Chemical compositions and kinematics of the Hercules stream

Ramya, P.; Reddy, Bacham E.; Lambert, David L.; Musthafa, M.M.

doi:10.1093/mnras/stw852

Cited by 14 publications

(24 citation statements)

References 55 publications

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“…The Hercules stream is almost missing in the TD map, so that probably is constructed mostly of thin disk stars. The same result was obtained by Bensby et al (2014) and Ramya et al (2016) from a chemical abundances analysis of stars that belong to the Hercules (for more discussions see Sect. 5.4).…”

Section: Thin and Thick Disk Structuressupporting

confidence: 81%

“…Later, Bensby et al (2014) re-examined the chemical composition of Hercules stream stars and found that it mainly consists of stars that chemically can be associated with both the thin and thick disks. Ramya et al (2016) on the other hand studied 58 Hercules stream red giants and found that they are mostly metalrich stars from the thin disk. The somewhat discrepant results could be explained with different target selection methods used by the two studies.…”

Section: Individual Structuresmentioning

confidence: 99%

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Kinematic structures of the solar neighbourhood revealed byGaiaDR1/TGAS and RAVE

Kushniruk

Schirmer

Bensby

2017

A&A

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Context. The velocity distribution of stars in the Solar neighbourhood is inhomogeneous and rich with stellar streams and kinematic structures. These may retain important clues of the formation and dynamical history of the Milky Way. However, the nature and origin of many of the streams and structures is unclear, hindering our understanding of how the Milky Way formed and evolved. Aims. We aim to study the velocity distribution of stars of the Solar neighbourhood and investigate the properties of individual kinematic structures in order to improve our understanding of their origins. Methods. Using the astrometric data provided by Gaia DR1/TGAS and radial velocities from RAVE DR5 we perform a wavelet analysis with the à trous algorithm to 55 831 stars that have U and V velocity uncertainties less than 4 km s −1 . An auto-convolution histogram method is used to filter the output data, and we then run Monte Carlo simulations to verify that the detected structures are real due to velocity uncertainties. Additionally we analysed our stellar sample by splitting all stars into a nearby sample (< 300 pc) and a distant sample (> 300 pc), and two chemically defined samples that to a first degree represent the thin and the thick disks. Results. We detect 19 kinematic structures in the Solar neighbourhood between scales 3 − 16 km s −1 at the 3σ confidence level. Among them we identified well-known groups (such as Hercules, Sirius, Coma Berenices, Pleiades, and Wolf 630), confirmed recently detected groups (such as Antoja12 and Bobylev16), and detected a new structure at (U, V) ≈ (37, 8) km s −1 . Another three new groups are tentatively detected, but require further confirmation. Some of the detected groups show clear dependence on distance in the sense that they are only present in the nearby sample (< 300 pc), and others appear to be correlated with chemistry as they are only present in either of the chemically defined thin and thick disk samples. Conclusions. With the much enlarged stellar sample and much increased precision in distances, proper motions, provided by Gaia DR1 TGAS we have shown that the velocity distribution of stars in the Solar neighbourhood contains more structures than previously known. A new feature is discovered and three recently detected groups are confirmed at high confidence level. Dividing the sample based on distance and/or metallicity shows that there are variety of structures which are as large-scale and small-scale groups, some of them have clear trends on metallicities, others are a mixture of both disk stars and based on that we discuss possible origin of each group.

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Section: Thin and Thick Disk Structuressupporting

confidence: 81%

Section: Individual Structuresmentioning

confidence: 99%

Kinematic structures of the solar neighbourhood revealed byGaiaDR1/TGAS and RAVE

Kushniruk

Schirmer

Bensby

2017

A&A

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“…), to explore the mysterious "cosmological lithium problem" (Fu et al 2015), to derive the main parameters of star clusters (for instance, Donati et al 2014;Borissova et al 2014; San Roman et al 2015; Goudfrooij et al 2015) and Galactic structure (e.g. Küpper et al 2015;Li et al 2016;Balbinot et al 2016; Ramya et al 2016), to study dust formation (e.g. Nanni et al 2013;Nanni et al 2014), to constrain dust extinction (e.g.…”

Section: Introductionmentioning

confidence: 99%

New parsec data base of α-enhanced stellar evolutionary tracks and isochrones – I. Calibration with 47 Tuc (NGC 104) and the improvement on RGB bump

Bressan

Marigo

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Precise studies on the Galactic bulge, globular cluster, Galactic halo and Galactic thick disk require stellar models with α enhancement and various values of helium content. These models are also important for extra-Galactic population synthesis studies. For this purpose we complement the existing PARSEC models, which are based on the solar partition of heavy elements, with α-enhanced partitions. We collect detailed measurements on the metal mixture and helium abundance for the two populations of 47 Tuc (NGC 104) from the literature, and calculate stellar tracks and isochrones with these α-enhanced compositions. By fitting the precise color-magnitude diagram with HST ACS/WFC data, from low main sequence till horizontal branch, we calibrate some free parameters that are important for the evolution of low mass stars like the mixing at the bottom of the convective envelope. This new calibration significantly improves the prediction of the RGB bump brightness. Comparison with the observed RGB and HB luminosity functions also shows that the evolutionary lifetimes are correctly predicted. As a further result of this calibration process, we derive the age, distance modulus, reddening, and the red giant branch mass loss for 47 Tuc. We apply the new calibration and α-enhanced mixtures of the two 47 Tuc populations ( [α/Fe] ∼0.4 and 0.2) to other metallicities. The new models reproduce the RGB bump observations much better than previous models. This new PARSEC database, with the newly updated α-enhanced stellar evolutionary tracks and isochrones, will also be part of the new stellar products for Gaia .

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“…It must be remembered that the figure represents the arms in their own standard of rest, which rotates with a velocity of the order of 28 km/s/kpc, in the inertial frame. Ramya et al (2016) performed a detailed study of the stellar population of the Hercules stream. They found an average metallicity of the order of (Fe/H) 0.15, Ziurys (2006), Glassgold (1996), Agúndez et al (2014), the 2018 Census of molecular detections presented by McGuire (2018), and current detections reported by Cernicharo et al (2019).…”

Section: Dynamics Very Close To the Sun Moving Groups And Stellar Streamsmentioning

confidence: 99%

Interrelations Between Astrochemistry and Galactic Dynamics

Mendoza

Duronea

Ronsó

et al. 2021

Front. Astron. Space Sci.

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This paper presents a review of ideas that interconnect astrochemistry and galactic dynamics. Since these two areas are vast and not recent, each one has already been covered separately by several reviews. After a general historical introduction, and a needed quick review of processes such as stellar nucleosynthesis that gives the base to understand the interstellar formation of simple chemical compounds (e.g., H2, CO, NH3, and H2O), we focus on a number of topics that are at the crossing of the two big areas, dynamics and astrochemistry. Astrochemistry is a flourishing field that intends to study the presence and formation of molecules as well as the influence of them on the structure, evolution, and dynamics of astronomical objects. The progress in the knowledge on the existence of new complex molecules and of their process of formation originates from the observational, experimental, and theoretical areas that compose the field. The interfacing areas include star formation, protoplanetary disks, the role of the spiral arms, and the chemical abundance gradients in the galactic disk. It often happens that the physical conditions in some regions of the interstellar medium are only revealed by means of molecular observations. To organize a rough classification of chemical evolution processes, we discuss about how astrochemistry can act in three different contexts, namely, the chemistry of the early universe, including external galaxies, star-forming regions, and asymptotic giant branch (AGB) stars and circumstellar envelopes. We mention that our research is stimulated by plans for instruments and projects, such as the ongoing Large Latin American Millimeter Array (LLAMA), which consists in the construction of a 12 m sub-mm radio telescope in the Andes. Thus, modern and new facilities can play a key role in new discoveries not only in astrochemistry but also in radio astronomy and related areas. Furthermore, the research on the origin of life is also a stimulating perspective.

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Chemical compositions and kinematics of the Hercules stream

Abstract: An abundance analysis is reported of 58 K giants identified by Famaey et al. (2005) as highly probable members of the Hercules stream selected from stars north of the celestial equator in the Hipparcos catalogue.

Cited by 14 publications

References 55 publications

Kinematic structures of the solar neighbourhood revealed byGaiaDR1/TGAS and RAVE

Kinematic structures of the solar neighbourhood revealed byGaiaDR1/TGAS and RAVE

New parsec data base of α-enhanced stellar evolutionary tracks and isochrones – I. Calibration with 47 Tuc (NGC 104) and the improvement on RGB bump

Interrelations Between Astrochemistry and Galactic Dynamics

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