The GALAH Survey: Chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and $Gaia$ eDR3

Buder, Sven; Lind, Karin; Ness, Melissa K.; Feuillet, Diane K.; Horta, Danny; Monty, Stephanie; Buck, Tobias; Nordlander, Thomas; Bland-Hawthorn, Joss; Casey, Andrew R.; De Silva, Gayandhi M.; D'Orazi, Valentina; Freeman, Ken C.; Hayden, Michael R.; Kos, Janez; Martell, Sarah L.; Lewis, Geraint F.; Lin, Jane; Schlesinger, Katharine. J.; Sharma, Sanjib; Simpson, Jeffrey D.; Stello, Dennis; Zucker, Daniel B.; Zwitter, Tomaz; Ciuca, Ioana; Horner, Jonathan; Kobayashi, Chiaki; Ting, Yuan-Sen; Wyse, Rosemary F. G.; Collaboration, The GALAH

doi:10.48550/arxiv.2109.04059

Cited by 5 publications

(6 citation statements)

References 154 publications

(373 reference statements)

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“…Presumably, the halo shows this interesting residual variability and structure as it is comprised of stars from many different star formation environments (e.g. Scannapieco et al 2021;Naidu et al 2021;Bonaca et al 2020;Hallakoun & Maoz 2021;Ishigaki et al 2021;Naidu et al 2020;Buder et al 2021a). Note where some elements show large positive residuals, others show large negative residuals.…”

Section: The Holistic View Of Residual Scatter In the Milkymentioning

confidence: 97%

The homogeneity of the star forming environment of the Milky Way disk over time

Ness,

Wheeler,

McKinnon

et al. 2021

Preprint

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Stellar abundances and ages afford the means to link chemical enrichment to galactic formation. In the Milky Way, individual element abundances show tight correlations with age, which vary in slope across ([Fe/H]-[α/Fe]). Here, we step from characterising abundances as measures of age, to understanding how abundances trace properties of stellar birth-environment in the disk over time. Using measurements from ∼27,000 APOGEE stars (R=22,500, SNR>200), we build simple local linear models to predict a sample of elements (X = Si, O, Ca, Ti, Ni, Al, Mn, Cr) using (Fe, Mg) abundances alone, as fiducial tracers of supernovae production channels. Given [Fe/H] and [Mg/H], we predict these elements, [X/H], to about double the uncertainty of their measurements. The intrinsic dispersion, after subtracting measurement errors in quadrature is ≈ 0.015 − 0.04 dex. The residuals of the prediction (measurement − model) for each element demonstrate that each element has an individual link to birth properties at fixed (Fe, Mg). Residuals from primarily massive-star supernovae (i.e. Si, O, Al) partially correlate with guiding radius. Residuals from primarily supernovae Ia (i.e. Mn, Ni) partially correlate with age. A fraction of the intrinsic scatter that persists at fixed (Fe, Mg), however, after accounting for correlations, does not appear to further discriminate between birth properties that can be traced with present-day measurements. Presumably, this is because the residuals are also, in part, a measure of the typical (in)-homogeneity of the disk's stellar birth environments, previously inferred only using open-cluster systems. Our study implies at fixed birth radius and time, there is a median scatter of ≈ 0.01 − 0.015 dex in elements generated in supernovae sources.

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Section: The Holistic View Of Residual Scatter In the Milkymentioning

confidence: 97%

The homogeneity of the star forming environment of the Milky Way disk over time

Ness,

Wheeler,

McKinnon

et al. 2021

Preprint

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“…A list of studies have shown that these disrupted stellar systems, together with globular clusters and chemically peculiar stars with halo orbits, can be grouped based on similar orbital properties, suggestive of their common origins (Roederer et al 2018;Myeong et al 2018b;Myeong et al 2019;Naidu et al 2020;Yuan et al 2020b;Bonaca et al 2021;Limberg et al 2021;Gudin et al 2021;Li et al 2021a;Shank et al 2021). Detailed abundance studies for these stellar debris have been made possible by HRspectroscopic follow-up studies (Ji et al 2020;Aguado et al 2021a,b;Matsuno et al 2021;Gull et al 2021), as well as by HR-spectroscopic surveys, such as the GALactic Archaeology with HERMES survey (GALAH; Buder et al 2021;Simpson et al 2021).…”

Section: Introductionmentioning

confidence: 99%

The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO

Yuan,

Malhan,

Sestito

et al. 2021

Preprint

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We combine the power of two stream-searching tools, STREAMFINDER and StarGO applied to the Gaia EDR3 data, to detect stellar debris belonging to the Cetus stream system that forms a complex, nearly polar structure around the Milky Way. In this work, we find the southern extensions of the northern Cetus stream as the Palca stream and a new southern stream, which overlap on the sky but have different distances. These two stream wraps extend over more than ∼ 100 • on the sky (−60 • < δ < +40 • ). The current N-body model of the system reproduces both wraps in the trailing arm. We also show that the Cetus system is confidently associated with the Triangulum/Pisces, Willka Yaku, and the recently discovered C-20 streams. The association with the ATLAS-Aliqa Uma stream is much weaker. All of these stellar debris are very metal-poor, comparable to the average metallicity of the southern Cetus stream with [Fe/H] = −2.17 ± 0.2. The estimated stellar mass of the Cetus progenitor is at least 10 5.6 M , compatible with Ursa Minor or Draco dwarf galaxies. The associated globular cluster with similar stellar mass, NGC 5824 very possibly was accreted in the same group infall. The multi-wrap Cetus stream is a perfect example of a dwarf galaxy that has undergone several periods of stripping, leaving behind debris at multiple locations in the halo. The full characterization of such systems is crucial to unravel the assembly history of the Milky Way and, as importantly, to provide nearby fossils to study ancient low-mass dwarf galaxies.

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“…Unsupervised learning methods have been used to define and study kinematic structures of galaxies (Doménech-Moral et al 2012;Obreja et al 2018Obreja et al , 2019Buck et al 2018Buck et al , 2019b or identify accreted stars from disrupted satellites of the MW (e.g. Buder et al 2021a) in the GALAH survey data (Buder et al 2021b). Hierarchical clustering on the other hand was employed to investigate the connection between stellar birth radii and their abundances (e.g.…”

Section: Introductionmentioning

confidence: 99%

Predicting resolved galaxy properties from photometric images using convolutional neural networks

Buck¹,

Wolf²

2021

Preprint

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Multi-band images of galaxies reveal a huge amount of information about their morphology and structure. However, inferring properties of the underlying stellar populations such as age, metallicity or kinematics from those images is notoriously difficult. Traditionally such information is best extracted from expensive spectroscopic observations. Here we present the Painting IntrinsiC Attributes onto SDSS Objects (PICASSSO) project and test the information content of photometric multi-band images of galaxies. We train a convolutional neural network on 27,558 galaxy image pairs to establish a connection between broad-band images and the underlying physical stellar and gaseous galaxy property maps. We test our machine learning (ML) algorithm with SDSS ugriz mock images for which uncertainties and systematics are exactly known. We show that multi-band galaxy images contain enough information to reconstruct 2d maps of stellar mass, metallicity, age and gas mass, metallicity as well as star formation rate. We recover the true stellar properties on a pixel by pixel basis with only little scatter, ∼ < 20% compared to ∼ 50% statistical uncertainty from traditional mass-to-light-ratio based methods. We further test for any systematics of our algorithm with image resolution, training sample size or wavelength coverage. We find that galaxy morphology alone constrains stellar properties to better than ∼ 20% thus highlighting the benefits of including morphology into the parameter estimation. The machine learning approach can predict maps of high resolution, only limited by the resolution of the input bands, thus achieve higher resolution than IFU observations. The network architecture and all code is publicly available on GitHub .

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The GALAH Survey: Chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and $Gaia$ eDR3

Cited by 5 publications

References 154 publications

The homogeneity of the star forming environment of the Milky Way disk over time

The homogeneity of the star forming environment of the Milky Way disk over time

The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO

Predicting resolved galaxy properties from photometric images using convolutional neural networks

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