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I review recent SDSS results related to galaxies and large scale structure, including: (1) discovery of coherent, unbound structures in the stellar halo, (2) demonstration that Pal 5 has tidal tails and Draco doesn't, (3) precise…

Astrophysics · Physics 2007-05-23 David H. Weinberg

Galaxies are predicted to assemble their stellar haloes through the accretion of stellar material from interactions with their cosmic environment. Observations that trace stellar halo buildup probe the processes that drive galaxy size and…

We present a machine learning (ML) approach for the prediction of galaxies' dark matter halo masses that achieves an improved performance over conventional methods. We train three ML algorithms (\texttt{XGBoost}, Random Forests, and neural…

Astrophysics of Galaxies · Physics 2019-10-16 Victor F. Calderon , Andreas A. Berlind

For the vast majority of stars in the second Gaia data release, reliable distances cannot be obtained by inverting the parallax. A correct inference procedure must instead be used to account for the nonlinearity of the transformation and…

Solar and Stellar Astrophysics · Physics 2018-08-08 C. A. L. Bailer-Jones , J. Rybizki , M. Fouesneau , G. Mantelet , R. Andrae

Dark matter subhaloes are key for the predictions of simulations of structure formation, but their existence frequently ends prematurely due to two technical issues, namely numerical disruption in N-body simulations and halo finders failing…

Cosmology and Nongalactic Astrophysics · Physics 2023-05-03 Benedikt Diemer , Peter Behroozi , Philip Mansfield

We model the formation of the Galactic stellar halo via the accretion of satellite galaxies onto a time-dependent semi-cosmological galactic potential. Our goal is to characterize the substructure left by these accretion events in a close…

Astrophysics of Galaxies · Physics 2015-05-18 Facundo A. Gómez , Amina Helmi , Anthony G. A. Brown , Yang-Shyang Li

The inference of the Milky Way halo mass requires modelling the phase space structure of dynamical tracers, with different tracers following different models and having different levels of sensitivity to the halo mass. For steady-state…

Astrophysics of Galaxies · Physics 2020-05-20 Jiaxin Han , Wenting Wang , Zhaozhou Li

We present a study of the membership of the Hyades open cluster, derive kinematically-modelled parallaxes of its members, and study the colour-absolute magnitude diagram of the cluster. We use Gaia DR1 Tycho-Gaia Astrometric Solution (TGAS)…

Astrophysics of Galaxies · Physics 2018-04-04 Stella Reino , Jos de Bruijne , Eleonora Zari , Francesca d'Antona , Paolo Ventura

Mock halo catalogues are indispensable data products for developing and validating cosmological inference pipelines. A major challenge in generating mock catalogues is modelling the halo or galaxy bias, which is the mapping from matter…

Cosmology and Nongalactic Astrophysics · Physics 2024-10-16 Simon Ding , Guilhem Lavaux , Jens Jasche

We use N-body cosmological simulations and empirical galaxy models to study the merger history of dwarf-mass galaxies (with M_halo~10^10 M_Sun). Our input galaxy models describe the stellar mass-halo mass relation, and the galaxy occupation…

Astrophysics of Galaxies · Physics 2022-01-04 Alis J. Deason , Sownak Bose , Azadeh Fattahi , Nicola C. Amorisco , Wojciech Hellwing , Carlos S. Frenk

We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of…

The Galactic Archaeology with HERMES (GALAH) Survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R$\simeq$28,000)…

The Galactic halo is supposed to form from merging with nearby dwarf galaxies. In order to probe different components of the Galactic halo, we have applied the Gaussian Mixture Models method to a selected sample of metal poor stars with…

Astrophysics of Galaxies · Physics 2021-06-23 Xilong Liang , Yuqin Chen , Jingkun Zhao , Gang Zhao

We use the SDSS-Gaia Catalogue to identify six new pieces of halo substructure. SDSS-Gaia is an astrometric catalogue that exploits SDSS data release 9 to provide first epoch photometry for objects in the Gaia source catalogue. We use a…

Astrophysics of Galaxies · Physics 2018-01-25 G. C. Myeong , N. W. Evans , V. Belokurov , N. C. Amorisco , S. Koposov

We propose a versatile and accurate method to estimate the halo mass and concentration from the kinematics of satellite galaxies. We construct the 6D phase-space distribution function of satellites from a cosmological simulation based on…

Astrophysics of Galaxies · Physics 2019-12-02 Zhao-Zhou Li , Yong-Zhong Qian , Jiaxin Han , Wenting Wang , Y. P. Jing

Upcoming Stage-IV surveys will deliver measurements of distribution of matter with unprecedented precision, demanding highly accurate theoretical models for cosmological parameter inference. A major source of modeling uncertainty lies in…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-01 Pranjal R. S. , Shivam Pandey , Dhayaa Anbajagane , Elisabeth Krause , Klaus Dolag

The relationship between galaxies and haloes is central to the description of galaxy formation, and a fundamental step towards extracting precise cosmological information from galaxy maps. However, this connection involves several complex…

Cosmology and Nongalactic Astrophysics · Physics 2023-05-03 Natália V. N. Rodrigues , Natalí S. M. de Santi , Antonio D. Montero-Dorta , L. Raul Abramo

We study the density profile and shape of the Galactic halo using deep multicolour images from the MENeaCS and CCCP projects, over 33 fields selected to avoid overlap with the Galactic plane. Using multicolour selection and PSF…

Astrophysics of Galaxies · Physics 2015-06-24 B. Pila-Díez , J. T. A. de Jong , K. Kuijken , R. F. J. van der Burg , H. Hoekstra

Aims: Develop a data-driven and statistically based method for finding such clumps in Integrals of Motion space for nearby halo stars and evaluating their significance robustly. Methods: We use data from Gaia EDR3 extended with radial…

Astrophysics of Galaxies · Physics 2022-09-14 S. Sofie Lövdal , Tomás Ruiz-Lara , Helmer H. Koppelman , Tadafumi Matsuno , Emma Dodd , Amina Helmi

The Milky Way's stellar halo, which extends to $>100$ kpc, encodes the evolutionary history of our Galaxy. However, most studies of the halo to date have been limited to within a few kpc of the Sun. Here, we characterize differences between…

Astrophysics of Galaxies · Physics 2022-11-10 Katherine Sharpe , Rohan P. Naidu , Charlie Conroy