Testing the nature of S0 galaxies using planetary nebula kinematics in NGC 1023

We investigate the manner in which lenticular galaxies are formed by studying their stellar kinematics: an S0 formed from a fading spiral galaxy should display similar cold outer disc kinematics to its progenitor, while an S0 formed in a minor merger should be more dominated by random motions. In a pilot study, an attempt to distinguish between these scenarios, we have measured the planetary nebula (PN) kinematics of the nearby S0 system NGC 1023. Using the Planetary Nebula Spectrograph, we have detected and measured the line-of-sight velocities of 204 candidate planetary nebulae (PNe) in the field of this galaxy. Out to intermediate radii, the system displays the kinematics of a normal rotationally supported disc system. After correction of its rotational velocities for asymmetric drift, the galaxy lies just below the spiral galaxy Tully–Fisher relation, as one would expect for a fading system. However, at larger radii the kinematics undergo a gradual but major transition to random motion with little rotation. This transition does not seem to reflect a change in the viewing geometry or the presence of a distinct halo component, since the number counts of PNe follow the same simple exponential decline as the stellar continuum with the same projected disc ellipticity out to large radii. The galaxy's small companion, NGC 1023A, does not seem to be large enough to have caused the observed modification either. This combination of properties would seem to indicate a complex evolutionary history in either the transition to form an S0 or in the past life of the spiral galaxy from which the S0 formed. More data sets of this type from both spirals and S0s are needed in order to definitively determine the relationship between these types of system.     

S0 galaxies in Fornax: data and kinematics

We have obtained long-slit spectroscopy for a sample of nine S0 galaxies in the Fornax Cluster using the FORS2 spectrograph at the 8.2-m European Southern Observatory (ESO) Very Large Telescope (VLT). From these data, we have extracted the kinematic parameters, comprising the mean velocity, velocity dispersion and higher moment h ₃ and h ₄ coefficients, as a function of position along the major axes of these galaxies. Comparison with published kinematics indicates that earlier data are often limited by their lower signal-to-noise ratio and relatively poor spectral resolution. The greater depth and higher dispersion of the new data mean that we reach well beyond the bulges of these systems, probing their disc kinematics in some detail for the first time. Qualitative inspection of the results for individual galaxies shows that they are not entirely simple systems, perhaps indicating a turbulent past. None the less, we are able to derive reliable circular velocities for most of these systems, which points the way towards a study of their Tully–Fisher relation. This study, along with an analysis of the stellar populations of these systems out to large galactocentric distances, will form the bases of future papers exploiting these new high-quality data, hopefully shedding new light on the evolutionary history of these systems.     

Bimodality in low-luminosity E and S0 galaxies

Stellar population characteristics are presented for a sample of low-luminosity early-type galaxies (LLEs) in order to compare them with their more luminous counterparts. Long-slit spectra of a sample of 10 LLEs were taken with the ESO New Technology Telescope, selected for their low luminosities. Line strengths were measured on the Lick standard system. Lick indices for these LLEs were correlated with velocity dispersion (σ), alongside published data for a variety of Hubble types. The LLEs were found to fall below an extrapolation of the correlation for luminous ellipticals and were consistent with the locations of spiral bulges in plots of line strengths versus σ. Luminosity weighted average ages, metallicities and abundance ratios were estimated from  χ²  fitting of 19 Lick indices to predictions from simple stellar population models. The LLEs appear younger than luminous ellipticals and of comparable ages to spiral bulges. These LLEs show a bimodal metallicity distribution, consisting of a low-metallicity group (possibly misclassified dwarf spheroidal galaxies) and a high-metallicity group (similar to spiral bulges). Finally, they have low α-element to iron peak abundance ratios indicative of slow, extended star formation.     

Clumpy metal concentrations in elliptical galaxies NGC 4374 and NGC 4636

We present a high spatial resolution study of metal distributions in the nearby,gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data.We define the hardness ratio HRFeL as the ratio of the emission in 0.65-1.4keV to that in 0.3-0.6keV and 1.4-3.5keV(after the magnesium and silicon lines are excluded),and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3-0.6keV,so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distribu...     

Lopsided galaxies: the case of NGC 891

It has been known for a long time that a large fraction of disc galaxies are lopsided. We simulate three different mechanisms that can induce lopsidedness: flyby interactions, gas accretion from cosmological filaments and ram pressure from the intergalactic medium. Comparing the morphologies, H  i spectrum, kinematics and   m = 1  Fourier components, we find that all of these mechanisms can induce lopsidedness in galaxies, although in different degrees and with observable consequences. The time-scale over which lopsidedness persists suggests that flybys can contribute to ∼20 per cent of lopsided galaxies. We focus our detailed comparison on the case of NGC 891, a lopsided, edge-on galaxy with a nearby companion (UGC 1807). We find that the main properties of NGC 891 (morphology, H  i spectrum, rotation curve, existence of a gaseous filament pointing towards UGC 1807) favour a flyby event for the origin of lopsidedness in this galaxy.     

Young circumnuclear disks in elliptical galaxies

By means of integral-field spectroscopy with the Multi-Pupil Field/Fiber Spectrograph of the Russian 6-m telescope we have studied the central parts of NGC 759 and NGC 83— regular (non-interacting, without strong nuclear activity) round red luminous (M _B =?20.8–?21.6) elliptical galaxies which are however known to possess molecular gas. In both galaxies we have found central stellar disks with the extension of 1–2 kpc along the radius which are evidently being formed just now.     

Stars and clusters of the coma galaxies NGC 4921 and NGC 4923

Based on deep Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for the spiral and lenticular galaxies NGC 4921 and NGC 4923 in the Coma cluster. The derived Hertzsprung-Russell diagrams show that, apart from the stellar population, NGC 4921 has several thousand globular clusters. The asymmetry of their apparent distribution proves that NGC 4921 is in close spatial proximity to NGC 4923. We have determined the positions of the peaks for the luminosity functions of globular clusters in the two galaxies, which has allowed us to measure the distance to this pair (D = 97±5 Mpc). In many cases, compact star-forming regions at the periphery of NGC 4921 are located at the ends of extended (up to 1.5 kpc) radial gas and dust filaments. The metallicity of young stars in these star-forming regions is close to that of the Sun (Z = 0.02).     

Extended Gaseous Disk in the S0 Galaxy NGC 4143

Astronomy Letters - We present the results of our spectroscopic study of the lenticular galaxy NGC 4143—a peripheral member of the Ursa Major cluster. Using the observations at the 6-m SAO...     

Observational study of the candidate polar-ring galaxies NGC 304 and NGC 7625

We present the results of our photometric (BV R) and spectroscopic CCD observations of NGC 304 and NGC 7625, candidate polar-ring galaxies, performed with the 6-m Special Astrophysical Observatory telescope. For NGC 304, such a study has been carried out for the first time. We have obtained basic integrated characteristics of the galaxies and determined their morphological types (S0 for NGC 304 and Sa for NGC 7625). The absolute magnitudes of the galaxies, M _B = ?20^m.81 for NGC 304 and M _B = ?19^m.34 for NGC7625, are indicative of their fairly high luminosities. The disk and bulge parameters have been determined forNGC 304 (µ₀ = 20^m.60, h = 3.86 kpc, µ _e = 21^m.59, r _e = 1.26 kpc in the B band); these correspond to the parameters of S0-type objects. The rotation velocity for NGC 304 (200 km s^?1) reaches its maximum at a galactocentric distance of 3.1 kpc, which yields a mass estimate for the galaxy of 2.8 × 10¹⁰ \(\mathcal{M}_ \odot \). The observed photometric features at the center of NGC 304 indicate that it may have an inner ring structure, although we have failed to confirm the existence of two kinematic systems based on our spectroscopic observations. In NGC 7625, the disk makes a dominant contribution to the total brightness. The derived integrated color indices (B-V = 0^m.81 and V-R = 0^m.61) agree with previous determinations of other authors. We have estimated the учештсешщт in the inner galactic regions. In the outer regions, we have detected structures with bluer colors (B-V = 0^m.60), which may be indicative of a polar ring with a minor stellar component.     

The optical variability of the Seyfert galaxies NGC 4051 and NGC 1068

The optical (BV) monitoring data for the Seyfert galaxies NGC 4051 and NGC 1068 are presented in this paper. NGC 4051 showed a variation of 0.43 mag in 21 minutes in B band from its bright nucleus, and the nucleus of NGC 1068 exhibited a variability of 0.46 mag in B band in a timescale of 1.8 hours. These results argued that the optical emission from the nuclei of the two Seyfert galaxies could be dominated by the nonthermal radiation. The data in this paper, however, are only marginal evidence on the rapid optical variability of these two Seyferts, and further monitoring is needed to confirm this type of variability.     

Detailed surface photometry of the cD galaxies NGC 4839 and NGC 4874

We present a detailed photometric study of the cD galaxies NGC 4839 and NGC 4874 based on the technique of surface photometry by fitting ellipses to the isophotes of the galaxies in the u, g, r, i, and z bands using Data Release 7 (DR7) of the Sloan Digital Sky Survey (SDSS). The motivation of this paper is to study the properties (e.g. break radius and surface brightness, color gradient, etc.) of the extended envelope of the two cD galaxies. The surface brightness profile in each band is obtained and fitted to the de Vaucouleurs r ^1/4 model. A deviation of the observed profile brighter than the fitted r ^1/4 model is noticed especially in the outer part of each galaxy. The profiles of ellipticity, position angle, B4 and shifts with respect to the center of each isophote are also obtained. The color index profiles, u-g, g-r, r-i, and i-z are also obtained and no significant color gradients are noticed except in the outer parts of the two galaxies. The integrated magnitude in each band and color indices are obtained and found to be in good agreement with the published ones.     

Synchronous evolution of galaxies in groups: NGC524 group

With the means of panoramic spectroscopy at the SAO RAS BTA telescope, we investigated the properties of stellar populations in the central regions of five early-type galaxies—the NGC524 group members. The evolution of the central regions of galaxies looks synchronized: the average age of stars in the bulges of all the five galaxies lies in the range of 3–6Gyr.Four of the five galaxies revealed synchronized bursts of star formation in the nuclei 1–2 Gyr ago. The only galaxy, in which the ages of stellar population in the nucleus and in the bulge coincide (i.e. the nuclear burst of star formation did not take place) isNGC502, the farthest from the center of the group of all the galaxies studied.     

GMOS spectroscopy of the S0 galaxy NGC 3115

We present Gemini Multi-Object Spectrograph longslit spectroscopy of the isolated S0 galaxy NGC 3115. We have determined kinematical data and Lick/IDS absorption line-strength indices for the major axis out to around 9 kpc and for the minor axis out to around 5 kpc (around 2R _e ). Using stellar population models which include the effects of variable [α/Fe] ratios, we derive metallicities, abundance ratios and ages for the stellar population of NGC 3115. We find that [α/Fe] remains fairly constant with increasing radius at around  [α/Fe]= 0.17  for the major axis but increases rapidly for the minor axis to around  [α/Fe]= 0.3  . We also find that to first order, this behaviour can be explained by a simple spheroid + disc model, where the spheroid has  [α/Fe]= 0.3  and the disc shows close to solar abundance ratios. The disc also appears considerably younger than the spheroid, having an age of around 6 Gyr compared to 12 Gyr for the spheroid. We compare these results to those previously presented for the globular cluster system of NGC 3115.     

Bar-driven evolution of S0s: the edge-on galaxy NGC 4570

We present circumstantial evidence that the central region of the edge-on S0 galaxy NGC 4570, which harbours a 150-pc scale nuclear disc in addition to its main outer disc, has been shaped under the influence of a small (∼ 500 pc) bar. This is based on the discovery of two edge-on rings, the locations of which are consistent with the inner Lindblad and ultraharmonic resonances of a rapidly tumbling triaxial potential. Observed features in the photometry and rotation curve correspond nicely with the positions of the main resonances, strengthening the case for a tumbling bar potential. The relative blue colour of the ILR ring, and the complete absence of any detected ISM, indicates that the nuclear ring is made of relatively young (≲ 2 Gyr) stars. We discuss a possible secular evolution scenario for this complex multicomponent galaxy, which may also apply to many other S0 galaxies with observed rings and/or multiple disc components.     

Central holes in disks of spiral galaxies

On the basis of the solutions obtained in the previous paper, the changes in the scenario of the standard model of the Big Bang are found. The chaos degree (constrainst on fluctuation spectra) is obtained, which could be still preserved by the initially completely chaotic Universe at the time of light elements nucleosynthesist _es. The time boundaries of hadron and lepton eras and the time the electron neutrinos and neutrons become frozen in reactions of weak interaction may be shifted up to 1.4 times. The corresponding temperatures may shift off from the standard ones 0.88 times if the mean-square level of fluctuations is close to unity. If the density of the energy of fluctuations concentrated in the short-wave region of the spectrum is less than 1.5 ^– , the nucleosynthesis leads to a helium abundance coinciding with the observe one. If at the timet _es the maximum of the spectral density of the energy is in the long-wave region, that is _max ct _es the level of the chaos during the period of nucleosynthesis is restricted to 1.76 (where |C _K |² d³ K,C _K is Fourier component of the amplitude of metric fluctuations). In particular, the protogalactic vortical disturbances with a wide spectrum 4 × 10^{3 -1}( = K/K, = /_crit) are compatible with the observed helium abundance.     

Massive disks in low surface brightness galaxies

An update of the set of low surface brightness galaxies is presented which can be used to set constraints on the otherwise ambiguous decompositions of their rotation curves into contributions due to the various components of the galaxies. The selected galaxies show all clear spiral structure and arguments of density wave theory of galactic spiral arms are used to estimate the masses of the galactic disks. Again these estimates seem to indicate that the disks of low surface brightness galaxies might be much more massive than currently thought. This puzzling result contradicts stellar population synthesis models. This would mean also that low surface brightness galaxies are not dominated by dark matter in their inner parts. This revised version was published online in August 2006 with corrections to the Cover Date.