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Our goal in this paper is to test some popular dark matter models by Ly-alpha forest in QSO spectra. Recent observations of the size and velocity of Ly-alpha forest clouds have indicated that the Ly-alpha absorption is probably not given by…

Astrophysics · Physics 2009-10-28 Hongguang BI , Jian GE , Li-Zhi FANG

Theoretical arguments and observations suggest that in massive halos ($>10^{12}\,M_\odot$), the circumgalactic medium (CGM) is dominated by a 'hot' phase with gas temperature near the virial temperature ($T \approx T_{\rm vir}$) and a…

We search for OVI absorption in a Keck HIRES spectrum of the z=3.62 quasar Q1422+231. Comparison of CIV measurements to cosmological simulations shows that \lya forest absorbers with N_HI > 10^{14.5} have [C/H]~=-2.5, for the UV background…

Astrophysics · Physics 2009-10-30 Romeel Davé , Uffe Hellsten , Lars Hernquist , Neal Katz , David Weinberg

We use the EAGLE (Evolution and Assembly of GaLaxies and their Environments) cosmological simulation to study the distribution of baryons, and far-ultraviolet (O VI), extreme-ultraviolet (Ne VIII) and X-ray (O VII, O VIII, Ne IX, and Fe…

Astrophysics of Galaxies · Physics 2020-09-07 Nastasha A. Wijers , Joop Schaye , Benjamin D. Oppenheimer

We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Ly$\alpha$ absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening…

We present model independent reconstructions of quintessence and the Swampland conjectures (SC) using both Machine Learning (ML) and cosmography. In particular, we demonstrate how the synergies between theoretical analyses and ML can…

Cosmology and Nongalactic Astrophysics · Physics 2021-03-31 Rubén Arjona , Savvas Nesseris

In hierarchical cosmogonies at redshift three the matter content of a typical present-day galaxy is dispersed over several individual clumps embedded in sheet-like structures, often aligned along filaments. We have used hydrodynamical…

Astrophysics · Physics 2016-08-30 Michael Rauch , Martin G. Haehnelt , Matthias Steinmetz

We present a new exploratory framework to model galaxy formation and evolution in a hierarchical universe by using machine learning (ML). Our motivations are two-fold: (1) presenting a new, promising technique to study galaxy formation, and…

Astrophysics of Galaxies · Physics 2015-11-30 Harshil M. Kamdar , Matthew J. Turk , Robert J. Brunner

We use a high-resolution cosmological simulation that includes hydrodynamics, multiphase star formation, and galactic winds to predict the distribution of metal line emission at z~0 from the intergalactic medium (IGM). We focus on two…

Astrophysics · Physics 2009-11-10 Steven Furlanetto , Joop Schaye , Volker Springel , Lars Hernquist

The methods by which one characterizes the distribution of matter in cosmological simulations is intrinsically different from how one performs the same task observationally. In this paper, we make substantial steps towards comparing…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Hilary Egan , Britton D. Smith , Brian W. O'Shea , J. Michael Shull

Among the many different pieces of physics that go into simulations of the circumgalactic medium (CGM), the metagalactic ultraviolet background (UVB) plays a significant role in determining the ionization state of different metal species.…

Observations of the circumgalactic medium (CGM) often display coincident absorption from species with widely varying ionization states, providing direct evidence for complex, multiphase interactions. Motivated by these measurements, we…

Astrophysics of Galaxies · Physics 2025-05-23 Lisiyuan Yang , Neal Katz , Evan Scannapieco , Marcus Brüggen

The production and distribution of metals in the diffuse intergalactic medium (IGM) have implications for galaxy formation models and the baryon (re)cycling process. The relative abundance of metals in high versus low-ionization states has…

Astrophysics of Galaxies · Physics 2022-08-17 Suk Sien Tie , Joseph F. Hennawi , Koki Kakiichi , Sarah E. I. Bosman

Galaxies evolve through a dynamic exchange of material with their immediate surrounding environment, the so-called circumgalactic medium (CGM). Understanding the physics of gas flows and the nature of the CGM is thus fundamental to studying…

Astrophysics of Galaxies · Physics 2024-10-16 C. Di Cesare , M. Ginolfi , L. Graziani , R. Schneider , M. Romano , G. Popping

Stellar and AGN-driven feedback processes affect the distribution of gas on a wide range of scales, from within galaxies well into the intergalactic medium. Yet, it remains unclear how feedback, through its connection to key galaxy…

Astrophysics of Galaxies · Physics 2025-12-15 Daniele Sorini , Sownak Bose , Mathilda Denison , Romeel Davé

We explore the application of computer vision and machine learning (ML) techniques to predict material properties (e.g. compressive strength) based on SEM images. We show that it's possible to train ML models to predict materials…

Understanding how galaxies interact with the circumgalactic medium (CGM) requires determining how galaxies morphological and stellar properties correlate with their CGM properties. We report an analysis of 66 well-imaged galaxies detected…

Over the past decade, Lyman-alpha and metal line absorption observations have established the ubiquity of a gas-rich circumgalactic medium (CGM) around star-forming galaxies at z~0.2 potentially tracing half of the missing baryonic mass…

Astrophysics of Galaxies · Physics 2019-03-19 D. J. Pisano , A. Fox , D. French , J. C. Howk , N. Lehner , F. J. Lockman , K. Jones

Ionization balance in the intergalactic medium (IGM) is central to the interpretation of quasar absorption spectra, linking observed ionic columns to the underlying gas density, temperature, metallicity, and ionizing radiation field.…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-17 Bhaskar Arya , Kartick C. Sarkar , Shiv K. Sethi

The distribution and the abundance of metals in the intergalactic medium (IGM) have strong implications on galaxy formation and evolution models. The ionic transitions of heavy elements in quasar spectra can probe both the mechanisms and…

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