Spectral observations of big objects
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Peculiar galaxy
The most typical characteristics of E+A galaxies are that their spectra show strong Balmer absorption lines but no significant emission lines associated with ongoing star formation.The spectra can be roughly fitted by a combination of an old elliptical galaxy(E) and a young A-type star spectrum,so named E+A galaxies.The existence of strong Balmer absorption lines indicates that E+A galaxies have undergone starburst activities,and the shortage of emission lines implies that they have quenched their star formation recently. Therefore,E+A galaxies are also interpreted as post-starburst galaxies. On the evolutionary path of some galaxies from gas-rich,star-forming,disk-dominated blue ones into gas-poor,quiescent,bulge-dominated red ones,E+A galaxies,which are in the intermediate phase,play an important role in our understanding of galaxy formation and evolution.E+A galaxies originate mainly from merging/interaction in low density regions, especially wet merging between gas-rich galaxies,but a few cluster-related physical mechanisms also play some role,such as ram pressure stripping star-forming gas by hightemperature and high-density intracluster media.Many physical parameters of E+A galaxies are between typical early-type and late type galaxies,or close to early-type,which suggest they will eventually evolve into elliptical galaxies.Although poor groups and field environment are preferred by E+A galaxies to reside in,a fraction of them located in rich groups and clusters whose members are almost early-type galaxies.Feedback from AGNs may be responsible for quenching star formation on the path of forming E+A galaxies.Spectral features of LINER/Seyferts and observational evidences for feedback from AGNs are indeed found in many E+A galaxies recently.However,this mechanism does not work in less massive galaxies. This paper presents the basic observational characteristics of E+A galaxies,and reviews their formation mechanism,evolutionary destination,environment and the connections with AGNs.Some problems are reviewed,.ie.the method for picking out homogeneous E+A galaxies,the connections between E+A and other transition galaxies,the detailed histories of star formation at the very starburst and post-starburst stages.
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Peculiar galaxy
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We prepare a catalog of the morphological types of 5840 galaxies within z = 0.01. We determine the morphological types by visual inspection using color images from the Sloan Digital Sky Survey (SDSS) DR7. The majority of the sample galaxies are SDSS spectroscopic target galaxies, but we add ~ 900 galaxies whose redshifts are available in the NASA Extra Galactic Database (NED). The fraction of elliptical and lenticular galaxies is ~ 0.06 while spiral galaxies comprise ~ 30% of the sample with a bar fraction of ~ 0.6. About half of sample are dwarf galaxies of which ~ 35% are dwarf elliptical-like galaxies. There is a strong correlation between the morphological types and luminosities of the galaxies, i.e., high luminosities in the early type galaxies and low luminosity in the late type galaxies. The mean luminosity of dwarf elliptical-like galaxies is similar to that of irregular galaxies.
Peculiar galaxy
Dwarf spheroidal galaxy
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We use the Karachentseva (1973) ``Catalogue of Very Isolated Galaxies'' to investigate a candidate list of >100 very isolated early-type galaxies. Broad-band imaging and low resolution spectroscopy are available for a large fraction of these candidates and result in a sample of 102 very isolated early-type galaxies, including 65 ellipticals and 37 S0 galaxies. Many of these systems are quite luminous and the resulting optical luminosity functions of the Es and early-types (E+S0s) show no statistical differences when compared to luminosity functions dominated by group and cluster galaxies. However, whereas S0s outnumber Es 4:1 in the CfA survey, isolated Es outnumber S0s by nearly 2:1. We conclude that very isolated elliptical galaxies show no evidence for a different formation and/or evolution process compared to Es formed in groups or clusters, but that most S0s are formed by a mechanism (e.g., gas stripping) that occurs only in groups and rich clusters. Our luminosity function results for ellipticals are consistent with very isolated ellipticals being formed by merger events, in which no companions remain. CHANDRA observations were proposed to test specifically the merger hypothesis for isolated ellipticals. However, this program has resulted in the observation of only one isolated early-type galaxy, the S0 KIG 284, which was not detected at a limit well below that expected for a remnant group of galaxies. Therefore, the hypothesis remains untested that very isolated elliptical galaxies are the remains of a compact group of galaxies which completely merged.
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Invited Papers: Galaxy Types.- Morphology of Galaxies: An Overview.- The Luminosity Functions of Galaxies.- Elliptical Galaxies.- Structure and Kinematics of Spirals.- Brightest Cluster Members.- Central Regions of Early-Type Galaxies.- Stellar Content and Chemical Evolution in Spheroidal Populations.- Invited Papers: Galaxian Components.- Stellar Disks in Early-Type Galaxies.- Gaseous Disks in Elliptical Galaxies.- Formation and Maintenance of Spiral Structure.- Dark Matter in Elliptical Galaxies.- Dark Matter in Late-Type Galaxies.- Dark Matter in Dwarf Galaxies.- Elliptical Galaxies in X-Rays.- The Warm Component of the ISM of Elliptical Galaxies.- The Bar Component in Disk Galaxies.- Peculiar Kinematics.- Cold Gas in Elliptical Galaxies.- Cold Gas in Late-Type Galaxies.- Abundance Gradients and Related Properties in Galaxies.- Structure and Metallicity of Low-Luminosity Early-Type Galaxies.- Invited Papers: Environment and Systematics.- Interactions: Weak.- Interactions: Strong.- The Morphology of Binary Galaxies.- Intrinsic Shapes of Elliptical Galaxies.- On Understanding the Global Properties of Galaxies.- Galaxy Manifolds and Galaxy Formation.- Sub-Components in Elliptical Galaxies and their Formation.- Morphology and Classification of Galaxies - Where Do We Stand?.- Poster Papers.- Detailed Morphological Classification of Early-Type Galaxies in the Perseus Cluster.- Properties of Dwarf Spheroidals.- Bright Cores in Nearby Southern Galaxies.- Shell Formation and Thick Disks in Elliptical Galaxies.- The Origin of Strong Isophotal Twists in Elliptical Galaxies.- Photometric Properties of Disks in Elliptical Galaxies.- Elliptical Galaxies with Dark Matter.- Nuclear Dust-Discs in Radio Ellipticals.- Extended H? Filaments in Elliptical Galaxies.- The Origin of the Ionized Gas in S0 Galaxies.- Line-Strength Gradients in S0 Galaxies.- Ultraviolet Spectra of Early Type Galaxies.- On the Nature of the Compact Galaxies in the UGC.- Morphology of Galaxies Surrounding Compact Groups.- Mean Surface Density and Morphological Type in Disc-Galaxies.- Peculiar Kinematics in Interacting Elliptical Galaxies.- Morphology and Kinematics of Spiral Galaxies without Bar: The Importance of the Central Mass.- The Correlation between Velocity Gradients and Arm Classification in Spiral Galaxies.- Optical Line/Radio Luminosity Correlation and the Effects of the Interstellar Medium.- The Luminosity-Diameter Relation for Disk Galaxies: A Search for Environmental Effects.- Global Properties in Early Type Galaxies.- Masses and Mass-to-Light Ratios of Elliptical Galaxies.- On the Photometric Scaling Laws for Early-Type Galaxies.- Properties of Brightest Cluster Members.- The Fundamental Plane for Early-Type Galaxies.- Elliptical Galaxies and the Thickness of the Fundamental Plane.- Dissipationless Formation of Elliptical Galaxies.- The Two-Component Colour-Structure of the gE Galaxy NGC 4472.- The Velocity Dispersion Anisotropy in NGC 720.- NGC 205 and the Nature of Compact Nuclei in Dwarf Galaxies.- Light and Color Distribution in the Core of M32.- NGC 3384 and Its Saturn-Like Appearance.- Cigale Observations of NGC 3198.- Mapping the Star Formation in Nearby Galaxies: The Magellanic Irregular NGC 3109.- MM Observations of the Magellanic Clouds from Antarctica.- Seyfert Galaxies with Close Companions. A Method for Identification.- Globular Clusters as Probes of the Galactic Potential.- Relation between the Properties of Globular Cluster System and the Mass Distribution on the Galactic Disk.- Towards a Precise Definition of the Morphological Structures of Galaxies as a Basis for Their Automatic Classification.- Fourier Analysis of Barred Galaxies: A Convenient Alternative to the Component Decomposition.- Improvements of the Signal-to-Noise Ratio by Adaptive Filtering.- Index of Objects.
Peculiar galaxy
Dwarf spheroidal galaxy
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The data collected in the Shapley–Ames catalog of bright galaxies show that lenticular (S0) galaxies are typically about a magnitude fainter than both elliptical (E) and early spiral (Sa) galaxies. Hubble was therefore wrong to regard S0 galaxies as being intermediate between morphological types E and Sa. The observation that E5–E7 galaxies are significantly fainter than objects of subtypes E0–E5 suggests that many of the flattest "ellipticals" may actually be misclassified lenticular galaxies. In particular, it is tentatively suggested all E7 galaxies might actually be misclassified S01(7) galaxies. The present results are consistent with the view that galaxies belonging to the S0 class evolved in environments in which they typically lost more than half of their original luminous material.
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A database containing 618 active and star-forming (A/SF) galaxies and 564 normal galaxies in a 120° × 6° wide strip crossing the north Galactic pole was constructed in order to compare the global properties of "active" galaxies against a control sample of "normal" galaxies. This database combines a literature and catalog search with new optical measurements from the Fpg (red) and Jpg (blue) band images of the STScI Digitized Sky Survey (DSS). We provide alternative names, accurate coordinates, morphological type, activity classes, red and blue apparent magnitudes, 2MASS near-infrared J–H and H–K colors, apparent diameters, axial ratios, position angles, and number counts of neighboring objects in a circle of radius 50 kpc. We also present an atlas of 103 interacting and merging systems among these galaxies. The integrated properties of A/SF and normal galaxies in this sample are compared using a multivariate factor analysis, which reveals that A/SF galaxies are objects with relatively late morphological types, and are more inclined and have bluer optical colors than normal galaxies. In this sample, all merging and interacting galaxies are A/SF objects. Star-forming galaxies are objects with relatively late morphological types, lower absolute luminosities and linear sizes, bluer colors, and higher inclination than sample X-ray or radio sources, as well as Seyfert galaxies. The near-infrared colors of the sample galaxies are independent parameters and do not correlate with activity level or any other parameter of the galaxies.
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Comparison of the morphological types of Markaryan galaxies and other galaxies in the Uppsala catalog indicates a strong deficiency of normal ellipticals among the Markaryan galaxies, for which the fraction of type E galaxies is less than or equal to 1% against 10% among the remaining galaxies. Among the Markaryan galaxies, an excess of barred galaxies is observed - among the Markaryan galaxies with types Sa-Scd, approximately half or more have bars, whereas among the remaining galaxies of the same types bars are found in about 1/3.
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H II galaxies are dwarf star forming galaxies found in objective prism surveys through their strong emission lines. They have been targets of extensive studies of their spectroscopic properties such as chemical abundances, physical conditions and kinematics. Little surface photometry work has been done on H II galaxies up to now. This thesis is primarily a CCD surface photometry study of the structural properties, optical colors and a statistical analysis of the environment of H II galaxies. In the chapter "The Morphology of H II Galaxies" I have used a sample of 39 H II galaxies with CCD images for a study of their overall morphology and luminosity profiles. The results show that H II galaxies can be classified in two main types: type I H II galaxies are luminous and have disturbed and irregular outer shapes while type II H II galaxies are less luminous and have regular shapes. The outer parts of profiles of all HIi galaxies are well represented by an exponential as in other types of known dwarf galaxies. In "The Dynamics of H II Galaxies" I have investigated the relation between the linear size of the starburst, luminosity and velocity dispersion. It is found that H II galaxies have similar relations as virialized systems which supports the gravitational origin of their overall kinematics. The possible bi-parametric behavior ("fundamental plane") of H II galaxies is also investigated. However, a conclusive answer to this question still requires more and better data. In "The Colors of H II Galaxies" I have presented a high spatial resolution CCD surface photometry study. The colors of the underlying stellar continuum within the starburst are obtained by removing the flux contribution of the emission lines in the broad band filters. Comparison with recent evolutionary population synthesis models show that the observational errors and the uncertainties in the models are still too large to put strict constraints on their past star formation history. However, the distribution of colors of the underlying galaxy in H II galaxies is similar to the colors of some dwarf galaxies which suggests a kinship of these with the quiescent phases of H II galaxies. In "The Environment of H II Galaxies" I have studied the environment of 51 H II galaxies for which I have CCD images, H-beta luminosity, velocity dispersion, H-beta equivalent width and oxygen abundance. The aim of the study is to check the tidal origin of the starburst in H II galaxies and the effect of the environment on their intrinsic properties. It is found that only 12 H II galaxies have a bright neighbour within a projected distance of 1 Mpc and 250 km s-1 in velocity difference. Surprisingly, isolated H II galaxies tend to be of high luminosity and disturbed morphology while H II galaxies with neighbours tend to be low luminosity regular H II galaxies. Furthermore, the metal abundance and the equivalent width of the emission lines in H II galaxies do not depend on the presence of a companion. These results are opposed to what is expected if interaction with a luminous companion is the main mechanism triggering the starbursts. It is also found a loose group of four H II galaxies with no luminous companion. For this, there is the additional difficulty of understanding how these starbursts are synchronized on time scales of less than 107 yrs in systems separated by ~1-2 Mpc.
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Surface brightness fluctuation
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We have derived the X-ray luminosities of a sample of galaxies in groups, making careful allowance for contaminating intragroup emission. The LX:LB and LX:LFIR relations of spiral galaxies in groups appear to be indistinguishable from those in other environments, however the elliptical galaxies fall into two distinct classes. The first class is central-dominant group galaxies, which are very X-ray luminous and may be the focus of group cooling flows. All other early-type galaxies in groups belong to the second class, which populates an almost constant band of LX/LB over the range 9.8< log LB<11.3. The X-ray emission from these galaxies can be explained by a superposition of discrete galactic X-ray sources together with a contribution from hot gas lost by stars, which varies a great deal from galaxy to galaxy. In the region where the optical luminosity of the non-central group galaxies overlaps with the dominant galaxies, the dominant galaxies are over an order of magnitude more luminous in X-rays. We also compared these group galaxies with a sample of isolated early-type galaxies, and used previously published work to derive LX:LB relations as a function of environment. The non-dominant group galaxies have mean LX/LB ratios very similar to those of isolated galaxies, and we see no significant correlation between LX/LB and environment. We suggest that previous findings of a steep LX:LB relation for early-type galaxies result largely from the inclusion of group-dominant galaxies in samples.
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