Ivan Yu. Katkov

Decoupled gas kinematics in isolated S0 galaxies

ABSTRACT A sample of completely isolated S0 galaxies has been studied by means of long-slit spec-troscopy at the Russian 6-m telescope. 7 of 12 galaxies have revealed a presence of ex-tended ionized-gas discs which rotation is mostly decoupled from the stellar kinematics: 5of 7 (71±17%) galaxies show a visible counterrotation of the ionized-gas component withrespect to the stellar component. The emission-line diagnostics demonstrates a wide range ofthe gas excitation mechanisms, although a pure excitation by young stars is rare. We concludethat in all cases the extended gaseous discs in our sample S0s are of external origin, despitethe visible isolation of the galaxies. Possible sources of external accretion, such as systems ofdwarf gas-rich satellites or cosmological cold-gas filaments, are discussed.Key words: galaxies: elliptical and lenticular — galaxies: ISM — galax ies: kinematics anddynamics — galaxies: evolution — galaxies. 1 INTRODUCTIONOne of the central topics in current extragalactic astronomy is howgalaxies form and how their properties change through cosmictimes. This is a particularly difficult task if concerning le nticulargalaxies since this class of objects show a diversity in their prop-erties that goes beyond present day simulations. A lot of internaland external physical processes controlling evolution of galaxiesthrough cosmic time may, and must, play role. External processes– gravitational tides, major and minor mergers, dry and wet ones,external cold gas accretion through intergalactic medium, ram pres-sure in hot intracluster/intragroup medium – govern star formationand re-shape general structures. Internal disc instabilities may pro-voke secular evolution and matter radial re-distribution.The mainpoint is to study galaxies where manifold of processes is con-strained and so evolution is only driven by few main processes.Such are isolated galaxies.We have compiled our sample of isolated S0 galaxies basingon the approaches recently developed by the team of Karachent-sev, Makarov, and co-authors. Their group-finding algorithmthat takes into account individual characteristics of galaxies hasbeen already used to study the properties of isolated galax-ies (Karachentsev et al. 2011), binary (Karachentsev & Makarov2008), triple (Makarov & Karachentsev 2009) systems of galaxies,and galaxy groups (Makarov & Karachentsev 2011). Our sampleobjects, 18 S0 galaxies which are rather nearby, V

Kinematics and Stellar Populations in Isolated Lenticular Galaxies

By combining new long-slit spectral data obtained with the Southern African Large Telescope (SALT) for 9 galaxies with previously published our observations for additional 12 galaxies we study the stellar and gaseous kinematics as well as radially resolved stellar population properties and ionized gas metallicity and excitation for a sample of isolated lenticular galaxies. We have found that there is no particular time frame of formation for the isolated lenticular galaxies: the mean stellar ages of the bulges and disks are distributed between 1 and > 13 Gyr, and the bulge and the disk in every galaxy formed synchronously demonstrating similar stellar ages and magnesium-to-iron ratios. Extended ionized-gas disks are found in the majority of the isolated lenticular galaxies, in 72%

A complex stellar line-of-sight velocity distribution in the lenticular galaxy NGC 524

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Stellar counter-rotation in lenticular galaxy NGC 448

11%. The half of all extended gaseous disks demonstrate visible counterrotation with respect to their stellar counterparts. We argue that just such fraction of projected counterrotation is expected if all the gas in isolated lenticular galaxies is accreted from outside, under the assumption of isotropically distributed external sources. A very narrow range of the gas oxygen abundances found by us for the outer ionized gas disks excited by young stars, [O/H] from 0.0 to +0.2 dex, gives evidence for the satellite merging as the most probable source of this accretion. At last we formulate a hypothesis that morphological type of a field disk galaxy is completely determined by the outer cold-gas accretion regime.

The Diversity of Thick Galactic Discs

Abstract We present a detailed study of the stellar and gaseous kinematics in the luminous early-type galaxy NGC 524, derived from the long-slit spectroscopic observations obtained with the Russian 6 m telescope and the IFU data from the SAURON survey. The stellar line-of-sight velocity distribution (LOSVD) of NGC 524 exhibits strong asymmetry. We performed a comprehensive analysis of the LOSVD using two complementary approaches by the nbursts full spectral fitting technique: (a) a non-parametric LOSVD recovery and (b) a parametric recovery of two Gaussian kinematical components having different stellar populations. We discuss the origin of the complex stellar LOSVD of NGC 524.

Outer regions of the merging system Arp 270

The counter-rotation phenomenon in disc galaxies directly indicates a complex galaxy assembly history which is crucial for our understanding of galaxy physics. Here we present the complex data analysis for a lenticular galaxy NGC 448, which has been recently suspected to host a counter-rotating stellar component. We collected deep long-slit spectroscopic observations using the Russian 6-m telescope and performed the photometric decomposition of Sloan Digital Sky Survey (SDSS) archival images. We exploited (i) a non-parametric approach in order to recover stellar line-of-sight velocity distributions and (ii) a parametric spectral decomposition technique in order to disentangle stellar population properties of both main and counter-rotating stellar discs. Our spectral decomposition stays in perfect agreement with the photometric analysis. The counter-rotating component contributes

A new technique for the determination of the initial mass function in unresolved stellar populations

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The insight into the dark side. I. The pitfalls of the dark halo parameters estimation

30 per cent to the total galaxy light. We estimated its stellar mass to be

A new method for reconstructing the density distribution of matter in the disks of spiral galaxies from the rotation velocity curve in it

9.0^{+2.7}_{-1.8}\cdot10^{9}M_\odot

Gas Motion Mapping for Three Seyfert Galaxies

. The radial scale length of counter-rotating disc is