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Distinguishing active galaxies from star-forming galaxies is essential for understanding galaxy evolution. Diagnostic methods like the BPT (Baldwin, Phillips, and Terlevich) diagram use optical emission-line ratios to separate galaxies.…

Astrophysics of Galaxies · Physics 2026-03-26 Farideh Mazoochi , Reihaneh Karimi , Mohammad Hossein Zhoolideh Haghighi , Fatemeh Tabatabaei

It is difficult to accurately identify galaxy mergers and it is an even larger challenge to classify them by their mass ratio or merger stage. In previous work we used a suite of simulated mergers to create a classification technique that…

Astrophysics of Galaxies · Physics 2023-04-12 R. Nevin , L. Blecha , J. Comerford , J. Simon , B. A. Terrazas , R. S. Barrows , J. A. Vázquez-Mata

Galaxies of rare morphology are of paramount scientific interest, as they carry important information about the past, present, and future universe. Once a rare galaxy is identified, studying it more effectively requires a set of galaxies of…

Instrumentation and Methods for Astrophysics · Physics 2017-01-04 Lior Shamir

Autonomous digital sky surveys such as Pan-STARRS have the ability to image a very large number of galactic and extra-galactic objects, and the large and complex nature of the image data reinforces the use of automation. Here we describe…

Astrophysics of Galaxies · Physics 2020-12-16 Hunter Goddard , Lior Shamir

We present the largest, most homogeneous catalogue of merging galaxies in the nearby universe obtained through the Galaxy Zoo project - an interface on the world-wide web enabling large-scale morphological classification of galaxies through…

Non-parametric morphology statistics have been used for decades to classify galaxies into morphological types and identify mergers in an automated way. In this work, we assess how reliably we can identify galaxy post-mergers with…

Classifying galaxies is an essential step for studying their structures and dynamics. Using GalaxyZoo2 (GZ2) fractions thresholds, we collect 545 and 11,735 samples in non-galaxy and galaxy classes, respectively. We compute the Zernike…

Instrumentation and Methods for Astrophysics · Physics 2025-01-20 Hamed Ghaderi , Nasibe Alipour , Hossein Safari

We introduce a new effective strategy to assign group and cluster membership probabilities $P_{mem}$ to galaxies using photometric redshift information. Large dynamical ranges both in halo mass and cosmic time are considered. The method…

Cosmology and Nongalactic Astrophysics · Physics 2016-11-09 Gianluca Castignani , Christophe Benoist

We present a new tool for the photometric estimate of stellar masses in distant galaxies. The observed SEDs are fitted by combining single stellar populations, with different SFRs and amounts of dust extinction. This approach gives us the…

Using the galaxy data of the Sloan Digital Sky Survey Data Release 8 (SDSS DR8), I explore whether the concentration index is a good morphological classification tool and find that a reasonably pure late-type galaxy sample can be…

Astrophysics of Galaxies · Physics 2015-06-12 Xin-Fa Deng

We analyze the Near Infrared ($\sim0.8-1\mu$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $0<z<6$, compare with previous HST-based results and release the first JWST-based morphological catalog of…

Encoded within the morphological structure of galaxies are clues related to their formation and evolutionary history. Recent advances pertaining to the statistics of galaxy morphology include sophisticated measures of concentration (C),…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 K. M. Hambleton , B. K. Gibson , C. B. Brook , G. S. Stinson , C. J. Conselice , J. Bailin , H. Couchman , J. Wadsley

Automating classification of galaxy components is important for understanding the formation and evolution of galaxies. Traditionally, only the larger galaxy structures such as the spiral arms, bulge, and disc are classified. Here we use…

Astrophysics of Galaxies · Physics 2022-05-10 Robin J. Kwik , Jinfei Wang , Pauline Barmby , Benne W. Holwerda

We interpret published CCD UBVI data to deduce the stellar density distribution and metallicity distribution function in the region from 2-8 kpc from the Galactic Plane, and compare our results to several star count models. A feature of…

Astrophysics · Physics 2009-11-07 S. Karaali , S. G. Ak , S. Bilir , Y. Karatas , G. Gilmore

Aims. This work investigates the potential of using the wavelength-dependence of galaxy structural parameters (S\'ersic index, n, and effective radius, Re) to separate galaxies into distinct types. Methods. A sample of nearby galaxies with…

Astrophysics of Galaxies · Physics 2015-05-13 M. Vika , B. Vulcani , S. P. Bamford , B. Häußler , A. L. Rojas

The task of morphological classification is complex for simple parameterization, but important for research in the galaxy evolution field. Future galaxy surveys (e.g. EUCLID) will collect data about more than a $10^9$ galaxies. To obtain…

Computer Vision and Pattern Recognition · Computer Science 2021-05-10 Andrey Soroka , Alex Meshcheryakov , Sergey Gerasimov

Using the TNG50 cosmological simulation and observations from the Kilo-Degree Survey (KiDS), we investigate the connection between galaxy mergers and optical morphology in the local Universe over a wide range of galaxy stellar masses…

We develop a straightforward and quantitative two-step method for spectroscopically classifying galaxies from the low signal-to-noise (S/N) optical spectra typical of galaxy redshift surveys. First, using \chi^2-fitting of characteristic…

Astrophysics · Physics 2009-10-28 Dennis Zaritsky , Ann I. Zabludoff , Jeffrey A. Willick

Here, we present a machine vision approach, combining a VAE framework with PCA, to decipher galaxy images. Using mock gri-band images from the EAGLE simulation, the VAE finds that around 35 features are needed to describe the images. Adding…

Astrophysics of Galaxies · Physics 2025-11-27 Samuel Howie , Ting-Yun Cheng , Carlton M. Baugh

State-of-the-art cosmological hydrodynamical simulations have star particles with typical mass between $\sim 10^8$ and $\sim 10^3$ M$_{\odot}$ according to resolution, and treat them as simple stellar populations. On the other hand,…

Astrophysics of Galaxies · Physics 2018-07-31 Milena Valentini , Alessandro Bressan , Stefano Borgani , Giuseppe Murante , Léo Girardi , Luca Tornatore