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 for all early-types, grouped in bins of increasing local and global {$σ$}, as well as the second velocity moment $V_{rms}$, indicating a common inside-out formation pattern. We then place our dEs on the [Mg/Fe] $vs.$ [Fe/H] diagram of Local Group galaxies and show that dEs occupy the same region and show a similar trend line slope in the diagram as the high-metallicity stars of the Milky Way and the Large Magellanic Cloud. This finding extends the similar trend found for dwarf spheroidal $vs.$ dwarf irregular galaxies and supports the notion that dEs have evolved from late-type galaxies that have lost their gas at a point of their evolution, which likely coincided with them entering denser environments.
Surface abundances of C, N, and O in red giants are affected by processed material mixed into the stars' convective envelopes. Using a sample of $\sim 5100$ stars with elemental abundances from APOGEE and asteroseismic masses from {\it Kepler}, we test theoretical stellar models that predict this mixing, then apply these models to derive birth C, N, and O abundances for these stars. Our models with standard mixing can reproduce the observed trends to within plausible uncertainties in the birth abundances. Some models with ''extra'' mixing processes fail, predicting trends with surface gravity …
Context. Recent observations of the Bulge, e.g., its X-shape, cylindrical stellar motions, and a potential fraction of young stars propose that it formed through secular evolution of the disk and not through gas dissipation and/or mergers, as thought previously. Aims. We measure abundances of six iron-peak elements (Sc, V, Cr, Mn, Co and Ni) in the local thin and thick disks as well as the Bulge to provide additional observational constraints for Galaxy formation and chemical evolution models. Methods. We use high-resolution optical spectra of 291 K giants in the local disk mostly obtained by …
Observations show an almost ubiquitous presence of extra mixing in low-mass upper giant branch stars. The most commonly invoked explanation for this is thermohaline mixing. One-dimensional stellar evolution models include various prescriptions for thermohaline mixing, but the use of observational data directly to discriminate between thermohaline prescriptions has thus far been limited. Here, we propose a new framework to facilitate direct comparison: Using carbon-to-nitrogen measurements from the SDSS-IV APOGEE survey as a probe of mixing and a fluid parameter known as the reduced density rat…
Context. The formation and evolution of the Milky Way bulge is still largely an unanswered question. One of the most essential observables needed in its modelling are the metallicity distribution and the trends of the alpha elements as measured in stars. While Bulge regions beyond R > 50 pc of the centre has been targeted in several surveys, the central part has escaped detailed study due to the extreme extinction and crowding. The abundance gradients from the center are, however, of large diagnostic value. Aims. We aim at investigating the Galactic Centre environment by probing M giants in th…
We present [C/N]-[Fe/H] abundance trends from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey, Data Release 14 (DR14), for red giant branch stars across the Milky Way Galaxy (MW, 3 kpc $<$ R $<$ 15 kpc). The carbon-to-nitrogen ratio (often expressed as [C/N]) can indicate the mass of a red giant star, from which an age can be inferred. Using masses and ages derived by Martig et al., we demonstrate that we are able to interpret the DR14 [C/N]-[Fe/H] abundance distributions as trends in age-[Fe/H] space. Our results show that an anti-correlation between age and…
In the age of high-resolution spectroscopic stellar surveys of the Milky Way, the number of stars with detailed abundances of multiple elements is rapidly increasing. These elemental abundances are directly influenced by the evolutionary history of the Galaxy, but this can be difficult to interpret without an absolute timeline of the abundance enrichment. We present age-abundance trends for [M/H], [α/M], and 17 individual elements using a sample of 721 solar neighbourhood Hipparcos red giant stars observed by APOGEE. These age trends are determined through a Bayesian hierarchical modelling met…
The relaxation time at the half-mass radius of Galactic globular clusters (GGCs) is typically within a few Gyr. Hence, the majority of GGCs are expected to be well relaxed systems, given their age is around 12-13 Gyr. So any initial radial segregation between stars of the same initial mass on the main sequence (MS), in particular, the progenitors of the present day sub-giant and red-giant branch (SGB, RGB) stars should already have dissipated. However, a body of evidence contradicting to these expectations has been accumulated to date. The paradox could be solved by taking into account the eff…
In this paper, we aim to derive high-precision alpha-element abundances using CRIRES high-resolution IR spectra of 72 cool M giants of the inner Galactic bulge. Silicon, magnesium, and calcium abundances were determined by fitting a synthetic spectrum for each star. We also incorporated recent theoretical data into our spectroscopic analysis (i.e. updated K-band line list, better broadening parameter estimation, non-local thermodynamic equilibrium (NLTE) corrections). We compare these inner bulge alpha abundance trends with those of solar neighbourhood stars observed with IGRINS using the same…
The elemental abundance structure of the Galactic disc has been extensively studied in the solar neighbourhood using long-lived stars such as F and G dwarfs or K and M giants. These are stars whose atmospheres preserve the chemical composition of their natal gas clouds, and are hence excellent tracers of the chemical evolution of the Galaxy. As far as we are aware, there are no such studies of the inner Galactic disc, which hampers our ability to constrain and trace the origin and evolution of the Milky Way. Therefore, we aim in this study to establish the elemental abundance trend(s) of the d…
We examine the radial distributions of stellar populations in the globular cluster (GC) M15, using HST/WFC3 photometry of red giants in the nitrogen-sensitive F343N-F555W color. Surprisingly, we find that giants with "primordial" composition (i.e., N abundances similar to those in field stars) are the most centrally concentrated within the WFC3 field. We then combine our WFC3 data with SDSS u, g photometry and find that the trend reverses for radii >1' (3 pc) where the ratio of primordial to N-enhanced giants increases outwards, as already found by Lardo et al. The ratio of primordial to enric…
The abundance ratios [Y$/$Mg], [Y$/$Al], [Y$/$Si], [Y$/$Ca], and [Y$/$Ti] have been suggested as chemical clocks for solar-metallicity dwarf stars in the field as well as for giant stars in open clusters. To verify this last hypothesis, we derive these abundances ratios of 50 giant stars belonging to seven open clusters. To calculate the abundances, we analyze FEROS spectra assuming the LTE-hypothesis. We confirm that [Y$/$Mg], [Y$/$Al], [Y$/$Si], [Y$/$Ca], and [Y$/$Ti] work as chemical clocks for field dwarf stars at the local region (d $<$ 1 kpc) whereas for the field giants the [Y$/$Mg], [Y…
We study the morphology of the radio emission of giant radio galaxies (GRGs), a rare type of active galaxies, in order to find new clues for the reasons of their large size. Using radio images from two sky surveys at 1.4 GHz we quantified their radio morphology by measuring the geometry (armlength, bending angle, etc.) and flux symmetry for 58 such objects. Preliminary analysis suggests that radio source symmetry does not differ between galaxies and quasars, that there is no evidence for a decrease in linear size with redshift, and only a marginal trend for increasing symmetry with larger size…
We further study the unusual trend we found at statistically significant levels in some globular clusters, including NGC 3201: a decreasing iron abundance in red giants towards the cluster centers. We first show that recently published new estimates of iron abundance in the cluster reproduce this trend, in spite of the authors' statement about no metallicity spread due to a low scatter achieved in the [FeII/H] ratio. The mean of [FeII/H] within $R \sim 2'$ from the cluster center is lower, by $Δ$[FeII/H] = 0.05$\pm$0.02 dex, than in the outer region, in agreement with our original estimate for…
Determining elemental abundances of bulge stars can, via chemical evolution modeling, help to understand the formation and evolution of the bulge. Recently there have been claims both for and against the bulge having a different [$α$/Fe] vs. [Fe/H]-trend as compared to the local thick disk possibly meaning a faster, or at least different, formation time scale of the bulge as compared to the local thick disk. We aim to determine the abundances of oxygen, magnesium, calcium, and titanium in a sample of 46 bulge K-giants, 35 of which have been analyzed for oxygen and magnesium in previous works, …
Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ~ 1.5--2.0 Msun. The surface aluminium abundance should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of the Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to quite different predictions for the behavior of [Na/Fe] and [Al/Fe] versus [Fe/H]. Overall, the observed trends of these abundances with metallicity are not well reproduced. We readd…
Globular cluster (GC) systems around galaxies of a vast mass range show remarkably simple scaling relations. The combined mass of all GCs is a constant fraction of the total galaxy mass and the mean metallicity and metallicity dispersion of the GC system scale up weakly with galaxy mass. The metallicity of massive, metal-poor ("blue") clusters increases with cluster mass, while that of metal-rich ("red") clusters does not. A significant age-metallicity relation emerges from analysis of resolved stellar populations in Galactic GCs and unresolved populations in nearby galaxies. Remarkably, all t…
The variable mass-loss in low-mass red giant stars: Chromospheric motion across stellar evolution in 47 Tuc
Universidad Andrés Bello（安德烈斯贝略大学）；European Southern Observatory（欧洲南方天文台）；Osservatorio Astronomico di Padova-INAF（帕多瓦天文台-意大利国家天体物理研究所）；Università degli Studi di Bologna（博洛尼亚大学）；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）
Tentative evidence that the properties of evolved stars with planets may be different from what we know for MS hosts has been recently reported. We aim to test whether evolved stars with planets show any chemical peculiarity that could be related to the planet formation process. We determine in a consistent way the metallicity and individual abundances of a large sample of evolved (subgiants and red giants) and MS stars with and without known planetary companions. No differences in the <[X/Fe]> vs. condensation temperature (Tc) slopes are found between the samples of planet and non-planet host…
Phosphorus (P) is considered to be one of the key elements for life, making it an important element to look for in the abundance analysis of spectra of stellar systems. Yet, there exists only a handful of spectroscopic studies to estimate the P abundances and investigate its trend across a range of metallicities. We have observed full HK band spectra at a spectral resolving power of R=45,000 with IGRINS instrument. Abundances are determined using SME in combination with 1D MARCS stellar atmosphere models. The investigated sample of stars have reliable stellar parameters estimated using optical…
I studied giant discy galaxies with optical radii more than 30 kpc. The comparison of these systems with discy galaxies of moderate sizes revealed that they tend to have higher rotation velocities, B-band luminosities, HI masses and dark-to-luminous mass ratios. The giant discs follow the trend $\log(M_{\rm HI})(R_{25})$ found for normal size galaxies. It indicates the absence of the peculiarities of evolution of star formation in these galaxies. The HI mass to luminosity ratio of giant galaxies appears not to differ from that of normal size galaxies, giving evidences in favor of similar star …
We obtain high resolution spectra of nine red giant branch stars in NGC 6681 and perform the first detailed abundance analysis of stars in this cluster. We confirm cluster membership for these stars based on consistent radial velocities of 214.5$\pm$3.7 km/s and find a mean [Fe/H] = -1.63$\pm$0.07 dex and [α/Fe] = 0.42$\pm$0.11 dex. Additionally, we confirm the existence of a Na-O anti-correlation in NGC 6681 and identify two populations of stars with unique abundance trends. With the use of HST photometry from Sarajedini et al. (2007) and Piotto et al. (2015) we are able to identify these two…
We present a detailed study of the composition of 20 M giants in the Galactic center with 15 of them confirmed to be in the Nuclear Star Cluster. As a control sample we have also observed 7 M giants in the Milky Way Disk with similar stellar parameters. All 27 stars are observed using the NIRSPEC spectograph on the KECK II telescope in the K-band at a resolving power of R=23,000. We report the first silicon abundance trends versus [Fe/H] for stars in the Galactic center. While finding a disk/bulge like trend at subsolar metallicities, we find that [Si/Fe] is enhanced at supersolar metallicitie…
The metallicity spread, or the metallicity trend along the evolutionary sequence of a globular cluster, is a rich source of information to help understand the cluster physics (e.g. multiple populations) and stellar physics (e.g. atomic diffusion). Low-resolution integral-field-unit spectroscopy in the optical with the MUSE is an attractive prospect if it can provide these diagnostics because it allows us to extract spectra of a large fraction of the cluster stars. We investigate the possibilities of full-spectrum fitting to derive stellar parameters and chemical abundances at low spectral reso…
We present results from a study of seven large known head-tail radio galaxies based on observations using the Giant Metrewave Radio Telescope at 240 and 610 MHz. These observations are used to study the radio morphologies and distribution of the spectral indices across the sources. The overall morphology of the radio tails of these sources is suggestive of random motions of the optical host around the cluster potential. The presence of the multiple bends an d wiggles in several head-tail sources is possibly due to the precessing radio jets. We find steepening of the spectral index along the ra…
I summarize the results of 15 years of research on the surface abundances of stars in globular clusters. Globular-cluster stars afford a unique view of the physical processes that shape the surface abundances of stars on and beyond the Spite plateau, as one can study stars in different evolutionary phases with the same composition at birth. The main result is the finding of observational trends in surface abundances of heavy elements (Mg, Ca, Ti, Cr, Fe, Ba) that range from ~0.1 dex (M4 at [Fe/H]=-1.1) to ~0.3 dex (M30 at [Fe/H]=-2.3) with turn-off and subgiant stars generally showing lower ab…
The imprints of stellar nucleosynthesis and chemical evolution of the galaxy can be seen in different stellar populations, with older generation stars showing higher $α$-element abundances while the later generations becoming enriched with iron-peak elements. The evolutionary connections and chemical characteristics of circumstellar disks, stars, and their planetary companions can be inferred by studying the interdependence of planetary and host star properties. Numerous studies in the past have confirmed that high-mass giant planets are commonly found around metal-rich stars, while the stella…
