Natal Cloud Research Articles

The role of binaries in the enrichment of the early Galactic halo

The detailed composition of most metal-poor halo stars has been found to be very uniform. However, a fraction of 20-70% (increasing with decreasing metallicity) exhibit dramatic enhancements in their abundances of carbon - the so-called carbon-enhanced metal-poor (CEMP) stars. A key question for Galactic chemical evolution models is whether this non-standard composition reflects that of the stellar natal clouds, or is due to local, post-birth mass transfer of chemically processed material from a binary companion; CEMP stars should then all be members of binary systems. Our aim is to determine the frequency and orbital parameters of binaries among CEMP stars with and without over-abundances of neutron-capture elements - CEMP-s and CEMP-no stars, respectively - as a test of this local mass-transfer scenario. This paper discusses a sample of 24 CEMP-no stars, while a subsequent paper will consider a similar sample of CEMP-s stars. Most programme stars exhibit no statistically significant radial-velocit variation over this period and appear to be single, while four are found to be binaries with orbital periods of 300-2,000 days and normal eccentricity; the binary frequency for the sample is 17+-9%. The single stars mostly belong to the recently-identified ``low-C band'', while the binaries have higher absolute carbon abundances. We conclude that the nucleosynthetic process responsible for the strong carbon excess in these ancient stars is unrelated to their binary status; the carbon was imprinted on their natal molecular clouds in the early Galactic ISM by an even earlier, external source, strongly indicating that the CEMP-no stars are likely bona fide second-generation stars. We discuss potential production sites for carbon and its transfer across interstellar distances in the early ISM, and implications for the composition of high-redshift DLA systems. Abridged.

The role of binaries in the enrichment of the early Galactic halo

Context. The detailed chemical composition of most metal-poor halo stars has been found to be highly uniform, but a minority of stars exhibit dramatic enhancements in their abundances of heavy neutron-capture elements and/or of carbon. The key question for Galactic chemical evolution models is whether these peculiarities reflect the composition of the natal clouds, or if they are due to later (post-birth) mass transfer of chemically processed material from a binary companion. If the former case applies, the observed excess of certain elements was implanted within selected clouds in the early ISM from a production site at interstellar distances.

SD 1313–0019: ANOTHER SECOND-GENERATION STAR WITH [Fe/H] = −5.0, OBSERVED WITH THE MAGELLAN TELESCOPE

We present a Magellan/MIKE high-resolution (R ~ 35,000) spectrum of the ancient star SD 1313-0019 which has an iron abundance of [Fe/H] = -5.0, paired with a carbon enhancement of [C/Fe] ~ 3.0. The star was initially identified by Allende Prieto et al. in the BOSS survey. Its medium-resolution spectrum suggested a higher metallicity of [Fe/H] = -4.3 due to the CaII K line blending with a CH feature which is a common issue related to the search for the most iron-poor stars. This star joins several other, similar stars with [Fe/H] < -5.0 that all display a combination of low iron and high carbon abundances. Other elemental abundances of SD 1313-0019 follow that of more metal-rich halo stars. From fitting the abundance pattern with yields of Population III supernova, we conclude that SD 1313-0019 had only one massive progenitor star with 20 - 30 M_sun that must have undergone a mixing and fallback episode. Overall, there are now five stars known with [Fe/H] < -5.0 (1D LTE abundances). This population of second-generation stars strongly suggests massive first stars that almost exclusively produced large amounts of carbon through stellar winds and/or their mixing and fallback supernova explosions. As a consequence, their natal clouds -- presumably some early minihalo structures -- contained ample amounts of carbon and oxygen that likely facilitated the formation of these first low-mass stars.

Production and Recycling of Carbon in the Early Galactic Halo

AbstractA large fraction of extremely metal-poor halo stars are strongly enriched in carbon (CEMP stars). The standard scenario for their origin is mass transfer in binary systems, but this assumes that they are binaries. If not, the C must have been implanted in their natal clouds from a distant production site(s) in the preceding - possibly first - generation of stars. The binary population of CEMP subgroups can shed light on these processes.

Massive stars in the giant molecular cloud G23.3−0.3 and W41

Young massive stars and stellar clusters continuously form in the Galactic disk, generating new HII regions within their natal giant molecular clouds and subsequently enriching the interstellar medium via their winds and supernovae. Massive stars are among the brightest infrared stars in such regions; their identification permits the characterization of the star formation history of the associated cloud as well as constraining the location of stellar aggregates and hence their occurrence as a function of global environment. We present a stellar spectroscopic survey in the direction of the giant molecular cloud G23.3-0.3. This complex is located at a distance of ~ 4-5 kpc, and consists of several HII regions and supernova remnants. We discovered 11 OfK+ stars, one candidate Luminous Blue Variable, several OB stars, and candidate red supergiants. Stars with K-band extinction from ~1.3 - 1.9 mag appear to be associated with the GMC G23.3-0.3; O and B-types satisfying this criterion have spectro-photometric distances consistent with that of the giant molecular cloud. Combining near-IR spectroscopic and photometric data allowed us to characterize the multiple sites of star formation within it. The O-type stars have masses from 25 - 45 Msun, and ages of 5-8 Myr. Two new red supergiants were detected with interstellar extinction typical of the cloud; along with the two RSGs within the cluster GLIMPSE9, they trace an older burst with an age of 20--30 Myr. Massive stars were also detected in the core of three supernova remnants - W41, G22.7-0.2, and G22.7583-0.4917. A large population of massive stars appears associated with the GMC G23.3-0.3, with the properties inferred for them indicative of an extended history of stars formation.

Champagne flutes and brandy snifters: modelling protostellar outflow–cloud chemical interfaces

A rich variety of molecular species has now been observed towards hot cores in star forming regions and in the interstellar medium. An increasing body of evidence from millimetre interferometers suggests that many of these form at the interfaces between protostellar outflows and their natal molecular clouds. However, current models have remained unable to explain the origin of the observational bias towards wide-angled "brandy snifter" shaped outflows over narrower "champagne flute" shapes in carbon monoxide imaging. Furthermore, these wide-angled systems exhibit unusually high abundances of the molecular ion HCO$^+$. We present results from a chemo-dynamic model of such regions where a rich chemistry arises naturally as a result of turbulent mixing between cold, dense molecular gas and the hot, ionized outflow material. The injecta drives a rich and rapid ion-neutral chemistry in qualitative and quantitative agreement with the observations. The observational bias towards wide-angled outflows is explained naturally by the geometry-dependent ion injection rate causing rapid dissociation of CO in the younger systems.

THE MID-INFRARED APPEARANCE OF THE GALACTIC MINI-STARBURST W49A

The massive star forming region W49A represents one of the largest complexes of massive star formation present in the Milky Way and contains at least fifty young massive stars still enshrouded in their natal molecular cloud. We employ Spitzer/IRS spectral mapping observations of the northern part of W49A to investigate the mid-infrared (MIR) spatial appearance of the polycyclic aromatic hydrocarbon (PAH) bands, PAH plateau features, atomic lines and continuum emission. We examine the spatial variations of the MIR emission components in slices through two of the ultra compact-HII (UC-HII) regions. We find that the PAH bands reproduce known trends, with the caveat that the 6.2 $\mu$m PAH band seems to decouple from the other ionized PAH bands in some of the UC-HII regions -- an effect previously observed only in one other object: the giant star forming region N66 in the LMC. Furthermore, we compare the nature of the emission surrounding W49A to that of `diffuse' sightlines. It is found that the surrounding emission can be explained by line of sight emission, and does not represent true `diffuse' material. Additionally, we examine the MIR appearance of star formation on various scales from UC-HII regions to starburst galaxies, including a discussion of the fraction of PAH emission in the 8 $\mu$m IRAC filter. We find that the MIR appearance of W49A is that of a starburst on large scales yet its individual components are consistent with other galactic HII regions.

Radiation-pressure-driven dust waves inside bursting interstellar bubbles

Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form bubbles of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log(L/L_sun) < 5.2, form and expand due to the thermal pressure accompanying ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, demonstrating the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the ISM through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We create a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well-studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in UltraLuminous InfraRed Galaxies (ULIRGs), merging galaxies and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

BONDI-HOYLE ACCRETION IN AN ISOTHERMAL MAGNETIZED PLASMA

In regions of star formation, protostars and newborn stars accrete mass from their natal clouds. These clouds are threaded by magnetic fields with a strength characterized by the plasma beta---the ratio of thermal and magnetic pressures. Observations show molecular clouds have beta <= 1, so magnetic fields can play a significant role in the accretion process. We have carried out a numerical study of the effect of large-scale magnetic fields on the rate of accretion onto a uniformly moving point particle from a uniform, non-self-gravitating, isothermal gas. We consider gas moving with sonic Mach numbers of up M ~ 45, magnetic fields that are either parallel, perpendicular, or oriented 45 degrees to the flow, and beta as low as 0.01. Our simulations utilize AMR to obtain high spatial resolution where needed; this also allows the simulation boundaries to be far from the accreting object. Additionally, we show our results are independent of our exact prescription for accreting mass in the sink particle. We give simple expressions for the steady-state accretion rate as a function of beta, M, and field orientation. Using typical molecular clouds values of M ~ 5 and beta ~ 0.04 from the literature, our fits suggest a 0.4 M_Sun star accretes ~ 4*10^{-9} M_Sun/year, almost a factor of two less than accretion rates predicted by hydrodynamic models. This disparity grows to orders of magnitude for stronger fields and lower Mach numbers. We discuss the applicability of these accretion rates versus accretion rates expected from gravitational collapse, and when a steady state is possible. This reduction in Mdot increases the time required to form stars in competitive accretion models, making such models less efficient. In numerical codes, our results should enable accurate subgrid models of sink particles accreting from magnetized media.

The CHESS survey of the L1157-B1 bow-shock: high and low excitation water vapor

Molecular outflows powered by young protostars strongly affect the kinematics and chemistry of the natal molecular cloud through strong shocks resulting in substantial modifications of the abundance of several species. As part of the "Chemical Herschel Surveys of Star forming regions" guaranteed time key program, we aim at investigating the physical and chemical conditions of H20 in the brightest shock region B1 of the L1157 molecular outflow. We observed several ortho- and para-H2O transitions using HIFI and PACS instruments on board Herschel, providing a detailed picture of the kinematics and spatial distribution of the gas. We performed a LVG analysis to derive the physical conditions of H2O shocked material, and ultimately obtain its abundance. We detected 13 H2O lines probing a wide range of excitation conditions. PACS maps reveal that H2O traces weak and extended emission associated with the outflow identified also with HIFI in the o-H2O line at 556.9 GHz, and a compact (~10") bright, higher-excitation region. The LVG analysis of H2O lines in the bow-shock show the presence of two gas components with different excitation conditions: a warm (Tkin~200-300 K) and dense (n(H2)~(1-3)x10^6 cm-3) component with an assumed extent of 10" and a compact (~2"-5") and hot, tenuous (Tkin~900-1400 K, n(H2)~10^3-10^4 cm-3) gas component, which is needed to account for the line fluxes of high Eu transitions. The fractional abundance of the warm and hot H2O gas components is estimated to be (0.7-2)x10^{-6} and (1-3)x10^{-4}, respectively. Finally, we identified an additional component in absorption in the HIFI spectra of H2O lines connecting with the ground state level, probably arising from the photodesorption of icy mantles of a water-enriched layer at the edges of the cloud.

THE PARSEC-SCALE ENVIRONMENT AND THE EVOLUTIONARY STATUS OF MWC 349A

We report on a study of the ~10' (~5 pc in projection) environs of the peculiar, high-luminosity emission-line star MWC 349A in the IR, radio, and visible domains. Besides the recently discovered X-shaped, arcmin-scale IR nebula centered on MWC 349A (X nebula), with the kinematic age of ~104 yr, we identify several young objects pointing toward an ongoing process of active star formation in this region and estimate some physical parameters of the newly discovered objects. The radiation of the X nebula is due to a geometrically and optically thin dust front heated to Td 60-70 K by the radiation of the central star. The bipolar dust front probably results from the interaction of a powerful stellar wind with the circumstellar disk. One of the related objects is an elongated, cold molecular cloud, ~1 pc in size, adjacent to MWC 349A in projection and having the same radial velocity (V LSR +9 km s–1). The proximity of the molecular cloud may indicate that MWC 349A was born locally rather than being a runaway object ejected from the core of Cyg OB2 several Myr ago. If it is still associated with its natal cloud, MWC 349A may be a rare example of the observable pre-main-sequence stage of a ~30 M ☉ star. If the association with the molecular cloud is an effect of projection, however, MWC 349A may already be an evolved star, even if it was born locally. We discuss future observations that may shed more light on the evolutionary status of this unique object.

Giant molecular clouds: star factories of the galaxy

Stars are forming in our galaxy at a rate of between 1 and 4 solar masses of stars per year. In contrast to elliptical galaxies, which are largely devoid of star formation, star formation is still going on in spiral galaxies because of their reservoirs of molecular gas, the fuel for new stars. The discs of spiral galaxies are comprised not only of stars as we clearly see from Earth, but also gas (the interstellar medium, ISM). This is where this gas accumulates into cold, dense, molecular regions known as molecular clouds, in which new stars are formed. Most star formation occurs in massive molecular clouds, known as giant molecular clouds (GMCs). However, while we have a good understanding of how individual stars form, there is less consensus on how their natal clouds of gas accumulate, how long these clouds last, how star formation progresses over their lifetime, and indeed how star formation has progressed over the lifetime of the Milky Way.

CHEMICAL ANALYSIS OF THE NINTH MAGNITUDE CARBON-ENHANCED METAL-POOR STAR BD+44°493

We present detailed chemical abundances for the bright carbon-enhanced metal-poor (CEMP) star BD+44 493, previously reported on by Ito et al. Our measurements confirm that BD+44 493 is an extremely metal-poor ([Fe/H]=-3.8) subgiant star with excesses of carbon and oxygen. No significant excesses are found for nitrogen and neutron-capture elements (the latter of which place it in the CEMP-no class of stars). Other elements that we measure exhibit abundance patterns that are typical for non-CEMP extremely metal-poor stars. No evidence for variations of radial velocity have been found for this star. These results strongly suggest that the carbon enhancement in BD+44 493 is unlikely to have been produced by a companion asymptotic giant-branch star and transferred to the presently observed star, nor by pollution of its natal molecular cloud by rapidly-rotating, massive, mega metal-poor ([Fe/H] < -6.0) stars. A more likely possibility is that this star formed from gas polluted by the elements produced in a "faint" supernova, which underwent mixing and fallback, and only ejected small amounts of elements of metals beyond the lighter elements. The Li abundance of BD+44 493 (A(Li)=log(Li/H)+12=1.0) is lower than the Spite plateau value, as found in other metal-poor subgiants. The upper limit on Be abundance (A(Be)=log(Be/H)+12<-1.8) is as low as those found for stars with similarly extremely-low metallicity, indicating that the progenitors of carbon- (and oxygen-) enhanced stars are not significant sources of Be, or that Be is depleted in metal-poor subgiants with effective temperatures of ~5400K.

Candidate super star cluster progenitor gas clouds possibly triggered by close passage to Sgr A*

Abstract Super star clusters are the end product of star formation under the most extreme conditions. As such, studying how their final stellar populations are assembled from their natal progenitor gas clouds can provide strong constraints on star formation theories. An obvious place to look for the initial conditions of such extreme stellar clusters is gas clouds of comparable mass and density, with no star formation activity. We present a method to identify such progenitor gas clouds and demonstrate the technique for the gas in the inner few hundred pc of our Galaxy. The method highlights three clouds in the region with similar global physical properties to the previously identified extreme cloud, G0.253 + 0.016, as potential young massive cluster (YMC) precursors. The fact that four potential YMC progenitor clouds have been identified in the inner 100 pc of the Galaxy, but no clouds with similar properties have been found in the whole first quadrant despite extensive observational efforts, has implications for cluster formation/destruction rates across the Galaxy. We put forward a scenario to explain how such dense gas clouds can arise in the Galactic Centre environment, in which YMC formation is triggered by gas streams passing close to the minimum of the global Galactic gravitational potential at the location of the central supermassive black hole, Sgr A*. If this triggering mechanism can be verified, we can use the known time interval since closest approach to Sgr A* to study the physics of stellar mass assembly in an extreme environment as a function of absolute time.

Evolution of protostellar outflow around low-mass protostar

The evolution of protostellar outflow is investigated with resistive magneto-hydrodynamic nested-grid simulations that cover a wide range of spatial scales (\sim 1AU - 1pc). We follow cloud evolution from the pre-stellar core stage until the infalling envelope dissipates long after the protostar formation. We also calculate protostellar evolution to derive protostellar luminosity with time-dependent mass accretion through a circumstellar disk. The protostellar outflow is driven by the first core prior to protostar formation and is directly driven by the circumstellar disk after protostar formation. The opening angle of the outflow is large in the Class 0 stage. A large fraction of the cloud mass is ejected in this stage, which reduces the star formation efficiency to \sim 50%. After the outflow breaks out from the natal cloud, the outflow collimation is gradually improved in the Class I stage. The head of the outflow travels more than \sim 10^5AU in \sim 10^5 yr. The outflow momentum, energy and mass derived in our calculations agree well with observations. In addition, our simulations show the same correlations among outflow momentum flux, protostellar luminosity and envelope mass as those in observations. These correlations differ between Class 0 and I stages, which is explained by different evolutionary stages of the outflow; in the Class 0 stage, the outflow is powered by the accreting mass and acquires its momentum from the infalling envelope; in the Class I stage, the outflow enters the momentum-driven snow-plough phase. Our results suggest that protostellar outflow should determine the final stellar mass and significantly affect the early evolution of low-mass protostars.

THE SCHMIDT-KENNICUTT LAW OF MATCHED-AGE STAR-FORMING REGIONS; Paα OBSERVATIONS OF THE EARLY-PHASE INTERACTING GALAXY TAFFY I

In order to test a recent hypothesis that the dispersion in the Schmidt-Kennicutt law arises from variations in the evolutionary stage of star forming molecular clouds, we compared molecular gas and recent star formation in an early-phase merger galaxy pair, Taffy I (UGC\ 12915/UGC\ 12914, VV\ 254) which went through a direct collision 20 Myr ago and whose star forming regions are expected to have similar ages. Narrow-band Pa-alpha image is obtained using the ANIR near-infrared camera on the mini-TAO 1m telescope. The image enables us to derive accurate star formation rates within the galaxy directly. The total star formation rate, 22.2 M_sun/yr, was found to be much higher than previous estimates. Ages of individual star forming blobs estimated from equivalent widths indicate that most star forming regions are ~7 Myr old, except for a giant HII region at the bridge which is much younger. Comparison between star formation rates and molecular gas masses for the regions with the same age exhibits a surprisingly tight correlation, a slope of unity, and star formation efficiencies comparable to those of starburst galaxies. These results suggest that Taffy I has just evolved into a starburst system after the collision, and the star forming sites are at a similar stage in their evolution from natal molecular clouds except for the bridge region. The tight Schmidt-Kennicutt law supports the scenario that dispersion in the star formation law is in large part due to differences in evolutionary stage of star forming regions.

A 1 mm SPECTRAL LINE SURVEY TOWARD GLIMPSE EXTENDED GREEN OBJECTS (EGOs)

A northern subsample of 89 Spitzer GLIMPSE extended green objects (EGOs), the candidate massive young stellar objects, are surveyed for molecular lines in two 1-GHz ranges: 251.5- 252.5 and 260.188-261.188 GHz. A comprehensive catalog of observed molecular line data and spectral plots are presented. Eight molecular species are undoubtedly detected: H13CO+, SiO, SO, CH3OH, CH3OCH3, CH3CH2CN, HCOOCH3, and HN13C. H13CO+ 3-2 line is detected in 70 EGOs among which 37 ones also show SiO 6-5 line, demonstrating their association to dense gas and supporting the outflow interpretation of the extended 4.5 um excess emission. Our major dense gas and outflow tracers (H13CO+, SiO, SO and CH3OH) are combined with our previous survey of 13CO, 12CO and C18O 1-0 toward the same sample of EGOs for a multi-line multi- cloud analysis of line width and luminosity correlations. Good log-linear correlations are found among all considered line luminosities, which requires a universal similarity of density and thermal structures and probably of shock properties among all EGO clouds to explain. It also requires that the shocks should be produced within the natal clouds of the EGOs. Diverse degrees of correlation are found among the line widths. However, both the line width and luminosity correlations tend to progressively worsen across larger cloud subcomponent size-scales, depicting the increase of randomness across cloud subcomponent sizes. Moreover, the line width correlations among the three isotopic CO 1-0 lines show data scatter as linear functions of the line width itself, indicating that the velocity randomness also increases with whole-cloud sizes and has some regularity behind.

Similarity and randomness in the molecular clouds associated with Spitzer GLIMPSE Extended Green Objects (EGOs)

AbstractEGOs are candidates of massive star forming regions that show signatures of outflows. A 1.1mm line survey has been performed to 89 EGOs using the AROSMT. Our high detection rates of H13CO+ 3-2 and SiO 6-5 lines support EGOs to be dense clouds harboring outflows.Ubiquitous line luminosity linear correlations are found among different kinds of tracer lines: dense gas tracer H13CO+ 3-2, outflow tracer SiO 6-5, mixed dense gas and outflow tracers SO3Σ 65 − 54 and CH3OH lines, and relatively lower density gas tracers 12CO, 13CO, C18O 1-0 (see an example in Fig. 1). This can be explained if a universal similarity of density and thermal structures and probably of shock properties among all these EGO clouds are assumed. Furthermore, the outflow shocks are also required to be produced mainly inside of the natal clouds of the YSOs.The data scatter of the luminosity (and line width) correlations show a clear trend of worsening across larger cloud substructure size scales or toward larger cloud sizes, which demonstrates the growth of randomness in cloud structures and velocity fields. See more details in our paper (He et al. 2012).

RX J0942.7−7726AB: an isolated pre-main-sequence wide binary

We report the discovery of two young M-dwarfs, RX J0942.7-7726 (M1) and 2MASS J09424157-7727130 (M4.5), that were found only 42 arcsec apart in a survey for pre-main sequence stars surrounding the open cluster eta Chamaeleontis. Both stars have congruent proper motions and near-infrared photometry. Medium-resolution spectroscopy reveals that they are coeval (age 8-12 Myr), codistant (100-150 pc) and thus almost certainly form a true wide binary with a projected separation of 4000-6000 AU. The system appears too old and dynamically fragile to have originated in eta Cha and a traceback analysis argues for its birth in or near the Scorpius-Centaurus OB Association. RX J0942.7-7726AB joins a growing group of wide binaries kinematically linked to Sco-Cen, suggesting that such fragile systems can survive the turbulent environment of their natal molecular clouds while still being dispersed with large velocities. Conversely, the small radial velocity difference between the stars (2.7 \pm 1.0 km/s) could mean the system is unbound, a result of the coincidental ejection of two single stars with similar velocity vectors from the OB association early in its evolution.

Accurate and homogeneous abundance patterns in solar-type stars of the solar neighbourhood: a chemo-chronological analysis

We report the abundances of C, Na, Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Sm in 25 solar-type stars in the solar neighbourhood, and their correlations with ages, kinematics, and orbital parameters. The spectroscopic analysis, based high resolution and high S/N ratio data, was differential to the Sun and applied to atomic line EWs and to C and C2 spectral synthesis. We performed a statistical study using a tree clustering analysis, searching for groups of stars sharing similar abundance patterns. We derived Teff, log(g), and [Fe/H] with errors of 30 K, 0.13 dex, and 0.05 dex, respectively. The average error in [X/Fe] is 0.06 dex. Ages were derived from theoretical HR diagrams and memberships in kinematical moving groups. We identified four stellar groups: with over-solar abundances (<[X/H]> = +0.26 dex), under-solar abundances (<[X/H]> = -0.24 dex), and intermediate values (<[X/H]> = -0.06 and +0.06 dex) but with distinct chemical patterns. Stars sharing solar metallicity, age, and Galactic orbit possibly have non-solar abundance, an effect either of chemical heterogeneity in their natal clouds or migration. A trend of [Cu/Fe] with [Ba/Fe] seems to exist, in agreement with previous claims in the literature, and maybe also of [Sm/Fe] with [Ba/Fe]. No such correlation involving C, Na, Mn, and Zn is observed. [Mg/Fe], [Sc/Fe], and [Ti/Fe] increase with age. [Mn/Fe] and [Cu/Fe] first increase towards younger stars up to the solar age, and then decrease, a result we interpret as possibly related to time-varying yields of SN Ia and the weak s-process. [Sr/Fe], [Y/Fe], [Sr/Mg], [Y/Mg], [Sr/Zn], and [Y/Zn] linearly increase towards younger stars. [Zr/Fe], [Ce/Fe], [Nd/Fe], [Ba/Mg], [Ba/Zn], and [Sr,Y,Ba/Sm] increase but only for stars younger than the Sun. The steepest negative age relation is due to [Ba/Fe], but only for stars younger than the Sun.