CONSTRAINTS ON THE SHAPE OF THE MILKY WAY DARK MATTER HALO FROM JEANS EQUATIONS APPLIED TO SLOAN DIGITAL SKY SURVEY DATA

ABSTRACT We present a machine learning (ML) approach for the prediction of galaxies’ dark matter halo masses which achieves an improved performance over conventional methods. We train three ML algorithms (XGBoost, random forests, and neural network) to predict halo masses using a set of synthetic galaxy catalogues that are built by populating dark matter haloes in N-body simulations with galaxies and that match both the clustering and the joint distributions of properties of galaxies in the Sloan Digital Sky Survey (SDSS). We explore the correlation of different galaxy- and group-related properties with halo mass, and extract the set of nine features that contribute the most to the prediction of halo mass. We find that mass predictions from the ML algorithms are more accurate than those from halo abundance matching (HAM) or dynamical mass estimates (DYN). Since the danger of this approach is that our training data might not accurately represent the real Universe, we explore the effect of testing the model on synthetic catalogues built with different assumptions than the ones used in the training phase. We test a variety of models with different ways of populating dark matter haloes, such as adding velocity bias for satellite galaxies. We determine that, though training and testing on different data can lead to systematic errors in predicted masses, the ML approach still yields substantially better masses than either HAM or DYN. Finally, we apply the trained model to a galaxy and group catalogue from the SDSS DR7 and present the resulting halo masses.

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Modelling the tightest relation between galaxy properties and dark matter halo properties from hydrodynamical simulations of galaxy formation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa620 ◽

2020 ◽

Vol 493 (3) ◽

pp. 4453-4462

Author(s):

Jian-hua He

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Stellar Mass ◽

Sloan Digital Sky Survey ◽

Dark Matter Halo ◽

Strong Interactions ◽

Circular Velocity ◽

Sky Survey ◽

Hydrodynamical Simulations ◽

Robust Prediction

ABSTRACT We investigate how a property of a galaxy correlates most tightly with a property of its host dark matter halo, using state-of-the-art hydrodynamical simulations of galaxy formation: EAGLE, Illustris, and IllustrisTNG. Unlike most of the previous work, our analyses focus on all types of galaxies, including both central and satellite galaxies. We find that the stellar mass of a galaxy at the epoch of the peak circular velocity with an evolution correction gives the tightest such correlation to the peak circular velocity Vpeak of the galaxy’s underling dark matter halo. The evolution of galaxy stellar mass reduces rather than increases scatter in such a relation. We also find that one major source of scatter comes from star stripping due to the strong interactions between galaxies. Even though, we show that the size of scatter predicted by hydrodynamical simulations has a negligible impact on the clustering of dense Vpeak-selected subhalo from simulations, which suggests that even the simplest subhalo abundance matching (SHAM), without scatter and any additional free parameter, can provide a robust prediction of galaxy clustering that can agree impressively well with the observations from the Sloan Digital Sky Survey (SDSS) main galaxy survey.

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Cosmological Parameter Determination fromPlanckand Sloan Digital Sky Survey Data in Λ Cold+Hot Dark Matter Cosmologies

The Astrophysical Journal ◽

10.1086/322448 ◽

2001 ◽

Vol 558 (1) ◽

pp. 10-22 ◽

Cited By ~ 5

Author(s):

L. A. Popa ◽

C. Burigana ◽

N. Mandolesi

Keyword(s):

Dark Matter ◽

Survey Data ◽

Cosmological Parameter ◽

Sloan Digital Sky Survey ◽

Parameter Determination ◽

Sky Survey

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Characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with SDSS DR16

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab871 ◽

2021 ◽

Vol 504 (1) ◽

pp. 65-88

Author(s):

Abhijeet Anand ◽

Dylan Nelson ◽

Guinevere Kauffmann

Keyword(s):

Formation Rate ◽

Sloan Digital Sky Survey ◽

Gas Absorption ◽

Dark Matter Halo ◽

Star Forming ◽

Sky Survey ◽

Optical Continuum ◽

Circumgalactic Medium ◽

Emission Line Galaxies ◽

Red Galaxies

ABSTRACT In order to study the circumgalactic medium (CGM) of galaxies we develop an automated pipeline to estimate the optical continuum of quasars and detect intervening metal absorption line systems with a matched kernel convolution technique and adaptive S/N criteria. We process ∼ one million quasars in the latest Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and compile a large sample of ∼ 160 000 Mg ii absorbers, together with ∼ 70 000 Fe ii systems, in the redshift range 0.35 < zabs < 2.3. Combining these with the SDSS DR16 spectroscopy of ∼1.1 million luminous red galaxies (LRGs) and ∼200 000 emission line galaxies (ELGs), we investigate the nature of cold gas absorption at 0.5 < z < 1. These large samples allow us to characterize the scale dependence of Mg ii with greater accuracy than in previous work. We find that there is a strong enhancement of Mg ii absorption within ∼50 kpc of ELGs, and the covering fraction within 0.5rvir of ELGs is 2–5 times higher than for LRGs. Beyond 50 kpc, there is a sharp decline in Mg ii for both kinds of galaxies, indicating a transition to the regime where the CGM is tightly linked with the dark matter halo. The Mg ii-covering fraction correlates strongly with stellar mass for LRGs, but weakly for ELGs, where covering fractions increase with star formation rate. Our analysis implies that cool circumgalactic gas has a different physical origin for star-forming versus quiescent galaxies.

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Testing homogeneity in the Sloan Digital Sky Survey Data Release Twelve with Shannon entropy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stv2166 ◽

2015 ◽

Vol 454 (3) ◽

pp. 2647-2656 ◽

Cited By ~ 16

Author(s):

Biswajit Pandey ◽

Suman Sarkar

Keyword(s):

Survey Data ◽

Shannon Entropy ◽

Sloan Digital Sky Survey ◽

Sky Survey ◽

Data Release ◽

Testing Homogeneity

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Clustering and Halo Occupation Distribution of Active Galactic Nuclei

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314003937 ◽

2013 ◽

Vol 9 (S304) ◽

pp. 243-243

Author(s):

Takamitsu Miyaji ◽

M. Krumpe ◽

A. Coil ◽

H. Aceves ◽

B. Husemann

Keyword(s):

Cross Correlation ◽

Dynamic Range ◽

Signal To Noise Ratio ◽

Sloan Digital Sky Survey ◽

Dark Matter Halo ◽

Bias Parameter ◽

X Ray ◽

Sky Survey ◽

Galaxy Population ◽

Halo Occupation Distribution

AbstractWe present the results of our series of studies on correlation function and halo occupation distribution of AGNs utilizing data the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS) in the redshift range of 0.07<z<0.36. In order to improve the signal-to-noise ratio, we take cross-correlation approach, where cross-correlation functions (CCF) between AGNs and much more numerous AGNs are analyzed. The calculated CCFs are analyzed using the Halo Occupation Distribution (HOD) model, where the CCFs are divided into the term contributed by the AGN-galaxy pairs that reside in one dark matter halo (DMH), (the 1-halo term) and those from two different DMHs (the 2-halo term). The 2-halo term is the indicator of the bias parameter, which is a function of the typical mass of the DMHs in which AGNs reside. The combination of the 1-halo and 2-halo terms gives, not only the typical DMH mass, but also how the AGNs are distributed among the DMHs as a function of mass separately for those at the center of the DMHs and satellites. The main results are as follows: (1) the range of typical mass of the DMHs in various sub-samples of AGNs log (MDMH/h−1MΘ) ~ 12.4–13.4, (2) we found a dependence of the AGN bias parameter on the X-ray luminosity of AGNs, while the optical luminosity dependence is not significant probably due to smaller dynamic range in luminosity for the optically-selected sample, and (3) the growth of the number of AGNs per DMH (N (MDMH)) with MDMH is shallow, or even may be flat, contrary to that of the galaxy population in general, which grows with MDMH proportionally, suggesting a suppression of AGN triggering in denser environment. In order to investigate the origin of the X-ray luminosity dependence, we are also investigating the dependence of clustering on the black hole mass and the Eddington ratio, we also present the results of this investigation.

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Analysis of Systematic Effects and Statistical Uncertainties in Angular Clustering of Galaxies from Early Sloan Digital Sky Survey Data

The Astrophysical Journal ◽

10.1086/342786 ◽

2002 ◽

Vol 579 (1) ◽

pp. 48-75 ◽

Cited By ~ 181

Author(s):

Ryan Scranton ◽

David Johnston ◽

Scott Dodelson ◽

Joshua A. Frieman ◽

Andy Connolly ◽

...

Keyword(s):

Survey Data ◽

Sloan Digital Sky Survey ◽

Sky Survey ◽

Systematic Effects

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Double X/Peanut Structures in Barred Galaxies – Insights from an N–body Simulation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3814 ◽

2020 ◽

Author(s):

Bogdan C Ciambur ◽

Francesca Fragkoudi ◽

Sergey Khoperskov ◽

Paola Di Matteo ◽

Françoise Combes

Keyword(s):

Dark Matter ◽

Milky Way ◽

Large Fraction ◽

Formation Time ◽

Dark Matter Halo ◽

Barred Galaxies ◽

Pattern Speed ◽

Nearby Galaxies ◽

Dynamical Instabilities ◽

Bow Tie

Abstract Boxy, peanut– or X–shaped “bulges” are observed in a large fraction of barred galaxies viewed in, or close to, edge-on projection, as well as in the Milky Way. They are the product of dynamical instabilities occurring in stellar bars, which cause the latter to buckle and thicken vertically. Recent studies have found nearby galaxies that harbour two such features arising at different radial scales, in a nested configuration. In this paper we explore the formation of such double peanuts, using a collisionless N–body simulation of a pure disc evolving in isolation within a live dark matter halo, which we analyse in a completely analogous way to observations of real galaxies. In the simulation we find a stable double configuration consisting of two X/peanut structures associated to the same galactic bar – rotating with the same pattern speed – but with different morphology, formation time, and evolution. The inner, conventional peanut-shaped structure forms early via the buckling of the bar, and experiences little evolution once it stabilises. This feature is consistent in terms of size, strength and morphology, with peanut structures observed in nearby galaxies. The outer structure, however, displays a strong X, or “bow-tie”, morphology. It forms just after the inner peanut, and gradually extends in time (within 1 to 1.5 Gyr) to almost the end of the bar, a radial scale where ansae occur. We conclude that, although both structures form, and are dynamically coupled to, the same bar, they are supported by inherently different mechanisms.

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