A Data-driven Model of Nucleosynthesis with Chemical Tagging in a Lower-dimensional Latent Space

Chemical tagging seeks to identify unique star formation sites from present-day stellar abundances. Previous techniques have treated each abundance dimension as being statistically independent, despite theoretical expectations that many elements can be produced by more than one nucleosynthetic process. In this work, we introduce a data-driven model of nucleosynthesis, where a set of latent factors (e.g., nucleosynthetic yields) contribute to all stars with different scores and clustering (e.g., chemical tagging) is modeled by a mixture of multivariate Gaussians in a lower-dimensional latent space. We use an exact method to simultaneously estimate the factor scores for each star, the partial assignment of each star to each cluster, and the latent factors common to all stars, even in the presence of missing data entries. We use an information-theoretic Bayesian principle to estimate the number of latent factors and clusters. Using the second Galah data release, we find that six latent factors are preferred to explain N = 2566 stars with 17 chemical abundances. We identify the rapid- and slow neutron-capture processes, as well as latent factors consistent with Fe-peak and α-element production, and another where K and Zn dominate. When we consider N ~ 160,000 stars with missing abundances, we find another seven factors, as well as 16 components in latent space. Despite these components showing separation in chemistry, which is explained through different yield contributions, none show significant structure in their positions or motions. We argue that more data and joint priors on cluster membership that are constrained by dynamical models are necessary to realize chemical tagging at a galactic-scale. We release accompanying software that scales well with the available data, allowing for the model's parameters to be optimized in seconds given a fixed number of latent factors, components, and ~107 abundance measurements.We acknowledge support from the Australian Research Council through Discovery Project DP160100637. J.B.H. is supported by a Laureate Fellowship from the Australian Research Council. Parts of this research were supported by the Australian Research Council (ARC) Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. S.~B. acknowledges funds from the Alexander von Humboldt Foundation in the framework of the Sofja Kovalevskaja Award endowed by the Federal Ministry of Education and Research. S.B. is supported by the Australian Research Council (grants DP150100250 and DP160103747). S.L.M. acknowledges the support of the UNSW Scientia Fellowship program. J.D.S., S.L.M., and D.B.Z. acknowledge the support of the Australian Research Council through Discovery Project grant DP180101791. The Galah survey is based on observations made at the Australian Astronomical Observatory, under programmes A/2013B/13, A/2014A/25, A/2015A/19, and A/2017A/18. We acknowledge the traditional owners of the land on which the AAT stands, the Gamilaraay people, and pay our respects to elders past and present. This research has made use of NASA’s Astrophysics Data System

Arecaceae

[Extract] Small to tall plants, molloecious or dioecious, polygamous, polygamodioecious, polygamoinonoecious, and hapaxanthic or pleonanthic. Stems solitary or clustered, acaulescent (not in Australia), erect or climbing, slender to stout; leaf scars annular. Leaves forming a terminal crown, palmate, costapalmate, paripinnate, imparipinnate, bipinnate, or entire. Inflorescence axillary, infrafoliar, interfoliar or suprafoliar, spicate or paniculate, bearing papery to woody, deciduous or persistent bracts; single prophyllar bract always present, proximal on inflorescence, bicarinate, variously shaped; peduncular bracts O- many, bicarinate or tubular, distal to prophyll, variously shaped. Flowers unisexual or bisexual, ebracteate; perianth of usually dissimilar sepals and petals, usually trimerous; segments fused or free, valvate or imbricate, usually thick textured and dull-coloured; stamens 3, 4, 6 or numerous; gynoecium apocarpous with 1-3 carpels or syncarpolls with 3 or sometimes more locules, or pseudo-monomerous; ovary superior, smooth or covered in imbricate scales. Fruit a berry or drupe, small to large, 1- 3- seeded, or to 8 seeded (not in Australia); epicarp smooth, warty, corky (not in Australia), scaly or spiny (not in Australia), usually brightly coloured; mesocarp fibrous, fleshy or dry, or obsolescent; endocarp thin, thick or absent. Seed adhering or not adhering to endocarp, sometimes sarcotestal; endosperm ruminate (due to infolding of seed coat) or homogeneous, rarely with central cavity; embryo small. Eophyll simple, bifid or compound

Arecaceae

[Extract] Small to tall plants, molloecious or dioecious, polygamous, polygamodioecious, polygamoinonoecious, and hapaxanthic or pleonanthic. Stems solitary or clustered, acaulescent (not in Australia), erect or climbing, slender to stout; leaf scars annular. Leaves forming a terminal crown, palmate, costapalmate, paripinnate, imparipinnate, bipinnate, or entire. Inflorescence axillary, infrafoliar, interfoliar or suprafoliar, spicate or paniculate, bearing papery to woody, deciduous or persistent bracts; single prophyllar bract always present, proximal on inflorescence, bicarinate, variously shaped; peduncular bracts O- many, bicarinate or tubular, distal to prophyll, variously shaped. Flowers unisexual or bisexual, ebracteate; perianth of usually dissimilar sepals and petals, usually trimerous; segments fused or free, valvate or imbricate, usually thick textured and dull-coloured; stamens 3, 4, 6 or numerous; gynoecium apocarpous with 1-3 carpels or syncarpolls with 3 or sometimes more locules, or pseudo-monomerous; ovary superior, smooth or covered in imbricate scales. Fruit a berry or drupe, small to large, 1- 3- seeded, or to 8 seeded (not in Australia); epicarp smooth, warty, corky (not in Australia), scaly or spiny (not in Australia), usually brightly coloured; mesocarp fibrous, fleshy or dry, or obsolescent; endocarp thin, thick or absent. Seed adhering or not adhering to endocarp, sometimes sarcotestal; endosperm ruminate (due to infolding of seed coat) or homogeneous, rarely with central cavity; embryo small. Eophyll simple, bifid or compound

Nomenclatural changes for two Australian species of Livistona R. Br. (Arecaceae)

Abstract is not available for this publication

Revision of calyptrocalyx and the New Guinea species of linospadix (Linospadicinae: Arecoideae: Arecaceae)

A revision of Calyptrocalyx and the New Guinea species of Linspadix (Linospadicinae: Arecoideae: Arecaceae) is provided. For Calyptrocalyx, twenty-six species are recognised, and two for Linospadix. Three species, Calyptrocalyx amoenus, C. awa, and C. yanutumene are described as new. The following new combinations are made: Calyptrocalyx arfakianus, C. caudiculatus, C. flabellatus, C. geonomiformis, C. hollrungii, C. julianettii, C. lepidotus, C. merrillianus, C. micholitzii, C. multifidus, and C. pusillus which were formerly species of Paralinospadix. Neotypes are proposed for C. lauterbachianus, C. laxiflorus, C. pachystachys, C. pauciflorus, and C. polyphyllus. Linospadix has two species in New Guinea, L. albertisiana and L. canina

New species of Livistona (Arecaceae) from New Guinea

The genus Livistona R.Br., over its entire range, is presently under revision by JLD. Recently, Rodd (1998) revised the Australian species, in which he described five new species and one variety, whilst new species have been described for Papua New Guinea and Australia (Dowe & Barfod 2001), and for Vietnam (Nguyen & Kiew 2000). Completion of the treatment of Livistona for New Guinea is part of the Palms of New Guinea project coordinated at the Royal Botanic Gardens, Kew. With the description of these new species, there will be nine Livistona species recognized for New Guinea. Of these, six are endemic

New species of Livistona R. Br. (Arecaceae) from north Queensland and Papua New Guinea

Livistona concinna, L. surru and L. tothur are described as new. Livistona concinna is endemic in north Queensland, and L. surru and L. tothur are endemic in Papua New Guinea. Each species is illustrated

Gronophyllum cariosum, an ornamental new species from Papua New Guinea

In the course of recent field-work undertaken in the Papua New Guinean West Sepik Province - the most biologically rich region of the island - a number of new palm species were identified. One such species is described here and notes provided

A new species of rheophytic palm from New Guinea

A new rheophytic palm, Hydriastele rheophytica, is described for New Guinea. Although other New Guinea palm species occur on the banks of fast flowing rivers, they also occur on adjacent slopes and in other locations. Hydriastele rheophytica is confined to\ud stream edges as part of a rheophytic community. This elegant species has been in cultivation in north Queensland for several years, proving adaptable to, and thriving in, many conditions