGs) at z~1.2. The sense of the dependence is that compact QGs are 0.5-2 Gyr older than normal-sized ones. The evidence comes from three different age indicators, Dn4000, Hdelta and fits to spectral synthesis models, applied to their stacked optical spectra. All age indicators consistently show that the stellar populations of compact QGs are older than their normally-sized counterparts. We detect weak [OII] emission in a fraction of QGs, and the strength of the line, when present, is similar between the t…
Recent stellar population analysis of early-type galaxy spectra has demonstrated that the low-mass galaxies in cluster centers have high [$α/\rm Fe$] and old ages characteristic of massive galaxies and unlike the low-mass galaxy population in the outskirts of clusters and fields. This phenomenon has been termed "coordinated assembly" to highlight the fact that the building blocks of massive cluster central galaxies are drawn from a special subset of the overall low-mass galaxy population. Here we explore this idea in the IllustrisTNG simulations, particularly the TNG300 run, in order to unders…
We study the relationship between the morphology and star formation history (SFH) of 361 quiescent galaxies (QGs) at redshift $\langle z_{obs}\rangle\approx 2$, with stellar mass $\log M_*\ge10.3$, selected with the UVJ technique. Taking advantage of panchromatic photometry covering the rest-frame UV-to-NIR spectral range ($\approx40$ bands), we reconstruct the non-parametric SFH of the galaxies with the fully Bayesian SED fitting code Prospector. We find that the half-light radius $R_e$, observed at $z_{obs}$, depends on the formation redshift of the galaxies, $z_{form}$, and that this relati…
We investigate the stellar population properties of passive spiral galaxies in the CALIFA survey. Nine spiral galaxies that have NUV-r > 5 and no/weak nebular emission lines in their spectra are selected as passive spirals. Our passive spirals lie in the redshift range of 0.001 < z < 0.021 and have stellar mass range of 10.2 < log(M_{\star}/M_{\odot}) < 10.8. They clearly lie in the domain of early-type galaxies in the WISE IR color-color diagram. We analyze the stellar populations out to two effective radius, using the best-fitting model to the measured absorption line-strength indices in the…
Accurate models of the star formation histories (SFHs) of recently-quenched galaxies can provide constraints on when and how galaxies shut down their star formation. The recent development of "non-parametric" SFH models promises the flexibility required to make these measurements. However, model and prior choices significantly affect derived SFHs, particularly for post-starburst galaxies (PSBs) which have sharp changes in their recent SFH. In this paper, we create mock PSBs, then use the Prospector SED fitting software to test how well four different SFH models recover key properties. We find …
This paper reports an environmental analysis of 41 uniformly-selected stripped-envelope supernovae (SESNe) based on deep ultraviolet-optical images acquired by the Hubble Space Telescope. Young stellar populations are detected in most SN environments and their ages are derived with a hierarchical Bayesian approach. The age distributions are indistinguishable between Type IIb and Type Ib while that for Type Ic is systematically younger. This suggests that the Type Ic SN progenitors are more massive while the Type IIb and Type Ib SNe have very similar progenitor masses. Our result supports a hyb…
Massive quiescent galaxies (MQGs) are thought to have formed stars rapidly at early times followed by a long period of quiescence. The recent discovery of a MQG, ZF-COSMOS-20115 at $z\sim4$, only 1.5 Gyr after the big bang, places new constraints on galaxy growth and the role of feedback in early star formation. Spectroscopic follow-up confirmed ZF-COSMOS-20115 as a MQG at $z=3.717$ with an estimated stellar mass of ${\sim}10^{11}\mathrm{M}_\odot$, showing no evidence of recent star formation. We use the Meraxes semi-analytic model to investigate how ZF-COSMOS-20115 analogues build stellar mas…
To date, the question of which progenitor channel can reproduce the observed rate of Type Ia supernovae (SNe Ia) remains unresolved, with the single and double degenerate scenarios remaining the leading contenders. The former implies a large population of hot accreting white dwarfs with photospheric temperatures of T ~ 10^5-10^6 K during some part of their accretion history. We show that in early-type galaxies, a population of accreting white dwarfs large enough to reproduce the SN Ia rate would contribute significantly to the ionizing UV radiation expected from the stellar population. For mea…
In this work, we combine the semi-analytic model of galaxy formation and evolution SAG with the $102$ relaxed simulated galaxy clusters from The Three Hundred project, and we study the link between the quenching of star formation (SF) and the physical processes that galaxies experience through their dynamical history in and around clusters. We classify galaxies in four populations based on their orbital history: recent and ancient infallers, and backsplash and neighbouring galaxies. We find that $\sim 85$ per cent of the current population of quenched galaxies located inside the clusters are a…
Fundamental parameters and physical processes leading to the formation of white dwarfs (WDs) may be constrained and refined by discovering WDs in open clusters (OCs). Cluster membership can be utilized to establish the precise distances, luminosities, ages, and progenitor masses of such WDs. We compile a list of probable WDs that are OC members in order to facilitate WD studies that are impractical or difficult to conduct for Galactic field WDs. We use recent catalogs of WDs and OCs that are based on the second data release of the \textit{Gaia} satellite mission (GDR2) to identify WDs that are…
Surveys of the Milky Way (MW) and M31 enable detailed studies of stellar populations across ages and metallicities, with the goal of reconstructing formation histories across cosmic time. These surveys motivate key questions for galactic archaeology in a cosmological context: when did the main progenitor of a MW/M31-mass galaxy form, and what were the galactic building blocks that formed it? We investigate the formation times and progenitor galaxies of MW/M31-mass galaxies using the FIRE-2 cosmological simulations, including 6 isolated MW/M31-mass galaxies and 6 galaxies in Local Group (LG)-li…
SN 2002cx-like Type Ia supernovae (also known as SNe Iax) represent one of the most numerous peculiar SN classes. They differ from normal SNe Ia by having fainter peak magnitudes, faster decline rates and lower photospheric velocities, displaying a wide diversity in these properties. We present both integral-field and long-slit visual-wavelength spectroscopy of the host galaxies and explosion sites of SNe Iax to provide constraints on their progenitor formation scenarios. The SN Iax explosion site metallicity distribution is similar to that of core-collapse (CC) SNe and metal-poor compared to …
We present estimates of stellar age and mass for 0.93 million Galactic disk main sequence turn-off and sub-giant stars from the LAMOST Galactic Spectroscopic Surveys. The ages and masses are determined by matching with stellar isochrones using Bayesian algorithm, utilizing effective temperature $T_{\rm eff}$, absolute magnitude ${\rm M}_V$, metallicity [Fe/H] and $α$-element to iron abundance ratio [$α$/Fe] deduced from the LAMOST spectra. Extensive examinations suggest the age and mass estimates are robust. The overall sample stars have a median error of 34 per cent for the age estimates, and…
Massive early-type galaxies are believed to be the end result of an extended mass accretion history. The stars formed in situ very early on in the initial phase of the assembly might have originated from an extremely intense star formation burst, and may still be found within the cores of such galaxies today. We investigate the presence of a surviving high-$z$ compact progenitor component in the brightest galaxy of the Hydra I cluster, NGC 3311, by mapping its 2D kinematics and stellar population out to 2 effective radii, combining MUSE observations, extended EMILES models, and a newly develop…
