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A standard parametric maximum-likelihood technique is used to determine both the probability distribution over total HI mass $M_{\rm HI}$ and the regression of this quantity on the linear optical diameter $D_{\rm o}$ for field giant spirals…

Astrophysics · Physics 2009-10-28 José M. Solanes , Riccardo Giovanelli , Martha P. Haynes

Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity…

Astrophysics of Galaxies · Physics 2015-06-11 J. S. Heiner , J. R. Sánchez-Gallego , L. Rousseau-Nepton , J. H. Knapen

We present a machine learning search for local, low-mass galaxies ($z < 0.02$ and $10^6 M_\odot < M_* < 10^9 M_\odot$) using the combined photometric data from the DESI Imaging Legacy Surveys and the WISE survey. We introduce the spectrally…

Astrophysics of Galaxies · Physics 2025-03-19 Huanian Zhang , Guangping Ye , Rongyu Wu , Dennis Zaritsky

We describe a combined halo model to constrain the distribution of neutral hydrogen (HI) in the post-reionization universe. We combine constraints from the various probes of HI at different redshifts: the low-redshift 21-cm emission line…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-23 Hamsa Padmanabhan , Alexandre Refregier

Upcoming 21cm surveys will map the spatial distribution of cosmic neutral hydrogen (HI) over very large cosmological volumes. In order to maximize the scientific return of these surveys, accurate theoretical predictions are needed.…

Cosmology and Nongalactic Astrophysics · Physics 2021-07-29 Digvijay Wadekar , Francisco Villaescusa-Navarro , Shirley Ho , Laurence Perreault-Levasseur

Galaxies are theorized to form and co-evolve with their dark matter halos, such that their stellar masses and halo masses should be well-correlated. However, it is not known whether other observable galaxy features, such as their…

Cosmology and Nongalactic Astrophysics · Physics 2024-07-19 Austin J. Larson , John F. Wu , Craig Jones

The cross-correlation of optical galaxies with the neutral hydrogen (HI) radiation intensity can enhance the signal-to-noise ratio (SNR) of the HI intensity measurement. In this paper, we investigate the cross-correlation of the galaxy…

Cosmology and Nongalactic Astrophysics · Physics 2022-09-21 Furen Deng , Yan Gong , Yougang Wang , Shuting Dong , Ye Cao , Xuelei Chen

Strong gravitational lensing provides some of the deepest views of the Universe, enabling studies of high-redshift galaxies only possible with next-generation facilities without the lensing phenomenon. To date, 21 cm radio emission from…

Astrophysics of Galaxies · Physics 2015-08-06 R. P. Deane , D. Obreschkow , I. Heywood

The HI gas content is a key ingredient in galaxy evolution, the study of which has been limited to moderate cosmological distances for individual galaxies due to the weakness of the hyperfine HI 21-cm transition. Here we present a new…

Astrophysics of Galaxies · Physics 2021-12-08 Kasper E. Heintz , Darach Watson , Pascal Oesch , Desika Narayanan , Suzanne C. Madden

Context: We present the first Cosmological Parameter inferences from eROSITA X-ray observations of galaxy clusters using a Machine Learning algorithm. Methods: We train a Random Forest using mock catalogs of clusters from Magneticum…

This paper presents a comprehensive study of quasar photometric classification and redshift estimation using machine learning techniques. We cross-matched photometric data from the Dark Energy Survey Data Release 2 (DES DR2) with…

Instrumentation and Methods for Astrophysics · Physics 2026-05-19 Pablo Motta , Filipe B. Abdalla , Elcio Abdalla , Gabriel S. Costa , Camila Cardoso

In this study, we present a sophisticated hybrid machine-learning framework that significantly improves the accuracy of predicting hydrogen storage capacities in metal hydrides. This is a critical challenge due to the scarcity of…

Materials Science · Physics 2024-08-29 Satadeep Bhattacharjee , Pritam Das , Swetarekha Ram , Seung-Cheol Lee

We present a random forest framework for predicting circumgalactic medium (CGM) physical conditions from quasar absorption line observables, trained on a sample of Voigt profile-fit synthetic absorbers from the Simba cosmological…

Astrophysics of Galaxies · Physics 2023-07-25 Sarah Appleby , Romeel Davé , Daniele Sorini , Christopher Lovell , Kevin Lo

Here I briefly highlight our studies of the gas content, kinematics and star formation in nearby dwarf galaxies (D < 10 Mpc) based on the `Local Volume HI Survey' (LVHIS, Koribalski et al. 2018), which was conducted with the Australia…

Astrophysics of Galaxies · Physics 2020-02-19 B. S. Koribalski

Atomic hydrogen constitutes the gas reservoir from which molecular gas and star formation in galaxies emerges. However, the weakness of the line means it has been difficult to directly detect in all but the very local Universe. Here we…

In order to retrieve cosmological parameters from photometric surveys, we need to estimate the distribution of the photometric redshift in the sky with excellent accuracy. We use and apply three different machine learning methods to…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-13 Elcio Abdalla , Filipe B. Abdalla , Alessandro Marins , Amilcar Queiroz , Rafael M. Ribeiro , Alex S. C. Souza

We study the clustering properties of the recently compiled HIPASS neutral hydrogen (HI) sources catalogue using the two point correlation function in redshift space. If the two point correlation is modelled as a power law,…

Astrophysics · Physics 2007-05-23 S. Basilakos , K. Kovac , M. Aragon , R. van de Weygaert , J. M. van der Hulst

We examine the properties of atomic hydrogen (HI) associated with galaxies in the EAGLE simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at $z=0.1$, and we…

The observed high covering fractions of neutral hydrogen (HI) with column densities above $\sim 10^{17} \rm{cm}^{-2}$ around Lyman-Break Galaxies (LBGs) and bright quasars at redshifts z ~ 2-3 has been identified as a challenge for…

Cosmology and Nongalactic Astrophysics · Physics 2016-02-25 Alireza Rahmati , Joop Schaye , Richard G. Bower , Robert A. Crain , Michelle Furlong , Matthieu Schaller , Tom Theuns

We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC…

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