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Galaxies, Volume 4, Issue 1 (March 2016) – 4 articles

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Article
Padé Approximant and Minimax Rational Approximation in Standard Cosmology
by Lorenzo Zaninetti
Galaxies 2016, 4(1), 4; https://doi.org/10.3390/galaxies4010004 - 18 Feb 2016
Cited by 11 | Viewed by 4262
Abstract
The luminosity distance in the standard cosmology as given by ΛCDM and, consequently, the distance modulus for supernovae can be defined by the Padé approximant. A comparison with a known analytical solution shows that the Padé approximant for the luminosity distance has an [...] Read more.
The luminosity distance in the standard cosmology as given by ΛCDM and, consequently, the distance modulus for supernovae can be defined by the Padé approximant. A comparison with a known analytical solution shows that the Padé approximant for the luminosity distance has an error of 4 % at redshift = 10 . A similar procedure for the Taylor expansion of the luminosity distance gives an error of 4 % at redshift = 0 . 7 ; this means that for the luminosity distance, the Padé approximation is superior to the Taylor series. The availability of an analytical expression for the distance modulus allows applying the Levenberg–Marquardt method to derive the fundamental parameters from the available compilations for supernovae. A new luminosity function for galaxies derived from the truncated gamma probability density function models the observed luminosity function for galaxies when the observed range in absolute magnitude is modeled by the Padé approximant. A comparison of ΛCDM with other cosmologies is done adopting a statistical point of view. Full article
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Editorial
Acknowledgement to Reviewers of Galaxies in 2015
by Galaxies Editorial Office
Galaxies 2016, 4(1), 3; https://doi.org/10.3390/galaxies4010003 - 22 Jan 2016
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Abstract
The editors of Galaxies would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article
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Article
Investigation of the Stellar Population of Several Polar Ring Galaxies
by Liliya Shalyapina, Gulnara Karataeva, Olga Merkulova, Valeriya Yakovleva and Nina Yablokova
Galaxies 2016, 4(1), 2; https://doi.org/10.3390/galaxies4010002 - 05 Jan 2016
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Abstract
We present results of our investigation of two multi-spin galaxies which were taken from the catalog of polar ring galaxies. All of them possess nucleus-like knots. An analysis of gas and stars kinematics and study of the stellar population were carried out for [...] Read more.
We present results of our investigation of two multi-spin galaxies which were taken from the catalog of polar ring galaxies. All of them possess nucleus-like knots. An analysis of gas and stars kinematics and study of the stellar population were carried out for these objects. A complex structure and peculiar kinematics of both components were revealed. The observed distribution of the stellar age and metallicity in central parts of galaxies (radius is about 8″) and along directions through their knots helps us to understand the merging processes and make conclusion of the knots’ nature in these objects. Full article
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816 KiB  
Article
Hidden Imprints of Minor Merging in Early-Type Galaxies: Inner Polar Rings and Inclined Large-Scale Gaseous Disks In S0s
by Olga Sil’chenko
Galaxies 2016, 4(1), 1; https://doi.org/10.3390/galaxies4010001 - 24 Dec 2015
Cited by 2 | Viewed by 3889
Abstract
I discuss my latest observational data and ideas about decoupled gaseous subsystems in nearby lenticular galaxies. As an extreme case of inclined gaseous disks, I demonstrate a sample of inner polar disks, derive their incidence, about 10% among the volume-limited nearby S0 galaxies, [...] Read more.
I discuss my latest observational data and ideas about decoupled gaseous subsystems in nearby lenticular galaxies. As an extreme case of inclined gaseous disks, I demonstrate a sample of inner polar disks, derive their incidence, about 10% among the volume-limited nearby S0 galaxies, and discuss their origin. However, large-scale decoupled gaseous disks at intermediate inclinations are also a rather common phenomenon among the field S0 galaxies. I suggest that the geometry of outer gas accretion and the final morphology of the galaxy may be tightly related: inclined gas infall may prevent star formation in the accreted disk and force the disk galaxy to be a lenticular. Full article
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