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Galaxy groups are essential for studying the distribution of matter on a large scale in redshift surveys and for deciphering the link between galaxy traits and their associated halos. In this work, we propose a widely applicable method for…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-03 Juntao Ma , Jie Wang , Tianxiang Mao , Hongxiang Chen , Yuxi Meng , Xiaohu Yang , Qingyang Li

Determining the AGN content in structures of different mass/velocity dispersion and comparing them to higher mass/lower redshift analogs is important to understand how the AGN formation process is related to environmental properties. We use…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 L. Pentericci , M. Castellano , N. Menci , S. Salimbeni , T. Dahlen , A. Galametz , P. Santini , A. Grazian , A. Fontana

We use deep Chandra X-ray imaging to measure the distribution of specific black hole accretion rates ($L_X$ relative to the stellar mass of the galaxy) and thus trace AGN activity within star-forming and quiescent galaxies, as a function of…

High Energy Astrophysical Phenomena · Physics 2017-12-27 James Aird , Alison L. Coil , Antonis Georgakakis

Gamma-ray bursts (GRBs) are intense, short-lived bursts of gamma-ray radiation observed up to a high redshift ($z \sim 10$) due to their luminosities. Thus, they can serve as cosmological tools to probe the early Universe. However, we need…

Context. The main element of the observing program of the Spectrum-Roentgen-Gamma orbital observatory is a four-year all-sky survey, in the course of which the entire sky will be scanned eight times. Aims. We analyze the statistical…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-28 Alexander Kolodzig , Marat Gilfanov , Rashid Sunyaev , Sergey Sazonov , Marcella Brusa

We studied the Active Galactic Nuclei (AGN) radio emission from a compilation of hard X-ray selected samples, all observed in the 1.4 GHz band. A total of more than 1600 AGN with 2-10 keV de-absorbed luminosities higher than 10^42 erg/s…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 F. La Franca , G. Melini , F. Fiore

The X-ray luminosity function (XLF) of galaxies is dominated by AGN (classified by their optical spectra) above Lx=10**42 erg/s, below this value by normal galaxies. The X-ray flux of AGN at low X-ray luminosity therefore contains…

Astrophysics · Physics 2007-05-23 I. Lehmann , G. Hasinger , A. D. Schwope , Th. Boller

We apply a number of statistical and machine learning techniques to classify and rank gamma-ray sources from the Third Fermi Large Area Telescope (LAT) Source Catalog (3FGL), according to their likelihood of falling into the two major…

High Energy Astrophysical Phenomena · Physics 2016-03-23 P. M. Saz Parkinson , H. Xu , P. L. H. Yu , D. Salvetti , M. Marelli , A. D. Falcone

We use the Herschel-ATLAS science demonstration data to investigate the star-formation properties of radio-selected galaxies in the GAMA-9h field as a function of radio luminosity and redshift. Radio selection at the lowest radio…

We combine deep X-ray survey data from the Chandra observatory and the wide-area/shallow XMM-XXL field to estimate the AGN X-ray luminosity function in the redshift range z=3-5. The sample consists of nearly 340 sources with either…

Remnant radio galaxies represent the dying phase of radio-loud active galactic nuclei (AGN). Large samples of remnant radio galaxies are important for quantifying the radio galaxy life cycle. The remnants of radio-loud AGN can be identified…

We report accurate redshifts of 110 active galaxies (mostly radio-loud objects at z<0.4) observed in the course of a survey to find broad, double-peaked emission lines. These redshifts are measured from the narrow emission lines of these…

Astrophysics · Physics 2009-11-10 Michael Eracleous , Jules P. Halpern

High redshift AGN holds the key to understand the early structure formation and to probe the Universe during its infancy. We review the latest searches for high-z AGN in the deepest X-ray field so far, the Chandra Deep Field South (CDFS) 4…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Fabrizio Fiore , Simonetta Puccetti , Smita Mathur

SMBHs are theorised to undergo significant growth in the early Universe, however, the X-ray Luminosity Function (XLF), used as a principal tracer of the SMBH accretion density, lacks observational constraints at z>6, until now. We present…

High Energy Astrophysical Phenomena · Physics 2025-06-23 C. L. Barlow-Hall , J. Aird

We use machine learning techniques to investigate their performance in classifying active galactic nuclei (AGNs), including X-ray selected AGNs (XAGNs), infrared selected AGNs (IRAGNs), and radio selected AGNs (RAGNs). Using known physical…

Astrophysics of Galaxies · Physics 2021-10-26 Yu-Yen Chang , Bau-Ching Hsieh , Wei-Hao Wang , Yen-Ting Lin , Chen-Fatt Lim , Yoshiki Toba , Yuxing Zhong , Siou-Yu Chang

Abstract abridged. The eROSITA X-ray telescope aboard the SRG orbital observatory, in the course of its all-sky survey, is expected to detect about three million active galactic nuclei (AGN) and hundred thousand clusters and groups of…

High Energy Astrophysical Phenomena · Physics 2023-01-11 S. D. Bykov , M. R. Gilfanov , R. A. Sunyaev

We have used FMOS on Subaru to obtain near-infrared spectroscopy of 123 far-infrared selected galaxies in COSMOS and obtain the key rest-frame optical emission lines. This is the largest sample of infrared galaxies with near-infrared…

We introduce a new infrared diagnostic to separate galaxies on the basis of their dominant infrared emission: stellar or nuclear. The main novelty with respect to existing diagnostics, is the usage of a broad band encompassing at the same…

Astrophysics of Galaxies · Physics 2015-06-22 Dario Fadda , Giulia Rodighiero

Almost all massive galaxies today are understood to contain supermassive black holes (SMBH) at their centers. SMBHs grew by accreting material from their surroundings, emitting X-rays as they did so. X-ray Luminosity Functions (XLFs) of…

Astrophysics of Galaxies · Physics 2023-01-16 Ahlam Alqasim , Mat J. Page

In order to find a fast and reliable method for selecting metal poor galaxies (MPGs), especially in large surveys and huge database, an Artificial Neural Network (ANN) method is applied to a sample of star-forming galaxies from the Sloan…

Astrophysics of Galaxies · Physics 2015-06-18 F. Shi , Y-Y. Liu , X. Kong , Y. Chen
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